Biological product preservation apparatus and method

Abstract

Biological product preservation apparatus 1 comprising: container unit 100 for preserving biological product; thermal energy store 210; thermoelectric modulation device 225, wherein thermal energy sto

Description

Technical Field The present disclosure relates to the field of preservation of biological products. For example, the present disclosure may relate to the preservation of body tissue, such as body tissue through which a fluid may be circulated, e.g. with a gaseous oxygen persufflation mixture. Background In some cases, one or more organs may be obtained from a donor patient and such organ(s) may be used in the treatment of a recipient patient. In which case, a surgeon may remove a relevant organ from the patient. The organ is then transferred so that it can be used to treat the recipient patient. During this process, there will be a time period in which the organ is not connected to either patient, and this organ is to be maintained in a suitable state so that it may still be useful in the treatment of the recipient patient. In this time period the organ may have to be transported, such as from one hospital to another. Storage apparatuses have been disclosed which are designed to facilitate this transfer of an organ. For example, GB2592354 discloses apparatuses and methods for the storage and preservation of body tissue. Aspects of the present disclosure seek to provide systems and methods for preservation of biological products. Such systems and methods of the present disclosure may, in some implementations, be used to provide improved preservation of body tissue. Summary Aspects of the disclosure are set out in the independent claims and optional features are set out in the dependent claims. Aspects of the disclosure may be provided in conjunction with each other, and features of one aspect may be applied to other aspects. In an aspect, there is provided a biological product preservation apparatus comprising: a container unit for preserving a biological product; a thermal energy store; a thermoelectric modulation device, wherein the thermal energy store is thermally coupled to the container unit via the thermoelectric modulation device; and a controller configured to control operation of the thermoelectric modulation device to manage a temperature of a said biological product in the container unit. Embodiments may enable the provision of a preservation apparatus which provides tightly controlled thermal management of biological products in the container unit. This thermal management may be robust to substantially differing ambient conditions or temperatures. In turn, this may provide improved preservation of biological products. The controller may be configured to control operation of the thermoelectric modulation device based on at least one obtained indication of temperature. The obtained indication of temperature may be indicative of a temperature of the container unit (e.g. of the biological product in the container unit). The obtained indication of temperature may be obtained from a sensor located between the thermoelectric modulation device and the container unit. The sensor may be located in a base unit of the apparatus. The container unit may be received within a container unit receiving portion of the base unit. The controller may be able to infer, based on said indication of temperature, a temperature of the biological product in the container unit (e.g. using stored conversion data). The controller may be configured to control operation of the thermoelectric modulation device to retain a temperature of the apparatus within a selected temperature range. The temperature of the apparatus may be indicative of a temperature of the container unit. For example, the temperature may be a temperature at a point along a thermal transfer path between the thermoelectric modulation device and the container unit. The biological product may comprise any suitable product to be used in a medical scenario. For example, the biological product may comprise a product which is to be used to facilitate treatment of a patient. Such a product may be in the form of body tissue, e.g. artificial or real. For example, the body tissue may comprise an organ (e.g. a human or animal organ). Additionally, or alternatively, the biological product could comprise another substance for facilitating treatment of a patient, such as replacement blood orother bodily fluids, or a suitable medicine (e.g. a drug, a vaccine or other composition to be applied to the patient to be treated). Embodiments may find particular utility for the preservation of biological products which would benefit from (or require) their temperature to be tightly controlled prior to use. For example, this may reduce the likelihood of the product deteriorating during the period in which it is being preserved (i.e. prior to its subsequent use for treating a patient). The apparatus is configured to preserve the biological product. Preservation of the biological product may comprise retaining the biological product in an environment whose temperature is controlled. For instance, the controller may be configured to control operation of the thermoelectric modulation device to manage a temperature of the biological product, thereby to provide preservation of said product. Preservation of the product may comprise retaining the product in selected conditions for the local environment to that product, such as retaining the local temperature to the product within a selected temperature range. The apparatus may be configured to preserve the product whether the apparatus is stationary or moving. For example, the product may be stored in the apparatus and / or transported within the apparatus. In otherwords, the apparatus may be portable, e.g. to facilitate transport of the apparatus (and said product therein). During either storage or transportation, the apparatus may be configured to provide preservation (e.g. thermal management) of the product. The container unit may be configured to preserve the biological material in preservation liquid. For example, one or more walls of the container unit may define an internal volume which is filled with preservation liquid. The biological product, e.g. body tissue, may be provided in the preservation liquid within the container unit. For example, this may further facilitate preservation of the product. The controller may be configured to control operation of the thermoelectric modulation device to manage a temperature of the preservation liquid within the container unit (e.g. to retain the preservation liquid within a selected temperature range). The apparatus may comprise a fluid delivery system configured to circulate fluid to the product in the container unit. The fluid delivery system may be configured to supply a gas to the product, e.g. to supply a gas to the body tissue. The apparatus may be a persufflation apparatus and the fluid delivery system may comprise a persufflation gas supply system configured to supply persufflation gas to body tissue in the container unit. For example, the apparatus may be configured to deliver persufflation gas to body tissue in the preservation liquid in the container unit. The controller may be configured to control operation of the thermoelectric modulation device to manage the transfer of thermal energy between the thermal energy store and the container unit. The thermoelectric modulation device may comprise a thermoelectric device configured to modulate temperature, e.g. to control the flow of thermal energy (thermoelectrically). For example, the thermoelectric device may be configured to manage (e.g. regulate) the flow of thermal energy thereacross. That is, the thermoelectric modulation device may be configured to selectively direct heat from one side of the device to the other side, and vice-versa. The thermoelectric modulation device may be configured to regulate the transfer of thermal energy. The thermoelectric modulation device may comprise a thermoelectric cooler (e.g. which uses thermoelectric cooling), such as Peltier device, e.g. it may comprise a plurality of Peltier devices arranged to operate together. The thermoelectric modulation device (e.g. the Peltier device) may be configured to direct heat in either direction (thereby to selectively provide heating and / or cooling, as relevant). For example, a thermal transfer path may be defined between the thermal energy store and the container unit, and the controller may be configured to manage the flow of thermal energy along (at least a portion of) the thermal transfer path. The thermal transfer path may couple at least one surface of the container unit to at least one surface of the thermal energy store. The apparatus may be configured to manage a temperature of preservation liquid in the container unit by controlling operation of the thermoelectric modulation device to manage the transfer of the thermal energy along the thermal transfer path. The apparatus may be configured to permit two-way thermal transfer along the thermal transfer path (e.g. both ways across the thermoelectric modulation device). The apparatus may be configured to provide closed loop thermal transfer between the container unit and the thermal energy store. A portion of the thermal transfer path may be provided by material of a base unit (which houses the container unit). The base unit may comprise a volume of material arranged to provide a thermal energy conduit (e.g. along which thermal conduction is preferable to its surrounding material). A first such thermal energy conduit may extend from the thermal energy store towards the thermoelectric device. A second such thermal energy conduit may extend from the thermoelectric device towards the container unit (e.g. towards a container unit receiving portion of the base unit). The thermoelectric device may be configured to regulate the flow of thermal energy along said first and second thermal conduits of the base unit (e.g. to manage a flow of thermal energy between the thermal energy store and the container unit). The controller may be configured to control operation of the thermoelectric modulation device based on a selected temperature range for the apparatus. The selected temperature range may be selected based on the biological product to be preserved, e.g. based on the type of body tissue in the container unit. The controller may be configured to set the selected temperature range based on a received input signal. For example, the controller may be configured to obtain an indication of one or more details about the biological product to be preserved (e.g. the body tissue to be preserved). The controller may be configured to set the selected temperature range based on said one or more obtained details and / or based on stored data associated with the particular type of biological product (e.g. body tissue to be preserved). The controller may be configured to: (i) receive an input signal indicative of a selected temperature range for the biological product to be preserved, and (ii) control operation of the thermoelectric modulation device based on the selected temperature range. The controller may be configured to control operation of the thermoelectric modulation device based on a selected temperature set point. The selected temperature set point may comprise a selected temperature value. The selected temperature value may be for temperature(s) obtained from one or more temperature sensors of the apparatus. For example, the selected temperature set point may specify a selected temperature value to be provided at a selected location of the apparatus and / or from a specific sensor of the apparatus. This location may be between the thermoelectric device and the container unit. The selected temperature set point may be for temperature sensor(s) of the apparatus located between the thermoelectric modulation device and the container unit. The selected temperature set point (e.g. the selected temperature value) may be indicative of a temperature of the product in the container unit, e.g. it may be obtained from a sensor located between the thermoelectric device and the container unit. Controlling operation of the thermoelectric modulation device based on the selected temperature set point may comprise permitting the temperature to be within a selected range which encompasses the selected temperature set point. The selected range may comprise values above and below the temperature set point (e.g. within a threshold amount of the set point). The controller may be configured to control operation of the thermoelectric modulation device to be at a lower power level or in an inactive state when the temperature is within the selected range. In response to the temperature being at a value outside the selected temperature range, the controller is configured to control operation of the thermoelectric modulation device to adjust the temperature back towards the selected range (e.g. to operate the thermoelectric device to provide heating or cooling, as required - e.g. to return said temperature back towards the selected temperature range). When at a temperature value outside the selected range, the controller may be configured to operate the thermoelectric modulation device at a higher power level. For example, the controller may be configured to control operation of the thermoelectric modulation device to adjust a temperature of the container unit in the event that an obtained temperature is outside a selected temperature range. The selected temperature range may comprise a set temperature and a buffer region either side of the set temperature. The controller may be configured to vary an amount of power available to the thermoelectric modulation device. The controller may be configured to permit the thermoelectric modulation device to use more power for cooling the container unit than for heating the container unit. The controller may be configured to dynamically vary the amount of power available to the thermoelectric modulation device. For example, the controller may be configured to vary one or more weightings which stipulate the amount of power available to the thermoelectric modulation device. A heating weighting may be set to control the amount of power available to the thermoelectric modulation device for heating, and a cooling weighting may be set to control the amount of power available for cooling. The cooling weighting may be greater than the heating weighting. The controller may be configured to adjust at least one weighting based on obtained sensor data. For example, the controller may be configured to adjust the one or more weightings based on ambient temperature data. The controller may be configured to increase a weighting as ambient temperature differs from the temperature set point by an increasing amount. For example, the controller may be configured to increase a cooling weighting (e.g. to permit more power to be used by the thermoelectric modulation device) in the event that the ambient temperature increases. For example, the increased cooling weighting may facilitate use of more power for cooling in circumstances where the ambient temperature is increased relative to the temperature set point. The controller may be configured to control operation of the apparatus based on power usage of the thermoelectric modulation device. For example, the controller may be configured to determine one or more ambient conditions for the apparatus based on a power draw from the battery. The apparatus may comprise one or more sensors configured to obtain an indication of a temperature of the thermal energy store. The controller may be configured to control operation of the apparatus based on said obtained indication of temperature of the thermal energy store. For example, the controller may be configured to determine a phase of the material in the energy store, and / or to determine when a phase change event has occurred for the material in the thermal energy store. The controller may be configured to predict when the material in the thermal energy store has all changed phase, e.g. melted. The controller may be configured to output a signal containing the predicted melt time. The apparatus may comprise one or more sensors configured to obtain an indication of ambient temperature. The controller may be configured to control operation of the apparatus based on said obtained indication of ambient temperature. The thermal energy store may comprise a housing for storing material to manage a temperature of preservation liquid in the container unit via the thermal transfer path. For example, the thermal energy store may store a material capable of being used in combination with the thermoelectric modulation device to cool the container unit (and the biological product therein). The apparatus may be arranged to facilitate replacement of the material stored in the housing. The housing may be removable. For example, the housing of the thermal energy store may be removed from the apparatus to permit replacement of the material therein. The thermal energy store may comprise a removable drawer, e.g. to enable material therein to be replaced. The material may comprise a phase change material, e.g. the thermal energy store may be configured to receive a phase change material. The phase change material may be selected to have a phase change temperature within a threshold temperature range of an intended temperature for the biological product. In other words, the phase change material may be selected to facilitate latent heat absorption when being used for managing the temperature of the biological product. In other words, the phase change material may be selected so that it will change phase during operation of the apparatus to preserve the product. For example, ice may be used, e.g. with that ice melting during use. The apparatus may comprise a base unit. The base unit may comprise the thermal energy store, the thermoelectric modulation device and a container unit receiving portion arranged to receive the container unit. The base unit may comprise one or more sensors which are used by the controller to control operation of the thermoelectric modulation device. At least one wall of the container unit receiving portion may be coupled to the thermal energy store via the thermoelectric modulation device. The apparatus may comprise at least one sensor configured to obtain an indication of a temperature of a thermal transfer path between the thermoelectric modulation device and the container unit receiving portion. The controller may be configured to control operation of the apparatus based on said obtained indication of the temperature of the thermal transfer path. One or more walls may define the container unit receiving portion. The thermal transfer path may comprise at least a portion of said one or more walls. The thermal transfer path may comprise one or more thermal conduits within the base unit which thermally couple: (i) the thermal energy store to the thermoelectric device, and (ii) the thermoelectric device to the container unit receiving portion. For example, the thermal conduits may provide a preferential thermal conduction path (e.g. which is more thermally conductive than their surrounding / neighbouring volumes of material). The thermal transfer path may comprise aluminium. The apparatus may comprise one or more sensors configured to obtain an indication of a temperature of the thermal energy store. The controller may be configured to control operation of the apparatus based on the obtained indication of temperature of the thermal energy store. Controlling operation of the apparatus based on the obtained temperature data may comprise determining an indication of a status of: (i) the biological product in the container unit, and / or (ii) the thermal energy store. The controller may be configured to output a status signal comprising an indication of the determined status. Determining an indication of the status of the thermal energy store may comprise determining a status of material in the thermal energy store. Determining the indication of the status may comprise determining an indication of a phase of the material in the thermal energy store. For example, the material in the thermal energy store may be (initially) in one phase state, and the controller may be configured to determine whether this material has changed phase and / or how much of the material (e.g. what proportion) has changed phase. For example, the material may initially be a solid, such as ice, and the phase change may comprise the solid, e.g. ice, melting to become a liquid, such as water. Determining the indication of the status may comprise determining a proportion of the material in the thermal energy which has changed phase, e.g. determining a proportion of the ice within the thermal energy store which has melted (and is now water). The controller may be configured to predict a time at which material in the thermal energy store should be refreshed based on the obtained indication of temperature of the thermal energy store. For example, the controller may be configured to predict a time at which a threshold amount (e.g. all) of the material within the energy store will have changed phase, e.g. when a threshold amount of ice within the thermal energy store has melted, e.g. when all of the ice within the thermal energy store has melted. The controller may be configured to output a prediction signal indicating the predicted time at which the material in the thermal energy store should be refreshed. The predicted time at which the material in the energy store should be refreshed may comprises a time at which a threshold amount of the material in the thermal energy store has changed phase, e.g. when all of the material has changed phase. The material in the thermal energy store may be water-based. The predicted time at which the material in the energy store should be refreshed may comprise a time at which all of the ice in the thermal energy store has melted (or at least when a threshold amount of the ice has melted). For example, the controller may be configured to: (i) predict a time when a threshold amount of the material in the thermal energy store will have changed phase, and (ii) output one or more signals indicative of the predicted time. The apparatus may be configured to display the predicted time, e.g. on a display of the apparatus. The apparatus may be configured to output one or more alerts once within a threshold amount of time from the predicted time (at which the material in the thermal energy store will have changed phase). The one or more sensors may be configured to obtain an indication of temperature at different heights within the thermal energy store. The controller may be configured to determine a proportion of the material within the thermal energy store which has changed phase based on temperature data associated with different heights within the thermal energy store. The controller may be configured to determine a change of phase has occurred based on a value of the temperature and / or a rate of change of the temperature. For example, the controller may be configured to determine a change of phase has occurred in response to detecting a rate of change of temperature at above a threshold amount. The controller may be configured to control operation of the apparatus based on a rate of change of temperature in the thermal energy store. The controller may be configured to determine a phase change event has occurred in the thermal energy store based on the rate of change of temperature. The controller may be configured to output an alert in response to determining that a threshold amount of the material stored in the thermal energy store has changed phase. The alert may comprise an indication of the time up to the predicted time at which all of the material will have changed phase, e.g. when all ice will have melted. The apparatus may output alert(s) at selected times before the predicted time. The controller may be configured to control operation of the apparatus based on temperature data obtained from each of the sensors (e.g. which are at different heights within the thermal energy store). The controller may be configured to determine an extent of phase changing having occurred for material in the thermal energy store based on a difference in obtained temperature data from the different sensors (e.g. temperature values for the different sensors and / or rate of change values for the temperature values from the different sensors). The controller may be configured to determine an indication of a temperature of body tissue in the container unit based on the obtained temperature data. The container unit may comprise a storage region for holding a liquid in which a biological product is to be preserved. The apparatus may also comprise an agitator configured to agitate liquid disposed in the storage region of the container unit. The agitator may be configured to distribute thermal energy throughout the preservation liquid in the container unit. For example, the agitator may be configured to inhibit thermal stratification occurring within the preservation liquid in the container unit. The agitator may be part of the container unit. The agitator may comprise at least one agitator port configured to deliver a fluid, e.g. a gas, to the storage region of the container unit to agitate the liquid therein. The agitator may be configured to deliver a fluid to the preservation liquid to agitate the preservation liquid, wherein that fluid is a fluid which is to be circulated to body tissue in the container unit. For example, the apparatus may be configured to deliver a gas, such as a persufflation gas, to the body tissue. The agitator may be configured to deliver gas, e.g. persufflation gas, to the preservation liquid in the container unit for agitation thereof. In other words, the agitator may be configured to deliver persufflation gas to the preservation liquid in the storage region, e.g. at least some of the persufflation gas which would otherwise be delivered to the product (e.g. body tissue) may be diverted into the preservation liquid to provide agitation thereof (e.g. through the agitator port). The agitator may be configured to bubble (persufflation) gas up through the preservation liquid in the storage region. The agitator may be coupled to the (persufflation) gas supply system to receive (persufflation) gas therefrom. The container unit may comprise an agitator conduit coupling an inlet port (for connecting to receive fluid, e.g. persufflation gas, to be circulated to the body tissue) to the agitator port. A passageway may extend between the inlet port and the outlet port (for coupling to the body tissue). The agitator conduit may be coupled to the passageway, e.g. to receive some of the gas which would otherwise travel through the outlet port towards the body tissue (for using that gas to agitate the preservation liquid). The agitator port may be in a lower portion of the storage region. The agitator port may be in a base of the storage region. The container unit may comprise a passageway which couples the inlet port to the outlet port. Said passageway may be external to the storage region of the container unit. The container unit may comprise a liquid region within the passageway. For example, the container unit may comprise a humidifier (e.g. which contains the liquid region) to humidify gas to be delivered to the body tissue (e.g. before that gas passes out through the outlet port towards the body tissue). The humidifier may be external to the internal volume of the container unit, e.g. on an exterior wall of the container unit. The container unit may be configured to bubble persufflation gas through liquid in the liquid region, e.g. thereby to humidify the persufflation gas, before that persufflation gas is delivered to the body tissue (e.g. for persufflation thereof). The apparatus may comprise an obstruction memberwithin the storage region of the container unit. The obstruction member may be configured to inhibit excess movement of the body tissue within the storage region. The obstruction member may provide ballast to reduce a volume of preservation liquid within the storage region. The obstruction member may comprise a plurality of apertures sized to permit movement of liquid therethrough but to inhibit movement of the body tissue therethrough. For example, the apertures may be configured to permit sloshing of liquid therethrough, but to inhibit movement of the body tissue (e.g. by more than a threshold amount). The obstruction member may comprise one or more flanges configured to contact at least one wall of the container unit. The flanges may surround a main portion of the obstruction member, and the main portion may define an internal region in which the body tissue to be preserved is retained. The obstruction member may be configured to retain the body tissue within said internal region. The obstruction member may be resilient. The agitator may be coupled to a surface of the container unit. At least one surface of the container unit receiving portion may be arranged to thermally couple the thermal energy store to a corresponding surface of the container unit. The agitator may be located adjacent to said corresponding surface of the container unit, e.g. the agitator port may be located proximal / adjacent to said surface of the container unit. The base unit may comprise a container unit receiving portion arranged to receive said container unit. At least one surface of the container unit receiving portion may be configured to thermally couple the container unit to a thermal management system for managing a temperature of the preservation liquid in the storage region. The agitator port may be disposed adjacent to said at least one surface of the container unit receiving portion. The agitator may comprise a fluid mover. For example, the agitator port may be located in a lower portion of the storage region in the container unit. The container unit is configured for delivering persufflation gas to the preservation liquid in the internal volume of the container unit, e.g. to bubble the persufflation gas through the preservation liquid. The container unit may be configured to deliver the persufflation gas into a lower region of the preservation liquid and to bubble this up through the preservation liquid. In an aspect, there is provided a base unit for a biological product preservation apparatus, the base unit comprising: a container unit receiving portion arranged to receive a container unit for preserving a biological product; a thermal energy store; a thermoelectric modulation device, wherein the thermal energy store is thermally coupled to the container unit receiving portion via the thermoelectric modulation device; and a controller configured to control operation of the thermoelectric modulation device to manage a temperature of a said biological product in a said container unit received in the container unit receiving portion. In an aspect, there is provided a method of preserving a biological product, the method comprising: preserving the biological product in a container unit, wherein the container unit is thermally coupled to a thermal energy store via a thermoelectric modulation device; and controlling operation of the thermoelectric modulation device to manage a temperature of the biological product in the container unit. In an aspect, there is provided a base unit for a body tissue persufflation apparatus, the base unit comprising: a persufflation gas supply system; a container unit receiving portion arranged to receive a container unit for holding preservation liquid in which a body tissue is to be preserved, and wherein the persufflation gas supply system is couplable to a said container unit to provide persufflation gas thereto for delivering said persufflation gas to said body tissue in said container unit; a thermal management system comprising: a thermal energy store; and a thermal transfer path arranged to couple at least one surface of the thermal energy store to one or more surfaces of a said container unit received in the container unit receiving portion; wherein the apparatus is configured to manage a temperature of preservation liquid in a said container unit using the thermal transfer path. The container unit receiving portion may comprise a portion of the thermal transfer path, and wherein said portion of the thermal transfer path is arranged to be adjacent to said one or more surfaces of a said container unit when received in the container unit receiving portion. Said portion of the thermal transfer path may be arranged to contact said one or more surfaces of said container unit. In an aspect, there is provided a method of persufflating body tissue comprising: preserving the body tissue in a preservation liquid in a container unit of a body tissue persufflation apparatus and supplying a persufflation gas to said body tissue, wherein one or more surfaces of said container unit are coupled to at least one surface of a thermal energy store via a thermal transfer path; and managing a temperature of the preservation liquid in the container unit using the thermal transfer path. Aspects of the present disclosure may comprise one or more computer program products comprising computer program instructions configured to program a controller to control operation of a biological product preservation apparatus to implement any of the methods disclosed herein. Figures Some examples of the present disclosure will now be described, byway of example only, with reference to the figures, in which: Fig. 1 is a schematic diagram of a biological product preservation apparatus. Fig. 2 is a schematic diagram of a biological product preservation apparatus. Fig. 3 is a schematic diagram of a container unit for a biological product preservation apparatus. In the drawings like reference numerals are used to indicate like elements. Specific Description Embodiments of the present disclosure are directed to apparatuses and methods for preserving a biological product. In particular, embodiments relate to the preservation of biological products which benefit from having refined temperature control during preservation. Forthis, the product is provided in a container unit that is thermally coupled to a thermal energy store via a thermoelectric modulation device, such as a Peltier device. A controller is configured to manage the flow of thermal energy through the thermoelectric modulation device, e.g. from the thermal energy store to the container unit and from the container unit to the thermal energy store. The controller may receive temperature data from one or more sensors, and it may use this temperature data to control the operation of the thermoelectric modulation device, e.g. to manage the flow of thermal energy through the system (positively and / or negatively), so as to retain a temperature of the biological product within a selected temperature range. Embodiments may find particular utility in the field of preservation and storage of body tissue, such as organs. Likewise, embodiments may find particular utility as part of a persufflation system for delivering persufflation gas to the body tissue being preserved. A first example of a biological product preservation apparatus 1 will now be described with reference to Fig. 1. The Biological Product Preservation Apparatus of Fig. 1 The biological product preservation apparatus 1 includes a container unit 100 and a base unit 200. The container unit 100 includes a storage region for preserving the biological product. In the example of Fig. 1, the biological product is body tissue 10, such as an organ. The base unit 200 comprises a thermal energy store 210, a thermoelectric modulation device 225, a container unit receiving portion 227 and a controller 250. The base unit 200 includes a thermal energy store housing 221, as well as first portion 222 and second portion 226. A thermal transfer path is defined between the thermal energy store 210 and the container unit receiving portion 227, e.g. from the thermal energy store 210, through the housing 221, the first portion 222, the thermoelectric modulation device 225, second portion 226 and to the container unit receiving portion 227 (or in reverse). Thermal transfer may then occur between the container unit receiving portion 227 and the container unit 100 (e.g. via air gap 230). The base unit 200 also includes a container unit transfer sensor 255. As shown in Fig. 1, the container unit 100 is inserted into the base unit 200 (into the container unit receiving portion 227). There may be an air gap 230 between at least some portions of the container unit 100 and the wall(s) which define the container unit receiving portion 227. Although not shown in Fig. 1, the apparatus 1 may include an energy storage device, such as a battery. Likewise, the apparatus 1 will include a lid which seals the container unit 100 and also the base unit 200, but for simplicity, this is not shown in Fig. 1. The container unit 100 comprises one or more walls which define an internal storage volume forthe container unit 100. The body tissue 10 is disposed in the internal storage volume of the container unit 100. The container unit receiving portion 227 of the base unit 200 comprises one or more walls which surround an open volume for receiving the container unit 100. With the container unit 100 received in the container unit receiving portion 227 of the base unit 200 (as shown in Fig. 1), the one or more walls of the container unit 100 will be held in close proximity to the one or more walls of the container unit receiving portion 227. These may be separated by the airgap 230. For example, the walls of the container unit 100 may run parallel to the corresponding walls of the container unit receiving portion 227 (e.g. or at least approximately parallel). The container unit 100 may be a consumable product. For instance, it may be a single-use component. As will be appreciated, for the preservation of biological products, such as body tissue 10, any components which come into contact with that body tissue 10 may need to be discarded after use. The container unit 100 may be arranged to retain the body tissue 10 in the internal volume so as to permit multiple uses of the base unit 200, e.g. with different subsequent container units. The thermal energy store 210 provides a volume for holding material for storing thermal energy. The thermal energy store 210 may comprise an internal volume for receiving such material. The base unit 200 may have a corresponding recess in which the thermal energy store 210 is received. At least a portion of the thermal energy store 210 may be removable from the base unit 200. For example, the thermal energy store 210 may comprise a drawer which can hold material in its internal volume. The drawer may be removable from the base unit 200 to permit replacement of the material in its internal volume. While numerous different materials could be used within the thermal energy store 210, ice may be particularly beneficial due to its abundance in medical settings, and also due to its melting temperature being close to desired preservation temperatures for many biological products. In use, the thermal energy store 210 may be filled with the material, e.g. filled with ice. At least a portion of the base unit 200 which surrounds the thermal energy store 210 may be provided by housing 221. The housing 221 may comprise one or more walls which define the internal volume into which the thermal energy store 210 is provided. For example, where the thermal energy store 210 is provided by a drawer, the housing 221 may provide at least some of the walls which surround the space into which the thermal energy store 210 may be slid. A thermal transfer path of the base unit 200 is defined which thermally couples the housing 221 to the container unit receiving portion 227 (and thus which couples the thermal energy store 210 to the container unit 100). The thermal transfer path may be provided by a separate material to the rest of the base unit 200. For example, the thermal transfer path may be formed of a material with high thermal conductivity, such as aluminium. The thermal transfer path may provide a preferential flow path for thermal energy to and / or from the container unit receiving portion 227 and the housing 221. For example, the thermal transfer path may be provided by a volume of material which is more thermally conductive than the adjacent / neighbouring material. For this, for example, the housing 221, first and second portions 222 and 226, and at least one portion of the container unit receiving portion 227 may be formed from material(s) which is of higher thermal conductivity than the material surrounding those portions. The container unit receiving portion 227 may comprise one or more walls of material which form part of the thermal transfer path. For example, the majority, e.g. all, of the container unit receiving portion 227 may form part of the thermal transfer path. For example, the same material which provides the housing 221 and / or the first and second portions 222, 226 may provide the wall(s) of the container unit receiving portion 227. In other words, with the container unit 100 received in the container unit receiving portion 227, the container unit 100 may be at least partially surrounded by material which provides the thermal transfer path, e.g. substantially completely surrounded. The thermoelectric modulation device 225 may comprise a Peltier device (e.g. a Peltier heat pump). For example, the thermoelectric modulation device 225 may be formed of a plurality of Peltier devices. The plurality of Peltier devices may be arranged to operate in tandem with each other. The thermoelectric modulation device 225 may be connected to the battery (not shown in Fig. 5). The thermoelectric modulation device 225 is provided in the thermal transfer path between the housing 221 and the container unit receiving portion 227 (e.g. between the thermal energy store 210 and the container unit 100). For example (and as shown in Fig. 1), the thermal energy store 210 may be located beneath the thermoelectric modulation device 225, and the thermoelectric modulation device 225 may be located beneath the container unit receiving portion 227. The thermal energy store 210 may be thermally coupled (e.g. connected) to the thermoelectric modulation device 225 via the first portion 222 of the thermal transfer path. The thermoelectric modulation device 225 may be thermally coupled (e.g. connected) to the container unit receiving portion 227 via the second portion 226 of the thermal transfer path. In other words, the thermoelectric modulation device 225 may be interposed within the thermal transfer path between the thermal energy store end (e.g. the housing 221) and the container unit end (e.g. the container unit receiving portion 227). At least one sensor may be provided in the apparatus 1. In Fig. 1, the sensor shown is in the base unit 200, e.g. in the form of the container unit transfer sensor 255. The container unit transfer sensor 255 may be arranged between the thermoelectric modulation device 225 and the container unit receiving portion 227 (e.g. in the second portion 226 of the thermal transfer path). The container unit transfer sensor 255 is coupled to the controller 250. The controller 250 is coupled to the thermoelectric modulation device 225. These couplings are shown by the dashed lines in Fig. 1. The base unit 200 is configured to receive the container unit 100 in the container unit receiving portion 227 and to hold the container unit 100 within thermal transfer range of the container unit receiving portion 227, e.g. in close proximity to each other. Likewise, the base unit 200 is configured to receive the thermal energy store 210 within the housing 221 and to hold the thermal energy store 210 within thermal transfer range of the housing 221, e.g. in close proximity to each other and / or even in contact with each other. The container unit receiving portion 227 is configured to thermally couple to the container unit 100. That is, the container unit 100 and container unit receiving portion 227 are configured to exchange thermal energy therebetween. For example, in the event that the container unit 100 is hotter than the container unit receiving portion 227, the container unit 100 may radiate heat to the container unit receiving portion 227, and vice-versa. In other words, the container unit receiving portion 227 is arranged to thermally couple with the container unit 100 for adjusting a temperature thereof (and thus for managing a temperature of the body tissue 10 in the container unit 100). Likewise, the housing 221 is configured to thermally couple to the thermally energy store. That is, the thermal energy store 210 and the housing 221 are configured to exchange thermal energy therebetween. For example, in the event that the thermal energy store 210 is hotter than the housing 221, the thermal energy store 210 may conduct and / or radiate heat to the housing 221, and vice-versa. In other words, the thermal energy store 210 is arranged to thermally couple with the housing 221 for adjusting a temperature thereof. As such, a thermal transfer path may be defined between the material in the thermal energy store 210 (e.g. the ice) and the biological product in the container unit 100 (e.g. the body tissue 10). The material in the thermal energy store 210 may be used for heating or cooling the container unit 100 (e.g. for two-way transfer). That is, thermal energy may be transferred along the thermal transfer path from the container unit 100 to the thermal energy store 210 or along the thermal transfer path from the thermal energy store 210 to the container unit 100. The thermoelectric modulation device 225 is configured to manage the transfer of thermal energy along the thermal transfer path between the thermal energy store 210 and the container unit 100. That is, the thermoelectric modulation device 225 is configured to selectively control the direction in which the thermal energy is transferred. The thermoelectric modulation device 225 is also configured to selectively control the amount of thermal energy which is transferred in that direction. As will be appreciated in the context of the present disclosure, for this, by reversing the current applied, it is possible to select whether heat flows towards the container unit 100 or towards the thermal energy store 210. In other words, the apparatus 1 is configured to provide active control of the thermoelectric modulation device 225, e.g. to provide active selection of which way the thermal energy will flow through along the thermal transfer path. To provide cooling of the container unit 100, the thermoelectric modulation device 225 is configured to transfer heat from its container unit side to its thermal energy store side. As such, heat will flow through the thermoelectric modulation device 225 from the second portion 226 to the first portion 222. In turn, this will cause heat to be conducted from the container unit receiving portion 227 towards the second portion 226 of the thermal path, thereby to cool the container unit receiving portion 227, and for heat to be radiated from the container unit 100 to the container unit receiving portion 227. The heat from the first portion 222 of the thermal path will be conducted to the housing 221 and to the material in the thermal energy store 210 (via conduction and / or radiation), thereby to heat the material in the thermal energy store 210. To provide heating of the container unit 100, the thermoelectric modulation device 225 is configured to transfer heat from its thermal energy store side to its container unit side. As such, heat will flow through the thermoelectric modulation device 225 from the first portion 222 to the second portion 226. In turn, this will cause heat to be conducted from the second portion 226 of the thermal path towards the container unit receiving portion 227, thereby to heat the container unit receiving portion 227, and for heat to be radiated from the container unit receiving portion 227 to the container unit 100. Heat from the housing 221 will be conducted to the first portion 222 of the thermal path, thereby to reduce a temperature of the material in the thermal energy store 210. In other words, the apparatus 1 is configured to provide closed loop thermal transfer between the thermal energy store 210 and the container unit 100. As will now be described in more detail, the controller 250 is configured to selectively control operation of the thermoelectric modulation device 225 to control the flow of thermal energy between the thermal energy store 210 and the container unit 100, thereby to manage a temperature of the container unit 100. Control of the Thermoelectric Modulation device The controller 250 is configured to control operation of the thermoelectric modulation device 225. That is, the controller 250 is configured to selectively control the flow of thermal energy across the thermoelectric modulation device 225. For example, the controller 250 may be configured to selectively apply an electrical signal to the thermoelectric modulation device 225, thereby to control the flow of thermal energy between the container unit 100 and thermal energy store 210 (across the thermoelectric modulation device 225). The controller 250 is configured to obtain an indication of at least one temperature of the apparatus 1. In the case of Fig. 1, the controller 250 is configured to obtain the indication of temperature from the container unit transfer sensor 255. The container unit transfer sensor 255 is configured to obtain an indication of a temperature between the thermoelectric modulation device 225 and the container unit 100 (in this case in the second portion 226 of the thermal path). The controller 250 is configured to control operation of the thermoelectric modulation device 225 based on the obtained indication of temperature. The controller 250 is configured to control operation of the thermoelectric modulation device 225 to manage a temperature of the container unit 100. Advantageously, the use of a thermoelectric modulation device 225 may provide precise control overthe temperature of the container unit 100. In particular, the thermoelectric modulation device 225 may enable management of the temperature of the container unit 100 in both directions (i.e. to increase or decrease a temperature of the container unit 100). For example, in the event that the obtained temperature exceeds an upper threshold value, the controller 250 may control operation of the thermoelectric modulation device 225 to reduce the temperature. In the event that the obtained temperature is below a lower threshold value, the controller 250 may control operation of the thermoelectric modulation device 225 to increase the temperature. The controller 250 may continue this operation of the thermoelectric modulation device 225 until the obtained temperature is back within the selected temperature range, e.g. until it has reached the temperature set point again. Additionally, this advantageous control over container unit 100 temperatures may be achievable over a wide range of ambient conditions. The controller 250 is configured to control operation of the thermoelectric modulation device 225 based on a set point for the temperature. In the case of Fig. 1, the set point may be for the obtained indication of temperature received by the controller 250 (e.g. from the container unit transfer sensor 255). As will be appreciated in the context of the present disclosure, the temperature obtained by the container unit transfer sensor 255 will be indicative of the temperature of the container unit 100. For example, the controller 250 may store information, such as a lookup table, linking a temperature from the container unit transfer to a corresponding temperature of the container unit 100. The controller 250 may be configured to control operation of the thermoelectric modulation device 225 based on an intended corresponding temperature for the container unit 100 (using temperature data obtained from the container unit transfer sensor 255). Additionally, or alternatively, a different location for the sensor may be utilised, with the controller 250 still controlling operation based on the corresponding temperature for the container unit 100. In particular, the sensor may be part of the base unit 200. The sensor may be coupled to a portion of the thermal transfer path in the base unit 200, such as between the thermoelectric modulation device 225 and up to the container unit receiving portion 227. This may be of particular utility where the container unit 100 is a consumable product. As such, the relevant sensor electronics may be capable of operating repeatedly with subsequent consumables. This may also simplify the design of the container unit 100. The controller 250 may be configured to control operation of the thermoelectric modulation device 225 based on the set point for the temperature. For this, the controller 250 may be configured to apply a buffer region for temperature values either side of the temperature set point. The controller 250 may be configured to only activate the thermoelectric modulation device 225 to adjust a temperature in the event that the temperature exceeds the buffer region (e.g. if the temperature is outside of a selected temperature range). This approach may prevent excessive swings in temperature and power usage for the apparatus 1. The controller 250 may be configured to control operation of the thermoelectric modulation device 225 using weightings for how much power the thermoelectric modulation device 225 may draw. For example, the controller 250 may be configured to permit the thermoelectric modulation device 225 to draw more power when cooling the container unit 100 than when heating the container unit 100. As will be described in more detail below in relation to Fig. 2, the controller 250 may be configured to adjust the weightings dynamically, e.g. based on data obtained from one or more sensors. Another advantage of the thermoelectric modulation device 225 is that the temperature set point may be varied. The controller 250 may be configured to receive an indication of a temperature set point. This indication may be in the form of an input signal containing a temperature set point. Additionally, or alternatively, the indication may be in the form of an input signal indicating what the biological product is, e.g. what sort of body tissue it is. The controller 250 may store an indication of different temperature set points for different biological products, e.g. in a look up table. Likewise, the controller 250 may either receive an indication of values for the buffer region and / or weightings or it may determine these based on stored data. The controller 250 may then control operation of the thermoelectric modulation device 225 based on the temperature set point (and optionally based on the buffer values and / or weightings). Operation of the Apparatus In operation, the controller 250 receives an indication of the biological product to be preserved. For example, the indication may be of the particular type of body tissue 10 which is in the container unit 100. Based on this indication, a temperature set point is set for the preservation of the body tissue 10. Likewise, values for the buffer region of temperature values are set (e.g. upper and lower threshold values for temperature). The controller 250 then monitors temperatures obtained from the container unit transfer sensor 255. The thermoelectric modulation device 225 may remain inactive (or passive) while the obtained temperature remains between the lower and upper threshold temperature values. This includes temperature values beyond the temperature set point, but which are within a buffer region of this temperature value. In response to obtaining a temperature value which is outside the selected temperature range, the controller 250 will activate the thermoelectric modulation device 225 to adjust this temperature back towards the selected range. For example, if the temperature is too high, then the controller 250 activates the thermoelectric modulation device 225 to provide cooling of the container unit 100. In which case, heat is effectively transferred from the container unit 100 to the material in the thermal energy store 210. For this, the heat transfer may be radiative from the container unit 100 to the container unit receiving portion 227, and conductive towards the thermoelectric modulation device 225. This heat then passes through the thermoelectric modulation device 225 and to the material in the thermal energy store 210 (e.g. conductively and / or radiatively). Likewise, if the temperature is too low, then the controller 250 activates the thermoelectric modulation device 225 to provide heating of the container unit 100. Under typical operating conditions, the likelihood is that the container unit 100 will be kept at a temperature higher than a temperature of the material in the thermal energy store 210. For instance, the material in the thermal energy store 210 may comprise ice, and the temperature set point may be slightly above zero, e.g. between 4 and 12 degrees Celsius. Ambient temperature may be above this temperature set point, and so the majority of the thermal transfer may be to use the ice in the thermal energy store 210 to cool the body tissue 10 in the container unit 100 (e.g. for the thermoelectric modulation device 225 to direct thermal energy from the container unit 100 to the stored ice). However, in the event that the temperature drops too low, this process may be reversed so that the thermoelectric modulation device 225 acts as a heater for heating the container unit 100. As such, the controller 250 may control operation of the thermoelectric modulation device 225 to retain a temperature of the container unit 100 (and thus the biological product therein) within a threshold temperature range. Another example of a biological product preservation apparatus 1 will now be described with reference to Fig. 2. Biological product preservation apparatus of Fig. 2 The apparatus 1 of Fig. 2 is similar to that of Fig. 1, and so repeat components shall not be described again here. As with the apparatus 1 of Fig. 1, for the apparatus 1 of Fig. 2, a thermal transfer path is defined between the thermal energy store 210 and the container unit 100, and the thermoelectric modulation device 225 is arranged to manage the transfer of thermal energy therebetween. The apparatus 1 of Fig. 2 also includes additional features and functionality to facilitate improved preservation of biological products. For instance, the apparatus 1 of Fig. 2 is configured for preserving body tissue 10 and for circulating fluid through that body tissue 10 for improved preservation of the body tissue 10. In particular, the apparatus 1 may be configured to provide persufflation of body tissue 10 in the container unit 100. That body tissue 10 may also be provided within a pool of preservation liquid 110. For this, and as shown in Fig. 2, the apparatus 1 may include a persufflation gas store 240, a gas delivery, an inlet connection 141, tubing 142, an outlet connection 143, a gas receiving line 243 and a gas outlet 244. The container unit 100 may also hold preservation liguid 110. The apparatus 1 of Fig. 2 also includes one or more additional sensors to those shown in Fig. 1. As shown, these may include first sensor 251, second sensor 252, third sensor 253, thermal energy store transfer sensor 254, ambient sensor 256, a container unit receiving portion sensor 257 and / or an air gap sensor 259. A battery 258 is also shown in Fig. 2. These additional sensors / components may enable further control of the thermoelectric modulation device 225 to that described in relation to Fig. 1, as well as additional control of other aspects of the apparatus 1, and in particular for the thermal energy store 210. Each of these different aspects of the apparatus 1 of Fig. 2 will now be described in turn in more detail. Preservation of body tissue As already mentioned, the apparatus 1 may be configured to preserve a biological product in the form of body tissue 10, such as a replacement organ. For this, it may be beneficial to store the body tissue 10 in a preservation liquid 110. One or more walls of the container unit 100 define an internal volume arranged to receive preservation liquid 110 in which the body tissue 10 is to be provided. As shown in Fig. 2, the body tissue 10 may be at least partially submerged within the preservation liquid 110 in the container unit 100. The body tissue 10 may float in the preservation liquid 110 in the container unit 100. As with the apparatus 1 of Fig. 1, one or more external surfaces of the container unit 100 are configured to couple thermally with the material of the container unit receiving portion 227. This forms part of a thermal coupling between the container unit 100 and the thermal energy store 210 (via the thermoelectric modulation device 225). In addition to the radiative thermal transfer between the container unit receiving portion 227 and the wall(s) of the container unit 100, thermal energy will be thermally transferred (e.g. conductively) between the wall(s) of the container unit 100 and the preservation liquid 110 stored in the internal volume of the container unit 100. In turn, thermal energy may be transferred (e.g. conductively) between the preservation liquid 110 and the body tissue 10 therein. In so doing, by controlling operation of the thermoelectric modulation device 225, the apparatus 1 is configured to control a temperature at which the body tissue 10 is preserved (e.g. a temperature of the preservation liquid 110 in the container unit 100). In other words, the apparatus 1 may be configured to manage a temperature of the preservation liquid 110 in the container unit 100. In particular, the controller 250 may be configured to control operation of the thermoelectric modulation device 225 to manage the thermal transfer between the thermal energy store 210 and the preservation liquid 110 in the container unit 100. In so doing, the controller 250 may be configured to retain a temperature of the preservation liquid 110 (and thus a temperature of the body tissue 10) within a selected temperature range. Additionally, or alternatively, for the preservation of body tissue 10 within the container unit 100, the apparatus 1 may be configured to circulate fluid to that body tissue 10, e.g. to the native vasculature of the body tissue 10. While this may comprise circulation of a liquid perfusate through the body tissue 10, in the example of Fig. 2, the apparatus 1 is a body tissue 10 persufflation apparatus configured to supply gaseous oxygen perfusate to the body tissue 10. For this, the apparatus 1 comprises the persufflation gas store 240. This may comprise a gas cannister which stores persufflation gas (and / or it may comprise means for onboard generation of persufflation gas). One or more fluid conduits are provided for connecting the gas store 240 to the body tissue 10. The gas delivery line 241 is connected to the gas store 240. The base unit 200 houses the gas store 240 and the gas delivery line 241. The gas delivery line 241 (of the base station) may couple to one or more conduits for connection to the body tissue 10. As mentioned above, the container unit 100 and any conduits of the container unit 100 may themselves be single-use (e.g. consumable) products. The base unit 200 may be multi-use. The apparatus 1 may comprise a plurality of couplings for connecting gas flow line(s) of the base unit 200 to the components in the container unit 100. As shown in Fig. 2, the inlet connection 141 couples the gas delivery line 241 to the tubing 142. The tubing 142 may comprise one or more different fluid conduits for coupling the gas delivery line 241 to the body tissue 10, e.g. to different portions of the native vasculature of the body tissue 10 (e.g. to different veins and / or arteries). In Fig. 2, the tubing 142 is shown by two dashed lines, but this is just to show the flow path through the body tissue 10. It is to be appreciated however that one or more pieces of tubing 142 may be coupled to the body tissue 10 to deliver input gas and one or more pieces of tubing 142 may be coupled to the body tissue 10 to receive gas which has passed through the body tissue 10 from the input tubing. The output tubing portion(s) may couple to the base unit 200 for delivering gas thereto. As shown in Fig. 2, the outlet connection 143 couples the tubing 142 to the gas receiving line 243 of the base unit 200. In other words, a gas flow path is defined through the apparatus 1 for delivering persufflation gas to the body tissue 10. The apparatus 1 may deliver persufflation gas from the gas store 240 (in the base unit 200) to the body tissue 10 (in the container unit 100) via this flow path. The apparatus 1 may also define a flow path for receiving this gas which has been delivered to the body tissue 10, and for returning this gas to the base unit 200. The base unit 200 may comprise a storage component (e.g. gas canister) for receiving the discarded gas, and / or the apparatus 1 may comprise an outlet for venting gas. In Fig. 2, the gas outlet 244 is shown. The gas outlet 244 is configured to vent persufflation gas which has passed through the body tissue 10 (e.g. which has been received from the tubing 142 via the gas receiving line 243). As will be described in more detail below, the apparatus may also include one or more other gas flow paths for delivering gas through the apparatus. The apparatus may include a gas flow path arranged to deliver gas into preservation liquid in the container unit. For example, this gas flow path may be coupled to the container unit, e.g. to a lower region thereof (such as in a floor of the container unit), to deliver gas to that region of the container unit. This may cause that gas to bubble up through the preservation liquid therein. This gas flow path may be for persufflation gas (e.g. the same gas to be delivered to the body tissue), or it may be for another gas (e.g. a gas suitable for contacting the body tissue). Such an additional gas flow path may facilitate agitation of the preservation liquid in the container unit (e.g. to inhibit thermal stratification occurring therein). This gas flow path may be different, e.g. independent, to the gas flow path mentioned above for delivering gas to the body tissue, or the two may be connected (e.g. they may be two different branches for gas to flow from the same gas source). As will be described in more detail below in relation to Fig. 3, the container unit may be arranged to direct some of the gas that would be delivered from the gas flow path to the body tissue to a separate conduit for delivery into the bottom of the container unit. As such, apparatuses of the present disclosure may be configured to preserve body tissue 10 in a preservation liquid 110 within the container unit 100, and / or to circulate persufflation gas to this body tissue 10 in the container unit 100. Control of thermoelectric modulation device As described above in relation to Fig. 1, the controller 250 may be configured to control operation of the thermoelectric modulation device 225 based on obtained sensor data indicative of at least one temperature of the apparatus 1 (from the container unit transfer sensor 255). For the apparatus 1 of Fig. 2, the controller 250 may be configured to obtain data from additional or alternative sources. For this, the apparatus 1 may include the thermal energy transfer sensor, the ambient sensor256, the container unit receiving portion sensor 257 and / or the air gap sensor 259 (in addition to the container unit transfer sensor 255). Additionally, or alternatively, the controller 250 may be configured to obtain an indication of power output associated with usage of the battery 258. The battery 258 and / or the thermal energy transfer sensor and the ambient sensor 256 may be part of the base unit 200. The thermal energy transfer sensor may be coupled between the thermal energy store 210 and the thermoelectric modulation device 225. For example, and as shown in Fig. 2, the thermal energy transfer sensor may be coupled to the second portion 226 of the thermal transfer path. The ambient sensor 256 may be coupled to an external region of the apparatus 1 or it may be located proximal to an external region of the apparatus 1. The battery 258 may be part of the base unit 200. The battery 258 may be coupled to one or more components of the apparatus 1. In particular, the battery 258 may be coupled to the thermoelectric modulation device 225, e.g. which may use power from the battery 258 to control the flow of thermal energy across the thermoelectric modulation device 225. The controller 250 may be configured to obtain an indication of a temperature on a thermal energy store side of the thermoelectric modulation device 225 (e.g. from the thermal energy transfer sensor). The controller 250 may be configured to obtain an indication of a temperature on a container unit side of the thermoelectric modulation device 225 (e.g. from the container unit transfer sensor 255). The controller 250 may be configured to obtain an indication of an ambient temperature, e.g. for the environment in which the apparatus 1 is located (e.g. from the ambient sensor 256). The controller 250 may be configured to obtain an indication of an amount of power being used by the controller 250. The controller 250 may be configured to control an amount of power draw which is available to the thermoelectric modulation device 225, e.g. to control how much power the thermoelectric modulation device 225 may use. As will now be described in more detail, the controller 250 may be configured to control operation of the thermoelectric modulation device 225 based on such obtained data. As with Fig. 1, the controller 250 of Fig. 2 may be configured to control operation of the thermoelectric modulation device 225 to manage a temperature of the container unit 100, and the biological product therein (i.e. in the preservation liquid 110 in the container unit 100). In particular, the controller 250 may be configured to control operation of the thermoelectric data based on temperature from one or more sensors to maintain a temperature of the container unit 100 within a selected temperature range. The controller 250 may be configured to control operation of the thermoelectric modulation device 225 based on differential sensor data from sensors either side of the thermoelectric modulation device 225. For this, the controller 250 may use temperature data obtained from both the thermal energy store transfer sensor 254 and the container unit transfer sensor 255. As mentioned above in relation to Fig. 1, the controller 250 may utilise temperature data obtained from the container unit transfer sensor 255 as a proxy to temperature information for the container unit 100 itself. In other words, the controller 250 may be configured to infer a temperature of the container unit 100 (and biological product / preservation liquid 110 therein) based on a temperature of the thermal transfer path between the thermoelectric modulation device 225 and the container unit 100. By positioning the container unit transfer sensor 255 closerto the thermoelectric modulation device 225 (e.g. as compared to being in the container unit 100 itself or the container unit receiving portion 227), there may be a shorter response time between operation of the thermoelectric modulation device 225 being controlled in a certain way and the temperature data representing the effect of that operation. The controller 250 may be configured to utilise the temperature data on the other side of the thermoelectric modulation device 225 as well (i.e. for a temperature of the thermal transfer path between the thermoelectric modulation device 225 and the thermal energy store 210). For this, the controller 250 may use temperature data obtained from the thermal energy store transfer sensor 254. Again, by being closer to the thermoelectric modulation device 225, this temperature data may be more responsive to change from the thermoelectric modulation device 225. The controller 250 may be configured to use temperature data from sensors on either side of the thermoelectric modulation device 225 (e.g. from both the thermal energy store transfer sensor 254 and the container unit transfer sensor 255). In particular, the controller 250 may be configured to determine the flow of thermal energy across the thermoelectric modulation device 225 based on temperature data from both sides of the thermoelectric modulation device 225, e.g. based on a differential reading between data from the two sensors. The controller 250 may be configured to dynamically control operation of the thermoelectric modulation device 225. For this, the controller 250 may be configured to control whether or not the thermoelectric modulation device 225 is activated, as well as how much power the thermoelectric modulation device 225 is permitted to use (e.g. to draw from the battery 258). Data from the temperature sensors of the apparatus 1 may be used to manage these control aspects. The controller 250 may be configured to control operation of the thermoelectric modulation device 225 according to a temperature set point. This may be a temperature indicative of the container unit side of the thermal transfer path (e.g. from the container unit transfer sensor 255). For instance, the temperature set point which is controlled by the controller 250 (e.g. for a portion of the thermal transfer path between the thermoelectric modulation device 225 and the container unit 100) may be controlled according to a corresponding temperature for the container unit 100. In other words, the controller 250 may be configured to obtain a temperature from a portion of the thermal transfer path and to infer what a corresponding temperature of the container unit 100 will be based on the obtained temperature. The controller 250 may then control operation so that the inferred temperature is within a selected range. For this, the controller 250 may have a temperature set point. This may either be received (e.g. input from a user) oralready stored in a data store of the controller 250. The temperature set point may be associated with temperature data from a single sensor. In the example of Fig. 2, that sensor may be the container unit transfer sensor 255. The controller 250 may be configured to control operation of the thermoelectric modulation device 225 based on aligning the temperature data from the container unit transfer sensor 255 with the temperature set point. The controller 250 may be configured to permit a buffer zone either side of the temperature set point. That is, a selected range may be defined which includes the temperature set point, as well as some temperatures around this temperature set point. For example, the selected range may comprise values which are greater than the temperature set point by up to a first threshold amount and values which below the temperature set point by up to a second threshold amount (e.g. the two threshold amounts may be the same, so that the range is centred on the temperature set point). The controller 250 may be configured to retain the thermoelectric modulation device 225 in a low energy state while the obtained temperature is within the selected temperature range. For example, the thermoelectric modulation device 225 may be limited to relatively low power or it may be disactivated (controlled to be inactive) altogether. In the event that the obtained temperature extends beyond the selected temperature range, the controller 250 may be configured to control operation of the thermoelectric modulation device 225 accordingly. For this, the controller 250 may be configured to activate the thermoelectric modulation device 225 (if it was previously disactivated / inactive) or to increase power supplied to the thermoelectric modulation device 225. The controller 250 may control operation of the thermoelectric modulation device 225 so that the obtained temperature is restored back to the selected range, e.g. to either heat or cool the second portion 226 so as to bring the temperature there back into the selected range. The controller 250 may be configured to control the thermoelectric modulation device 225 to continue this heating / cooling until the temperature then re-enters the selected temperature range. The controller 250 may then reduce the power supplied to the thermoelectric modulation device 225 or disactivate it (to become inactive). The controller 250 may be configured to control power usage of the thermoelectric modulation device 225. For this, the thermoelectric modulation device 225 may be permitted to use a variable amount of power, e.g. to draw different amounts of power from the battery 258. The controller 250 may be configured to set one or more weightings for how much power the thermoelectric modulation device 225 is permitted to draw. The controller 250 may set the weighting(s) so that the thermoelectric modulation device 225 is permitted to draw more power for cooling the container unit 100 than for heating the container unit 100. That is, the apparatus 1 may have an asymmetry between algorithms for heating and cooling. The controller 250 may be configured to dynamically vary the weighting(s). That is, the controller 250 may be configured to variably change how much power the thermoelectric modulation device 225 is permitted to use, e.g. when heating and when cooling. In particular, the controller 250 may be configured to vary the weighting(s) based on obtained temperature data. As one example, the controller 250 may be configured to vary the weighting(s) based on ambient temperature data (e.g. from the ambient sensor 256). The controller 250 may be configured to vary the weighting(s) based on a difference between the temperature set point (or the selected temperature range) and the ambient temperature. As the ambient temperature differs by an increasing amount from the temperature set point, the controller 250 may increase a magnitude of the weighting(s). For example, the controller 250 may set a weighting for the amount of power the thermoelectric modulation device 225 is permitted to use for cooling based on an amount by which the ambient temperature differs from the temperature set point. Likewise, the controller 250 may set a weighting for the amount of power the thermoelectric modulation device 225 is permitted to use for heating based on an amount by which the ambient temperature differs from the temperature set point. As the ambient temperature becomes increasingly greater than the temperature set point, the controller 250 may increase the weighting for cooling power for the thermoelectric modulation device 225. As such, the thermoelectric modulation device 225 may provide greater cooling capacity for the container unit 100. Advantageously, this may enable the apparatus 1 to more tightly manage the temperature of the container unit 100, as it is less likely that changes in ambient temperature will be able to influence the temperature within the container unit 100. This may also mean the apparatus 1 is more robust for use in differing ambient conditions. Similarly, as the ambient temperature gets increasingly colder than the temperature set point, the controller 250 may increase the weighting for heating power for the thermoelectric modulation device 225. As another example, the controller 250 may be configured to vary the weighting(s) based on temperature data from the thermal energy store side of the thermal transfer path (from the opposite side of the thermoelectric modulation device 225 to the container unit 100). For instance, the controller 250 may be configured to vary the weighting(s) based on temperature data obtained from the thermal energy store transfer sensor 254 (or even one of the first, second or third sensors 251,252, 253). For this, the controller 250 may be configured to control the weighting(s) based on an indication of the amount of thermal energy stored in the thermal energy store 210 and / or a temperature of the thermal transfer path on the thermal energy store side of the thermoelectric modulation device 225. For example, the controller 250 may increase the weighting for cooling if the temperature on the thermal energy store 210 side is greater than the temperature set point. In other words, the controller 250 may control the weighting(s) based on a temperature differential across the thermoelectric modulation device 225. As the temperature differential increases in one direction, the weighting forthe other direction may increase, e.g. so that more power may be used for cooling as the thermal energy store 210 becomes increasingly hotter than the temperature set point (and vice-versa). The controller 250 may be configured to control operation of the thermoelectric modulation device 225 based at least in part on data indicative of power usage and / or the battery 258. For example, the controller 250 may be configured to control weightings based on an indication of remaining battery life, e.g. so that weighting(s) may reduce as battery life gets lower. Additionally, or alternatively, the controller 250 may be configured to monitor power draw from the battery 258 associated with operation of the thermoelectric modulation device 225. The controller 250 may be configured to utilise this information in a similar manner to that described above for the ambient sensing. That is, the controller 250 may be configured to determine that ambient temperature is elevated in response to identifying elevated power usage forthe thermoelectric modulation device 225 (e.g. due to the thermoelectric modulation device 225 requiring more power so as to provide cooling of the thermoelectric modulation device 225). As described above, the controller 250 may be configured to provide dynamical control of both: (i) how the thermoelectric modulation device 225 is operated (e.g. for heating or for cooling), and (ii) how much power the thermoelectric modulation device 225 may use for this operation. This control may enable the temperature of the container unit 100 to be reliably maintained within a precise and relatively narrow temperature range over an extended time period and even when subject to very different ambient conditions. This temperature management may be of particular benefit to the preservation of body tissue 10, as the tissue may be held in a desired temperature range associated with most beneficial preservation. Control of thermal energy store As described herein, thermal energy may be transferred between the thermal energy store 210 and the container unit 100 (along the thermal transfer path through the thermoelectric modulation device 225). This transfer of thermal energy is controlled to manage a temperature of the biological product in the container unit 100. A typical scenario for this is the preservation of body tissue 10 in preservation liquid 110 in the container unit 100, where the body tissue 10 is to be kept at a relatively cool temperature (e.g. somewhere between 4 and 12 degrees Celsius), and where the thermal energy store 210 initially stores ice. In this case, thermal energy may predominantly be transferred from the container unit 100 through the thermoelectric modulation device 225 and to the ice, where that is absorbed as latent heat (for melting the ice) and / or heating the mixture of ice / water in the thermal energy store 210. The use of ice in such scenarios may be beneficial as the melting temperature of ice is relatively close to the selected temperature range for the container unit 100, and so at least initially, a large amount of energy may be absorbed without a significant increase in temperature due to the latent heat transition from ice to water. As will be appreciated in the context of the present disclosure, the efficiency for operation of the thermoelectric modulation device 225 may vary in dependence upon a temperature differential across it. In particular, as the thermal energy store side of the thermoelectric modulation device 225 approaches the temperature of the container unit side and then increases above the temperature of the container unit side, the efficiency of the thermoelectric modulation device 225 for cooling of the container unit 100 will continue to decrease, thereby requiring increasingly greater amounts of power to provide cooling of the container unit 100. The present inventors have identified that improved operation of the thermoelectric modulation device 225 may be obtained through monitoring the contents of the thermal energy store 210, e.g. so as to be able to identify the thermal storage capacity of the thermal energy store 210. For this, the apparatus 1 may include one or more sensors for sensing a property of the thermal energy store 210. In the apparatus 1 of Fig. 2, three such sensors are provided in the thermal energy store 210: first sensor 251, second sensor 252, and third sensor 253. The one or more sensors within the thermal energy store 210 may each comprise a temperature sensor. Each sensor may be located at a different height within the thermal energy store 210. As shown in Fig. 2, the first sensor 251 is the lowest sensor, the third sensor 253 is the highest sensor, and the second sensor 252 is located between the first sensor 251 and the third sensor 253. The sensors may be distributed across a substantial portion of the overall height of the thermal energy store 210, e.g. with the first sensor 251 located towards the bottom of the thermal energy store 210 and the first sensor 251 located towards the top of the thermal energy store 210. Each sensor may be located in or adjacent to a wall of the thermal energy store 210 which houses material, such as ice. For example, with the thermal energy store 210 full of material, the sensors may be at least partially in contact with that material, or located adjacent to that material (e.g. coupled to it via another component). Each sensor is configured to obtain an indication of a temperature. In particular, each sensor may be configured to obtain an indication of a temperature of the material in the thermal energy store 210. The sensors are configured to obtain an indication of temperatures at different heights within the thermal energy store 210. For instance, the first sensor 251 may be configured to obtain an indication of a temperature in a lower region of the thermal energy store 210, with the second and third sensors 252, 253 being configured to obtain indications of temperatures in higher regions of the thermal energy store 210. In other words, the apparatus 1 is configured to obtain an indication of the temperature of the material in the thermal energy store 210 at different heights within the thermal energy store 210. The controller 250 may be configured to determine a thermal energy storage capacity of the thermal energy store 210 based on the data obtained from the thermal energy store 210. In particular, the controller 250 may be configured to determine a phase of the material in the thermal energy store 210, and / or a proportion of the material within the thermal energy store 210 in each phase. For the case of initially storing ice in the thermal energy store 210, the controller 250 may be configured to obtain an indication of an amount of melted ice within the thermal energy store 210. For temperature data obtained from each sensor within the thermal energy store 210, the controller 250 may be configured to determine whether or not the material adjacent to that sensor remains ice or if it has melted (to become water). For this, the controller 250 is configured to determine whether or not ice has melted based upon a value of the temperature and / or a rate of change in temperature values. For instance, at temperatures substantially below zero degrees Celsius, it may be determined that the ice has not melted, and at temperatures substantially above zero degrees Celsius, it may be determined that the ice has melted. For temperatures at or close to zero degrees Celsius, the controller 250 may be configured to determine whether the ice has melted based at least in part on a rate of change of temperature values. In particular, the controller 250 may be configured to determine that the ice has melted in response to detecting an increase in the rate of temperature change (versus time). In other words, in the event that the temperature begins to increase (from a value at approximately zero degrees Celsius), the controller 250 may infer that melting has occurred. The controller 250 may be configured to monitor temperature values from sensors at different heights within the thermal energy store 210 to determine how high within the thermal energy store 210 the melted ice has reached. In an initial state, the thermal energy store 210 may be filled with ice. As this ice begins to melt, water will accumulate at the bottom of the draw, and the remaining ice will begin to float upon that water. As such, water will fill up at the bottom pushing the ice upwards. Typically, the last ice to melt will be at the top of the thermal energy store 210, as it will have been continually pushed higher up due to rising water levels within the thermal energy store 210. The controller 250 is configured to monitor the obtained temperature data from each sensor within the thermal energy store 210. As already mentioned, for each sensor, the controller 250 may be configured to determine that ice at the height of that sensor within the thermal energy store 210 has melted in response to a change in the rate of increase of temperature within the thermal energy store 210 exceeding a threshold amount. By having numerous sensors in the thermal energy store 210 at different heights, the controller 250 may be configured to track the progress of the ice melt through the thermal energy store 210, e.g. to identify the rising water levels within the thermal energy store 210 (and thus further ice being melted). The controller 250 may be configured to determine a proportion of the ice which has melted within the thermal energy store 210 based on the height that the meltwater has reached within the thermal energy store 210. For example, the controller 250 may be configured to determine a percentage amount of ice remaining, e.g. based on stored data indicative of the expected final height for the meltwater within the thermal energy store 210. The controller 250 may be configured to predict when all the ice will have melted based on the rate of progression of ice melt within the thermal energy store 210. For example, the controller 250 may be configured to determine a proportion of the amount of melted ice within the thermal energy store 210. Based on this proportion and the amount of time taken since the ice was initially put within the thermal energy store 210, the controller 250 may be configured to predict when all of the ice will melt. The controller 250 may also be configured to take into account additional data streams, such as ambient temperature, a temperature of the container unit side of the thermal transfer path and / or an indication of power draw from the battery 258 when predicting the melt time. For example, the controller 250 may be configured to determine a quicker rate of melting in the event that ambient temperature or power usage for the thermoelectric modulation device 225 is elevated (e.g. as a greater amount of cooling may be needed). The controller 250 may be configured to control operation of the apparatus 1 based on the predicted melt time for the ice. The apparatus 1 may comprise a display screen or GUI. The controller 250 may be configured to display an indication of the predicted melt time on the display screen / GUI. For example, this may enable an operator of the apparatus 1 to have an idea of when they should replace the ice within the thermal energy store 210. The apparatus 1 may also be configured to output one or more alerts associated with the melt time. For example, the apparatus 1 may be configured to output an alert which is still a relatively long period of time away from the predicted melt time. This may be an hour or more before the predicted melting event occurs. The apparatus 1 may be configured to output an alert at a closer time to the predicted melt time and / or to output an alert in response to determining that all ice has melted within the thermal energy store 210. The alert(s) may comprise an indication that the ice within the thermal energy store 210 is to be refreshed. By monitoring the contents of the thermal energy store 210, the controller 250 may inform an operator of the apparatus 1 as to when they should be replacing the ice within the thermal energy store 210. In so doing, the apparatus 1 (and in particular the thermoelectric modulation device 225) may be operated at higher efficiency levels by retaining the material in the thermal energy store 210 in a more optimal range (for both temperature and phase). As will be appreciated, the present disclosure may also apply to use of other materials to ice, e.g. other phase change materials. The monitoring of the contents of the thermal energy store 210 may still be applicable when other materials are stored in the thermal energy store 210. Likewise, the above example may provide beneficial effects when implemented in an apparatus 1 which does not include a thermoelectric modulation device 225. Container unit of Fig. 3 An example container unit 100 will now be described with reference to Fig. 3. The container unit 100 of Fig. 3 may be used as part of the apparatus 1 of Figs. 1 and 2. Fig. 3 shows a container unit 100. As with the example of Fig. 2, the container unit 100 of Fig. 3 may be arranged to receive a preservation liquid 110, and to preserve a biological product such as body tissue 10 within that preservation liquid 110. The container unit 100 may also include an agitator. In the example of Fig. 3, the agitator includes agitator port 150 and an agitator conduit 155. As with Fig. 2, the container unit 100 includes one or more components for delivering fluid (e.g. persufflation gas) to the body tissue 10. For this, the container unit 100 includes an inlet connection 141, an inlet tubing connector 144, tubing 142, an outlet tubing connector 145 and an outlet connection 143. The container unit 100 may also include a humidifier 160. The humidifier 160 may include a humidifier inlet 162 and a humidifier outlet 164. An agitator connection 146 is also included. The container unit 100 may also include an obstruction member 120. The instruction member may comprise one or more flanges 122. Agitation of preservation liquid One or more walls of the container unit 100 define an internal volume in which preservation liquid 110 is to be stored. The body tissue 10 is placed in the preservation liquid 110 in the internal volume of the container unit 100. As described above in relation to Fig. 2, the apparatus 1 may be configured to manage a temperature of the preservation liquid 110 in the container unit 100 (e.g. using the thermoelectric modulation device 225). For this, one or more outer surfaces of the container unit 100 may be located in proximity of the container unit receiving portion 227 of the base unit 200, and heat may be transferred therebetween radiatively. The present inventors have identified that the biological product in the preservation liquid 110 may experience beneficial preservation by providing agitation of the preservation liquid 110 in the container unit 100. This approach may inhibit thermal stratification occurring within the preservation liquid 110 in the container unit 100, and so the biological product may experience a more uniform surrounding temperature. In turn, this may facilitate better temperature management of the body tissue 10, as the temperature in closest proximity to the thermal transfer path in the base unit 200 (i.e. the liquid adjacent to the walls of the container unit 100) will be at a temperature which is more representative of the temperature felt by the biological product. For the container unit 100 of Fig. 3, agitation of the preservation liquid 110 may be provided through delivery of a gas to the preservation liquid 110. In particular, a gas may be bubbled through the preservation liquid 110 from a lower portion thereof. This gas bubbling may act to distribute heat more uniformly within the preservation liquid 110. For this, the container unit 100 comprises the agitator port 150 and the agitator conduit 155. The agitator port 150 comprises an inlet to the internal volume of the container unit 100. The agitator port 150 may be located in a floor (bottom wall) of the container unit 100. For example, the agitator port 150 may provide an opening into a lower region of the internal volume of the container unit 100. The agitator port 150 is coupled to a supply of gas by the agitator conduit 155. The agitator conduit 155 comprises a channel through which gas may flow to the agitator port 150. The agitator conduit 155 may be located on an external surface of the container unit 100 (e.g. opposite to the internal volume), as shown in Fig. 3. Alternatively, the agitator conduit 155 may be located inside the internal volume of the container unit 100. For example, the agitator conduit 155 may extend from the inlet tubing connector 144 towards a lower region of the internal volume. The agitator conduit 155 and port 150 are arranged to deliver gas to a lower region of the internal volume of the container unit 100. That is, the two are configured to supply a gas into the preservation liquid 110 in the container unit 100. The supplied gas delivered to the lower region of the preservation liquid 110 will bubble up through the preservation liquid 110, thereby inhibiting thermal stratification of that preservation liquid 110. The container unit 100 may be for a body tissue persufflation apparatus. In which case, the apparatus 1 (and thus container unit 100) are configured to circulate gaseous oxygen perfusate to the body tissue 10 in the container unit 100. The agitator conduit 155 may couple the agitator port 150 to the supply of gaseous oxygen perfusate forthe persufflation apparatus. For example, one or more conduits of the container unit 100 may be coupled to the gas store 240 (via the gas supply line) in the base unit 200. The agitator conduit 155 may be coupled to one of these said conduits for coupling to the supply of gas. In Fig. 3, this is shown via agitator connection 146. The agitator connection 146 is located downstream of the inlet connection 141 of the container unit 100 (which is for connecting to the base unit 200 to receive persufflation gas therefrom). In other words, the container unit 100 provides a gas channel (from the agitator connection 146, through the agitator conduit 155, and into the agitator port 150) arranged to provide persufflation gas to preservation liquid 110 in the container unit 100. This arrangement may enable at least some persufflation gas to be delivered to the preservation liquid 110 to distribute heat therein. This gas channel may be small relative to the other channels for carrying persufflation gas, thereby to limit the amount of gas which flows in through the agitator port 150, as the thermal stratification inhibition may occur with a relatively small amount of gas provided. Additionally, or alternatively, the agitator connection 146 may comprise a valve for limiting the amount of persufflation gas which is delivered through the agitator port 150. Persufflation gas delivery As with the container unit 100 of Fig. 2, the container unit 100 of Fig. 3 is configured to circulate gaseous oxygen perfusate to the body tissue 10 in the container unit 100. For this, the container unit 100 is configured to couple to a source of persufflation gas in the base unit 200, thereby to receive persufflation gas. The container unit 100 may also be configured to couple to the base unit 200 to provide discarded persufflation gas thereto. The inlet connection 141 of the container unit 100 is configured to couple to a source of persufflation gas in the base unit 200. For instance, the inlet connection 141 may be configured to couple to the gas supply line shown in Fig. 2. The inlet connection 141 is located external to the internal volume of the container unit 100. The humidifier 160 is coupled to the inlet connection 141. The humidifier 160 is located on an external wall of the container unit 100. Providing the humidifier 160 on the external wall may simplify manufacturing of the container unit 100, e.g. by enabling simpler moulding to be performed. The humidifier 160 comprises the humidifier inlet 162 and the humidifier outlet 164. The humidifier inlet 162 is coupled to the inlet connection 141. For example, a conduit may extend from the inlet connection 141 through to the humidifier inlet 162. The agitator connection 146 may be provided in said conduit. The humidifier 160 may be at least partially filled with a liquid, such as the preservation liquid 110 of the internal volume of the container unit 100 (the two volumes of preservation liquid 110 may be separate or connected in some way). The humidifier inlet 162 may be located in a lower region of the humidifier 160. The humidifier outlet 164 may be located in a higher region of the humidifier 160. A conduit may extend from the humidifier outlet 164 into the internal volume of the container unit 100. As shown in Fig. 3, a conduit which is coupled to the humidifier outlet 164 may be coupled to the inlet tubing connector 144. At which point, the conduit is coupled to tubing 142 which is to be connected to the body tissue 10, e.g. to the native vasculature thereof. Similarly, tubing 142 may extend from the body tissue 10, e.g. from the native vasculature thereof, to the outlet tubing connector 145, where that tubing 142 is connected to a separate conduit. That separate conduit may extend through to the outlet connection 143. The outlet connection 143 may be coupled to a component of the base unit 200 for discarding gas, e.g. to the gas receiving line 243 shown in the base unit 200 of Fig. 2. The inlet connection 141 is configured to receive gaseous oxygen perfusate from the base unit 200 (e.g. from the gas store 240). The container unit 100 is configured to provide humidification of this gas prior to delivery to the body tissue 10 in the container unit 100. For this, the gas is delivered from the inlet connection 141 into the preservation liquid in the humidifier 160 (via the humidifier inlet 162). The humidifier 160 is arranged for received persufflation gas to be bubbled through the preservation liquid. For example, the humidifier inlet 162 may be located in a lower portion of the humidifier 160. The humidifier outlet 164 is configured to receive humidified persufflation gas which has been bubbled through the preservation liquid in the humidifier 160. For example, the humidifier outlet 164 may be located in an upper portion of the humidifier 160. The container unit 100 is arranged to deliver humidified persufflation gas from the gas humidifier 160 to the body tissue 10 in the container unit 100. For this, one or more tubes may be configured to couple the humidifier outlet 164 to the body tissue 10, e.g. to the native vasculature of the body tissue 10. The inlet tubing connector 144 may be included to couple a conduit extending from the humidifier outlet 164 to tubing 142 which is to be coupled to the body tissue 10 (e.g. at least partially inserted into the native vasculature thereof). For example, this may be included where a different type of tubing 142 is used for contacting the body tissue 10. Similarly, tubing 142 may be provided which couples the body tissue 10 to the outlet connection 143 (e.g. via the outlet tubing connector 145). The outlet connection 143 is configured to couple to the base unit 200 (e.g. to the gas receiving line 243 in the base unit 200 shown in Fig. 2) for discarding gas thereto. In other words, the container unit 100 is arranged to provide two different gas flow paths. For both gas flow paths, gas is received from the base unit 200 through the inlet connection 141, and this may ultimately be returned to the base unit 200 via the outlet connection 143. For the first gas flow path, the gas is humidified in the humidifier 160 on the outside of the container unit 100 before being delivered to the body tissue 10. For the second gas flow path, the gas may be directed through the agitator conduit 155 and into the preservation liquid 110 through the agitator port 150. At least one conduit may be coupled to the outlet connection 143 which is for receiving gas in the container unit 100 (e.g. agitator gas) which has not travelled through the body tissue 10, e.g. to retain pressure levels within the internal volume of the container unit 100. Obstruction member The obstruction member 120 is included in the internal volume of the container unit 100. The obstruction member 120 may be a separate component to the container unit 100, e.g. it may be a component which is insertable into the internal volume of the container unit 100. The obstruction member 120 comprises one or more flanges 122. The flange(s) 122 extend radially around a perimeter of the obstruction member 120. The flange(s) 122 may be located at a lower region of the obstruction member 120. The obstruction member 120 comprises one or more walls which extend upwards from the flange(s) 122. The walls may extend towards a ceiling of the obstruction member 120 (at an upper region of the member). The wall(s) include one or more apertures. The obstruction member 120 is sized to fit within the internal volume of the container unit 100 and to surround the body tissue 10. The flange(s) 122 are arranged to contact the internal wall(s) of the container unit 100. The flange(s) 122 may be arranged to abut the internal wall(s) of the container unit 100 to hold the obstruction member 120 in a fixed position within the internal volume of the container unit 100. The apertures in the obstruction member 120 are configured to permit movement of liquid therethrough. In particular, the obstruction member 120 is arranged to permit movement of preservation liquid 110 through the apertures, e.g. as it sloshes about within the internal volume of the container unit 100. The obstruction member 120 is configured to surround the body tissue 10 within the internal volume of the container unit 100. The obstruction member 120 is configured to permit movement of preservation liquid 110 through the apertures, but to inhibit movement of the body tissue 10 therethrough. In other words, the obstruction member 120 is arranged to provide a constraining volume to limit the amount by which body tissue 10 may move within the container unit 100. The obstruction member 120 may be flexible and resilient. For example, the obstruction member 120 may be arranged to be securely inserted into the internal volume of the container unit 100 and to define an internal volume therewithin for limiting lateral movement of the body tissue 10 within the container unit 100. Advantageously, this arrangement may enable provide additional protection for the body tissue 10 within the container unit 100. In particular, any lateral movement of the body tissue 10, e.g. due to motion of the apparatus 1 as a whole (e.g. in transit), may be limited within the container unit 100. In turn, this may reduce the likelihood of impact-induced damage to the body tissue 10, as well as the likelihood of the movement of the body tissue 10 dislodging any tubing 142 coupled to the body tissue 10. Alternatives and variations It will be appreciated that the examples described above should not be considered limiting. Instead, the examples are just intended to demonstrate aspects of the technology. For example, in the examples described herein, the biological product to be preserved by the biological product preservation apparatuses is in the form of body tissue 10, such as a replacement organ. However, it will be appreciated that other forms of biological product may be preserved in apparatuses of the present disclosure. For example, the biological product could be different body tissue to a replacement organ, e.g. it may comprise artificial tissue. Alternatively, the biological product may comprise any of: drugs, vaccines, blood (or other body fluids). The biological product may comprise any product which may be used in a clinical scenario, e.g. for medical reasons such as facilitating treatment of a patient. As will be appreciated in the context of the present disclosure, preservation apparatuses disclosed herein may beneficially provide tightly controlled thermal management of a product within the container unit 100, and this thermal management may beneficially be employed to any suitable biological product. Likewise, while examples include delivery of persufflation gas to body tissue, this need not be considered limiting. No such fluid circulation may included and / or an alternative circulation such as liquid perfusate may be utilised. As another example, a particular thermal transfer path is shown in the figures for coupling the thermal energy store 210 to the container unit 100. For this, there may be both radiative and conductive thermal transfer, but it is to be appreciated that this need not be the case. For example, there may be no air gap 230 between the container unit receiving portion 227 and the container unit 100. Similarly, in examples described herein, one or more sensors may provide the sensor data to be used by the controller for determining how to operate the thermoelectric device 225. It is to be appreciated that any suitable sensor and / or sensor location may be used, e.g. to provide the relevant temperature data. For example, said sensor may be provided between the thermoelectric device 225 and the container unit 100. The sensor may be located closer to the container unit 100, e.g. in the container unit receiving portion 227 and / or the airgap 230. As will be appreciated the closer the proximity of the sensor to the container unit 100, the more reliable / accurate the correlation between the temperature sensed by that sensor and the temperature of the container unit 100 (and thus the product 10). Similarly, in examples described herein the material within the thermal energy store 210 has been described as ice. Likewise, the selected temperature range has generally been described as a relatively cool temperature range. However, neither should be considered limiting. Any suitable material may be used within the thermal energy store 210. For instance, the material may be selected to be a material which undergoes a phase change at a temperature relatively close to the selected temperature range for the container unit 100. For example, a phase change material may be utilised. As will be appreciated, any particular phase change may be utilised. Ice may be beneficial due to its relative abundance, but other materials could also be used. In examples described herein, the thermoelectric modulation device 225 may comprise a Peltier device. However, it is to be appreciated that alternative device may be used, and / or multiple Peltier devices may be used together in combination. As one example, the Peltier device may be provided by product DA-160-24-02 as manufactured and sold under the trademark of Laird Thermal Systems. Similarly, as described above, the controller 250 may be configured to control operation of the thermoelectric modulation device 225 based on data from one or more sensors of the apparatus 1. It will be appreciated that the particular types of sensor shown and their arrangement should not be considered limiting. For example, the sensors may be temperature sensors, but they could also sense other properties which are indicative of temperature. For example, for the thermal energy store 210, an indication of the proportion of melted ice may be determined using another type of sensor, e.g. an impedance sensor, a capacitance sensor or other sensor which is able to determine a difference between water and ice based on their respective properties (e.g. electrical properties). Likewise, while three sensors are shown in Fig. 2, there may be more or fewer sensors, and their respective locations may be different. For example, as will be appreciated, the controller 250 may be configured to determine an amount of melted water based on data obtained from any particular sensor location within the thermal energy store 210. It will be appreciated from the discussion above that the examples shown in the figures are merely exemplary, and include features which may be generalised, removed or replaced as described herein and as set out in the claims. With reference to the drawings in general, it will be appreciated that schematic functional block diagrams are used to indicate functionality of systems and apparatus described herein. In addition, the processing functionality may also be provided by devices which are supported by an electronic device. It will be appreciated however that the functionality need not be divided in this way, and should not be taken to imply any particular structure of hardware otherthan that described and claimed below. Thefunction of one or more of the elements shown in the drawings may be further subdivided, and / or distributed throughout apparatus of the disclosure. In some examples, the function of one or more elements shown in the drawings may be integrated into a single functional unit. As will be appreciated by the skilled reader in the context of the present disclosure, each of the examples described herein may be implemented in a variety of different ways. Any feature of any aspects of the disclosure may be combined with any of the other aspects of the disclosure. For example, method aspects may be combined with apparatus aspects, and features described with reference to the operation of particular elements of apparatus may be provided in methods which do not use those particular types of apparatus. In addition, each of the features of each of the examples is intended to be separable from the features which it is described in combination with, unless it is expressly stated that some otherfeature is essential to its operation. Each of these separable features may of course be combined with any of the other features of the examples in which it is described, or with any of the other features or combination of features of any of the other examples described herein. Furthermore, equivalents and modifications not described above may also be employed without departing from the invention. Certain features of the methods described herein may be implemented in hardware, and one or more functions of the apparatus may be implemented in method steps. It will also be appreciated in the context of the present disclosure that the methods described herein need not be performed in the order in which they are described, nor necessarily in the order in which they are depicted in the drawings. Accordingly, aspects of the disclosure which are described with reference to products or apparatus are also intended to be implemented as methods and vice versa. The methods described herein may be implemented in computer programs, or in hardware or in any combination thereof. Computer programs include software, middleware, firmware, and any combination thereof. Such programs may be provided as signals or network messages and may be recorded on computer readable media such as tangible computer readable media which may store the computer programs in non-transitory form. Hardware includes computers, handheld devices, programmable processors, general purpose processors, application specific integrated circuits (ASICs), field programmable gate arrays (FPGAs), and arrays of logic gates. Any controller described herein may be provided by any control apparatus such as a general-purpose processor configured with a computer program product to program the processor to operate according to any one of the methods described herein. The functionality of the controller may be provided by an application specific integrated circuit, ASIC, or by a field programmable gate array, FPGA, or by a configuration of logic gates, or by any other control apparatus. Other examples and variations of the disclosure will be apparent to the skilled addressee in the context of the present disclosure.

Claims

1. A biological product preservation apparatus comprising:a container unit for preserving a biological product;a thermal energy store;a thermoelectric modulation device, wherein the thermal energy store is thermally coupled to the container unit via the thermoelectric modulation device; anda controller configured to control operation of the thermoelectric modulation device to manage a temperature of a said biological product in the container unit.

2. The apparatus of claim 1, wherein the controller is configured to control operation of the thermoelectric modulation device based on at least one obtained indication of temperature.

3. The apparatus of claim 1 or 2, wherein the controller is configured to control operation of the thermoelectric modulation device to retain a temperature of the apparatus within a selected temperature range.

4. The apparatus of claim 3, wherein the temperature of the apparatus is indicative of a temperature of the container unit, optionally wherein said temperature is indicative of the biological product in the container unit.

5. The apparatus of any preceding claim, wherein the biologic product comprises body tissue.

6. The apparatus of any preceding claim, wherein the container unit is configured to preserve the biological product in preservation liquid.

7. The apparatus of claim 6 as dependent upon claim 5, wherein the apparatus comprises a fluid delivery system configured to circulate fluid to the body tissue in the container unit.

8. The apparatus of claim 7, wherein the fluid delivery system comprises a gas supply system configured to supply a gas to the body tissue in the container unit, optionally wherein the apparatus is a persufflation apparatus and said gas comprises a persufflation gas.

9. The apparatus of any preceding claim, wherein the controller is configured to control operation of the thermoelectric modulation device to manage the transfer of thermal energy between the thermal energy store and the container unit.

10. The apparatus of any preceding claim, wherein the controller is configured to: (i) receive an input signal indicative of a selected temperature range for the container unit and (ii) control operation of the thermoelectric modulation device based on the selected temperature range.

11. The apparatus of any preceding claim, wherein the thermal energy store is arranged to store a material to be used for managing the temperature of the container unit.

12. The apparatus of claim 11, wherein the apparatus is configured to permit replacement of said material in the thermal energy store, optionally wherein the thermal energy store is removable.

13. The apparatus of any preceding claim, wherein the thermal energy store is arranged to receive a phase change material, optionally wherein the phase change material comprises ice.

14. The apparatus of any preceding claim, wherein the controller is configured to control operation of the apparatus based on power usage of the thermoelectric modulation device.

15. The apparatus of any preceding claim, further comprising a base unit, and wherein the base unit comprises the thermal energy store, the thermoelectric modulation device and a container unit receiving portion arranged to receive the container unit.

16. The apparatus of claim 15, wherein at least one surface of the container unit receiving portion is coupled to the thermal energy store via the thermoelectric modulation device, optionally wherein said surface is coupled to the thermal energy store via at least one thermal conduit coupled to the thermoelectric modulation device.

17. The apparatus of claim 15 or claim 16, further comprising one or more sensors configured to obtain an indication of a temperature of at least one location on the thermal transfer path between the thermoelectric modulation device and the container unit receiving portion; andwherein the controller is configured to control operation of the apparatus based on said obtained indication of the temperature of the thermal transfer path.

18. The apparatus of any preceding claim, further comprising one or more sensorsconfigured to obtain an indication of a temperature of the thermal energy store; and wherein the controller is configured to control operation of the apparatus based on said obtained indication of temperature of the thermal energy store.

19. The apparatus of any preceding claim, further comprising one or more sensors configured to obtain an indication of ambient temperature; andwherein the controller is configured to control operation of the apparatus based on said obtained indication of ambient temperature.

20. The apparatus of any preceding claim, wherein the controller is configured to vary an amount of power available to the thermoelectric modulation device.

21. The apparatus of claim 20, wherein the controller is configured to permit the thermoelectric modulation device to use more power for cooling the container unit than for heating the container unit.

22. The apparatus of any preceding claim, wherein the controller is configured to control operation of the thermoelectric modulation device to adjust a temperature of the container unit in the event that an obtained temperature is outside a selected temperature range, optionally wherein the selected temperature range comprises a set temperature and a buffer region either side of the set temperature.

23. A base unit for a biological product preservation apparatus, the base unit comprising: a container unit receiving portion arranged to receive a container unit for preserving a biological product;a thermal energy store;a thermoelectric modulation device, wherein the thermal energy store is thermally coupled to the container unit receiving portion via the thermoelectric modulation device; anda controller configured to control operation of the thermoelectric modulation device to manage a temperature of a said biological product in a said container unit received in the container unit receiving portion.

24. A method of preserving a biological product, the method comprising:preserving the biological product in a container unit, wherein the container unit is thermally coupled to a thermal energy store via a thermoelectric modulation device; andcontrolling operation of the thermoelectric modulation device to manage a temperature of the biological product in the container unit.

25. A computer program product comprising computer program instructions configured to program a controller to control operation of a biological product preservation apparatus to implement the method of claim 24.s

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