Induction of heterogeneous ice nucleation for cryopreservation

Abstract

The present invention relates to the use of a platelet of at least one homopolymer and / or at least one copolymer for inducing ice nucleating in an aqueous liquid, wherein the homopolymer is selected from the group consisting of PCL, PHL, PVL, POL, PDDL, PFS, PLLA, PDHF, PC, and PPDO; and wherein the copolymer comprises first units from first monomers selected from the group consisting of CL, HL, VL, OL, DDL, FS, LLA, DHF, C and PDO and second units from second monomers selected from the group consisting of DMA, NAM, 4VP, 2VP, DMAEMA, qDMAEMA and AA, preferably wherein the platelet is formed by crystallization driven self- assembly (CDSA). The present invention further relates to a method of inducing ice nucleation in an aqueous liquid comprising the steps: a) providing a platelet as defined according to the invention; b) mixing the platelet of step a) with the aqueous liquid, preferably wherein the concentration of platelets in the aqueous liquid is between 0.1 and 10 mg / mL; c) cooling the aqueous liquid of step b), preferably at a rate of -1 degrees Celsius per minute, thereby inducing the ice nucleation; and d) optionally, further cooling aqueous liquid of step c) to a desired temperature and / or storing the aqueous liquid of step c). The present invention further relates to a cryopreserved sample, obtainable by the method according to the invention.

Description

[0001]Title: INDUCTION OF HETEROGENEOUS ICE NUCLEATION FOR CRYOPRESERVATION FIELD OF THE INVENTION The present invention relates to the use of a platelet of at least one homopolymer and / or at least one copolymer for inducing ice nucleating in an aqueous liquid, wherein the homopolymer is selected from the group consisting of PCL, PHL, PVL, POL, PDDL, PFS, PLLA, PDHF, PC, and PPDO; and wherein the copolymer comprises first units from first monomers selected from the group consisting of CL, HL, VL, OL, DDL, FS, LLA, DHF, C and PDO and second units from second monomers selected from the group consisting of DMA, NAM, 4VP, 2VP, DMAEMA, qDMAEMA and AA, preferably wherein the platelet is formed by crystallization driven self- assembly (CDSA). The present invention further relates to a method of inducing heterogeneous ice nucleation using the aforementioned platelets. Lastly, the present invention relates to a cryopreserved sample, obtainable by the method according to the invention. More in particular, the present invention relates to cryopreservation and / or improved storage of living cells, (therapeutic) reagents or compounds. BACKGROUND The background description includes information that may be useful in understanding the present invention. It is not an admission that any of the information provided herein is prior art or relevant to the presently claimed invention, or that any publication specifically or implicitly referenced is prior art. Cryopreservation is a vital technique that allows for the long-term storage of living materials such as living cells, therapeutic reagents or other compounds. However, in the process of cryopreservation, damage may occur due to the formation of ice crystals, i.e. due to ice nucleation. For example, when ice forms inside the cell, the expanding ice crystals can physically disrupt the cell membrane and internal structures, leading to cell rupture and death. Hence, preventing negative effects on any material due to the formation of ice crystals is crucial in cryopreservation. Ice nucleation is the process through which ice crystals form from water. When aqueous liquids are cooled down, ice is not directly formed when the temperature of the solution drops below the freezing point. This observation can be explained with classical nucleation theory that states that ice crystal formation introduces both a penalty for the interface free energy of the newly formed ice crystal while it also lowers the bulk free energy of the solution. Both components depend on the radius of the new formed crystal. For a small radius, the introduced penalty is larger than the gain in bulk free energy, and therefore a crystal will not be stable (and will dissolve again). For larger radius, the bulk free energy becomes the driving force and crystals will grow. Together, this results in a minimum critical nucleus size, and only when a crystal is formed that is larger than this critical size, ice can be formed. This critical radius is temperature dependent, with smaller critical sizes at lower temperatures. The formation of such a critical ice crystal depends on the likeliness that enough water molecules can assemble into a crystal, and is therefore depended on the number of water molecules in the sample (= volume of sample) and the time. The likeliness that enough water molecules assemble in an ice like structure in pure water close to the melting temperature is very low, and would require an almost infinite waiting time to observe. Because further cooling of the sample decreases the minimum critical size, it increases the chances to form an ice crystal large enough to be stable. From this surface, ice growth is possible and often results in a burst of ice growth to compensate the ice volume of the system. There are two main types of ice nucleation, namely homogenous ice nucleation and heterogeneous ice nucleation. Homogeneous ice nucleation occurs when water freezes without any impurities or foreign particles present and typically requires very low temperatures, e.g. below -38 degrees Celsius for pure water droplets (because the number of water molecules in a seed that exceeds the critical size is much smaller at lower temperatures, and therefore more likely to happen). More commonly found in nature is heterogeneous ice nucleation. This type of nucleation occurs when water freezes, e.g. on a surface of particles such as dust, pollen or other aerosols. These particles serve as nucleation sites that reduce the energy barrier required for ice formation. Due to the presence of such particles, i.e. nucleation sites, ice nucleation can occur at temperatures higher than observed for homogeneous ice nucleation, e.g. at around -15 degrees Celsius. One major issue that causes cell damage during cryopreservation is supercooling. Supercooling is the process of cooling a liquid below its freezing point without it becoming solid. While particles (in non-pure solutions) can act as ice nucleation sites that promote freezing, under certain conditions, even impure liquids can remain in a supercooled state. Since ice nucleation is a stochastic effect, this effect depends on both the sample volume (number of water molecules) and the cooling rate (time the sample is at a certain temperature). Therefore, it is more severe in smaller volumes and fast cooling rates, and can reach temperatures below -20 degrees Celsius before nucleation occurs and with a large spread in nucleation temperatures between samples of the same volume. When ice forms, this will lead to gradients in temperature and solute concentration in the aqueous liquid / solution. This is undesirable and might harm any material, e.g. cells, that are present in the aqueous liquid / solution. When freezing occurs closer to zero degrees Celsius, these gradients are usually less severe, the rate of ice growth is lower so that any cells have more time to adjust. Furthermore, it has been shown that the lower the temperature at which ice is formed, the more damage this does to cells in a sample. The ability to induce and control ice nucleation at a temperature closer to zero degrees Celsius has been shown to improve cell recovery, viability, and functionality, and a smaller spread of nucleation temperatures would decrease variation between the recovery, viability, and functionality of samples during cryopreservation. Hence, it is highly desirable to induce and control ice nucleation. The induction of ice nucleation can be achieved with different physical methods such as ice seeding, shock cooling, introduction of extremely cold objects, the use of ultrasound waves, or subjecting samples to electric and / or magnetic fields. Most of these physical methods are hindered by their poor effectiveness, require dedicated infrastructure, or are difficult to implement at scale. Alternatively, it is possible to control nucleation with the introduction of (chemical) ice nucleators which can be added to the cell medium formulations. Examples of ice nucleators are for example inorganic compounds such as Feldspar (KAlSi3O8), silver iodide, (washing water of) certain tree pollen, or the commercial bacterial protein extract Snomax® which is used as an additive for artificial snow production. However, for all these known nucleators there are concerns about reproducibility, toxicity, immunogenicity, and / or solubility, which hinder their use for cryopreservation of (living) cells. Accordingly, there is a need in the field to provide for an ice nucleating agent that may be used to induce and control ice nucleation, in particular in and around (living) cells, that does not have the drawbacks of the aforementioned ice nucleating agents. The technical problem underlying the present invention is therefore the provision of an ice nucleating agent that can fulfil such a need. STATEMENT OF THE INVENTION In a first aspect, the present invention relates to the use of a platelet of at least one homopolymer and / or at least one copolymer for inducing ice nucleating in an aqueous liquid, wherein the homopolymer is selected from the group consisting of PCL, PHL, PVL, POL, PDDL, PFS, PLLA, PDHF, PC, and PPDO; and wherein the copolymer comprises first units from first monomers selected from the group consisting of CL, HL, VL, OL, DDL, FS, LLA, DHF, C, PDO and second units from second monomers selected from the group consisting of DMA, NAM, 4VP, 2VP, DMAEMA, qDMAEMA and AA, preferably wherein the platelet is formed by crystallization driven self-assembly (CDSA). Highly advantageously, platelets according to the invention allow for the controlled induction of ice nucleation in an aqueous liquid. These result in nucleation at higher temperatures and at a narrower temperature range compared to the same aqueous liquid without such platelets. In a second aspect, the invention relates to a method of inducing ice nucleation in an aqueous liquid comprising the steps: a) providing a platelet as defined in accordance with the present invention; b) mixing the platelet of step a) with the aqueous liquid, preferably wherein the concentration of platelets in the aqueous liquid is between 0.1 and 10 mg / mL; c) cooling the aqueous liquid of step b), preferably at a rate of -1 degrees Celsius per minute, thereby inducing the ice nucleation; and d) optionally, further cooling aqueous liquid of step c) to a desired temperature and / or storing the aqueous liquid of step c). Advantageously, the platelets according to the invention can be reproducibly prepared and are non-toxic, making them versatile in their application. In a third aspect, the invention relates to a cryopreserved sample, obtainable by the method according to the invention, wherein the cryopreserved sample comprises a platelet according to the invention. Highly advantageously, the inventors realized that platelets according to the invention can prevent damage to components suspended therein, for example cells suspended in the aqueous liquid. Embodiments discussed below for the use are also applicable for the method according to the present invention and vice versa. DETAILED DESCRIPTION The present invention is elucidated below with a detailed description. When used in these specification and claims, the terms "comprises" and "comprising" and variations thereof mean that the specified features, steps or integers are included. The terms are not to be interpreted to exclude the presence of other features, steps, or components. DEFINITIONS The following definitions are used in the present description and claims to define the stated subject matter. Other terms not cited below are meant to have the generally accepted meaning in the field. When used in these specification and claims, the terms "comprises" and "comprising" and variations thereof mean that the specified features, steps or integers are included. The terms are not to be interpreted to exclude the presence of other features, steps, or components. The terms “about” and “approximately”, when referring to a measurable value such as an amount, a temporal duration, and the like, is meant to encompass variations of ±20% or ±10%, more preferably ±5%, even more preferably ±1% and still more preferably ±0.1% from the specified value, as such variations are appropriate to perform the disclosed methods. As used herein, the term “and / or” indicates that one or more of the stated cases may occur, alone or in combination with at least one of the stated cases, up to with all of the stated cases. “Platelet or platelets” as used in the present description refers to two-dimensional (2D) nanostructures. Two-dimensional refers to the geometric characteristics of the nanostructures where the structure extends significantly in two dimensions (length and width) but has a very limited extension in the third dimension (thickness). The use of the term platelet or platelets is independent of the shape thereof, a platelet may refer to any regular or irregular 2D shape such as, but not limited to hexagonal, rectangle, disc or leaf-like shapes. The platelets in accordance with the invention are known in the art and their morphology as well as obtainment is known and understood. “Unimer” as used in the present invention refers to a single, discrete polymer molecule, e.g. a (block) copolymer, before it assembles into larger structures, e.g. a platelet. The unimers can undergo self-assembly, e.g. CDSA, by interactions such as hydrophobicity, hydrogen bonding, or van der Waals forces to form organized nanoscale structures. “Seed” as used in the present invention refers to a small (i.e. smaller than the particle formed therefrom), pre-formed nucleus or initial cluster of polymers that acts as a template or starting point for further self-assembly. Seeds are used in processes like crystallization or self-assembly such as e.g. (living) CDSA, where they help to control the size, morphology, and uniformity of the resulting structures. “Multilayered platelet” as used in the present description refers to a platelet as defined above, i.e. a two-dimensional nanostructures, comprising two or more layers, wherein each layer is of different compositions. I.e. multilayered particles feature distinct, interconnected layers spread across the same plane rather than stacked vertically. Each layer may possess different properties or compositions. “Crystallization driven self-assembly (CDSA) and living CDSA” as used in the present description refer to a techniques used to create well-defined (nano)structures through the controlled aggregation of crystallizable (co)polymers or molecules. Living CDSA refers to a hierarchical assembly with predictable control of size and shape. “Block copolymer” as used in the present description refers to a class of polymers composed of two or more polymer blocks, or constituent units, covalently bonded together in repeating blocks. Block copolymers according to the invention may refer to any classification thereof, such as di- tri- or multiblock copolymers and may further comprise a non-repeating polymer block, also referred to as a junction block. For example, a PCL-b-PDMA block copolymers refer to the block polymer wherein at least one polymer block comprises PCL and a second polymer block comprises PDMA. “Ice nucleating” or “ice nucleation” as used in the present description refers the process by ice crystals form from water that is below it’s freezing temperature. In accordance with the invention ice nucleation refers to heterogeneous nucleation (formation of ice crystals on foreign particles or surfaces that serve as nucleation sites, e.g. the particles according to the invention). “Aqueous liquid” as used in the present description refers to any liquid that primarily or substantially comprises water and / or wherein water is a solvent. “Elongated hexagonal” as used in the present description refers to a geometric shape with six sides (hexagon) that is stretched or extended along one or more dimensions, typically resulting in a longer and narrower form compared to a regular hexagon. “Cryopreservation” as used in the present description refers to the process of preserving material such as nucleic acids, proteins, cells, tissues, organs at very low temperatures, usually, but not limited to below -80 degrees Celsius, to maintain their viability and functionality for future use. “ Temperature spread” as used in the present description refers to the range of temperatures between the temperature of the first freezing event and the lowest temperature of the last freezing event in a single experiment. Typically, a smaller temperature spread results in more similar samples. “Variation in cell viability” as used in the present description refers to differences in cell viability between different samples in a single experiment. For example, if 24 tubes with cells would be frozen in a single cryopreservation experiment, the percentage of viable cells can vary greatly between the different tubes. Typically, this variation in viability becomes smaller when the 24 samples freeze at more similar temperatures. BRIEF DESCRIPTION OF THE DRAWINGS The present invention is described hereinafter with reference to the accompanying drawings in which embodiments of the present invention are shown and in which like reference numbers indicate the same or similar elements. Figure 1 discloses A) The general assembly strategy applied to obtain ice nucleating platelets. Polymers are assembled into polydisperse cylinders that can be transformed into uniform seeds with sonication. By addition of polymers to these seeds under specific conditions different well defined platelets can be obtained. B) Schematic representation of the characteristics of platelets, in which their length, width, height and area are depicted. C) Schematic representation of the invention in which platelets acts as heterogenous ice nucleators. D) Schematic representation of a typic ice nucleation experiment in which an array of droplets of a defined volume are cooled with a fixed temperature ramp. By plotting the frozen fraction over temperature (see eq. 1) of samples with and without platelets, ice nucleating activity can be determined. Figure 2 discloses the ice nucleating activity of Platelet 1 (Fig.2A), Platelet 2 (Fig 2B), Platelet 3 (Fig 2C), Platelet 4 (Fig 2D) in water. DETAILED DESCRIPTION OF EMBODIMENTS In a first aspect, the present invention relates to the use of a platelet of at least one homopolymer and / or at least one copolymer for inducing ice nucleating in an aqueous liquid, wherein the homopolymer is selected from the group consisting of PCL, PHL, PVL, POL, PDDL, PFS, PLLA, PDHF, PC, PPDO; and wherein the copolymer comprises first units from first monomers selected from the group consisting of CL, HL, VL, OL, DDL, FS, LLA, DHF, C and PDO and second units from second monomers selected from the group consisting of DMA, NAM, 4VP, 2VP, DMAEMA, qDMAEMA and AA, preferably wherein the platelet is formed by crystallization driven self-assembly (CDSA). Examples of such particles have been described in i.a. Xia, T. et al., (J. Am. Chem. Soc.2023, 145 (46), 25274–25282). In a preferred embodiment, the platelets for use in accordance with the invention wherein the homopolymer is PCL and / or the copolymer comprises first units from CL as first monomer and seconds units from DMA as the second monomer (PCL-PDMA), preferably a platelet of PCL and PCL-PDMA. Hence, in an embodiment according to the first aspect of the invention, the platelets used to induce ice nucleation are of homopolymers and copolymers, or, of homopolymers or copolymers only. Examples of particles having only homopolymers or copolymers have been described respectively in i.a. Wan et al., (Macromolecules 2024, 57 (6), 2848-2857) and Inam et al., (Chem. Sci., 2017,8, 4223-4230). The description and embodiments described herein relate to platelets of homopolymers and copolymers combined, or, homopolyers or copolymers alone. More details are provided below. Platelets The present application relates to a novel use of platelets. Examples of the platelets used in the present invention and the fabrication thereof have been disclosed. Arno et al., (J. Am. Chem. Soc.2017, 139, 46, 16980–16985) describes the fabrication of biodegradable platelets made from poly(caprolactone)-b-poly(N,N-dimethylacrylamide) (PCL-b-PDMA) block copolymer via crystallization-driven self-assembly (CDSA). Further work by Xia, T. et al., (J. Am. Chem. Soc.2023, 145 (46), 25274–25282) and Xiao, L. et al., (ACS Macro Lett.2023, 12 (12), 1636–1641) describe the tuning of CSDA and scalability of the PCL-b-PDMA platelet production. In an embodiment, the present invention relates to the use of platelets according to the invention, wherein the platelet length is at least 280 nm, preferably at least 330 nm, more preferably at least 460 nm. The length of the platelets according to the invention is the longest length of such a platelet. It is hence understood that the distance perpendicular to said length is considered the width of the platelet. In a further embodiment, the length of the platelet is between 280 and 3700 nm, between 330 and 3700 nm, between 460 and 3700 nm, between 1850 and 3700 nm or between 2500 and 3700 nm. In addition to the length of the platelet, the platelet may be defined by the aspect ratio or area thereof. The aspect ratio of the platelet is the ratio between any two directions, preferably in two perpendicular directions such as the length and width. In an embodiment the aspect ratio of a platelet is between 1:1 and 1:100, between 1:1 and 1:50, between 1:1 and 1:25, between 1:1 and 1:10, between 1:1 and 1:5, or between 1:1 and 1:2, preferably 1:3, more preferably 2:5. Without being bound by any particular theory, the inventors believe that the longest distance perpendicular on the length, i.e. width, is crucial for the activity of the platelet in the context of ice nucleation. In another embodiment, the platelet is defined by the area thereof, in such embodiments the area of the platelet is at least 800 nm2, at least 8000 nm2, at least 80.000 nm2. In an embodiment the area of the platelet is between 800 and 1.000.000 nm2, between 8000 and 1.000.000 nm2, for example about 25.000 nm2, for example about 894.000 nm2. The inventors have found that platelets with a length of at least 280 nm, preferably at least 330 nm, more preferably at least 460 nm, effectively induce ice nucleation in an aqueous liquid. In an embodiment, it is preferred that the length of the platelets for use in accordance with the invention have a variation in length of between 10 to 180 nm, preferably 10 to 100 nm, more preferably 10 to 50 nm, most preferably 10 to 25 nm. With ‘variation’ is referred to the spread, dispersion, scatter and variability of a platelet. For example, platelets with a length of 460 nm may have a variation of 10 nm, i.e.450 to 470 nm. In a further embodiment, at least 50%, 75%, 80%, 90%, 95% or 99% of platelets for use in accordance with the invention have a variation in length that falls between 10 to 180 nm, preferably 10 to 100 nm, more preferably 10 to 50 nm, most preferably 10 to 25 nm. In yet a further embodiment, it is preferred that the length of the platelets for use in accordance with the invention have a variation of between 5 and 20 %, preferably between 5 and 15 %, of the length of the platelet. Hence, in an embodiment the mean platelet length and / or median platelet length is at least 280 nm, preferably at least 330 nm, more preferably at least 460 nm. In another embodiment, the length of the platelets for use in accordance with the invention is any size larger than the minimum size. For example, when platelets are used of at least 280 nm, the platelets may be any size of 280 nm and larger, for example 290 nm, 300 nm, 310 nm 320 nm or larger. The inventors belief that platelets having a mean or median length of at least 460 nm can optimally and efficiently induce ice nucleation in an aqueous liquid. In an embodiment, the platelet is in the shape of an hexagonal, preferably in the shape of an elongated hexagonal. It is understood that an hexagonal is a 2 dimensional (2D) shape having six sides. Elongated hexagonal as used in the present description refers to a geometric shape with six sides that is stretched or extended along one or more dimensions, typically resulting in a longer and narrower form compared to a regular hexagon. Preferably, the ratio between the length and width of the platelet is between 1:1 and 1:100, between 1:1 and 1:50, between 1:1 and 1:25, between 1:1 and 1:10, between 1:1 and 1:5, or between 1:1 and 1:2. Without being bound by theory, the inventors belief that hexagonal platelets, allow for efficient ice nucleation in an aqueous liquid. Furthermore, without being bound by theory, the inventors belief that the hexagonal shape, being a 2D hexagonal shape, i.e. a flat hexagonal shape, allows for efficient ice nucleation in an aqueous liquid. In an embodiment, the platelet has a thickness of between 5 and 25 nm. In an embodiment, the platelet has a thickness of between 5 and 25 nm, preferably between 10 and 20 nm. The thickness of the platelet refers to the length in the ‘third’ dimension of the platelets according to the invention, i.e. the direction in the z-axis if the length and width are considered the x-axis and y-axis. The thickness of the platelet depends on the polymer or block polymer chain length, longer polymer chains (i.e. unimers) tend to form thicker cores due to the greater number of monomers or blocks in the third dimension. Alternatively, the thickness of the platelet depends on post-modifications of the platelet surface. Hence, it is understood that depending on degree of polymerization and / or post-modifications of the polymer or block copolymer comprised in the platelet, the thickness thereof may be different. Furthermore, it is understood that the thickness does not need to be the uniform within a single platelet, or across the plurality of platelets. In an embodiment the variation of thickness across the platelets is 1 nm, 2 nm, 3 nm, 4 nm, 5 nm of 6 nm or more. It is further understood that, despite having a thickness of between 5 and 25 nm, the platelets according to the invention are considered 2 dimensional (2D) platelets. In an embodiment, the thickness of the platelet is a factor 5, 10, 15, 20, 30, 50, 100, times smaller compared to the length of the platelet. Polymers The platelets according to the present invention are formed from a homopolymer and / or a copolymer. Advantageously, the homopolymer is selected from poly(δ-valerolactone) (PVL), poly(ε-caprolactone) (PCL), poly(ζ-heptalactone) (PHL), poly(η-octalactone) (POL), poly-(λ- dodecanolactone) (PDDL), poly(p-dioxanone) (PPDO), poly(ferrocenyldimethylsilane) (PFS), poly(L-lactide) (PLLA), polycarbonates (PCs), poly(di-n-hexylfluorene) (PDHF), polycarbonate (PC) and / or poly(p-dioxanone) (PPDO). In a preferred embodiment, the homopolymer from which the platelets according to the invention are formed is selected from the group of lactones, preferably poly(δ-valerolactone) (PVL), poly(ε-caprolactone) (PCL), poly(ζ-heptalactone) (PHL), poly(η-octalactone) (POL), poly-(λ- dodecanolactone) (PDDL). The homopolymer is used as a unimer in the preparation of platelets according to the invention and can be used alone to prepare the platelets according to the invention, or in combination with a copolymer. The copolymer comprises first units from first monomers selected from the group consisting of δ-valerolactone (VL), ε-caprolactone (CL), ζ-heptalactone (HL), η-octalactone (OL), λ- dodecanolactone (DDL), p-dioxanone (PDO), ferrocenyldimethylsilane (FS), L-lactides (LLAs), carbonates (Cs), and / or di-n-hexylfluorene (DHF), preferably δ-valerolactone (VL), ε- caprolactone (CL), ζ-heptalactone (HL), η-octalactone (OL), λ- dodecanolactone (DDL), more preferably ε-caprolactone (CL). The copolymer further comprises second units from second monomers selected from the group consisting of dimethylacrylamide (DMA), N- acryloylmorpholine (NAM), 4-vinylpyridine (4VP), 2-vinylpyridine (2VP), 2- (dimethylamino)ethyl-methacrylate (DMAEMA), quarternized-(dimethylamino)ethyl- methacrylate (qDMAEMA) and acrylic-acid (AA), preferably dimethylacrylamide (DMA). Hence, in an embodiment the copolymers comprising first units from first monomers selected from the group consisting of CL, HL, VL, OL, DDL, FS, LLA, DHF, C, PDO and second units from second monomers selected from the group consisting of DMA, NAM, 4VP, 2VP, DMAEMA, qDMAEMA and AA are PCL-PDMA, PCL-PNAM, PCL-P4VP, PCL-P2VP, PCL-PDMAEMA, PCL-PqDMAEMA, PCL-PAA, PHL-PDMA, PHL-PNAM, PHL-P4VP, PHL-P2VP, PHL- PDMAEMA, PHL-PqDMAEMA, PHL-PAA, PVL-PDMA, PVL-PNAM, PVL-P4VP, PVL-P2VP, PVL-PDMAEMA, PVL-PqDMAEMA, PVL-PAA, POL-PDMA, POL-PNAM, POL-P4VP, POL- P2VP, POL-PDMAEMA, POL-PqDMAEMA, POL-PAA, PDDL-PDMA, PDDL-PNAM, PDDL- P4VP, PDDL-P2VP, PDDL-PDMAEMA, PDDL-PqDMAEMA, PDDL-PAA, PFS-PDMA, PFS- PNAM, PFS-P4VP, PFS-P2VP, PFS-PDMAEMA, PFS-PqDMAEMA, PFS-PAA, PLLA-PDMA, PLLA-PNAM, PLLA-P4VP, PLLA-P2VP, PLLA-PDMAEMA, PLLA-PqDMAEMA, PLLA-PAA, PDHF-PDMA, PDHF-PNAM, PDHF-P4VP, PDHF-P2VP, PDHF-PDMAEMA, PDHF- PqDMAEMA, PDHF-PAA, PC-PDMA, PC-PNAM, PC-P4VP, PC-P2VP, PC-PDMAEMA, PC- PqDMAEMA, PC-PAA, PPDO-PDMA, PPDO-PNAM, PPDO-P4VP, PPDO-P2VP, PPDO- PDMAEMA, PPDO-PqDMAEMA, PPDO-PAA. The copolymer is used as a unimer in the preparation of platelets according to the invention and can be used alone to prepare the platelets according to the invention, or in combination with a homopolymer. In a preferred embodiment, the homopolymer is PCL and / or the copolymer comprises first units from CL as first monomer and seconds units from DMA as the second monomer (PCL-PDMA), preferably a platelet of PCL and PCL-PDMA In an embodiment the copolymer from which the platelets according to the invention are formed is a block copolymer. Hence in such a preferred embodiment, the block copolymer is PCL-b- PDMA, PCL-b-PNAM, PCL-b-P4VP, PCL-b-P2VP, PCL-b-PDMAEMA, PCL-b-PqDMAEMA, PCL-b-PAA, PHL-b-PDMA, PHL-b-PNAM, PHL-b-P4VP, PHL-b-P2VP, PHL-b-PDMAEMA, PHL-b-PqDMAEMA, PHL-b-PAA, PVL-b-PDMA, PVL-b-PNAM, PVL-b-P4VP, PVL-b-P2VP, PVL-b-PDMAEMA, PVL-b-PqDMAEMA, PVL-b-PAA, POL-b-PDMA, POL-b-PNAM, POL-b- P4VP, POL-b-P2VP, POL-b-PDMAEMA, POL-b-PqDMAEMA, POL-b-PAA, PDDL-b-PDMA, PDDL-b-PNAM, PDDL-b-P4VP, PDDL-b-P2VP, PDDL-b-PDMAEMA, PDDL-b-PqDMAEMA, PDDL-b-PAA, PFS-b-PDMA, PFS-b-PNAM, PFS-b-P4VP, PFS-b-P2VP, PFS-b-PDMAEMA, PFS-b-PqDMAEMA, PFS-b-PAA, PLLA-b-PDMA, PLLA-b-PNAM, PLLA-b-P4VP, PLLA-b- P2VP, PLLA-b-PDMAEMA, PLLA-b-PqDMAEMA, PLLA-b-PAA, PDHF-b-PDMA, PDHF-b- PNAM, PDHF-b-P4VP, PDHF-b-P2VP, PDHF-b-PDMAEMA, PDHF-b-PqDMAEMA, PDHF-b- PAA, PC-b-PDMA, PC-b-PNAM, PC-b-P4VP, PC-b-P2VP, PC-b-PDMAEMA, PC-b- PqDMAEMA, PC-b-PAA, PPDO-b-PDMA, PPDO-b-PNAM, PPDO-b-P4VP, PPDO-b-P2VP, PPDO-b-PDMAEMA, PPDO-b-PqDMAEMA, PPDO-b-PAA, most preferably the block copolymer is PCL-b-PDMA. The block copolymer is i.a. used as a unimer in the preparation of platelets according to the invention and can be used alone to prepare the platelets according to the invention, or in combination with a homopolymer. In a further embodiment, the block copolymers as listed herein are used in (living) CDSA as the seed. In brief, the block copolymers are formed into polydisperse cylinders using CDSA, then sonication to obtain small crystalline seeds for further living CDSA to form the platelets according to the invention. The process is known in the art and described in i.a. Xia et al., (J. Am. Chem. Soc.2023, 145 (46), 25274-25282). Additionally, preparation of platelets in accordance with the invention is described in the examples below. In a preferred embodiment, poly(caprolactone) (PCL) is used as a homopolymer with the repeating unit derived from ε-caprolactone (C6H10O2) monomers. The Molecular Weight of PCL typically ranges from 5,000 to 100,000 g / mol, depending on the degree of polymerization. PCL is typically synthesized through ring-opening polymerization (ROP) of ε-caprolactone, using catalysts such as tin(II) octoate or other metal-based catalysts. The process allows for control over the polymer’s molecular weight and properties. It is understood that the skilled person is able to synthesize PCL, or, may obtain PCL through e.g. commercial vendors. In an embodiment wherein the block copolymer is prepared from PCL and a monomer selected from the group consisting of N,N-dimethylacrylamide (DMA), N-acryloylmorpholine (NAM), 4- vinylpyridine (4VP), 2-vinylpyridine (2VP), 2-(dimethylamino)ethyl-methacrylate (DMAEMA), quaternized (dimethylamino)ethyl methacrylate (qDMAEMA), poly(acrylic-acid) (PAA) and wherein the one or more caprolactone block copolymers are selected from poly(caprolactone)- b-poly(N,N-dimethylacrylamide) (PCL-b-PDMA), poly(caprolactone)-b-poly(N- acryloylmorpholine) (PCL-b-PNAM), poly(caprolactone)-b-poly(4-vinylpyridine) (PCL-b-P4VP), poly(caprolactone)-b-poly(2-vinylpyridine) (PCL-b-P2VP), poly(caprolactone)-b-poly(2- (dimethylamino)ethyl-methacrylate) (PCL-b-PDMAEMA), poly(caprolactone)-b- poly(quarternized-(dimethylamino)ethyl-methacrylate) (PCL-b-PqDMAEMA), poly(caprolactone)-b- poly(acrylic-acid) (PCL-b-PAA). The monomer is selected from the list of N,N-dimethylacrylamide (DMA), N-acryloylmorpholine (NAM), 4-vinylpyridine (4VP), 2-vinylpyridine (2VP), 2-(dimethylamino)ethyl-methacrylate (DMAEMA), quaternized dimethylaminoethyl methacrylate (qDMAEMA) and poly(acrylic-acid) (PAA) are common monomers used in the production of polymers and (block)copolymers. The skilled person is capable of synthesizing these monomers, or, is able to obtain them through e.g. commercial vendors. Preferably, the monomer N,N-dimethylacrylamide (DMA) is selected. The one or more block copolymers are selected from poly(caprolactone)-b-poly(N,N- dimethylacrylamide) (PCL-b-PDMA), poly(caprolactone)-b-poly(N-acryloylmorpholine) (PCL-b- PNAM), poly(caprolactone)-b-poly(4-vinylpyridine) (PCL-b-P4VP), poly(caprolactone)-b- poly(2-vinylpyridine) (PCL-b-P2VP), poly(caprolactone)-b-poly(2-(dimethylamino)ethyl- methacrylate) (PCL-b-PDMAEMA), poly(caprolactone)-b-poly(quarternized- (dimethylamino)ethyl-methacrylate) (PCL-b-PqDMAEMA), poly(caprolactone)-b-poly(acrylic- acid) (PCL-b-PAA) are caprolactone block copolymers. Preferably, poly(caprolactone)-b- poly(N,N-dimethylacrylamide) (PCL-b-PDMA) is selected. Highly advantageously, the platelets formed with the aforementioned block copolymers allow for induction of ice nucleation in aqueous liquid. The caprolactone block copolymers may be synthesized using a hydroxy-terminated dual-head reversible addition / fragmentation chain transfer (RAFT) agent, which could undergo ring- opening polymerization (ROP) followed by RAFT polymerization. RAFT agents are commonly known in the field, for example 2-Cyano-5-hydroxypentan-2-yl ethyl carbonotrithioate (CHPET) or 4-Cyano-4-(((ethylthio)carbonothioyl)thio)pentanoic acid (CEPA). Following known procedures such as those described in i.a. Arno et al., Xia et al,. and / or Xiao et al,. and described herein, the block copolymer may be used to form polydisperse cylinders via CDSA, then fragmented by known means, preferably by sonication, to obtain small crystalline seeds for further (living) CDSA, to form platelets according to the invention. In an embodiment, the mass average molar mass (MW) of poly(caprolactone) is between 1 kDa and 30 kDa, preferably between 2 kDa and 15 kDa and / or wherein the Mass average molar mass (MW) of the caprolactone block copolymer is between 2 kDa and 100 kDa, preferably between 7 kDa and 80 kDa. The mass average molar mass (MW) may also be referred to as weight average or weight average molecular weight. The skilled person is able to determine the MWof a polymer or block copolymer using methods known in the art such as using Size Exclusion Chromatography (SEC) / high-pressure liquid chromatography (HPLC), Light Scattering and / or Nuclear Magnetic Resonance (NMR). It is understood that the MWof a polymer depends on i.a. the weight of the individual monomer and the size of the polymer chain. The Mass average molar mass (MW) of a block copolymer is calculated by taking the weighted average of the molar masses of the individual blocks, considering their respective mass fractions. In a specific preferred embodiment, the polymer PCL51is used in accordance with the invention. The MWof PCL51is preferably 6070 Da. In another specific preferred embodiment the block copolymer PCL51-b-PDMA189is used in accordance with the invention, the MWof PCL51-b- PDMA189is preferably 24800 Da. The present inventors have observed that platelets formed with PCL51and PCL51-b-PDMA189are able to induce ice nucleation. In an embodiment, the weight ratio of the at least one homopolymer to the at least one copolymer of the platelet is between 1 to 10 and 10 to 1, most preferably 1 to 1. Hence, it is understood that the weight ratio of the homopolymer unimer to the copolymer unimer in the platelet is typically between 1:10 and 10:1, with a most preferred ratio of 1:1. Seeds, e.g. PCL- b-PDMA serve as nuclei for crystallization growth, but the contribution of the seed to the overall platelet area is minimal. Therefore, there is a difference between the seeds and the unimers (e.g. provided in a 1:1 weight ratio). The ratio by weight of unimer to seed is between 1 to 10 and 10 to 1, preferably 10 to 1. Without being bound by any particular theory, the inventors believe that this ratio does not significantly affect the function of the platelets, but it does influence the size of the platelets. Platelet production Platelets according to the present invention are preferably formed using crystallization driven self-assembly (CDSA). During CDSA, the crystalline regions of a material act as nucleation sites, guiding the assembly of additional molecules or particles. This results in the formation of uniform and often hierarchical structures such as fibers, rods, sheets or platelets. The process is driven by non-covalent interactions, including hydrogen bonding, van der Waals forces, and π-π stacking. CDSA is utilized in various applications, including nanotechnology, materials science, and drug delivery, due to its ability to produce precisely controlled and functionalized nanostructures. In an embodiment, living CDSA is used to prepare the platelets for use according to the invention. In living CDSA platelets are formed by using seed particles and this allows the platelet size to be well controlled. The use of CDSA to produce the platelets according to the invention as it allows the generation of platelets with uniform size, tunable dimensions, controllable shapes, and modifiable functionalities. These features make CDSA particularly suitable for a wide range of applications, from biomedical to electronic fields. In an embodiment, the platelets according to the invention may be formed by block copolymers (BCP) self-assembly. Typically, BCP self-assembly is achieved via direct dissolution, solvent- switch, and thin-film hydration methods. In an embodiment, the platelets according to the invention may be formed using polymerization- induced self-assembly (PISA). Most PISA processes are reversible-deactivation radical polymerizations (RDRP) or reversible addition-fragmentation chain-transfer polymerization (RAFT-PISA). PISA can be extended to all types of living polymerizations such as living anionic polymerization, ring-opening metathesis (ROMP), radical ring-opening copolymerization (rROP), and ring-opening polymerization (ROP). In an embodiment, PISA may be combined with CDSA, termed polymerization-induced crystallization-driven self-assembly (PI-CDSA) to form the platelets according to the invention. without being bound to any particular theory, PI-CDSA may be used to generate crystalline self- assemblies such as the platelets according to the invention in high concentrations (10–25% solids w / w). In an embodiment, the platelet may be formed by crystallization driven self-assembly (CDSA) of poly(caprolactone)a homopolymer and two or more copolymers thereby forming a multilayered platelet. “Multilayered platelet” as used in the present description refers to a platelet as defined above, i.e. a two-dimensional nanostructures, comprising two or more layers, wherein each layer is of different compositions. Thus, multilayered particles feature distinct, interconnected layers spread across the same (2D) plane rather than stacked vertically. Each layer may possess different properties or compositions. The inventors believe without being bound by any particular theory, that multilayered platelets further improve efficient induction of ice nucleation. In an embodiment, a multilayered particle is a particle wherein the two or more layers comprise (block co-)polymers selected from PCL, PHL, PVL, POL, PDDL, PFS, PLLA, PDHF, PC, PPDO, PCL-b-PDMA, PCL-b-PNAM, PCL-b-P4VP, PCL-b-P2VP, PCL-b-PDMAEMA, PCL-b- PqDMAEMA, PCL-b-PAA, PHL-b-PDMA, PHL-b-PNAM, PHL-b-P4VP, PHL-b-P2VP, PHL-b- PDMAEMA, PHL-b-PqDMAEMA, PHL-b-PAA, PVL-b-PDMA, PVL-b-PNAM, PVL-b-P4VP, PVL-b-P2VP, PVL-b-PDMAEMA, PVL-b-PqDMAEMA, PVL-b-PAA, POL-b-PDMA, POL-b- PNAM, POL-b-P4VP, POL-b-P2VP, POL-b-PDMAEMA, POL-b-PqDMAEMA, POL-b-PAA, PDDL-b-PDMA, PDDL-b-PNAM, PDDL-b-P4VP, PDDL-b-P2VP, PDDL-b-PDMAEMA, PDDL- b-PqDMAEMA, PDDL-b-PAA, PFS-b-PDMA, PFS-b-PNAM, PFS-b-P4VP, PFS-b-P2VP, PFS- b-PDMAEMA, PFS-b-PqDMAEMA, PFS-b-PAA, PLLA-b-PDMA, PLLA-b-PNAM, PLLA-b- P4VP, PLLA-b-P2VP, PLLA-b-PDMAEMA, PLLA-b-PqDMAEMA, PLLA-b-PAA, PDHF-b- PDMA, PDHF-b-PNAM, PDHF-b-P4VP, PDHF-b-P2VP, PDHF-b-PDMAEMA, PDHF-b- PqDMAEMA, PDHF-b-PAA, PC-b-PDMA, PC-b-PNAM, PC-b-P4VP, PC-b-P2VP, PC-b- PDMAEMA, PC-b-PqDMAEMA, PC-b-PAA, PPDO-b-PDMA, PPDO-b-PNAM, PPDO-b-P4VP, PPDO-b-P2VP, PPDO-b-PDMAEMA, PPDO-b-PqDMAEMA, and / or PPDO-b-PAA. Further features and uses described in the context of ‘single layered’ particles according to the invention also apply to the multilayered particle as described herein. The dimensions of the platelets during production thereof can be controlled by known means in the art and further described in the examples below. In brief, when forming platelets in accordance with a specific embodiment of the invention, crystalline seeds are combined with PCL polymers and one or more caprolactone block copolymers, wherein individual polymers may also be referred to as ‘polymer unimers’ or ‘unimers’. The dimensions of the platelets may be controlled various means such as by adjusting the unimer to seed ratio, varying the ratio of polymer to block copolymer and / or varying the flow rate of when combining seed and unimers. In an embodiment, the ratio of unimer to seed of the formed platelet is between 1 to 10 and 10 to 1, preferably 10 to 1. Without being bound by any particular theory, the inventors believe that this ratio does not significantly affect the function of the platelets, but it does influence the size of the platelets. In addition external conditions such as temperature, solvent, pH and / or unimer / seed concentration may be used to control platelet dimensions. Verifying the dimensions of the platelets may be performed by means common to the skilled person, such as obtaining an image of the platelets using Transmission Electron Microscopy (TEM) or Atomic Force Microscopy (AFM) and determining the dimensions based on said image. In an embodiment, the length of the platelets is at least 280 nm, preferably at least 330 nm, more preferably at least 460 nm. Aqueous liquid The use of platelets according to the present invention is for induction of ice nucleating in an aqueous liquid. Specifically, the invention relates to the use of a platelet of poly(caprolactone) (PCL) and one or more caprolactone block copolymers, for inducing ice nucleating in an aqueous liquid, preferably wherein the platelet is formed by crystallization driven self-assembly (CDSA) . In an embodiment, the invention relates to the use of the platelet, wherein the platelet has a concentration of between 0.1 and 10 mg / mL when mixed with the aqueous liquid. Without being limited by any particular theory, the inventors believe that the higher the concentration of platelets in the aqueous liquid, the higher the temperature at which ice nucleation can be induced. It is understood that, with the highest concentration is meant the concentration at which platelets can be dissolved, suspended, mixed or else in the aqueous liquid without precipitating, or, with the highest concentration is meant the concentration of the platelets without it influencing other constituents in the aqueous liquid. It is further understood that, depending on the particle size, the particles can be dissolved, suspended or mixed in the aqueous liquid at different maximum concentrations. Hence, in an embodiment, the platelet has a concentration of between 0.1 and 100 mg / mL, between 1 and 100 mg / mL, between 10 and 100 mg / mL, between 25 and 100 mg / mL when mixed with the aqueous liquid. In an embodiment, the invention relates to the use of the platelet for inducing ice nucleating in an aqueous liquid, wherein the aqueous liquid has a volume of between 0.4 nL and 5000 µL, preferably between 0.4 nL and 1000 µL. The inventors have observed that, when inducing ice nucleation in aqueous liquids of this volume, e.g. in droplets, microplates, cryovials or cryostraws, the particles efficiently induce ice nucleation. In an embodiment, ice nucleation is induced in larger volumes comprising the platelets according to the invention, such as volumes between 5 mL to 5000 mL, between 5 mL and 2500 mL or between 5 mL and 500 mL. In particular such larger volumes are useful for cryopreservation of e.g. blood stem cells in cryobags. Hence, the platelets according to the invention may be used to induce ice nucleation in a large range of volumes. In an embodiment, the aqueous liquid further comprises cells, preferably living cells, polynucleotides, oligonucleotides, DNA, mRNA, ssRNA, lipids, and / or proteins or fragments thereof. Ice nucleation occurs at a wide range of temperatures, or, may occur rapidly at temperatures well below the equilibrium melting temperature of an aqueous liquid in absence of particles according to the invention. This uncontrolled ice nucleation may cause damage to cells, DNA or RNA molecules, lipid layers, or proteins and fragments thereof. The inventors have observed that when using particles according to the invention, ice nucleation occurs ate a narrow(er) range and at temperatures closer to zero degrees Celsius and under controlled conditions and dynamics. Hence, by controlling the ice nucleation conditions and dynamics, the inventors belief that using the particles in a aqueous liquid comprising one or more of the above-mentioned components, damage thereto will be mitigated or substantially reduced. Hence, in a further embodiment, the invention relates to the use of the platelet according to the invention in cryopreservation, preferably cryopreservation of cells, preferably living cells, polynucleotides, oligonucleotides, DNA, mRNA, ssRNA, lipids, and / or proteins or fragments thereof. For example, mRNA vaccines typically require ultra cold storage throughout production, storage, transport and final administration of a vaccine, i.e. the cold chain. The COVID-19 pandemic has demonstrated that cryopreservation is imperative to afford an effective cold chain for vaccine storage and delivery, particularly for vaccines requiring ultralow- temperature storage, such as those based on mRNA technology. However, cold storage and / or the cold chain can induce damage with the carrier particles, e.g. liposomes, that stabilize the mRNA and / or assist the mRNA to enter a cell. Without being bound by any particular theory, the inventors belief that because of the controlled ice nucleation using the particles according to the invention, the particles can be used in cold storage of, for example, vaccines, such as RNA, DNA, liposomal, and / or protein vaccines. In an embodiment, the invention relates to the use of the platelet according to the invention, wherein the aqueous liquid comprises one or more selected from the list of culture medium such as basal medium, serum-free medium, chemically defined medium; growth serums such as BSA, FBS or HAS; cryoprotectants such as DMSO, glycerol, glycol; and / or buffers such as HEPES or PBS, or any component thereof. Hence, in such an embodiment, the aqueous liquid is not merely consisting of water. The inventors have found that, even in the presence of such further components in the aqueous liquid, ice nucleation is efficiently induced when using the platelets according to the invention. Use for inducing ice nucleation In a first aspect, the invention relates to a use of a platelet of at least one homopolymer and / or at least one copolymer for inducing ice nucleating in an aqueous liquid, wherein the homopolymer is selected from the group consisting PCL, PHL, PVL, POL, PDDL, PFS, PLLA, PDHF, PC, and PPDO; and wherein the copolymer comprises first units from first monomers selected from the group consisting of CL, HL, VL, OL, DDL, FS, LLA, DHF, C and PDO and second units from second monomers selected from the group consisting of DMA, NAM, 4VP, 2VP, DMAEMA, qDMAEMA and AA, preferably wherein the platelet is formed by crystallization driven self-assembly (CDSA). Highly advantageously, such platelets thus allow for the controlled induction of ice nucleation in an aqueous liquid, thereby preventing damaging e.g. cells when storing (i.e. cryopreserving) such cells in a freezer. In an embodiment, the invention relates to the use of the platelet according to the invention, wherein the ice nucleating in the aqueous liquid is induced at a temperature -15 degrees Celsius or lower, preferably -10 degrees Celsius or lower, more preferably -5 degrees Celsius or lower, most preferably 0 degrees Celsius or lower. The ice nucleation temperature is measured according to the ice nucleation experiments as described in the Example section below. Briefly, with the ice nucleating temperature of -15 degrees Celsius it is meant that, at - 15 degrees Celsius, 50% of the aqueous liquid droplets in the experiment are frozen. The authors have observed that, at higher concentrations of the platelets in the aqueous liquid, the temperature at which ice nucleation is observed increases. Hence, ice nucleating in the aqueous liquid is induced at a temperature below -15 degrees Celsius, preferably below -10 degrees Celsius, more preferably below -5 degrees Celsius, most preferably below 0 degrees Celsius. Furthermore, the inventors have observed that when comparing ice nucleation experiments in samples with and without platelets, ice nucleating is induced at significantly higher temperatures in the samples comprising the platelets. Hence, in a further embodiment, the invention relates to the use of the platelet according to the invention, wherein the temperature at which ice nucleation occurs in an aqueous liquid comprising the platelet is increased by at least 10%, at least 20%, at least 30%, at least 50%, or, between 10% and 50%, between 10% and 100%, compared to an aqueous liquid without the platelet. For example, and as further demonstrated in the example section below, 0.6 μL Milli-Q water droplets freeze at -27.3 degrees Celsius when cooled with a 1°C min-1ramp.0.6 μL droplets comprising 0.5 mg / mL of platelet 3 freeze at -19.0 degrees Celsius when cooled with the same speed. Hence, the delta (difference) in ice nucleation temperature is 8.3 degrees Celsius corresponding to a 30% increase in temperature at which ice nucleation occurs in an aqueous liquid comprising the platelet. In an embodiment, the temperature spread at which ice nucleation occurs in an aqueous liquid comprising the platelet is decreased by at least 10%, at least 20%, at least 30%, at least 50% or at least 75% compared to an aqueous liquid without the platelet. For example, in 0.6 µL droplets of Milli-Q water, ice nucleation occurs at a temperature of between -19.3 and -32.0 degrees Celsius in an aqueous liquid without particles, i.e. having a spread of 12.7 degrees Celsius. In Milli-Q water comprising the particles according to the invention ice nucleation occurs at a temperature of between -15.5 and -21.8 degrees Celsius in an aqueous liquid without particles, i.e. having a spread of 6.3 degrees Celsius. Hence, the delta (difference) in spread of the ice nucleation temperature is 6.3 degrees Celsius corresponding to a 50% decrease in spread at which ice nucleation occurs in an aqueous liquid. Without being bound by any particular theory, the inventors believe that a reduced spread decreases the variation in viability and recovery of e.g. cells in the aqueous liquid after cryopreservation between different samples, i.e. after the cryopreserved sample has been thawed. In an embodiment, the variation in cell viability is improved by at least 10%, at least 20%, at least 30%, at least 50% or at least 75% compared to an aqueous liquid without the platelet. Without being bound by any particular theory, the inventors believe that freezing e.g. one or more samples comprising cells and the platelets according to the invention, results in more cells, i.e. a higher recovery of cells, after thawing of the sample. Without being bound by any particular theory, the inventors believe that freezing e.g. one or more samples comprising cells and the platelets according to the invention, results in more living cells, i.e. a higher viability of cells, after thawing of the sample. Hence, cell recovery refers to the number of cells after cryopreservation. Cell viability refers to the viability of the cells after cryopreservation. For example freezing 100.000 cells comprising platelets according to the invention results in 77.000 cells after thawing. Freezing 100.000 cells without platelets according to the invention results in 70.000 cells after thawing. Thus, cell recovery is improved by 10%. For example freezing 100.000 cells comprising platelets according to the invention results in 55.000 viable cells after thawing. Freezing 100.000 cells without platelets according to the invention results in 50.000 viable cells after thawing. Thus, cell viability is improved by 10%. Furthermore, in an embodiment the temperature spread at which ice nucleation occurs in a set of samples with aqueous liquid comprising the platelets is decreased by at least 10%, at least 20%, at least 30%, at least 50% or at least 75% compared to a set of aqueous liquids without the platelets, the variation in cell viability between samples is more consistent by at least 10%, at least 20%, at least 30%, at least 50% or at least 75% compared to the variation in cell viability between samples that contain an aqueous liquid without the platelets. Without being bound by any particular theory, the inventors believe that reducing the temperature spread at which nucleation occurs, leads to more consistent viability in similar samples. It is understood in the present embodiment, that the average ice nucleation temperature may not be increased by the addition of particles according to the invention. Having more similar cell viabilities in similar samples may be highly advantageous when thawed samples need to be highly similar (e.g. when used for screening applications) In an embodiment, the temperature at which ice nucleation occurs in an aqueous liquid comprising the platelet is increased by at least 10%, at least 20%, at least 25%, or, between 10% and 60%, between 15% and 45%, between 20% and 50% for aqueous liquids having a volume of at least 0.1 μL. In an embodiment, the temperature at which ice nucleation occurs in an aqueous liquid comprising the platelet is increased by at least 10%, at least 20%, at least 25%, or, between 10% and 60%, between 15% and 45%, between 20% and 50% for aqueous liquids having a volume of at least 1 μL. In an embodiment, the temperature at which ice nucleation occurs in an aqueous liquid comprising the platelet is increased by at least 10%, at least 20%, at least 25%, or, between 10% and 60%, between 15% and 45%, between 20% and 50% for aqueous liquids having a volume of at least 10 μL. In an embodiment, the temperature at which ice nucleation occurs in an aqueous liquid comprising the platelet is increased by at least 10%, at least 20%, at least 25%, or, between 10% and 60%, between 15% and 45%, between 20% and 50% for aqueous liquids having a volume of at least 100 μL. In an embodiment, the temperature at which ice nucleation occurs in an aqueous liquid comprising the platelet is increased by at least 10%, at least 20%, at least 25%, or, between 10% and 60%, between 15% and 45%, between 20% and 50% for aqueous liquids having a volume of at least 1000 μL. In an embodiment, the temperature at which ice nucleation occurs in an aqueous liquid comprising the platelet is increased by at least 10%, at least 20%, at least 25%, or, between 10% and 60%, between 15% and 45%, between 20% and 50% for aqueous liquids having a volume of at least 5000 μL or more. Method of inducing ice nucleation The present invention also relates to a method of inducing ice nucleating using the platelets as discussed above. In a second aspect, the invention relates to method of inducing ice nucleation in an aqueous liquid comprising the steps: a) providing a platelet as defined in the present invention; b) mixing the platelet of step a) with the aqueous liquid, preferably wherein the concentration of platelets in the aqueous liquid is between 0.1 and 10 mg / mL; c) cooling the aqueous liquid of step b), preferably at a rate of -1 degrees Celsius per minute, thereby inducing the ice nucleation; and d) optionally, further cooling aqueous liquid of step c) to a desired temperature and / or storing the aqueous liquid of step c). In step a) of the method according to the invention a platelet according to the invention is provided. The skilled person is well capable to make the platelets in accordance with known methods and as described in the present invention. In a preferred embodiment, the platelets are formed of poly(caprolactone) (PCL) and at least one caprolactone block copolymer, for example PCL-b-PDMA, PCL-b-PNAM, PCL-b-P4VP, PCL-b-P2VP, PCL-b-PDMAEMA, PCL-b-PqDMAEMA, PCL-b-PAA. In another embodiment the platelet is formed of the homopolymer selected from poly(δ- valerolactone) (PVL), poly(ε-caprolactone) (PCL), poly(ζ-heptalactone) (PHL), , poly(η- octalactone) (POL), poly-(λ- dodecanolactone) (PDDL), poly(p-dioxanone) (PPDO), poly(ferrocenyldimethylsilane) (PFS), poly(L-lactide) (PLLA), polycarbonates (PCs), and / or poly(di-n-hexylfluorene) (PDHF). The copolymer comprises first units from first monomers selected from the group consisting of δ-valerolactone (VL), ε-caprolactone (CL), ζ-heptalactone (HL), η-octalactone (OL), λ- dodecanolactone (DDL), ferrocenyldimethylsilane (FS), L-lactides (LLAs), carbonates (Cs), p- dioxanone (PDO) and / or di-n-hexylfluorene (DHF) polycarbonate (PC) and / or poly(p- dioxanone) (PPDO), preferably δ-valerolactone (VL), ε-caprolactone (CL), ζ-heptalactone (HL), η-octalactone (OL), λ- dodecanolactone (DDL), more preferably ε-caprolactone (CL). The copolymer further comprises second units from second monomers selected from the group consisting of dimethylacrylamide (DMA), N-acryloylmorpholine (NAM), 4-vinylpyridine (4VP), 2-vinylpyridine (2VP), 2-(dimethylamino)ethyl-methacrylate (DMAEMA), quarterinzed- (dimethylamino)ethyl-methacrylate (qDMAEMA) and acrylic-acid (AA), preferably dimethylacrylamide (DMA). Hence, in an embodiment the copolymers comprising first units from first monomers selected from the group consisting of CL, HL, VL, OL, DDL, FS, LLA, DHF, C and PDO and second units from second monomers selected from the group consisting of DMA, NAM, 4VP, 2VP, DMAEMA, qDMAEMA and AA are PCL-PDMA, PCL-PNAM, PCL-P4VP, PCL-P2VP, PCL-PDMAEMA, PCL-PqDMAEMA, PCL-PAA, PHL-PDMA, PHL-PNAM, PHL-P4VP, PHL-P2VP, PHL- PDMAEMA, PHL-PqDMAEMA, PHL-PAA, PVL-PDMA, PVL-PNAM, PVL-P4VP, PVL-P2VP, PVL-PDMAEMA, PVL-PqDMAEMA, PVL-PAA, POL-PDMA, POL-PNAM, POL-P4VP, POL- P2VP, POL-PDMAEMA, POL-PqDMAEMA, POL-PAA, PDDL-PDMA, PDDL-PNAM, PDDL- P4VP, PDDL-P2VP, PDDL-PDMAEMA, PDDL-PqDMAEMA, PDDL-PAA, PFS-PDMA, PFS- PNAM, PFS-P4VP, PFS-P2VP, PFS-PDMAEMA, PFS-PqDMAEMA, PFS-PAA, PLLA-PDMA, PLLA-PNAM, PLLA-P4VP, PLLA-P2VP, PLLA-PDMAEMA, PLLA-PqDMAEMA, PLLA-PAA, PDHF-PDMA, PDHF-PNAM, PDHF-P4VP, PDHF-P2VP, PDHF-PDMAEMA, PDHF- PqDMAEMA, PDHF-PAA, PC-PDMA, PC-PNAM, PC-P4VP, PC-P2VP, PC-PDMAEMA, PC- PqDMAEMA, PC-PAA, PPDO-PDMA, PPDO-PNAM, PPDO-P4VP, PPDO-P2VP, PPDO- PDMAEMA, PPDO-PqDMAEMA, PPDO-PAA. The copolymer is used as a unimer in the preparation of platelets according to the invention and can be used alone to prepare the platelets according to the invention, or in combination with a homopolymer. In an embodiment the copolymer from which the platelets according to the invention are formed is a block copolymer. Hence in such a preferred embodiment, the block copolymer is PCL-b- PDMA, PCL-b-PNAM, PCL-b-P4VP, PCL-b-P2VP, PCL-b-PDMAEMA, PCL-b-PqDMAEMA, PCL-b-PAA, PHL-b-PDMA, PHL-b-PNAM, PHL-b-P4VP, PHL-b-P2VP, PHL-b-PDMAEMA, PHL-b-PqDMAEMA, PHL-b-PAA, PVL-b-PDMA, PVL-b-PNAM, PVL-b-P4VP, PVL-b-P2VP, PVL-b-PDMAEMA, PVL-b-PqDMAEMA, PVL-b-PAA, POL-b-PDMA, POL-b-PNAM, POL-b- P4VP, POL-b-P2VP, POL-b-PDMAEMA, POL-b-PqDMAEMA, POL-b-PAA, PDDL-b-PDMA, PDDL-b-PNAM, PDDL-b-P4VP, PDDL-b-P2VP, PDDL-b-PDMAEMA, PDDL-b-PqDMAEMA, PDDL-b-PAA, PFS-b-PDMA, PFS-b-PNAM, PFS-b-P4VP, PFS-b-P2VP, PFS-b-PDMAEMA, PFS-b-PqDMAEMA, PFS-b-PAA, PLLA-b-PDMA, PLLA-b-PNAM, PLLA-b-P4VP, PLLA-b- P2VP, PLLA-b-PDMAEMA, PLLA-b-PqDMAEMA, PLLA-b-PAA, PDHF-b-PDMA, PDHF-b- PNAM, PDHF-b-P4VP, PDHF-b-P2VP, PDHF-b-PDMAEMA, PDHF-b-PqDMAEMA, PDHF-b- PAA, PC-b-PDMA, PC-b-PNAM, PC-b-P4VP, PC-b-P2VP, PC-b-PDMAEMA, PC-b- PqDMAEMA, PC-b-PAA, PPDO-b-PDMA, PPDO-b-PNAM, PPDO-b-P4VP, PPDO-b-P2VP, PPDO-b-PDMAEMA, PPDO-b-PqDMAEMA, PPDO-b-PAA, most preferably the block copolymer is PCL-b-PDMA. The platelets may be provided in any form suitable for mixing in subsequent step b). Hence, in an embodiment, the platelets are provided as a dry composition or as a liquid composition. In a further embodiment, the dry composition comprising the platelets is obtained by dehydration, spray-drying, freeze-drying or the like. In yet a further embodiment, the liquid composition comprising the platelets is a liquid composition directly for use in subsequent step, or, is a concentrated liquid composition. In embodiments wherein the platelets are provided as a dry composition or liquid composition, the composition may further comprise additives such as stabilizers, buffers, preservatives and the like. In step b) of the method according to the invention, the platelet of step a) is mixed with an aqueous liquid, preferably wherein the concentration of platelets in the aqueous liquid is between 0.1 and 10 mg / mL. In accordance with embodiments described in the present invention and without being limited by any particular theory, the inventors believe that the higher the concentration of platelets in the aqueous liquid, the higher the temperature at which ice nucleation can be induced. Hence, in an embodiment, the platelet has a concentration of between 0.1 and 100 mg / mL, between 1 and 100 mg / mL, between 10 and 100 mg / mL, between 25 and 100 mg / mL when mixed with the aqueous liquid. In an embodiment, the aqueous liquid further comprises cells, preferably living cells, polynucleotides, oligonucleotides, DNA, mRNA, ssRNA, lipids, and / or proteins or fragments thereof. In a further embodiment, the aqueous liquid further comprises one or more selected from the list of culture medium such as basal medium, serum-free medium, chemically defined medium; growth serums such as BSA, FBS or HAS; cryoprotectants such as DMSO, glycerol, glycol; and / or buffers such as HEPES or PBS, or any component thereof In step c) of the method according to the invention, the aqueous liquid of step b) is cooled, preferably at a rate of -1 degrees Celsius per minute, thereby inducing ice nucleation. It is understood that a cooling rate of -1 degrees Celsius per minute means that each minute the aqueous liquid has a temperature that is 1 degree Celsius less compared to a minute before. It is further understood that cooling the aqueous liquid in step c) results in solidification, i.e. freezing, thereof. Hence, the aqueous liquid after cooling in step c) is in a solid (frozen) state, liquid state, or a combination thereof. Preferably, the cooling of step c) results in fully freezing the aqueous solution. In an embodiment, the cooling rate during step c) according to the method of the present invention is -1, -2, -3, -4, -5, -6, -7, -8, -9 -10, or more degrees Celsius per minute. In an embodiment, the cooling rate is any cooling rate such that ice nucleation in the aqueous liquid occurs, hence, in an embodiment it is preferred that no vitrification of the aqueous liquid occurs. Vitrification is the process of transforming a liquid into a glass-like, amorphous solid state without forming crystalline structures. In step d), which is an optional step, of the method according to the invention involves further cooling the aqueous liquid to a desired temperature and / or storing the aqueous liquid of step c). In accordance with the result of cooling in step c) the aqueous liquid in step c) may be solid (frozen) state, liquid state, or a combination thereof. Further cooling in step d) may result in further solidification of the aqueous liquid in step c) to obtain a solid (frozen) state, liquid state, or a combination thereof. Preferably, the further cooling of step d) results in fully freezing the aqueous solution. In an embodiment the cooled solution of step c) is further cooled to a temperature of at least - 20 degrees Celsius, at least -40 degrees Celsius, at least -80 degrees Celsius, at least -120 degrees Celsius, or at least -196 degrees Celsius. It is understood that the storing of the solution in optional step d) means the cryopreservation of the aqueous liquid. In an embodiment, the storing of optional step d) is for a period of at least 1 day, at least 1 week, at least 1 month, at least 1 year, at least 10 years or more. Without being bound by any particular theory, the inventors believe that the presence of the particles according to the invention improve (i.e. extend) the period for which the aqueous liquid can be stored. Cryopreserved sample The invention relates to a cryopreserved sample, obtainable by the method according to the method described herein, wherein the cryopreserved sample comprises a platelet according to the present invention. The cryopreserved sample is a frozen sample. In an embodiment, the cryopreserved sample further comprises cells, preferably living cells, polynucleotides, oligonucleotides, DNA, mRNA, ssRNA, lipids, and / or proteins or fragments thereof. In a further embodiment, the cryopreserved sample further comprises one or more selected from the list of culture medium such as basal medium, serum-free medium, chemically defined medium; growth serums such as BSA, FBS or HAS; cryoprotectants such as DMSO, glycerol, glycol; and / or buffers such as HEPES or PBS, or any component thereof. Other variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claim. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measured cannot be used to advantage. The scope of the present invention is defined by the appended claims. One or more of the objects of the invention are achieved by the appended claims. EXAMPLES The present invention is further elucidated based on the Examples below which are illustrative only and not considered limiting to the present invention. MATERIALS All chemicals and solvents were used as obtained without further purification unless otherwise stated. Sodium ethanethiolate (90%), carbon disulfide (≥99%), solid iodine (≥99%), 4,4’- azobis(4-cyanovaleric acid) (ACVA, 98%), borane tetrahydrofuran complex solution (1.0 M in THF), tris(hydroxymethyl)aminomethane (Tris), trichloro(1H,1H,2H,2H-perfluorooctyl)silane and iodomethane were purchased from Sigma Aldrich / Merck or Alfa Aesar. 4-cyano-4- [(ethylsulfanylthiocarbonyl)sulfanyl] pentanoic acid (CTA) and diphenylphosphate (DPP, 99%, Sigma Aldrich) were dried over P2O5in desiccator under static vacuum for 1 week before use. ɛ-caprolactone (99%, ACROS Organics) were vacuum distilled twice over CaH2before being introduced in the glovebox and used. 2,2'-azobis(2-methylpropionitrile) (AIBN, 98%, Sigma Aldrich) was recrystallized twice from methanol and stored at 4 °C in the dark. 1,4-dioxane (anhydrous, 99.8%), N,N-dimethyl acrylamide (DMA, 99%, contains 500 ppm monomethyl ether hydroquinone as inhibitor), were purchased from Sigma Aldrich or Fisher, and passed through a basic alumina plug immediately to remove stabilizer before use. Sylgard® 184 (DOW Corning) polydimethylsiloxane (PDMS) elastomer kit was purchased from Darwin microfluidics. HFE-7500 (3M, Novec Engineered Fluid), and HFE-7100 (3M, Novec Engineered Fluid) were purchased from Fluorochem. PFPE-Tris was synthesized according to previous literature using PFPE-COOH (Krytox 157FSH, ~7410 g / mol, purchased from Lub Service GmbH) as starting material. All other solvents were purchased from Fisher Scientific or Biosolve. Dry solvents were used directly from a drying and degassing inert solvent tower system. METHODS Synthesis of polymers Synthesis of polymers Polycaprolactone (PCL51) synthesized by ring-opening polymerization. Ring-opening polymerization was conducted in a glove box filled with N2. Briefly, caprolactone (2.246g, 19.68 mmol), diphenylphosphate (DPP, 70.33 mg, 0.28 mmol), and CHPET (2-cyano- 5-hydroxypentan-2-yl-ethyl carbonotrithioate; 70 mg, 0.28 mmol) were weighed accurately in vials and then transferred to a 50-mL round bottle flask. Toluene (19.726 mL) was used as the solvent for the reaction. Polymerization was conducted at room temperature, and 1H NMR was used to monitor the process. After about 6.5 h, the reaction was quenched by the Amberlyst S6 agent, and the solution was removed from the glove box. The crude product was precipitated into cold diethyl ether 3 times and collected after centrifugation.1.34 g (monomer conversion: 71%) of light-yellow solid was obtained before it was dry in a vacuum oven.1H NMR (400 MHz, Chloroform-d, δ (ppm)): 4.06 (t, J = 6.7 Hz, 2H, COOCH2), 2.30 (t, J = 7.5 Hz, 2H, CH2COO), 1.65 (dtt, J = 13.4, 6.7, 3.7 Hz, 4H, COOCH2CH2CH2CH2CH2OH), 1.44 – 1.32 (m, 2H, (CH2)2CH2(CH2)2). Polycaprolactone-b-polydimethylacetamide (PCL51-PDMA189) synthesized by Reversible addition–fragmentation chain transfer (RAFT) polymerization Macro-CTA (PCL50, 100 mg, 0.0168 mmol), DMA (399.7 mg, 4.032 mmol), and AIBN (0.276 mg, 0.00168 mmol, 10 mg mL-1 in dioxane) were dissolved in dioxane (1 mL) and then transferred into an ampoule. The solution was freeze-pump thawed three times before the ampoule was immersed in an oil bath set at 70 °C. After 2 hours, polymerization was quenched by immersing the ampoule in the liquid N2. The crude product was precipitated into the cold diethyl ether once it reached room temperature and then collected by centrifugation, and this process was repeated three times. After drying in a vacuum oven for 3 days, 458.5 mg (monomer conversion: 80%) of a solid product was obtained.1H NMR (400 MHz, Chloroform- d, δ (ppm)): 4.06 (t, J = 6.7 Hz, 2H, COOCH2), 3.21 – 2.75 (m, 6H, CON(CH3)2), 2.30 (t, J = 7.5 Hz, 1H, CH2COO), 1.71 – 1.58 (m, 4H, COOCH2CH2CH2CH2CH2OH), 1.44 – 1.32 (m, 2H, (CH2)2CH2(CH2)2). Living Epitaxial Growth of 2D Platelet. PCL homopolymer with block copolymer PCL-b-PDMA, or PCL-ACM homopolymer with block copolymers PCL-b-PDMA-ACM dissolved in THF, DMF or Chloroform (10 mg mL-1or 50 mg mL-1) was added to a dispersion of crystalline seeds (0.01 mg mL-1) in a screw cap vial. Typical living CDSA procedure: if fix the ratio of unimer-to-seed is 10, 10 uL of unimer solution (10 mg / mL, PCL / PCL-b-PX in a 1:1 w / w ratio dissolved in THF) was added to 1 mL of seed solution (0.01 mg / mL in ethanol)) S10 After shaking the vials for 5 s, the solution was aged for 2 days at room temperature. The unimer-to-seed ratio was altered by adding different volumes of unimer solution to the dispersion of seed micelles (When the ratio of unimers to seeds above 20, the concentration of unimers changes to 50 mg mL-1 ). The of contour lengths, widths and areas were measured from AFM and CLSM images. General procedure for CDSA Cylinders prepared by direct crystallisation-driven self-assembly (CDSA) PCL51-b-PDMA189(10 mg) and ethanol (2 mL) were measured accurately and added into a 7- mL vial. The mixture was heated at 70 °C for 3 hours without stirring and then left to cool down naturally. After ageing for 7 days at room temperature, a cloudy cylinder solution was obtained. Seeds prepared by sonicating cylinders The original solution of cylinders was diluted to 0.5 mg·mL-1, and then 3 mL of the diluted solution was transferred into a quartz tube and immersed in the dry ice-acetone bath during the whole sonication process. A total of 20 min sonication was applied by a sonic probe with the model of 60 cycles of a 20-second sonication followed by a 100- second pause. The obtained solution of seeds was transferred to a vial for storage and imaged through TEM to determine the average size. General procedure of living CDSA to prepare platelets in batch The solution of seeds was diluted to 0.01 mg mL-1, and then in the 1-mL scale, the unimer solution (10 mg·mL-1of the 1:1 mixture in weight of homo and diblock polymers in CHCl3) of a pre-calculated amount was added. After a 5-second handshake followed by 2-minute ageing at room temperature, samples were prepared for TEM or AFM, and the average size of platelets was measured according to the obtained images. For the batch scale-up, a 10-mL scale living CDSA was conducted using the same procedure. General procedure of living CDSA to prepare platelets in the flow reactor Seeds (or original platelets) and unimer were loaded into syringes, and then the mixer and coil were buried in the sand bath at a pre-set temperature and equilibrated for 30 minutes before the flow started. Every time flow rates, seeds, or unimer were changed, samples were collected after passing 3 reactor volumes to make sure they reached the steady state. Ice nucleation activity experiments To determine the ice nucleation activity of platelets, stock solutions of 1 mg / mL of platelets were created by resuspending platelets in milli-Q®(MQ) water. Additional samples with lower concentrations were obtained by further diluting these stocks with MQ. All samples were compared with the homogeneous ice nucleation reference, made from the same MQ batch. For those platelets that showed activity in MQ their activity was also measured in relevant media and compared with a reference of pure media. Ice nucleation activity was assessed via optical freezing arrays with different droplet volumes. Both the Bielefeld Ice Nucleation ARraY (BINARY) for microliter droplets and nanoBINARY setup for nanoliter sized droplets used in these experiments have been described in more detail in previous publications (Budke et al., Atmospheric Meas. Tech.2015, 8 (2), 689–703; Eickhoff et al., J. Chem. Phys.2023, 158 (15), 154504). In short, the BINARY setup consists of an array of individual 0.60 µL droplets on a thin glass slide, pretreated with trichloro(1H,1H,2H,2H-perfluorooctyl)silane to reduce the contact area. Droplets are separated from each other using a silicon mask and a glass cover and are cooled at a controlled rate using a Peltier cooling stage. The nanoBINARY setup is based on the same principle but utilizes a microfluidic chip design and forms droplets of ~0.4 nL in a fluorinated oil phase (HFE-7500 with 2 wt.% PFPE-Tris). The nucleation activity of platelets can be quantified and compared by plotting the frozen fraction curve as (f (T)) vs temperature and is given by the cumulative number of frozenicedroplets at a specific temperature T (Nfrozen(T)) divided by the total number of observed dropletsin an experiment (N ) according to the equation: (^) =ே^౨^^^^total(்)^^^^ே౪^౪^^. Nucleation temperature per condition are reported as the temperature for which ficeis 0.5. EXAMPLES A schematic overview of the platelet formation is depicted in Figure 1A. For the platelets used for the examples below, platelet assembly starts with PCL -b-PDMA based seeds of51 189 approximately 50nm length. Different sizes platelets were obtained by variations in the seed to unimer ratios. All platelets utilized a 1:1 wt% ratio of PCL51and PCL51-b-PDMA189unimers. The height of all platelets is ~10 nm, and length, width and area of the platelets (see Figure 1B for a schematic) are summarized in Table 1. Table 1: Overview of the Platelets used in the next examples. Platelet #: 1 2 3 4 Length 284±34 463±59 628±106 1850±120 (nm) Aspect 2.11±0.20 2.45±0.29 2.60±0.29 3.25±0.13 ratio Area 0.029±0.005 0.069±0.016 0.124±0.045 0.894±0.055 (µm2) Figure 1D is a cartoon representation of the nucleation experiments used in the examples below. Unless stated otherwise, all nucleation experiments were performed in MQ water with a -1°C cooling ramp using the platelets summarized in Table 1. Activity of platelets 1,2,3, and 4 were determined using the nanoBINARY (0.4 nL droplets) and / or the BINARY (0.6 µL droplets) setup and were compared with pure MQ water. All temperatures for which fice(T)=0.5 are reported in Table 2. Example 1: Platelet 1 was suspended in MQ at a concentration of 0.5 mg / mL. Ice nucleation was measured at 0.5 mg / mL in both 0.4 nL and 0.6 µL droplets (see Figure 2A). Based on these results it was concluded that Platelet 1 shows no nucleation activity. Example 2: Platelet 2 was suspended in MQ at concentrations of 0.5 mg / mL, 0.22 mg / mL, 0.05 mg / mL and 0.005 mg / mL. Ice nucleation was measured at 0.5, 0.05 and 0.005 mg / mL in 0.6 µL droplets and at 0.5 and 0.22 mg / mL in 0.4 nL droplets (see Figure 2B). Based on these results it was concluded that Platelet 3 shows nucleation activity at all concentrations Example 3: Platelet 3 was suspended in MQ at concentrations of 0.5 mg / mL and 0.05 mg / mL. Ice nucleation was measured at 0.5 and 0.05 mg / mL in 0.6 µL droplets and at 0.5 mg / mL in 0.4 nL droplets (see Figure 2C). Based on these results it was concluded that Platelet 4 shows nucleation activity at all concentrations. Example 4: Platelet 4 was suspended in MQ at concentrations of 2.0 mg / mL, 0.5 mg / mL and 0.05 mg / mL. Ice nucleation was measured at 2.0, 0.5 and 0.05 mg / mL in 0.6 µL droplets and at 0.5 mg / mL in 0.4 nL droplets (see Figure 2D). Based on these results it was concluded that Platelet 5 shows nucleation activity at all concentrations. Table 2: Summary of nucleation temperatures ( fice(T)=0.5 ) of examples 1-4 Water Platelet 1 Platelet 2 Platelet 3 Platelet 4 0.4 nL -36.6°C 0.5 mg / mL -36.7°C -24.2°C -25.5°C -26.7°C 0.22 mg / mL -25.7°C 0.6 µL -27.3°C 2 mg / mL -20.0°C 1 mg / mL 0.5 mg / mL -25.9°C -19.0°C -20.0°C -21.9°C 0.05 mg / mL -21.6°C -21.9°C -23.5°C 0.005 mg / mL -22.6°C

Claims

CLAIMS 1. Use of a platelet of at least one homopolymer and / or at least one copolymer for inducing ice nucleating in an aqueous liquid, wherein the homopolymer is selected from the group consisting of PCL, PHL, PVL, POL, PDDL, PFS, PLLA, PDHF, PC, and PPDO; and wherein the copolymer comprises first units from first monomers selected from the group consisting of CL, HL, VL, OL, DDL, FS, LLA, DHF, C and PDO and second units from second monomers selected from the group consisting of DMA, NAM, 4VP, 2VP, DMAEMA, qDMAEMA and AA, preferably wherein the platelet is formed by crystallization driven self-assembly (CDSA).

2. Use of the platelet according to claim 1, wherein the homopolymer is PCL and / or the copolymer comprises first units from CL as first monomer and seconds units from DMA as the second monomer (PCL-PDMA), preferably a platelet of PCL and PCL-PDMA.

3. Use of the platelet according to any of the previous claims, wherein the copolymer is a block copolymer.

4. Use of the platelet according to any of the previous claims, wherein the mass average molar mass (MW) of the poly(caprolactone) is between 1 and 30 kDa, preferably between 2 and 15 kDa and / or wherein the Mass average molar mass (MW) of the caprolactone block copolymer is between 2 and 100 kDa, preferably between 7 and 80 kDa.

5. Use of the platelet according to any of the previous claims, wherein the platelet has a weight ratio of the at least one homopolymer to the at least one copolymer of between 1 to 10 and 10 to 1, preferably 1 to 1.

6. Use of the platelet according to any of the previous claims, wherein the temperature at which the ice nucleation occurs in the aqueous liquid comprising the platelet is increased by at least 10%, at least 20%, at least 30% at least 50%, or, between 10% and 60%, between 15%and 45%, between 20% and 50% compared to a temperature at which ice nucleation occurs in an aqueous liquid not comprising the platelet.

7. Use of the platelet according to any of the previous claims, wherein the platelet has a length of at least 280 nm, preferably at least 460 nm and / or wherein aspect ratio of the platelet is between 1:1 and 1:100, between 1:1 and 1:50, between 1:1 and 1:25, between 1:1 and 1:10, between 1:1 and 1:5, or between 1:1 and 1:

2.

8. Use of the platelet according to any of the previous claims, wherein the platelet has a hexagonal shape.

9. Use of the platelet according to any of the previous claims, wherein the platelet has a thickness of between 5 and 25 nm.

10. Use of the platelet according to any of the previous claims, wherein the platelet concentration in the aqueous liquid is between 0.1 and 10 mg / mL.

11. Use of the platelet according to any of the previous claims, wherein the aqueous liquid has a volume of between 0.5 and 5000 µL, preferably between 0.5 and 1000 µL.

12. Use of the platelet according to any of the previous claims, wherein the aqueous liquid further comprises cells, preferably living cells, polynucleotides, oligonucleotides, DNA, mRNA, ssRNA, lipids, and / or proteins or fragments thereof.

13. Use of the platelet according to any of the previous claims in cryopreservation, preferably cryopreservation of cells, preferably living cells, polynucleotides, oligonucleotides, DNA, mRNA, ssRNA, lipids, and / or proteins or fragments thereof.

14. Use of the platelet according to any of the previous claims, wherein the platelet is formed by crystallization driven self-assembly (CDSA) of a homopolymer and two or more copolymers thereby forming a multilayered platelet.

15. Use of the platelet according to any of the previous claims, wherein the temperature spread at which ice nucleation occurs in an aqueous liquid comprising the platelet is decreased by at least 10%, at least 20%, at least 30%, at least 50% or at least 75% compared to an aqueous liquid without the platelet.

16. Use of the platelet according to any of the previous claims, wherein the variation in cell viability is improved by at least 10%, at least 20%, at least 30%, at least 50% or at least 75% compared to an aqueous liquid without the platelet.

17. A method of inducing ice nucleation in an aqueous liquid comprising the steps: a) providing a platelet as defined in any of claims 1 - 16; b) mixing the platelet of step a) with the aqueous liquid, preferably wherein the concentration of platelets in the aqueous liquid is between 0.1 and 10 mg / mL; c) cooling the aqueous liquid of step b), preferably at a rate of -1 degrees Celsius per minute, thereby inducing the ice nucleation; and d) optionally, further cooling aqueous liquid of step c) to a desired temperature and / or storing the aqueous liquid of step c).

18. A cryopreserved sample, obtainable by the method according to claim 17.

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