High pressure single-use electrochemical analytical sensor

Abstract

A single-use electrochemical analytical sensor (200) is provided. The sensor (200) includes a sensing electrode (224) configured to contact a process fluid and a reference chamber (260, 202) containing an electrolyte. A reference electrode (225) is disposed in the electrolyte. A reference junction (258) is configured to contact the process fluid and is further configured to generate a flow of the electrolyte into the process fluid. The reference chamber (260, 202) is configured to be stored in a reduced pressure state and then pressurized prior to operation. A method (400) of operating a single-use electrochemical sensor is also provided.

Description

Background Technology

[0001] Over the past two decades, single-use or disposable bioprocessing systems have gained significant momentum in replacing stainless steel systems in biopharmaceutical manufacturing. Compared to conventional systems modified from stainless steel equipment, single-use systems rely on highly engineered polymers and undergo pre-sterilization via gamma radiation. For end users, they offer several significant advantages, including reduced initial investment, elimination of complex pre-cleaning, sterilization, and validation processes, and improved process turnaround times. As a result, single-use bioprocessing systems have moved from initial R&D laboratories to large-scale commercial pharmaceutical manufacturing.

[0002] pH is a critical process parameter in many processes of biopharmaceutical manufacturing. In upstream bioreactor applications, the pH of the culture medium is continuously monitored and controlled within a narrow physiological range, and deviations from this ideal pH range can negatively impact cell concentration, protein productivity, and quality. Traditional pH sensors used in biopharmaceutical manufacturing are based on electrochemical measurement methods with a pH-sensitive glass electrode and a reference electrode. This is a mature technology that has proven successful in the biotechnology and pharmaceutical industries due to its high reliability, accuracy, and stability.

[0003] However, conventional pH sensors are designed to be compatible with standard stainless steel bioreactor systems, and therefore have several significant limitations when used in single-use systems. First, conventional sensors must be sterilized by the end user using autoclaving, in-situ steam sterilization, or in-situ cleaning procedures. They are generally incompatible with gamma-ray irradiation sterilization processes, as gamma radiation can damage their sensing components and cause undesirable performance degradation. To ensure satisfactory accuracy, conventional pH sensors typically require two-point calibration by the end user between uses, which is both cumbersome and adds to the complexity of the process. Furthermore, conventional pH sensors typically have a shelf life of one year because the pH sensing glass ages over time, leading to a decline in sensor performance. Unfortunately, for single-use systems, a longer sensor shelf life is preferable, as the sensor can be attached as a separate component of a plastic bioreactor bag or to a tubing kit for downstream applications, with the expectation of an even longer shelf life. Summary of the Invention

[0004] A single-use electrochemical analysis sensor is provided. The sensor includes a sensing electrode configured to contact a process fluid and a reference chamber containing an electrolyte. The reference electrode is disposed in the electrolyte. A reference connector is configured to contact the process fluid and is also configured to generate an electrolyte flow into the process fluid. The reference chamber is configured to be stored under reduced pressure and then pressurized prior to operation. A method for operating the single-use electrochemical sensor is also provided. Attached Figure Description

[0005] Figure 1A and Figure 1B This is a schematic diagram of a pH sensor used in low-pressure bioreactor applications, showing the storage location and the operating location.

[0006] Figure 2 This is a graph showing how the reference chamber pressure of the pH sensor decays over time.

[0007] Figure 3A and Figure 3B This is a schematic diagram of a pH sensor for downstream applications according to one embodiment.

[0008] Figure 4 This is a flowchart of a method for operating a disposable electrochemical analysis sensor according to one embodiment. Detailed Implementation

[0009] Figure 1A and Figure 1B This is a schematic diagram of a pH sensor for low-pressure (i.e., upstream) bioreactor applications, showing the storage and operating locations. Suppliers of single-use instruments typically assemble the pH sensor into a tubular kit and sterilize the assembly by gamma irradiation. A two-year shelf life is expected for this type of sensor to allow for efficient supply chain management and provide a reasonable storage life for users. Any fluid loss in this small, sealed volume during sensor manufacturing, when pressurizing the reference chamber, significantly reduces the pressure.

[0010] Figure 1A This is a schematic diagram showing the storage location of a pH sensor. In the example shown, the pH sensor is generally shown in cross-section, having a distal end 102 and a proximal end 104. The distal end 102 is generally configured to engage process reagents or process space or process environment, such as a bioreactor bag, and the proximal end 104 has an electrical connector 106 configured to be coupled to an instrument. An example of connector 106 is referred to as a Variopin connector.

[0011] Some electrochemical analytical sensors are considered amperometric because they generate currents that indicate process variables (e.g., pH). Other types of sensors are considered potential sensors because they generate potentials that indicate process variables. As used herein, electrochemical analytical sensors are intended to include any analytical sensor with electrical properties that vary with process variables.

[0012] like Figure 1A The sensor 100 shown is configured in a storage position, in which the process plunger 108 is spaced apart from the locking member 110. In the storage configuration, the pH-sensing glass electrode 112 is held within a storage chamber 114 filled with a buffer solution. Figure 1A As can be seen, a reference electrode 116 is disposed within an electrolyte 118, which is configured to be electrically connected to the process reagent via a reference connector 120. The sensor 100 is maintained in a storage position for both storage and calibration immediately prior to operation. This is because the buffer solution in the storage chamber 114 has a known pH, and the sensor can be calibrated or otherwise characterized by measuring the pH with electrode 112 and comparing the measured value to the known pH of the buffer solution.

[0013] Figure 1B This is a schematic diagram showing the pH sensor 100 in its operating position. (Comparison) Figure 1B and Figure 1A This shows that the process plunger 108 has slid into proximity to the locking member 110. This sliding movement has caused the end 122 to extend from the sidewall 124, thereby exposing the pH glass electrode 112 to the process reagent 126. It can be seen that the process reagent 126 is also exposed to the reference connector 120. Therefore, the sliding movement from the storage position to the operating position has exposed the wet storage chamber 114 to the process reagent 126. Figure 1B In the configuration shown, sensor 100 can be used to sense the pH of a process fluid, such as a bioreaction fluid, cell culture medium, or mash.

[0014] like Figure 1A and Figure 1B As shown, the sensor provides wet storage for the pH glass and reference connector via a separate storage chamber and a sliding sensor assembly that moves axially within the process connector and enters the process reagent upon startup. The sliding sensor assembly can provide reliable measurements at low process pressures. Note that the process connector sleeve remains fixed relative to the process medium, and the sensor moves as it is inserted into the process reagent.

[0015] This disposable pH sensor is compatible with gamma-ray radiation sterilization and can be attached to a disposable bioreactor bag to form an assembly. By incorporating a unique storage buffer solution, the sensor eliminates the need for two-point calibration by the end user and allows for one-point standardization using the storage buffer solution. More importantly, the storage buffer solution contacts both the pH electrode and the reference electrode, keeping them moist and fresh during sensor storage. This wet storage results in a long shelf life of 2 years with excellent sensor performance, including high accuracy, sensitivity, and stability. Rigorous real-time testing of prototypes—unaged, aged for 1 year, and aged for 2 years—demonstrates that sensor performance remains at a high level without degradation after 2 years of storage.

[0016] After the cell culture process is completed in the bioreactor bag, the medium is moved downstream of the process reagent. Here, the medium is propelled through a filtration stage in a small-diameter pipe at a relatively high pressure of up to 90 psi. This high process pressure can be problematic for conventional pH sensors. Conventional glass electrode pH sensors have a reference connector, which is a constrained path connecting the sensor's reference chamber and the electrolyte buffer solution within it to the process reagent. An example of such a connector is a porous ceramic cylinder or tank placed between the reference chamber and the user's process reagent. Another example is a polymer connector. A positive ion flow from the sensor's reference chamber to the process fluid must be present for the sensor to operate correctly.

[0017] Higher process pressures in downstream applications can interfere with the ion flow and cause pH reading fluctuations or drift. This interference can be mitigated by pressurizing the reference chamber. However, previous methods of pressurizing the reference required specialized pressurization techniques at the plant. Because the reference connector is porous and the reference chamber is pressurized, the pressure decays over time, limiting the sensor's storage life and service life.

[0018] Figure 2 This is a graph showing how the reference pressure for the pH sensor decays over time. More specifically, Figure 2 Curve-fitted data of baseline pressure decay in an improved commercially available sensor (sealed connector, air-filled) is shown – data source: 14-day pressure decay data at 60 days. Figure 2 The data in the figure are curve-fitted and extrapolated from -60 days to +180 days. Figure 2Test data has shown that, assuming the sensor's reference chamber is initially pressurized to 90 psi and a minimum reference chamber pressure of 30 psi is required for the sensor to function properly, the possible shelf life is up to six months. Furthermore, once the sensor is moved to the "operating" position, the reference connector (a porous material) is essentially a leak point and will allow pressure to decay during use, thus limiting the operational life. As explained above, the expectation is to provide a single-use pH sensor that is compatible with downstream applications and has a viable shelf life (2 years) as long as the upstream sensor.

[0019] Figure 3A This is a schematic diagram of a pH sensor for a downstream application according to one embodiment. In the illustrated example, the pH sensor 200 is provided with a reference chamber 202, which can be pressurized upon installation. This maximizes the unit's storage life because there is no pressure differential driving reference fluid through a reference joint or seal, and therefore no pressure loss during storage. Instead, a user-actuable mechanism 204 is used to generate the desired pressure in the reference chamber 202. In one example, a piston 206 is pressed down or otherwise actuated in a cylinder 208, which is part of or fluidly coupled to the reference chamber 202, to generate the desired pressure upon process initiation. The force on the piston 206 can be provided by compressing a spring 210, such as a wave spring, to provide a pressure close to constant over time, as fluid in the auxiliary reference chamber 202 is slowly expelled through a porous reference joint. Other spring types can be used to provide constant pressure, including using the expansion of the reference chamber itself under pressure as a potential energy source, or compressing the gas in the chamber to act as a spring. This solves the storage life problem and provides a longer operational life.

[0020] Figure 3AA sensor 200 with an electrical connector 220 having a plurality of electrical contacts 222 is shown. The contacts 222 are coupled to sensing elements within the sensor 200, such as a pH glass electrode 224 and a reference electrode 225. Additionally, if additional sensing elements are used in the sensor 200 (e.g., a temperature sensor and / or a pressure sensor), the contacts 222 facilitate electrical connection to such elements. The connector 220 may include any suitable features that facilitate mating with a mating connector, such as an external threaded region 228. The connector 220 is preferably a hermetically sealed electrical connector such that the inner cavity 226 is fluidly isolated from the cable or connector to which it is coupled. In one embodiment, the connector 220 is a Variopin connector. The connector 220 is secured to the sensor 200 by a sleeve 230 that causes a sidewall 232 to contact an end 234 of a sidewall 236. Additionally, the sidewall 236 preferably includes a groove 238 therein for placing an O-ring 240. Then, when the sleeve 230 is threaded onto the side wall 232, the inner surface of the sleeve 230 abuts against the O-ring 240 for sealing.

[0021] Sidewall 236 is mounted or otherwise secured to end 242, which includes flange 244, the flange 244 being sized to extend beyond and around end 246 of sidewall 248. End 242 may be constructed of the same polymer as sidewall 236 and / or sidewall 248, and end 242 may be secured thereto by any suitable method including solvent welding, adhesives, ultrasonic welding, etc.

[0022] The sensor 200 also includes an insert 250 that contacts the inner diameter 252 of the sidewall 248 and includes a central aperture 254 sized to mount the pH electrode 224 along the longitudinal axis of the sensor 200. The insert 250 also includes a sleeve 256 that extends along the length of the pH electrode 224 and passes through an orifice in a reference connector disc 258. The disc 258 may be a porous ceramic disc configured to release a controlled amount of electrolyte into the process reagent over time. However, embodiments in which the reference connector has other types of physical configurations (e.g., small tubing or multiple such tubing) may be implemented.

[0023] Sidewall 248 defines a pair of reference chambers 260, 202 and a conduit 262 that fluidly connects the main reference chamber 260 to the auxiliary reference chamber 202. At least a portion of the fluid electrolyte is disposed within the reference chambers 260, 202. The electrolyte can be a liquid or a gel, but must have the ability to flow to some extent through the reference connector 258. It can be seen that by pressurizing the auxiliary reference chamber 202, the main reference chamber 260 will also be pressurized. This pressurization helps maintain electrolyte outflow from the reference connector even when the process fluid pressure increases. Figure 3A In the configuration shown, the pressure activation mechanism 204 includes an internal threaded portion connected to an external threaded portion 264 of the sidewall 248. The pressure activation mechanism is shown in an idle configuration, wherein pistons 206 and 266 are adjacent to the pressure activation mechanism 204 and are substantially disposed within the threaded portion 264.

[0024] Figure 3B This is a schematic diagram of sensor 200 in a pressure engagement configuration. Figure 3B and Figure 3A In contrast, the engagement of pressure activation feature 204 shows that pistons 266 and 206 have been displaced toward electrode 224, thereby reducing the size of auxiliary reference chamber 202 and pressurizing main reference chamber 260. Additionally, in the illustrated configuration, pistons 266 and 206 have both been displaced by the same distance. As the electrolyte slowly flows through reference connector 258, the pressure compensation mechanism (e.g., spring 210) will displace piston 206 away from the fixed pressure engagement position of piston 266. In this way, the pressure in main reference chamber 260 will be maintained at the desired level until piston 206 bottoms out against sidewall 248. In one embodiment, sidewall 248, or a portion thereof, is formed of a transparent or translucent material, allowing the position of piston 206 to be observed by the user to assess the remaining pressure compensation life of the pressure compensation mechanism.

[0025] Figure 3A and Figure 3B A sensor 200 is shown coupled to a process adapter 280 configured to position the sensor's sensing element within a process fluid. In the example shown, the process adapter 280 includes a sensor port 282 configured to receive the internal threads of the external threads 284 of the sensor 200. The sensor 200 may also include one or more O-rings 286 configured to engage and seal with the process adapter 280. Although the process adapter 280 is shown as having a clean flange 290 for coupling to a corresponding flange, any suitable coupling mechanism can be used.

[0026] Figure 4This is a flowchart of a method for operating a single-use electrochemical analysis sensor according to one embodiment. Method 400 begins at block 402, where a single-use electrochemical sensor is provided. The sensor may be a pH sensor 404, an ion sensor 406, or any other sensor 408 that includes an electrolyte that must flow into the process fluid to generate a sensor signal. At block 410, a process connector is obtained. If the sensor is to be coupled to a downstream single-use process reagent, the process connector may be process connector 280 (…). Figure 3B (As shown). However, process connectors are typically process-specific and configured to position the sensor in or appropriately close to the process fluid to obtain a process variable signal. Next, at optional block 412, the sensor and process connector can be sterilized. This can be done using gamma radiation 414, X-ray radiation, or via other suitable method 416. The sterilized sensor and / or process connector can be packaged or otherwise maintained under sterile conditions until called for use. When such use is required, block 418 is executed, where the sensor is pressurized immediately prior to use. This pressurization is preferably via a knob or user-actuable pressure activation mechanism (e.g., mechanism 204). Figure 3B This is accomplished manually, as shown in the diagram. Finally, at box 420, a pressurized sensor is used to sense the process fluid.

[0027] Therefore, it can be seen that because the sensor is not pressurized during storage, a sensor and method that facilitates a long storage life are provided. Then, immediately before operation, the sensor is pressurized to allow for accurate and precise operation in pressurized process fluid environments (e.g., downstream processing). Additionally, it is believed that the storage life and product life of the pH sensor can be extended by increasing the viscosity of the reference electrolyte within the device. For example, a thick reference gel can be used for this purpose. Using a higher viscosity reference gel will result in a longer service life. Furthermore, introducing a reference gel will reduce the internal pressure required for the sensor to operate well under high external process pressures.

[0028] Piston actuation can be accomplished in several ways. In one embodiment, the spring is compressed during sensor assembly, and the piston is locked in place by a feature in the cylinder, preventing it from pressurizing the system. When the piston cap rotates 90 degrees, the piston moves away from the retaining structure and provides force to generate pressure in the system. Furthermore, the actuated piston can also be locked in the actuated position by a locking mechanism.

[0029] In another embodiment, the installer pushes or pulls the piston cap, while a feature on the cylinder body holds the piston cap in place when the user rotates it 90 degrees. Alternatively, the cap can be held in place by a snap-fit ​​feature without rotation.

[0030] Note that the pressurization method described herein is not limited to pH sensors, but can be generally applied to other ion sensors that measure potential. These ion sensors include, but are not limited to, potassium, sodium, chloride, and fluorine sensors, to name just a few. As long as the sensor's reference electrode relies on the diffusion of an internal reference electrolyte through a porous connector material, it can be pressurized using the method described above.

[0031] Although the invention has been described with reference to preferred embodiments, those skilled in the art will recognize that changes in form and detail may be made without departing from the spirit and scope of the invention. For example, while the description provided above illustrates pressurization of the reference chamber in a particular manner, such pressurization can take various forms. The sensor may include a spring member that is preloaded at the factory and released in the field to apply pressure to the reference chamber. In another example, the unloaded spring member may be compressed by pushing in the field. In yet another example, the unloaded spring member may be compressed by pulling in the field. In yet another example, the unloaded spring member may be compressed by screwing in the field. In another example, the unloaded spring member may be compressed by pushing and twisting in the field. In yet another example, the unloaded spring member may be compressed by pulling and twisting in the field.

Claims

1. A disposable electrochemical analysis sensor, comprising: A sensing electrode configured to contact the process fluid; A reference chamber containing an electrolyte; A reference electrode, wherein the reference electrode is disposed in the electrolyte; A reference connector, configured to contact the process fluid, and further configured to generate an electrolyte flow into the process fluid; and The reference chamber is configured to be stored in a depressurized state and then pressurized before operation. The disposable electrochemical analysis sensor also includes a pressure activation mechanism configured to generate pressure in the reference chamber when activated.

2. The disposable electrochemical analysis sensor according to claim 1, wherein, The pressure activation mechanism includes: A first movable piston is configured to generate pressure in the reference chamber as the first movable piston moves.

3. The disposable electrochemical analysis sensor according to claim 2, further comprising an O-ring seal disposed around the first movable piston.

4. The disposable electrochemical analysis sensor according to claim 2 further includes a second movable piston, the second movable piston being spaced apart from the first movable piston by a spring.

5. The disposable electrochemical analysis sensor according to claim 4 further includes a mechanical latching mechanism for locking the second movable piston in the pressurized position.

6. The disposable electrochemical analysis sensor according to claim 4, wherein, The spring is configured to move the first movable piston away from the second movable piston as the electrolyte flows into the process fluid, in order to maintain pressure in the electrolyte.

7. The disposable electrochemical analysis sensor according to claim 6, wherein, The sidewall of the sensor containing the first movable piston is made of a material that allows the position of the piston to be observed through the sidewall.

8. The disposable electrochemical analysis sensor according to claim 1, wherein, The electrolyte is a gel.

9. The disposable electrochemical analysis sensor according to claim 1, wherein, The reference chamber is configured to be pressurized to 90 psi.

10. The disposable electrochemical analysis sensor according to claim 1, wherein, The sensing electrode is a pH glass electrode.

11. The disposable electrochemical analysis sensor according to claim 1, wherein, The reference connector is a porous disc.

12. The disposable electrochemical analysis sensor according to claim 11, wherein, The disk is made of a material selected from the group consisting of ceramics and polymers.

13. The disposable electrochemical analysis sensor of claim 1, further comprising a process connector operably connected to the sensor for downstream flow.

14. The disposable electrochemical analysis sensor according to claim 13, wherein, At least one of the sensor and the process connector is sterilized.

15. A method for operating a single-use electrochemical analysis sensor, the method comprising: Provide single-use electrochemical analysis sensors; A process connection is provided, the process connection being accessible to process fluids; The reference chamber of the disposable electrochemical sensor is pressurized; as well as The single-use electrochemical sensor, after being pressurized, is used to sense the properties of the process fluid.

16. The method according to claim 15, wherein, The reference chamber is pressurized by either compressed gas or a mechanical hydraulic system, wherein the internal pressure of the reference chamber is between 0 psi and 100 psi.

17. The method of claim 15, further comprising: Before pressurizing the reference chamber, at least one of the disposable electrochemical sensor and the process coupling is sterilized.

18. The method according to claim 17, wherein, The sterilization process employs at least one of gamma ray radiation and X-ray radiation.

19. The method according to claim 15, wherein, The disposable electrochemical sensor is a pH sensor.

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