Method for enhancing filtration yields in tangential flow filtration system

Abstract

The disclosure generally relates to methods and apparatus for the efficient quantitative recovery of valuable biological fluids from filtration systems, more particularly to efficient quantitative recovery of valuable biological fluids from high precision separation systems suitable for use in the pharmaceutical and biotechnology industries.

Claims

1. A process for enhanced recovery of a biological fluid from an activated crossflow filtration system, the process comprising: a. inducing an internalized pressurized countercurrent flow throughout the activated crossflow filtration system by activating an internal pump fluidically coupled to a sterile air source at a first end of the activated crossflow filtration system to cause said biological fluid to flow in a flow direction from the sterile air source toward a drain valve and opposite to a crossflow direction, b. recovering said biological fluid at the drain valve fluidically coupled at a second end opposite the first end of the activated crossflow filtration system, wherein the crossflow direction is along a fluid loop from a biofluid source container to a crossflow filtration filter and back to the biofluid source container, wherein the activating of the internal pump causes sterile air from the sterile air source to be introduced into the fluid loop between the biofluid source container and the crossflow filtration filter, and wherein said inducing of the internalized pressurized countercurrent flow comprises supplying sterile air from the sterile air source passively.

2. The process according to claim 1, wherein said internal pump is a peristaltic pump.

3. The process according to claim 1, wherein said activated crossflow filtration system comprises a series of tubes, valves, sensors, and conduits connected together to form a flowpath.

4. The process according to claim 1, wherein said internal pump is located adjacent to the biofluid source container.

5. The process according to claim 1, wherein activating said internal pump comprises operating said internal pump between 10-10,000 rpm.

6. The process according to claim 1, wherein activating said internal pump comprises operating said internal pump between 100-1000 rpm.

7. The process according to claim 1, wherein activating said internal pump comprises operating said internal pump to generate an air flow output of from 1 mL/min to 1 L/min.

8. The process according to claim 7, wherein said internal pump generates pressure between 1 psi to 150 psi.

9. The process according to claim 7, wherein said internal pump generates pressure between 14 to 100 psi.

10. The process according to claim 1, wherein said internal pump generates pressure between 14 to 50 psi.

11. The process according to claim 1 for enhanced recovery of a biological fluid from the activated crossflow filtration system wherein said internal pump induces air flow at about 2 L/min.

12. The process according to claim 1 for enhanced recovery of a biological fluid from the activated crossflow filtration system wherein said induction of the internalized pressurized countercurrent flow is about 25% of a maximum flow rate.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The accompanying drawings illustrate presently preferred embodiments of the present disclosure, and together with the general description given above and the detailed description given below, serve to explain the principles of the present disclosure. As shown throughout the drawings, like reference numerals designate like or corresponding parts.

(2) FIG. 1 is a depiction of a Flowpath of a process flow of an exemplary embodiment of a Crossflow Filtration system for processing a biofluid incorporating aspects of the present disclosure.

DETAILED DESCRIPTION

(3) The various diagrams, flow charts and scenarios described herein are only examples, and there are many other scenarios to which the present disclosure will apply.

(4) Crossflow Filtration Systems generally comprise a series of tubes, valves, sensors, and conduits connected together to form a Flowpath. In these systems, an Internal Pump operably linked to a Sterile Air Source is located near the terminus of the Crossflow Filtration System adjacent to a Biofluid Source Container. In one particular embodiment, the Internal Pump operably linked to a Sterile Air Source is located at the terminus of the Crossflow Filtration System adjacent to a Biofluid Source Container.

(5) i. As shown in the tangential Crossflow Filtration System 20 of FIG. 1, a collection of conduits 10 are provided (or otherwise present) to establish passageways and avenues for the circulation and/or flow of sample liquid to or among the various system components and sub-modules. While the number, pattern, and complexity of the conduits will vary depending on the number of system components and sub-modules, in a basic embodiment of the inventive system, the conduits 10 should at the least define, together with the Biofluid Container 1a, Recirculating Pump 2, Internal Pump 4, Sterile Air Source 5, Drain Valve 6, Valves 7, Pressure valves 8, Connections 9 and the Crossflow Filtration Filter 3, a fluid process stream through which the biofluid is conducted, the process stream flowing from said Biofluid Container 1a, into said Crossflow Filtration Filter 3, and back to said Biofluid Container 1a. The system may comprise a Feed Flow Line 11 operably linked from said Biofluid Container, e.g. via the Recirculating Pump, to said Crossflow Filtration Filter containing Feed Flow, a Retentate Flow Line Return 12 operably linked from said Crossflow Filtration Filter to said Biofluid Container; said Retentate Flow Line Return containing unFiltered Flow, and a Permeate Flow Line 13 operably linked to said Crossflow Filtration Filter containing (filtered) Permeate Flow. Further, the system may comprise a Drain Line 14 operably linked by a Drain Valve 6 to said Feed Flow Line.

(6) There are no particular limitations to the type of conduit used. Potential conduit types include, for example, rigid pipes, flexible tubing, and the channels and passages formed in or intrinsic to the device. Other components include valves and connections). Typically, the plurality of conduits employed in the process development device will include a mixture of conduit types. In a preferred embodiment, the bulk of the conduits employed are flexible, substantially biologically inert, synthetic polymeric tubing having an internal diameter of approximately 0.100 inches (0.254 cm).

(7) A plurality of valves 7 are positioned along or otherwise functionally proximate the fluid process stream for regulating the flow of liquid sample therethrough. In operation, flow of liquid through a valve will depend upon whether the valve is in an “open” or “closed” state or—in some circumstances—an intermediate state.

(8) As indicated, a plurality of pumps 2 are positioned along or otherwise functionally proximate the device's fluid process stream to drive the flow of liquid sample therethrough. 1. It is understood that the system may have multiple configurations, for instance a pump on the permeate line. While pumps are preferred, other electronically-controllable means for driving sample liquid through the fluid process stream may be used.

(9) In the automated CFF/TFF system illustrated in FIG. 1, in-line pumps are utilized including positive displacement pumps including peristaltic, transfer, diaphragm, centrifugal, high-pressure positive displacement (HPPD) and solenoid-activated diaphragm pumps. Although pumps are integrated into the system architecture they may thus still be modular so as to further facilitate single use operations where appropriate. Other pump configurations—e.g., piezoelectric-driven, acoustically-driven, thermopneumatically-driven, electrostatically-driven, etc.—may be employed. Potentially useful fluidic micropump devices are disclosed, and/or suggested, and/or mentioned in, for example, U.S. Pat. No. 5,338,164, issued to R. F. Sutton et al. on Aug. 16, 1994; U.S. Pat. No. 4,938,742, issued to J. G. Smits on Jul. 3, 1990; U.S. Pat. No. 6,283,718, issued to A. Prosperetti et al. on Sep. 4, 2001; and U.S. Pat. No. 5,759,015, issued to H. Van Lintel on Jun. 2, 1998, which are hereby incorporated by reference in their entireties.

(10) The solenoid-actuated diaphragm pumps are self priming, micro-dispensing, solenoid actuated micropumps, capable of providing a non-metallic, inert fluid path for the dispensing of high purity or aggressive fluids. Such pumps are available from Bio-Chem Valve, Inc. of Boonton, N.J. 07005.

(11) The high-pressure positive displacement (HPPD) pumps operate such that the driven flow of liquid sample does not fluctuate unacceptably together with back pressure. HPPD pumps include rotary reciprocating pumps such as disclosed in U.S. Pat. No. 5,863,187, issued to D. S. Bensley et al. on Jan. 26, 1999 (hereby incorporated by reference in its entirety), and available from Ivek Corporation of North Springfield, Vt. 05150. In the interest of reducing the device's minimum recirculation volume, the HPPD pumps should be configured to eliminate or otherwise reduce the so-called “dead spaces” where fluid can collect.

(12) A reciprocating pump can suitably comprise a reciprocating moving member, such as e.g. a diaphragm, a membrane or a piston. A reciprocating moving member can move back and forth in relation to a pump chamber (also called a cylinder, when the moving member is a piston), forcing fluid (e.g. culture liquid) out from the pump chamber during an inward stroke of the moving member and sucking fluid (e.g. culture liquid) into the pump chamber during an outward stroke. The stroke volume of the reciprocating pump corresponds to the fluid (culture liquid) volume displaced out from or into the pump chamber during each stroke. The reciprocating pump may e.g. be a fluid-driven diaphragm pump, with a pump chamber and a drive fluid-filled drive chamber separated by a flexible diaphragm, which constitutes the reciprocating moving member. The drive fluid can be a gas, e.g. air, or a liquid. When fluid pressure is applied to the drive chamber via a drive fluid supply line, the diaphragm expels liquid from the pump chamber in an inward stroke and when the fluid pressure is released, the diaphragm flexes back and draws liquid into the pump chamber in an outward stroke. The pump chamber may e.g. be directly connected to the retentate inlet compartment of the filter unit. Alternatively, it may be connected via a fluid connector (not shown), such as a short piece of tubing with a diameter large enough not to impede the liquid flow and a volume significantly smaller than the stroke volume of the reciprocating pump (e.g. less than 20% of the stroke volume, such as less than 10% or less than 5% of the stroke volume), optionally via an aseptic connector.

(13) Pumps, particularly the Internal Pump, when activated (e.g. turned on), induces a pressure in the Flowpath. Such pressure is amenable to various characterizations and methods of measure. Many such measures are framed in light of the manufacturing conditions used to create the pump. One such measure is rotations per minute (rpm) which refers to the rotation of a pressurizing mechanism around an axis or shaft, such as an impeller, in which the rpm describes the induced pressure. Other pressure measures may refer to flow output which measures the output of liquid per unit time expelled from a tube. Alternatively pressure may refer to psi (pounds per square inch) which is a unit of pressure or of stress based on avoirdupois units. The pressure describes the result from a force of one pound-force applied to an area of one square inch. Numerous methods are available to calculate or measure psi and may include so-called absolute, gauged or differential. Such descriptors are typically provided by each pump manufacturer.

(14) In certain embodiments induction of an internalized pressurized Flow is activated by an Internal Pump pressuring flow between 10-10,000 rpm. Another embodiment refers to induction of an internalized pressurized flow by an Internal Pump pressuring flow between 100-1000 rpm.

(15) An alternate embodiment refers to induction of an internalized pressurized flow output of from 1 mL/min to 1 L/min.

(16) Another alternate embodiment refers to induction of an internalized pressurized flow between standard pressure (1 psi) to 150 psi.

(17) Another alternate embodiment refers to induction of an internalized pressurized flow between 14 to 100 psi.

(18) Another alternate embodiment refers to induction of an internalized pressurized flow between 14 to 50 psi.

(19) Another embodiment refers to the control of displaced volume when using the pump.

(20) By use of a pump, control of either displaced volume and/or the pressure downstream from the pump and upstream the filter and flow path to be evacuated from the liquid to be recovered can be secured. This promotes two advantages: a) the process is very gentle and minimizes foaming as it allows the system to be run at slower and at lower pressure. Further, b) accurate control of the amount of fluid (air) being displaced downstream the pump is important when the fluid is recovered in a sterile fashion by emptying it into a bag, for example. Knowledge of the displaced volume improves safety as the bag cannot inflate in an uncontrolled manner. monitor the pressure downstream the pump and upstream the fluid outlet for recovery to determine a pressure vs. time profile that can indicate that all fluid is replaced. This automation also allows for better process documentation (E-batch records of the GMP process), which eventually increases product and patient safety.

(21) The Sterile Air source may also be supplied under pressure. In one embodiment it is supplied passively. In another embodiment it may be supplied at a rate from about 1 to 10 liters per minute.

(22) Another method to measure the Sterile Air flow is in terms the amount of air that can be provided per unit time. According to such measure, another embodiment refers to pressuring air flow at about 2 liters per minute.

(23) Another method to describe Air flow is measured in terms of a percentage of pump flow rate. According to such method, another embodiment refers to Air flow in the range of from 1 to 100% of Flowrate.

(24) Another embodiment refers to pressurized flow at about 25% of maximum flow rate.

(25) Crossflow Filtration Filters are well known in the literature. Such filters may include a cylindrical outer membrane surface symmetrically located about the axis and enclosing a filtrate chamber that is in fluid communication with the filtered fluid outlet. Although they are frequently shaped as a simple cylinder, other configurations may be used including stepped and conical shaped filters. The membrane surface may be fabricated from a wide variety of materials including porous polymers, ceramics and metals. In one embodiment, the membrane is relatively thin, e.g. from 0.2-0.4 mm and may be supported by an underlying rigid frame or porous support. One example is described in US2012/0010063. The pore size (e.g. 1 to 500 micron), shape (e.g. V-shape, cylindrical, slotted) and uniformity of the membrane surface may vary depending upon application. In many embodiments, the membrane surface comprises a corrosion-resistant metal (e.g. electroformed nickel screen) including uniform sized pores having sizes from 5 to 200 microns, or even 10 to 100 microns. Examples of such materials are described: U.S. Pat. Nos. 7,632,416, 7,896,169, US2011/0120959, US 2011/0220586 and US2012/0010063.

(26) For certain biopharmaceutical applications in which the sample liquid under investigation has substantial and significant protein content, forces and circumstances that can lead to the unintended and undesired denaturation of said proteins (i.e., the loss of the physical conformation of the protein's polypeptide constituency) should be avoided and/or mitigated. The mechanical shear forces often produced in the operation of certain pumps, particularly at gas/liquid interfaces (e.g., bubbles), have been linked to protein denaturation, and accordingly, should be mitigated and/or avoided in the selection, manufacture, and incorporation of the device.

(27) A plurality of sensors (not shown) may be positioned along or otherwise functionally proximate the fluid process stream, each sensor capable of acquiring data about the liquid sample in their respective areas of sensitivity. The types of data desirably acquired are those pertaining to the crossflow (also known as tangential flow) filtration process under investigation and relevant to the upward linear scaling thereof, and typically includes, but is not limited to, temperature, pH, pressure, concentration, flow rate, conductivity, flow rate and the like. Any detectors, probes, meters, and like sensing devices capable of acquiring such data can be utilized. Those skilled in the art will know of objectives for and methods of incorporating such sensing devices into the device. Incorporation will involve, among other things, establishment of connectivity with the data processing network 7.

(28) “High-Performance Tangential Flow Filtration” (HPTFF), or HPCFF, refers to one embodiment that is often employed to produce up to 1000 fold purification factors of protein mixtures containing similarly sized species. This is normally not possible in traditional size-exclusion based membrane processes. HPTFF technology exploits differences in the size and thickness of the ionic cloud surrounding proteins. This thickness can be manipulated by changing the pH and ionic strength of a sample solution. Further details regarding HPTFF technology can be found, for example, in R. van Reis et al., Biotech, Bioeng., 56, 71-82, 1997; S. Saksena et al., Biotech. Bioeng., 43, 960-968, 1994; R van Reis et al., J. Membrane Sci., 129, 19-29, 1997; S. Nakao et al., Desalination, 70, 191-205, 1988; U.S. Pat. No. 5,256,294, issued to R. van Reis in 1993; and U.S. Pat. No. 5,490,937, issued to R. van Reis in 1996.

Example 1

(29) A Crossflow Filtration System as described in FIG. 1 was constructed and activated with biofluid from a bioreactor. The cycling of the biofluid through the system results in concentration of the biofluid in the Biofluid container and the collection of waste from the permeate line. Pressurized flow from inline pump 2 is discontinued and countercurrent flow is initiated from an Internal Pump operably linked to said Retentate Flow Line Return and a Sterile Air Source. Valves to the biofluid container are sealed and a Drain line value is opened allowing the flow of concentrated biofluid to drain from the system and be recovered.

(30) To avoid infection of the biofluid, all system components in contact with the biofluid should be suitable sterilized before cultivation. The system or parts of the system may be assembled and sterilized by autoclaving or radiation, or one or more components may be pre-sterilized and assembled in a sterile system. To facilitate assembly, the sterilized system parts or components may be equipped with aseptic connectors, e.g. of the ReadyMate type (GE Healthcare). Alternatively, the sterilized system parts/components may be contained in aseptic packages and assembled in a sterile clean room.

(31) In yet another embodiment, the pressurizing method may also be used to a) recovery fluid at the permeate side of the filter. In this embodiment, a pump is connected to the top connection at the permeate side of the filter and the pressure would push fluid quantitatively through a CFF filter towards the end of the process to allow for quantitative processing.

(32) Thus, while there have been shown, described and pointed out, fundamental novel features of the invention as applied to the exemplary embodiments thereof, it will be understood that various omissions and substitutions and changes in the form and details of devices and methods illustrated, and in their operation, may be made by those skilled in the art without departing from the spirit or scope of the invention. Moreover, it is expressly intended that all combinations of those elements and/or method steps, which perform substantially the same function in substantially the same way to achieve the same results, are within the scope of the invention. Moreover, it should be recognized that structures and/or elements and/or method steps shown and/or described in connection with any disclosed form or embodiment of the invention may be incorporated in any other disclosed or described or suggested form or embodiment as a general matter of design choice. It is the intention, therefore, to be limited only as indicated by the scope of the claims appended hereto.