Cationic charge modified microporous membranes

• US 5,269,931 A
• Filed: 08/20/1991
• Issued: 12/14/1993
• Est. Priority Date: 09/17/1990
• Status: Expired due to Term

• Current Assignee: Pall Corporation (Danaher Corporation)
• Original Assignee: Gelman Sciences, Inc. (Danaher Corporation)
• Inventors: Sellinger, Alan, Hu, Ho-Pin, Tamashiro, Wesley, Katsnelson, Inessa
• Primary Examiner(s): SPEAR JR, FRANK
• Application Number:
  US07/747,668
• Time in Patent Office: 847 Days
• Field of Search: 204/180.1, 204/180.2, 422/56, 422/58, 422/61, 521/53, 521/54, 210/490, 210/500.39, 210/500.42, 210/500.43, 210/635, 210/638, 264/41, 264/49
• US Class Current: 210/635
• CPC Class Codes: B01D 2323/38 Graft polymerization
• CPC Class Codes: B01D 67/0093 Chemical modification
• CPC Class Codes: B01D 71/68 Polysulfones; Polyethersulfones
• CPC Class Codes: G01N 27/44717 Arrangements for investigating the separated zones, e.g. localising zones
• CPC Class Codes: G01N 33/54386 Analytical elements
• CPC Class Codes: G01N 33/545 Synthetic resin

Abstract

Cationic charged semihydrophobic polyethersulfone (CSfIP) membranes having hydrophilic and semihydrophobic properties are provided, as well as preparation of the same by post-treatment. Typically, as an illustration, a microporous hydrophilic polyethersulfone membrane substrate which contains non-leachable polymeric additive having functional groups is treated in an alkaline solution for simultaneous or sequential reaction with 1) a primary charge modifying agent which is an epichlorohydrin modified polyamine, and 2) a secondary polymeric charge modifying agent containing a positive charge (or for reaction with the primary charge modifying agent alone); then baked until cured at elevated temperature; and finally washed and dried. The CSHP membranes are used in various applications such as the filtration of fluids and the macromolecular transfer of biomolecules either from electrophoresis gels or directly to immobilization on the membrane for hybridization and stripping. The CSHP membranes--unlike conventional charged membranes which typically show a decrease in sensitivity and reprobing performance--retain their sensitivity and reprobing performance and excel in this regard throughout multiple reprobing cycles.

Claims

1. A cationic semihydrophobic charge modified microporous membrane, comprising:

a microporous membrane substrate comprising polyethersulfone and at least one non-leachable polymeric additive selected from polyvinylpyrrolidone and polyethylene glycol, which additive enhances hydrophilicity and has functional groups latently reactive with respective groups of charge modifying agents; and

a primary charge modifying agent comprising polyethyleneimine-epichlorohydrin resin which contains polyamines, can chemically react with electrophile-containing compounds and thus impart a net positive charge, and is chemically grafted to said polymeric additive.

2. A membrane according to claim 1 where the polyethersulfone has the formula ##STR5## where n is an integer from 50 to 150 and the membrane substrate contains said additive in an amount effective to make the charge modified membrane when formed and dried water wettable.

3. A membrane according to claim 1 where the primary charge modifying agent comprises polyethyleneimine-epichlorohydrin resin having the formula ##STR6## where R independently represents hydrogen or a continuation of the polyamine chain and R'"'"' represents --OH or --Cl.

4. A blotting composition, comprising a sample substrate applied to a semihydrophobic charge modified membrane according to claim 1 having an internal surface area and an external surface area, wherein available surfaces of the membrane are coextensively charge modified.

5. The blotting composition as recited in claim 4, wherein the sample substrate comprises a gel.

6. The blotting composition as recited in claim 4, wherein the sample substrate comprises a gel comprising macromolecules selected from the group consisting of DNA, RNA, and proteins.

7. The blotting composition as recited in claim 4, wherein the sample substrate comprises a gel which comprises macromolecules electrophoretically separated into a series of bands.

8. The blotting composition as recited in claim 4, wherein the sample substrate comprises materials capable of being bound by the fixed formal charge of the membrane.

9. The blotting composition as recited in claim 8, wherein said materials comprise amine-containing

10. A method of transferring a biological sample to an immobilizing matrix, comprising applying the sample to a semihydrophobic charge modified membrane according to claim 1.

11. The method recited in claim 10, wherein the biological sample is mixed with a gel and the applying step comprises gel blotting.

12. The method recited in claim 10, wherein the applying step comprises spot-wetting the biological sample to the membrane.

13. The method recited in claim 10, wherein the transferring step comprises electro-transfer of the biological sample to the membrane.

14. The method recited in claim 10, wherein the transferring step comprises capillary-transfer of the biological sample to the membrane.

15. The method recited in claim 10, wherein the membrane comprises polyethersulfone.

16. The method recited in claim 10, wherein the biological sample comprises bacteria.

17. The method recited in claim 10, wherein the biological sample comprises a macromolecule selected from the group consisting of DNA, RNA, and protein.

18. A method of identifying a macromolecule, comprising applying a biological sample which includes the macromolecule to a semihydrophobic charge modified membrane according to claim 1;

transferring the macromolecule to the membrane; and

detecting the macromolecule.

19. The method recited in claim 18, wherein the applying step comprises spot-wetting the biological sample to the membrane.

20. The method recited in claim 18, wherein the applying step comprises gel blotting.

21. The method recited in claim 18, wherein the macromolecule is transferred by capillary action.

22. The method recited in claim 18, wherein the macromolecule is transferred by applying an electrical current to the biological sample.

23. The method recited in claim 18, wherein the detecting step is accomplished by ELISA.

24. A dot-blot method, comprising applying a biological sample, which includes a macromolecule selected from the group consisting of DNA, RNA, and protein to a semihydrophobic charge modified membrane according to claim 1;

and transferring the macromolecule to the membrane.

25. The method recited in claim 24, additionally comprising detecting the macromolecule.

26. A method of colony hybridization, comprising applying a biological sample comprising bacteria to a semihydrophobic charge modified membrane according to claim 1;

transferring the bacteria to the membrane; and

detecting the bacteria on the membrane.

27. A cationic semihydrophobic charge modified microporous membrane, comprising:

a microporous membrane substrate comprising polyethersulfone and at least one non-leachable polymeric additive selected from polyvinylpyrrolidone and polyethylene glycol, which additive enhances hydrophilicity and has functional groups latently reactive with respective groups of charge modifying agents; and

a primary charge modifying agent comprising polyethyleneimine-epichlorohydrin resin which contains polyamines, can chemically react with electrophile-containing compounds and thus impart a net positive charge, and is chemically grafted to said polymeric additive.

a secondary charge modifying agent containing functionality that is reactive with the primary charge modifying agent, selected from the group consisting of partially phosphinated polyvinylbenzyl chloride, ammonium and sulfonium analogs thereof, and quaternized poly(dimethylamine-co-epichlorohydrin), said secondary agent being reacted with the primary agent in an amount either such that the magnitude of the final formal positive charge is increased over that due to its reaction with the primary agent or such that the sensitivity of the primary agent to the variance of environmental pH is decreased.

28. A membrane according to claim 27 where the polyethersulfone has the formula ##STR7## where n is an integer from 50 to 150 and the medium contains said additive in an amount effective to make the charge modified membrane when formed and dried water wettable.

29. A membrane according to claim 27 where the primary charge modifying agent comprises polyethyleneimine-epichlorohydrin resin having the formula ##STR8## where R independently represents hydrogen or a continuation of the polyamine chain and R'"'"' represents --OH and --Cl.

30. A membrane according to claim 27 where the secondary charge modifying agent comprises a partially phosphinated polyvinylbenzyl chloride having the formula ##STR9## where m and n are integers indicating the polymer length and R" independently represents a lower alkyl group or an aryl group;

or an ammonium or sulfonium analog of said phosphinated benzyl chloride.

31. A membrane according to claim 27 where the secondary charge modifying agent comprises a quaternized poly(dimethylamine-co-epichlorohydrin) having the formula ##STR10## where R""" is a continuation of the polymer chain.

32. A process for preparing a semihydrophobic cationic charge modified microporous membrane comprising:

A. providing a microporous membrane substrate comprising polyethersulfone and at least one non-leachable polymeric additive selected from polyvinylpyrrolidone and polyethylene glycol, which additive enhances hydrophilicity and has functional groups latently reactive with reactive groups of charge modifying agents;

B. reacting the membrane substrate with a primary charge modifying agent comprising polyethyleneimineepichlorodydrin resin by means including baking, said agent being reacted in an amount conferring a positive fixed formal charge to said membrane substrate when cured; and

C. washing and drying the resulting charge modified membrane.

33. A process according to claim 32 wherein the polyethersulfone has the formula ##STR11## where n is an integer from 50 to 150 and the membrane substrate contains said additive in an amount effective to make the charge modified membrane when formed and dried water wettable.

34. A process according to claim 32 where the charge modifying agent comprises polyethyleneimine-epichlorohydrin resin having the formula ##STR12## where R independently represents hydrogen or a continuation of the polyamine chain and R'"'"' represents --OH or --Cl.

35. A process for preparing a cationic semihydrophobic charge modified membrane comprising:

A. providing a microporous membrane substrate comprising polyethersulfone and at least one non-leachable polymeric additive selected from polyvinylpyrrolidone and polyethylene glycol, which additive confers hydrophilicity and has functional groups latently reactive with reactive groups of charge modifying agents;

B. reacting the membrane substrate with a primary charge modifying agent comprising polyethyleneimine-epichlorohydrin resin in an amount conferring a positive fixed formal charge to said membrane substrate;

C. reacting the primary charge modifying agent with a secondary charge modifying agent containing functionality that is reactive with the primary charge modifying agent, selected from partially phosphinated polyvinylbenzyl chloride, ammonium and sulfonium analogs of said phosphinated benzyl chloride, and quaternized poly(dimethylamine-co-epichlorohydrin), said secondary agent being reacted with the primary agent in an amount either such that the magnitude of the final formal positive charge is increased over that due to its reaction with the primary agent or such that the sensitivity of the primary agent to the variance of environmental pH is decreased; and

D. washing and drying the resulting charge modified membrane.

36. A process according to claim 35 where the polyethersulfone has the formula ##STR13## where n is an integer from 50 to 150 and the medium contains said additive in an amount effective to make the charge modified membrane when formed and dried water wettable.

37. A process according to claim 35 where the primary charge modifying agent comprises polyethyleneimine-epichlorohydrin resin having the formula ##STR14## where R represents hydrogen or a continuation of the polyamine chain and R'"'"' represents --OH or --Cl.

38. A process according to claim 35 where the secondary charge modifying agent has the formula ##STR15## where m and n are integers indicating the polymer length and R" independently represent a lower alkyl group or an aryl group;

or an ammonium or sulfonium analog of said phosphinated benzyl chloride.

39. A process according to claim 35 where the secondary charge modifying comprises a quaternized poly(dimethylamine-co-epichlorohydrin) having the formula ##STR16## were R""" is a continuation of the polymer chain.