Method of purifying a biological composition and article therefor

1. A method of purifying a biological composition, the method comprising:

a) disposing loose cationic ligand-functionalized staple fibers and a biological composition within a mixing volume of a vessel, wherein the loose cationic ligand-functionalized staple fibers have a modified surface layer comprising a grafted acrylic polymer comprising 10 to 100 percent by weight of a cationically-ionizable monomer unit, and wherein at least a portion of the loose cationic ligand-functionalized staple fibers are fibrillated high-density polyethylene fibers;

b) agitating the biological composition and the loose cationic ligand-functionalized staple fibers while they are in intimate contact with each other within the mixing volume to provide modified fibers and a purified biological composition; and

c) separating at least a portion of the purified biological composition from the modified fibers and any loose cationic ligand-functionalized staple fibers with which it is in contact.

2. The method of claim 1 , wherein the loose cationic ligand-functionalized staple fibers are disposed within the mixing volume before the biological composition is disposed within the mixing volume.

3. The method of claim 1 , wherein step b) is accomplished at least in part using a static mixer.

4. The method of claim 1 , wherein the biological composition contains a synthetic polymer flocculant.

5. The method of claim 1 , wherein the grafted acrylic polymer further comprises a multifunctional monomer unit.

6. The method of claim 1 , wherein the grafted acrylic polymer further comprises 0.1 to 90 percent by weight of at least one nonionizable hydrophilic monomer unit.

7. The method of claim 6 , wherein the nonionizable hydrophilic monomer unit comprises an N-vinyllactam having from 4 to 6 carbon atoms.

8. The method of claim 1 , wherein the cationically-ionizable monomer unit is a divalent monomer unit represented by the formula:

wherein:

R 1 is H or an alkyl group having from 1 to 4 carbon atoms;

R 2 is a divalent alkylene group optionally substituted by a catenary carbonyloxy, carbonylamino, oxycarbonylamino, or ureylene divalent linking group;

each R 3 independently is H or an alkyl group having from 1 to 4 carbon atoms;

R 4 is H or an alkyl group having from 1 to 4 carbon atoms or —N(R 3 ) 2 ; and

X 1 is —O— or —NR 3 —.

9. The method of claim 1 , wherein the cationically-ionizable monomer unit comprises a divalent monomer unit represented by the formula:

wherein:

R 1 is H or an alkyl group having from 1 to 4 carbon atoms;

R 2 is a divalent alkylene group optionally substituted by a catenary carbonyloxy, carbonylamino, oxycarbonylamino, or ureylene divalent linking group; and

each R 3 independently is H or an alkyl group having from 1 to 4 carbon atoms.

10. The method of claim 1 , wherein the vessel comprises a sealed specimen bag.

11. The method of claim 1 , wherein step c) includes depositing at least a portion of the modified fibers and any loose cationic ligand-functionalized staple fibers on a porous substrate.

12. An article for purifying a biological composition, the article comprising:

a vessel having a mixing volume disposed therein; and

loose cationic ligand-functionalized staple fibers disposed within the mixing volume, wherein the loose cationic ligand-functionalized staple fibers have a modified surface layer comprising a grafted acrylic polymer comprising 10 to 100 percent by weight of at least one cationically-ionizable acrylic monomer unit, and wherein at least a portion of the loose cationic ligand-functionalized staple fibers are fibrillated high-density polyethylene fibers.

13. The article of claim 12 , wherein the grafted acrylic polymer comprises a multifunctional monomer unit.

14. The article of claim 13 , wherein the grafted acrylic polymer further comprises 0.1 to 90 percent by weight of at least one nonionizable hydrophilic monomer unit.

15. The article of claim 14 , wherein the nonionizable hydrophilic monomer unit comprises an N-vinyllactam having from 4 to 6 carbon atoms.

16. The article of claim 12 , wherein the cationically-ionizable acrylic monomer unit is represented by the formula:

wherein:

R 1 is H or an alkyl group having from 1 to 4 carbon atoms;

R 2 is a divalent alkylene group optionally substituted by a catenary carbonyloxy, carbonylamino, oxycarbonylamino, or ureylene divalent linking group;

each R 3 is independently H or an alkyl group having from 1 to 4 carbon atoms;

R 4 is H or an alkyl group having from 1 to 4 carbon atoms or —N(R 3 ) 2 ; and

X 1 is —O— or —NR 3 —.

17. The article of claim 12 , wherein the cationically-ionizable monomer unit comprises a divalent monomer unit represented by the formula:

wherein:

R 1 is H or an alkyl group having from 1 to 4 carbon atoms;

R 2 is a divalent alkylene group optionally substituted by a catenary carbonyloxy, carbonylamino, oxycarbonylamino, or ureylene divalent linking group; and

each R 3 independently is H or an alkyl group having from 1 to 4 carbon atoms.

18. The article of claim 12 , wherein the biological composition contains a synthetic polymer flocculant.