Ligand graft functionalized substrates
Polyethyleneimine and polyalkylene biguanide ligand functionalized substrates, methods of making ligand functionalized substrates, and methods of using functionalized substrates are disclosed.
1. A filter element comprising two or more layers of a porous thermoplastic ligand functionalized substrate and extending from the surfaces thereof free-radically grafted biguanide ligand groups to form a free-radically-grafted substrate, wherein the free-radically grafted substrate is of the formula:
Substrate˜(M ligand ) m , where Substrate represents the porous thermoplastic substrate, M ligand and represents a polymerized grafted ethylenically unsaturated monomer having pendant biguanide ligand groups, and m is at least two;
wherein said pendent biguanide ligands groups are selected from one or more of the formula:
wherein
R 2 is an arylene or alkylene and a is at least one.
2. The filter element of claim 1 wherein the grafted ligand groups comprise the reaction product of a free-radically grafted electrophilic functional group and a ligand compound:
wherein
each R 4 is individually H, alkyl or aryl,
each R 6 is individually alkylene or arylene,
c may be zero or an integer from 1 to 500, and
d is zero or 1, with the proviso that when d is zero, then c is 1 to 500.
3. The article of claim 1 , wherein the porous substrate is selected from a porous membrane, porous non-woven web, or porous fiber.
4. The article of claim 1 further comprising free-radically grafted ionic or hydrophilic groups.
5. The article of claim 4 , further comprising free-radically grafted quaternary ammonium groups on the surface of the substrate.
6. The filter element of claim 1 wherein the individual layers have different porosity.
7. The filter element of claim 1 wherein the individual layers have different degrees of grafting by the grafting monomers.
8. The filter element of claim 1 further comprising an upstream prefilter layer and/or a downstream support layer.
9. The filter element of claim 1 wherein the individual filter elements are pleated.
10. The filter element of claim 1 wherein the pore size of the porous substrate is from 0.1 to 10 μm.
11. A filter cartridge comprising the filter element of claim 1 .
12. A method of filtration comprising the steps of:
a) providing the filter element comprising two or more layers of the ligand functionalized base substrate of claim 1 , and
b) allowing a moving biological solution containing a target biomaterial and other biological materials to impinge upon the upstream surface of the filter element for a time sufficient to effect separation of the target biomaterial from the solution.
13. The method of claim 12 yielding a log-reduction value (LRV) of at least 1.0 for neutral viruses.
14. The method of claim 12 yielding a log-reduction value (LRV) of at least 5.0 for neutral viruses.
15. The method of claim 12 wherein the solution comprises from 0 to about 150 mM salt.
16. The method of claim 12 wherein the other biological material is a positively charged monoclonal antibody and the target biomaterial is negatively charged so the target biomaterial binds to the ligand functionalized substrate.
17. The method of claim 16 wherein the target biomaterial is selected from viruses, host cell proteins, and nucleic acids.