Crosslinked zwitterionic hydrogels

1. A crosslinked hydrogel, comprising a crosslinked polymer having repeating units and a plurality of crosslinks, wherein each crosslink is represented by the formula:

wherein

R 1 and R 2 are independently selected from the group consisting of hydrogen, fluorine, trifluoromethyl, C1-C6 alkyl, and C6-C12 aryl groups;

R 3 is selected from the group consisting of C1-C6 alkyl, C6-C12 aryl, CH 2 ═C(R 1 )-L 1 -, CH 2 ═C(R 2 )-L 2 -, or R 3 is the residual portion of a third crosslink, -L 1 -CR 1 —CH 2 — or -L 2 -CR 2 —CH 2 —;

L 1 and L 2 are independently selected from the group consisting of —C(═O)O—(CH 2 ) n — and —C(═O)NH—(CH 2 ) n —, wherein n is an integer from 1 to 20;

L 3 is —(CH 2 ) n —, where n is an integer from 1 to 20;

A 1 is C, S, SO, P, or PO;

x is an integer from about 5 to about 10,000;

X − is the counter ion associated with the N + cationic center; and

M + is a counterion associated with the (A=O)O − anionic center.

2. The hydrogel of claim 1 , wherein R 1 , R 2 , and R 3 are independently selected from the group consisting of C1-C3 alkyl.

3. The hydrogel of claim 1 , wherein L 1 and L 2 are —C(═O)O—(CH 2 ) n —, wherein n is 1-6.

4. The hydrogel of claim 1 , wherein L 3 is —(CH 2 ) n —, where n is an integer from 1-6.

5. The hydrogel of claim 1 , wherein A 1 is C or SO.

6. The hydrogel of claim 1 , wherein M + at each occurrence is a metal or organic ion.

7. The hydrogel of claim 1 , wherein X − at each occurrence is selected from the group consisting of halide, carboxylate, alkylsulfonate, sulfate, nitrate, perchlorate, tetrafluoroborate, hexafluorophosphate, trifluoromethylsulfonate, bis(trifluoromethylsulfonyl)amide, lactate, and salicylate.

8. The hydrogel of claim 1 , wherein x is an integer from about 10 to about 1,000.

9. The hydrogel of claim 1 , wherein the hydrogel is a gradient hydrogel.

10. A surface of a substrate, wherein the surface comprises a hydrogel of claim 1 .

11. The surface of claim 10 , wherein the substrate is selected from the group consisting of a medical device, a glucose sensor, a particle, a drug carrier, non-viral gene delivery system, a biosensor, a membrane, an implantable sensor, a subcutaneous sensor, an implant, and a contact lens.

12. The surface of claim 11 , wherein the particle is a nanoparticle.

13. The hydrogel of claim 1 , further comprising a particle encapsulated therein.

14. The hydrogel of claim 13 , wherein the particle is a nanoparticle.

15. The hydrogel of claim 14 , wherein the nanoparticle has a diameter of about 5 nm to about 200 nm.

16. The hydrogel of claim 14 , wherein the nanoparticle is a gold nanoparticle.

17. The hydrogel of claim 14 , wherein the nanoparticle is a polymer-coated nanoparticle.

18. The hydrogel of claim 17 , wherein the nanoparticle is coated with a polymer comprising carboxybetaine methacrylate (CBMA) or oligo(ethylene glycol) methyl ether methacrylate (OEGMA).

19. The hydrogel of claim 1 , wherein each repeating unit has the formula:

wherein

R 4 is selected from the group consisting of hydrogen, fluorine, trifluoromethyl, C1-C6 alkyl, and C6-C12 aryl groups;

R 5 and R 6 are independently selected from the group consisting of hydrogen, alkyl, and aryl, or taken together with the nitrogen to which they are attached form a cationic center;

L 4 is a linker that covalently couples the cationic center [N + (R 5 )(R 6 )] to the polymer backbone [—(CH 2 —CR 4 ) n —];

L 5 is a linker that covalently couples the anionic center [A 2 (═O)—O − ] to the cationic center;

A 2 is C, S, SO, P, or PO;

M + is a counterion associated with the (A 2 =O)O − anionic center;

X − is a counter ion associated with the cationic center;

n is an integer from 5 to about 10,000.

20. The hydrogel of claim 19 , wherein R4, R5, and R6 are independently selected from the group consisting of C1-C3 alkyl.

21. The hydrogel of claim 19 , wherein L4 is selected from the group consisting of —C(═O)O—(CH2)n- and —C(═O)NH—(CH2)n-, wherein n is an integer from 1 to 20.

22. The hydrogel of claim 19 , wherein L5 is —(CH2)n-, where n is an integer from 1 to 20.

23. The hydrogel of claim 19 , wherein n is an integer from 10 to about 1,000.

24. The hydrogel of claim 19 , wherein M+ at each occurrence is a metal or organic ion.

25. The hydrogel of claim 19 , wherein X— at each occurrence is selected from the group consisting of halide, carboxylate, alkylsulfonate, sulfate, nitrate, perchlorate, tetrafluoroborate, hexafluorophosphate, trifluoromethylsulfonate, bis(trifluoromethylsulfonyl)amide, lactate, and salicylate.