Alginate hydrogel compositions

1. A semi-permeable hydrogel composition comprising an alginate that forms an alginate matrix comprising a periphery, wherein the periphery of the alginate matrix is covalently crosslinked to a multi-armed water soluble polymer that comprises polyethylene glycol or poly(2-methacryloyloxy ethyl phosphorylcholine), wherein the multi-armed water soluble polymer forms a covalently crosslinked surface layer on the alginate matrix, and wherein the covalent crosslink of the multi-armed water soluble polymer and the alginate comprises a linkage that is a product of a first click-reactive functional group of the multi-armed water soluble polymer and a second click-reactive functional group of the alginate.

2. The semi-permeable hydrogel composition of claim 1 , wherein the hydrogel composition further comprises 1-20 surface layers of alginate that is covalently crosslinked to the multi-armed water soluble polymer.

3. The semi-permeable hydrogel composition of claim 1 , wherein the hydrogel composition further comprises a biocompatible surface layer, wherein the biocompatible surface layer is covalently bonded to the semi-permeable hydrogel composition.

4. The hydrogel composition of claim 1 , wherein the hydrogel composition is stable for at least 30 days at 40° C. in 1 mM phosphate buffered saline.

5. The hydrogel composition of claim 4 , wherein the composition is characterized by a first tan delta value determined at the time the composition is subjected to storage at 40° C. in 1 mM phosphate buffered saline (day 0), and a second tan delta value determined after the composition has been stored for 30 days at 40° C. in 1 mM phosphate buffered saline; and wherein the first tan delta value and the second tan delta value are the same or differ by no more than about 0.05.

6. The hydrogel composition of claim 4 , wherein the hydrogel maintains its semi-permeability after storage for 30 days at 40° C. in 1 mM phosphate buffered saline.

7. The semi-permeable hydrogel composition of claim 1 , wherein the composition is permeable to molecular species that have a molecular weight of up to about 100 kDa, and is impermeable to larger molecular species.

8. The hydrogel composition of claim 1 , wherein the alginate is in a matrix comprising a divalent cation selected from the group consisting of Ca 2+ , Cu 2+ , Ba 2+ , Sr 2+ , Mg 2+ , and combinations thereof.

9. The hydrogel composition of claim 1 , wherein the multi-armed water soluble polymer is a multi-armed polyethylene glycol having from 3 to 10 arms, and wherein:

i) the multi-armed water soluble polymer has a weight average molecular weight in a range from about 1,000 to about 100,000 Daltons; or

ii) the alginate has a weight average molecular weight in a range from about 10,000 to about 300,000 g/mol.

10. The hydrogel composition of claim 1 , wherein

i) about 3 mol % to about 50 mol % of the alginate comprises the second functional group; and

ii) the second functional group is selected from azide and tetrazine; the first functional group is selected from a dibenzyl cyclooctyne amine and norbornene; and the covalent crosslinks are formed by virtue of a cycloaddition reaction between the first and second functional groups.

11. The hydrogel composition of claim 1 , wherein the alginate is in a matrix further comprising within the matrix, a pharmacologically active material.

12. The hydrogel composition of claim 11 , wherein the pharmacologically active material is selected from the group consisting of proteins, polynucleotides, and small molecules.

13. The hydrogel composition of claim 1 , wherein the alginate is in a matrix further comprising living cells within the matrix, wherein:

i) the living cells are autologous cells, allogeneic cells or xenogeneic cells;

ii) the living cells are induced pluripotent stem-cell derived cells, induced pluripotent stem-cell derived pancreatic progenitor cells, platelets, T-Cells, CAR-T cells, cardiac myoblasts, genetically modified APRE-19 cells, pancreatic cells or dermal cells; or

iii) the living cells are hormone, cytokine, or growth factor secreting cells.

14. The hydrogel composition of claim 1 , in a form selected from the group consisting of a bead, capsule, sheet, membrane, thread, fiber, filament, particle, sponge, mesh, foam, scaffold and composites of any of the foregoing.

15. The semi-permeable hydrogel composition of claim 1 , wherein the multi-armed water soluble polymer comprises poly(2-methacryloyloxy ethyl phosphorylcholine).

16. The semi-permeable hydrogel composition of claim 1 , wherein the multi-armed water soluble polymer comprises a copolymer of (2-methacryloyloxyethyl phosphorylcholine) and lysine methacrylamide.

17. A semi-permeable hydrogel composition comprising an alginate that forms an alginate matrix comprising a periphery, wherein the periphery of the alginate matrix is covalently crosslinked to a multi-armed water soluble polymer that is polyethylene glycol or poly(2-methacryloyloxy ethyl phosphorylcholine), wherein the multi-armed water soluble polymer forms a covalently crosslinked surface layer on the alginate matrix, wherein the covalent crosslink of the multi-armed water soluble polymer and the alginate comprises a linkage that is a product of a first click-reactive functional group of the multi-armed water soluble polymer and a second click-reactive functional group of the alginate, wherein the hydrogel composition is stable for at least 30 days at 40° C. in 1 mM phosphate buffered saline, wherein the composition is characterized by a first tan delta value determined at the time the composition is subjected to storage at 40° C. in 1 mM phosphate buffered saline (day 0), and a second tan delta value determined after the composition has been stored for 30 days at 40° C. in 1 mM phosphate buffered saline; and wherein the first tan delta value and the second tan delta value are the same or differ by no more than about 0.05.