In a process for forming a hydrogel, a precursor crosslinkable through disulfide bonds for forming the hydrogel is provided in a solution. The precursor comprises a branched molecular structure, which comprises a plurality of branches. At least three of the branches each comprises a disulfide bond. The pH in the solution is adjusted to initiate thiol-disulfide exchange in the precursor, thus crosslinking the precursor through disulfide bonds formed by thiol-disulfide exchange. After the precursor is sufficiently crosslinked to form a hydrogel, the pH in the solution is adjusted to inhibit further thiol-disulfide exchange in the hydrogel. Further, a hydrogel matrix may comprise a polymer substantially crosslinked through disulfide bonds. The polymer may comprise a hydrophobic poly(amido amine) core and an amino-functionalized hydrophilic shell.
