In some aspects, the present disclosure provides a system for forming a hydrogel that comprises: a reactive multi-arm polymer that comprises three or more polymer arms linked to a core region, at least three of the three or more polymer arms comprising a cyclic-imidyl ester group, a hydrolysable ester group, an iodinated lactone residue, an amide group and a hydrophilic polymer segment, where the cyclic-imidyl ester group is linked to the iodinated lactone residue through the hydrolysable ester group, the iodinated lactone residue is linked to the hydrophilic polymer segment through the amide group, and the hydrophilic polymer segment is linked to the core region; and a polyamino compound comprising at least two amino (NH.sub.2) groups, wherein the reactive multi-arm polymer and the polyamino compound react to form a crosslinked hydrogel. Other aspects pertain to crosslinked hydrogels formed from such systems and methods of treatment using such systems.