In some aspects, the present disclosure provides a radiopaque, reactive polymer comprising one or more hydrophilic polymer regions, the one or more hydrophilic polymer regions having first and second ends and comprising at least one hydrophilic polymer segment, a plurality of iodinated amino-acid residues, wherein at least one of the plurality of iodinated amino-acid residues is linked to each of the hydrophilic polymer regions, and a plurality of reactive moieties, wherein at least one of the plurality of reactive moieties is linked to each of the plurality of iodinated amino-acid residues and wherein the reactive moieties each comprise an electrophilic group. In other aspects the present disclosure pertains to systems that comprise such a radiopaque, reactive polymer and a compound having a plurality of nucleophilic moieties that reacts with the radiopaque, reactive polymer to form a crosslinked reaction product, as well as methods of treatment using the same.