A cross-linkable monomer comprises a fumaric acid functional group having
a first end and a second end, a first spacer group affixed to said first
end and comprising at least repeating unit, a first terminal group
affixed to said first spacer group, a second spacer group affixed to said
second end and comprising at least one ethylene glycol repeating unit,
and a second terminal group affixed to said second spacer group. A
hydrogel formed by cross-linking the present monomer and a method for
making the monomer. A method for forming a hydrogel, comprises the steps
of a) synthesizing a copolymer of poly(propylene fumarate) (PPF) and
poly(ethylene glycol (PEG) so as to produce P(PF-co-EG), b) synthesizing
a PEG-tethered fumarate (PEGF), c) coupling agmatine sulfate to the PEGF
to produce PEGF modified with agmatine (Agm-PEGF), and d) cross-linking
the P(PF-co-EG) from step a) with Agm-PEGF from step c).