A composition comprises an oligomer synthesized from a multifunctional monomer, a diol, and an amino acid synthesized by reacting (i) a multifunctional monomer comprising citric acid or triethyl citrate with (ii) a diol to form a reaction product, and further reacting the reaction product with (iii) an amino acid. Examples of the diol include 1,8-octanediol, ethylene glycol, and poly(ethylene glycol). Examples of the amino acid include cysteine and serine. Further, the amino acid is linked as a side group to the oligomer backbone.
