Control and prediction of gelation kinetics in enzymatically cross-linked poly(ethylene glycol) hydrogels

We demonstrate control of gelation kinetics in formation of poly(ethylene g lycol) (PEG) hydrogels by enzymatic cross-linking. A predictive model for g elation kinetics based on macromer structure and composition, stoichiometri c ratios of reactants, cross-linking enzyme concentration, and the underlyi ng kinetics of enzyme reaction was developed on the basis of classical Flor y-Stockmayer theory. Experiments with substrate-functionalized multiarm com b PEG showed good agreement with theory upon variation of the enzyme concen tration, with a slight overprediction in the time to gelation. Experiments with a substrate-functionalized difunctional PEG in conjunction with a poly peptide where macromer concentrations were varied were also consistent with theory, but with a slight underprediction of gelation time.