Characterization of Temperature-Sensitive Hydrogels Based on N-Isopropylacrylamide and Novel Crosslinkers
Michael Weir, Joseph M. Antonucci, Francis W. Wang
This paper describes the use of new types of synthesized hydroxylated dimethacrylate monomers as crosslinkers for thermally-sensitive hydrogel networks with potential uses in tissue engineering. An array of 54 different N-isopropylacrylamide (NIPAAm)-based hydrogels were created by systematically altering both the type and concentration of crosslinker used. Cloud point measurements were used as a technique to rapidly screen for hydrogels with lower critical solution temperatures (LCST's) appropriate for tissue engineering applications. Most formed a lightly crosslinked network with LCST's between 28 C and 32 C, which is below physiological temperature. Additionally, gel collapse at 37 C was hindered by the more hydrophilic crosslinkers which served to increase the hydrogen bonding between the gel matrix and water. Finally, a simple pass-fail assay was devised to assess the injectibility of these hydrogels. Within the constraints of this assay, it was found that hydrogels with crosslinker mole fractions of 0.1, 0.05 and 0.025 - regardless which crosslinker was used - were too viscous to be injected in a suitable amount of time without causing physical deterioration of the gel during extrusion. All others were able to be injected.