Gelation of photopolymerized hyaluronic acid grafted with glycidyl methacrylate

Experiments have tracked the ambient gelation of a series of hydrophilic hyaluronic acid (HA) resins grafted with glycidyl methacrylate (GM) and photopolymerized as a function of dose. The resin mixtures range in GMHA concentration between 0.5 and 1.5% w/w in phosphate buffered saline (PBS). Illuminated at 20 mW/cm2, the dynamic viscosity (η(t)) has been tracked and characterized using the Boltzmann log-sigmoidal model. A gelled viscosity of ~ 10 Pa s was determined at 0.5% w/w which rose to ~ 50 Pa s at or above 1% w/w. More curing agent marginally increased the gel viscosity at each concentration. Time constants associated with viscosity advancement were shortest at [GMHA] = 1.0%; higher concentrations are attributed with lower quantum efficiency when illuminated. Subsequent frequency sweeps replicated already published work using similar GHMA concentrations in PBS. G′ values ranged from 100 to 500 Pa over the formulation range with expected sensitivity to GMHA and curing agent concentration. Overall, the sigmoidal model represented this advancing viscosity data well, and further analysis of the physical significance of these model parameters may help in understanding photopolymerization of this complicated formulation more broadly.

► The ambient dynamic viscosity of photopolymerized GMHA gels has been measured.
► 2 physical parameters and two time constants were extracted from the sigmoidal model.
► Higher crosslinker content for a fixed GMHA concentration led to higher gel viscosity.
► The time to toggle between the initial and final viscosity ranged between 5 and 10 s.
► Dynamic frequency sweep tests on cured gels also revealed G′ values between 100 and 500 Pa.