Synthesis of an Optically Transparent Poly(N-isopropylacrylamide) Based Thermally Gelling Material

Restrictive barriers and efficient clearance mechanisms make delivery of therapeutics to the back of the eye particularly challenging. An optically transparent, thermally gelling copolymer scaffold that can simply be mixed with an active pharmaceutical ingredient of choice and injected directly into the vitreous chamber has been designed. The poly(N-isopropylacrylamide) (PNIPAAm) based copolymer possesses a lower critical solution temperature near body temperature. Incorporating acrylic acid and poly(ethylene) glycol methacrylate into the polymer at optimized ratios modulates the Lower Critical Solution Temperature to transition the aqueous copolymer solution into a volume consistent gel which does not expel water, a common challenge with PNIPAAm based materials. The addition of acryloyloxy dimethyl-γ-butyrolactone to the copolymer enables the polymer to slowly degrade and be cleared from the body. Herein, the synthesis and characterization of the novel copolymer scaffolds is described. A detailed report is provided on the intraocular biocompatibility profile as assessed via in vivo imaging techniques, histology and immunostaining. Overall, the scaffolds were well tolerated in the rodent eye for the duration of the 17-day experiment.