(594c) Hydrogels for Long-Term Release of Intact Insulin

Our group has developed novel hydrogels consisting of thermoresponsive and hydrolytically degradable properties for long-term release of low dose insulin to the retina to retard the development and progression of early diabetic retinopathy. Diabetic retinopathy involves retinal neuronal cell loss which leads to vision loss. The hydrogels were formulated by UV photopolymerization of N-isoprpylacrylamide and a cross-linkable macromer, 2-hydroxyethylmethacrylate-lactate-dextran in dimethyl formamide. Lispro insulin (Humalog®) was loaded during the process of hydrogel synthesis. Stability of lispro insulin released from the hydrogel in phosphate buffered saline, PBS, (pH 7.4) at 37 °C was studied by using Waters Acquity Ultra Performance Liquid Chromatography (UPLC) system. A Waters Acquity UPLC® BEH C18 1.7 um (2.1 x 50mm) column and UV detector set at 214 nm were used for separation and detection, respectively, of lispro insulin. A mixture of acetonitrile and water was used as mobile phase and a gradient of acetonitrile was applied to elute lispro insulin. The presence of pentaerythritiol triacrylate and 2-aminoethyl methacrylate in the hydrogels stabilized lispro insulin as the duration of release of stable insulin doubled compared to the release from hydrogels without these two components. Conventional protein stabilizers, such as polyethylene glycol, polyvinyl alcohol, and pluronic F127, did not play any role in stabilizing lispro insulin in PBS at 37 °C. Similarly, zinc chloride and glutamic acid, known insulin stabilizers, did not improve lispro insulin stability. Glycerin and meta-cresol individually enhanced lispro insulin stability in solution. Role of these two species conjugated to hydrogels in stabilizing lispro insulin is under investigation.