Effect of Gamma Irradiation on Pluronic Gels for Ocular Delivery of Ciprofloxacin: in Vitro Evaluation

Gamma irradiation was tested as a method for sterilization of pluronic F-127 gel to be used for ocular delivery of ciprofloxacin (CFX). The effect of gamma irradiation on the properties of pluronic gels was studied at different irradiation doses and pluronic copolymer concentrations. The flow of pluronic gels of different concentrations was non-Newtonian with thixotropic pseudoplastic properties for both non-irradiated and irradiated gels. The viscosities of the irradiated gels increased equally at all doses of irradiation. Deviation from Newtonian flow and degree of pseudoplasticity at different irradiation doses were compared by determination of Farrow’s constant values. The values decreased with increasing of irradiation dose indicating a decrease in the degree of pseudoplasticity while non-Newtonian flow was retained at all tested doses. CFX was unstable in pluronic gels irradiated at high irradiation doses for all pluronic concentrations. However, drug instability due to irradiation was less severe as concentration of pluronic was increased indicating more drug protection as the concentration of copolymer increased. At pluronic concentration of 25% w/v, low irradiation doses namely 15 and 20 kGy did not harm the drug and its concentration in the gel was kept within 98 ± 1.59%. Sterility test on pluronic gel (25% w/v) revealed that irradiation dose at 20 kGy can give a definite sterile product. Release study of CFX from the pluronic gel (25% w/v) showed a significant decrease in drug release after 180 min from irradiated (20 kGy) pluronic gel. The developed formulation could be a viable alternative for the ocular delivery of ciprofloxacin by virtue of its desirable properties.