Design and Evaluation of Natamycin Nanocrystals Loaded In Situ Gel for Ophthalmic Administration

Background: Natamycin belongs to a large group of naturally occurring polyene antifungal antibiotics derived from Streptomyces natalensis. Natamycin has a restrictive pharmaceutical role because of its extremely low aqueous solubility, which severely reduces the bioavailability of the drug. To improve the absorption of the drug, nanocrystals of natamycin were prepared and incorporated into in situ gel.

Aim: To improve the solubility and absorption of natamycin nanocrystals by preparing nanocrystal in situ gel of natamycin for ophthalmic delivery

Methodology: Natamycin nanocrystal was prepared using Sono-Precipitation method. Box-Behnken approach was employed to assess the influence of independent variables, namely concentration of stabilizer, sonication time and amplitude on particle size and zeta potential of the prepared nanocrystal.

Optimized natamycin nanocrystal in situ gel formulations was characterized for various parameters like pH, viscosity, drug content, in vitro drug release and ex vivo permeation studies.

Results: The optimized formulation of natamycin nanocrystal with a particle size of 293.9nm and zeta potential -14.6mV was incorporated into in situ gels. The pH triggered in situ gel was prepared using Carbopol and Hydroxypropyl methylcellulose (HPMC)., which showed clear preparation, pH of the formulation was closed to the pH of tear fluid, i.e., 7.4, viscosity showed pseudoplastic behaviour with immediate gelation remained for an extended period, and the drug content was around 99.70%. From the characterizations given above, PF-4 was optimized and evaluated for In vitro drug release showing slow and sustained release when compared to the marketed formulation and followed first-order kinetics with the diffusion-controlled mechanism. Ex vivo permeation through goat's cornea of PF-4 showed better permeation than marketed formulation. The stability studies of PF-4 showed that formulation was stable at the appropriate condition.

Conclusion: Nanocrystals formulations of natamycin was successfully formulated and incorporated into in situ gels. Further in vivo studies need to be carried out for confirmation of pharmacological activity