Studies on the Synthesis and Characterization of Encapsulated Organogels for Controlled Drug Delivery Applications

Abstract

Over the years, biopolymeric microparticles have been associated with the leaching of the internal phase. The present work was aimed at developing a new strategy in negotiating the problem of leaching from the microparticles. We hypothesized that gelation of the internal phase as organogels (core) and their encapsulation within the alginate microparticles may prevent leaching. Organogels were prepared using natural fatty acyl sources and synthetic source. Natural sources include vegetable fats (cocoa butter, mango butter), animal fat (lanolin) and fatty acid having both plant and animal origin (stearic acid), whereas, synthetic source include the mixture of Span 80 and Tween 80. Prior to encapsulation, the physicochemical, thermal and mechanical properties of the organogels were characterized in depth. The gelation mechanism and crystallization phenomenon during the formation of vegetable fat and stearic acid based organogels were critically evaluated. The predicted gelation mechanism in vegetable fat based organogels is instantaneous nucleation coupled with one or two dimensional growth of the fat crystals. On the other hand, stearate molecules followed heterogeneous nucleation coupled with one-dimensional growth during the formation of stearate organogels. The aforementioned organogels were encapsulated within the alginate microparticles by ionotropic gelation method. Microscopic, XRD and DSC studies confirmed the successful encapsulation of organogels as the core material of the developed microparticles. The organogel encapsulated microparticles prevented the leaching of the internal phase and improved the drug encapsulation efficiency. Presence of semi-solid organogels as the core material facilitated the controlled release of the drugs (model drugs: metronidazole and ciprofloxacin in stearate formulations) from the microparticles. The developed formulations showed good antimicrobial properties against Escherichia coli. The microparticles were found to be biocompatible and mucoadhesive in nature when checked against mammalian L929 fibroblast cells and goat’s small intestine, respectively. Based on the results, it was concluded that the developed formulations (organogels and microparticles) may be used as the controlled drug delivery vehicles for in vivo applications.