Cold Emulsified Nanoemulsion: Enhancing Delivery and Stability of Thermolabile Acyclovir

Abstract

Acyclovir is an acyclic purine nucleoside widely used as an antiviral agent with good topical efficacy. Acyclovir is a thermolabile drug, making it challenging to formulate a stable and effective emulsion via a conventional emulsification process. This study aims to develop, optimize, and characterize the nanoemulsion of thermolabile drug acyclovir, manufactured by adopting a cold emulsification process and compare the physicochemical properties and diffusion pattern with a leading marketed formulation. Diffusion studies were conducted using Franz diffusion cells. The optimized formulation was subjected to quantitative estimation of acyclovir, impurity profiling, viscosity, pH, vesicle size, shape, and polydispersibility index (PDI). In the current study, the particle size of the nanoemulsion varies from 66.25 to 244.40 nm, and the zeta potential revealed a high negative surface charge on the particles. Transmission electron microscopy images revealed spherical-shaped, non-aggregated, and discrete globules. The in-vitro diffusion study of acyclovir nanoemulsion showed enhanced penetration efficacy than the conventional emulsion. All these observations signified that the cold emulsification process for manufacturing nanoemulsion is appropriate for thermolabile and pH-sensitive drugs. The study demonstrates enhanced stability and efficacy of optimized acyclovir nanoemulsion through cold emulsification.