Design and optimization of metformin solid lipid microparticles for topical application

This study aimed to improve metformin skin administration by creating solid lipid microparticles (SLMs). To obtain optimal metformin delivery, SLMs were created using a double emulsion hot homogenization technique with a rotor-stator. The effects of the two surfactants and homogenization time on particle characteristics and performance were studied using Response Surface Methodology (RSM). Tween 60 concentration had the most significant effect on particle size. The simple effects of the studied factors did not significantly affect encapsulation efficiency. However, the interactions between these parameters influenced this response. Moreover, the particle size was affected more by the surfactant concentration. After optimizing the three factors, the results showed an optimum encapsulation efficiency of 82% and a particle size of 2 µm with a desirability of 0.915. The topical drug release profile of lipid microparticle suspensions is characterized by an early burst, followed by sustained drug release. The release of metformin from solid lipid particles followed the Higuchi release model, whereas it followed the Weibull model for release from the gel formulation. Based on the in vitro drug release results, we can conclude that the particles containing the drug are in the shape of a matrix.

Practical Applications: The SLM formulation produces a film on the cutaneous surface, retaining the active component in the skin's superficial layer. Furthermore, owing to their micron size, SLM increases the contact surface of the encapsulated drug with the stratum corneum, which might improve cutaneous delivery and provide sustained release of the drug.