Transdermal Cubic Phases of Metformin Hydrochloride: In Silico and in Vitro Studies of Delivery Mechanisms.

Transdermal delivery is one of important controlled drug release strategies for drug development. Cubic phases are the assemblies of amphiphilic molecules in water with the hydrophilic-hydrophobic interpenetrating network for transdermal delivery of both hydrophilic and hydrophobic drugs. However, many details about the transdermal delivery of drugs from cubic phases remain unclear. Here, metformin hydrochloride (Met) cubic phases were prepared with glyceryl monooleate (GMO), ethanol, and water. The cubic structure was identified with the polarizing light microscopy and small-angle X-ray scattering method. Dissipative particle dynamics (DPD) was used for building the microstructures of the cubic phases to explore the mechanism of drug release that mainly depended on drug diffusion from the water channels of cubic phases in accordance with the Higuchi equation of in vitro release experiments. The coarse-grained model and molecular docking method showed that GMO could enhance drug permeation through the skin by disturbing the interaction between Met and the skin proteins, and increasing the fluidity of skin lipids, which was confirmed with the Fourier transform infrared spectroscopy, Langmuir monolayer, and immunohistochemistry. Furthermore, in vitro permeation experiments showed the high Met transdermal improvement of cubic phases. Cubic phases are an ideal transdermal delivery system of Met. In silico methods are very useful for analyzing the molecular mechanisms of transdermal formulations.