An investigation of the stability and diffusivity of flexible lipid vesicles for transdermal insulin delivery

Abstract

Flexible lipid vesicles have the potential of complementing or even replacing traditional needle injection methods for insulin delivery. Vesicles are made flexible by the incorporation of a chemical surfactant which may also hinder their stability. We studied the changes in the size and apparent flexibility of vesicles with varying surfactant concentrations over time and the effects these changes have on vesicle diffusion. We found that increased surfactant concentrations lead to greater size fluctuations. In addition, we witnessed a significant decrease in the flexibility of vesicles over six weeks, while the diffusivity of surfactant infused liposomes increased over a single week. Our data suggests that while surfactants are necessary in vesicles for transdermal drug delivery, their long-term stability is uncertain. Using our diffusion data, we developed a model to estimate the insulin delivering capacity of a hypothetical insulin patch which has the potential to stabilize vesicles for extended periods of time.