Nano-engineered electro-responsive drug delivery systems

Stimuli-responsive drug delivery systems can release therapeutic agents when actuated by an appropriate stimulus, whether endogenous or exogenous. Interestingly, exogenous stimuli are completely dissociated from the patient's physiology and can be precisely controlled externally in magnitude, in space, and in time. They can therefore constitute more reproducible means of controlling the release of therapeutics from appropriately responsive delivery systems. One stimulus which has long attracted attention is the application of an electric potential, and most electro-responsive drug delivery systems reported to date have been based on intrinsically conducting polymers. These systems, however, are limited by slow drug release and low drug loading. These challenges are currently driving the development of new electro-responsive delivery systems with higher responsiveness and drug loading, by implementing concepts of nano-engineering into their structure. This review will focus on this exciting and most recent direction taken in this field by first discussing drug delivery from electro-responsive films containing nano-scaled features, and then nanoscale dispersed/colloidal electro-responsive drug delivery systems, such as nanoparticles, micelles, and vesicular structures.