Nano Drug Delivery Formulations for Topical Dermal Administration of L-Ascorbic Acid and Derivatives

This review considers L-ascorbic acid as a test substance in designing a dermal drug delivery system for carrying a hydrophilic, low-stability API. Actual studies of nano delivery systems carrying L-ascorbic acid are reviewed. L-ascorbic acid and other antioxidant substances are present in the skin at high levels compared with blood plasma. Augmenting these L-ascorbic acid levels by topical administration may have benefit, but other antioxidants may also need to be augmented. Coadministration of other APIs with L-ascorbic acid may be beneficial, but synergetic interactions are rare and difficult to predict. Some studies reviewed used in vitro methods for quantifying skin retention of API in the living skin layers. These methods may be inadequate. In vivo mouse and rat models suggest therapeutic value of L-ascorbic acid in the skin, but since these animal skins are more permeable than human skin, evidence for good API retention in human skin is weak. Studies using inorganic or polymer nanoparticles for L-ascorbic acid include a lack information concerning skin permeability and retention. Liposome-like systems seem to be the main focus of research now. These studies challenge the understanding of skin penetration mechanisms. Predictions that positively charged deformable liposomes are superior to negatively charged non-deformable liposomes fail.