Topical Drug Delivery to Skin Using STAR Particles

Skin has exceptional barrier properties that severely limit delivery of bioactive compounds for dermatological, cosmeceutical and other applications. As a result, many topically applied drugs are delivered at suboptimal levels, and some dermatological drugs are given systemically, thereby dramatically increasing dose and risk of side effects. To overcome the limitations of conventional delivery systems, we have developed STAR particles, which are millimeter-size particles with micron-scale projections (i.e., microneedles). The STAR particles painlessly puncture superficial skin layers (i.e., up to several hundred microns deep) to increase skin permeability and thereby enhance topical drug delivery.

STAR particles can be incorporated into skin creams, as an inert formulation additive, and applied to the skin similarly to conventional skin products. Because of their simple application method, STAR particles require no training prior to use and can be applied to any size skin surface area. Additionally, STAR particles are fabricated from low-cost, commercially available and safe materials.

To date, STAR particles have been fabricated out of biocompatible materials, such as stainless steel, and validated in excised skin, in vivo animal experiments and initial studies in human subjects. In ex vivo permeability studies, STAR particles dramatically increased delivery of topically applied model drugs with a wide range of physiochemical properties (e.g., molecular weight between 500 to 20,000 Da and partition coefficient, logP, between -3.1 to 2.2). In animal studies, skin permeability to model compounds was similarly increased, and skin treated with STAR particles showed no signs of irritation, erythema or bleeding. Application of STAR particles to human subjects was also well tolerated, with subjects only reporting a mild tingling sensation during STAR particle application. These results indicate that STAR particles may be used to safely increase topical drug delivery and thereby enable new dermatological therapies.