Transdermal ballistic delivery of micro-particles: investigation into skin penetration

This paper describes investigations into the impact of model micro-particles into excised human skin. This work is aimed at optimising a unique form of transdermal drug delivery, based on PowderJect^(R) devices. These devices work by accelerating drugs in micro-particle form to a velocity at which they will enter the skin. Not only are PowderJect^(R) devices painless and needle-free; by the manipulation of penetration depth, existing therapeutic compounds can be made to work much more effectively. A research device was designed to deliver particles to the skin at conditions with nominally uniform velocities. Glass, polystyrene and steel micro-spheres were used to simulate drug payloads. The results of these investigations show that penetration depth into skin is a function of particle density, radius and entry velocity. This relationship provides a criterion for the optimal selection of particle parameters and entry velocity to target specific layers within the skin. The experimental data is compared to both a theoretical and an empirical model with good agreement