Intradermal ballistic delivery of micro-particles into excised human skin for pharmaceutical applications.

A unique form of needle-free drug and vaccine delivery is under investigation. The principle of the concept is to accelerate pharmaceuticals in particle form to a momentum sufficient to penetrate the outer layer of the human skin for a pharmacological effect. The relationship between the key particle impact parameters and particle penetration depth in excised human skin has been experimentally determined. Research devices have been used to deliver particles of a range of radii (0.89-53 microm), and density (1.08-18.2 g/cm3) at controlled and incremental impact velocities between 160 and 640 m/s. Analysis of the particle impact data reveals particle penetration depth as a function of particle density, radius and impact velocity. The experimental relationship provides a criterion for the optimal selection of particle parameters and velocity to target specific layers within the skin. Furthermore, some sources of variability in penetration depth have also been established. The experimental data have also been compared with a mechanistic Unified Penetration Model with good agreement.