Precise laser poration to control drug delivery into and through human nail

Drug treatment of diseases of the human nail remains a difficult challenge; topical therapy, in particular, is limited by very poor transport of active agents across the nail itself. The objective of this research was to examine the potential of controlled, and fibre-optic delivered, femtosecond laser light pulses to provide new pathways and opportunities for drug access to targets within and beneath the nail plate. Optical, confocal fluorescence and scanning electron microscopies demonstrated partial and complete laser poration of human nail samples, with the energy per pore and the exposure duration being the key modulating parameters that determined the extent of ablation achieved. Parallel measurements of the penetration of a model drug across laser-treated nails showed that complete poration resulted in essentially complete circumvention of the diffusion barrier, an array of 100 pores in 0.2 cm² area of nail permitting a 10³-fold increase in initial drug uptake. Partial ablation of the nail created pores that extended to a range of depths; the nail material adjacent to the ablated area was rendered porous in appearance presumably due to local thermal perturbation of the nail structure. These openings offer, as a result, potential sites in which topical drug formulations might be sequestered post-poration and from which slow, sustained delivery of the active agent into and through the nail may be envisaged.