Chapter 11 - Laser and other ablation technologies

Abstract

Advances in the use of lasers and other ablation techniques for transdermal drug delivery are covered in this chapter. Laser poration involves the utilization of high-energy light source to form well-defined ablated regions in a tissue. When a fractional laser is employed, several microscopic channels are formed in the skin. These zones of treatment are surrounded by normal tissue. Laser-mediated drug delivery can be classified into four groups: (1) Nonablative dermal remodeling lasers (NDRLs) have nonaqueous chromophores and have been utilized to enhance drug delivery. Lasers such as the neodymium-doped YAG laser (1064nm) or the 585/595-nm pulsed dye laser used for the management of vascular disorders are also regarded as NDRLs; (2) nonablative fractional lasers such as erbium fiber laser (1550nm); (3) ablative fractional lasers are lasers that, when used fractionally, can form regions of thermal damage, which are called microscopic treatment zones; (4) fully ablative lasers, such as the erbium-doped yttrium aluminum garnet (Er:YAG) laser (ʎ=2940nm) or the carbon dioxide laser (ʎ=10,600nm), whose principal chromophore is water and have been used for the heating as well as complete vaporization of the skin. Another interesting method of increasing skin permeability involves heating the skin. It has been asserted that either very short exposures at high temperatures or long exposures at moderate temperatures can increase percutaneous transport. This increase in transdermal flux is ascribed to the formation of micrometer-scale conduits in the skin. One of the thermal ablation techniques involves the use of radiofrequency. Radiofrequency heating occurs in materials via energy transferred from the electric field to the charges in the material. When carrying out transdermal abrasion experiments, researchers use sandpaper or pressurized particles to remove the stratum corneum. On the other hand, microdermabrasion uses negative pressure and Al2O3 crystals to superficially peel off the outer surface of the skin. Several examples are given to illustrate the use of these ablation technologies.