Minimally Invasive Automated De-Epithelization by Precise ArF Excimer Laser Ablation

Abstract

Objective: Development of a robotic ArF excimer laser device with a three-dimensional (3D) pattern scanning sensor for the controlled de-epithelization of live mouse and xenografted epidermis. Significance: The animal model could be adapted to humans for automated, minimally invasive de-epithelization of cutaneous areas and therefore is of interest for cutaneous gene therapy research. Materials and Methods: Ablation thresholds of mouse, porcine, and human skin were measured by acoustic detection methods. These ablation thresholds were used as initial parameters for dosimetry measurements. De-epithelization of live mouse and xenografted epidermis was performed by laser ablation (ArF excimer laser, λ= 193 nm, t_p = 20 nsec). The rectangular shape of the laser spot and a robotic arm displacement incorporating a three-dimensional patter scanning sensor allowed a polygonal tile floor irradiation of a 2-cm-diameter area. Ablated epidermis was subjected to histology. Results: SCID and nude mouse skin did not entirely reflect the de-epithelization of human skin because abundant pockets of dermal keratinocytes persist in the outer root sheath of hair and cysts providing competitive foci of re-epithelization. Automated de-epithelization of human and porcine skin xenografts resulted in precise removal of keratinocytes with subcellular precision, providing a smooth live surface where epidermal transplants might engraft with little endogenous competition from residual outer root sheath from rare hairs. Conclusions: The displacement of the ArF excimer laser devices allows reproducible, smooth, and damage-free ablation of epidermal areas in the animal model.