Using sandpaper for noninvasive transepidermal optical skin clearing agent delivery

Abstract

We present a gentle mechanical method for the noninvasive transepidermal delivery of topically applied optical skin clearing agents. Optical skin clearing reduces light scattering in highly turbid skin with the aid of hyperosmotic chemicals such as glycerol, polyethylene glycol, and solutions of dextrose. Transepidermal delivery of such agents is believed to be most patient compliant and most likely to be used in a clinical environment. Optical skin clearing has the potential to expand the current limited use of laser light in medicine for diagnostic and therapeutic applications. Light scattering limits the penetration depth of collimated light into skin. In order to increase the diffusion of topically applied optical skin clearing agents into skin, we present a gentle mechanical delivery method involving glycerol and dextrose as optical skin clearing agents and fine 220-grit sandpaper to rub the clearing agent into the tissue. Gentle rubbing causes abrasion of the superficial skin layer including the stratum corneum, which otherwise prevents these optical skin clearing agents from freely diffusing into skin. Results indicate very fast optical skin clearing rates. In vivo hamster skin turned transparent within 2 min. The 1e light penetration depth increased by 36+/-3.75% for dextrose and 43+/-8.24% for glycerol. Optical skin clearing was reversed using phosphate buffered saline solution. Skin viability was observed 70 h post-treatment and showed scabbing and erythema on a few percent of the total optically cleared skin surface.

Optical clearing of biological tissues: prospects of application in medical diagnostics and phototherapy

“…The abrasive paper with the gritness 220 was used by Stumpp et al [136] for smooth rubbing of glycerol or dextrose solution into the depilated hamster skin in vivo. After 2-4 min of rubbing in, excluding any visible damage, the skin gradually became more transparent, allowing the observation of subcutaneous blood vessels.…”

“…Beside the chemical agents, a number of physical methods of surmounting the skin barrier are proposed to enhance the diffusion, including low-and high-intensity irradiation [130,158], fractional lamp [131,133] and laser [132] microablation, mechanical microperforation [137,138], ultrasonic (US) irradiation [134,135,159], electrophoresis [160], needleless injection [161], mechanical removal of the surface layer by means of abrasive paper [136], epidermal stripping [162], and microdermabrasion [163].…”

“…However, at low concentrations OCAs do not provide sufficient optical clearing, while at high concentrations they can induce edema, chemical burn, partial necrosis and scarring [45,65,108]. To develop an efficient and safe way of breaking the integrity of the epidermis stratum corneum and accelerating the penetration of OCA into the dermis, various physical methods [56,118,[130][131][132][133][134][135][136][137][138][139][140], chemical enhancers of permeability [114,118,[141][142][143][144][145][146][147], and their combinations [118,148,149] have been proposed.…”

Enhancement of skin optical clearing efficacy using photo‐irradiation

“…As a common method, intradermal injection of OCAs was used to improve the optical clearing of in vivo skin effectively [1,9], Nevertheless, OCAs with high concentration induced visible skin lesions [10,11], such as edema, suppuration, or even scarring. Although sandpaper abrasive is effective in facilitating transepidermal OCAs delivery [12], it is difficult to quantify and control the abrasive strength.…”

Application of an optical clearing agent during noninvasive laser coagulation of the canine vas deferens

“…7,8 Optical clearing agents ͑OCA͒ have been explored over the past decade with great interest by numerous investigators for reducing light scattering in skin and increasing the optical transmission through skin for both therapeutic and diagnostic light-based procedures. [9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27] Although the mechanism of optical clearing of skin is still being studied, the basic effect is understood. Common skin components, hydrated collagen ͑n = 1.42͒, stratum corneum ͑n = 1.55͒, and interstitial fluid ͑n = 1.36͒ have different refractive indices.…”