BME MS Defense: Supriya Ravichandran

Quantification of Skin Barrier Function and Subsequent Nanoparticle Penetration in an ex vivo Human Skin Model

Supervised by Professor Lisa DeLouise

Abstract

There is a growing concern that the increasing presence of nanoparticles (eg. metal oxides, carbon nanotubes, quantum dots), formulated in commercial products may pose environmental health and safety risks. A major focus has been on nanoparticle skin penetration. Recent studies confirm that healthy skin is a supreme barrier preventing nanoparticles from penetrating the stratum corneum. However, when the skin barrier is compromised by exogenous factors such as mechanical injury or ultraviolet radiation, recent research suggests that nanoparticles can penetrate into the viable epidermis and below. No studies have however, considered the possibility that common skin care products could unknowingly alter the skin barrier function of otherwise healthy skin to potentially increase its susceptibility to nanoparticle penetration. In this study, we employ in vivo human skin and viable ex-vivo human skin models to investigate the effect of tape stripping and a commercial depilatory agent on barrier impairment.

Depilatory agents are common skin care products that may be used prior to the application of a nanoparticle containing cosmetic. Tape stripping was used as a positive control. The barrier disruption was quantified by measuring transepidermal water loss values on in vivo human skin and transepithelial electrical resistance measurements and tissue histology on ex-vivo skin. The effect of these treatment conditions on quantum dot penetration through ex-vivo skin was investigated with tissue histology to probe for nanoparticle penetration through the stratum corneum and flow cytometry to quantify quantum dot association with live epidermal cells. These results are the first to demonstrate that a depilatory agent can significantly alter skin barrier function to consequently allow nanoparticle stratum corneum penetration.