Microscopical evaluation of the cornea in the isolated chicken eye test: the most common histopathological changes

and zDepartment of Dermatology, Venerology and Allergology, Charit eeUniversit€atsmedizin Berlin, Germany Introduction: Nanoparticles (NPs) are widely used in everyday products as well as biomedical applications and intended or unintended contacts between NPs and the skin are likely. It is still unclear, however, whether pre-existing skin diseases may predispose to unwanted NP penetration or whether NPs may even aggravate hypersensitivity reactions. The aim of this study was to investigate whether AHAPS-functionalized silica NPs penetrate inflamed skin or affect the course of allergic contact dermatitis (ACD). Materials and Methods: SKH1 mice (n 5 5 per group) with oxazolone-induced ACD were treated topically with 250 mg silica NPs of 55 6 nm in diameter and N-(6-aminohexyl)(3-aminopropyl) trimethoxysilane (AHAPS)-functionalization or ultra pure water for 5 consecutive days. Mice were examined clinically, histopathologically and for several molecular parameters. NPs were visualized by fluorescence and transmission electron microscopy. Results: The AHAPS-silica NPs were only identified in the superficial layers of the stratum corneum of the epidermis, but not in deeper epidermal or dermal layers, despite severe inflammation and barrier disruption. Furthermore, the NPs did not affect the course of ACD. Conclusions: In contrast to previous general apprehensions about NPs and experimental data on other NPs, AHAPS-functionalized silica NPs seem not to penetrate inflamed skin or affect the course of ACD in this model. Whether they may serve as suitable drug carriers in different skin conditions remains to be studied.