The Human Stratum Corneum Prevents Small Gold Nanoparticle Penetration and Their Potential Toxic Metabolic Consequences

David C Liu,Jeffrey E Grice,Daniel Sundh,Tarl W Prow,Michael S Roberts,H Peter Soyer,Anthony P Raphael

doi:10.1155/2012/721706

David C Liu, Jeffrey E Grice + Show 5 more

Open Access

https://doi.org/10.1155/2012/721706

Copy DOI

Abstract

Nanoparticles are being used in multiple applications, ranging from biomedical and skin care products (e.g., sunscreen) through to industrial manufacturing processes (e.g., water purification). The increase in exposure has led to multiple reports on nanoparticle penetration and toxicity. However, the correlation between nanoparticle size and its penetration without physical/chemical enhancers through the skin is poorly understood—with studies instead focusing primarily on skin penetration under disrupted conditions. In this paper, we investigate the penetration and metabolic effects of 10 nm, 30 nm, and 60 nm gold nanoparticles within viable excised human skin after 24-hour exposure using multiphoton tomograph-fluorescence lifetime imaging microscopy. After 24 hour treatment with the 10, 30, and 60 nm gold nanoparticles, there was no significant penetration detected below the stratum corneum. Furthermore, there were no changes in metabolic output (total NAD(P)H) in the viable epidermis posttreatment correlating with lack of penetration of nanoparticles. These results are significant for estimating topical nanoparticle exposure in humans where other model systems may overestimate the exposure of nanoparticles to the viable epidermis. Our data shows that viable human skin resists permeation of small nanoparticles in a size range that has been reported to penetrate deeply in other skin models.

Highlights

The skin is the largest organ of the body and is the primary barrier to nanoparticle exposure from naturally occurring and engineered nanomaterials found in the environment and workplace [1,2,3]
We have previously shown ex vivo that skin treated with gold nanoparticles suspended in toluene results in nanoparticle penetration into the epidermis due to toluene acting as a chemical enhancer and disrupting the stratum corneum [8]
Analysis of nanoparticle skin penetration involves a number of factors including the skin model, skin barrier integrity, and the inherent physicochemical attributes of the nanoparticles and vehicle of the formulation

Summary

Introduction

The skin is the largest organ of the body and is the primary barrier to nanoparticle exposure from naturally occurring and engineered nanomaterials found in the environment and workplace [1,2,3]. A number of reports have shown that nanoparticles penetrate skin into the dermis under various physically disrupted conditions [4,5,6,7,8]. Nanoparticles have been shown to penetrate skin in the presence of chemical enhancers [3]. We have previously shown ex vivo that skin treated with gold nanoparticles suspended in toluene results in nanoparticle penetration into the epidermis due to toluene acting as a chemical enhancer and disrupting the stratum corneum [8]. Even though there are multiple reviews on nanoparticle toxicity and penetration within the skin [9,10,11,12,13], the correlation between nanoparticle size and its penetration without physical/chemical enhancers is poorly understood— with studies instead focusing primarily on skin penetration under disrupted conditions

Objectives

Methods

Results

Conclusion