Multi-walled carbon nanotube oxidation dependent keratinocyte cytotoxicity and skin inflammation

Brian C Palmer,Lisa A Delouise,Sarah J Phelan-Dickenson

doi:10.1186/s12989-018-0285-x

Abstract

BackgroundThe effects of carbon nanotubes on skin toxicity have not been extensively studied; however, our lab has previously shown that a carboxylated multi-walled carbon nanotube (MWCNT) exacerbates the 2, 4-dinitrofluorobenzene induced contact hypersensitivity response in mice. Here we examine the role of carboxylation in MWCNT skin toxicity.ResultsMWCNTs were analyzed by transmission electron microscopy, zetasizer, and x-ray photoelectron spectroscopy to fully characterize the physical properties. Two MWCNTs with different levels of surface carboxylation were chosen for further testing. The MWCNTs with a high level of carboxylation displayed increased cytotoxicity in a HaCaT keratinocyte cell line, compared to the MWCNTs with intermediate levels of carboxylation. However, neither functionalized MWCNT increased the level of in vitro reactive oxygen species suggesting an alternative mechanism of cytotoxicity. Each MWCNT was tested in the contact hypersensitivity model, and only the MWCNTs with greater than 20% surface carboxylation exacerbated the ear swelling responses. Analysis of the skin after MWCNT exposure reveals that the same MWCNTs with a high level of carboxylation increase epidermal thickness, mast cell and basophil degranulation, and lead to increases in polymorphonuclear cell recruitment when co-administered with 2, 4-dinitrofluorobenzene.ConclusionsThe data presented here suggest that acute, topical application of low doses of MWCNTs can induce keratinocyte cytotoxicity and exacerbation of allergic skin conditions in a carboxylation dependent manner.

Highlights

The effects of carbon nanotubes on skin toxicity have not been extensively studied; our lab has previously shown that a carboxylated multi-walled carbon nanotube (MWCNT) exacerbates the 2, 4dinitrofluorobenzene induced contact hypersensitivity response in mice
Both carboxylated nanoparticles were relatively well dispersed as evidenced by the low hydrodynamic diameter and polydispersity index values; as expected, the pristine MWCNT displayed poor dispersity in water
All MWCNTs were similar in overall size and shape as indicated by the representative transmission electron microscopy (TEM) images (Fig. 1a-c) with a minor difference being the appearance of less defects and nanotube fragments in both the pristine MWCNTs and the MWCNTs of Lot #2

Summary

Introduction

The effects of carbon nanotubes on skin toxicity have not been extensively studied; our lab has previously shown that a carboxylated multi-walled carbon nanotube (MWCNT) exacerbates the 2, 4dinitrofluorobenzene induced contact hypersensitivity response in mice. Carbon nanotubes (CNT) are layers of sp hybridized carbon atoms formed into single-walled (SWCNT) or multi-walled (MWCNT) cylindrical structures that were first reported by Sumio Iijima [1, 2]. These high aspect ratio nanoparticles have a pore diameter < 100 nm and a length usually on the micron scale. Research suggested that in vivo respiratory exposures to CNTs led to acute lung inflammation and fibrosis [5,6,7,8] These revelations prompted the National Institute for Occupational Safety and Health to recommend an 8 h time-weighted average of elemental carbon respirable mass exposure limit of 1 μg/m3 [9]. More recent surveys of CNT manufacturers reveal that most sites are below the new airborne exposure limit [10, 11]; less is known

Methods

Results

Discussion

Conclusion