Toward safer multi-walled carbon nanotube design: Establishing a statistical model that relates surface charge and embryonic zebrafish mortality

Abstract

Given the increased utility and lack of consensus regarding carbon nanotube (CNT) environmental and human health hazards, there is a growing demand for guidelines that inform safer CNT design. In this study, the zebrafish (Danio rerio) model is utilized as a stable, sensitive biological system to evaluate the bioactivity of systematically modified and comprehensively characterized multi-walled carbon nanotubes (MWNTs). MWNTs were treated with strong acid to introduce oxygen functional groups, which were then systematically thermally reduced and removed using an inert temperature treatment. While 25 phenotypic endpoints were evaluated at 24 and 120 hours post-fertilization (hpf), high mortality at 24 hpf prevented further resolution of the mode of toxicity leading to mortality. Advanced multivariate statistical methods are employed to establish a model that identifies those MWNT physicochemical properties that best estimate the probability of observing an adverse outcome. The physicochemical properties considered in this study include surface charge, percent surface oxygen, dispersed aggregate size and morphology and electrochemical activity. Of the five physicochemical properties, surface charge, quantified as the point of zero charge (PZC), was determined as the best predictor of mortality at 24 hpf. From a design perspective, the identification of this property–hazard relationship establishes a foundation for the development of design guidelines for MWNTs with reduced hazard.

• Carbon nanotube toxicity
• predictive toxicity
• property–hazard relationship
• safe material design
• zebrafish (Danio rerio)

Acknowledgements

The authors would like to thank Patrick Kelleher for assisting with the MWNT preparation, Eva Albalghiti for collecting PZC measurements, and David Goodwin for providing XPS analysis.

Declaration of interest

The authors declare no conflict of interest. The authors alone are responsible for the content and writing of the paper. This publication was developed under Assistance Agreement No. RD83558001-0 by the U.S. Environmental Protection Agency and the NIH grant No. T32 ES07060 and P30 ES000210. It has not been formally reviewed by EPA. The views expressed in this document are solely those of the authors and do not necessarily reflect those of the Agency. EPA does not endorse any products or commercial services mentioned in this publication.

Supplementary material available online

Supplementary Figure S1 and Table S1