Influence of multi-walled carbon nanotubes on the toxicity of ZnO nanoparticles in the intestinal histopathology, apoptosis, and microbial community of common carp.

In recent years, carbon nanotubes (CNTs) have gained tremendous attention due to their widespread application. Previous research indicated that carbon nanomaterials can affect the toxicity of some pollutants. In this study, we investigated the influence of multi-walled CNTs (MWCNTs) on the toxicity of ZnO nanoparticles (ZnONPs) in the intestine of common carp (Cyprinus carpio). After four-week exposure, histopathological observation and TUNEL assay showed concentration ratio-dependent intestinal lesions and apoptosis, with the most severe in the HSC-ZnONPs group (50 mg L−1 ZnONPs and 2.5 mg L−1 MWCNTs), less severe in the ZnONPs group (50 mg L−1 ZnONPs) and the least in the LSC-ZnONPs group (50 mg L−1 ZnONPs and 0.25 mg L−1 MWCNTs). Furthermore, ICP-OES indicated that intercellular zinc accumulation was significantly decreased by the presence of the MWCNTs, which suggested the varied contribution of ZnONPs to intestine injury in different groups. Moreover, 16 s rDNA sequencing revealed that ZnONPs alone and in combination with MWCNTs significantly altered the microbial community diversity and composition of the gut microbiota compared with controls. In addition, the predominant phylum, class, order, family, and genus were significantly different among these groups. In conclusion, the influence of MWCNTs on the toxicity of ZnONPs was related to the concentration and concentration ratio of the mixture. [Display omitted] • ZnONPs exposure induced histological alterations and apoptosis in the intestine. • Low level of MWCNTs have an antagonism effect on toxicity of ZnONPs to common carp. • High level of MWCNTs have a synergy effect on toxicity of ZnONPs to common carp. • MWCNTs significantly decreased ZnONPs accumulation in the intestine after four weeks exposure. • Single ZnONPs exposure or co-exposure with MWCNTs and ZnONPs alterated gut microbiota. [ABSTRACT FROM AUTHOR]