Carbon nanomaterials rescue phenanthrene toxicity in zebrafish embryo cultures

Abstract

Multi-Walled Carbon Nanotubes (MWCNTs) and Carbon Blacks (CB) are known to carry wide varieties of adsorbed, potentially toxic chemicals resulting from their manufacturing, typically including metals and polyaromatic hydrocarbons (PAHs). Instead of desorption of these adsorbates into aqueous milieu, substantial high-affinity adsorption of the aqueous dispersed PAH, phenanthrene to MWCNTs and CB from aqueous solutions and dispersions is reported. Phenanthrene adsorption to aqueous dispersed carbon nanomaterials phases was measured using isotherms and then exploited to remove toxic levels of phenanthrene from aqueous media incubating zebrafish embryos (ZFEs) as a whole organism toxicity screening system. Remarkable reduction in phenanthrene-induced ZFE toxicity was observed using two experiments: one comparing PAH concentration-dependent rescue of ZFE viability from MWCNTs compared to carbon black (CB), and a second examining kinetics of the ZFE rescue by MWCNTs vs. CB incubations after initial ZFE exposure to phenanthrene for 2 hours. Phenanthrene LD₅₀ concentration in the absence of any carbon-based sorbent increases dramatically to 10 μg ml⁻¹ in the presence of either 81.3 μg ml⁻¹ MWCNTs or 81.5 μg ml⁻¹ CB materials. When CB and MWCNTs were added to ZFEs previously exposed to 10 μg ml⁻¹ phenanthrene for 2 hours, significant rescue of ZFE viability was observed in CB-treated embryos while no ZFE rescue was observed in MWCNT-treated ZFEs. This result is consistent with an expected carbon nanomaterial surface area-dependent ZFE rescue effect: CB exhibits a higher Brunauer–Emmett–Teller (BET) surface area than the MWCNTs used, with higher adsorption capacity likely for phenanthrene, yielding ZFE rescue from toxicity.