Effects of organic matter on uptake and intracellular trafficking of nanoparticles in Tetrahymena thermophila

While the biological uptake of nanomaterials (NMs) has been widely investigated, few studies have correlated the adsorption of natural organic matter (NOM) to uptake patterns. NOM is ubiquitous in the aquatic environment, inevitably leading to adsorption. In the present study, mixtures of bovine serum albumin (BSA) and humic acid (HA) were adopted to simulate NOM, and the effects of organic matter adsorption on uptake and intracellular trafficking of AgNPs with varied alkyl chain lengths in Tetrahymena thermophila were investigated. Notably, adsorption of BSA was shown to enhance the uptake rate of hexyl AgNPs in T. thermophila via the caveolae-mediated pathway while HA exerted no effect. Moreover, coating with BSA induced transfer of NPs into a more acidic intracellular environment, which was dependent on the association constant between BSA and NPs. A lower association constant resulted in rapid dissociation of BSA from the nanosurface, which terminated further acidification of NPs. Our collective results suggest that the composition of adsorbed organic matter strongly affects the bioavailability of NPs. Additionally, these effects are highly dependent on the physicochemical properties and interactions of NPs with organic matter.