Nanoparticles-EPS corona increases the accumulation of heavy metals and biotoxicity of nanoparticles

Microbial extracellular polymeric substances (EPS) coating nanoparticles (NPs) surface can form NPs-EPS corona, which significantly affect the adsorption of NPs to toxic substances and alter the ecotoxicological effect of NPs. In this work, the EPS coronas on TiO₂ NPs (TNPs) and CeO₂ NPs (CNPs) were characterized and the adsorption characteristics of NPs with and without EPS corona to five heavy metals were investigated in single-metal and multiple-metal systems. The results of spectral analysis showed that NPs-EPS corona exhibited new crystalline phases and abundant functional groups. Moreover, 42 and 13 proteins were identified in the TNPs-EPS and CNPs-EPS coronas, respectively. The rates of Cd²⁺, Pb²⁺, Cu²⁺, Ni²⁺ and Ag⁺ adsorption by NPs-EPS corona increased to values that were 6.7-7.6, 4.4-5.1, 4.2-5.5, 3.9-4.9 and 8.5-8.8 times those of NPs without EPS corona, respectively, in single-metal system. NPs-EPS coronas are effective in absorbing Ag⁺, Pb²⁺ and Cu²⁺ compared with Cd²⁺and Ni²⁺ in multiple metal adsorption. These results indicated that NPs-EPS corona effectively adsorb and remove heavy metals by forming NPs-EPS-metal complexes and inducing precipitation. However, NPs-EPS corona can enhance the toxicity of NPs by accumulating highly-toxic heavy metals in aquatic environments.