Effect of nanoplastics on the transport of platinum-based pharmaceuticals in water-saturated natural soil and their effect on a soil microbial community

The transport of three platinum-based anticancer drugs (cisplatin, oxaliplatin and carboplatin) in soil-water environments, with and without the presence of two different types of surface functionalized polystyrene nanoparticles (PS-NPs; "nanoplastics"), was investigated. Recently, there is an increasing concern regarding the presence of micro and nanoplastics in aquatic and terrestrial ecosystems. Moreover, recent reports suggest that micro and nanoplastics may act as vehicles that enhance the mobility of other contaminants. Our transport studies indicate that PS-NPs may interact with pharmaceutical compounds and alter their mobility in a natural soil-water environment. Carboplatin showed "tracer like"mobility in soil without the presence of PS-NPs. When aminated PS-NPs were added to aqueous solutions, mobility of carboplatin in soil was reduced. Pt-complexes originating from cisplatin alone showed an elution of 35% of the inlet concentration at initial stages of the experiment with a gradual decrease to 15-20% recovery compared to the inlet concentration, while the presence of carboxylated PS-NPs significantly increases the recovery of Pt-complexes originating from cisplatin to ~56-60%. Oxaliplatin showed the lowest mobility (5-10% recovery only); aminated PS-NPs increased the recovery by more than 4-fold, to 35-36%. Carboplatin showed both up and down regulation (toxic) effects on soil bacterial taxa, while Pt-complexes originating from cisplatin showed mostly toxic effects on the microbial community; oxaliplatin was the least toxic. PS-NPs alone had little impact on soil microbes, but their presence was found to significantly increase the toxicity of Pt-based pharmaceuticals for soil microbial populations.