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 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 the aqueous solution, mobility of carboplatin in soil was reduced. Pt-complexes originating from cisplatin alone showed 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 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 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.