Microplastics as potential carriers of viruses could prolong virus survival and infectivity

Microplastics are emerging contaminants in various aquatic environments, leading to human and environmental health concerns. Viruses have also been ubiquitously detected in aquatic environments, and there is an unknown risk of microplastics-mediated virus migration through adsorption. This study applied polystyrene microplastics as the carrier and the T4 bacteriophage (or phage) as the virus model, and a violet side scatter/green fluorescence double-gated flow cytometry approach to investigate the adsorption capacity of viruses on microplastics. Our results show that up to 98.6±0.2% of the dosed viruses can be adsorbed by microplastics, and such adsorptions are dependent on size and surface functional groups. Both Fourier-transform infrared spectroscopy and fluorescence-labelled confocal microscopy confirmed that the virus can successfully adsorb onto microplastics. Zeta potential characterisation revealed that the electrostatic interaction is the primary adsorption mechanism associated with the adsorption of viruses. UV-aging was found to enhance the adsorption capacities of viruses on microplastics. Both pristine and UV-aged microplastics were found to significantly prolong the infectivity of the adsorbed viruses, even under elevated temperatures. Collectively, our findings highlight that microplastics are associated with the biological risks of water-borne viral transmission through virus adsorption.