Tracking How Biodegraded Microplastics Enter the Ecosystem with CuInS₂@ZnS QDs

Plastic pollution has become a vital issue that damages the ecosystem and threatens human health. Nevertheless, tracking how the microplastics, i.e., the main product of plastics, degraded in the environment remains difficult. To address this challenge, we herein report a simple but innovative model system formed by poly(l-lactic acid) (PLLA) and CuInS2@ZnS quantum dots (QDs) for optically tracking the degraded microplastics. The PLLA films incorporated with QDs were prepared through blending PLLA with hydrophobic CuInS2@ZnS QDs followed by hot pression. The optical stability of PLLA films was evaluated, and both the enzymatic degradation and fermentation behaviors of bulk PLLA were investigated. The uptake of microplastics by different microorganisms was analyzed through fluorescence imaging, and the results revealed that the PLLA microplastics were mainly collected by Gram-positive cocci. Preliminary animal studies on zebrafish suggested that the microplastics doped with QDs remained fluorescent in vivo, even though the microplastics were very toxic.