Near-infrared (NIR-II) fluorescent poly(ethylene terephthalate) nano-microplastics for in vivo tracking

Abstract Environmental health concerns because of nano-microplastics (NMPs) are growing, yet in vivo data in mammals remain scarce. Most analysis techniques rely on excised organs, limiting the ability to observe real-time NMP migration within living organisms. Therefore, there is an increasing need for simple, non-invasive techniques to track NMPs in vivo. In this study, we utilized near-infrared (NIR) fluorescence (NIRF), known as the second biological window in NIR (NIR-II), and applied it to in vivo optical imaging of deep tissue. NIR-II fluorescent poly(ethylene terephthalate) (PET) particles were synthesized by encapsulating the NIR-II fluorescent dye IR-1061 into PET. PET was dissolved in acetonitrile and stirred with IR-1061 under a nitrogen atmosphere for 24 h, with a dye loading of 1.56 mg/mg PET. To prevent agglomeration and control particle size (30–300 nm), an aqueous bovine serum albumin solution (0.02–50 mg/mL) was added. The mixture was then stirred in open air for 48 h to evaporate residual acetonitrile. In vivo NIRF imaging enabled real-time tracking of PET particles’ distribution over time following oral administration to mice. This method offers a promising platform for evaluating the behavior and potential toxicity of NMPs based on their size and composition.