Noninvasive Monitoring of In Vivo Degradation Kinetics of PLGA Implants Based on NIR-II Fluorescence Imaging

This study presents a noninvasive and quantitative strategy for real-time monitoring of the in vivo degradation of poly(lactic-co-glycolic acid) (PLGA) implants using a novel aggregation-caused quenching (ACQ) near-infrared-II (NIR-II) fluorescent probe, ACQ1. Cylindrical implants loaded with ACQ1 were fabricated and exhibited uniform fluorescence distribution, deep-tissue penetration, and minimal interference from released probes due to ACQ behavior. Both in vitro and in vivo experiments demonstrated a strong linear correlation between ACQ1 fluorescence intensity and implant mass loss. In contrast, conventional fluorophores (Coumarin 6 and Nile Red) showed significant signal artifacts and poor correlation with degradation, largely due to tissue autofluorescence and probe leakage. The ACQ1-based method enabled accurate, real-time tracking of PLGA degradation under accelerated conditions and in subcutaneous mouse models, offering a reliable tool for evaluating biodegradable implants and supporting future clinical translation.