Fluorescent probe based on carbon dots/silica/molecularly imprinted polymer for lysozyme detection and cell imaging

The abnormal concentration of lysozyme in body fluids and tissues is a potential indicator for diseases such as leukemia and meningitis. In this work, by combining the excellent optical properties of carbon dots (CDs) with the favorable selectivity of molecularly imprinted polymer (MIP), a novel fluorescent probe for lysozyme detection and cell imaging was constructed, where silanized CDs with low cytotoxicity (CDs/SiO₂) were used as the fluorescence signal reporter and N-isopropylacrylamide (NIPAM) was used as the temperature-sensitive monomer. The as-prepared CDs/SiO₂/MIP showed a thermo-sensitive property for the response to lysozyme. Moreover, this probe could be used for quantitative detection of lysozyme, with a wider detection range (0.001~0.01 mg/mL), a low detection limit (0.55 μg/mL), and a high selectivity. Importantly, the MTT assay testified that the fluorescent CDs/SiO₂/MIP probe had low cytotoxicity. In addition, human hepatoma carcinoma cells (HepG-2 cells) could be stained by the CDs/SiO₂/MIP, and showed a bright intracellular green fluorescence, indicating that the imaging of live cells was possible. This study provides a new way to detect lysozyme in vitro and an attractive perspective to probe intracellular lysozyme in vivo.