Target-responsive vesicular nanoprobe for fluorescent detection of lipase

A novel fluorescent vesicular nanoprobe (RhB@HMCN_x-PCL-PEG) is presented for lipase activity monitoring, leveraging the synergetic integration of nitrogen-deficient hollow mesoporous carbon nitride nanoparticles (HMCN_x) and lipase-responsive amphiphilic block copolymers. The HMCN_x, engineered via KSCN-assisted hydrothermal treatment, exhibits enhanced water dispersibility while remaining its hollow mesoporous structure, enabling efficient encapsulation of rhodamine B (RhB). Subsequent covalent conjugation of carboxyl-terminated poly(ε-caprolactone)-poly(ethylene glycol) (COOH-PCL-PEG) and self-assembly-driven vesicle formation establish a "signal-on" detection mechanism. Lipase-triggered hydrolysis of the PCL layer releases RhB, with fluorescence intensity quantitatively correlating to lipase activity. The nanoprobe achieves a low detection limit of 0.5 mU mL⁻¹ (3σ) and a broad linear range (0.5 to 5 U mL⁻¹). Remarkable selectivity against interferents (e.g., trypsin, α-amylase) and robust performance in real samples (milk, skin toner) underscore its practicality. This work not only advances carbon nitride-based nanomaterials for biosensing but also provides a platform for enzyme-responsive detection systems.