Film-permeability-triggered afterglow electrochemiluminescence for lipase detection

Afterglow electrochemiluminescence (ECL), persistent luminescence observed after the cessation of electrical excitation, has attracted great attention but remains unexplored in sensing applications. Here, we present a solid-state afterglow ECL biosensor leveraging enzyme-responsive polymer nanoarchitectonics for lipase quantification. The sensor is constructed by covalently grafting an amphiphilic block copolymer (PCL-PEG) onto nitrogen-deficient carbon nitride nanosheets (CN_xNS) deposited on electrodes. Hydrophobic PCL segments self-assemble into a compact barrier under aqueous conditions, blocking S₂O₈^2- diffusion and suppressing CN_xNS's afterglow ECL. Lipase-triggered hydrolysis of PCL dynamically increases the film's permeability, enabling the recovery of afterglow ECL proportional to enzyme activity. The sensor achieves a detection limit (3σ) of 1 μU mL^-1 with a broad linear range of 1 μU mL^-1 to 10 mU mL^-1, and shows high specificity against interferents (e.g. α-amylase, trypsin). Real-sample validation in toners demonstrates its practical applicability. This work establishes a paradigm for afterglow ECL-based biosensing.