Graphitic carbon nitride nanosheets-based turn-on fluorescent biosensor for highly sensitive, label-free detection of adenylate kinase activity

Graphitic carbon nitride nanosheets (CNNS) are a promising kind of graphene-like two-dimensional (2D) nanomaterials, which have great potential as biological probes for biosensing and bioimaging applications. However, the pristine CNNS are usually chemically inert, making the functional modification is difficult, which limits their practical biological applications. Therefore, development of new designs for CNNS-based biosensors to extend biological applications is interesting and also of great significance. Herein, we developed a novel CNNS-based turn-on biosensor for simple, sensitive and label-free detection of adenylate kinase (ADK) activity. The approach relies on ADK-mediated catalytic reverse transphosphorylation reaction (2ADP ⇋ ATP + AMP). In this method, quantitative analysis of ADK activity in the concentration range from 0.1 to 100 U/L with the low detection limit of 0.06 U/L. Moreover, it was successfully applied in detecting ADK in the complex biological media. We believe the developed biosensing strategy might provide a rapid, cost-efficient, highly sensitive and label-free platform for ADK-based clinical diagnosis and biomedical research.