2-D/2-D heterostructured biomimetic enzyme by interfacial assembling Mn3(PO4)2 and MXene as a flexible platform for realtime sensitive sensing cell superoxide

It is critical for fabricating flexible biosensors with both high sensitivity and good selectivity to realize real-time monitoring superoxide anion (O2•−), a specific reactive oxygen species that plays critical roles in various biological processes. This work delicately designs a Mn3(PO4)2/MXene heterostructured biomimetic enzyme by assembling two-dimensional (2-D) Mn3(PO4)2 nanosheets with biomimetic activity and 2-D MXene nanosheets with high conductivity and abundant functional groups. The 2-D nature of the two components with strong interfacial interaction synergistically enables the heterostructure an excellent flexibility with retained 100% of the response when to reach a bending angle up to 180°, and 96% of the response after 100 bending/relaxing cycles. It is found that the surface charge state of the heterostructure promotes the adsorption of O2•−, while the high-energy active site improves electrochemical oxidation of O2•−. The Mn3(PO4)2/MXene as a sensing platform towards O2•− achieves a high sensitivity of 64.93 µA·µM−1·cm−2, a wide detection range of 5.75 nM to 25.93 µM, and a low detection limit of 1.63 nM. Finally, the flexible heterostructured sensing platform realizes real-time monitoring of O2•− in live cell assays, offering a promising flexible biosensor towards exploring various biological processes.