Plasmonic-photonic metasensor with mesoporous Nb2C MXene for the detection of IgAN extracellular vesicles

Two-dimensional metasurface is composed of functional nanounits at the subwavelength scale, which can manipulate the propagation and characters of light. However, metasurfaces are still in the stage of theoretical study, which lack practical application exploration. Herein, we designed a novel metasurface-based biosensor as metasensor for the detection of extracellular vesicles. Firstly, the mesoporous Nb₂C MXene (mesoNb₂C) nanosheets had in-plane structure with the uniform pore size, which improved both electrochemical and luminescence performance. Furthermore, a novel metasurface was prepared consisting of plasmonic Au nanorings (Au NRs) layer and ZnS@SiO₂ photonic crystal as sensing interface. The constructed plasmonic-photonic metasensor can adjust the reflection wavelength. So, the electrochemiluminescence (ECL) signal of mesoNb₂C can be reflected by the ZnS@SiO₂ photonic crystal and significantly enhanced by the Au NRs array with the local surface plasmon resonance hotspots in the metasensor. Finally, the metasensor was used to evaluate the expression of miRNA-23b-3p in the urinary EVs of IgA nephropathy patients. The metasensor showed a good linear relationship between the ECL intensity and the logarithm of miRNA-23b-3p concentration from 1 fM to 100 nM, and the limit of detection was 0.45 fM, which can be used to effectively distinguish between normal people, mild patients and severe patients.