AgAu@Ag core-shell triangular nanonet jointed with composite SERS enhanced substrate for capturing and sensing urine biomarkers FGFR3 and NMP22

Herein, we achieved ultrasensitive surface-enhanced Raman scattering (SERS) detection of bladder cancer (BC) urine biomarkers, nuclear matrix protein 22 (NMP22) and fibroblast growth factor receptor 3 (FGFR3) by preparing gold and silver core-shell triangular nanonets (AgAu@Ag TNNs) with porous triangular mesh structures. The tip effect of the triangular structure of AgAu@Ag TNNs and the plasma coupling of the mesh holes on its surface enabled an enhancement factor (EF) of 1.37 × 10⁸. Moreover, we prepared gold-sprayed silicon wafers (Si@Au) by a simple physical method and covered graphene oxide (GO) on them as SERS substrates (Si@Au@GO). The plasmon coupling effect and chemical enhancement of this substrate improved the EF of AgAu@Ag TNNs to 1.88 × 10⁸. Based on above excellent SERS performance of nanoparticles combined with substrate, we achieved simultaneous quantitative detection of FGFR3 and NMP22 in the range of 100 fg/mL- 10 ng/mL and 100 fg/mL- 100 ng/mL, with the limit of detection (LOD) of 73.36 fg/mL and 21.56 fg/mL, respectively. This ultra-sensitive and specific joint immunosensor provides a reliable detection strategy to assist in the precise localisation of BC clinical staging.