Aggregation-induced ECL strategy based on CuAg nanoclusters/Curdlan-g-PGTMAC for gastric cancer detection

In this work, a novel biosensor based on aggregation-induced luminescence (AIE) of copper-silver alloy nanoclusters (CuAg NCs) has been developed for the detection of gastric cancer marker miRNA-142-3p. The alloy nanoclusters were synthesized by doping Ag ions into Cu NCs as nano-emitters. On the one hand, the doped Ag ions induced Ag-Cu metallophilic interactions, which promoted the relaxation of excited electrons through the radiative pathway. On the other hand, the doped Ag ions can reduce the band gap between the HOMO-LUMO orbitals of the nanoclusters, which decreased the energy consumed for electronic excitation. Therefore, the luminescent signal and stability of CuAg NCs were significantly enhanced. Furthermore, the modification of the permanently positively charged polysaccharide quaternary ammonium salt (Curdlan-g-PGTMAC) on CuAg NCs induced the aggregation-induced electrochemiluminescence (AIECL) effect. The introduction of Curdlan-g-PGTMAC also accelerated the reduction of the co-interaction reagent (S₂O₈^2-), which significantly improved the ECL generation efficiency. The ECL response of the CuAg NC-based AIECL biosensor showed a good linear correlation with the concentration of miRNA-142-3p over a wide range from 1 fM to 100 nM with a detection limit as low as 8.8 fM. The ECL biosensor with high sensitivity and wide dynamic range was used for the clinical application of miRNA-142-3p in gastric cancer successfully.