Surface confinement–induced electrochemiluminescence enhancement of Au nanoclusters for ultrasensitive detection of a soluble urokinase-type plasminogen activator receptor

In this study, gold nanoclusters (Au NCs) anchored on the surface of 2D Zn-containing hydroxyl double salt (Zn-HDS) with surface confinement–induced electrochemiluminescence (SC-ECL) improvement were used as an intensive ECL emitter to construct a biosensor for ultrasensitive detection of soluble urokinase-type plasminogen activator receptor (suPAR) related to cardiovascular disease in chronic nephritis patients. Impressively, SC-ECL of Au NCs/Zn-HDS nanocomposites exhibited fast electrochemical excitation and efficient radiation transition, showing 4.9 times stronger ECL emission and 10.9 times higher ECL efficiency than those of pure Au NCs. This improvement was attributed to the matched energy level of Zn-HDS and Au NCs, enabling electron–hole pairs of Au NCs to be trapped by the energy levels of Zn-HDS. Moreover, a bipedal DNA walker was generated through target-induced DNA strand displacement and catalytic hairpin assembly (CHA), which was attached to a stable DNA cubic track through electrostatic attraction of positively charged SH-PEG-NH3+ to improve walking efficiency and further boost detection sensitivity. Consequently, the proposed sensing platform achieved trace detection of suPAR ranging from 0.700 pg/mL to 80.0 ng/mL with a low detection limit of 0.344 pg/mL and was successfully applied to detect suPAR in patient serum. This work synthesized a highly efficient metal nanocluster-based ECL emitter, showing great potential in constructing ultrasensitive biosensors for early disease diagnosis.