Highly sensitive electrochemical immunoassay integrated with polymeric nanocomposites and enhanced SiO₂@Au core-shell nanobioprobes for SirT1 determination

An ultra-highly sensitive electrochemical immunosensor for SirT1 (a key protein in age-related diseases) evaluation has been designed, employing polymeric nanocomposites as sensing platform and core-shell SiO₂@Au to immobilize HRP-Ab₂ as nanobioprobes. The approach includes chemical synthesis of PAMAM-Au-MWCNT nanocomposites (PNCs) with abundant PAMAM-Au nanoparticles immobilized on the MWCNT matrix, and biochemically synthesis of nanobioprobes with highly dispersed SiO₂@Au tracing tags for successive efficient load functionalized enzyme-antibodies (HRP-Ab₂). The PNCs nanocomposites could improve the efficiency of immune response via abundant capture antibodies (Ab₁^#1) on the electrode surface, and accelerate electron transfer through MWCNT and Au nanoparticles. Besides, the SiO₂@Au was employed as tracing tags to label numerous HRP-Ab₂ to further enhance signal readout during HRP−thionine−H₂O₂ system. Under optimal conditions, the signal intensity was linearly related to the concentration of SirT1 in the range of 20 pg mL^-1 to 500 ng ml^-1, and the limit of detection was 12.5 pg mL^-1. It is noteworthy that the proposed immunoassay protocol has been successfully applied to evaluate SirT1 expression in cells by different treatment with high sensitivity and accuracy.