Sirtuin 1 evaluation with a novel immunoassay approach based on TiO2–Au label and hyperbranched polymer hybrid

Accurate and highly sensitive evaluation of the sirtuin 1 (SirT1) level is becoming increasingly important for understanding the contribution of SirT1 in metabolism pathways. Here, a novel electrochemical immunoassay of SirT1 based on crosslinked hyperbranched azo-polymer decorated with gold colloids (Au–HAP) as sensing platform and titanium dioxide (TiO2)–Au nanocomposites to immobilize secondary antibody–horseradish peroxidase (Ab2–HRP) as electrochemical labels has been designed. Greatly enhanced sensitivity was achieved by exploiting the excellent conductivity of Au nanoparticle, the amplification effect of Au–HAP and TiO2–Au, and the favorable catalytic ability of HRP. The nanocomposites of Au–HAP and TiO2–Au could attach numerous capture antibodies on the surface for significant immune recognition efficiency. Meanwhile, the TiO2–Au-labeled Ab2–HRP using an HRP–thionine–H2O2 (hydrogen peroxide) detection system could further induce signal readout. Under optimal conditions, the signal intensity was linearly related to the concentration of SirT1 in the range of 1–500 ng ml−1, and the limit of detection was 0.28 ng ml−1. The developed biosensor exhibits attractive performance for the analysis of SirT1, with rapid response, high sensitivity, and high accuracy, and could become a promising technique for protein detection.