A dual-mode biosensor for salivary cortisol with antibody-aptamer sandwich pattern and enzyme catalytic amplification.

A split-type and dual-mode (photoelectrochemical and electrochemical, PEC and EC) biosensor was developed for non-invasive and sensitive detection of cortisol in saliva, based on antibody-aptamer sandwich model and enzyme catalytic amplification. Platinum nanoparticles (PtNPs)/CdIn4S2/TiO2/FTO served as the sensing electrode, and glucose oxidase/aptamer-conjugated Au nanoparticles (GOx-AuNPs-Apt) served as the measurement probe. In the presence of the target cortisol, a sandwich complex including cortisol, antibody, and GOx-AuNPs-Apt detection probe could be formed. When glucose and 4-chloro-1-naphthol (4-CN) were present, GOx and AuNPs in the complex worked together to catalyze glucose to generate H2O2, which encouraged PtNPs to catalyze 4-chloro-1-naphthol to generate a significant amount of benzo-4-chlorohexadienone (4-CD) precipitation. However, in the absence of cortisol, there was no 4-CD precipitation because none of the above catalytic reactions could be carried out. As an effective quencher, 4-CD may reduce photocurrent while simultaneously increasing charge transfer resistance, so a double-signal immunosensor using 4-CD as the signal indication was built. With the increase of target concentration, the PEC signal decreased while the EC signal increased, and within optimal conditions, this sensor had a good linear relationship in the range of 0.001−1000 ng/mL. The detection limits of photochemistry and electrochemistry were 0.8 pg/mL and 0.4 pg/mL, respectively. Furthermore, the designed method had acceptable recoveries of 88.0–114.7% and well-matched accuracy using the commercialized human cortisol ELISA kit and standard HPLC-MS as references. Photoelectrochemical and electrochemical dual-mode biosensor for salivary cortisol: Integrating antibody-aptamer sandwich pattern with enzyme catalytic amplification [ABSTRACT FROM AUTHOR]