Target-mediated silver deposition-based electrochemical biosensor for highly sensitive detection of human chorionic gonadotropin

As a glycoprotein hormone, human chorionic gonadotropin (hCG) is an established marker for pregnancy test. On the basis of the target-mediated silver deposition (TSD), in this work, we report the development of an amplification-free electrochemical biosensor for the highly sensitive detection of hCG. The detection of hCG involves the use of the affinity peptide-modified electrode for hCG capture (the CGGSSPPLRINRHILTR peptide containing the hCG-binding domain of the PPLRINRHILTR sequence is used as the affinity peptide), the oxidation of the diol sites of the glycan chains on hCG hormones into aldehyde groups by NaIO₄, and the deposition of silver nanoparticles (AgNPs) for the solid-state voltammetric stripping analysis. Due to the deposition of multiple AgNPs while the solid-state Ag/AgCl voltammetric process has a high signal-to-noise ratio, the TSD-based electrochemical biosensor can be applied to the highly sensitive detection of hCG without the need for signal amplification. Under optimal conditions, the stripping current increased linearly with an increasing hCG concentration over the range from 1.0 to 25 mIU/mL, with a detection limit of 0.45 mIU/mL. Owing to the high specificity of the hCG-binding peptide PPLRINRHILTR, this electrochemical hCG biosensor exhibits high selectivity. The results of the quantitative assay of hCG in urine samples at the concentrations of 25, 10, and 1.0 mIU/mL are desirable, indicating the good anti-interference capability. As the TSD-based electrochemical biosensor allows the amplification-free detection of low-abundance hCG, it is easy to use and cost-effective, showing great promise in point-of-care assay of hCG for pregnancy test.