Methods based on nanostructures have been developed for potentiometric immunosensors, but most involve low sensitivity or weak signal output and are unsuitable for routine use in diagnosis. Herein, we devise an in-situ signal-amplification strategy for enhanced electrical readout of potentiometric immunosensor toward target prostate-specific antigen (PSA, one kind of cancer biomarkers), based on polyion oligonucleotide-labeled gold nanoparticles (AuNPs). To decrease the background signal, monoclonal anti-human PSA capture antibody was covalently conjugated onto an activated glassy carbon electrode via typical carbodiimide coupling. AuNPs heavily functionalized with the polyion oligonucleotides and polyclonal anti-PSA detection antibodies (pAb2-AuNP-DNA) were utilized as the signal-generation nanotags. In the presence of target PSA, a sandwich-type immunoreaction was executed between capture antibody and detection antibody on the electrode. The detectable signal derived from the shift in the electric potential as a result of the change in the surface charge before and after the antigen-antibody reaction. With target PSA increased, the captured pAb2-AuNP-DNA to the electrode accompanying detection antibody increased, thereby resulting in the change of the electrode potential. Due to numerous polyion oligonucleotides with the negative charge, the signal readout amplified. Under the optimal conditions, the shift in the output potential was proportional to the logarithm of target PSA concentration and displayed a dynamic linear range from 0.05 to 20 ng mL−1 with a detection limit of 13.6 pg mL−1. An intermediate precision of ≤13.2% was accomplished with the batch-to-batch identification. The selectivity was acceptable. The method accuracy was evaluated for human serum specimens, and gave the consistent results between the potentiometric immunosensor and the referenced enzyme-linked immunosorbent assay (ELISA).
Lv, S., Lin, Z., Zhang, K., Lu, M., & Tang, D. (2017). Polyion oligonucleotide-decorated gold nanoparticles with tunable surface charge density for amplified signal output of potentiometric immunosensor. Analytica Chimica Acta, 964, 67–73. https://doi.org/10.1016/j.aca.2017.02.004