Polyaspartic acid-doped CaCO3 nanospheres: A novel signal-generation tag for electrochemical immunosensing with calcium ion-selective electrode

•Polyaspartic acid-doped CaCO3 nanospheres as the signal-generation tags.•Calcium ion-selective electrode as the readout device.•Polyaspartic acid-doped CaCO3 nanospheres for the labeling of antibody.

A novel signal-generation tag based on polyaspartic acid (PASA)-doped CaCO3 nanospheres was utilized for development of the electrochemical immunosensing protocol with a calcium ion-selective electrode (Ca-ISE). The organic-inorganic hybrid nanospheres were synthesized via the reverse micellar method, and functionalized with the detection antibody through the carbodiimide coupling. Upon target analyte introduction, a sandwiched immunoreaction was carried out on the microplate between capture antibody and the labeled detection antibody on the CaCO3 nanospheres. The carried CaCO3 was dissolved under acidic conditions, and the released Ca2 + ions were detected on a Ca-ISE. The detectable electronic signal increased with the increasing target concentration. By monitoring the shift in the potential, the concentration of the analyte could be quantitatively evaluated by using a portable ion-selective electrode. Importantly, our strategy can be readily applied in other electrochemical detection systems (e.g., DNA sensors, immunosensors and aptasensors) by controlling the corresponding labels on the CaCO3 nanospheres.

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