Search

Sensitivity amplification strategy by implementing click chemistry in the construction of biosensing interface can efficiently improve the performance of immunosensor. Herein, we developed a sandwich-type amperometric immunosensor for ultrasensitive detection of carbohydrate antigen 24-2 (CA 242) based on pH responsive label-assisted click chemistry triggered sensitivity amplification strategy. The sensitivity of amperometric immunosensor relies on the current response differences (ΔI) caused by per unit concentration target analyte. The pH responsive Cu 2+ -loaded polydopamine (CuPDA) particles conjugated with detection antibodies were employed as labels, which can release Cu(II) ions by regulating pH. In the presence of ascorbic acid (reductant), Cu(II) ions were reduced to Cu(I) ions. Azide-functionalized double-stranded DNA (dsDNA) as signal enhancer was immobilized on the substrate through Cu + -catalyzed azide/alkyne cycloaddition reaction. With the help of the click reaction, the ΔI caused by target was elevated prominently, resulting in sensitivity amplification of the immunosensor. Under optimal condition, the proposed immunosensor exhibited excellent performance with linear range from 0.0001 to 100 U mL −1 and ultralow detection limit of 20.74 μU mL −1 . This work successfully combines click chemistry with pH-responsive labels in sandwich-type amperometric immunosensor, providing a promising sensitivity amplification strategy to construct immunosensing platform for analysis of other tumor marker. [ABSTRACT FROM AUTHOR]

A new screen-printed carbon electrode (SPCE) with multiple working electrodes and one signal output channel without counter and reference electrodes was designed. The multiple working electrodes can be individually modified for each target of interest. The SPCE contained one signal output channel, making the immuniosensor be realized by common single-channel electrochemical workstation. The counter and reference electrodes were independent of disposable SPCE, reducing costs and eliminating precious metal pollution. Platinum network as counter electrode improved the reproducibility of the SPCE. Moreover, method of generating hydrogel on working electrode was used to enhance the conductivity of SPCE. Based on this, a multiplexed single channel label-free amperometric immuniosensor for four tumor markers, namely, squamous cell carcinoma antigen (SCCA), fragment antigen 21-1 (Cyfra21-1), carbohydrate antigen 125 (CA125), and neuron specific enolase (NSE) was developed, and the corresponding detection limits were 5.5 pg mL −1 , 4.8 pg mL −1 , 0.0054 U mL −1 and 2.3 pg mL −1 , respectively. The sensitivity of this immunosensor was 0.83 µA (lg(ng mL −1 )) −1 for SCCA, 1.92 µA (lg(ng mL −1 )) −1 for Cyfra21-1, 4.75 µA (lg(U mL −1 )) −1 for CA125 and 2.40 µA (lg(ng mL −1 )) −1 for NSE. Among them, the sensitivities of CA125 and NSE were four-fold higher than those of the previous works. [ABSTRACT FROM AUTHOR]