Improved screen-printed carbon electrode for multiplexed label-free amperometric immuniosensor: Addressing its conductivity and reproducibility challenges

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.