Abstract
We report a protocol of CdS-labeled sandwich-type amperometric bioanalysis with high sensitivity, on the basis of simultaneous chemical-dissolution/cathodic-enrichment of the CdS quantum dot biolabel and anodic stripping voltammetry (ASV) detection of Cd directly on the bioelectrode. We added a microliter droplet of 0.1 M aqueous HNO3 to dissolve CdS on the bioelectrode and simultaneously achieved the potentiostatic cathodic preconcentration of Cd by starting the potentiostatic operation before HNO3 addition, which can largely increase the ASV signal. Our protocol was used for immunoanalysis and aptamer-based bioanalysis of several proteins, giving limits of detection of 4.5 fg·mL−1 for human immunoglobulin G, 3.0 fg·mL−1 for human carcinoembryonic antigen (CEA), 4.9 fg·mL−1 for human α-fetoprotein (AFP), and 0.9 fM for thrombin, which are better than many reported results. The simultaneous and sensitive analysis of CEA and AFP at two screen-printed carbon electrodes was also conducted by our protocol.
Highlights
Bioanalysis on the basis of a variety of bioaffinity events that are naturally of high specificity has attracted great academic and industrial attention [1–3]
Improving the bioanalysis sensitivity is widely concerned in many areas including biomedical and environmental analysis [4–6]
A KCl-saturated calomel electrode (SCE) of a small-sized salt bridge filled with saturated KNO3 served as the reference electrode (RE)
Summary
Bioanalysis on the basis of a variety of bioaffinity events that are naturally of high specificity has attracted great academic and industrial attention [1–3]. Various biolabeling strategies are frequently used in bioaffinity-based bioanalysis, because the bioaffinity events usually fail to directly give great analytical signals [7–9]. Two kinds of biolabeling protocols have been reported for the bioaffinity-based bioanalysis to date, i.e., molecule-level biolabeling Various optical and electrochemical methods as well as their hyphenation with chromatographic or magnetic separation have been widely employed in bioanalysis [18,19]. Electrochemical methods have been intensively explored for rapid bioanalysis due to the high sensitivity and selectivity, low limits of detection (LODs), facile operation, simple instrumentation, and scope for miniaturization [20–22]
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