Biosensor array based on the in situ detection of quantum dots as electrochemical label

A simple, fast, and inexpensive miniaturized electrochemical biosensor array with in situ detection of CdSe/ZnS quantum dots (QDs) is presented.This biosensor uses the affinity reaction between streptavidin and biotin, for biotin determination, but the methodology could be extended to other clinical biomarkers. Individual screen-printed carbon electrodes (SPCEs) and 8-channel screen-printed carbon electrochemical arrays (8xSPCEs) were modified with streptavidin and its analytical performance was evaluated using QDs labeled biotin (biotin-QD). After the biological reaction, Cd2+ ions released from the dissolution of the nanoparticles were determined in situ by voltammetric stripping. A linear range of 5 × 10−10–5 × 10−9 M and a limit of detection of 2 × 10−10 M (in terms of QD) were achieved for SPCEs (5.0% RSD, n = 3). For 8xSPCEs, a linear range of 1 × 10−9–1.2 × 10−8 M and a limit of detection of 3 × 10−10 M (in terms of QD) were obtained (8.5% RSD, n = 3). A one-step competitive bioassay between biotin and biotin-QD was carried out using the biosensor array. A linear range of two orders of magnitude (1 × 10−9–1 × 10−7 M) and a limit of detection of 1.4 × 10−9 M were achieved for biotin (6.4% RSD, n = 3).