Functionalized Thiophene-Based Aptasensors for the Electrochemical Detection of Mucin-1

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Mucin-1 (MUC1) is a glycoprotein found in epithelial tissues; its function is to protect the body by blocking pathogens from reaching the cells. Overexpression and elevated serum levels of this protein are observed in breast cancer, lung cancer, stomach cancer, ovarian cancer, and many other types of malignancies. Current methods used to detect cancer are expensive and therefore not readily accessible; some methods are also invasive. The ability to detect MUC1 could allow for early detection of cancer, leading to more successful outcomes. This research focuses on the development of a robust biosensor platform based on aptamer-functionalized electroactive polymers (EAPs) that can be used for the detection of cancer. To achieve this, indium tin oxide slide surfaces were modified to enable the electrochemical growth of an electroactive copolymer of 3,4-ethylenedioxythiophene (EDOT) and 2,2-(3,4-dihydro-2H-thieno[3,4-b][1,4]dioxepine-3,3-diyl)diacetic acid (ProDOT(COOH)₂), with the carboxylic acid functionalities added to introduce bonding sites for a MUC1-specific aptamer. Three copolymer ratios were investigated to maximize the performance. The aptamer was then attached to the EAPs to create aptasensors that could be used for the electrochemical detection of a MUC1 polypeptide. The limits of detection of the biosensors and their stabilities were evaluated. The MUC1 aptasensor showed stability for at least 6 days, depending on the ratio of the copolymer, when stored in 0.1 M phosphate-buffered saline. The 1:2 EDOT/ProDOT(COOH)₂ copolymer was found to be the most stable over time and to offer one of the smallest limits of detection, making it the most favorable ratio for aptasensor optimization. Specifically, the 1:2 EDOT/ProDOT(COOH)₂ biosensor provided a limit of detection of 369 fg/mL (418 fM) and a linear range of 625 fg/mL to 6.25 ng/mL (709 fM to 7.09 nM) with the MUC1 peptide APDTRPAPG. The sensor also showed selectivity when tested with competing agents including IgG and cell media. The performance of the aptasensor demonstrated its potential as a highly sensitive and selective biosensor for MUC1 detection.