Research on colon cancer diagnosis is advancing due to the application of electrochemical biosensors. Early screening can significantly reduce the overall mortality rate from colorectal cancer (CRC). Colon cancer-secreted protein-2 (CCSP-2) is specifically overexpressed and secreted by cancerous cells and adenomas found in the colon. Utilizing a cost-effective and non-invasive electrochemical immunosensor for CCSP-2 detection can aid in the early diagnosis of disease recurrences in individuals with colon cancer. In this work, we designed a simplified electrochemical immunosensor consisting of a functionalized gold (Au) electrode using cysteine-modified recombinant protein G (RPGCys) to immobilize the CCSP-2 antibody. Electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) have been used to analyze the electrochemical response caused by the binding between the target CCSP-2 and anti-CCSP-2, and there are significant changes observed for charge transfer resistance (Rct) in EIS and current density in CV. The quantification of mass changes attributed to binding events within the sensor will be determined through the application of quartz crystal microbalance (QCM). Angle-resolved X-ray photoelectron spectroscopy (ARXPS) and atomic force microscopy (AFM) will be used for the characterization of the sensor surface. The sensor's sensitivity and specificity will be assessed through the determination of the limit of detection and comprehensive testing of the probe with varied proteins and cell lines sourced from both cancerous and non-cancerous patient samples. This electrochemical probe is expected to enable the rapid and direct detection of early-stage colorectal cancer.
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