β-1,4-Galactosyltransferase-V colorectal cancer biomarker immunosensor with label-free electrochemical detection.

β-1,4-Galactosyltransferase-V (β-1,4-GalT-V) is a membrane-bound glycoprotein with glycosyltransferase enzyme activity that synthesizes lactosylceramide and glycosylates high-branched N-glycans in the Golgi apparatus. Colorectal cancer (CRC) tumor cells have shown to overexpress these biomolecules concerning normal cells, releasing them into the body fluids. Thus, their detection has been suggested as a diagnosis/prognosis CRC biomarker. We report the first electrochemical immunosensor for the detection of such a novel β-1,4-GalT-V CRC biomarker. The label-free electrochemical immunosensor covalently coupled an anti-β-1,4-GalT-V antibody at a mixed self-assembled monolayer-coated screen-printed gold electrode (SPAuE) surface. This functionalized platform captured the β-1,4-GalT-V glycoprotein from human serum samples with high specificity, which response monitored by electrochemical impedance spectroscopy (EIS) was protein concentration-dependent. The resultant electrochemical immunosensor showed a linear dynamic range from 5 to 150 pM, with a sensitivity of 14 Ω pM and a limit of detection of 7 pM, of clinical relevance. This outstanding performance makes it great potential for including it in a biomarker signature for the early diagnosis/prognosis of CRC.