We report real-time voltammetric detection of potential lung cancer biomarkers, namely, interleukin-10 (IL-10) and osteopontin (OPN), using localized silica nanowires as templates, through an electrochemical alkaline phosphatase (AP) based assay. The high surface to volume ratio associated with nanowires enhances the loading of a specific capture antibody toward a particular cancer antigen. An AP enzyme attached to the cancer antigens (IL-10 and OPN) via detector antibodies hydolyses (dephosphorylates) the p -nitrophenyl phosphate substrate to a yellow, water-soluble product, p -nitrophenol (pNP). This was detected in a small test volume of 3 μL, using a microelectrode cell fabricated in Au. The electro-oxidation of pNP occurs between 0.85 and 0.9 V with anodic peak current showing linear dependence with the capture antibody and antigen concentrations, respectively. The detection of IL-10 down to 1 fg/mL in ideal pure solution and 1 pg/mL in clinically relevant samples was achieved reproducibly. Moreover, both the concentration of the capture antibody and the cancer antigen were found to have a strong influence on the anodic peak current, as demonstrated considering specific example of OPN.
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Ramgir et al. (2007) studied this question.
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