We report results of the studies relating to the fabrication of a label-free, flexible, light weight and disposable conducting paper based immunosensing platform comprising of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) and nanostructured iron oxide (nFe2O3@PEDOT:PSS) nanocomposite for detection of carcinoembryonic antigen (CEA), a cancer biomarker. The effect of various solvents such as sorbitol, ethanol, propanol, n-methyl-2-pyrrolidone (NMP) and dimethyl sulfoxide (DMSO) on the electrical conductivity of Whatman filter paper (WP) modified with nFe2O3@PEDOT:PSS/WP was investigated. The electrical conductivity of the PEDOT:PSS/WP electrode was found to be enhanced by two orders of magnitude (from 6.8× 10-4 to 1.92 × 10-2 Scm-1) after its treatment with DMSO. Further, nFe2O3 doped PEDOT:PSS/WP electrode exhibited the electrical conductivity as 2.4 × 10-2 Scm-1. Besides this, the incorporation of iron oxide nanoparticles (nFe2O3) into PEDOT:PSS/WP resulted in improved electrochemical performance and signal stability. This nFe2O3@PEDOT:PSS/WP based platform was used for immobilization of the anti-carcinoembronic antigen (anti-CEA) protein for quantitative estimation of cancer biomarker (CEA). The results of electrochemical response studies revealed that this conducting paper based immunoelectrode had a sensitivity of 10.2 μAng-1mLcm-2 in the physiological range (4-25 ngmL-1) and shelf life of 34 days. Further, the proposed immunoelectrode was validated with conventional ELISA for the detection of CEA in serum samples of cancer patients.
Keywords: Biosensor; Electrochemical paper; Iron oxide nanoparticles; PEDOT:PSS.
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