Electrochemical paper based cancer biosensor using iron oxide nanoparticles decorated PEDOT:PSS

Highlights: • PEDOT:PSS and nanostructured iron oxide modified conducting paper sensor has been reported for cancer biomarker detection. • The electrical conductivity of the paper electrode has been enhanced by two orders of magnitude after treatment with DMSO. • It exhibits high sensitivity of 10.2 μA ng⁻¹mL cm⁻² in the detection range of 4–25 ngmL⁻¹ for CEA detection. • It may be a promising alternative over the expensive conventional electrodes (ITO, gold and glassy carbon). -- Abstract: 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.