Label-free photoelectrochemical immunosensor based on sensitive photocatalytic surface of Sn doped ZnO for detection of hepatitis C (HCV) anticore mAbs 19D9D6

Photoelectrochemical (PEC) based immunosensors are important bioanalytical tools for the label free detection of hepatitis C (HCV) antibodies as the photocurrent in the external circuit which is the response signal is not effected intrinsically by the excitation stimulus of light. Therefore, in this article, the facile development of label-free photoelectrochemical (PEC) immunosensor for the detection of hepatitis C (HCV) anticore mAbs 19D9D6 (1 NLB monoclonal antibodies) is reported. The photoactive ZnO was applied as matrix which was further doped with Sn in order to enhance the PEC properties for constructing the PEC immunosensor through immobilization of truncated recombinant HCV core nucleocapsid polypeptide antigen (residues 13–40) corresponding to immunodominant region as biolayer for immunospecific interaction. Morphological analysis was carried out using Scanning electron microscopy (SEM). X-ray diffraction (XRD) was performed for the structural analysis of the pure ZnO and Sn doped ZnO matrix. Optical properties were evaluated using the UV–visible spectroscopy that was further used to attain Mott–Schottky plot, Tauc plot and Urbach plot that explained in detail the PEC enhancement in terms of the energy band gap (Eg). The results depicted a significant red shift in the light absorption by Sn-doped ZnO electrode due to band shrinkage. Defect sites induced due to doping also hinders the photo-generated electron-hole pair recombination. Consequently, the photocurrent density of Sn doped ZnO electrode increased approximately two fold when subjected to illumination. The insulative layer formation at the semi-conductor solution junction resulted in a significant decrease in the photocurrent density that was successfully applied to monitor the immunospecific interaction between the antigen and antibody. PEC immunosensor has the linear detection range from 0.006 to 60 ng mL⁻¹ anticore mAbs 19D9D6 (1 NLB monoclonal antibodies) concentration with 0.53 pg mL⁻¹ (S/N = 3) detection limit as a function of photocurrent decrement which is low for enhancing the sensitivity to effectively measure the antibody. The as prepared PEC immunosensor displayed high selectivity and stability due to which it can be rendered as capable photoelectrochemical scheme for protein detection in the point of care medical diagnosis.