Chitosan/polyaniline hybrid conducting biopolymer base impedimetric immunosensor to detect Ochratoxin-A

Chitosan (CS)-polyaniline (PANI) hybrid conducting biopolymer film was obtained on indium-tin-oxide (ITO) electrode using electrochemical polymerization process. Fourier transform infrared (FT-IR) spectra of PANI-CS had showed covalent and hydrogen binding between PANI and CS molecules. Electrochemical impedance spectroscopy (EIS) measurements had showed low charge transfer resistance (R(CT)) of PANI-CS and PANI. Successive rabbit antibody (IgGs) immobilization on PANI-CS, CS and PANI matrixes surface were confirmed with FT-IR and EIS measurements. Ochratoxin-A (OTA) interaction with IgGs had increased R(CT) values and showed linear response up to 10 ng/mL OTA concentration in electrolyte. Relative change in R(CT) was higher in PANI-CS due to higher proportion of carboxylic and hydroxyl functionalities at PANI-CS matrix surfaces. The absolute sensitivity of PANI, CS, and PANI-CS were 16+/-6, 22+/-9 and 53+/-8 Omega mL/ng, respectively derived from slope of linear response up to 10 ng/mL with 1 ng/mL minimum detection limit.