Biofunctionalized Gold Nanoparticle-Conducting Polymer Nanocomposite Based Bioelectrode for CRP Detection
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An electrochemical impedance immunosensing method for the detection and quantification of C-reactive protein (αCRP) in phosphate buffered saline (PBS) is demonstrated. The protein antibody, Ab-αCRP, has been covalently immobilized on a platform comprising of electrochemically deposited 3-mercaptopropionic acid-capped gold nanoparticles Au(MPA)-polypyrrole (PPy) nanocomposite film of controlled thickness onto an indium tin oxide-coated glass plate. The free carboxyl groups present on the nanocomposite film have been used to site-specifically immobilize the Ab-αCRP biomolecules through a stable acyl amino ester intermediate generated by N-(3-dimethylaminopropyl)-N′-ethyl carbodiimide hydrochloride and N-hydroxysuccinimide. The nanocomposite film was characterized by atomic force microscopy, high-resolution transmission electron microscopy, Fourier transform infrared spectroscopy, and electrochemical techniques. The bioelectrode was electrochemically analyzed using modified Randles circuit in terms of constant phase element (CPE), electron transfer resistance (R et), and Warburg impedance (Z w). The value of n, a CPE exponent used as a gauge of heterogeneity, for the Au-PPy nanocomposite film was found to be 0.56 which is indicative of a rather rough morphology and porous structure. A linear relationship between the increased ∆R et values and the logarithmic value of protein antigen, Ag-αCRP, concentrations was found in the range of 10 ng to 10 μg mL−1 with a R et sensitivity of 46.27 Ω cm2/decade of [Ag-αCRP] in PBS (pH 7.4).
KeywordsElectrochemical impedance spectroscopy Conducting polymer Gold nanoparticles Protein immobilization
We are grateful to Prof. R. C. Budhani, Director, National Physical Laboratory, New Delhi, India for providing the facilities. S.K. Mishra is thankful to the Council of Scientific and Industrial Research, India for providing a senior research fellowship (SRF). We also acknowledge Mr. Sandeep Singh for AFM measurements.
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