Au-IDE/LFA biosensor: an integrated sensing platform with lateral flow immunoassay for quantitative detection of hCG hormone using non-faradaic continuous FFT-admittance voltammetry

The development of the novel Au-IDE/LFA (gold interdigitated electrode with lateral flow immunoassay) biosensor, an integrated electrochemical sensing platform with lateral flow immunoassay, for quantitative detection of hCG (human Chorionic Gonadotropin) hormone levels is successfully directed here. To fabricate the Au-IDE/LFA setup, a free multi-electrode array of AU-IDE was configured exactly on five zones of LFA on the flow direction, employing non-faradaic measurements through a combination of two electrodes. The impedance behavior of each zone, connected with an Au surface electrode in the Au-IDE/LFA setup was characterized by frequency response analysis (FRA) using non-faradaic electrochemical impedance spectroscopy. Precisely, FRA validated that Au surfaces exhibit similar current homogeneity due to produce the repeatable impedance. The assay optimization using CFFT (Continuous Fast Fourier Transform)-admittance voltammetry, a new method, pinpointed that optimizing the excitation potential by utilizing lower SW frequencies at 88 Hz, amplitude at 10 mV, and DC potential at 10 mV resulted in excellent admittance responses of Au-IDE/LFA biosensor. Both bare and standard LFA were used for signal baseline establishment to ignore the background signal noise induced by the anti-β-hCG-AuNPs (6.01 µA/V), PBS buffer (11.51 µA/V), and urine background (22.11 µA/V). Admittance response showed a high sensitivity about three times more than impedance response with limit of detection by 2.53 mIU/mL in a linear range of 5-500 mIU/mL for hCG with R²= 0.998. This performance metric was utilized to determine the performance efficiency of proposed biosensor. The lack of any cross-interference with other human hormone like hCG and discriminating beta unit from alpha unit of hCG confirmed high selectivity and specificity of fabricated biosensor. The functional performance of biosensor resulted in the direct and quantitative detection of the native hCG in urine biological matrix, which offers a promising approach with high potential for early diagnosis of pregnancy test in clinical samples.