A label-free genosensor for BRCA1 related sequence based on impedance spectroscopy

Abstract

A simple approach based on electrochemical impedance spectroscopy of a DNA hybridization sensor for breast cancer is reported by immobilizing a BRCA1 related 19 mer oligonucleotides ssDNA sequence on a glassy carbon electrode modified with a poly 5-carboxyindole conducting polymer. Differential pulse voltammetry, UV-vis spectrophotometry, FT-IR and impedance spectroscopy are performed for the study of electropolymerization of 5-carboxyindole, chemical immobilization of ssDNA and the hybridization event at the electrode surface. A significant change is observed in the impedance spectra before and after hybridization of ssDNA with the target probe under optimum conditions. The above described technique is found to be efficient enough to detect a single base mismatch in a target DNA sequence. All the experiments are performed in Tris-HCl buffer 20 mM (pH 6.5). A detection limit of 1 × 10⁻¹⁷ M with a linear range from 1 × 10⁻⁸ to 1 × 10⁻¹⁸ is obtained after hybridization for the optimum time period. The proposed method is simple, free from any redox indicator/marker and possesses high sensitivity and selectivity. This technique is successfully demonstrated for detection of a single base mutation in a BRCA1 related sequence.