Development of an electrochemical DNA biosensor for detection of breast cancer gene

Breast cancer is one of the leading causes of death in women worldwide [1]. Several inherited gene mutations have been linked to breast cancer, mostly associated to the tumor suppressor gene BRCA1, which is known as a kind of anti-oncogene and one of the most important breast cancer susceptibility gene [2]. Hence, the detection of BRCA1 offers an opportunity to characterize the function of genetic features in breast cancer as well as to screen breast cancer patients for the presence of germ line mutations [3]. An impedimetric BRCA1 gene biosensor has been developed based on carbon nanotbe-Nafion composite film. The resultant nanocomposite can provide a large surface area, excellent electrocatalytic activity, and high stability, which would improve immobilization sites for biological molecules, allow remarkable amplification of the electrochemical signal and contribute to improved sensitivity. The biosensor was fabricated by adsorbing the single-stranded DNA (ssDNA) on carbon nanotbe-Nafion modified on the surface of glassy carbon electrode via the π–π* stacking interactions. As the negative ssDNA and the steric hindrance, the electron transfer resistance of the electrodes toward the [Fe(CN)6]3-/4- redox couple was difficult, the electron transfer resistance value increased. In the measurement of BRCA1 gene, ssDNA probe with the target DNA to form double-stranded DNA (dsDNA), the formation of helix induced increase in the electron transfer resistance that was in logarithmically direct proportion to the concentration of BRCA1 gene over a range from 1.0 × 10-15 to 1.0 × 10-12 M. The detection limit of this sensor was 7.0 × 10-16 M. The results demonstrate that this carbon nanotbe-Nafion biosensor possesses good selectivity, acceptable stability and reproducibility for BRCA1 gene detection.