Electrochemical Biosensor for the Diagnosis of Breast Cancer Using ssDNA Aptamer

The BRCA1 gene encodes a DNA repair protein , in many cell types in the human body. Mutations in BRCA1 gene are the cause of breast cancers. This work focuses on the detection of the BRCA1 gene in breast cancer using novel aptamers and a label-free electrochemical biosensor. Single-stranded DNA aptamers were attached to multi-walled carbon nanotubes. These were then drop casted onto a screen-printed carbon electrode using polyvinyl alcohol and glutaraldehyde. The biosensor so developed is capable of detecting the BRCA1 gene with high specificity and sensitivity. After fabrication the electrode was allowed to hybridize with a complementary ssDNA. Anthraquinone monosulphonic acid was used as a redox intercalator for the detection of the hybridized double-stranded DNA on the electrode . The reductive signal of the redox intercalator decreased in the presence of base pair mismatches. The increase in the current upon hybridization is directly correlated with the concentration of the complementary target DNA. The response to target DNA concentration showed an excellent linear relationship from 1 × 10-16 M to 1 × 10-4 M (R2 = 0.9641), with a limit of detection at 1 × 10-18 M, avoiding the requirement for the amplification of complementary DNA.