In situ hybridization chain reaction mediated ultrasensitive enzyme-free and conjugation-free electrochemcial genosensor for BRCA-1 gene in complex matrices

In this study, we report an enzyme-free and conjugation-free electrochemical genosensor enabling an ultrasensitive readout of BRCA-1, a breast cancer susceptibility gene. The sensor employs a target-responsive hybridization chain reaction (HCR) to significantly amplify the detectable current signals. By means of a functional auxiliary probe pair and a versatile initiator sequence, a linear DNA concatemer structure can be formed via spontaneous and continuous polymerization of DNA oligomers in the presence of target sequence. Such a DNA nanoassembly endows the genosensor an ultrahigh sensitivity up to 1 aM, which is higher than that of the nanomaterials-based or enzyme mediated amplification approaches by several orders of magnitude. More importantly, the sensor's responsive peak current exhibits a favorable linear correlation to the logarithm of the concentrations of target sequence ranging from 1 aM to 10 pM. In addition, the sensor is highly selective, and can discriminate a single mismatched sequence. This HCR-based genosensor is also capable of probing low-abundance BRCA-1 gene sequence directly in complex matrices, such as 50% human serum, with minimal interference. These advantages will make our tailor-engineered HCR-based electrochemical genosensor appealing to genetic analysis and clinical diagnostics.