Homogeneous label-free genotyping of single nucleotide polymorphism using ligation-mediated strand displacement amplification with DNAzyme-based chemiluminescence detection.

Genotyping of single nucleotide polymorphisms (SNPs) is a central challenge in disease diagnostics and personalized medicine. A novel label-free homogeneous SNP genotyping technique is developed on the basis of ligation-mediated strand displacement amplification (SDA) with DNAzyme-based chemiluminescence detection. Discrimination of single-base mismatches is first accomplished using DNA ligase to generate a ligation product between a discriminant probe and a common probe. The ligated product then initiates two consecutive SDA reactions to produce a great abundance of aptamer sequences against hemin, which can be probed by chemiluminscence detection. The developed strategy is demonstrated using a model SNP target of cytochrome P450 monooxygenase CYP2C19*2, a molecular marker for personalized medicines. The results reveal that the developed technique displays superb selectivity in discriminating single-base mismatches, very low detection limit as low as 0.1 fM, a wide dynamic range from 1 fM to 1 nM, and a high signal-to-background ratio of 150. Due to its label-free, homogeneous, and chemiluminescence-based detection format, this technique can be greatly robust, cost-efficient, readily automated, and scalable for parallel assays of hundreds of samples. The developed genotyping strategy might provide a robust, highly sensitive, and specific genotyping platform for genetic analysis and molecular diagnostics.