UC San Diego

Single nucleotide polymorphisms (SNP) in a gene sequence are markers for variety of human diseases. Their detection with high specificity and sensitivity is essential for effective practical implementation of personalized medicine. Current DNA sequencing, including SNP detection, primarily uses enzyme based methods or fluorophore-labeled assays that are time consuming, need lab-scale settings, and are expensive. Electrical detection of DNA has been advancing rapidly, with to achieve high specificity, sensitivity and portability. However, existing electrical charge-based SNP detectors have insufficient specificity and accuracy limiting their effectiveness. Its actual implementation is still in infancy because of the low specificity, especially for analytically optimal and practically useful length of target DNA strands. Most of the research so far has focused on the enhancement of the sensitivity of DNA biosensors while the specificity problem has remained unresolved. The low specificity is primarily due to the non-specific binding during hybridization of probe and the target DNA. Here, we have addressed these limitations by designing a functional prototype of electrical biosensors for SNP detection. We demonstrate the use of DNA strand displacement-based probes on a graphene field effect transistor (FET) for high specificity single nucleotide mismatch detection. The single mismatch was detected by measuring strand displacement-induced resistance (and hence current) change and Dirac point shift in a graphene FET. SNP detection in large double helix DNA strands (e.g., 47 nucleotides) minimize false positive. We describe the first integrated dynamic DNA nanotechnology and 2-D material electronics, to overcome current limitations for the detection of DNA single nucleotide polymorphism (SNP). Existing SNP detection systems have poor sensitivity and specificity and lack portability and real-time wireless transmission of detected molecular signals. We have integrated two different kinds of dynamic DNA nano-devices as nucleic acid-sensing probes with electrical biosensors using graphene FET and analytical wireless communication platform. The signal was transmitted remotely using a microcontroller board and Bluetooth standard to personal electronics, including smart phones, tablets and computers. Our electrical sensor-based SNP detection technology without labeling and without apparent cross-hybridization artifacts would allow fast, sensitive and portable SNP detection with single-nucleotide resolution. Practical implementation of this enabling technology will provide cheaper, faster and portable point-of-care molecular diagnostic devices for personalized global health management. It will have wide applications in digital and implantable biosensors and high-throughput DNA genotyping with transformative implications for personalized medicine.