Bioengineers at the University of California, San Diego have developed an electrical graphene chip capable of detecting mutations in DNA. Researchers say the technology could one day be used in various medical applications such as blood-based tests for early cancer screening, monitoring disease biomarkers and real-time detection of viral and microbial sequences. The advance was published June 13 in the online early edition of Proceedings of the National Academy of Sciences.
The chip essentially works by performing DNA strand displacement, the process in which a DNA double helix exchanges one strand for another complementary strand. The new complementary strand—which, in this case, contains the single nucleotide mutation—binds more strongly to one of the strands in the double helix and displaces the other strand. In this study, the DNA probe is a double helix containing two complementary DNA strands that are engineered to bind weakly to each other: a “normal” strand, which is attached to the graphene transistor, and a “weak” strand, in which four the G’s in the sequence were replaced with inosines to weaken its bond to the normal strand. DNA strands that have the perfectly matching complementary sequence to the normal strand—in other words, strands that contain the SNP—will bind to the normal strand and knock off the weak strand. Researchers engineered the chip to generate an electrical signal when an SNP-containing strand binds to the probe, allowing for quick and easy SNP detection in a DNA sample.