Molybdenum disulfide field-effect transistor biosensor for ultrasensitive detection of DNA by employing morpholino as probe

This work reports on a molybdenum disulfide (MoS2) based field-effect transistor (FET) biosensor for ultra sensitive label-free detection of DNA via phosphorodiamidate morpholino oligos (PMO)-DNA hybridization. After the chip was fabricated and the sensing channel was modified with positive charges, the negatively charged MoS2 nanosheet was drop-casted onto the channel, enabling MoS2 to tightly bind to the sensing surface via electrostatic interactions. Meanwhile, DNA analogue, PMO, was immobilized on the MoS2 surface, and detection of PMO-DNA hybridization was conducted by the fabricated MoS2 FET biosensor. Due to the neutral character and high affinity of PMO, a limit of detection (LOD) down to 6 fM was obtained, which is lower than that of the previously reported MoS2 FET DNA biosensor based on DNA-DNA hybridization. In addition, the MoS2 FET biosensor also showed high sequence specificity capable of distinguishing the complementary DNA from one base mismatched DNA, three-base mismatched DNA and noncomplementary DNA. Moreover, the unique FET biosensor was able to detect DNA in complex sample like serum, making the method potential in disease diagnostics.