DNA-based functionalization of two-dimensional MoS₂ FET biosensor for ultrasensitive detection of PSA

Molybdenum disulfide (MoS₂) field-effect transistor (FET) biosensors are being increasingly studied due to their highly sensitive and label-free biodetection, system-level integration and easy fabrication. However, the stability and detection ability of a pristine device deteriorate due to the absorption of H₂O and CO and usually exhibit high false signals. Herein, a novel ecofriendly technology is employed to functionalize MoS₂ FETs using the conjugation of a DNA tetrahedron and biotin-streptavidin (B-SA). The functionlized devices demonstrate ultrahigh sensitivity of the target protein (prostate-specific antigen, PSA) with a limit of detection of 1fg/mL and a wide linear range of 1fg/mL to 100ng/mL in a phosphate-buffered saline, which are 100 and 10,000 times higher than the reported highest values, respectively; these results are attributed to the stable immobilization provided by the DNA tetrahedron as well as the multilevel amplification and anchor system (B-SA system), which improves the antibody-antigen (Ab-Ag) binding. Real-time measurement results indicate that our proposed biosensor can also detect trace PSA (1fg/mL) in a clinically relevant sample of healthy human serum.