Rapid and sensitive detection of prostate-specific antigen via label-free frequency shift Raman of sensing graphene.

The sensitive and accurate detection of cancer biomarkers is critically important to early clinical diagnosis, disease monitoring, and successful cancer treatment. Here, we first demonstrate an aptamer-based frequency shift Raman approach via sensing of graphene. This biosensor allows the rapid, sensitive, and label-free detection of the acknowledged protein cancer biomarker, prostate-specific antigen (PSA). Monolayer graphene is employed as the Raman substrate, which is highly sensitive to its electronic structure and interface properties. The PSA aptamer can be adsorbed strongly on the surface of substrates through π-π stacking interactions. The vibrational frequency of the G peak of graphene shifted upon the specific binding between the PSA and its aptamer. The corresponding frequency shifts of the G peak are directly correlated with PSA concentrations. The limit of detection is as low as 0.01 ng/mL, with a wide linear range from 0.05 ng/mL to 25 ng/mL. The analytic samples can be detected directly without any extensive preparation and label process. The whole detection is completed in only 30 min. Furthermore, excellent recoveries are acquired to validate the feasibility of this assay in human serum samples. The proposed technology could provide a selective, versatile, and user-friendly strategy for the early detection of cancer biomarkers.