A Non-Enzymatic and Label-Free Fluorescence Bioassay for Ultrasensitive Detection of PSA

The early diagnosis of prostate cancer is very vital for the improvement of patient survival chances. The content of prostate specific antigen (PSA) in serum is closely related to the status of the prostate cancer. We report a fluorescence bioassay, capable of detecting PSA in a non-enzymatic and label-free manner. PSA gives rise to the structural change of a hairpin, consequently triggering the hybridization chain reaction and forming a long-nicked double-helix, which is not adsorbed by graphene oxide. GelRed, as the signal indicator, then binds with dsDNA molecule, thereby producing the fluorescence. The established bioassay has the merits of simple operation, favorable cost-to-benefit ratios, good stability, and specificity. Moreover, the detection limit of this assay is as low as 10 pg/mL, and the linearity range is wide—from 100 pg/mL to 200 ng/mL. At the same time, this bioassay can realize the detection of PSA in biological samples (human serum, saliva, and urine). Therefore, the bioassay provides a potential means for the early diagnosis of prostate cancer.