Amplified using DNase I and aptamer/graphene oxide for sensing prostate specific antigen in human serum

In this paper, we proposed an amplified assay using DNase I for sensitively sensing prostate specific antigen (PSA) based on CdSe/ZnS quantum dot labelled PSA aptamer/graphene oxide (QD-aptamer/GO). In this sensing system, GO could strongly bind QD conjugated aptamer and quench the fluorescence of QD, furthermore, GO could protect DNA from nuclease cleavage. When binding target PSA, aptamer probe released from the surface of GO nanosheet, then the free aptamer could be cleaved by nuclease, thus the QD and PSA were liberated, after that, the released PSA would bind another aptamer on GO nanosheet and start a new cycle, which resulted in amplification of restoring signal. The probe possessed steady fluorescence signal and high specificity due to the anti photobleaching of QD and the high affinity of aptamer to PSA. Under the optimum experimental conditions, fluorescence intensity increased linearly with the PSA concentration between 0.1 fg mL⁻¹and 3 fg mL⁻¹with the limit of quantification of 0.05 fg mL⁻¹, which was three orders of magnitude lower than that without DNase I. Finally, the method was applied to quantification of PSA in human serum samples.