Sensitive determination of prostate-specific antigen with graphene quantum dot-based fluorescence aptasensor using few-layer V2CTx MXene as quencher

A novel fluorescence aptasensor of prostate-specific antigen (PSA) was established using few-layer vanadium carbide (FL-V2CTx) nanosheet as a quencher. First, FL-V2CTx was prepared by the delamination of multi-layer V2CTx (ML-V2CTx) with tetramethylammonium hydroxide. The aptamer-carboxyl graphene quantum dots (CGQDs) probe was prepared by combining the aminated PSA aptamer and CGQDs. Then, the aptamer-CGQDs were absorbed onto the surface of FL-V2CTx by hydrogen bond interaction, which led to the decrease in fluo-rescence of aptamer-CGQDs due to photoinduced energy transfer. After addition of PSA, PSA-aptamer-CGQDs complex was released from FL-V2CTx. The fluorescence intensity of aptamer-CGQDs-FL-V2CTx with PSA was higher than that without PSA. The FL-V2CTx-based fluorescence aptasensor provided a PSA detection linear range from 0.1 to 20 ng mL-1 with detection limit of 0.03 ng mL-1. The Delta F value of fluorescence intensities for aptamer-CGQDs-FL-V2CTx with and without PSA was 5.6, 3.7, 7.7, and 5.4 times of ML-V2CTx, few-layer titanium carbide (FL-Ti3C2Tx), ML-Ti3C2Tx and graphene oxide aptasensors, respectively, indicating the advantage of FL-V2CTx. The aptasensor had high selectivity for PSA detection compared with some proteins and tumor markers. This proposed method had convenience and high sensitivity for PSA determination. The determination results of PSA in human serum samples using the aptasensor were consistent with those by chemiluminescent immu-noanalysis. The fluorescence aptasensor can be successfully applied for PSA determination in serum samples of prostate cancer patients.