Determination of PSA by a label-free fluorescent aptasensor based on the on and off of the AIEE effect

Fluorescent organic compounds with aggregation-induced emission enhancement (AIEE) effect are playing an increasingly important role in the construction of fluorescence sensors. In this paper, 4,4'-diaminobiphenyl (DABP) with an AIEE activity was used as a fluorescent substance, and a novel and simple unlabeled fluorescent aptasensor was constructed through binding and disassociation of DABP with the aptamer of prostate specific antigen (PSA-Apt). DABP and PSA-Apt could bind together through hydrogen bonding and hydrophobic effects, resulting in AIEE effect and enhanced the fluorescence of DABP. Then, PSA was added to the above solution. Given the considerably higher affinity between PSA-Apt and PSA than between PSA-Apt and DABP, the PSA-Apt dissociated from DABP and bound to PSA, which freed up DABP in the solution. The AIEE effect disappeared, and the fluorescence intensity of DABP decreased. The decrease in the fluorescent intensity was directly proportional to the PSA level, which enabled the qualitative and quantitative determination of PSA. This method has a high sensitivity for the detection of PSA, and within the concentration range of 30-5000 pg mL^-1, an excellent linear relationship existed between the concentration of PSA and the decrease in the fluorescence intensity of DABP, with a limit of detection as low as 10 pg mL^-1. In addition, the sensor has a high specificity for PSA and can be used for the determination of PSA in human serum.