A convenient and label-free fluorescence “turn off–on” nanosensor with high sensitivity and selectivity for acid phosphatase

• A novel convenient and label-free fluorescence “turn off–on” nanosensor for rapid detection of acid phosphatase was established.
• The simple and straightforward method was based on the aggregation-caused quenching and enzymolysis approach.
• Highly sensitivity and selectivity were obtained.
• Acid phosphatase in human serum sample was detected with satisfactory results.

In this study, we reported a convenient label-free fluorescence nanosensor for rapid detection of acid phosphatase on the basis of aggregation-caused quenching (ACQ) and enzymolysis approach. The selectivity nanosensor was based on the fluorescence “turn off–on” mode, which possessed high sensitivity features. The original strong fluorescence intensity of CuInS2 QDs was quenched by sodium hexametaphosphate (NaPO3)6. The high efficiency of the quenching was caused by the non-covalent binding of positively charged CuInS2 QDs to the negatively charged (NaPO3)6 through electrostatic interactions, aggregating to form a CuInS2 QDs/(NaPO3)6 complex. Adding acid phosphatase caused intense fluorescence of CuInS2 QDs/(NaPO3)6 to be recovered, and this was because of enzymolysis. (NaPO3)6 was hydrolyzed into small fragments and the high negative charge density decreased, which would weaken the strong electrostatic interactions. As a result, the quenched fluorescence “turned on”. Under the optimum conditions, there was a good linear relationship between I/I0 (I and I0 were the fluorescence intensity of CuInS2 QDs/(NaPO3)6 system in the presence and absence of acid phosphatase, respectively) and acid phosphatase concentration in the range of 75–1500 nU mL−1 with the detection limit of 9.02 nU mL−1. The proposed nanosensor had been utilized to detect and accurately quantify acid phosphatase in human serum samples with satisfactory results.

A convenient and label-free near-infrared fluorescence “turn off–on” nanosensor was developed for rapid detection of acid phosphatase based on aggregation-caused quenching and enzymolysis approach.Figure optionsDownload as PowerPoint slide