Stable and sensitive sensor for alkaline phosphatase based on target-triggered wavelength tuning of fluorescent copper nanoclusters.

Generally, the volatility and vulnerability of intensity signal largely reduced the reproducibility and stability of fluorescent nanosensor. Herein, we proposed a novel and stable fluorescent sensor by employing the wavelength shift of copper nanoclusters (CuNCs) as signal readout. The thymine-templated CuNCs were prepared by facile and rapid one-pot reduction method. Interestingly and importantly, it was found that the fluorescence wavelength of CuNCs could be precisely tuned by manganese ion (Mn). Through systematic investigation, it was further proved that the wavelength readout of CuNCs is significantly more stable than intensity readout. Since alkaline phosphatase (ALP) can catalyze the hydrolysis of phosphorylated ascorbic acid into ascorbic acid (AA) which can trigger the decomposition of MnO nanosheets (NS) into Mn, a stable sensor for sensitive ALP detection was constructed based on precise wavelength tuning of fluorescent CuNCs. The sensor exhibited good linear response to ALP over the range from 0.025 to 10 U/L with a detection limit of 0.008 U/L. Additionally, this sensor was also extended to assay two typical ALP inhibitors (NaVO and EDTA) with reasonable results. Last but not least, it was confirmed that the detection results of ALP in real serum samples with this sensor were highly consistent with the data from clinical test, which was mainly attributed to the improved stability and practicability of wavelength readout-based sensor.