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 (Mn2+). 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 MnO2 nanosheets (NS) into Mn2+, 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 (Na3VO4 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. A stable sensor for sensitive ALP detection that combines the strategy of target-triggered Mn2+ generation from MnO2 NS and the finding of Mn2+-mediated wavelength tuning of fluorescent CuNCs. [Display omitted] •A strategy for controlled tuning fluorescence wavelength of copper nanoclusters was put forward.•The stability of wavelength readout of copper nanoclusters is significantly higher than that of intensity signal.•A wavelength readout-based fluorescent sensor was constructed for alkaline phosphatase detection.•The sensor exhibits high sensitivity and selectivity, as well as desirable practicability.