UiO-66-NH2: An easily attainable and label-free turn-on probe for facile fluorescence sensing of alkaline phosphatase

Alkaline phosphatase (ALP) is now a well acknowledged indicator for diverse clinical diseases correlated with its abnormal expression. Compared to the assays by traditional and lately emerging methods, the fluorescent (FL) sensing, especially in the turn-on mode, has become more favored due to its simplicity, low cost, and high sensitivity and precision. However, the feasible FL probes are still limited and suffering from poor biological compatibility, complex preparation, additional modification or function-alization. Herein, we found that one common metal-organic framework, UiO-66-NH2 at nanoscale, could act as a new and label-free FL probe for facile sensing of ALP in the turn-on mode, based on the simple aid by phenyl phosphate which could be hydrolyzed by ALP, with the product of phosphate ion enhancing the FL emission of UiO-66-NH2 via simple adsorption. Unlike many other FL probes in the turn-on mode, it was unnecessary to quench the FL of the probes in advance, greatly simplifying the sensor design. Moreover, by use of a new method based on dielectric barrier discharge (DBD), the UiO-66-NH2 could be prepared in 10 min, much shorter than that (usually hours) for preparing most other FL probes for ALP assay. The limit of detection was 0.4 U L-1, superior or at least rivalrous to the previously reported ones, and the ALP assay was also accomplished for real serum samples, with the analytical results highly consistent with those obtained by the clinical procedures, revealing its high practical utility.