A Turn-On Fluorescent Sensor for Selective and Sensitive Detection of Alkaline Phosphatase Activity with Gold Nanoclusters Based on Inner Filter Effect

Abstract

In this work, a novel approach for simple and sensitive determination of alkaline phosphatase (ALP) is developed on the basis of an inner filter effect of p-nitrophenylphosphate (PNPP) on the fluorescence of gold nanoclusters (AuNCs). AuNCs with a high quantum yield of 12% were synthesized by one-pot strategy and were directly applied as fluorescent substance. When AuNCs were mixed with PNPP, the fluorescence of the AuNCs was remarkably quenched or was decreased via the inner filter effect since the absorption spectrum of PNPP overlaps well with the excitation spectrum of the AuNCs. While in the presence of ALP, PNPP was catalytically hydrolyzed into p-nitrophenol, which has different absorption characteristics from those of PNPP, resulting in the recovery of the AuNCs fluorescence. Thus, a novel "turn-on" fluorescent sensor for detecting ALP was established with a detection limit as low as 0.002 U/L (signal-to-noise ratio of 3). The turn-on fluorescent sensor exhibits many merits such as high sensitivity, excellent selectivity, and high signal output because of the low background signals. In addition, the developed sensing method was successfully applied to investigate ALP inhibitors and ALP determination in serum samples. A good linear relationship was obtained in the range from 0.02 to 50 U/L, and satisfactory recoveries at four spiking levels of ALP ranged from 95% to 106% with precision below 5%. The very simple sensing approach proposed here should promote the development of fluorescence turn-on chemosensors for chemo/biodetection.

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Basophilic green fluorescent carbon nanoparticles derived from benzoxazine for the detection of Cr(vi) in a strongly alkaline environment

“…The inner lter effect (IFE) refers to the absorption of the excitation and/or emission of uorescent material by absorbers in the detection system, and it needs that the absorption band of the absorbers possesses a complementary overlap with the excitation and/or emission spectra of the uorescent material. [47][48][49][50][51] To conrm the mechanism of the selective response of G-CNPs towards Cr(VI), UV-vis absorption spectrum of Cr(VI) (actually CrO 4 2À ), the maximum uorescence excitation and emission spectra of the G-CNPs at pH ¼ 14 were measured. As shown in Fig.…”