Fluorometric and colorimetric dual-readout alkaline phosphatase activity assay based on enzymatically induced formation of colored Au@Ag nanoparticles and an inner filter effect

• DOI: 10.1007/s00604-019-3478-6
• Publication Date: 2019-05-11T15:01:58Z
• Authors: Chuanxia Chen; Guanglu Zhang; Pengjuan Ni; Yuanyuan Jiang; Yizhong Lu; Zhengliang Lu
• Keywords: Adult; Silver; Metal Nanoparticles; Ascorbic Acid; 02 engineering and technology; Alkaline Phosphatase; Spectrometry, Fluorescence; Limit of Detection; Quantum Dots; Humans; Colorimetry; Graphite; Gold; 0210 nano-technology; Oxidation-Reduction; Enzyme Assays

An ultrasensitive fluorometric and colorimetric dual-mode assay is described for the determination of the activity of alkaline phosphatase (ALP). ALP catalyzes the decomposition of 2-phospho-L-ascorbic acid, and the ascorbic acid thus generated reduces silver ions. In the presence of gold nanoparticles, gold-silver nanoparticles (Au@Ag NPs) are formed. This is accompanied by a color change form pink to deep yellow. The Au@Ag NPs reduce the fluorescence of blue fluorescent graphene quantum dots due to spectral overlap. The changes of absorbance (measured at 410 and 520 nm) and fluorescence (measured at excitation/emission wavelengths of 346/415 nm) correlate well with the ALP activity in the 0.01-6 mU·mL-1 (absorption) and 0.01-2 mU·mL-1 (fluorescence) ranges, and the detection limits are 9 and 5 μU·mL-1 individually. Graphical abstract Schematic presentation of colorimetric and fluorometric dual-readout assay for alkaline phosphatase (ALP) activity. It is based on enzymatically induced formation of gold-silver nanoparticles (Au@Ag NPs), and the fluorescence quenching of graphene quantum dots due to inner filter effect.