Bimodal Quantitative Monitoring for Enzymatic Activity with Simultaneous Signal Increases in ¹⁹F NMR and Fluorescence Using Silica Nanoparticle-Based Molecular Probes

Abstract

We describe the bimodal quantitative assay for enzymatic activity in (19)F NMR spectroscopy and fluorescence spectroscopy using a nanoparticle-based molecular probe. Perfluorinated dendrimers were tethered on silica nanoparticles with a phosphate-caged fluorescein as a linker. Before enzymatic reaction, the molecular rotation of the perfluorinated dendrimers should be highly restricted, and the (19)F NMR signals from the perfluorinated dendrimers were too broad to be detected relative to the noise level. Fluorescence signals of fluorescein were suppressed by the presence of the diphosphate groups. Following the enzymatic reaction with an alkaline phosphatase, perfluorinated dendrimers and fluorescein were released, and the NMR signals of perfluorinated dendrimers and strong fluorescence from fluorescein were correspondingly observed. The enzymatic activity and reaction rates of the hydrolysis of alkaline phosphatase were detected from the increases of fluorescence and (19)F NMR signals. Finally, the feasibility of the probe in the presence of miscellaneous molecules under biomimetic conditions was demonstrated by determining of the enzymatic activity in cell lysate. Quantitative analysis using both (19)F NMR spectroscopy and fluorescence spectroscopy can be accomplished.