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Open AccessArticle

Kinetic Analysis of the Uptake and Release of Fluorescein by Metal-Organic Framework Nanoparticles

Faculty of Physics and Center for NanoScience (CeNS), LMU Munich, Geschwister-Scholl-Platz 1, 80539 Munich, Germany
Department of Chemistry and Center for NanoScience (CeNS), LMU Munich, Butenandtstraße 11 (E), 81377 Munich, Germany
Authors to whom correspondence should be addressed.
Academic Editor: Claudio Pettinari
Materials 2017, 10(2), 216;
Received: 29 November 2016 / Revised: 3 February 2017 / Accepted: 9 February 2017 / Published: 22 February 2017
(This article belongs to the Special Issue Metal Organic Framework Materials)
Metal-organic framework nanoparticles (MOF NPs) are promising guest-host materials with applications in separation, storage, catalysis, and drug delivery. However, on- and off-loading of guest molecules by porous MOF nanostructures are still poorly understood. Here we study uptake and release of fluorescein by two representative MOF NPs, MIL-100(Fe) and MIL-101(Cr). Suspensions of these MOF NPs exhibit well-defined size distributions and crystallinity, as verified by electron microscopy, dynamic light scattering, and X-ray diffraction. Using absorbance spectroscopy the equilibrium dissociation constants and maximum numbers of adsorbed fluorescein molecules per NP were determined. Time-resolved fluorescence studies reveal that rates of release and loading are pH dependent. The kinetics observed are compared to theoretical estimates that account for bulk diffusion into NPs, and retarded internal diffusion and adsorption rates. Our study shows that, rather than being simple volumetric carriers, MOF-NPs are dominated by internal surface properties. The findings will help to optimize payload levels and develop release strategies that exploit varying pH for drug delivery. View Full-Text
Keywords: metal organic framework; nanoparticle; loading and release metal organic framework; nanoparticle; loading and release
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MDPI and ACS Style

Preiß, T.; Zimpel, A.; Wuttke, S.; Rädler, J.O. Kinetic Analysis of the Uptake and Release of Fluorescein by Metal-Organic Framework Nanoparticles. Materials 2017, 10, 216.

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