Monitoring of nanoclay-protein adsorption isotherms via fluorescence techniques


The investigation of nanoparticles and their interaction with bio-macromolecules have become an important issue; the widely discussed protein corona around nanoparticles and their biological fate in general have drawn particular attention. Here, we focus on nanoclay dispersions and the use of solvatochromic fluorescent dyes (Dansyl and Coumarin 153) for monitoring the interaction with two model proteins, bovine serum albumin and beta-lactoglobulin. On one hand, these dyes are poorly emissive in water, but experience a boost in their fluorescence when adsorbed into the hydrophobic domains of proteins. On the other hand, (nano)clays and clay minerals have previously been investigated in terms of their individual protein adsorption isotherms and their usefulness for the solubilization of water-insoluble dyes into an aqueous environment. In the following, we have combined all three individual parts (nanoclay, fluorophore and protein) in dispersions in a wide range of concentration ratios to systematically study the various adsorption processes via fluorescence techniques. In order to clarify the extent of dye diffusion and adsorption-desorption equilibria in the investigations, nanoclay hybrids with an adsorbed dye (Coumarin 153) and a covalently conjugated dye (Dansyl) were compared. The results suggest that the fluorescence progression of protein titration curves correlate with the amount of protein adsorbed, matching their reported adsorption isotherms on hectorite clays. Furthermore, experimental data on the protein monolayer formation around the nanoclays could be extracted due to only minor alterations of the dispersions' optical quality and transparency. In this manner, a fluorescence-based monitor for the formation of the globular protein layer around the nanoclay was realized. (C) 2017 Elsevier B.V. All rights reserved.




Biophysics; Chemistry; Materials Science


Felbeck, T; Moss, S; Botas, AMP; Lezhnina, MM; Ferreira, RAS; Carlos, LD; Kynast, UH

nossos autores


This work was in part financially supported by the German Federal Ministry for Economic Affairs and Energy (BMWi, ZIM grant 16KN 013521). T. F. would like to express his gratitude to Dr. Ute Resch-Genger, Federal Institute for Materials Research and Testing (BAM Division 1.10-Biophotonics) for her sensible advice on solvatochromic dyes to understand the delicate guest-nanoclay interactions, and for support in quantitative measurements. This work was further developed within the scope of the project CICECO - Aveiro Institute of Materials, POCI-01-0145-FEDER-007679 (FCT Ref. UID/CTM/50011/2013), financed by national funds through the FCT/MEC and co-financed by FEDER under the PT2020 Partnership.

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