Protein Adsorption and Reorganization on Nanoparticles Probed by the Coffee- Ring Effect: Application to Single Point Mutation Detection

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Protein Adsorption and Reorganization on Nanoparticles Probed by the Coffee-Ring Effect: Application to Single Point Mutation Detection, J. Am. Chem. Soc 2016, 138, 11623–11632

 

The coffee-ring effect (CRE) describes the deposition of particles at the edge of a drop during drying of a colloidal suspension, as one can observe in the black ring of a coffee stain. The physics of the CRE was first explained by Deegan et al.  When a drop is pinned on a substrate, the higher evaporation rate at the contact line induces a strong capillary flow that thoroughly transports particles from the bulk to the contact line where they accumulate. The CRE is a phenomenon that can occur with any drying drop containing nonvolatile solutes, including not only inert particles but also biological entities such as bacteria, viruses and proteins. This ubiquitous character makes the occurrence of the CRE an obstacle in many types of applications ranging from inkjet printing  to DNA microarrays, protein microarrays and cell patterning.  Much eff ort has thus been devoted to control or suppress the CRE. Successful strategies have usually relied on aff ecting either one of the two key components at the origin of the CRE, i.e., the capillary flow toward the edge of the drop and the pinning of the contact line, or by tuning interactions between particles and interfaces. This implied the use of additives such as surfactants, polymers, sol−gel inducers and cosolvents, or the application of electric or optical stimulations. However, how proteins can aff ect the deposition behavior of particles in an evaporating drop remains largely unknown. Knowing that both synthetic polymers and surfactants can affect the CRE, one can raise the question whether adding biomolecules such as proteins to a particle suspension would change the pattern formation upon drop drying and, if so, what distinguishes proteins from ordinary polymers and surfactants.

 

Hence, using the CRE to probe these interactions can be exploited in diff erent ways. First, it can be exploited to distinguish between a native and a mutant form of a specific protein, especially when mutation leads to hydrophobic residue exposure, as presented in this paper with the robust discrimination between native and sickle cell human hemoglobin. Second this could be useful to investigate protein reorganization and charge modifi cation after adsorption on particles in the context of nanotoxicology and nanomedicine, for instance to screen in a rapid and low-resource way a large number of proteins and nanoparticles. These two new types of screening assays could reach high-throughput capabilities by benefiting from the development of automatic pattern recognition softwares. Overall, we have shown how the CRE translates various types of molecular interactions between particles and proteins into easily distinguishable macroscopic patterns, thus providing valuable insights for the development of current and future cost-effective diagnostic tools.

 

N'hésitez pas à consulter le communiqué de presse associé à cet article : Détecter une maladie génétique avec une "tache de café" !

 

Résumé: 

J. Am. Chem. Soc 2016, 138, 11623–11632

 

The coffee-ring effect denotes the accumulation of particles at the edge of an evaporating sessile drop pinned on a substrate. Because it can be detected by simple visual inspection, this ubiquitous phenomenon can be envisioned as a robust and cost-effective diagnostic tool. Toward this direction, here we systematically analyze the deposit morphology of drying drops containing polystyrene particles of different surface properties with various proteins (bovine serum albumin (BSA) and diff erent forms of hemoglobin). We show that deposit patterns reveal information on both the adsorption of proteins onto particles and their reorganization following adsorption. By combining pattern analysis with adsorption isotherm and zeta potential measurements, we show that the suppression of the coffee-ring effect and the formation of a disk-shaped pattern is primarily associated with particle neutralization by protein adsorption. However, our fi ndings also suggest that protein reorganization following adsorption can dramatically invert this tendency. Exposure of hydrophobic (respectively charged) residues can lead to disk (respectively ring) deposit morphologies independently of the global particle charge. Surface tension measurements and microscopic observations of the evaporating drops show that the determinant factor of the deposit morphology is the accumulation of particles at the liquid/gas interface during evaporation. This general behavior opens the possibility to probe protein adsorption and reorganization on particles by the analysis of the deposit patterns, the formation of a disk being the robust signature of particles rendered hydrophobic by protein adsorption. 

 

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Références: 

Protein Adsorption and Reorganization on Nanoparticles Probed by the Coffee-Ring Effect: Application to Single Point Mutation Detection

 

Devineau S, Anyfantakis M, Marichal L, Kiger L, Morel M, Rudiuk S, Baigl D.

 

J. Am. Chem. Soc 2016, 138, 11623–11632

 

doi: 10.1021/jacs.6b04833