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Université de Fribourg

Characterizing nanoparticles in complex biological media and physiological fluids with depolarized dynamic light scattering

Balog, Sandor ; Rodriguez-Lorenzo, Laura ; Monnier, Christophe A. ; Obiols-Rabas, Marc ; Rothen-Rutishauser, Barbara ; Schurtenberger, Peter ; Petri-Fink, Alke

In: Nanoscale, 2015, p. -

Light scattering is one of the few techniques available to adequately characterize suspended nanoparticles (NPs) in real time and in situ. However, when it comes to NPs in multicomponent and optically complex aqueous matrices – such as biological media and physiological fluids – light scattering suffers from lack of selectivity, as distinguishing the relevant optical signals from the...

Université de Fribourg

Spinodal decomposition in a food colloid–biopolymer mixture: evidence for a linear regime

Bhat, Suresh ; Tuinier, Remco ; Schurtenberger, Peter

In: Journal of Physics: Condensed Matter, 2006, vol. 18, p. L339–L346

We investigate phase separation and structural evolution in a complex food colloid (casein micelles) and biopolymer (xanthan) mixture using small-angle light scattering. We demonstrate that phase separation is induced by a depletion mechanism, and that the resulting coexistence curve can be described by osmotic equilibrium theory for mixtures of colloids and polymer chains in a background...

Université de Fribourg

Modeling equilibrium clusters in lysozyme solutions

Cardinaux, Frédéric ; Stradner, Anna ; Schurtenberger, Peter ; Sciortino, F. ; Zaccarelli, E.

In: Europhysics Letters, 2007, vol. 77, no. 4, p. 48004

We present a combined experimental and numerical study of the equilibrium cluster formation in globular-protein solutions under no-added salt conditions. We show that a cluster phase emerges as a result of a competition between a long-range screened Coulomb repulsion and a short-range attraction. A simple effective potential, in which electrostatic repulsion is fixed by experimental conditions...

Université de Fribourg

Interplay between spinodal decomposition and glass formation in proteins exhibiting short-range attractions

Cardinaux, Frédéric ; Gibaud, Thomas ; Stradner, Anna ; Schurtenberger, Peter

In: Physical Review Letters, 2007, vol. 99, no. 11, p. 118301

We investigate the competition between spinodal decomposition and dynamical arrest using aqueous solutions of the globular protein lysozyme as a model system for colloids with short-range attractions. We show that quenches below a temperature Ta lead to gel formation as a result of a local arrest of the protein-dense phase during spinodal decomposition. The rheological...

Université de Fribourg

Cluster-Driven dynamical arrest in concentrated lysozyme solutions

Cardinaux, Frédéric ; Zaccarelli, Emanuela ; Stradner, Anna ; Bucciarelli, Saskia ; Farago, Bela ; Egelhaaf, Stefan U. ; Sciortino, Francesco ; Schurtenberger, Peter

In: The Journal of Physical Chemistry B, 2011, vol. 115, no. 22, p. 7227–7237

We present a detailed experimental and numerical study of the structural and dynamical properties of salt-free lysozyme solutions. In particular, by combining small-angle X-ray scattering (SAXS) data with neutron spin echo (NSE) and rheology experiments, we are able to identify that an arrest transition takes place at intermediate densities, driven by the slowing down of the cluster motion. Using...

Université de Fribourg

Jamming and overpacking fuzzy microgels: Deformation, interpenetration, and compression

Conley, Gaurasundar M. ; Aebischer, Philippe ; Nöjd, Sofi ; Schurtenberger, Peter ; Scheffold, Frank

In: Science Advances, 2017, vol. 3, no. 10, p. e1700969

Tuning the solubility of fuzzy polymer microgels by external triggers, such as temperature or pH, provides a unique mechanism for controlling the porosity and size of colloidal particles on the nanoscale. As a consequence, these smart microgel particles are being considered for applications ranging from viscosity modifiers and sensing to drug delivery and as models for the glass and the...

Université de Fribourg

Superresolution microscopy of the volume phase transition of pNIPAM microgels

Conley, Gaurasundar M. ; Nöjd, Sofi ; Braibanti, Marco ; Schurtenberger, Peter ; Scheffold, Frank

In: Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2016, vol. 499, p. 18–23

Hierarchical polymer structures such as pNIPAM microgels have been extensively studied for their ability to undergo structural and physical transformations that can be controlled by external stimuli such as temperature, pH or solvent composition. However, a direct three-dimensional visualization of individual particles in-situ has so far been hindered by insufficient resolution, with optical...

Université de Fribourg

Thermoresponsive hybrid microgel particles with intrinsic optical and magnetic anisotropy

Dagallier, Camille ; Dietsch, Hervé ; Schurtenberger, Peter ; Scheffold, Frank

In: Soft Matter, 2010, vol. 6, p. 2174-2177

We describe the synthesis of thermoresponsive, magnetic, optically anisotropic and orientable colloidal particles based on poly(N-isopropylacrylamide) hybrid microgels (PNIPAMs) with an embedded ellipsoidal hematite (α-Fe₂O₃) core. Our ability to orient the particles with a magnetic field is demonstrated by small angle X-ray scattering and by optical polarization microscopy.

Université de Fribourg

Rheology and structural arrest of casein suspensions

Dahbi, Louisa ; Alexander, M. ; Trappe, Véronique ; Dhont, J.K.G. ; Schurtenberger, Peter

In: Journal of Colloid and Interface Science, 2010, vol. 342, no. 2, p. 564-570

The rheology of milk powder suspensions is investigated up to very high concentrations, where structural arrest occurs. The main component of the milk powder investigated is casein, so that the suspensions can be regarded as casein suspensions. Four concentration regimes are identified. For effective casein volume fractions less than 0.54 the concentration dependence of the zero-shear viscosity...

Université de Fribourg

Colloidal characterization and thermodynamic stability of binary eye lens protein mixtures

Dorsaz, N. ; Thurston, G. M. ; Stradner, Anna ; Schurtenberger, Peter ; Foffi, G.

In: The Journal of Physical Chemistry B, 2009, vol. 113, no. 6, p. 1693–1709

We present a study of binary mixtures of eye lens crystallin proteins. A coarse-grained model of aqueous α- and γ-crystallin mixtures based on molecular dynamics simulations and SANS experiments is proposed. Thermodynamic perturbation theory is implemented to obtain the stability boundaries, or spinodal surface, of the binary mixture in the full parameter space. The stability of these...