Size-Controlled Nanoparticle Clusters of Narrow Size-Polydispersity Formed Using Multiple Particle Types Through Competitive Stabilizer Desorption to a Liquid-Liquid Interface.

A novel colloidal approach is presented for preparing fully dispersed nanoparticle (NP) assemblies (clusters) of narrow size-polydispersity over a wide range of sizes through irreversible depletion of stabilizing ligands onto a liquid-liquid interface. Unusually, the relative monodispersity of the assemblies continuously improves throughout the process. A detailed kinetics study into the assembly of iron oxide NP clusters shows that the assembly rate decreases with NP concentration, pinpointing the role of the interface in size focusing.

The dynamics and pH-dependence of Ag43 adhesins' self-association probed by atomic force spectroscopy.

Self-associating auto-transporter (SAAT) adhesins are two-domain cell surface proteins involved in bacteria auto-aggregation and biofilm formation. Antigen 43 (Ag43) is a SAAT adhesin commonly found in Escherichia coli whose variant Ag43a has been shown to promote persistence of uropathogenic E. coli within the bladder.

Electrodynamics of soft multilayered particles dispersions: dielectric permittivity and dynamic mobility.

We report a theory for the evaluation of the electrodynamics of dispersions of spherical soft multilayered (bio)particles, with microorganisms and polyelectrolyte multilayers-coated particles as illustrative paradigms. These particles generally consist of a hard (ion- and water-impermeable) core component supporting a succession of step-function or diffuse-like concentric soft (permeable) polymeric layers defined by distinct electrostatic, hydrodynamic and structural properties. The formalism is based on a rigorous numerical resolution of the coupled Navier-Stokes-Brinkman equation, continuity equations for the flow and for the ionic species present in solution, and the non-linear Poisson equation corrected for the multilayered nature of the soft interphase.

Thermo-regulated adhesion of the Streptococcus thermophilus Δrgg0182 strain.

The physicochemical determinants governing the temperature-dependent adhesion of Streptococcus thermophilus to abiotic surfaces are identified under physiological condition for cells either lacking or not the Rgg0182 transcriptional regulator involved in their thermal adaptation. For that purpose, the wild type LMG18311 strain and Δrgg0182 mutant were imaged using highly resolved atomic force microscopy (AFM) at various cell growth temperatures (42 to 55 °C). The corresponding hydrophobic/hydrophilic balance of the cells was quantitatively addressed via the measurement by chemical force microcopy of their adhesion to a reference hydrophobic surface.

Metal speciation in a complexing soft film layer: a theoretical dielectric relaxation study of coupled chemodynamic and electrodynamic interfacial processes.

We report a comprehensive formalism for the dynamics of metal speciation across an interphase formed between a complexing soft film layer and an electrolyte solution containing indifferent ions and metal ions that form complexes with charged molecular ligands distributed throughout the film. The analysis integrates the intricate interplay between metal complexation kinetics and diffusive metal transfer from/toward the ligand film, together with the kinetics of metal electrostatic partitioning across the film/solution interphase. This partitioning is determined by the settling dynamics of the interfacial electric double layer (EDL), as governed by time-dependent conduction-diffusion transports of both indifferent and reactive metal ions.

Bacterial surface appendages strongly impact nanomechanical and electrokinetic properties of Escherichia coli cells subjected to osmotic stress.

The physicochemical properties and dynamics of bacterial envelope, play a major role in bacterial activity. In this study, the morphological, nanomechanical and electrohydrodynamic properties of Escherichia coli K-12 mutant cells were thoroughly investigated as a function of bulk medium ionic strength using atomic force microscopy (AFM) and electrokinetics (electrophoresis). Bacteria were differing according to genetic alterations controlling the production of different surface appendages (short and rigid Ag43 adhesins, longer and more flexible type 1 fimbriae and F pilus).

Electrostatic interactions between diffuse soft multi-layered (bio)particles: beyond Debye-Hückel approximation and Deryagin formulation.

We report a steady-state theory for the evaluation of electrostatic interactions between identical or dissimilar spherical soft multi-layered (bio)particles, e.g. microgels or microorganisms.