Compact Saloplastic Poly(Acrylic Acid)/Poly(Allylamine) Complexes: Kinetic Control Over Composition, Microstructure, and Mechanical Properties

Durable compact polyelectrolyte complexes (CoPECs) with controlled porosity and mechanical properties are prepared by ultracentrifugation. Because thestarting materials, poly(allylamine hydrochloride) (PAH) and poly(acrylic acidsodium salt) (PAA), are weak acids/bases, both composition and morphology are controlled by solution pH. In addition, the nonequilibrium nature of polyelectrolyte complexation can be exploited to provide a range of compositions and porosities under the infl uence of polyelectrolyte addition order and speed, and concentration. Confocal microscopy shows these “saloplastic” materials to be highly porous, where pore formation is attributed to a combination of deswelling of the polyelectrolyte matrix and expansion of small inhomogenities by osmotic pressure. The porosity (15–70%) and the pore size ( < 5 μ m to > 70 μ m) of these materials can be tuned by adjusting the PAA to PAH ratio, the salt concentration, and the pH. The modulus of these CoPECs depends on the ratio of the two polyelectrolytes, with stoichiometric complexes being the stiffest due to optimized charge pairing, which correlates with maximized crosslinking density. Mechanical properties, pore sizes, and pore density of these materials make them well suited to three dimensional supports for tissue engineering applications

Propriétés mécaniques de films multicouches de polyélectrolytes

Les films multicouches de polyélectrolytes sont constitués d'une superposition alternée de polyélectrolytes de charges opposées, qui s'assemblent par interaction électrostatique pour former des films dont l'épaisseur peut varier de quelques longueurs moléculaires à plusieurs dizaines de µm. Ces matériaux suscitent actuellement un intérêt croissant en raison de leurs utilisations potentielles dans la réalisation de photodiodes, de membranes sélectives ou de revêtements biocompatibles. Nous présentons une étude du comportement du module de cisaillement complexe réalisée sur des films multicouches réticulés et non réticulés, constitués d'acide hyaluronique et de poly-L-lysine. Les mesures ont été effectuées avec le dispositif de piézorhéologie, que nous avons récemment développé, et qui permet de caractériser la réponse mécanique d'un échantillon mince (~10µm) sur une gamme de fréquence étendue et pour de très faibles déformations appliquées. Cette communication illustre l'intérêt de la piézorhéologie pour l'étude des propriétés mécaniques des systèmes lamellaires d'intérêt biologique

Catalytic Saloplastics: Alkaline Phosphatase Immobilized and Stabilized in Compacted Polyelectrolyte Complexes

Novel biochemically active compact polyelectrolyte complexes (CoPECs) are obtained through a simple coprecipitation and compaction procedure. As shown for the system composed of poly(acrylic acid) (PAA) and poly(allylamine) (PAH) as polyelectrolytes and alkaline phosphatase (ALP) as enzyme, the enzyme can be firmly immobilized into these materials. The ALP not only remains active in these materials, but the matrix also enhances the specific activity of the enzyme while protecting it from deactivation at higher temperature. The presence of the matrix allows fine control and substantial enhancement of reaction rates by varying the salt concentration of the contacting solution or temperature. The excellent reusability, together with the ease of co-immobilizing other useful components, such as magnetic particles, allowing facile handling of the CoPECs, makes these materials interesting candidates for variable scaffolds for the immobilization of enzymes for small- and large-scale enzyme-catalyzed processes

High-resolution electron microscopy of young apatite crystals in human fetal enamel

International audienc

Synthesis, characterization and high temperature analysis of Al-containing hydroxyapatites

International audienc

Heterogeneous nucleation of calcium phosphate salts at a solid/liquid interface examined by scanning angle reflectometry

International audienc

High resolution electron microscopy study of crystal growth mechanisms in chicken bone composites

International audienc

High Resolution Electron Microscopy: Structure and Growth Mechanisms of Human Dentin Crystals

International audienc