Search

Mineralized biological tissues rich in type I collagen (e.g., bone and dentin) exhibit complex anisotropic suprafibrillar organizations in which the organic and inorganic moieties are intimately coassembled over several length scales. Above a critical size, a defect in such tissue cannot be self-repaired. Biomimetic materials with a composition and microstructure similar to that of bone have been shown to favorably influence bone regeneration. This highlights the value of developing a similar formulation in an injectable form to enable minimally invasive techniques. Here, we report on the fabrication and application potential of an injectable collagen/CHA (carbonated hydroxyapatite) cell-free hydrogel. The organic part consists of spray-dried nondenatured and dense collagen microparticles, while the inorganic part consists of biomimetic apatite mineral. By mixing both powders at desired tissue-like ratios with an aqueous solvent in one step, spontaneous co-self-assembly occurs, leading to the formation of a mineralized matrix with suprafibrillar tissue-like features thanks to the induced liquid crystalline properties of collagen on one hand and apatite on the other hand. When injected into soft tissue, the mineralized collagen hydrogel free of chemical cross-linking agents exhibits suitable cohesion and is biocompatible. Preliminary in vitro tests in a tooth cavity model show its integration onto dentin with a biomimetic interface. Based on the results, this versatile injectable mineralized collagen hydrogel shows promising potential as a biomaterial for bone tissue repair and mineralized tissue-like ink for bioprinting applications.

Metallogels built in a bottom-up approach by metal coordination and supramolecular interactions have important potential for the elaboration of smart materials. In this context, we present here the formation of supramolecular coordination polymers driven by the complexation of cobalt(II) or zinc(II) ions with polyoxometalate-based hybrids displaying two terpyridine ligands in a linear arrangement. Thanks to the electrostatic interactions between the polyoxometalate cores and metal nodes, the polymer chains self-assemble into fibers that physically cross-link to form gels above a critical concentration. Using spectroscopy, microscopy, X-ray scattering, and rheometry, complemented by molecular dynamics simulations, we investigated the supramolecular organization of the chains in the fibers and the resulting processes leading to gelation. Compared to previously reported systems, these gels have improved rheological features and appealing properties, such as birefringence, luminescence, and spin crossover, paving the way for their use as building blocks for multifunctional smart materials., Competing Interests: The authors declare no competing financial interest., (© 2024 The Authors. Published by American Chemical Society.)

Abstract: Skin contamination by α-emitting actinides such as plutonium and americium is a risk for workers during nuclear fuel production and reactor decommissioning. Decontamination of skin is an important medical countermeasure to limit potential internal contamination, particularly in the case of injured skin. Current recommendations include undressing of the victim followed by skin washing using soap or chelating agents, such as diethylene triamine pentaacetic acid (DTPA). The goal of the present work is to assess the efficacy of a novel Ca-DTPA loaded gel to decontaminate injured skin exposed to plutonium or americium as compared to recommended treatments. For decontaminant testing on injured skin, whole body skin was obtained from euthanized rats and lesions created using a metallic brush. Delimited test areas were contaminated with plutonium or americium solutions of known properties. Various protocols were tested including time before contamination, duration of gel application, washing steps, as well as the concomitant addition or not of dressings. Activity was measured in each decontamination product and in skin. Data indicate that healthy skin was easier to decontaminate than damaged skin. On injured skin, we demonstrated an increased decontamination efficacy of the Ca-DTPA gel formulation as compared to the solution. Importantly, gel application alone was effective, and further gel applications could be used for residual activity., (Copyright © 2024 The Author(s). Published by Wolters Kluwer Health, Inc. on behalf of the Health Physics Society.)

The supramolecular and mesoscopic architectures of lead-saponified linseed oil, used by painters since the Renaissance, have been characterised and linked to their rheological properties. The multi-scale organization of saponified oils has been demonstrated by SAXS (Small Angle X-ray Scattering), FF-TEM (Freeze-Fracture Transmission Electron Microscopy) and DIC (Differential Interference Contrast): some of the lead soaps (formed when the oil is heated in the presence of PbO) are organized into microscopic lamellar domains, distributed in a continuous matrix made up of unorganized species (partially saponified triglycerides, glycerol, remaining soaps, etc. ). The concentration of lead soaps in the oil controls the average size and interaction between the lamellar domains. Linseed oil + PbO 17 mol% is viscous and consists of aggregates of lamellar domains isolated within the continuous unorganized matrix. In contrast, in linseed oil + PbO 50 mol%, the domains are homogeneously dispersed and form what can be described as a three-dimensional network, giving the system viscoelastic properties.

Organogels are used in a wide range of applications for which the development of new bio-based organogelators is highly desirable. While furan-2,5-dicarboxylic acid (FDCA) is a promising molecule for the synthesis of bio-based polyesters, it has never been used in the context of organogels. This study explores the possibility to design FDCA-based organogelators that self-assemble into fibrillar networks stabilized by hydrogen bonding. Gelation tests show the versatility of this gelator family with a wide variety of gelled liquids, especially apolar liquids. The structure of the gels was investigated by FTIR and CD spectroscopies, crystallography, powder X-ray diffraction and rheology.

From the 15 th century onwards, painters began to treat their oils with lead compounds before grinding them with pigments. Such a treatment induces the partial hydrolysis of the oil triglycerides and the formation of lead soaps, which significantly modify the rheological properties of the oil paint. Organization at the supramolecular scale is thus expected to explain these macroscopic changes. Synchrotron Rheo-SAXS (Small Angle X-ray Scattering) measurements were carried out on lead-treated oils, with different lead contents. We can now propose a full picture of the relationship between structure and rheological properties of historical saponified oils. At rest, lead soaps in oil are organized as lamellar phases with a characteristic period of 50 Å. Under shear, the loss of viscoelastic properties can be linked to the modification of this organization. Continuous shear resulted in a preferential and reversible orientation of the lamellar domains which increased with the concentration of lead soaps. The parallel orientation predominates over the entire shear range (0-1000 s -1 ). Conversely, oscillatory shear coiled the lamellae into cylinders that oriented themselves vertically in the rheometer cell. This is the first report of such a vertical cylindrical structure obtained under shear from lamellae., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier Inc. All rights reserved.)

Egg-tempera painting is a pictorial technique widely used in the Middle Ages, although poorly studied in its physico-chemical aspects until now. Here we show how NMR relaxometry and rheology can be combined to probe egg-tempera paints and shed new light on their structure and behavior. Based on recipes of the 15th century, model formulations with egg yolk and green earth have been reproduced to characterize the physicochemical properties of this paint at the mesoscopic and macroscopic scales. The rheological measurements highlight a synergetic effect between green earth and egg yolk, induced by the interactions between them and the structural organisation of the system. 1 H NMR relaxometry emphasizes the presence and the structure of a network formed by the yolk and the pigment., (© 2021 Wiley-VCH GmbH.)

We investigate the organisation of clay nanoplatelets within a hydrogel based on modified ionenes, cationic polyelectrolytes forming physically crosslinked hydrogels induced by hydrogen bonding and π-π stacking. Combination of small angle X-ray and neutron scattering (SAXS, SANS) reveals the structure of the polyelectrolyte network as well as the organisation of the clay additives. The clay-free hydrogel network features a characteristic mesh-size between 20 and 30 nm, depending on the polyelectrolyte concentration. Clay nanoplatelets inside the hydrogel organise in a regular face-to-face stacking manner, with a large repeat distance, following rather closely the hydrogel mesh-size. The presence of the nanoplatelets does not modify the hydrogel mesh size. Further, the clay-compensating counterions (Na + , Ca 2+ or La 3+ ) and the clay type (montmorillonite, beidellite) both have a significant influence on nanoplatelet organisation. The degree of nanoplatelet ordering in the hydrogel is very sensitive to the negative charge location on the clay platelet (different for each clay type). Increased nanoplatelet ordering leads to an improvement of the elastic properties of the hydrogel. On the contrary, the presence of dense clay aggregates (tactoids), induced by multi-valent clay counterions, destroys the hydrogel network as seen by the reduction of the elastic modulus of the hydrogel., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2021 Elsevier Inc. All rights reserved.)

A novel bioinspired underwater adhesive based on the injectable aqueous solution of a graft copolymer with a thermoresponsive backbone is reported, which turns into a sticky hydrogel just below body temperature. With this topology, the collapse of the backbones upon the thermal transition leads to the formation of a percolating network of strong hydrophobic domains. Similar to pressure-sensitive adhesives (PSAs), the hydrogel goes through fibrillation and extensive energy dissipation in large deformations, giving it an edge over conventional chemical hydrogels, which are typically elastic and inherently nonsticky. This capability comes from the hydrophobic nanoscaffold, which resists large deformations to minimize its contact with water. Since hydrophobic interactions are not weakened in water, the behavior of the hydrogel is maintained in aqueous medium. Chemistry-insensitive adhesion of this hydrogel offers a major advantage over current injectable adhesives, which rely on in situ chemical crosslinking reactions with tissues., (© 2020 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

A bio-based glycolipid bolaamphiphile (glyco-bolaamphiphile) has recently been produced (Van Renterghem et al., Biotechnol. Bioeng., 2018, 115, 1195-1206) on a gram scale by using the genetically-engineered S. bombicola strain Δat Δsble Δfao1. The glyco-bolaamphiphile bears two symmetrical sophorose headgroups at the extremities of a C16:0 (ω-1 hydroxylated palmitic alcohol) spacer. Its atypical structure has been obtained by redesigning the S. bombicola strain Δat Δsble, producing non-symmetrical glyco-bolaamphiphile, with an additional knock out (Δfao1) and feeding this new strain with fatty alcohols. The molecular structure of the glyco-bolaamphiphile is obtained by feeding the new strain a saturated C16 substrate (palmitic alcohol), which enables the biosynthesis of bolaform glycolipids. In this work, we show that the bio-based glyco-bolaamphiphile readily forms a hydrogel in water at room temperature, and that the hydrogel formation depends on the formation of self-assembled fibers. Above 28 °C, the molecules undergo a gel-to-sol transition, which is due to a fiber-to-micelle phase change. We provide a quantitative description of the Self-Assembled Fibrillar Network (SAFiN) hydrogel formed by the glyco-bolaampiphile. We identify the sol-gel transition temperature, the gelling time, and the minimal gel concentration; additionally, we explore the fibrillation mechanism as a function of time and temperature and determine the activation energy of the micelle-to-fiber phase transition. These parameters allow control of the elastic properties of the glyco-bolaamphiphile hydrogel: at 3 wt% and 25 °C, the elastic modulus G' is above the kPa range, while at 5 °C, G' can be tuned between 100 Pa and 20 kPa, by controlling the undercooling protocol.

We study the flow of suspensions of non-Brownian particles dispersed into a Newtonian solvent. Combining capillary rheometry and conventional rheometry, we evidence a succession of two shear thinning regimes separated by a shear thickening one. Through X-ray radiography measurements, we show that during each of those regimes, the flow remains homogeneous and does not involve particle migration. Using a quartz-tuning fork based atomic force microscope, we measure the repulsive force profile and the microscopic friction coefficient μ between two particles immersed into the solvent, as a function of normal load. Coupling measurements from those three techniques, we propose that (1) the first shear-thinning regime at low shear rates occurs for a lubricated rheology and can be interpreted as a decrease of the effective volume fraction under increasing particle pressures, due to short-ranged repulsive forces and (2) the second shear thinning regime after the shear-thickening transition occurs for a frictional rheology and can be interpreted as stemming from a decrease of the microscopic friction coefficient at large normal load.

Recently, alginates (ALG) characterized by high mannuronic content (M blocks) have been shown to undergo a reversible sol/gel transition during cooling in the presence of potassium salts. Cold gelling takes place at low temperatures, just below 0 °C for a KCl concentration of 0.3 mol/kg, but the aggregation process can be easily shifted to higher temperatures by increasing the salt concentration. In the present paper, we take advantage of this peculiar behavior to design a copolymer with schizophrenic gelling properties. For this purpose, side chains of poly(N-isopropylacrylamide) (PNIPAM), characterized by a Lower Critical Solution Temperature (LCST) in water, were grafted on the alginate backbone. Working in semidilute solutions, we show by coupling DSC and viscoelastic measurements that ALG-g-PNIPAM solutions are able to form gels either by cooling or heating depending on the ionic environment. As the aggregation process of ALG and PNIPAM depends mainly and respectively on the nature of the cations and anions, the choice of the salt is then critical to control the self-assembly behavior and the gel properties. Moreover, as the gelation process of alginates driven by the aggregation of mannuronic sequences is characterized by a large hysteresis of 20-30 °C between gelling and melting, both ALG and ALG-g-PNIPAM polymers offer a large versatility not only in terms of salt (nature and concentration) but also in preparation history as different states (sol or gel) can be obtained at room temperature.

Eudragit® RL (EuRL) matrices have been proposed to release a drug to the skin. However, no information is available on both viscoelastic and adhesive properties of such compositions. This work focuses on the evaluation of both rheological and texture properties of EuRL differently plasticized with tributyl citrate (TBC) or triacetin (TRI) in order to design a pressure sensitive adhesive suitable for transdermal patch preparation. The patch adhesive properties (i.e. tack, peel adhesion and shear adhesion) as well as its in vitro biopharmaceutical performances were determined after loading ibuprofen, ketoprofen or flurbiprofen. The addition of 40-60% w/w TBC or 40-50% w/w TRI to EuRL permitted to obtain matrices with the desired adhesive properties. Moreover, the increase of plasticizer content and loading of the drug reduced the relaxation time (τ R ). Consequently, the shear adhesion values decreased and the in vitro drug release constants (k) increased. Indeed, the k values from patches containing TBC were lower than the corresponding with TRI because of the lower fluidity of such matrices. In conclusion, the 60/40 EuRL/TBC binary blend is suitable for the design of transdermal patches since the in vitro permeability of the three selected drugs appeared comparable to those described in literature for marketed products., (Copyright © 2017 Elsevier B.V. All rights reserved.)

British 19th century painters such as J. M. W. Turner, commonly modified the properties of their paint by using gels called "gumtions". These gels allowed them to easily tune the paint handling and drying properties. The fascinating properties of these "gumtions" were obtained by adding lead acetate to a ternary system based on mastic resin, linseed oil and turpentine. Herein, we report and investigate in depth the rheological properties of these gels as well as their structure at a molecular and supra-molecular scale., (© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

A new approach for the elaboration of low molecular weight pressure-sensitive adhesives based on supramolecular chemistry is explored. The synthesis of model systems coupled with probe-tack tests and rheological experiments highlights the influence of the transient network formed by supramolecular bonds on the adhesion energy. The first step of our approach consists of synthesizing poly(butyl acrylate-co-glycidyl methacrylate) copolymers from a difunctional initiator able to self-associate by four hydrogen bonds between urea groups. Linear copolymers with a low dispersity (M n = 10 kg/mol, Ip < 1.4) have been synthesized via atom transfer radical polymerization. Films of the copolymers were then partially cross-linked through reaction of the epoxy functions with a diamine. The systematic variation of the average ratio of glycidyl methacrylate and diamine per copolymer shed light on the respective role played by the supramolecular interactions (between bis-urea groups and with the side chains) and by the chain extension and branching induced by the diamine/epoxy reaction. In this strategy, the adhesive performance can be optimized by modifying the strength of "stickers" (via the structure of the supramolecular initiator, for instance) and the polymer network (e.g., via the length and level of branching of the copolymer chains) in order to approach commercial PSA-like properties (high debonding energy and clean removal).

Low molecular weight gelators are versatile and responsive gel-forming systems. However, it is still a challenge to develop a new organogelator for a precise application, i.e., to gel a predetermined liquid. We propose a simple concept of a two-component gelling system that can be rationally adapted to gel liquids ranging in polarity from silicone oil to acetonitrile.

New thermo associating polymers were designed and synthesized by grafting amino terminated poly(ethylene oxide-co-propylene oxide) (PEPO) onto carboxymethyl guar (CMG) and carboxymethyl tamarind (CMT). The grafting was performed by coupling reaction between NH2 groups of PEPO and COOH groups of CMG and CMT using water-soluble EDC/NHS as coupling agents. The grafting efficiency and the temperature of thermo-association, T(assoc) in the copolymer were studied by NMR spectroscopy. The graft copolymers, CMG-g-PEPO and CMT-g-PEPO exhibited interesting thermo-associating behavior which was evidenced by the detailed rheological and fluorescence measurements. The visco-elastic properties (storage modulus, G'; loss modulus, G") of the copolymer solutions were investigated using oscillatory shear experiments. The influence of salt and surfactant on the T(assoc) was also studied by rheology, where the phenomenon of "Salting out" and "Salting in" was observed for salt and surfactant, respectively, which can give an easy access to tunable properties of these copolymers. These thermo-associating polymers with biodegradable nature of CMG and CMT can have potential applications as smart injectables in controlled release technology and as thickeners in cosmetics and pharmaceutical formulations., (Copyright © 2014 Elsevier Ltd. All rights reserved.)

We have synthesized a 17-mer peptide (ERα17p) that is issued from the hinge region of the estrogen receptor α and which activates the proliferation of breast carcinoma cells in steroid-deprived conditions. In the present paper, we show that at a concentration of ~50 μM, it rapidly forms amyloid-like fibrils with the assistance of electrostatic interactions and that at higher concentrations, it spontaneously forms a hydrogel. By using biophysical, spectral and rheological techniques, we have explored the structural, biophysical and mechanical characteristics of ERα17p with respect to fibril formation and gelation., (Copyright © 2014 European Peptide Society and John Wiley & Sons, Ltd.)

We studied the stress-strain relation of model dual cross-link gels having permanent cross-links and transient cross-links over an unusually wide range of extension ratios λ and strain rates ϵ̇ (or time t = (λ - 1)/ϵ̇). We propose a new analysis method and separate the stress into strain- and time-dependent terms. The strain-dependent term is derived from rubber elasticity, while the time-dependent term is due to the failure of transient cross-links and can be represented as a time-dependent shear modulus which shows the same relaxation as in small strain. The separability is applicable except for the strain stiffening regimes resulting from the finite extensibility of polymer chains. This new analysis method should have a wide applicability not only for hydrogels but also for other highly viscoelastic soft solids such as soft adhesives or living tissues.

By taking advantage of a natural and abundant polymer as well as a straightforward film formation technique, this paper focuses on the conception and use of a new alternative tool for thermo-controlled cell detachment. Thermoresponsive xyloglucan was produced after partial galactose removal by a 24 h reaction with β-galactosidase. The obtained polymer (T24) was then activated by reaction with 4-nitrophenyl chloroformate (NPC) in order to graft a cyclic peptide presenting an arginine-glycine-aspartic acid (RGD) motif. The effect of RGD grafting on the sol-gel transition temperature of T24 is evaluated by rheological measurements. Solvent-casted films of T24-RGD successfully promoted cell adhesion, proliferation, and thermo-controlled detachment. The presented approach is a new alternative for cells sensitive to the proteolytic treatment routinely used for cell detachment. Because the RGD sequence used herein is widely recognized by different cell types, this protocol may be extended to other cells. Besides, the presented chemical route can be applied to different peptide sequences.

The chain length of hydrogen-bonded supramolecular polymers and thus their rheological properties can be controlled by the presence of so-called chain stoppers: these monofunctional monomers are able to interact with the monomers and break the polymer chains. In this letter, we show that the use of anions, strong hydrogen bond competitors, instead of precisely designed complementary units is a very simple approach to tuning the rheology of a bisurea-based hydrogen-bonded supramolecular polymer. All of the anions tested were able to break the supramolecular chains, resulting in a dramatic drop in the viscosity of the solutions and were found to be more efficient than a previously described organic stopper. A careful study of the rheological properties of bisurea solutions in the presence of H2PO4,N(C4H9)4 showed that the presence of this ion does not modify the nature of the bisurea supramolecular assembly. For a molar fraction of stopper of only 10(-5), the viscosity of bisurea solutions decreases by a factor of 10 as a result of the formation of shorter supramolecular assemblies.

The rheological properties of hydrogen bonded reversible aggregates in apolar solvent have been investigated. The zero shear viscosity, the plateau modulus and the terminal viscoelastic relaxation time exhibit power laws dependencies with the concentration that have been compared with the behaviours expected for reversible polymers. It appears that the dynamics originate from scission/recombination mechanisms. Moreover, the growth of the aggregates with concentration follows the laws observed and predicted for worm-like micelles at low concentrations allowing the length of the aggregates to be estimated 500 nm at 3 g L(-1). However, at the highest concentrations investigated, deviations from the power laws suggest the presence of some intrinsic chain stopper poisons in the solutions.

Platelet factor-4 (PF4/CXCL4) is an orphan chemokine released in large quantities in the vicinity of growing blood clots. Coagulation of plasma supplemented with a matching amount of PF4 results in a translucent jelly-like clot. Saturating amounts of PF4 reduce the porosity of the fibrin network 4.4-fold and decrease the values of the elastic and loss moduli by 31- and 59-fold, respectively. PF4 alters neither the cleavage of fibrinogen by thrombin nor the cross-linking of protofibrils by activated factor XIII but binds to fibrin and dramatically transforms the structure of the ensuing network. Scanning electron microscopy showed that PF4 gives rise to a previously unreported pattern of polymerization where fibrin assembles to form a sealed network. The subunits constituting PF4 form a tetrahedron having at its corners a RPRH motif that mimics (in reverse orientation) the Gly-His-Arg-Pro-amide peptides that co-crystallize with fibrin. Molecular modeling showed that PF4 could be docked to fibrin with remarkable complementarities and absence of steric clashes, allowing the assembly of irregular polymers. Consistent with this hypothesis, as little as 50 microm the QVRPRHIT peptide derived from PF4 affects the polymerization of fibrin.

In an attempt to establish connections between classical rheology and aging in paste colloidal suspensions, we report in this paper a large set of experimental results on a given system. We have studied suspensions of polyethylene oxide-protected silica particles and performed classical rheology experiments that exhibit a very nonlinear behavior. We have then evidenced aging through stress relaxation as observed in various glassy systems, and finally show other manifestations of aging through various rheological experiments. Qualitative agreement between these experimental results and the predictions of a simple model suggests that the behavior observed experimentally is governed by the competition between aging and mechanically induced rejuvenation.

Abiomimetic motility assay is used to analyze the mechanism of force production by site-directed polymerization of actin. Polystyrene microspheres, functionalized in a controlled fashion by the N-WASP protein, the ubiquitous activator of Arp2/3 complex, undergo actin-based propulsion in a medium that consists of five pure proteins. We have analyzed the dependence of velocity on N-WASP surface density, on the concentration of capping protein, and on external force. Movement was not slowed down by increasing the diameter of the beads (0.2 to 3 microm) nor by increasing the viscosity of the medium by 10(5)-fold. This important result shows that forces due to actin polymerization are balanced by internal forces due to transient attachment of filament ends at the surface. These forces are greater than the viscous drag. Using Alexa488-labeled Arp2/3, we show that Arp2/3 is incorporated in the actin tail like G-actin by barbed end branching of filaments at the bead surface, not by side branching, and that filaments are more densely branched upon increasing gelsolin concentration. These data support models in which the rates of filament branching and capping control velocity, and autocatalytic branching of filament ends, rather than filament nucleation, occurs at the particle surface.

This paper deals with the effect of different low-molecular-weight poly(ethylene oxide)s on the rheology of concentrated aqueous colloidal silica suspensions (volume fraction >0.2) with the aim of obtaining well-dispersed media. Results are correlated with the physico-chemical characteristics of the systems that govern the ranges of the various operating interactions, i.e., mainly surface coverage, molecular weight of the polymer, and ionic strength of the medium. Optimization of the fluidification occurs to be strongly linked to these parameters. An unexpected effect of free polymer bulk concentration leads to improved fluidification when the characteristic lengths of the system are correctly adjusted; it has been interpreted in the frame of recent theories. Copyright 2000 Academic Press.