1: Magnetic Particles: Preparation, Properties and Applications: M. Ozaki. 2: Maghemite (gamma-Fe2O3): A Versatile Magnetic Colloidal Material C.J. Serna, M.P. Morales. 3: Dynamics of Adsorption and Oxidation of Organic Molecules on Illuminated Titanium Dioxide Particles Immersed in Water M.A. Blesa, R.J. Candal, S.A. Bilmes. 4: Colloidal Aggregation in Two-Dimensions A. Moncho-Jorda, F. Martinez-Lopez, M.A. Cabrerizo-Vilchez, R. Hidalgo Alvarez, M. Quesada-PMerez. 5: Kinetics of Particle and Protein Adsorption Z. Adamczyk.

Surface and Colloid Science

Novel crosslinking methods to design hydrogels

Starting from known properties of non-specific salt effects on the surface tension at an air–water interface, we propose the first general, detailed qualitative molecular mechanism for the origins of ion-specific (Hofmeister) effects on the surface potential difference at an air–water interface; this mechanism suggests a simple model for the behaviour of water at all interfaces (including water–solute interfaces), regardless of whether the non-aqueous component is neutral or charged, polar or non-polar Specifically, water near an isolated interface is conceptually divided into three layers, each layer being 1 water-molecule thick We propose that the solute determines the behaviour of the adjacent first interfacial water layer ( I 1 ); that the bulk solution determines the behaviour of the third interfacial water layer ( I 3 ), and that both I 1 and I 3 compete for hydrogen-bonding interactions with the intervening water layer ( I 2 ), which can be thought of as a transition layer The model requires that a polar kosmotrope (polar water-structure maker) interact with I 1 more strongly than would bulk water in its place; that a chaotrope (water-structure breaker) interact with I 1 somewhat less strongly than would bulk water in its place; and that a non-polar kosmotrope (non-polar water-structure maker) interact with I 1 much less strongly than would bulk water in its place We introduce two simple new postulates to describe the behaviour of I 1 water molecules in aqueous solution The first, the ‘relative competition’ postulate, states that an I 1 water molecule, in maximizing its free energy (—δG), will favour those of its highly directional polar (hydrogen-bonding) interactions with its immediate neighbours for which the maximum pairwise enthalpy of interaction (—δ H ) is greatest; that is, it will favour the strongest interactions We describe such behaviour as ‘compliant’, since an I 1 water molecule will continually adjust its position to maximize these strong interactions Its behaviour towards its remaining immediate neighbours, with whom it interacts relatively weakly (but still favourably), we describe as ‘recalcitrant’, since it will be unable to adjust its position to maximize simultaneously these interactions The second, the ‘charge transfer’ postulate, states that the strong polar kosmotrope–water interaction has at least a small amount of covalent character, resulting in significant transfer of charge from polar kosmotropes to water–especially of negative charge from Lewis bases (both neutral and anionic); and that the water-structuring effect of polar kosmotropes is caused not only by the tight binding (partial immobilization) of the immediately adjacent ( I 1 ) water molecules, but also by an attempt to distribute among several water molecules the charge transferred from the solute When extensive, cumulative charge transfer to solvent occurs, as with macromolecular polyphosphates, the solvation layer (the layer of solvent whose behaviour is determined by the solute) can become up to 5- or 6-water-molecules thick We then use the ‘relative competition’ postulate, which lends itself to simple diagramming, in conjunction with the ‘charge transfer’ postulate to provide a new, startlingly simple and direct qualitative explanation for the heat of dilution of neutral polar solutes and the temperature dependence of relative viscosity of neutral polar solutes in aqueous solution This explanation also requires the new and intriguing general conclusion that as the temperature of aqueous solutions is lowered towards o °C, solutes tend to acquire a non-uniform distribution in the solution, becoming increasingly likely to cluster 2 water molecules away from other solutes and surfaces (the driving force for this process being the conversion of transition layer water to bulk water) The implications of these conclusions for understanding the mechanism of action of general (gaseous) anaesthetics and other important interfacial phenomena are then addressed

https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0033583500005369

The Hofmeister effect and the behaviour of water at interfaces.

The last decade of research in the physical sciences has seen a dramatic increase in the study of nanoscale materials. Today, "nanoscience" has emerged as a multidisciplinary effort, wherein obtaining a fundamental understanding of the optical, electrical, magnetic, and mechanical properties of nanostructures promises to deliver the next generation of functional materials for a wide range of applications. While this range of efforts is extremely broad, much of the work has focused on "hard" materials, such as Buckyballs, carbon nanotubes, metals, semiconductors, and organic or inorganic dielectrics. Meanwhile, the soft materials of current interest typically include conducting or emissive polymers for "plastic electronics" applications. Despite the continued interest in these established areas of nanoscience, new classes of soft nanomaterials are being developed from more traditional polymeric constructs. Specifically, nanostructured hydrogels are emerging as a promising group of materials for multiple biotechnology applications as the need for advanced materials in the post-genomic era grows. This review will present some of the recent advances in the marriage between water-swellable networks and nanoscience.

Soft nanotechnology with soft nanoparticles.

Hydrogels, due to their excellent biochemical and mechnical property, have shown attractive advantages in the field of wound dressings. However, a comprehensive review of the functional hydrogel as a wound dressing is still lacking. This work first summarizes the skin wound healing process and relates evaluation parameters and then reviews the advanced functions of hydrogel dressings such as antimicrobial property, adhesion and hemostasis, anti-inflammatory and anti-oxidation, substance delivery, self-healing, stimulus response, conductivity, and the recently emerged wound monitoring feature, and the strategies adopted to achieve these functions are all classified and discussed. Furthermore, applications of hydrogel wound dressing for the treatment of different types of wounds such as incisional wound and the excisional wound are summarized. Chronic wounds are also mentioned, and the focus of attention on infected wounds, burn wounds, and diabetic wounds is discussed. Finally, the future directions of hydrogel wound dressings for wound healing are further proposed.

Functional Hydrogels as Wound Dressing to Enhance Wound Healing.

The prevalence of suboptimal outcome for surgical interventions in the treatment of full-thickness articular cartilage damage suggests that there is scope for a materials-based strategy to deliver a more durable repair. Given that the superficial layer of articular cartilage creates and sustains the tribological function of synovial joints, it is logical that candidate materials should have surface viscoelastic properties that mimic native articular cartilage. The present paper describes force spectroscopy analysis by nano-indentation to measure the elastic modulus of the surface of a novel poly(vinyl alcohol) hydrogel with therapeutic potential as a joint implant. More than 1 order of magnitude decrease in the elastic modulus was detected after adsorption of a hyaluronic acid layer onto the hydrogel, bringing it very close to previously reported values for articular cartilage. Covalent derivatization of the hydrogel surface with fibronectin facilitated the adhesion and growth of cultured rat tibial condyle chondrocytes as evidenced morphologically and by the observance of metachromatic staining with toluidine blue dye. The present results indicate that hydrogel materials with potential therapeutic benefit for injured and diseased joints can be engineered with surfaces with biomechanical properties similar to those of native tissue and are accepted as such by their constituent cell type.

Poly(vinyl alcohol) hydrogel as a biocompatible viscoelastic mimetic for articular cartilage.

Complexation between polyoxyethylene and polymethacrylic acid—the importance of the molar mass of polyoxyethylene

A viscous fluid, such as heavy crude oil which is too viscous to enable it to be pumped from a flowing phase of a reservoir into and along a pipeline for delivery to a refinery or other storage facility, may be contacted with a formulation to reduce its viscosity. The formulation comprises a polymeric material AA which includes -O- moieties pendent from a polymeric backbone thereof and said material is optionally cross-linked. In one embodiment, the formulation may comprise polyvinyl alcohol. In an alternative embodiment, the formulation may comprise a cross-linked polymeric material, such as cross-linked polyvinyl alcohol. After the viscous composition has been transported to a desired location, it may be separated from the other components.

Method for reducing the viscosity of viscous fluids

Evidence is presented from the literature for the importance of water structure for the stability of colloidal systems having hydrophilic character and the confused nature of the evidence for the involvement of hydration of hydrophobic surfaces. Streaming potential results at a polyvinylacetate/water interface in the presence of LiCl, LiBr, LiI, Li 2 SO 4 , NaCl, KCl, CsCl, Me 4 NCl, Et 4 NCl, and Bu 4 NCl are presented; the data suggest a cation dependent yield stress within the liquid contained in the diaphragm pores. Together with concomitant surface conductance determinations these results gave values of electrokinetic potential which indicated strong specific anion adsorption at the apolar interface which was also observed in the case of Cs + , K + , and the tetraalkylammonium ions; no specific adsorption was observed in the case of Li + and Na + . The evidence obtained is used to support a possible explanation of the confusion with regard to the importance of hydration for the stability of hydrophobic sols.

The influence of hydration upon the potential at the shear plane (zeta potential) of a hydrophobic surface in the presence of various electrolytes

Larval biotherapy is a debridement tool used in wound management. The mechanism of action involves degradation of eschar by serine proteases including chymotrypsin within the alimentary fluids of first instar Lucilia sericata. With the rationale of obviating some limitations of biotherapy, including cost, complexity of use, and patient reticence, the present study describes a mobile hydrogel formulation containing freeze-dried recombinant L. sericata chymotrypsin designed for topical application. Neither freeze-drying nor formulation into the hydrogel significantly attenuated the measured activity of released enzyme compared to fresh-frozen enzyme in aqueous solution. Gel electrophoresis confirmed qualitatively that the chymotrypsin/hydrogel formulation both with and without supplementary urea at 10% w/v degraded human chronic wound eschar ex vivo. Mindful that the hallmark of intractability of chronic wounds is aberrant biochemistry, the pH activity profile for the enzyme/hydrogel formulation was compared with exudate pH in chronic wounds of mixed aetiology in a cohort of 48 hospital in-patients. Five patients' wounds were acidic, however, the remainder were predominantly alkaline and coincided with the pH optimum for the insect enzyme. Thus, a recombinant L. sericata chymotrypsin and hydrogel formulation could represent a pragmatic alternative to larval therapy for the management of chronic wounds. © 2011 American Institute of Chemical Engineers Biotechnol. Prog., 2011

Donald Eagland

Papers

Poly(vinyl alcohol) hydrogel as a biocompatible viscoelastic mimetic for articular cartilage.

Complexation between polyoxyethylene and polymethacrylic acid—the importance of the molar mass of polyoxyethylene

Method for reducing the viscosity of viscous fluids

The influence of hydration upon the potential at the shear plane (zeta potential) of a hydrophobic surface in the presence of various electrolytes

Recombinant Lucilia sericata chymotrypsin in a topical hydrogel formulation degrades human wound eschar ex vivo.