A novel injectable,cohesive and toughened Si-HPMC (silanized-hydroxypropyl methylcellulose) composite calcium phosphate cement for bone substitution

This study reports on the incorporation of the self-setting polysaccharide derivative hydrogel (silanized-hydroxypropyl methylcellulose, Si-HPMC) into the formulation of calcium phosphate cements (CPCs) to develop a novel injectable material for bone substitution. The effects of Si-HPMC on the handling properties (injectability, cohesion and setting time) and mechanical properties (Young’s modulus, fracture toughness, flexural and compressive strength) of CPCs were systematically studied. It was found that Si-HPMC could endow composite CPC pastes with an appealing rheological behavior at the early stage of setting, promoting its application in open bone cavities. Moreover, Si-HPMC gave the composite CPC good injectability and cohesion, and reduced the setting time. Si-HPMC increased the porosity of CPCs after hardening, especially the macroporosity as a result of entrapped air bubbles; however, it improved, rather than compromised, the mechanical properties of composite CPCs, which demonstrates a strong toughening and strengthening effect. In view of the above, the Si-HPMC composite CPC may be particularly promising as bone substitute material for clinic application.     

Urease-induced calcification of segmented polymer hydrogels – A step towards artificial biomineralization

Natural organic/inorganic composites, such as nacre, bones and teeth, are perfectly designed materials with exceptional mechanical properties. Numerous approaches have been taken to synthetically prepare such composites. The presented work describes a new way of mineralizing bulk materials on a large scale following the approach of bioinduced mineralization. To this end, a series of polymer conetworks with entrapped urease were prepared. After polymerization, the entrapped urease shows high enzymatic activity. The bioactive polymer conetworks were then treated with an aqueous mixture of urea and CaCl₂. The urease-induced calcification indeed allows formation of carbonate crystals exclusively within the hydrogel even at room temperature. The influence of network composition, degree of cross-linking, immobilized urease concentration and temperature of calcification were investigated. By varying these parameters, spherical, monolithic clusters, as well as bar-like nanocrystals with different aspect ratios in spherical or dendritic arrays, are formed. The grown nanocrystals improve the stiffness of the starting material by up to 700-fold, provided that the microstructure shows a dense construction without pores and strong interaction between crystals and network. The process has the potential to generate a new class of hybrid materials that would be available on the macroscopic scale for use in lightweight design and medicine.     

Critical Review of Additive Mastoplastic with Arion Hydrogel Prosthesis

The author reviews his personal experience using additive mastoplastics with the hydrogel prosthesis produced in France by Arion. The enumeration of cases covers 143 patients (285 prothesis) with 36 months of follow-up evaluation. The positive aspects of this filling (especially the radiotransparency) and its complications are considered, with special attention paid to the wrinkling effect that may be caused by some physical instability of the hydrogel. The well-known controversy of 1992 concerning silicon mammary prostheses encouraged scientists to seek alternative solutions in the field of prosthetic extenders. This effort sometimes produced negative solutions such as the soya oil prosthesis, but at the same time provided materials with excellent physical–chemical qualities, with subsequent positive effects from a clinical point of view. This work is dedicated to one of these products, the Arion hydrogel. After 6-years of utilization with a 36-month follow-up period, 285 prosthesis have been fitted for 143 patients.     

Synthesis, characterization and evaluation of IPN hydrogels for antibiotic release

We prepared new ternary interpenetrating polymeric networks (IPN) systems containing chitosan, poly(N-vinylpyrrolidone) and poly(acrylamide) polymers. IPNs were synthesized by radical polymerization of acrylamide monomers in presence of glutaraldehyde (G) and N,N'-methylenebisacrylamide as crosslinkers and the other polymers. These IPNs were named as C-P-A. Glutaraldehyde were used in different concentration to control the network porous of IPNs. Spectroscopic and thermal analyses of these cylindrical shaped IPNs were made with fourier transform infrared spectroscopy analysis, thermogravimetric analysis, and thermomechanical analysis. Swelling studies of IPNs were carried out at pH 1.1 and pH 7.4 at 37°C. The swelling and diffusion parameters of IPNs in these solutions were calculated. Amoxicillin as a bioactive species was entrapped to the IPNs during synthesis. In vitro release kinetics of IPNs were investigated. The experimental data of swelling and release studies suggest clearly that the swelling and release process obeys second-order kinetics. The release of the entrapped bioactive species from IPNs depends on the degree of crosslinking of the polymer and pH of the medium at body temperature. We observed that amoxicillin release at pH 1.1 was higher than at pH 7.4. As a result, IPNs-based chitosan with different cross-linker concentration could be promising candidates for formulation in oral gastrointestinal delivery systems.     

Effect of enhancers and retarders on percutaneous absorption of flurbiprofen from hydrogels

The effect of enhancers/retarders on the transdermal absorption of flurbiprofen from cellulose hydrogels was studied in vitro. The release rate of flurbiprofen and the viscosity of hydrogel matrices were also examined. The flux of flurbiprofen from cellulose hydrogels approximated that from aqueous buffers, whereas the skin reservoir of flurbiprofen was lower with hydrogels. Incorporation of the cosolvents, propylene glycol (PG) and ethanol, did not significantly increase skin absorption of flurbiprofen. Ethanol even reduced the skin reservoir of the drug. Oleic acid, an unsaturated fatty acid, produced the largest skin reservoir of the drug when incorporated into the hydrogels. D-Limonene, a cyclic monoterpene, showed the greatest ability to enhance the flux of flurbiprofen. However, phospholipids as retarders markedly reduced the skin absorption of flurbiprofen. The mechanisms by which enhancers/retarders govern flurbiprofen permeation were elucidated by in vitro permeation studies using various skin types (enhancers/retarders-pretreated skin, stratum corneum (SC)-stripped skin, and delipidized skin) and histological examination. The results suggest different mechanisms and skin structural modifications caused by different enhancers/retarders.     

Surface hydration of hydrogel contact lenses

A hand refractometer was used to measure the surface hydration of soft contact lenses of three different water contents, in a randomized, double masked study conducted on nine subjects. No statistically significant difference was found after 30 minutes of lens wear between the hydration levels at the front and back surfaces of Permathin (42.5 % nominal water content) and Snoflex 50 (50% nominal water content) hydrogel lenses; however, there was a significant difference for Gelfiex 60 (60% nominal water content) lenses, the back surface being more hydrated than the front surface. These findings suggest that there may be a water gradient between the front and back surfaces of higher water content hydrogel lenses during wear. Whilst the magnitude of the difference between surface hydration levels is small and of little consequence in the routine clinical measurement of water content using a hand refractometer, this phenomenon could be of aetiological significance with respect to the occurrence of multiple corneal erosions observed in patients wearing very thin, high water content lenses.     

Thermal control of drug release by a responsive ion track membrane observed by radio tracer flow dialysis

The combination of a responsive hydrogel with a rigid porous supporting structure yields a membrane with high mechanical strength and high on-off-permeability ratio. A membrane consisting of an ion track filter with a thermally responsive lining was prepared by penetrating a 19 μm thick foil of poly(ethylene terephthalate) (PET) with swift heavy ions at a fluence of 5·10⁵ ions/cm², followed by etching of the ion tracks to generate an ion track filter with 2.9 μm pore diameter, onto which a thin layer of poly(N-isopropylacrylamide) (NIPAAm) hydrogel was grafted. It was revealed that the mass flow of various molecules (water, chloride⁻, choline⁺, insulin, and albumin) through the membrane could be thermally controlled. The on-off-permeability ratio ranged between 3 and 10 increasing with molecular weight. Over a storage time of 5 months the permeabilities varied up to a factor of 2.6, while the on-off-permeability ratio and temperature sensitivity remained practically constant.     

凝胶材料制备方法及其反应动力学的研究进展

部分水凝胶材料具有良好的生物相容性、低细胞毒性和生物可降解性,广泛应用于组织工程和生物医药等领域,其中采用天然高分子明胶、壳聚糖和海藻酸钠制备复合凝胶材料,负载骨髓间充质干细胞用于修复和治疗骨缺损成为近年来的研究热点之一。因为水凝胶材料抗张强度低和化学稳定性差,所以研究凝胶反应机理和凝胶反应动力学对提高水凝胶的性能具有重要意义。本文总结了明胶、壳聚糖和海藻酸钠凝胶材料的制备方法和凝胶反应机理,比较了不同凝胶反应动力学研究方法,介绍凝胶复合材料在骨修复中的应用,为天然高分子凝胶材料的分子设计和临床应用提供思路。     

The influence of degree-of-branching and molecular mass on the interaction between dextran and Concanavalin A in hydrogel preparations intended for insulin release

The interactions of a number of commercially available dextran preparations with the lectin Concanavalin A (ConA) have been investigated. Dextrans over the molecular mass range 6 × 10³-2 × 10⁶ g mol⁻¹ were initially characterised in terms of their branching and hence terminal ligand density, using NMR. This showed a range of branching ratios between 3% and 5%, but no clear correlation with molecular mass.The bio-specific interaction of these materials with ConA was investigated using microcalorimetry. The data obtained were interpreted using a number of possible binding models reflecting the known structure of both dextran and the lectin.The results of this analysis suggest that the interaction is most appropriately described in terms of a two-site model. This offers the best compromise for the observed relationship between data and model predictions and the number of parameters used based on the chi-squared values obtained from a nonlinear least-squares fitting procedure. A two-site model is also supported by analysis of the respective sizes of the dextrans and the ConA tetramer.Using this model, the relationship between association constants, binding energy and molecular mass was determined.