Viscoelasticity,mechanical properties,and in vivo biocompatibility of injectable polyvinyl alcohol/bioactive glass composite hydrogels as potential bone tissue scaffolds

Abstract

An injectable composite hydrogel composed of polyvinyl alcohol (PVA) and bioactive glass (BG) particles were synthesized by a physical crosslinking approach. The morphology, mechanical properties, and viscoelasticity of the PVA/BG composite hydrogel were characterized. Scanning electronic microscopy (SEM) showed uniform and homogeneous distribution of BG particles throughout the composite hydrogel. The incorporation of 2.5?wt% of BG particles in the composite hydrogel formulations, enhanced the static compressive strength and static elastic modulus by 325% and 150%, respectively. The storage molds (G′) was greater than the loss modules (G′′) at all the frequency range studied, which revealed a self-standing elastic composite hydrogel with a smooth injectability. The PVA/BG composite hydrogel was also implanted subcutaneously in the dorsal region of adult male rats. After 4?weeks of implantation, no inflammatory cells were seen within and around the implant, which indicated that the composite hydrogel was biocompatible. The properties of the synthesized injectable PVA/BG composite hydrogel demonstrate its capability toward bone regeneration.     

Semiquantitative determination of aromatic andα,β-unsaturated aldehydes by circular thin-layer chromatography

Summary A method for semiquantitative determination of aromatic and,-unsaturated aldehydes such as salicylaldehyde, anisaldehyde, vanillin, veratraldehyde, piperonal, cinnamaldehyde, furfural andp-dimethylaminobenzaldehyde by making circular spots of their isonicotinoyl hydrazones on chromatoplates with circular thin-layer Chromatographic apparatus and their comparison with sensitivity standards has been described. The accuracy is ± 5% and the method is rapid, simple and economical.

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Zusammenfassung Ein Verfahren zur semiquantitativen Bestimmung aromatischer und,-ungesättigter Aldehyde wie Salioylaldehyd, Anisaldehyd, Vanillin, Veratrumaldehyd, Piperonal, Zimtaldehyd, Furfural und p-Dimethylaminobenzaldehyd durch Dünnschicht-Ringchromatographie ihrer Isonikotinsäurehydrazone und Vergleich mit Standardchromatogrammen wurde beschrieben. Die Genauigkeit beträgt ±5%.

     

Aromatic polyether, -ketone, -sulfones as laminating resins. XII. Derivatives of 2,2′-diphenylethynyldiphenyl which cure by an intramolecular cyclization

Polymers made from 2,2′-diiododiphenyl-4,4′-dicarbonyl dichloride, diphenyl ether, and isophthaloyl chloride have been made and converted to the 2,2′-diphenylethynyl derivatives. Introduction of units of isophthaloyl chloride reduced the melting point of these polymers to about 200°C, and they could then be cured by heating. A good glass laminate was prepared and cured from one of the polymers.     

Reactions of [(Cp)2Ti(NCS)2] as a potential metalloligand; synthesis and physico-chemical investigations of novel heterobimetallic complexes

Summary Bis(cyclopentadienyl)titanium(IV) diisothiocyanate [(Cp)₂-Ti(NCS)₂] reacts with MCl₂ (M = Cu, Pd or Pt), [CuCl(PPh₃)₃], [RuCl₂(PPh₃)₃] and [RuCl₂(DMSO)₄] (DMSO = dimethylsulphoxide) giving solid compounds of stochiometry [(Cp)₂Ti(-NCS)₂MCl₂] (M = Cu, Pd or Pt), [(Cp)₂Ti(-NCS)₂CuCl(PPh₃)], [(Cp)₂Ti(-NCS)₂-RuCl(PPh₃)₂]Cl and [(Cp)₂Ti(-NCS)₂RuCl₂(DMSO)2]. These products have been characterized by physicochemical and spectroscopic methods.     

Thin-Layer Chromatographic Separation of Cadaverine and Ornithine,and Spectrophotometric Quantification

JPC – Journal of Planar Chromatography – Modern TLC -     

On the estimation of stability parameters from heat-induced conformational transition curves of proteins

A method is suggested to determine valid and authentic values of thermodynamic stability parameters of proteins from their heat-induced conformational transition curves. We show (a) that the estimate of ΔH_m ^van, the enthalpy change on denaturation at T_m, the midpoint of denaturation, is significantly less than ΔH_m ^cal, the value obtained by the calorimetric measurements, if the analysis of the conformational transition curve uses the conventional method which assumes a linear temperature-dependence of the pre- and post-transition baselines; and (b) that there exists an excellent agreement between ΔH_m ^van and ΔH_m ^cal values of proteins, if the analysis of thermal denaturation curves assumes that the temperature-dependence of pre- and post-transition baselines is described by a parabolic function. The latter analysis is supported by our observations that the temperaturedependencies of the absorption and circular dichroism properties of protein groups are indeed nonlinear. It is observed that the estimate of ΔC_p, the constant-pressure heat capacity change is independent of the model used to describe the temperaturedependence of the pre- and post-transition baselines. An important conclusion is that for proteins which exhibit a two-state character, all stability parameters are measured with the same error as that observed with a calorimeter.     

Sequence-dependent conformational energy of DNA derived from molecular dynamics simulations: toward understanding the indirect readout mechanism in protein-DNA recognition

Sequence dependence of DNA conformation plays a crucial role in its recognition by proteins and ligands. To clarify the relationship between sequence and conformation, it is necessary to quantify the conformational energy and specificity of DNA. Here, we make a systematic analysis of dodecamer DNA structures including all the 136 unique tetranucleotide sequences at the center by molecular dynamics simulations. Using a simplified conformational model with six parameters to describe the geometry of adjacent base pairs and harmonic potentials along these coordinates, we estimated the equilibrium conformational parameters and the harmonic potentials of mean force for the central base-pair steps from many trajectories of the simulations. This enabled us to estimate the conformational energy and the specificity for any given DNA sequence and structure. We tested our method by using sequence-structure threading to estimate the conformational energy and the Z-score as a measure of specificity for many B-DNA and A-DNA crystal structures. The average Z-scores were negative for both kinds of structures, indicating that the potential of mean force from the simulation is capable of predicting sequence specificity for the crystal structures and that it may be used to study the sequence specificity of both types of DNA. We also estimated the positional distribution of conformational energy and Z-score within DNA and showed that they are strongly position dependent. This analysis enabled us to identify particular conformations responsible for the specificity. The presented results will provide an insight into the mechanisms of DNA sequence recognition by proteins and ligands.