Development of silver nanoparticles‐loaded calcium alginate beads embedded in gelatin scaffolds for use as wound dressings

Silver nanoparticles (AgNPs)‐loaded calcium alginate beads embedded in gelatin scaffolds were developed to sustain and maintain the release of silver (Ag⁺) ions over an extended time period. The UV irradiation technique was used to reduce Ag⁺ ions in alginate solution to AgNPs. The average sizes of AgNPs ranged between ca 20 and ca 22 nm. The AgNPs‐loaded calcium alginate beads were prepared by electrospraying of a sodium alginate solution containing AgNPs into calcium chloride (CaCl₂) solution. The AgNPs‐loaded calcium alginate beads were then embedded into gelatin scaffolds. The release characteristics of Ag⁺ ions from both the AgNPs‐loaded calcium alginate beads and the AgNPs‐loaded calcium alginate beads embedded in gelatin scaffolds were determined in either deionized water or phosphate buffer solution at 37 °C for 7 days. Moreover, the AgNPs‐loaded calcium alginate beads embedded in gelatin scaffolds were tested for their antibacterial activity and cytotoxicity. © 2014 Society of Chemical Industry     

Physicochemical properties of konjac glucomannan extracted from konjac flour by a simple centrifugation process

Konjac flour (KF) contains main polysaccharide, konjac glucomannan (KGM) that is applied in various applications; however, extraction of KGM is complicated. A simple centrifugation process was used to extract KGM from KF and the influence of extraction temperatures on its physicochemical properties was determined. The centrifugation process was effective for the extraction of KGM and the results revealed two effective temperatures (35 °C and 75 °C). The extracted KGM was easy to grind. Ash and protein contents of the extracted KGM were clearly reduced, however the ash and protein contents of the KGM extracted at the high temperature (75 °C) were significantly lower than that extracted at the low temperature (35 °C), and thus proofs the extraction at the high temperature to be more effective. Furthermore, improved purities in both extracted glucomannan samples were attained in comparison to commercial KGM. While the yield percentages of the samples differed, no significant disparity in morphology and particle size was determined. Particles of both extracted KGM were comparable in shape and size. Moreover, the transparency of both extracted KGM solutions was higher than commercial KGM solution. These results suggested that the extraction temperature at 75 °C is effective in extraction KGM from KF.     

Growth of single-crystalline rutile TiO2 nanorods on fluorine-doped tin oxide glass for organic–inorganic hybrid solar cells

Single-crystalline TiO₂ nanorods (TiO₂ NRs) are grown directly on FTO substrates by hydrothermal methods. The diameters and lengths of TiO₂ NRs are easily controlled by growth conditions. When used in hybrid solar cells, TiO₂ NRs function as the continuous pathway for fast electron transport to charge collecting electrode, demonstrating a high power conversion efficiency (PCE) of 3.21% with 140?nm long TiO₂ NRs. The bilayer polymer coating are introduced into 500?nm long TiO₂ NRs to reduce the surface roughness, resulting in the improved contact between the polymer blend and silver electrode and an enhanced PCE from 2.70 to 3.07%.     

Photo-electrocatalytic H2 evolution on poly(2,2′-bithiophene) at neutral pH

Vapour phase polymerised (VPP) polybithiophene (PBTh) on glassy carbon is revealed to be an efficient photo-electrocatalytic electrode for the hydrogen evolution reaction (HER). An onset potential of −0.03 V vs SCE for the HER is observed on illumination using visible light in 0.1 mol L⁻¹ phosphate buffer at pH 6.9, 600 mV lower in energy than E⁰. Hydrogen evolution is confirmed using gas chromatography with a calculated faradaic efficiency of 34% when holding at a potential of −0.5 V. Importantly, this process occurs without platinum and under neutral aqueous conditions thus revealing a significant but overlooked application for PBTh: a potential low-cost cathode material for the splitting of water.     

Influence of heat treatment temperature on the properties of the lithium disilicate-fluorcanasite glass-ceramics

This study aims to investigate the influence of heat treatment temperatures on the mechanical properties and chemical solubility (CS) of lithium disilicate-fluorcanasite glass-ceramics and to develop new dental materials. The glasses and glass-ceramics were prepared using CaF₂-SiO₂-CaO-K₂O-Na₂O-Li₂O-Al₂O₃-P₂O₅-based glass system using a conventional melt quenching method followed by a two-stage crystallization process. This two-stage method involves two heating temperature steps: first at a constant temperature (T_S1) of 600°C and second step at varying temperatures (T_S2) of 650, 700, 750, and 800°C. The crystallization behavior, phase formation, microstructure, translucency characteristic, density, hardness, fracture strength, and CS were investigated. It was found that the lithium disilicate crystal acted as the main crystalline phase, and the crystalline phase of fluorcanasite occurred at the heat treatment temperatures of 750 and 800°C. In addition, it was found that density, hardness, fracture strength, and CS increased while the translucency values decreased with increasing heat treatment temperatures. Furthermore, the CS increased dramatically when the fluorcanasite phases occurred in the glass-ceramic samples. The maximum density values, Vickers hardness, fracture toughness, and flexural strength are 2.56 g/cm³, 6.73 GPa, 3.38 MPa.m^1/2, and 259 MPa, respectively. These results may offer a possibility to design a new material for dental applications based on lithium disilicate-fluorcanasite glass-ceramics.     

Influence of the interaction between chloride and thiourea on copper electrodeposition

The interaction between chloride and thiourea in copper electrodeposition in a sulfate-plating bath was investigated. The sole addition of thiourea to the bath increased the polarization of the electrode potential during copper deposition, leading to very fine and smoothly structured deposit but with microscopic nodules distributed over the surface. When chloride was added to a plating solution containing thiourea, the copper deposition mechanism was changed, showing a depolarization of the electrode potential, and the copper deposits were found to have a relatively rougher microstructure, but without the formation of microscopic nodules. However, rough deposit surfaces having no distinct pattern were formed at the macroscopic scale. Observations of roughening evolution show that the rough surface was initiated from small holes formed across the deposit surface during the initial stage of deposition that eventually developed into visibly rough deposits. The copper deposition inside these holes and at other areas was expected to undergo different deposition mechanisms. Copper deposition in the areas that ultimately developed into holes was almost totally inhibited by the thiourea–Cu(I)–chloride complex film, not just in the grain growth process, but over practically the entire electrodeposition process. Conversely, copper deposition occurred in other areas under conditions where nucleation proceeded, but grain growth was inhibited to produce a fine, homogeneous microstructure. An uneven deposit surface that had different microscopic structures in different areas was then formed. The structure of the thiourea–Cu(I)–chloride film was strongly affected by the current density and appeared to break down completely if sufficiently high current density was applied to yield a fine and homogeneous microstructure that was also macroscopically smooth.     

Electrospun poly(L-lactic acid) fiber mats containing a crude Garcinia cowa extract for wound dressing applications

The copolymerization of sodium-2-acrylamido-2-methylpropane sulfonate with acrylonitrile and acrylamide in water has been studied at different concentrations of monomers, the initiator and the external electrolyte (NaCl). It was shown that an increase in the total concentration of the monomers leads to enriching the copolymers with units of the ionic monomer. A decrease in the initiator concentration causes the increase of the nitrile content in the product. Using of reactivity ratios r₁ and r₂ was shown to be invalid for this system as it does not allow one to appropriately predict the copolymer composition or its microstructure. The observed effects of significant dependence of copolymers composition on these factors have been explained by the influence of prepolymerization processes of formation of monomer assemblies and aggregates of monomers with growing macroradicals.     

Effectual drug-releasing porous scaffolds from 1,6-diisocyanatohexane-extended poly(1,4-butylene succinate) for bone tissue regeneration

Tooth extraction induces residual ridge resorption which impairs function and aesthetic of dental prostheses. This study aimed at developing new bone scaffolds to be used in a tooth socket for preserving bone mass from the residual ridge resorption. Scaffolds were fabricated from poly(1,4-butylene succinate) extended with 1,6-diisocyanatohexane (PBSu-DCH) by solvent casting and particulate leaching technique. Four different weight ratios of NaCl particles (200-400 μm; used as the porogen species) and the polymer were varied (i.e., 25, 30, 35, and 40% based on the weight of the polymer). Scaffolds were evaluated for their physical (i.e., morphology, porosity, pore volume, and pore size), physico-mechanical (i.e., mechanical properties and water retention ability), and biological properties (i.e., cytotoxicity and bone cell attachment). The potential for use of the as-prepared materials as effectual drug-releasing scaffolds for bone tissue regeneration was assessed by incorporating ipriflavone and studying the release of the drug from the drug-loaded scaffolds.