Papers by Keyword: Organic-Inorganic Hybrid

Abstract: Titania/organically modified silanes (ormosils) organic-inorganic hybrid thin films doped with azobenzene small molecules are prepared by a low temperature sol-gel spin-coating process for optical switch applications. Acid-catalyzed solutions of γ-glycidoxypropyltrimethoxysilane and methyltrimethoxysilane mixed with tetrapropyl orthotitanate are used as matrix precursors. Atomic force microscopy is used to study the morphological properties of the hybrid thin films. Results indicate that crack-free thin films with a thickness of about 1.3μm can be obtained by a single spin-coating process after a low heat treatment temperature. The propagation mode properties of the hybrid thin films are also studied by employing a prism coupling technique. The photo-responsive properties of the hybrid films baked at different temperatures are induced by an irradiation with UV light and subsequent visible light.

Abstract: So-called bioactive ceramics are used for bone-repairing owing to attractive features such as direct bone-bonding in living body. However, there is limitation on clinical applications due to their inappropriate mechanical properties performances such as higher brittleness and lower fracture toughness than natural bone. To overcome this problem, hybrid materials have been developed by modification of calcium silicate, that is basic component of bioactive ceramics, with organic polymer. It is known that bioactive ceramics bond to bone through bone-like apatite layer which is formed on their surfaces by chemical reaction with body fluid. We attempted preparation of bioactive organic-inorganic hybrids from Glucomannan that is a kind of complex polysaccharide, and calcium silicate. Hybrids were prepared from glucomannan and tetraethoxysilane (TEOS). They were treated with 1M (=mol·m-3) CaCl2 aqueous solution for 24 hours. Then ability of apatite formation on the hybrids was examined in vitro using simulated body fluid (SBF, Kokubo solution). Surface structure of the specimens was examined by thin-film X-ray diffraction (TF-XRD), scanning electron microscopic (SEM) observation. The hybrids with TEOS:Glucomannan= 1:1 to 4:1 in mass ratio formed the apatite in SBF within 3 or 7 d, when they were previously treated with CaCl2 solution.

Abstract: Natural bone is a kind of organic-inorganic hybrid composed of collagen and apatite crystals with a structure that provides specific mechanical properties such as high fracture toughness and flexibility. Materials exhibiting both high flexibility and bioactivity similar to natural bone are required for novel bone-repairing materials in medical fields. We expect that we can design such materials by mimicking the bone structure. Biomimetic process has been paid much attention where bone-like apatite is deposited on organic polymers in simulated body fluid (SBF). In this study, we investigated influence of cross-linking agents on apatite-forming ability of pectin gels. Pectin is a polysaccharide abundant in carboxyl group. Pectin gels were prepared by cross-linking of pectin aqueous solutions with calcium ions or divinylsulfone (DVS). Apatite-forming ability of the gels was examined in SBF. The citrus-derived pectin showed tendency to form the largest amount of the apatite independent on a kind of cross-linking agents in SBF.

Abstract: Novel hybrid gels in the system gelatin-GPTMS-TEOS were prepared via a sol-gel route, and their ability to release Si(IV) was examined using MG63 osteoblast-like cell culture. The amount of Si released and the release rate were controllable by changing the mixing ratio of GPTMS and TEOS. In addition, the hybrids had biocompatible surfaces. It is expected that the hybrids will be utilized for the investigation of the effect of Si on cell differentiation and tissue regeneration.

Abstract: Titanium (Ti) and its alloy have sufficient mechanical properties to be utilized as artificial hip joints and article teeth. However, they have no bioactivity. In this work, we prepared bioactive coatings on Ti by sol-gel techniques. The coatings had a double layered structure. Underlying layer was methylsiloxane (MS) consisted of methyltriethoxysilane (MTES). Top layer was MS-Ca-Nb-Ta hybrid composed of MTES, calcium nitrate tetrahydrate, pentaethoxy-niobium and pentaethoxy-tantalum. The coating exhibited formation of bone-like apatite in SBF immersion test. Adhesive strength of the coating was found to be 1.8 MPa.

Abstract: Apatite-polymer hybrids are expected as novel bone substitutes exhibiting bone-bonding ability and mechanical performances analogous to those of natural bone. In this study, we attempted preparation of organic-inorganic hybrids from different pectins such as pectic acid, apple-derived pectin and citrus-derived pectin through apatite deposition in simulated body fluid (SBF). Pectin gels were prepared by CaCl2 treatment of aqueous solutions of pectin. Apatite-forming ability of the gels was examined in SBF. The citrus-derived pectin showed tendency to form the largest amount of the apatite in SBF.

Abstract: Development of the organic-inorganic hybrids composed of apatite crystals and organic polymer is expected to be an attractive material that has mechanical properties similar to natural bone as well as bone-bonding ability, i.e. bioactivity. It is reported that the carboxyl groups (-COOH) on the surfaces of the organic substrates act as a catalyst for induction of heterogeneous nucleation of apatite. The present authors previously showed that the apatite was successfully deposited on the polyglutamic acid gels containing abundant carboxyl groups through the biomimetic process, when they were priorly treated with calcium chloride solution. In this study, we fabricated the polyglutamic acid gels with different degree of cross-linking. Effect of the cross-linking on their ability of the apatite formation was examined in simulated body fluid (SBF). It was suggested that the apatite deposition on the polyglutamic acid gels is governed not only by the amount of –COOH that induces the heterogeneous nucleation of the apatite, but also by swelling property that controls local increase in degree of supersaturation with respect to the apatite.

Abstract: So-called bioactive ceramics bond to living bone through the apatite layer formed on their surfaces in the body. The apatite deposition is triggered by dissolution of calcium ion (Ca2+) and by silanol (Si-OH) group formed on the surfaces of the ceramics. It is expected that organic modification of these components would produce bioactive materials with high flexibility. In this study, we examined bioactivity and mechanical properties of the organic-inorganic hybrids from starch by modification with silanol group and calcium ion. Effect of cross-linking agent was also investigated. The obtained hybrids showed bioactivity and mechanical properties analogous to those of human cancellous bone by appropriate control in their compositions. Addition of cross-linking agent to improve mechanical strength of the hybrids did not decrease their bioactivity.

Abstract: Organic-inorganic hybrid monoliths with well-defined macropores and/or mesopores have been synthesized by a sol-gel process accompanied by polymerization-induced phase separation. Using aklyltrialkoxysilanes and alkylene-bridged alkoxysilanes, two different categories of organo-siloxane networks have been characterized in view of macroporoisity based on phase separation as well as mesoporosity based on supramolecular templating by surfactants. The alkyl-terminated polysiloxane network exhibited substantial surface hydrophobicity together with the mechanical flexibility. On the other hand, the alkylene-bridged network behaved much more similarly to those prepared from tetraalkoxysilanes with regard to surface hydrophilicity, mechanical rigidness and mesopore-forming ability. Supramolecular templating of mesopores embedded in the gel skeletons comprising well-defined macroporous network has proven to give wide variety of hierarchically designed macro-mesoporous organic-inorganic hybrid materials.