Key Engineering Materials Vols. 361-363

Abstract: A great number of studies have shown that diamond-like carbon (DLC) coatings could be developed for orthopaedic implants, but few articles have been published about in vivo evaluation. In this study, DLC coatings were deposited on titanium alloy (Ti-13Nb-13Zr) implants using the plasma immersion implantation and deposition (PIII-D), and the in vivo biocompatibility of DLC coatings was evaluated into both muscular tissue and femoral condyles of rats. Results indicate that DLC coatings are biocompatible in vivo, and DLC-coated implants were observed directly bonding to bone without any intervening soft tissue layer.

Abstract: Tantalum metal was soaked in NaOH and CaCl2 solutions, and then subjected to heat treatment at 500°C. EDX analysis showed that about 6.5 at. % of Na was incorporated into the surface of the tantalum metal by the first NaOH treatment. These Na+ ions were replaced by Ca2+ ions by the subsequent CaCl2 treatment. According to TF-XRD patterns, an amorphous sodium tantalate was seemed to be formed on the tantalum metal by the NaOH treatment and transformed into amorphous calcium tantalate by the CaCl2 treatment. This phase was crystallized into Ca2Ta2O7 by heat treatment. Critical detaching load of the surface of the CaCl2-treated tantalum metal was as low as 5mN, while as high as 42mN after the heat treatment. Apatite-forming ability of the NaOH-treated tantalum metal in a simulated body fluid (SBF) was appreciably increased by the CaCl2 treatment and maintained even after the heat treatment.

Abstract: Radiation induced graft polymerization of 2-hydroxyethyl acrylate (HEMA) on titanium surface and couple gelatin have been studied in the paper. The composition and properties of surface modified titanium were investigated by several surface sensitive techniques: X-ray photoelectron spectrum (XPS) and scanning electron microscopy (SEM). Results of the technological measurements show that surface chemistry is affected throughout the surface modification process, finally leading to a complete and homogeneous vinyl compound overlayer on top of the titanium samples. And the modified porous titanium exhibits an interesting mineralization in simulated body fluid (SBF) and an adsorptive property in bovine serum albumin (BSA).

Abstract: A non-bioactive implant device can easily be changed to in vitro bioactive with a thin coating of crystalline TiO2. This crystalline coating can be deposited very thin with great step coverage at a low temperature with Atomic Layer Deposition (ALD). An anatase TiO2 coating was built up atomic layer by atomic layer using TiI4 and H2O as precursors in a hot wall furnace. Several hundreds of cycles resulted in a 10-30nm well defined TiO2 of anatase phase on both Si and Ti substrates. These coatings were shown to be bioactive when immersed in simulated body fluid in vitro, as hydroxyapatite (HA) formed on the surface. The surface roughness of the substrates affected the adhesion of the HA. The adhesion was low on the smooth Si but much better on the 100 times rougher Ti. The ALD technique is promising for coating substrates of all shapes with bioactive crystalline TiO2 at a low temperature.

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: Undesirable phase and microstructure formation, and poor HAP/metal bonding strength restrict the fabrication technique to obtain HAP and other calcium phosphate ceramic coatings. In this paper a bioceramic composite coating, which includes HAP andβ-Ca2P2O7, was obtained by laser cladding with pre-depositing mixed powders of CaHPO4·2H2O and CaCO3 directly on the 316L stainless steel metal substrate. The phases, microstructure and bonding feature of the bioceramic composite coating are characterized by X-ray diffraction(XRD), scanning electron microscopy-energy dispersive spectroscopy(SEM-EDS). The microstructure of the coating consists of minute granular HAP that is distributed among the overlapped club-shapedβ-Ca2P2O7. Uniform presences of Ca, P and O in bioceramic composite coating supplie necessary elements for the synthesis of HAP andβ-Ca2P2O7. Diffusions inwards of P and O into alloying layer help form the chemical metallurgical bonding and composition gradient distributions are present. a chemical metallurgical bonding was formed between the bioceramic composite coating and metal substrate.

Abstract: This paper performs a new way of a resorbable surface on Ti alloy preparation. Precalcification of a chemically treated Ti or Ti alloy surface by a supersaturated calcification solution - SCS2 (high content of Ca2+ as well as (PO4)3- ions) allows to short of an induction period in SBF solution (practically immediate reaction stats a hydroxyapatite precipitation). Soluble octacalcium phosphate (Ca8H2(PO4)6. 5H2O was detected by RTG on the surface after calcification. Presumption is: a healing time of the calcified Ti alloy could be shortened.

Abstract: The protein adsorption behavior was investigated for highly (001) oriented hydroxypatatite coatings (HACs). Highly (001) oriented (HO-) HACs and HAC with low orientation (LO-HAC) were prepared on titanium (Ti) substrates through a radio-frequency thermal plasma spraying method. Sintered HA pellets (S-HA) was also prepared as a control. The solution of 22 'g/100 'l PBS of the fluorescein-isothiocyanate (FITC) labeled bovine serum albumin (FITC-BSA), immunoglobulin G (FITC-IgG) and cytochrom c (FITC-CCC) was separately dropped on the surface of HACs and was incubated for 30 min. After the incubation, such HACs were washed with the PBS additionally supplemented with 125mM NaCl and observed using a fluorescence microscope. Fluorescence microscopic examination indicates that FITC labeled proteins somewhat adsorbed on the HACs, while proteins adsorbed little on S-HA surface. In particular, it can be seen that FITC-CCC adsorbed more prominently on the HO-HAC.

Abstract: Apatite nuclei were precipitated in the pores of titanium in simulated body fluid (SBF) and titanium-apatite nuclei composite was obtained. Apatite was induced by the apatite nuclei inside the pores of the composite and apatite layer was formed on the composite surface by soaking in SBF. The apatite layer showed high adhesive strength to the composite due to a mechanical interlocking effect between the composite and the apatite.

Abstract: In the present work, technique of plasma polymerization was used to generate amido (- NH2) and carboxyl (-COOH) on titanium surface for immobilizing bovine serum albumin (BSA). After plasma polymerization of allylamine and crylic acid, the contact angle with respect to double distilled water significantly increased. Surface components were detected by X-ray photoelectron spectroscopy and Fourier transform infrared reflection-absorption spectroscopy. The results showed that BSA was successfully immobilized on the titanium surface and the amounts of BSA on specimens were relied on the properties of thin film deposited through plasma polymerization, which was corresponding to the ultraviolet spectrophotometer result.