Papers by Keyword: Biomimetic Coating

Abstract: Metallic materials including stainless steel, cobalt-chromium alloys, titanium and its alloys, and nickel-titanium (NiTi) shape memory alloys have been used in biomedical applications since the 1940s due to their favorable mechanical properties. Classified as a smart material, NiTi alloy has gained noticeable popularity in biomedical fields such as orthopedic, dental, and cardiovascular applications as it retains reasonable corrosion resistance and biocompatibility along with unique shape memory properties. However, several studies have shown their limits in medical applications due to the risk of Ni ions release from the NiTi implant surface. In order to prevent Ni release, ceramic-based surface coatings such as hydroxyapatite, alumina, and titanium dioxide have been proposed applied by various methods such as electrophoretic deposition, sol-gel, biomimetic and dip coating. In this work, HA coatings on NiTi wire samples were obtained by using biomimetic and dip-coating methods. The biomimetic coating consisted of immersing the NiTi wire samples into simulated body fluid for 24 and 48 h periods, whereas dip coating was accomplished by placing the NiTi wire samples into the HA suspension and retracting the sample with a controlled speed. The effects of the two coating methods on coating quality, surface characteristics and corrosion behavior of NiTi wire samples were investigated. Dip coating method was shown to be a more favorable technique for the NiTi wire samples used throughout this study.

Abstract: Low temperature deposition techniques of bioceramics coatings are now being researched and developed to avoid deficiencies inherent in high temperature techniques. Biomimetic coatings is a solution-based method conducted at ambient temperature to deposit bioactive coatings on the surface. The current study aims to investigate the effect of ultraviolet (UV) irradiation on the coating of bone-like apatite on the anodised surface. High purity titanium foils were anodised with an applied voltage of 350 V, current density of 70 mA.cm^-2 in mixture of 0.04 M β-glycerophosphate disodium salt pentahydrate (β-GP) and 0.4 M calcium acetate (CA) for 10 min. After anodic oxidation, UV light treatment was conducted in pH-adjusted distilled water for 12 hours with ultraviolet light A (UVA) irradiation. Subsequently, the UV-treated anodised titanium foils were soaked in SBF for 7 days with/without UVA irradiation. After SBF immersion for 7 days, anodised titanium with combination of UV light treatment and UV irradiation during in vitro testing was fully covered by highly crystalline bone-like apatite at maximal thickness of 2.8 μm. This occurred mainly due to the formation of large amounts of Ti-OH groups which act as nucleation sites for bone-like apatite. This study also revealed that UV irradiation during in vitro testing is superior in promoting growth of bone-like apatite compared to UV light treatment. The suggested mechanism for bone-like apatite formation on anodised titanium under different UV irradiation conditions is illustrated in this article. The findings of this study indicated that biomimetic bone-like apatite coating with assistance of UV irradiation is an effective method in accelerating the formation of bone-like apatite.

Abstract: Objective: To functionalize the Bio-Oss^® Block with biomimetic coating incorporating BMP2 and evaluate the release kinetics of the incorporated BMP2 In Vitro.Materials and methods: Bio-Oss^® Blocks were prepared with the size of 7mm x 10mm x 4mm. Each block was immersed and suspended in 300ml 5-fold-concentrated modified Tyrode solution for 24 hours to form a seeding substratum. BMP2 at the concentration of 10ug/ml was added into 120ml supersaturated calcium phosphate solution and co-precipitated within the growing layer for 48 hours. The loading amount of incorporated BMP2 was determined using enzyme-linked immunosorbent assay . The surface characterization of the coating was evaluated by scanning electron microscopy. The distribution of coating-incorporated protein was mapped by a confocal laser-scanning microscope. BMP2 release profiles from the functionalized blocks under different circumstances were monitored. Results: The total loading of BMP2 in a BMP2-incorporated-block is 50.35 ± 6.41μg. The crystalline coating layer deposited on both the superficial surfaces and internal surfaces of the blocks. The BMP2 was distributed homogeneously in the whole block. The coating-incorporated depot of BMP2 barely released in Tris-HCl buffered solution (pH of 7.4). However, when the functionalized blocks were immersed in Citric acid-Sodium citrate buffered solution (pH of 5), or were co-cultured with osteoclasts, the coating-incorporated BMP2 depot showed a sustained release.Conclusions: BMP2 were successfully incorporated onto and into the Bio-Oss^® Blocks. A sustained delivery of a lower concentration of BMP2 (μg-BMP2) from Bio-Oss^® Block was achieved in acidic solution or with the mediation of osteoclasts.

Abstract: As alternative for alumina and zirconia implants, silicon nitride based ceramics are considered promising candidate due to its biocompatibility and mechanical properties. However, this materials exhibit a bioinert character, leading to clinical failures. To overcome this problem, a biomimetic coating of hydroxyapatite is proposed in this paper, so that the surface can be bioactive and, consequently, the osteointegration process can be enhanced. Silicon nitride samples were sintered with different additives (Y, La and Yb) and the surfaces before and after coating were characterized by diffuse reflectance infrared Fourier transformed (DRIFT), X ray diffraction (XRD) and scanning electron microscopy (SEM). The results showed that the surfaces of bioinert silicon nitride samples sintered with different additives could be transformed into bioactive by the formation of a hydroxyapatite layer through biomimetic process.

Abstract: The shark-skin effect motivated from the dermal surface morphology of sharks hastens the imitation and manufacture of the non-smooth drag reduction bionic coating based on shark skin. The fabrication of the bionic shark-skin coating with life-sized scale-like microstructure was presented in this paper. Using hot embossing technology, the direct micro replication of the microstructure on shark skin was investigated for the first time. Modeled after the shark skin sample, the negative structure was directly replicated and printed on PMMA flat plate in the hot embossing process, relied on which the bionic shark-skin coating made of silica gel was fabricated in the end. The preliminary experiment results indicate that this method is a high precision, high throughput, high efficiency and low cost way to fabricate bionic microstructure in micron and submicron scale with good repeatability and availability.

Abstract: The aim of this study was to investigate if it is possible to fast load hydroxyapatite with antibiotics and still obtain a slow but therapeutic release of drugs during several hours. Physical vapour deposition was used to coat commercially pure titanium with a layer of anatase TiO2. On top of this, a layer of hydroxyapatite was deposited using biomimetic precipitation. This hydroxyapatite coating was then soaked in solutions containing antibiotics for various amounts of times. The release rate of the antibiotics was measured in PBS during 22 hours. The released amount was compared with the results from an antimicrobial susceptibility test and proved to be sufficient to kill several ml of bacterial broth during the time of the release measurements. It was shown that the soaking time does not affect the release rate and the results suggest that it is possible to develop implants with the option to add antibiotics to their surface at the site of surgery by a simple soaking method.

Abstract: The osseointegration of porous titanium implants was evaluated in the present work. Implants were fabricated from ASTM grade 2 titanium by a powder metallurgy method. Part of these implants were submitted to chemical and thermal treatment in order to deposit a biomimetic coating, aiming to evaluate its influence on the osseointegration of the implants. The implants were characterized by Scanning Electron Microscopy (SEM), Electron Dispersive X-Ray Spectroscopy (EDS) and Raman Spectroscopy. Three coated and three control (uncoated) implants were surgically inserted into thirty albino rabbits’ left and right tibiae, respectively. Tibiae samples were submitted to histological and histomorphometric analyses, utilizing SEM, optical microscopy and mechanical tests. EDS results indicated calcium (Ca) and phosphorous (P) at the surface and Raman spectra exhibited an intense peak, characteristic of hydroxyapatite (HA). Bone neoformation was detected at the bone-implant interface and inside the pores, including the central ones. The mean bone neoformation percentage in the coated implants was statistically higher at 15 days, compared to 30 and 45 days. The mechanical tests showed that coated implants presented higher resistance to displacement, especially after 30 and 45 days.

Abstract: In order to improve implant-bone attachment, porous titanium has been used to achieve the ingrowth of bone tissue within the porous structure. Although this biomaterial has shown efficient bone adhesion for orthopedic and dental implants, the ideal surface must have chemical bonds at the implant-bone interface. In this work, samples of pure porous titanium were produced by powder metallurgy technique and submitted to biomimetic process in order to evaluate the material’s bioactivity and to enhance its osteoconductivity. The samples were immersed in modified simulated body fluid (mSBF) which induces the nucleation and growth of a calcium phosphate bioactive film and a chemical bond with titanium. SEM, EDX and FTIR analyses showed that a calcium phosphate deposition occurred without the need of pre-treatments to increase the surface bioactivity. As a result, this research revealed the potential for obtaining a bonelike apatite film on this porous titanium by biomimetic method.

Abstract: In this work, porous titanium samples processed by powder metallurgy and coated with biomimetic coatings, obtained during different periods of immersion in a simulated body fluid (SBF), were tested for corrosion resistance in a phosphate buffer solution (PBS). Uncoated samples were also tested for comparison. The corrosion resistance of both types of titanium samples was evaluated by electrochemical impedance spectroscopy and potentiodynamic polarisation curves. The electrochemical results indicated the formation of a surface film on the porous Ti samples with immersion in the SBF solution and this biomimetic film increased their corrosion resistance. This film helps osteointegration besides increasing corrosion resistance.

Abstract: Bone-like apatite coatings were prepared using a biomimetic method in a simulated body fluid (SBF). The effect of initial pH values on the surface morphology of biomimetic apatite coating was studied. The coatings were characterized using X-ray diffraction and environmental scanning electron microscope. It was revealed that the morphology of the biomimetic apatite coating could be tailored by manipulating the initial pH of the SBF solution.