Electrophoretic deposition of hyaluronic acid and composite films for biomedical applications

Hyaluronic acid (HYH) is a natural biopolymer, which has tremendous potential for various biomedical applications. Electrophoretic deposition (EPD) methods have been developed for the fabrication of HYH films and composites. New methods for the immobilization of drugs and proteins have been utilized for the fabrication of organic composites. Electrophoretic deposition enabled the fabrication of organic-inorganic composites containing bioceramics and bioglass in the HYH matrix. It was shown that the deposition yield, microstructure, and composition of the films can be controlled. Potential applications of EPD for the surface modification of biomedical implants and fabrication of biosensors are highlighted.     

Electrophoretic co-deposition of diamond/borosilicate glass composite coatings

Composite coatings made of diamond powders and borosilicate glass have been deposited on stainless steel substrates by electrophoretic co-deposition. Ethanol and acetone suspensions containing diamond powders of particle size 1-2 μm and borosilicate glass powders of size 0.1-0.5 μm were used. Electrophoretic deposition (EPD) parameters were optimized by a trial-and-error-approach. Microstructures of deposited and sintered coatings were investigated by XRD and SEM analysis. The results show that applied voltages up to 10 V led to thin and incomplete coatings. Voltages higher than 50 V resulted in uneven coatings with uncontrolled thickness and poor uniformity. The best results were achieved using ethanol suspensions. Smooth, uniform and dense coatings with diamond and glass particles distributed uniformly were obtained under applied voltages in the range of 30-50 V and a deposition time of 4 min. The concentration ratio of diamond to borosilicate glass in the composite coatings was in good correlation with the original ratio in suspension, thus control of the coating microstructure and composition is possible. During sintering at 900 °C, the glass particles softened; sintered by viscous flow and spread over the diamond particles surface. Thus a glass layer forms protecting the diamond from oxidization or graphitization and bonding the diamond particles together.     

Electrophoretic deposition of composite hydroxyapatite–chitosan–heparin coatings

Electrophoretic deposition method has been developed for the fabrication of organic–inorganic composite coatings for biomedical applications. The coatings were obtained as multilayer and functionally graded materials (FGM). Needle-shaped hydroxyapatite (HA) particles were prepared by a wet chemical method and used for the fabrication of chitosan–HA layers. The HA particles in the chitosan matrix showed preferred orientation of c-axis parallel to the substrate surface. Multilayer coatings were obtained, which contained pure chitosan layers and composite HA–chitosan layers. The thickness of the multilayer coatings was in the range of 2–100 μm. The thickness of the individual layers can be varied by the variation of deposition conditions. The feasibility of co-deposition of chitosan and heparin has been demonstrated. The proposed mechanism of heparin deposition is based on the use of non-stoichiometric chitosan–heparin complexes. The deposition yield and coating composition have been studied at various deposition conditions. The addition of heparin to chitosan solutions resulted in increasing deposition rate. Composite chitosan–heparin layers were used for the surface modification of HA–chitosan coatings. Obtained results pave the way for the electrophoretic fabrication of novel FGM coatings for biomedical implants with improved blood compatibility. The coatings were studied by X-ray diffraction analysis, thermogravimetric and differential thermal analysis, electron microscopy, and Fourier transform infrared spectroscopy.     

HA/Ti composite for biomedical application by mechanical milling

In order to overcome the poor mechanical properties of HA and the low bioactivity of Ti,HA/Ti composites with various compositions were prepared by mechanical milling.The effects of milling condition and the composition on the microstructure,the density and the hardness of the composites were studied.The results show that during the ball milling process.Ti particles are refined and the homogeneity of the HA/Ti mixtures is improved;HA will partially decompose due to the existence of Ti and high sintering temperature.The microstructure of HA/Ti composites is highly dependent on the milling condition and the composition.In the microstructure.Ti phase connects to be a continuous network,and HA/Ti mixtures disperse in the network.The longer the milling time,the finer the network will be.The density of HA/T composites decreases with the content of HA increasing and the milling time prolonging,because HA deteriorates the sinterability of Ti.The hardness of HA/Ti composites increases firstly with the content of HA increasing,and then drops when the content of HA exceeds 30%.Addition of HA will strengthen the HA/T composite but will decrease the density of the composite,which accounts for the effect of HA on the hardness of the composites.     

粉体粒度对HA/BG生物活性涂层组织结构的影响

采用亚音速火焰喷涂方法及涂层处理技术,以Ti6Al4V为基体喷涂不同粒度粉体,制备HA/BG生物活性涂层,并引入Ti/G过渡层缓解应力.涂层经700℃晶化处理.结果表明,粉体粒度决定了HA/BG涂层的组织结构.细小粉体可获得疏松、多孔结构的涂层,此种结构有利于涂层材料与骨组织之间结合.涂层经过700℃晶化处理后,主相为...     

Sol-gel derived HA/TiO2 double coatings on Ti scaffolds for orthopaedic applications

Hydroxyapatite/titania （HA/TiO2） double layers were coated onto Ti scaffolds throughout for orthopaedic applications by sol-gel method. Differential scanning calorimetry （DSC）, thermogravimetric analysis （TG） and X-ray diffractometry （XRD） were used for the characterisation of the phase transformations of the dried gels and coated surface structures. Scanning electron microscope （SEM） equipped with energy dispersive spectrometry （EDS） was used for the observation and evaluation of the morphology and phases of the surface layers and for the assessment of the in vitro tests. The in vitro assessments were performed by soaking the HA/TiO2 double coated samples into the simulated body fluid （SBF） for various periods. The TiO2 layer was coated by a dipping-coating method at a speed of 12 cm/min, followed by a heat treatment at 600 ℃ for 20 min. The HA layer was subsequently dipping-coated on the outer surface at the same speed and then heat-treated at difference temperatures. The results indicat that the HA phase begins to crystallize after a heat treatment at 560 ℃. The crystallinity increases obviously at 760 ℃. SEM observations find no delamination or crack at the interfaces of HA/TiO2 and TiO2/Ti. The HA/TiO2 coated Ti scaffolds displays excellent bone-like apatite forming ability when it is soaked into SBF. Ti scaffolds after HA/TiO2 double coatings can be anticipated as promising implant materials for orthopaedic applications     

Electrophoretic deposition of titanium/silicon-substituted hydroxyapatite composite coating and its interaction with bovine serum albumin

Silicon-substituted hydroxyapatite (Ca10(PO4)6-x(SiO4)x(OH)2-x, Si-HA) composite coatings on a bioactive titanium substrate were prepared by electrophoretic deposition technique with the addition of triethanolamine (TEA) to enhance the ionization degree of Si-HA suspension. The surface structure was characterized by XRD, SEM, XRF, EDS and FTIR. The bond strength of the coating was investigated. The results show that the depositing thickness and the images of Si-HA coating can be changed with the variation of deposition time. The XRD spectra of Ti/Si-HA coatings show the characteristic diffraction peaks of HA, and the incorporation of silicon changes the lattice parameter of the crystal. The FTIR spectra shows that the most notable effect of silicon substitution is the decrease of intensities of -OH and PO43- groups with the silicon contents increasing. XRD and EDS element analyses present that the content of silicon in the coating increases with increasing silicon concentration in the suspension. The bioactive TiO2 coating formed may improve the bond strength of the coatings. The interaction of Ti/Si-HA coating with BSA is much greater than that of Ti/HA coating, suggesting that the incorporation of silicon in HA is significant to improve the bioactive performance of HA.     

Preparation of poly-L-lactide/bioactive glass composite and evaluation of cytotoxicity in vitro

Bioactive and bioresorbable composite materials were fabricated from poly-L-lactide and bioactive glass （average particle size 6.8 μm） by a solvent evaporation technique. Cellular cultivation in vitro and MTT assay were conducted for evaluating the influence on morphology, growth and proliferation of cultured fibroblasts. The results of cytotoxicity testing show that cells cultured in extracts of PLLA/BG and on the surface of composites demonstrate normal growth and proliferation. The bioactive glass in PLLA composite facilitates both adhesion and proliferation of rat fibroblasts on PLLA/bioactive glass composite film.     

树脂基复合材料用陶瓷涂层防护性能分析

采用等离子喷涂铝粉作为打底材料在碳纤维增强聚酰亚胺复合材料（PMC）基体上制备了Al2O3和ZrO2轻质陶瓷防护涂层，测试了涂层的剪切结合强度、耐热循环性能、抗冲蚀性能、隔热性能。结果表明，等离子喷涂铝粉作打底层的涂层系统，性能优于电弧喷铝或电弧喷锌作打底层的涂层系统。带有Al2O3涂层的试样失重不到基体材料失重的1／3，Al2O3和ZrO2陶瓷涂层都可以为聚酰亚胺复合材料基体提供有效的冲蚀防护。Al2O3和ZrO2陶瓷涂层都可以为聚酰亚胺复合材料基体提供有效的隔热防护，ZrO2涂层隔热性能优于Al2O3涂层。     

电泳共沉积超细金刚石/玻璃复合涂层的研究

通过电泳共沉积技术制备超细金刚石/玻璃复合涂层,主要探讨了电泳沉积工艺及固化烧结条件对涂层的影响。超细金刚石粉体在乙醇溶液中荷负电,为阳极沉积。通过电流变化和形貌观察研究涂层沉积质量,结果表明:电压为30～50 V时,可以形成均匀平整的复合涂层。添加质量分数为0.05%～0.10%的金属阳离子能实现阴极沉积,避免了阳极腐蚀,有利于基板的选择。复合涂层最优固化烧结温度为450°C,反应时间为3 h,烧结后的涂层光滑致密且实现了金刚石在黏结相中的均匀分布。     

Bioactivity of bioresorbable composite based on bioactive glass and poly-L-lactide

Bioactive and bioresorbable composite was fabricated by a solvent evaporation technique using poly-L-lactide（PLLA） and bioactive glass （average particle size： 6.8μm）. Bioactive glass granules are homogeneously distributed in the composite with microcrack structure. The formation of hydroxyapatite（HA） on the composite in simulated body fluid（SBF） was analyzed by scanning electron microscopy（SEM）, energy dispersive spectroscopy（EDS）, X-ray diffraction（XRD）, and Raman spectra. Rod-like HA crystals deposit on the surface of PLLA/bioactive glass composite after soaking for 3 d. Both rod-like crystals and HA layer form on the surface for 14 d in SBF. The high bioactivity of PLLA/bioactive glass composite indicates the potential of materials for integration with bone.     

Properties and strengthening mechanism of brush plated nanoparticle reinforced composite coatings

Nanoparticle reinforced nickel matrix composite coatings, such as n-Al2O3/Ni, n-SiO2/Ni, n-SiC/Ni and n-TiO2/Ni, were fabricated by brush plating technique. Hardness, wear resistance and contact-fatigue resistance of the composite coatings were determined, and strengthening mechanism of the composite coatings was discussed. Results show that the composite coatings have superior properties to the Ni metal coating. Compared with properties of brush plated Ni metal coating, the composite coatings have hardness over 1.5 times and wear resistance capability of about 2.5 times. The strengthening mechanism of the composite coatings mainly includes fine-crystal grain effect, nanoparticle dispersion effect and dislocation effect.     

Electrochemical deposition of octacalcium phosphate micro-fiber/chitosan composite coatings on titanium substrates

Calcium phosphate/chitosan composites have been extensively studied as bone substitutes, tissue engineering scaffolds, or bone cements. In the present study, we have prepared octacalcium phosphate (OCP) micro-fiber/chitosan composite coatings through an electrochemical deposition method. OCP coatings with microporous structure, which are woven by micro-fibers with 20-30 μm in length and 0.1-1 μm in width, have a good ability to incorporate chitosan. This novel OCP micro-fiber/chitosan composite coating could have broad applications in the biomedical engineering.     

Electrical bistability of composite film comprising hyper-branched polymer and gold nanoparticle

A hyper-branched polymer (HPS) with dithiocarbamate (DC) end groups and gold nanoparticle stabilized by HPS (HPSAu) were synthesized. We fabricated a single-layered organic electrical bistable device (OBD). It exhibited a unipolar switching behavior with a negative differential resistance (NDR). When a certain voltage was applied to the pristine state, the device changed irreversibly and began exhibiting bistable conductive states; the equivalent circuit of this device is a parallel circuit comprising one resistance and one capacitor.     

反应电火花沉积TiN/Ti复合涂层机理与性能

利用DZ-1400型电火花沉积/堆焊机,以工业纯钛TA2为电极,以工业纯氮为保护气和反应气,在TCA钛合金表面上制备了TiN/Ti复合涂层.用SEM、XRD、AES等仪器对涂层、物相、微观结构、元素组成及界面行为进行分析,测定了涂层的显微硬度,利用自制磨损试验机对比了涂层与淬火回火65Mn的磨损性能.结果表明,TiN/Ti复合涂层与基体形成良好的冶金结合,涂层主要由钛和反应合成的TiN、Ti2N相组成,组织致密、均匀、连续,涂层平均显微硬度可达1390HV0.1,约是基体硬度的6.3倍,涂层耐磨性良好.     

An improved method for the deposition of corrosion-resistant aluminium coatings for aerospace applications

The gradual reduction in the use of electroplated cadmium as a corrosion barrier for aircraft parts has led to the development of ion- vapour-deposited (IVD) aluminium as an alternative. The most common IVD technique is the McDonnell Douglas “Ivadize” process, but the morphology of such aluminium coatings is usually open and columnar. Consequently, a post-deposition shot peen is used to densify the structure. This has led to very poor control over the thickness and uniformity of the coating, and precision parts cannot be coated by such techniques. The use of multimagnetron ion plating can guarantee close control over the coating dimensions by the precise deposition of fully dense aluminium films which do not require peening. To further improve the properties of the films, a series of aluminium alloys have been deposited to provide enhancement of the corrosion and tribological properties of the films.     

Electrochemical deposition of bioactive coatings on Ti and Ti-6Al-4V surfaces

Passivating coatings of brushite (CaHPO₄·2H₂O) were obtained on Ti and Ti-6Al-4V ELI alloy substrates by cathodic polarization. After soaking in Ringer's solution for 48 h brushite was transformed to hydroxyapatite (Ca₁₀(PO₄)₆(OH)₂) as confirmed by XRD, FT-IR and Raman spectroscopy. Electrochemical cyclic polarization curves of the coated biomaterials obtained in Ringer's solution at pH values of 7.1 and 8.91 as well as in Hank's Balanced Salt Solution (HBSS) at pH value of 7.4 show a nobler behavior than of the uncoated biomaterials. The coated biomaterials had lower corrosion rates than the uncoated biomaterials suggesting a protective character of the hydroxyapatite coating. Electrochemical impedance spectra (EIS) revealed capacitive behavior, owing to the protective, very resistant layer, the thickness of which increased with soaking time. The coated biomaterials presented higher electropositive open circuit potentials compared to the uncoated biomaterials as result of the protective effect of the coating. The morphology of the coatings changed with soaking time as the coatings became denser, smoother and better adhering. Hence such coatings may provide favorable structure for cell adhesion and proliferation.     

Al2O3-nanodiamond composite coatings with high durability and hydrophobicity prepared by aerosol deposition

We attempted the room-temperature fabrication of Al₂O₃-based nanodiamond (ND) composite coating films on glass substrates by an aerosol deposition (AD) process to improve the anti-scratch and anti-smudge properties of the films. Submicron Al₂O₃ powder capable of fabricating transparent hard coating films was used as a base material for the starting powders, and ND treated by 1H,1H,2H,2H-perfluorooctyltriethoxysilane (PFOTES) was added to the Al₂O₃ to increase the hydrophobicity and anti-wear properties. The ND powder treated by PFOTES was mixed with the Al₂O₃ powder by ball milling to ratios of 0.01 wt.%, 0.03 wt.%, and 0.05 wt.% ND. The water contact angle (CA) of the Al₂O₃-ND composite coating films was increased as the ND ratio increased, and the maximum water CA among all the films was 110°. In contrast to the water CA, the Al₂O₃-ND composite coating films showed low transmittance values of below 50% at a wavelength of 550 nm due to the strong agglomeration of ND. To prevent the agglomeration of ND, the starting powders were mixed by attrition milling. As a result, Al₂O₃-ND composite coating films were produced that showed high transmittance values of close to 80%, even though the starting powder included 1.0 wt.% ND. In addition, the Al₂O₃-ND composite coating films had a high water CA of 109° and superior anti-wear properties compared to those of glass substrates.     

Electrophoretic deposition of conjugated polymer: Deposition from dilute solution and PEDOT coating effect

It has been shown that the films of a soluble conjugated polymer poly[(9,9-dioctyl-2,7-divinylene fluorenylene)-alt-{2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylene}] for electronic devices can be prepared by the electrophoretic deposition with polymer suspensions derived from dilute polymer solutions which are so dilute that the conventional spin-coating technique is not applicable. For example, a 100 nm-thick film can be prepared on an indium-tin-oxide (ITO) electrode from a suspension from solution containing 0.1 g/l of the polymer. The thickness of the polymer film deposited is found to be almost proportional to the concentration of the polymer, and the linearity down to 5.0 × 10^?3 g/l is confirmed. On the other hand, it has been found that coating the ITO electrode with poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) salt results in low and nonlinear deposition rate.