Papers by Keyword: Bioactive Coatings

Abstract: The aim of this research is to develop a methodology to obtain bioactive coatings on Ti6Al4V substrates pretreated with NaOH 5M for 24 h, by an autocatalytic route using an acid bath. The autocatalytic bath was developed in order to produce bioactive coatings with a Ca/P molar ratio of 1.2 by dissolving the appropriate amounts of CaCl₂ and NaH₂PO₂ as precursors and C₄H₄Na₂O₄·6H₂O as a reducing agent in distilled water, at pH values of 5.5 and 6.0, temperatures of 80 and 90°C, and two immersion times of 60 and 180 min. It was observed that the thickness and morphology of the coating changed according to the processing conditions.

Abstract: The purpose of the present study was to evaluate the role of bioactive surface coating and geometric design of orthopedic implants. In return, a 3-dimensional model with a interconnected macroscopic por system (IMPS) was designed. The model was created by using the place holder method with titanium powder and ammonium bicarbonate. After sintering one group of the IMPS-model was penetrated with plasma to create hydophilic surface. The second group was coated with the biomaterial NanoBone and the third was an untreated controll group. All three groups were used for an experimental pilot study in rabbit femora to determine the osseointegration process after 4 and 12 weeks. The biomaterial coated group points an approximately 10 % higher bone to implant contact compared with the two other groups.

Abstract: A two-step, biomimetic approach was applied for the rapid deposition of octacalcium phosphate (OCP) coatings on zirconia ceramics (Y-TZP). In the first step, sintered zirconia discs were immersed into a supersaturated Ca-P solution with pH=7.4 (CPS1). In the second step, the substrates were transferred from the CPS1 to another Ca-P solution with a lower pH (CPS2). After 6 hours of immersion in the CPS2, a thick coating consisting of large OCP crystals was obtained. Afterwards, the coated substrates were subjected to a thermal treatment in order to improve the attachment of the coating to the substrate.

Abstract: The combined chemical-hydrothermal synthesis of TiO2 and CaTiO3 films on pure Ti substrates was examined with a focus on film crystallinity and surface morphology. Pure Ti disks were chemically treated with H2O2/ HNO3 aqueous solutions at 353 K for 20 min in order to form a TiO2 gel layer on the surfaces. The samples were then hydrothermally treated in an autoclave at 453 K for 12 h or 24 h. Anatase-type TiO2 and perovskite-type CaTiO3 films with high crystallinity were obtained upon treatment with distilled water or aqueous NH3 and aqueous Ca(OH)2, respectively. Uniform, crack-free films were obtained. The surfaces showed excellent attachment of osteoblast-like MC3T3E1 cells in an incipient stage. Furthermore, the cells showed satisfactory proliferation, though at a slightly lower rate than on Ti. In addition, the samples were immersed in SBF (Simulated Body Fluid), adjusted to 310 K. A light hydroxyapatite (HAp) precipitate was observed on the unmodified Ti surface after 6 days of immersion. In contrast, precipitation was observed only after 2 to 4 days on the present oxide films. Thus, these oxide films are non-toxic and enhance the deposition of HAp.

Abstract: Ceramic scaffolds, mechanically qualified, highly porous, non biodegradable and with bioactive coating have been manufactured. The aim of this study was evaluated mechanical and in vivo responses of the porous alumina scaffolds with bioactive coating. The bioactive coating was performed under vacuum with bio-glass (45S5®)) and hydroxyapatite (HAp). Alumina ceramics (Al2O3) are used for bone implants in function of the biocompatibility and the high mechanical reliability of this material. Unfavourably alumina is a bioinert material and bone ingrowths are hard to occur and any implant anchorage becomes difficult. To improve this, ceramic scaffold samples were made with porosity concentration around 75vol% and with average pores diameters around 190.0µm. They were mechanically characterized through macro and micro structural analyses and mechanical tests and biologically through cell culture tests with fibroblastic VERO cell line for cytotoxicity and animal experiments on tibiae rats – Rattus norvegiicus albinos – aiming histological and line scan analysis in order to check the scaffold-bone cellular interaction. Current results seem to suggest the promising properties of the bioactive coated alumina ceramic scaffolds tested. The concentration of 75vol% alumina showed to be the great alternative for an economical solution for porous alumina ceramic scaffolds related to the mechanical properties and bone integration.

Abstract: The objective of this study was to manufacture porous scaffolds with bioinert and bioactive materials to join mechanical properties and bony integration. Porous alumina ceramic matrices were produced using the slurry technique followed by isostatic pressing, leaching and sintering. Porous alumina samples presented 75.0vol% porosity and 52.27MPa of compressive strength. Bioglass/hydroxyapatite ceramic slurry was used as coating on alumina matrices. The infiltration was performed by dipping the alumina porous samples into bio-glass/hydroxyapatite ceramics slurry under vacuum and followed by sintering. The evaluation of the alumina ceramic scaffolds samples were made using EDX, mechanical and in vitro tests. For the in vitro tests, fibroblastic VERO cell line was employed. The porous alumina ceramic coated acquired a higher strength and more pronounced cell interaction than the non coated alumina scaffolds.

Abstract: Silicon substituted Hydroxyapatite coatings were prepared by Pulsed Laser Deposition from targets made of mixtures of Hydroxyapatite with Si powder at different concentrations. The properties of the Si-HA coatings with several degrees of Si substitution were analyzed by different techniques such as FTIR, XRD, XPS and solid-state NMR. It was found that the Si incorporation causes an amorphization of the structure together with a loss of carbonate groups. Furthermore, the Si atoms are incorporated in the form of SiO4 4- groups, and H(PO4)2- appears as the predominant phosphate group.

Abstract: Hydroxyapatite (HAP) was electrophoretically deposited on 316L stainless steel in order to promote a bioactive surface. The effect of dispersing media (water and acetone), applied voltage and the deposition time on the deposit weight and microstructure of the coatings was evaluated. The deposition time was varied in the range of 1 to 900 s for water suspensions and 0.5 to 180 s for acetone suspensions. Suspensions were prepared by using HAP powder with an average particle size of 1.5 μm at a concentration of 1 % by weight. The deposition was performed under a direct current (DC) field of 400 to 1000 V for acetone suspensions and 5 to 50 V for water suspensions. The coatings were analyzed using scanning electron microscopy. The amount of hydroxyapatite on the surface of the metallic substrate was evaluated by determining the difference in weight of the samples, before and after the electrophoretic process. The stabilization of HAP particles in water was achieved using 1 % by weight of Dispex N40TM and 0.001M KCl. Under this condition the zeta potential of HAP in water suspension was –28 mV. Non additive was required in acetone suspensions. Dense, homogeneous and crack-free coatings of sub-micron particles (0.63 mg/cm2) were obtained by applying 5 V during 60 s in water suspensions. Above a DC field of 5 V the hydrolysis of water seriously difficulties the coatings formation. Homogeneous and crack-free coatings of sub-micron particles (1.45 mg/cm2) were also obtained in acetone suspensions applying 400 to 1000 V during 5 s. Lower voltages were not used with acetone suspensions due to its high resistivity.

Abstract: Natural wollastonite was electrophoretically deposited on 316L stainless steel in order to promote a bioactive surface. The effect of the disperse media and the deposition time on the deposit weight and microstructure of the wollastonite coatings was evaluated. The disperse media were methanol, acetone, ethanol, propyl alcohol and the deposition time was in the range of 1 to 180 s. Suspensions were prepared by using wollastonite powder with a mean particle size of 2 μm at a concentration of 1 g/L. The deposition was performed under a DC field of 800 V. The coated substrates were sintered at temperatures ranging from 900 to 1050oC in air for 2 to 4 h. Dense, homogeneous and crack-free coatings were obtained by using methanol and acetone. No wollastonite coating was obtained by using ethanol at these processing conditions and few wollastonite particles were deposited on the metallic substrates by using propyl alcohol. The deposit weight increases as the deposition time is increased in all the cases.

Abstract: The bioactive properties of hydroxyapatite (HA) are well known in the implant industry and coatings of HA have been used to enhance the adhesion of living tissue to metal prostheses. Pulsed laser deposition (PLD) in a water vapour atmosphere is an appropriate method for the production of crystalline HA coatings. In this work the effect of RF plasma on thin films of HA grown by PLD at different substrate temperatures has been studied. The physicochemical properties of the films were studied by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and energy dispersive spectroscopy (EDS), showing that the incorporation of RF discharge in the deposition chamber can lead to changes in the crystallinity and deposition rate of the films but substrate temperature still plays the most important role.