Eliana Cristina da Silva Rigo

Bonelike Apatite Coating on Ti6A4V: Novel Nucleation Process Using Sodium Silicate Solution

Despite the well known biocompatibility and bioactivity of synthetic hydroxyapatite (HA), its use, as structural biomaterial has been limited because of intrinsic low mechanical properties. In order to avoid this problem, metallic implants are commonly coated with a thin HA layers. Among the various techniques used to produce coatings on metals, the biomimetic process has gained increasing attention in the last years. In this work, a metallic substrate (Ti6A14V) was coated using a variation of the traditional biomimetic method. The HA coatings were characterised by diffused reflectance spectroscopy (DRIFT) and scanning electron microscopy (SEM).

Biomimetic Method for Obtaining Hydroxyapatite

Coating of bioinerts or biotolerable materials with a bioactive layer, generally composed of hydroxyapatite (HA), has been currently used when one wishes to combine bioactivity and material properties. Coating methods include: plasma and flame spray, sputtering, electrophoresis and electrolysis. Except the electrolytic one, all other methods involve high working temperatures. Therefore, the physical and chemical characteristics of hydroxyapatite can be affected, with possible consequences on the behavior of the implanted material. A recently proposed method named biomimetic, can be employed to coat several types of substrates through precipitation of a hydroxyapatite layer. This approach imitates the biological natural conditions of hydroxyapatite formation, through control of temperature, pH and concentration of ionic species. In this work, barium titanate substracts were coated with hydroxyapatite and characterized by X-ray diffraction, infrared spectroscopy and scanning electron microscopy.

A Comparative Study of Biomimetic Coatings on Titanium and Stainless Steel

Titanium and stainless steel are examples of biomaterials widely used in dental and orthopedic implants owing to their properties of good corrosion resistance and excellent biocompatibility. This paper reports on a study of the biomimetic method applied to titanium (cp-Ti) and 316L stainless steel. The method consists in immersing the metal substrate in a synthetic solution of SBF (simulated body fluid) whose composition, pH and temperature resemble those of human blood plasma. The coating on the two metals was effective for obtaining hydroxyapatite, which was confirmed by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FTIR).

Corrosion Characterization of Titanium Alloys by Electrochemical Techniques in Artificial Saliva and SBF Solution

The commercially pure titanium (cp Ti) biocompatibility is due to its chemical stability in organism because of the presence of a fine film and impermeable of titanium oxide over the metal surface that confirms its corrosion resistance, changing this materials surface has been the direction of many research groups, these modifications may have influence in corrosion resistance. In this work was investigated the electrochemical behavior of cp Ti, without and with coating of the hydroxyapatite, commonly used implant materials, in artificial saliva and simulated body fluid (SBF) solution at 25oC and pH=7.4. The potentiodynamic polarization curves, shows that there is a passive region with low current’ density, indicating that in the investigated conditions the formation of a surface protective film occurs. In the studied conditions it was observed that hydroxyapatite layer has influence on corrosion resistance properties.

Evaluation of the antimicrobial activity and cytotoxic effect of hydroxyapatite containing Brazilian propolis

The aim of this work was to produce hydroxyapatite powder (HA) containing the dry extract of green and red propolis, and to evaluate the possible bactericidal activity of these materials over a short period of time through a fast release system. The ethanolic extracts of green and red propolis (EEP) were incorporated into the material by spray drying. After release tests, powders containing dry EEP were characterized regarding the content of total phenolics and flavonoids. Material characterization was undertaken by scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR). The antimicrobial activity was evaluated by plate colony counting, minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC) against Staphylococcus aureus (S. aureus). The cytotoxicity of the materials was determined by the neutral red incorporation method. The materials showed apparently spherical morphology, indicating a decrease in the degree of agglomeration with the addition of propolis. Characteristic HA and propolis functional groups were observed in the FTIR. The materials showed a higher release of phenolics and lower amounts of flavonoids when compared to the EEP, with the higher amounts of flavonoids observed for HA with red propolis. A bactericidal effect was observed for all materials within the interval of 0.5 and 1 h, showing lower inhibitory activity (MIC) and higher bactericidal activity (MBC) when compared to the EEP, with the best results attributed to HA with red propolis. The IC50 values (which is the concentration needed to inhibit cell growth by 50%) obtained from the cytotoxicity assay for HA with the green and red propolis lay between MIC and MCB. Considering these results, it is suggested that HA and propolis may be used as a possible antimicrobial agent, inhibiting the growth of S. aureus, although further in vivo biocompatibility should be investigated before using this material as a medical device with bactericidal potential.

Development and Characterization of Hydroxyapatite Containing Silver by Precipitation and Immersion Methods

The use of bone substitutes for recovery of lost function is a constant search within the medical field. So biomaterials have received a very large attention from the scientific community, including the materials the basis of calcium phosphate. Hydroxyapatite (HA) has been studied as apart from representing the natural constitution of the mass of bones and teeth in 30 to 70 %, has properties of bioactivity and osteoconductivity, encouraging and assisting the growth of bone tissue. In contrast, bacterial infections can arise after implantation causing the loss of functionality in the short and medium term. Several alternatives are being tested, usually associated with the use of conventional antibiotics incorporated into biomaterials. An alternative to antibiotics would be use such metals that possess antibacterial properties. Silver (Ag) is known as a bactericidal metal and so gained a prominent place among the studies as an important ally in the control of post-surgical infections. This work aimed to synthesize, characterize and evaluate the antimicrobial effect of the addition of silver ions into hydroxyapatite. The hydroxyapatites containing silver were obtained by the precipitation method in aqueous solution containing AgNO3 and by immersing the powder after the precipitation process in aqueous solutions containing AgNO3. At this stage of the work, were analyzed and characterized the crystalline phases and the ionic groups present in HA, HA precipitates with Ag and immersed in a solution of Ag. X-ray diffraction (XRD) spectra showed that regardless of the method used, precipitation (room temperature or 90°C) or by immersion, the metallic Ag was present in the structure of HA. Additionally, it was observed that the peaks indicated in the XRD pattern for HA corresponding to the diffraction pattern of plugs JPCDS 09-0432 (Joint Committee on Powder Diffraction Standards). No peaks related to the phases being observed β-TCP and CaO, respectively, indicating that the conditions adopted for obtaining HA Ag, only HA phase is present and that methods, precipitation and immersion are efficient to occur doping of HA with Ag

Evaluation of the Apatite Coating on Silicon Nitride Based Ceramics Sintered with Re2O3 Additives (Re = Y, La, Yb)

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.

Hydroxyapatite Nucleation on Modified Silicon Surface for Use in Biosensors

In this work, we explore the deposition of single-phase and uniform HA coatings on a crystalline silicon surface of microelectronic quality. The used methodology includes an NaOH treatment to produce the silanization of Si surface and a modified biomimetic technique, using sodium silicate solution (SS) as nucleant agent, for apatite-based coating formation. The sodium silicate solution (SS) demonstrated to be effective for the calcium phosphate layer formation, but the treatment can reduce the induction to obtain a uniform surface coating of HA. This suggests that, among the factors that determine nucleation of calcium phosphate on silicon, surface electrical charge could play a key role.