SBF Solution Research Articles

Structural and biological evaluation of new chitosan membrane for dural closure

Objective: to study the structural and biological evaluation of chitin-chitosan based membrane for dura mater replacement. Materials and methods. Chitosan-based films were made out of 3% solution of chitosan for the research. We used 200, 500 and 700 kDa chitosan (deacetylation rate 80–90 %) to produce chitin-chitosan membrane by using solvent evaporation method. For enhancing mechanical properties and reducing the degradation, chitin particles were added to the chitosan solution. Chitosan and chitin ratio was 80/20. The chitin/chitosan solution in Petri dishes was dried out during 3 days at room temperature. To obtain information about the structure of membrane surface and cross-section scanning, electron microscopy was performed. Hydrolytic degradation was studied by pouring into SBF solution. To determine the rate of enzymatic degradation, trypsin solution was used. To determine the mass loss percentage, we measured the sample weight after 7, 14, 21, 30 and 60 days after being in the appropriate solutions. Relative elongation and strength were measured by digital dynamometer to study membranes mechanical properties such as the strength and elasticity. MLO-A5 cells were used to assess biocompatibility of new materials. Results. Macroscopic view of obtained samples has shown their relative transparency with impregnation of chitin particle that elevated over the membrane surface without any diversity between different chitosan molecular weight samples. Due to scanning electron microscopy, principal diversity between the samples of different molecular weight has being seen: rough pore surface at 200 and 500 kDa and flat with minimal roughness surface of 700 kDa membranes. Cross-section of 500 and 700 kDa membranes are dense with no pores, but 200 kDa membrane are sponge like and it can be prediction for fluid sorption and cell migration during healing process. Chitin-chitosan membranes are biocompatible and degrade in aqueous and enzymatic solutions. Due to polysaccharide nature of chitosan and chitin, enzymatic degradation has shown higher trend compare to the hydrolytic ones. 200 kDa membrane degrades faster with final mass loss 83.2 % and completely due to porous structure that allows fluid sorption. Membrane mechanical parameters strongly depend on their structure. 200 kDa membrane has shown 2-fold higher elongation compared to 500 kDa and 3-fold — compared to 700 kDa ones. The compensation of mechanical forces ensured by porous structure is better than in dense ones. Tensile strength was in 2-fold better in 200 kDa membranes than in 500 and 700 kDa ones. Cell culture experiment has shown the better adhesion at the 3 rd day for 200 kDa membrane and minimal cell adhesion for 700 kDa membrane, probably due to smooth surface. The reduction rate between all samples and PCT control differ a lot, except for 200 kDa membrane that has the same proliferation rate as TCP. Conclusion. Chitin-chitosan membranes, made from different molecular weight chitosan, are transparent and has appropriate structure for being used as a dura mater substitute. They are biocompatible and degrade in aqueous and enzymatic solutions. Due to porous structure, excellent mechanical properties as well as better cell adhesion and proliferation, 200 kDa chitosan membrane is more applicable for neurosurgical issues.

Study on the inflammatory response of PMMA/polystyrene/silica nanocomposite membranes for drug delivery and dental applications.

BackgroundThe application of polymeric materials in medical industry has grown drastically in the last two decades due to their various advantages compared to existing materials. The present research work emphases on the sol-gel technique to formulate the polymethyl methyl acrylate/polystyrene/silica composite membrane.MethodsThe characteristic of the composite was investigated through modern state art of instrumentation.ResultsThe functional groups attached to the polymer was absorbed by FTIR. The FTIR spectrum confirm that the blend was mixed thoroughly and the formation of unite intimately between the polymers. The membranes were observed by SEM for its surface homogeneity which depends upon the composition of the two blending polymers. The captured SEM images showed the formation of microcracks on the surface, which was evidently controlled by varying the constituent polymer ratios. The prepared blend membranes with 2:1 ratio of PMMA/PS/Si displayed higher water uptake compared to other blended membranes. The composite membranes had good hydroxyl apatite growth in SBF solution. Furthermore, the in vitro cytotoxicity studies carried out by MTT method, using RAW macrophage cells showed that all the samples exhibited excellent cell viability.ConclusionThe inflammatory response of composite with equal concentration of PMMA-PS were performed and observed no inflammation in comparison with control and other tested concentrations.

Use of Materials Based on Polymeric Silica as Bone-Targeted Drug Delivery Systems for Metronidazole.

Mesostructured ordered silica-based materials are the promising candidates for local drug delivery systems in bone disease due to their uniform pore size and distribution, and high surface area which affect their excellent adsorption properties, good biocompatibility and bioactivity, and versatile functionalization so that their properties can be controlled. Ordered mesoporous silica (MCM-41 type) was synthesized by a surfactant-assisted sol-gel process using tetraethoxysilane as a silica precursor and hexadecyltrimethylammonium bromide as the structure-directing agent. Functionalized silica materials containing various types of organic groups (3-aminopropyl, 3-mercaptopropyl, or 3-glycidyloxypropyl groups) were synthesized by the post-grafting method onto pre-made mesoporous silica. Comparative studies of their structural characteristics, the surface mineralization activity and release properties for the model drug Metronidazole (MT) were then conducted. It has been found that porosity parameters, mineralization activity and adsorption/release of metronidazole from mesoporous channels of silica can be regulated using functional groups which are chemically bounded with an outer silica surface. The preferential mineral nucleation was found on negatively charged surfaces—MCM-41, and mercaptopropyl and glycidyloxypropyl functionalized silica (MCM-SH and MCM-epoxy, respectively) in simulated body fluid (SBF solution), as well as a sustained release of MT. In contrast to them, aminopropyl-functionalized samples (MCM-NH2) achieved a high MT release rate. These results confirm the potential of silica-based materials for local therapeutic applications (as drug carriers and bone substitutes) in bone disease.

The effect of steel ball diameter variation in dry shot peening process on surface roughness and corrosion rate of AISI 316L implant material

Stainless steel, or also called as inox steel is a material that has a resistivity to the oxide reaction in an oxygen-containing environment. This study uses AISI 316L stainless steel material which is a biomedical implant as a raw material that obtains surface modification technique to obtain new mechanical properties. Surface modification technique uses dry shot peening process by varying steel ball diameter as an abrasive material shot on the surface of steel ball at high speed. The steel ball used is AISI 440 C type with a hardness level of HRC 50-55. The results show that the level of material surface roughness will decrease along with the increasing (bigger) size of steel ball diameter used. The results of corrosion test on SBF solution (simulated body fluid) show an increase in corrosion resistance along with the decreasing (smaller) size of steel ball diameter used.

Assessment of phase stability and in vitro biological properties of hydroxyapatite coatings composed of hexagonal rods

We describe fabrication of hydroxyapatite coatings consisting of micrometric hexagonal crystals on titanium substrate. The aim was to evaluate their phase stability and in vitro performance. We employed a facile hydrothermal method assisted with a chelating agent and monoethanolamine as regulators of the nucleation and crystal growth. After the hydrothermal reaction, the hydroxyapatite coatings were sintered at different temperatures up to 950 °C. We performed in-depth investigations into the coating surface morphology, topography, wettability, and chemical composition using scanning electron microscopy, profilometry, sessile drop technique, x-ray diffraction and Raman spectroscopy. We assessed the bioactivity of hydroxyapatite structure sintered at different temperatures after incubation in the SBF solution. Simultaneously, we conducted a series of in vitro experiments based on MTT assay using MC3T3 mouse preosteoblast cell line to study the cytocompatibility of synthesized specimens. The results show that the thermal processing of hydroxyapatite coatings leads to their thermal decomposition to β-TCP phase already at 700 °C. As the heat treatment progresses, the edges of hexagonal crystals are melting and smoothing. We show that while as-prepared hydroxyapatite coating exhibits remarkable bioactivity after just 3 days, the sintered samples are not bioactive at all. Biological examination with MC3T3 cells indicates good compatibility of all coatings, with cell proliferation being enhanced on samples heated at higher temperatures. In conclusion, the heat treated HAp coatings with different morphologies and different HAp/β-TCP phase ratios influence the in vitro bioactivity and response of preosteoblast cells.

Bactericidal abilities and in vitro properties of diamond-like carbon films deposited onto MAO-treated titanium

The present work is focused on the antibacterial potentials, tribological properties and corrosion resistances of silver (Ag) or nitrogen (N)-doped diamond-like carbon (DLC) films deposited by a hybrid ion beam deposition system onto titanium substrates that were pretreated by micro arc oxidation (MAO). The results revealed that the DLC and N-DLC films had remarkable sealing effects on the porous MAO-coated substrate. Although the MAO/(Ag:N)-DLC coating still presented porous features, it had the lowest average wear rate of all the samples (4.40 × 10−16 m3/N·m) in an SBF solution and eradicated 100% of the E. coli bacteria. The corrosion current density (1.06 × 10−10 A/cm2) of the MAO/DLC coating was two orders of magnitude greater than that of the other three coatings. It can be speculated that doped DLC films deposited onto MAO-coated substrates could significantly reduce the risk of the titanium implant.

Synthesizing and comparing HA–TiO2 and HA–ZrO2 nanocomposite coatings on 316 stainless steel

In this research, hydroxyapatite coating and composite hydroxyapatite coatings containing nanoparticles were fabricated using a single step electrodeposition method. To investigate the effect of compositing agent type on hydroxyapatite structure, two different compounds (titania and zirconia) were used. Each compound was used at two different concentrations to observe the effect of compositing agent content on matrix structure. Pure hydroxyapatite was deposited with a water based Calcium–Phosphate (Ca–P) solution with pH = 4.2. To deposit composite coatings, a merged solution was prepared by merging Ca–P solution with aqueous TiO2 (ZrO2) suspension. Prepared coatings were analyzed using thickness measurement, XRD, FTIR, FESEM, polarization test and immersion in SBF solution. In the first step, XRD, FTIR and FESEM results proved the formation of hydroxyapatite using Ca–P solution and analysis of composite coatings proves the existence of nanoparticles in the coatings as compositing agent and the coating procedure was successful. Thereafter, polarization and immersion results indicate that composite coatings show superior properties than pure hydroxyapatite. The properties of hydroxyapatite matrix are influenced not only by the type of the compositing agent but also by the content of the additive. Adding nanoparticles changes different characteristics of pure HA, such as (1) decreasing the thickness of the coating, pure hydroxyapatite was 5.5 µm and the thickness of HA–ZrO2 (ZrO2: 6 mM = HZ2) composite coating was 4.4 µm; (2) increasing the crystallinity (Xc), Xc for HZ2 coating is 86% and Xc for pure HA is 80%; (3) obvious changes in morphology has occurred and new morphologies of HA are observed which has not been mentioned in the literature previously; (4) composite coatings have more positive Ecorr than pure HA, Ecorr. of HZ2 coating is − 0.23 which is the most positive one and Ecorr. of HA is − 0.41; (5) composite coatings have smaller porosity ratio than pure HA; (6) Pure and composite coatings are bioactive, but composite coatings show different bioactivity behavior.

Electrochemical properties and bioactivity of hydroxyapatite coatings prepared by MEA/EDTA double-regulated hydrothermal synthesis

In this study, we develop hydroxyapatite coatings that consist of micrometric hexagonal crystals grown on the Ti/TiO2 substrate. The coatings are synthesized by a hydrothermal method. The advance of our hydrothermal approach lies in the concomitant use of two reagents: ethylenediamine tetraacetic acid and monoethanolamine. The phase identification, surface morphology, and elemental composition of structures are examined by x-ray diffraction, Raman spectroscopy, scanning electron microscopy and energy dispersive x-ray spectroscopy. We also assess the in vitro bioactivity of hydroxyapatite structure and uncoated materials after incubation in the SBF solution. Simultaneously, we conduct a series of experiments to investigate electrochemical properties of titanium with and without hydroxyapatite by the means of electrochemical impedance and potentiodynamic polarization experiments in the Ringer's solution. Our results show that monoethanolamine-assisted hydrothermal method is an efficient and promising approach to obtain hydroxyapatite coatings with excellent crystal quality and Ca/P ratio close to the stoichiometric value of the Ca10(PO4)6(OH)2 phase. The SBF immersion tests indicate high bioactivity of hydroxyapatite coating after 7 days of incubation. However, the hydroxyapatite coating does not improve the corrosion behavior of the metallic titanium substrate. Electrochemical studies of all structures show the highest corrosion resistance for the Ti/TiO2 surface as compared to other samples. The lowest value of corrosion current density (jcor = 0.65 ± 0.19 nA cm−2) is found for the Ti/TiO2 surface. This result could be attributed to the porous morphology of the hydroxyapatite layer which could favor direct flow of electrolyte between the corrosive medium and the titanium substrate or to the adverse effect of hydrothermal synthesis on the barrier properties of the TiO2 intermediate layer.

Microstructure, adhesion, in vitro corrosion resistance and tribological behavior of (Si:N)-DLC coated pure Ti

(Si:N)-DLC, Si/(Si:N)-DLC, Si3N4/(Si:N)-DLC and Si/Si3N4/(Si:N)-DLC four films were deposited on the pure Ti substrates, using a hybrid ion beam deposition system consisting of a DC magnetron sputtering and linear anode-layer ion sources, to improve the adhesion and in vitro protective performance. The microstructures and thicknesses of the (Si:N)-DLC film with different interlayers were investigated by Raman spectroscopy, X-ray photoelectron spectroscopy, atomic force microscopy and scanning electron microscopy. The mechanical and adhesion properties were evaluated by indentation and scratch tests. The corrosion resistance and wear resistance of the coated pure Ti samples were characterized by electrochemical test and friction test in the SBF solution, respectively. The results showed that the (Si:N)-DLC film containing Si3N4 structure was obtained. This (Si:N)-DLC film interacted with the Si or Si3N4 interlayer, showing an obvious transition boundary, which resulted in an increasing binding force. As a result, the Si/Si3N4/(Si:N)-DLC film showed the highest critical loads. Furthermore, it was found that the Si/(Si:N)-DLC film had excellent in vitro corrosion resistance and tribological behavior in the SBF solution.

Deposition Hydroxyapatite /Titania Composite on Ti-6Al-7Nb Alloy for Human Body Implants

The microstructural analysis and electrochemical measurements tests were used to investigate the behaviors of (TiO2) and (HAp)-coated Ti-6Al-7Nb alloy in the SBF solution .By using RF sputtering, a thin TiO2 layer coated the substrate, while a thick layer of HAp coated the outer side of surface. The generated middle layer consist of the composite of TiO2 and HAp which is by AFM characterized as uniformly distributed coating system with nano size. The images of the scan electron microscopy (SEM) shows that there is no any cracking observed in the outer layer of tested samples due to the use of thin film TiO2 as mid lead to reduce the difference in the thermal expansion between the HAp material and Ti-6Al-7Nb substrate .The HAp upper layer significantly improve the bioactivity of the Ti-6Al-7Nb alloy. In this study, the bonding strength and the corrosion resistance was improved by using thin layer of TiO2. From electrochemical impedance spectroscopy (EIS) study Bod plot, the composite layer of TiO2 and HAp was suggested by the capacitive act as barrier layer coated substrate and prevent the relays of the ion from metallic. The results shows the values of Rox (309.2 k? cm2)are greater than for Rct(19.2 k? cm2), by assumes the presence oxide film increases for coated substrate are greater than that of uncoated, which is a result of the presence of coated film that improve the corrosion resistance of the sample.

Bioorthogonal surface modified α-TCP-based bone filler for enhancement of apatite formation and bioactivity

The aim of the present study was to investigate the effect of click chemistry reactants on morphology and physico-chemical properties of alpha tricalcium phosphate (α-TCP)-based powders. The powders were synthesized by solid-state reaction. The powders were modified with azide and cycloalkyne to form triazole as a consequence of reactions of these molecules. The presence of the band related to the triazole ring and the click molecules in powder structure was confirmed by Fourier transform infrared (FTIR) and Liquid chromatography- mass spectroscopy (LC-MS) analyses. Based on scanning electron microscopy (SEM) observations, the modified powder exhibited a different microstructure and morphology of apatite precipitates after one day and 7 days of soaking in distilled water and SBF solution, respectively, with respect to unmodified powder. According to the acellular in vitro test, X-ray diffraction (XRD) patterns represented triple characteristic peaks of hydroxyapatite (HA) in modified powder compared with control. Besides, the tendency of conversion of α-TCP to HA is more enhanced for modified powder as well. The SEM analysis depicted the plate-like and needle-like morphology of HA on the surface of modified and control powders, respectively. Since plate-like morphology of HA enhances bone generation and is found in trabecular bone, therefore, a future design can be considered for triazole-modified α-TCP-based fillers as good candidates for bone substitute application.

Synthesis of ternary bioactive glass derived aerogel and xerogel: study of their structure and bioactivity

Abstract In this work ternary bioactive glasses with the molar composition 63 % SiO2, 28 % CaO, and 9 % P2O5 have been prepared via sol-gel processing route leading to xerogel or aerogel glasses, depending on the drying conditions. Two types of drying methods were used: atmospheric pressure drying (evaporative), to produce xerogels, and supercritical fluids drying, to obtain aerogels. Both dried gels were subjected to heat-treatment at three different temperatures: 400, 600 and 800 ºC in order to the removal of synthesis byproducts and structural modifications. The resulting materials were characterized by X-ray diffraction (XRD), Fourier transforms infrared spectroscopy (FTIR), scanning electron microscopy (SEM), thermal gravimetric analysis (TGA) and differential thermal analysis (DTA), and by in vitro bioactivity tests in simulated body fluid. The influence of the drying and the sintering temperature of their structure, morphology, and bioactivity of the final products were evaluated. The results show a good bioactivity of xerogel and aerogel bioactive glass powders with the formation of an apatite layer after one day of immersion in SBF solution for aerogel bioactive glass powders and a particle size less than 10 nm. An apatite layer formed after 3 days in the case of xerogel bioactive glass powders and a particle size around 100 nm.

In vitro evaluation of the biocompatibility and bioactivity of plasma electrolyte oxidized titania/calcium phosphate nanocoatings on Ti

In this study, monolayer and two-layer composite coatings of titania and calcium phosphate were fabricated via plasma electrolyte oxidation technique on titanium substrates. The calcium phosphate layers were produced by using an electrolyte containing calcium acetate and β-glycerophosphate. In order to study and compare their biocompatibility and bioactivity properties MTT, cell adhesion, and soaking in SBF solution tests were performed on both coatings. According to the XPS and AFM analysis results, two-layer coatings have a higher Ca/P proportion on their surface and rougher surface. Higher cell proliferation rate was observed on two-layer specimen’s surface. An appropriate cell adhesion was observed in both coatings. Higher amount of hydroxyapatite (HAp) nanocrystals were observed on coatings with two-layer in comparison with monolayer after being soaked in SBF solution for 28 days. Besides, the proportion of HAp to calcium triphosphate after soaking in SBF solution was higher in two-layer coating.

Biomimetic Coating of a Titanium Substrate with Silicon-Substituted Hydroxyapatite

Silicon-substituted hydroxyapatite (Si-HA) materials have been synthesized from a model SBF solution with different concentrations of silicon ions. All of the samples prepared from an extracellular fluid solution at different concentrations of silicate ions have been shown to be single-phase and consist of hydroxyapatite. The nature of the silicon-containing reagent (Na2SiO3 or tetraethyl orthosilicate) has no effect on the structure of hydroxyapatite. Analysis of silicon-modified phosphate coatings on titanium substrates indicates that more complete Si-HA deposition occurs on etched samples during the first three days of holding in the model solution. After exposure of Si-HA-coated titanium substrates to a high-power ion beam, further crystal growth and surface regeneration are possible.

Degradation and In Vivo Response of Hydroxyapatite-Coated Mg Alloy

Nowadays there is a need for new generation of biodegradable implants, which should be able to stimulate the healing responses of injured tissues at the molecular level. Magnesium alloys attract great attention as perspective bone implants due to their biocompatibility, physical properties and ability to degrade completely under physiological conditions. The main purpose of this research was assessment of in vitro corrosion and surface morphology after short term in vivo implantation of Mg based implant covered by hydroxyapatite (HA). Mg alloys with the addition of Zr (0.65%), Al (1.85%) and Nd (1.25%) were used. In our work, we propose dipping method for hydroxyapatite coatings formation which has been shown to reduce the corrosion rate of magnesium implants in vivo. Simulated body fluid (SBF; pH 7.4) with ion concentrations approximately equal to those of human blood plasma resembling physiological conditions and citrate buffer with pH 5—simulating inflammation were selected as modelling environments for in vitro degradation test. The rod samples were implanted into the tibia bone of rats and after 1 day and 5 days of implantation were taken out to observe cells adhesion on surface samples. SEM was used to assess surface morphology after in vitro and in vivo tests. SBF solution causes some cracks on the surface of HA coatings, while citrate solution at pH 2 caused complete dissolving of the coating. The HA coating favoured cell adhesion and rapid fibrous tissue formation.

Mechanical and Bioactive Properties of Mullite Reinforced Pseudowollastonite Biocomposite

Bioactive composites consist of pseudowollastonite and mullite synthesized from natural resources was developed for bone implant applications. To realize such applications, a mechanical test of these composites and in vitro bioactivity in SBF solution were studied. The present paper reports pseudowollastonite synthesized from the rice husk ash and limestone reinforced with 10, 20 and 30 wt. % of mullite. Influence of sintering temperature, phase composition, morphology towards mechanical properties of various pseudowollastonite-mullite (PSW-M) composites was examined prior to the bioactivity test. It was found that pseudowollastonite with the addition of 20 wt. % of mullite sintered at 1150°C gave the best result for diametral tensile strength (DTS) and hardness with the value of 8.8 ± 0.15 MPa and 3.79 ± 0.13 GPa, respectively. The obvious increment in the mechanical strength was due to the formation of liquid phase CaAl2O3 during sintering at 1150°C. In addition, the formation of fibrous apatite (HA) layer of amorphous calcium phosphate (ACP) with Ca/P ratio 1.8 on PSW20M sample confirmed the good bioactivity of the composite.

Degradation behaviour of Mg-4Ag and Mg-5Gd alloys under in-vitro conditions and different time-frames

The Mg-4Ag and Mg-5Gd binary alloys' degradation and corrosion properties were studied under in-vitro conditions (in a SBF solution of pH 7.4 at 37 °C) by using various analytical techniques and time-frame windows (up to 3 vs. 28 days), and compared with the pure Mg alloy. Different kinetics and mechanisms of the alloys' degradation were identified, influencing their corrosion rates' dynamics.The Electrochemical Impedance Spectroscopy (EIS) measurements, being performed for up to 3 days, revealed that the corrosion of all three alloys are under a kinetic-controlled mechanism, among which only pure Mg and Mg-4Ag show a repassivation ability in this time-frame. However, the corrosion rates of binary alloys after 28 days of incubation reaching a value of around 0.33 mm/y and a release of 64 mg/L Mg2+ ions, that was accompanied by a pH change up to 8.3, an be lower compared to the pure Mg alloy (0.62 mm/y, 117 mg/L of Mg2+, pH of 9.0). While thick and homogenous layers of differently-shaped and chemically secondary-phased Mg(OH)2 products were identified on both binary alloys, MgO products and an apatite structure are formed on the pure Mg alloy surface. The Mg-4Ag alloy seems to be biomedically the most appropriate regarding the in-vitro degradation process.

Relationships between surface energy and charge of surface-modified titanium and HAp formation

Surface properties such as surface energy and surface charge are important for bone formation on a Ti surface. We investigated the relationship between surface properties (surface energy and surface charge) and initial Ca2+ and PO43− adsorption amounts on titanium surfaces modified with various functional groups (OH, NH2, SH, CH3, CH2CH, COOH). Surfaces with high surface energy and highly negative zeta potential, such as COOH and OH-modified Ti surfaces, exhibited high Ca2+ adsorption amounts. High surface energy, highly negative zeta potential, and an ideal stoichiometric Ca/P ratio during the initial adsorption of Ca2+ and PO43− led to the precipitation of HAp on COOH-modified Ti surfaces. On the other hand, the adsorption of HAp formed by homogeneous nucleation in the SBF solution occurs on the CH3 and CH2CH-modified Ti surfaces with low surface energy.

In vitro biocompatibility of new bioactive lithia-silica glass-ceramics

Glass-ceramics based on the Li2O-SiO2 system have been extensively used as restorative dental materials due to their excellent chemical durability, aesthetics, inertness in the buccal environment, and high fracture strength; but they are not bioactive. On the other hand, all known bioactive glasses show ability to bond to bone, teeth and cartilage coupled to osteoconduction and osteoinduction, but their fracture strength and toughness are rather low. The aim of this study is to develop and evaluate the in vitro biocompatibility of a new type of (bioactive and strong) lithia-silica glass-ceramic. For these purposes, two types of glass-ceramics based on a multicomponent lithia-silica system were studied: lithium metasilicate (LM) and lithium disilicate (LD). The in vitro bioactivity study was conducted in a SBF solution, before and after different times of immersion; the new materials were analyzed by XRD, FTIR, and SEM. Some samples were subjected to in vitro biodegradation tests to quantify the release of lithium and the weight loss. Cytotoxicity, adhesion, and cell proliferation on different samples were examined by using the Methyl Tetrazolium salt (MTS) and Alizarin Red. For ~40 vol% crystallinity, lithium metasilicate was detected as the major phase, whereas for ~80 vol% crystallinity, lithium disilicate was the major phase. The LD proved to be strong (3p-bending strength of 233 ± 12 MPa) and bioactive after 14 days of immersion in SBF. In terms of lithium ion release, the LD was outside the toxic range (>8.3 ppm). The LM and LD are not cytotoxic. The LD shows the best cellular adhesion and proliferation, leading to the formation of a mineralized matrix after 21 days. These results clearly suggest that the new LD brand is strong and highly biocompatible and warrants further study.

In vitro degradation and cytotoxicity of Mg-5Zn-0.3Ca/nHA biocomposites prepared by powder metallurgy

Abstract Mg-5Zn-0.3Ca/nHA biocomposites were prepared from pure Mg, Zn, Ca and nano-hydroxyapatite (nHA) powders by powder metallurgy method. The effect of various mass fractions of nHA (1%, 2.5%, 5%) as reinforcement on the corrosion properties of Mg-5Zn-0.3Ca alloy was investigated. The corrosion resistance of biocomposite samples was investigated by immersion tests and electrochemical techniques in SBF solution. The results showed that the corrosion resistance of Mg alloy was improved by adding 1% and 2.5% nHA. Bioactive nHA motivated the formation of stable phosphate and carbonate layers on surface and improved corrosion resistance of nanocomposites. However, addition of large contents of nHA in Mg alloy as reinforcement increased the density of this precipitated layer, so gases produced from localized corrosion were accumulated underneath this layer and decreased its adhesiveness and lowered its corrosion resistance. Indirect cytotoxicity evaluation for Mg alloy and its nanocomposites also showed that their extraction was not toxic and nanocomposite with 1% nHA indicated almost similar behavior as negative control.