Immersion In Simulated Body Fluid Solution Research Articles

Structural Parameters and Behavior in Simulated Body Fluid of High Entropy Alloy Thin Films.

The structure, composition and corrosion properties of thin films synthesized using the Pulsed Laser Deposition (PLD) technique starting from a three high entropy alloy (HEA) AlCoCrFeNix produced by vacuum arc remelting (VAR) method were investigated. The depositions were performed at room temperature on Si and mirror-like polished Ti substrates either under residual vacuum (low 10-7 mbar, films denoted HEA2, HEA6, and HEA10, which were grown from targets with Ni concentration molar ratio, x, equal to 0.4, 1.2, and 2.0, respectively) or under N2 (10-4 mbar, films denoted HEN2, HEN6, and HEN10 for the same Ni concentration molar ratios). The deposited films' structures, investigated using Grazing Incidence X-ray Diffraction, showed the presence of face-centered cubic and body-centered cubic phases, while their surface morphology, investigated using scanning electron microscopy, exhibited a smooth surface with micrometer size droplets. The mass density and thickness were obtained from simulations of acquired X-ray reflectivity curves. The films' elemental composition, estimated using the energy dispersion X-ray spectroscopy, was quite close to that of the targets used. X-ray Photoelectron Spectroscopy investigation showed that films deposited under a N2 atmosphere contained several percentages of N atoms in metallic nitride compounds. The electrochemical behavior of films under simulated body fluid (SBF) conditions was investigated by Open Circuit Potential (OCP) and Electrochemical Impedance Spectroscopy measurements. The measured OCP values increased over time, implying that a passive layer was formed on the surface of the films. It was observed that all films started to passivate in SBF solution, with the HEN6 film exhibiting the highest increase. The highest repassivation potential was exhibited by the same film, implying that it had the highest stability range of all analyzed films. Impedance measurements indicated high corrosion resistance values for HEA2, HEA6, and HEN6 samples. Much lower resistances were found for HEN10 and HEN2. Overall, HEN6 films exhibited the best corrosion behavior among the investigated films. It was noticed that for 24 h of immersion in SBF solution, this film was also a physical barrier to the corrosion process, not only a chemical one.

Fabrication and characterization of polyvinyl alcohol/TiO2 membrane immersed in simulated body fluid for biomedical application

AbstractIn this study, we synthesized hydroxyapatite (HA) on polyvinyl alcohol/TiO2 (PVA/TiO2) in which TiO2 was prepared by the sol‐gel method. HA was formed by immersing the membrane in the simulated body fluid (SBF) solution. We improved the mechanical strength of the membranes by adding glutaraldehyde (GA) combining with heat treatment to cross‐link the polymer network. In addition, the composition of TiO2 crystalline phase, TiO2 content in each membrane, and the duration of membrane immersion in SBF solution were investigated. The morphological structures of hydroxyapatite/polyvinyl alcohol/TiO2 (HA/PVA/TiO2) membranes were characterized by IR, SEM, and XRD. We confirmed that the HA formation depended on the TiO2 content and phase composition (rutile or anatase). Membranes containing TiO2 rutile‐phase showed more pronounced HA formation than membranes containing TiO2 anatase‐phase. The appearance of HA also depended on SBF immersion duration. Membranes soaked for 3 weeks showed significantly more HA formation than membranes soaked for 1 and 2 weeks. Furthermore, the number of cells in membranes soaked for 3 weeks was clearly higher than in other membranes. Finally, HA/PVA/TiO2 membranes containing 25 wt.% of TiO2 rutile‐phase are biocompatible based on the number of viable cells and thus have the potential for biomedical application.

Novel synthesis of BCP cotton-wool-like nanofibrous scaffolds by air-heated solution blow spinning (A-HSBS) technique

Biphasic calcium phosphate (BCP) cotton-wool-like nanofibrous scaffolds are very interesting materials for tissue engineering. Air-heated solution blow spinning (A-HSBS) was a simple and novel strategy developed in this work to obtain this structure. Precursor solutions of calcium nitrate, triethyl phosphate, and polyvinylpyrrolidone (spinning agent) dissolved in water and ethanol were used. The scaffolds were calcined at 800 °C. Part of the samples was stored under restricted atmospheric conditions, while the other part was exposed to ambient conditions for 7 days. The scaffolds were characterized by thermogravimetric analysis, X-ray diffraction, Fourier transform infrared spectroscopy, and scanning electron microscopy. In vitro assays were performed using simulated body fluid (SBF) and phosphate-buffered saline (PBS) solutions. Results showed the formation of scaffolds constituted by intertwined nanometric fibers. XRD patterns indicated the formation of BCP and CaO. For the sample exposed to air, CaCO3 was formed from the conversion of CaO with atmospheric CO2, producing BCP/CaCO3. After 7 days of immersion in SBF solution, the formation of a homogeneous layer of apatite was more evident on the surface of the BCP/CaCO3 than on the BCP nanofibers. The biodegradability in PBS medium, after 14 days of immersion, showed a mass loss of 21% (pH of 8.3) and 14% for the BCP and BCP/CaCO3 scaffolds (pH of 7.8), respectively. BCP nanofibrous scaffolds can be considered promising candidates for use in bone tissue engineering applications.

Optical, structural and physical properties of fluoride doped bioactive glasses

Glasses of composition (60–x)NaPO3-25B2O3-xCaF2-15MgO, where x = 2.5, 5, 7.5, 10 and 12.5 mol% were synthesized by melt quench method at 1100 °C. The X ray diffractogram (XRD) of glass samples reveals their amorphous nature. Density of synthesized samples was found to increase when CaF2 composition varied from 2.5 to 12.5 mol%. UV visible absorption spectra of the samples show broad absorption band at nearly about 215 nm. The optical band gaps were estimated from the optical absorption spectra by using Tauc plots. An increase of band gap energies was observed due to the creation of ionic cross-links within the glass structure. The various other parameters like calcium ion concentration, polaron radius, internuclear distance and optical basicity values were calculated using the refractive index and density of glasses. For in vitro studies, the glasses were soaked in Simulated Body Fluid (SBF) solution for 14 days. The XRD and Infrared (IR) studies carried out on samples post immersion in SBF solution for 14 days have revealed the formation of hydroxyapatite layer.

Synthesis and electrophoretic deposition of TiO2-SiO2 composite nanoparticles on stainless steel substrate

Titanium dioxide-silica composite nanoparticles were synthesized through a verified Stöber sol-gel method. The resultant nanoparticles, which consisted of titanium dioxide cores (35.54 ± 4.4 nm length rods) surrounded by ultrafine silica particles (3.22 ± 0.63 nm spheres) forming a thin shell, were electrophoretically deposited on an anodized stainless steel substrate to enhance its biological response in simulated body fluid (SBF). The presence of silica shell on TiO2 cores increased the surface roughness of the resultant composite particles and eliminated the cracks observed in the TiO2 coating due to the higher cohesion between the particles. The tape test results confirmed the higher adhesion of TiO2-SiO2 coating to the substrate. After 7 days of immersion in SBF solution, the silica shell resulted in a significantly higher Ca-P cluster formation on the TiO2-SiO2 coating compared to the TiO2 coating, which was almost free of Ca-P deposit. As the cracks were eliminated on the surface of the TiO2-SiO2 coating, the barrier performance of this coating was enhanced compared to the TiO2 coating in a phosphate-buffered saline solution.

Equisetum hyemale-derived unprecedented bioactive composite for hard and soft tissues engineering

Although Bioactive Glasses (BGs) have been progressively optimized, their preparation often still involves the use of toxic reagents and high calcination temperatures to remove organic solvents. In the present work, these synthesis related drawbacks were overcome by treating the ashes from the Equisetum hyemale plant in an ethanol/water solution to develop a bioactive composite [glass/carbon (BG-Carb)]. The BG-Carb was characterized by scanning electron microscopy, and transmission electron microscopy; and its chemical composition was assessed by inductively coupled plasma-optical emission spectroscopy. Brunauer–Emmett–Teller gas adsorption analysis showed a specific surface area of 121 m2 g−1. The formation of hydroxyapatite (HA) surface layer in vitro was confirmed by Fourier-transform infrared spectroscopy analysis before and after immersion in simulated body fluid (SBF) solution. The Rietveld refinement of the XRD patterns and selected area electron diffraction analyses confirmed HA in the sample even before immersing it in SBF solution. However, stronger evidences of the presence of HA were observed after immersion in SBF solution due to the surface mineralization. The BG-Carb samples showed no cytotoxicity on MC3T3-E1 cells and osteo-differentiation capacity similar to the positive control. Altogether, the BG-Carb material data reveals a promising plant waste-based candidate for hard and soft tissue engineering.

In Vitro Studies and Evaluation of Antibacterial Properties of Biodegradable Bone Joints Based on PLA/PCL/HA

Background: Due to the history of using permanent implants and the ability of adaptations of polymers to physiological environments such as the body environment, the need to design a polymer implant with a new formulation for orthopedic applications was felt. Methods: Polymer joints in this study were made by solvent casting method. The mechanical properties of the samples were investigated by bending tests, before and after immersion in simulated body fluid (SBF). Morphology of nanocomposites, bioactivity of samples and initiation of degradation process were performed by field emission scanning electron microscope (FESEM). Toxicity test was performed to evaluate the toxicity of nanocomposites. The antibacterial properties of the samples were investigated by examining the zone of inhibition and measuring the photometric concentration. Biodegradability test was performed to prove the biodegradability of polymer joints. Results: It was found that the mechanical properties of nanostructures increased with the addition of nanoparticles. Also, the presence of oxide and graphene nanoparticles affected the antibacterial properties of the composite nanostructure. Immersion in SBF solution showed that the nanostructures were biodegradable and bioactive. The results of this study indicate that the optimal nanocomposite PLA-PCL-HA-1% ZNO-1% GR has a Young’s modulus close to spongy bone and reduces the stress shielding phenomenon. The flexural Yang modulus of the PLA-PCL-HA nanocomposite was 2139.037 ± 381.312 MPa. The presence of zinc oxide and graphene nanoparticles increased the Young’s modulus to 4363.636 ± 127.498 MPa. The optimal sample has the necessary lethality against two strains of gram-positive and gram-negative bacteria and due to its bioactivity is a suitable option for use in spongy bone tissue. In this study, the viability of fibroblast cells in the vicinity of the polymer matrix versus the optimal matrix increased from 22.14 ± 0.623 to 82.96 ± 1.101% after 72 hours. Conclusions: Improving cell viability indicates a reduction in the optimal matrix toxicity compared to the polymer matrix.

The Effect of Liquid Phase Concentration on the Setting Time and Compressive Strength of Hydroxyapatite/Bioglass Composite Cement.

Composite scaffolds of hydroxyapatite (HAp) nanoparticles and bioactive glass (BG) have been applied as appropriate materials for bone tissue engineering. In this study, hydroxyapatite/bioglass cement in different ratios was successfully fabricated. To prepare HAp and HAp/BG cement, synthesized HAp and HAp/BG powder were mixed in several ratios, using different concentrations of sodium hydrogen phosphate (SP) and water as the liquid phase. The liquid to powder ratio used was 0.4 mL/g. The results showed that setting time increased with BG content in the composite. The results also showed that with the addition of bioglass to the HAp structure, the density decreased and the porosity increased. It was also found that after immersion in simulated body fluid (SBF) solution, the compressive strength of the HAp and HAp/BG cements increased with BG concentration up to 30 wt.%. SEM results showed the formation of an apatite layer in all selected samples after immersion in SBF solution. At 30 wt.% BG, greater nucleation and growth of the apatite layer were observed, resulting in higher bioactivity than pure HAp and HAp/BG in other ratios.

Design of multilayer hybrid sol-gel coatings with bifunctional barrier-bioactive response on the Elektron 21 magnesium alloy for biomedical applications

The present study aims to develop multilayer barrier-bioactive hybrid sol-gel coatings from a mixture of the silane precursors tetraethylorthosilicate (TEOS) and glycidoxypropyltriethoxysilane (GPTMS) deposited on the Elektron 21 magnesium alloy. The purpose of the inner layer (barrier coating) was to provide corrosion protection to the magnesium alloy, whereas the outer layer (bioactive coating) was doped with different Ca and Mg contents to produce a bioactive material. The coatings were characterised using scanning electron microscopy (SEM) and their corrosion behaviour was evaluated by anodic polarisation and electrochemical impedance spectroscopy after immersion in simulated body fluid (SBF) at 37 ± 0.5 °C. The experimental results showed that the multilayer coatings increased the corrosion resistance of the alloy up to three orders of magnitude during immersion in SBF solution. On the other hand, the presence of Ca and Mg in the bioactive coating promoted the growth of apatite-like phases. However, an increment of salt content favoured the formation of porous coatings, which allowed the access of the electrolyte to the substrate leading to their rapid deterioration. Despite the latter, this research endorses the premise that the TEOS-GPTMS hybrid system represents a promising alternative to produce bifunctional barrier-bioactive coatings.

Improving the mechanical properties of strontium nitrate doped dicalcium phosphate cement nanoparticles for bone repair application

Advances in the science and technology of bone materials and cements have been expanded over the past several years. The combination of reinforcing materials with bone cement has been proven with the increase in strength and biocompatibility of the porous scaffold. The aim of this study was to investigate and compare four specific types of the scaffold. The effect of strontium nitrate on dicalcium phosphate (DCaP) bone cements made by co-precipitation method was investigated. In this study, a pure sample of brushite (Br) and strontium nitrate containing (3 wt%, 7 wt%, and 10 wt%) were prepared. The phase composition of the samples was examined by X-ray diffraction (XRD) and their microstructure and morphology were examined using field emission scanning electron microscopy (FESEM) technique. The bioactivity of the samples was evaluated in the simulated body fluid (SBF) and the biodegradability of the samples was measured in the phosphate buffer saline (PBS). The mechanical properties of the sample such as compressive strength and elastic modulus were investigated. Bioactivity and biodegradability tests confirm the result of compressive strength. The SEM images showed that the prepared scaffolds were porous with 55–65% porosity and the interconnected porosity dimention is around 50–100 μm. The obtained results indicated that with increasing hydroxyapatite (HA) and brushite in the nanocomposite, the porosity increased, the size of the porous decreased and the elastic modulus increased. The results of cell culture indicated biocompatibility and non-toxicity of the synthesized scaffolds increased more than 0.989. Also, the ultimate strength of brushite-dicalcium phosphate cements depends on the degree of cement conversion, the porosity of the cement, the size of the crystal and the filler particles. The sample containing 3 wt% strontium nitrates with hydroxyapatite (HA) and brushite (Br) showed proper mechanical and biological properties before and after immersion in SBF solution.

Characterization, bioactivity investigation and cytotoxicity of borosilicate glass/dicalcium silicate composites

Composites of dicalcium silicate cement (C2S), prepared by solid state reaction, were fabricated with 5, 10, 15 and 20 wt% additions of borosilicate glass (BG) prepared by melt–quenching method. Bioactivity behavior of the cement and its composites was estimated by soaking in simulated body fluid (SBF) at 37 ± 0.5 °C for 28 days. Physico-mechanical properties of the cement and its composites were measured. The variations of pH, Ca and P ions concentrations in the SBF solution after soaking were determined. Additionally, the structure was analyzed using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) coupled with energy dispersive spectroscopy (EDS). Evaluation of the cytotoxicity against human normal fibroplast cell line (BJ1) was also carried out. Results showed the formation of hydroxyapatite (HA) layer on the surface of investigated materials after immersion in SBF solution. It can be pointed out that increasing BG content in the present cement composition enhances the mechanical properties and the bioactivity behavior of the cement. Moreover, with increasing the content of BG in cement, the cytotoxicity effect decreases, making these materials possible candidates for dental applications.

Comparative study on microstructure and corrosion behavior of nanostructured hydroxyapatite coatings deposited by high velocity oxygen fuel and flame spraying on AZ61 magnesium based substrates

Hydroxyapatite coatings are biocompatible, osteoconductive and create a corrosion resistance surface on magnesium-based implants. Thermal decomposition of HA during thermal spraying limits its application. To overcome the challenges associated with thermal decomposition of HA during thermal spraying, high velocity oxygen fuel spraying with a good thermal stability for HA is proposed. In this work, the traditional flame spraying was compared to high velocity oxy-fuel (HVOF) for HA depositions on magnesium alloy substrates. The effect of process on microstructure, morphology, corrosion behavior and cellular response of HA layers were evaluated. X-ray diffraction analysis showed that the amount of secondary phases in the HVOF deposited sample was less than that in the flame sprayed coatings. Elemental weight percentage of calcium in corroded surfaces was 21% and 34.5% for HVOF and flame sprayed coatings, respectively. Contrary to the results of the electrochemical impedance spectroscopy measurements for HVOF coating performed during the early hours of immersion in the simulated body fluid (SBF), flame sprayed coating exhibited lower corrosion rate after 5 h immersion in SBF solution.

Study of apatite layer formation on SBF-treated chitosan composite thin films

Surface modifications of thin films based on chitosan (Ch), pure Ch and either Ch/montmorillonite (MMT) or Ch/nanoclay composites, were characterised by infrared spectroscopy (ATR-FTIR), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), and atomic force microscopy (AFM). Biomineralisation of the Ch-based materials without any prior surface treatment was evaluated by immersing films in simulated body fluid (SBF) at 37 °C for 14 days. Samples were compared before and after soaking. Results obtained from SEM-EDX, AFM, and infrared spectroscopy (ATR-FTIR) were compared, and all prepared films showed growth of a new phase containing calcium. The composition of thin films influenced the amount of new phase formed as well as the degree of crystallinity of the newly formed phase. The largest increase was observed for the Ch composite with modified nanoclay. Moreover, increased growth of the new phase on the surface of films after immersion in SBF solution significantly influenced the thermal properties of the materials.

In vitro evaluation of bioactive glass ceramic coating for application on Ti6Al4V based biomedical implants

The present study showed the suitability of bioactive glass-ceramics for application as bioactive coating on Ti based biomedical implants. The desired properties of bioactive glass-ceramic coating were obtained through controlled crystallization. XRD, optical microscopy, SEM in association with EDX data showed the phase composition and morphology of the glass-ceramic coatings. Microhardness distribution across the coated substrates and the scratch resistance property of the coatings were varied for the differently heat treated coated substrates. The bioactivity of the fluroapatite based glass-ceramic coating on Ti6Al4V substrate was investigated in vitro in simulated body fluid (SBF) solution. After immersion in SBF solution the glass-ceramic coating surface was characterized by SEM, EDX analysis and the elemental compositional change of the SBF solution was determined by chemical analysis technique. SEM, EDX analysis and chemical analysis indicated that the glass-ceramic coatings reacted with the SBF solution and formed fluroapatite layer on their surfaces.

In vitro investigations on CoO doped CaF2[sbnd]CaO[sbnd]B2O3[sbnd]P2O5−MO bioactive glasses by means of spectroscopic studies

In this investigation we have synthesized CaF2CaOB2O3P2O5: CoO glasses mixed with different therapeutically active ions viz., Ba2+, Sr2+, Mg2+ and Zn2+ (that play a vital role in the normal functioning of human body) and performed in vitro bioactivity studies by immersing them in simulated body fluid (SBF) for a period of about a month and the obtained results were analyzed using spectroscopic studies. Due to immersion in SBF solution, a thin layer of hydroxy apatite (HAp) is developed on the surface of the samples. The results of XRD, SEM and also IR spectra have confirmed that the layer deposited on the surface of the samples is crystalline HAp mixed with cobalt ions. The quantitative analysis of the results in vitro bioactive studies with the help of optical absorption and IR spectral studies have indicated that BaO is an efficient modifier in accelerating the HAp growth. The cobalt ions are found to be in tetrahedral positions and participated in the glass network with BO4 and PO4 structural units in larger quantities in CoZn and CoMg glasses and such occupancy is found to be the reason for the relatively low bioactive efficiency of these glasses when compared with that of CoBa glass.

Robocast 45S5 bioglass scaffolds: in vitro behavior

The in vitro bioactivity and degradation behavior of 45S5 bioglass robocast scaffolds is investigated by immersion tests in simulated body fluid (SBF). A comparative study is conducted between fully amorphous scaffolds, sintered at 550 °C, and mostly crystalline structures, sintered at 1000 °C. The degradation behavior is evaluated through measurements of the weight loss and solution pH variations upon immersion in SBF. The concurrent formation of calcium-rich precipitates on the scaffold surface during immersion in SBF solution was also monitored. The effect of the degradation on the scaffolds’ mechanical performance in compression is subsequently analyzed. Finally, in vitro cell culture experiments were performed to evaluate the proliferation behavior of osteoblast-like cells onto both types of robocast scaffolds. Amorphous scaffolds exhibited an enhanced in vitro degradation and faster calcium carbonate precipitation. However, cell proliferation was not enhanced in the glassy structures compared to the crystalline scaffolds, which demonstrated also a better mechanical performance, as expected.

Synthesis, characterization and bioactivity of a calcium-phosphate glass-ceramics obtained by the sol-gel processing method

In this work, a calcium-phosphate glass-ceramics was successfully obtained by heat treatment of a mixture of 26.52 in wt.% of fluorapatite (Fap) and 73.48 in wt.% of 77S (77 SiO214 CaO9 P2O5 in wt.%) gel. The calcium phosphate-glass-ceramics was prepared by sol-gel process with tetraethyl orthosilicate (TEOS), triethyl phosphate (TEP), calcium nitrate and fluorapatite. The synthesized powders were characterized by some commonly used tools such as X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), 31P magic angle spinning nuclear magnetic resonance (MAS-NMR), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and thin-film X-ray diffraction (TF-XRD). The obtained results seemed to confirm the nucleation and growth of hydroxyapatite (Hap) nano-phase in the glass. Moreover, an in-vitro evaluation of the glass-ceramic was performed. In addition, to assess its bioactive capacity, it was soaked in simulated body fluid (SBF) at different time intervals. The SEM, EDS and TF-XRD analyses showed the deposition of hydroxyapatite on the surface of the specimens after three days of immersion in SBF solution. The mechanical properties of the obtained material such as rupture strength, Vickers hardness and elastic modulus were measured. In addition, the friction coefficient of calcium phosphate-glass-ceramics was tested. The values of the composite of rupture strength (24MPa), Vickers hardness (214Hv), Young's modulus (52.3GPa), shear modulus (19GPa) and friction coefficient (0.327) were obtained. This glass-ceramics can have useful applications in dental prostheses. Indeed, this material may have promising applications for implants because of its content of fluorine, the effective protector against dental caries.

In vitro bioactivity studies of ceramic structures isolated from marine sponges

In this work, we focused on the potential of bioceramics from different marine sponges—namely Petrosia ficiformis, Agelas oroides and Chondrosia reniformis—for novel biomedical/industrial applications. The bioceramics from these sponges were obtained after calcination at 750 °C for 6 h in a furnace. The morphological characteristics were evaluated by scanning electron microscopy (SEM). The in vitro bioactivity of the bioceramics was evaluated in simulated body fluid (SBF) after 14 and 21 d. Observation of the bioceramics by SEM after immersion in SBF solution, coupled with spectroscopic elemental analysis (EDS), showed that the surface morphology was consistent with a calcium-phosphate (Ca/P) coating, similar to hydroxyapatite crystals (HA). Evaluation of the characteristic peaks of Ca/P crystals by Fourier transform infrared spectroscopy and x-ray diffraction further confirmed the existence of HA. Cytotoxicity studies were carried out with the different ceramics and these were compared with a commercially available Bioglass®. In vitro tests demonstrated that marine bioceramics from these sponges are non-cytotoxic and have the potential to be used as substitutes for synthetic Bioglass®.

Microstructural characterization, biocorrosion evaluation and mechanical properties of nanostructured ZnO and Si/ZnO coated Mg/HA/TiO2/MgO nanocomposites

Nano-ZnO monolayer and nano-Si/ZnO double-layer coatings were deposited on a Mg/HA/TiO2/MgO nanocomposite using radio frequency magnetron sputtering. The composition and surface morphology of the specimens were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, Fourier-transform infrared spectroscopy, transmission electron microscopy, atomic force microscopy and field-emission scanning electron microscopy equipped with energy dispersive X-ray spectroscopy. Potentiodynamic polarization and immersion tests were used to investigate the corrosion behavior of samples. The Si/ZnO nanocomposite coating, which had an average thickness of 1.7μm, exhibited a uniform and dense film, consisting of a ZnO outer layer (~1.1μm thick) and a Si inner layer (~0.6μm thick). However, some pores and cracks were observed in the ZnO monolayer coating (~1.5μm thick). In addition, the Si and ZnO nanoparticles had a spherical morphology with an average particle size of 28–40nm. Higher polarization resistance values were obtained for the nano-Si/ZnO coated sample (~2.55kΩcm2) compared with that of the ZnO coated (~1.34kΩcm2) and uncoated (~0.14kΩcm2) samples in a simulated body fluid (SBF). The results from the hydrogen evolution studies indicated that the nano-Si/ZnO-coated sample had a lower degradation rate (1.07ml/cm2/day) than the ZnO-only coated sample (2.25ml/cm2/day) and the uncoated sample (4.42ml/cm2/day). After 168h of immersion in a SBF solution, a larger amount of hydroxyapatite precipitated on the Si/ZnO coating than the ZnO coating, which resulted in an improvement in the bioactivity. The compressive strength and elongation of uncoated Mg/HA/TiO2/MgO decreased from 253MPa and 9.8% to 104MPa and 5.2% after 28days of immersion in SBF solution, whereas the Si/ZnO coated sample indicated a compressive strength of 148MPa and elongation of 7.2%. Therefore, the double-layer Si/ZnO composite coating prepared by magnetron sputtering on the Mg/HA/TiO2/MgO nanocomposite is more suitable for biomedical applications.

In Vitro and in Vivo Studies of Novel Poly(D,L-lactic acid), Superhydrophilic Carbon Nanotubes, and Nanohydroxyapatite Scaffolds for Bone Regeneration.

Poly(D,L-lactide acid, PDLLA) has been researched for scaffolds in bone regeneration. However, its hydrophobocity and smooth surface impedes its interaction with biological fluid and cell adhesion. To alter the surface characteristics, different surface modification techniques have been developed to facilitate biological application. The present study compared two different routes to produce PDLLA/superhydrophilic vertically aligned carbon nanotubes:nanohydroxyapatite (PDLLA/VACNT-O:nHAp) scaffolds. For this, we used electrodeposition and immersion in simulated body fluid (SBF). Characterization by goniometry, scanning electron microscopy, X-ray diffraction, and infrared spectroscopy confirmed the polymer modifications, the in vitro bioactivity, and biomineralization. Differential scanning calorimetry and thermal gravimetric analyses showed that the inclusion of VACNT-O:nHA probably acts as a nucleating agent increasing the crystallization rate in the neat PDLLA without structural alteration. Our results showed the formation of a dense nHAp layer on all scaffolds after 14 days of immersion in SBF solution; the most intense carbonated nHAp peaks observed in the PDLLA/VACNT-O:nHAp samples suggest higher calcium precipitation compared to the PDLLA control. Both cell viability and alkaline phosphatase assays showed favorable results, because no cytotoxic effects were present and all produced scaffolds were able to induce detectable mineralization. Bone defects were used to evaluate the bone regeneration; the confocal Raman and histological results confirmed high potential for bone applications. In vivo study showed that the PDLLA/VACNT-O:nHAp scaffolds mimicked the immature bone and induced bone remodeling. These findings indicate surface improvement and the applicability of this new nanobiomaterial for bone regenerative medicine.