Preparation and bioactivity of apatite coating on Ti6Al4V alloy by microwave assisted aqueous chemical method

To improve the bioactivity of titanium and its alloys, dense and uniform apatite coatings were prepared on Ti6Al4V titanium substrates using microwave assisted aqueous chemical method. The influence of the pretreatment to the titanium substrates and the Ca/P molar ratio of the microwave solution on the coating deposition and morphology, as well as the bioactivity of the coated samples were studied. Results showed that during the microwave process, alkali treatment followed by heat treatment to the titanium substrates would promote the rapid deposition of hydroxyapatite to form coating. And the morphologies of the apatite coatings could be adjusted by the Ca/P molar ratio of the microwave solution. After immersion test in simulated body fluid (SBF), the coated titanium alloy exhibits a good bioactivity by inducing the formation of apatite depositions.     

Bioactivity modulation of Bioglass® powder by thermal treatment

A discussion of the effects of Bioglass^® powder crystallisation on the in vitro bioactivity in simulated body fluid (SBF) is presented.Starting from Bioglass^® powder, different glass–ceramics were obtained by thermal treatments between 580 °C and 800 °C, with variable crystallisation content (from 10 to 92 wt%). All samples (glass and glass–ceramics) showed apatite formation at their surface when immersed in SBF. In case of the glass and the samples with lowest crystallinity, the first step of apatite formation involved a homogenous dissolution followed by an amorphous calcium phosphate (CaP) layer precipitation. For the samples with a high crystallisation content, heterogeneous dissolution occurred. For the first time, the Stevels number of the amorphous phase is used to explain the possible dissolution of the crystalline phase present in materials with a similar chemical composition of the Bioglass^®. All samples presented at 21 days of immersion in SBF B-type hydroxycarbonate apatite crystals.     

Biomimetic apatite deposited on microarc oxidized anatase-based ceramic coating

Biomimetic apatite was formed on a microarc oxidized (MAO) anatase-based coating containing Ca and P in a simulated body fluid (SBF). At the process of the SBF immersion (0–96 h), the Ca and P of the MAO coating dissolve into the SBF, increasing the supersaturation degree near the surface of the MAO coating, which could promote the formation and growth of apatite. After SBF immersion for 7 days, the surface of the MAO coating was modified slightly. The entire surface immersed for 14 days was covered by an apatite coating. The apatite possesses carbonated structure, controllable crystallinity and pore networks. The results indicate that the MAO coating formed in an electrolyte containing phosphate and EDTA–Ca chelate complex possesses good apatite-forming ability.     

In vitro apatite-forming ability of calcium aluminate blends

Calcium aluminate cement (CAC) blends show great potential as biomaterial when compared to commercial products used in odontology and orthopedics. Mixtures of CAC +4 wt% of different additives (alumina, zirconia, zinc oxide, tricalcium phosphate or hydroxyapatite) containing compositions, resulted in samples with low porosity levels and smaller pore sizes after their contact with simulated body fluid (SBF) solution, which was associated with apatite precipitation on the materials’ surface. In order to certify these aspects, the in vitro apatite-formation ability (bioactivity) of CAC blends was evaluated by pH and calcium concentration measurements in SBF for samples previously treated (or not) with sodium silicate (SS) solution. The surface of the samples after immersion in SBF or SBF/SS was analyzed by scanning electron microscopy (SEM), energy dispersive X-ray (EDX) analysis and confocal Raman spectroscopy. In addition, the in vitro apatite deposition and the osteoblastic cell viability were also evaluated. SEM results showed that the precipitation of phases was detected on the CAC blend samples’ surfaces. The presence of calcium and mainly phosphorus by EDX indicated the formation of calcium phosphate phases. Moreover, the presence of a more homogeneous apatite-like layer on the samples’ surface was observed after treatment with sodium silicate solution. The detection of the Raman signature at 960 cm⁻¹, confirmed the presence of an apatite-like layer on the surface of the compositions after immersion in SBF or SBF/SS. Regarding the osteoblastic cell viability results, blends with collagen, zinc oxide and zirconia presented better results when compared to commercial products.     

Fabrication and In Vitro Bioactivity of Poly (ϵ-caprolactone) Composites Filled with Silane-Modified Nano-Apatite Particles

Silane coupling agents were firstly employed to modify the surfaces of nano-apatite (n-HA) particles, and then thin films of the silanized n-HA/PCL composites were successfully developed by incorporating solvent dispersion and thermal co-blending with hot-pressing methods. In vitro studies were conducted using the 2-time simulated body fluid (2SBF). Composite specimens were soaked in 2SBF from 3 to 14. Results showed that a layer of bone-like apatite was formed within 7 days on the surfaces of all composites, after its immersion in 2SBF, demonstrating moderate in vitro bioactivity of these composites.     

Examination of morphology,degradation and biocompatibility of fluorapatite–forsterite nanocomposite

This research has been done to study the characteristics and biocompatible evaluation of nano-biocomposite ceramic. Nanocomposites with the base of fluorapatite with 15, 25, 35 wt% of forsterite have been synthesized by the sol-gel method. Fluorapatite-forsterite nanocomposites have been characterized in terms of degradation by determining the weight change percentages and the pH changes in terms of bioactivity by checking the apatite layer formation using a solution of simulated body fluid (SBF). The release rate of silicon ions and fluorine ions are measured by ICP and fluorine selective electrode, respectively. This is the indication of desirable bioactivity in the synthesized nanocomposite and can be increased by adding the amount of forsterite in the samples and the higher solubility of the forsterite incompatible with fluorapatite. Compressive strength measurements indicate that the compressive strength of the nanocomposite increases by adding the forsterite percentages. The result of MTT assay indicates nontoxicity and decreases the cell viability in 7 days incompatible with the first day.     

A comprehensive study on copper incorporated bio-glass matrix for its potential antimicrobial applications

In this study, sol-gel derived Cu substituted 70S bioglass (70SiO2-(20-x) CaO–10P2O5-xCuO; where x = 0, 0.5, 1, 1.5) were synthesized as a new multifunctional bioactive glasses (BGs). The effect of Cu substitution in the bio-glass matrix was evaluated for its impact on pathogen (Escherichia coli and Staphylococcus aurous). Fourier Transform Infrared spectroscopy (FT-IR), Thermogravimetric Analysis (TGA), X-Ray Diffraction (XRD), Inductively Coupled Plasma spectroscopy (ICP) and Scanning Electron Microscopy (SEM) revealed that the obtained powders are amorphous silicate glass. The substituted element is present in the desired molar concentration. In vitro bioactivity test was performed in SBF solution by immersion of bioglass pellets. Antibacterial test was carried out against Escherichia coli and Staphylococcus aureus. The results showed that the prepared BGs have a high acellular bioactivity observed by a fast formation of thick and continuous layer of carbonated hydroxyapatite (CHA). The antibacterial properties of the substituted bio-glass matrix was indicated by the growth inhibition of bacterial colonies. The obtained results showed that copper substituted bio-glass is having potential to avoid post-surgical infections and it also represents the capability of hard tissue regeneration.     

Processing and in vitro bioactivity of high-strength 45S5 glass-ceramic scaffolds for bone regeneration

In this paper, the compressive strength and in vitro bioactivity of sintered 45S5 bioactive glass scaffolds produced by powder technology and polymer foaming were investigated. The sintering temperature of scaffolds was 975 °C. The characterization of scaffolds before immersion in SBF was performed by scanning electron microscopy (SEM) and microtomography (μCT). The scaffolds were also tested for compression, and their density and porosity were measured. After immersion, the samples were observed through SEM and analyzed using EDS, X-ray diffraction (XRD), and infrared spectroscopy (FT-IR). Mass variation was also estimated. The glass-ceramic scaffolds showed a 61.44±3.13% interconnected porosity and an average compressive strength of 13.78±2.43 MPa. They also showed the formation of a hydroxyapatite layer after seven days of immersion in SBF, demonstrating that partial crystallization during sintering did not suppress their bioactivity.     

Apatite formation on titania–vaterite powders in simulated body fluid

Titania–hydroxyapatite composites were prepared by soaking compacts of a powder mixture consisting of crystalline titania and calcium carbonate (vaterite) to form apatite in simulated body fluid (SBF). The apatite crystal formed on compacts in SBF at 37 °C within 2 days. The apatite-forming ability of the mixtures was much higher than that of titania crystals such as anatase or rutile on their own. Calcium carbonate (vaterite), which has high solubility in the aqueous solution, plays an important role in the apatite formation; the dissolution is suggested to increase the supersaturation of the apatite in SBF. Formation of titanium hydroxide groups, which may induce the apatite formation, is drastically promoted on the powder-compacts by the soaking in SBF, independently of the structures of the titania crystals (anatase or rutile). The apatite formation on the compact of the titania–calcium carbonate (vaterite) powder mixture containing the anatase phase occurs in a shorter period than that on the one of titania (rutile)–calcium carbonate (vaterite). Crystalline titania (anatase phase) is suggested to be particularly effective in inducing the apatite nucleation.     

Preparation of Bioglasses Developed from Bypass Cement Dust for Bone Regeneration and Comparing Their Radiation Damage Prediction with Natural Bone

Cement industry causes many respiratory diseases due to the formation of bypass cement dust (BCD) as by-product. For this purpose a new study to get ride BCD from the environment by prepared three selected bioglasses samples with composition Na₂O₍₁₀₎?+?P₂O_5(90-x)?+?BCD_(x) where x value?=?10, 20, 30 in mol%. BCD contains an appropriate amount of calcium ions that can contribute in bioglass formulation for bone regeneration. Cooperative characterization for the prepared glasses were carried out through FTIR and SEM analysis before and after immersion in simulated body fluid (SBF) solution for up to 23 days at 37 °C. Therefore, the three samples can only be directly compared in the range of BCD content between 10 and 30 wt.%. After immersion in SBF, porous apatite layer is formed on the glass surface after 13 days and become denser after 23 days. Our results showing that, the porous hydroxy apatite layer was formed faster in the BCD 30 sample than in the BCD10 and BCD 20 samples. Further, SEM analysis revealed the formation of highly porous apatite layer on the composite surfaces when immersed in SBF solution at 37 °C. These porous structures provide channels for bone in growth and improve the microscopic bioresorption. The predicting radiation damage and atomic displacements per atom in BCD-30 sample if it was implanted to a patient exposed to radiotherapy or x-rays has been calculated and compared with natural bone. The gamma shielding parameters, mass stopping power (MSP), range for both proton (H-ions) and alpha (He-ions) in bioglass-BCD-30 and human bone tissue have estimated.

     

Microscopic and spectroscopic evidences for multiple ion-exchange reactions controlling biomineralization of CaO.MgO.2SiO2 nanoceramics

This study is focused on the mechanism of in vitro biomineralization on the surface of CaO.MgO.2SiO₂ (diopside) nanostructured coatings by scanning electron microscopy, energy-dispersive X-ray spectroscopy and inductively coupled plasma spectroscopy assessments. A homogeneous diopside coating of almost 2 µm in thickness was deposited on a medical-grade stainless steel by coprecipitation, dipping and sintering sequences. After soaking the sample in a simulated body fluid (SBF) for 14 days, a layer with the thickness of 8 µm is recognized to be substituted for the primary diopside deposit, suggesting the mineralization of apatite on the surface. Investigations revealed that the newly-formed layer is predominantly composed of Ca, P and Si, albeit with a biased accumulations of P and Si towards the surface and substrate, respectively. The variations in the ionic composition and pH of the SBF due to the incubation of the sample were also correlated with the above-interpreted biomineralization. In conclusion, the multiple ion-exchange reactions related to Ca, Mg, Si and P were found to be responsible for the in vitro bioactivity of nanodiopside.     

Bioactivity of Hench Bioglass and Corresponding Glass-Ceramic and the Effect of Transition Metal Oxides

Glasses based on the Hench’s bioglass doped with (0.1%) of one of the 3d-transition metals were prepared. Infrared absorption spectra of the prepared samples were measured. The prepared glassy samples were crystallized through controlled thermal treatments and the precipitated crystalline phases were identified by X-ray diffraction analysis. Infrared reflection spectroscopy was performed on the glassy and crystalline derivative samples before and after immersion in simulated body fluid for different time periods of 1 week, 2 weeks or 1 month. The main crystalline phase formed in the undoped and TM-doped samples are solid solutions of sodium calcium silicates (1Na.2Ca.3Si and 3Na.3Ca.6Si). Infrared reflectance spectra reveal the formation of the two layers of SiO₂-gel and CaO-P₂O₅ and the transition metal ions seem to act as nucleating catalysts initiating the ease of formation of an apatite layer and hence promoting bioactivity in the doping level.     

Synthesis and in vitro bioactivity assessment of injectable bioglass−organic pastes for bone tissue repair

The aim of this work was to study the bioactivity of systems based on a clinically tested bioactive glass (BG) particulates (mol%: 4.33 Na₂O−30.30 CaO−12.99 MgO−45.45 SiO₂−2.60 P₂O₅−4.33 CaF₂) and organic carriers. The cohesiveness of injectable bone graft products is of high relevance when filling complex volumetric bone defects. With this motivation behind, BG particulates with mean sizes within 11−14 μm were mixed in different proportions with glycerol (G) and polyethylene glycol (PEG) as organic carriers and the mixtures were fully injectable exhibiting Newtonian flow behaviors. The apatite forming ability was investigated using X-ray diffraction and field emission scanning electron microscopy under secondary electron mode after immersion of samples in simulated body fluid (SBF) for time durations varying between 12 h and 7 days. The results obtained revealed that in spite of the good adhesion of glycerol and PEG carriers to glass particles during preparation stage, they did not hinder the exposure of bioactive glass particulates to the direct contact with SBF solution. The results confirmed the excellent bioactivity in vitro for all compositions expressed by high biomineralization rates with the formation of crystalline hydroxyapatite being identified by XRD after 12 h of immersion in SBF solution.     

In vitro hydroxiapatite formation on the Ca doped surface of ZSM-5[Ga] type zeolite

A high SiO₂/Al₂O₃ ratio ZSM-5[Ga] type zeolite was synthesized. Then an ionic exchange of Na by Ca ions on the surface was performed. The in vitro bioactivity was assessed by immersing samples in Simulated Body Fluid (SBF) for different periods of time. Bonelike apatite was formed on the zeolite as early as 7 days of immersion. This indicates that this ZSM-5[Ga] zeolite with a Ca-functionalized surface is a potential material for bone tissue regeneration.     

Preparation and in vitro assessment of economic bio-scaffolds modified with wollastonite (CaSiO3)

Porous bioceramic scaffolds are the preferred option for substituting spongy bone. Therefore, this study evaluates the use of carbonate associated with apatite rocks at Hamadat mines (referred to as calcite) as a source of low-cost bioactive material useful for biomedical applications. In this study, the depositional environment and mineralogical, and petrographic behavior of such depositions were studied. Furthermore, the possibility of producing highly porous, low-cost bioceramic scaffolds using the freeze-drying technique was demonstrated. The bioactivity of the produced scaffolds was enhanced by adding different ratios of wollastonite (25, 50 and 75 wt %) to the scaffold’s batches. However, the scaffolds were coated with ZnCl₂ to enhance their antimicrobial susceptibility. The physical and mechanical properties as well as the phase composition and microstructure of the prepared scaffolds were investigated. The X-ray diffraction results revealed the formation of pure phase of α-wollastonite after 3 h of sintering at 1200 °C. To estimate the scaffolds’ biodegradability, the pH and the weight change were measured. The results were confirmed using the inductively coupled plasma measurements for the scaffolds deposited in a simulated body fluid (SBF) solution for 28 days. Results showed that the scaffolds had excellent bioactivity, which was demonstrated by the appearance of apatite particles on their surface after being immersed in the SBF. The antimicrobial activity test revealed that Zn²⁺, NPs and CaSiO₃ had positive effects due to their oxidative stress process. Zn²⁺, Ca²⁺, and Si⁴⁺ cations can be adsorbed on bacterial surface membranes, interacting with the respiratory microbial enzymes, inhibiting their actions, and damaging the cell, thereby causing the bacterial cell decomposition.     

Synthesis and characterization of spinel–forsterite nanocomposites

Although micron size forsterite is biocompatible, the degradation rate of this ceramic is extremely low, and the apatite formation ability is poor as well. In this study, the influence of nanostructure and the degree of crystallinity on the apatite formation ability and degradation rate were investigated. Forsterite was synthesized by 5 h of milling of talc and magnesium carbonate and subsequent annealing at 1000 °C in the presence of chloride ion. To investigate the in vitro bioactivity and degradability, the prepared forsterite powder was pressed in the form of tablets and then immersed in simulated body fluid (SBF) and Ringer's solution, respectively. The results showed that nanostructure forsterite powder with crystallite size of about 20 nm was bioactive and released magnesium ions in the SBF solution. With increasing crystallinity degree of nanostructure forsterite, the apatite formation ability and degradation rate decreased.     

Antibacterial properties,in vitro bioactivity and cell proliferation of titania–wollastonite composites

Titania–wollastonite materials that show high in vitro bioactivity, appropriate cell proliferation and antibacterial behavior have been developed. Titania–wollastonite compounds were synthesized by two different routes: (i) solid state reaction and (ii) sol–gel. The in vitro bioactivity assessment was performed by immersing samples in a simulated body fluid (SBF). The materials characterization, before and after immersion in SBF, was performed by SEM and EDS. Cytotoxicity was assessed by estimating cell proliferation and the antibacterial properties were evaluated by performing a kinetic study of a bacterium growth (Burkhoderia cepacia). In order to evaluate the band gap value UV–vis spectroscopy was performed. A faster apatite layer formation was observed on the samples processed by sol–gel. However, these agglomerates were smaller than those formed on the solid state reaction substrates. The highest inhibition of the bacteria growth and the highest cell proliferation were observed on the samples synthesized by solid state reaction.     

Bioactive properties of CuO doped CaF2‒CaO‒B2O3‒P2O5‒MO(M=Ba,Sr, Zn,Mg) glasses

Calcium oxy fluoro boro phosphate glasses with fixed concentration of CuO and mixed with different modifier oxides (viz., BaO, SrO, ZnO and MgO) that play a vital role in collagen deposition, cellular activity, proliferation of osteoblasts and in blood vessel maturation, producing enzymes etc., that are necessary for normal functioning of human body were synthesized. In vitro bioactivity studies indicated the formation of hydroxy apatite (HAp) layer on the surface of the samples. This was confirmed by XRD and SEM photographs and also IR spectral studies. The magnitude of HAp layer formed was evaluated by measuring weight loss of the samples and pH measurements of the residual simulated body fluid (SBF) solutions at specific intervals of time. The analysis of the results of degradability studies together with spectroscopic studies has revealed that BaO is an effective modifier in improving the bioactivity of the host glass, among all the modifiers investigated.     

Synthesis and characterization of β-TCP/CNT nanocomposite: Morphology,microstructure and in vitro bioactivity

In this study, β-TCP/CNT nanocomposite has been synthesized by solution precipitation method. Then, the effects of the different percentage of CNT (CNT1β-TCP, CNT3β-TCP, CNT5β-TCP) and surfactant (CNT1β-TCP1SDBS, CNT1β-TCP2SDBS, CNT1β-TCP3SDBS) on β-TCP/CNT nanocomposite powder were studied. The X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and Transmission electron microscopy (TEM) analyses were used to characterize the samples. The observations revealed that the microstructure of 1 wt% CNT could provide dispersion without agglomeration in nanocomposite powder; however, a higher concentration of CNT powder in the nanocomposite resulted in the formation of Ca₂PO₇ phase. Implementing 2 wt% of SDBS as a surfactant modified the shape, size, and distribution of CNT particles on nanocomposites. Finally, the nanocomposite sample was immersed in simulated body fluid (SBF) to evaluate the in vitro bioactivity. It obviously showed an apatite layer on the surface after 7 days of immersion in SBF. Taken together, this nanocomposite might be potentially to be used as bone repair biomaterial.     

Formation of dicalcium phosphate dehydrate coating on carbon fibers with in-situ grown graphene nanosheet interlayer

A dicalcium phosphate dehydrate (DCPD) coating was successfully fabricated on carbon fiber with in-situ grown graphene (IGN) interlayer. The obtained coating was analyzed using XRD, SEM, XPS, Raman, TEM and Thermo-gravimetric analysis(TGA). The in-vitro bioactivity of the obtained coating was investigated by simulated body fluid (SBF) immersion test. The results showed that the IGN interlayer grew homogenously on the carbon fiber with a wavy shape. The IGN interlayer was 40–90 nm in length and less than 10 nm in thickness. The DCPD exhibited a flake shape with a size of 10–50 nm. The IGN could bond with the DCPD tightly and form a uniform distribution within the DCPD coating. TGA test revealed that the carbon fiber with IGN interlayer was more effective for DCPD attachment and deposition than pure carbon fiber. The SBF tests showed that the DCPD coating could induce the formation of a cloud shaped apatite layer. The DCPD coated carbon fiber with IGN interlayer would be possible for potential application in tissue engineering.