Simulated Body Fluid Solution Research Articles

Tribocorrosion Behaviour of a Ti–25Nb–3Zr–2Sn–3Mo Alloys Induction Nitride Layer in a Simulated Body Fluid Solution

Ti–25Nb–3Zr–2Sn–3Mo (TLM) alloys have been used in orthopaedics due to their excellent biocompatibility. However, the poor tribological performance caused by the low shear strength limits the applicability of TLM alloy. Herein, the surface of the TLM alloy was strengthened by induction nitriding technology, and the microstructure of the formed nitride layer as well as its corrosion property were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and electrochemical workstation. The results showed that a gradient nitride layer with a thickness of ~30 μm was obtained on the surface of the TLM alloy after induction nitriding and the surface microhardness of the TLM alloy also increased from approximately 230 HV to 1253 HV. Meanwhile, the corrosion resistance of the TLM alloy in simulated body fluids (SBFs), was significantly improved by the nitride layer, which was supported by the corrosion potential value increasing from −665.77 (the raw sample) to −241.00 mV (the nitrided sample). Triborrosion behaviour is also characterized by a reciprocating sliding wear tester connected to an electrochemical workstation with different electrochemical conditions. The results evidenced that the TLM alloy has excellent tribocorrosion resistance after induction nitriding, who’s the mechanical material loss (WA) was only 0.23% of that of the raw sample under a 10 N load, and the total material loss (WT) was 15% of that of the raw sample.

In Vivo Degradation Behavior of Magnesium Alloy for Bone Implants with Improving Biological Activity, Mechanical Properties, and Corrosion Resistance.

This study aimed to establish a surface modification technology for ZK60 magnesium alloy implants that can degrade uniformly over time and promote bone healing. It proposes a special micro-arc oxidation (MAO) treatment on ZK60 alloy that enables the composite electrolytes to create a coating with better corrosion resistance and solve the problems of uneven and excessive degradation. A magnesium alloy bone screw made in this way was able to promote the bone healing reaction after implantation in rabbits. Additionally, it was found that the MAO-treated samples could be sustained in simulated body-fluid solution, exhibiting excellent corrosion resistance and electrochemical stability. The Ca ions deposited in the MAO coating were not cytotoxic and were beneficial in enhancing bone healing after implantation.

Gelatin-Curcumin Nanocomposites as a Coating for Implant Healing Abutment: In Vitro Stability Investigation.

Regarding the importance of preventing peri-implantitis in dental implants, the current study aimed to coat a healing abutment with gelatin−curcumin nanocomposites, and the stability of this coating on the healing abutment was evaluated. A cell viability measuring test was used to determine the cytotoxicity of nanocomposites against dental pulp stem cells. To show the pattern of curcumin release from nanocomposites, drug dissolution apparatus two was applied. Then, 16 healing abutments were examined in vitro. Titanium healing abutments were coated with the gelatin−curcumin nanocomposite. The dip coating method was applied for coating and the consistency of coated cases was evaluated at intervals of one, 30, and 60 days after coating inside the simulated body fluid (SBF) solution. A scanning electron microscope (SEM) was used for investigating the microstructure and morphology of coatings, and an energy dispersive X-ray (EDX) was applied for determining the combination of the coating. Moreover, the healings were weighed before and after coating via an accurate digital scale with an accuracy of 0.0001. Finally, the data were analyzed using SPSS software. The prepared nanocomposite was non-cytotoxic against tested cells. The nanocomposite showed a relatively rapid release pattern in the first 10 days for curcumin. The release of curcumin from the nanoparticles continued slowly until the 30th day. The weight changes were statistically significant (p-value < 0.001) during this time. Based on the post hoc test, the weight between two times immediately after coating and 30 days after coating, and also one day after coating and 30 days after coating, was statistically insignificant. The results revealed that the coating of the gelatin−curcumin nanocomposite on the healing was successful and this consistency was kept for at least one month. It is necessary to investigate more evaluations in different fields of physicochemical, mechanical, and antimicrobial aspects for coated healing abutments.

The effects of chemical conversion parameters on morphology and corrosion performance of calcium phosphate coating on AZ31 alloy

To improve the corrosion resistance of magnesium alloy, Ca–Ph coatings were prepared on AZ31 alloy substrates by chemical conversion. The treatment time and temperature have been adjusted to prepare the coatings with various morphologies, compositions, and properties. The surface morphologies and chemical compositions were investigated using a scanning electron microscope (SEM) with energy dispersive spectroscopy (EDS), and the phase structure was investigated using X-ray diffraction (XRD). The corrosion performance of the coatings was investigated by an electrochemical test and immersion test. All the coatings showed significant corrosion protection to the substrate in the simulated body fluid (SBF) solution. The coating prepared at 5 h duration was thicker than other coatings but with the lowest corrosion current density in the electrochemical test and weight loss studies after being immersed in the SBF solution for 7 days had the slightest loss. The results showed that higher temperatures favored the presence of hydroxyapatite and that the coating thickness had an enhanced influence on the corrosion performance.

In situ fabrication of cerium-incorporated hydroxyapatite/magnetite nanocomposite coatings with bone regeneration and osteosarcoma potential.

With the ultimate goal of providing a novel platform able to inhibit bacterial adhesion, biofilm formation, and anticancer properties, cerium-doped hydroxyapatite films enhanced with magnetite were developed via spin-coating. The unique aspect of the current study is the potential for creating cerium-doped hydroxyapatite/Fe3O4 coatings on a titanium support to enhance the functionality of bone implants. To assure an increase in the bioactivity of the titanium surface, alkali pretreatment was done before deposition of the apatite layer. Scanning electron microscopy (SEM) in conjunction with energy-dispersive X-ray (EDX) spectroscopy, X-ray diffraction (XRD) analysis, and Fourier transform-infrared (FTIR) spectroscopy were used to evaluate coatings. Coatings demonstrated good efficacy against Staphylococcus aureus and Escherichia coli, with the latter showing the highest efficacy. In vitro bioactivity in simulated body fluid solution showed this material to be proficient for bone-like apatite formation on the implant surface. Electrochemical impedance spectroscopy was undertaken on intact coatings to examine the barrier properties of composites. We found that spin-coating at 4000 rpm could greatly increase the total resistance. After seeding with osteoblastic populations, Ce-HAP/Fe3O4 materials the adhesion and proliferation of cells. The heating capacity of the Ce-HAP/Fe3O4 film was optimal at 45 °C at 15 s at a frequency of 318 kHz. Osseointegration depends on many more parameters than hydroxyapatite production, so these coatings have significant potential for use in bone healing and bone-cancer therapy.

Hydroxyapatite Growth on Activated Carbon Surface for Methylene Blue Adsorption: Effect of Oxidation Time and CaSiO3 Addition on Hydrothermal Incubation

Many adsorbent materials are now commercially available; however, studies have focused on modifying them to enhance their properties. In this study, an activated carbon (AC) and hydroxyapatite (HAp) composite was synthesized by the immersion of ACs in a simulated body fluid solution, varying the AC oxidation degree along with the addition of CaSiO3. The resulting composites were characterized by ash %, X-ray fluorescence (XRF), Fourier-transformed infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and point of zero charge (PZC). The characterization results indicated that the addition of CaSiO3 and the oxygenated functional groups in the AC surface are key factors for HAp growth. The composites were tested on methylene blue (MB) adsorption as a potential application for the synthesized materials. Adsorption isotherms were modeled with Langmuir and Freundlich isotherms, and the composites were fitted to a Langmuir model with the highest qmax value of 9.82. The kinetic results indicated that for the pseudo-second-order model, the composites fitted, with a contact time of 180 min to remove a 95.61% average of the MB. The results indicate that composite materials can be an efficient adsorbent for the removal of MB from aqueous solutions at low concentrations since the material with the highest amount of HAp growth removed 99.8% of the MB in 180 min.

The influence of heat treatment on the bioactivity of ZrO2 coatings and corrosion resistance of 316L steel in SBF solution

Zirconium dioxide ceramic coatings were applied to the surface of 316L steel using the sol-gel method. The coated samples were heated at 300 °C or 500 °C. The task of the coatings was to increase the bioactivity and corrosion resistance of 316L steel in the SBF (simulated body fluids) environment. Examination of the chemical composition (EDS, Raman spectroscopy) of these samples after 150 days of exposure showed an increased presence of phosphates on the surface compared to uncoated steel samples. The deposition of ZrO2 coatings also increased the corrosion resistance of 316 L steel in the SBF solution (electrochemical tests).

Synthesis of TiO2 Nanotubes for Improving the Corrosion Resistance Performance of the Titanium Implants

TiO2 nanotubes were successfully synthesized by electrochemical method. A fluoride salt mixture was used as an electrolyte for synthesizing TiO2 nanotubes on titanium substrates. In this work, we have reported the synthesis procedure of TiO2 nanotubes and investigated the corrosion resistance of TiO2 nanotubes coated on the Ti substrate. FE-SEM was used to observe the morphology and determine the size of the TiO2 nanotubes. The phase formation and crystal quality of TiO2 nanotubes were studied by XRD measurements. One-microliter distilled water droplets were used to define the wettability of the TiO2 nanotube surfaces by measuring the contact angle. The corrosion resistance behavior of specimens was analyzed in the simulated body fluid solution (SBF) using potentiodynamic polarization tests for potential application as implants.&#x0D;

Zn doped CaP coatings used for controlling the degradation rate of MgCa1 alloy: In vitro anticorrosive properties, sterilization and bacteria/cell-material interactions

The purpose of this study was to investigate the effect of Zn doped CaP coatings prepared by micro-arc oxidation method, as a possible approach to control MgCa1 alloy degradation. All the prepared coatings comprised a calcium deficient CaP phase. The control in this evaluation was performed with undoped CaP coating in SBF solution at body temperature (37 ± 0.5⁰C). The investigation involved determination of microchemical, mechanical, morphological, properties along with anticorrosive, cytocompatibility and antibacterial efficacy. The effect of sterilization process on the properties of the surfaces was also investigated. The results showed that the addition of Zn into CaP increased the corrosion resistance of MgCa1 alloy. Moreover, the adhesion strength of the coatings to MgCa1 alloy was enhanced by Zn addition. In cytotoxicity testing of the samples, extracts of the samples in MEM were incubated with L929 cells and malformation, degeneration and lysis of the cells were examined microscopically after 72 h. The results showed that all samples were cytocompatible. The degradation of MgCa1 alloy in the simulated body fluids (SBF) or DMEM was decreased by coating with CaP. Moreover, the degradation rate of CaP was further decreased by adding a small amount of Zn into the CaP matrix. The samples having CaP coatings and Zn doped CaP coating demonstrated antibacterial efficacy against E.coli. As a result, coating of magnesium alloy with Zn-doped CaP decreased the degradation rate, increased the corrosion resistance, cytocompatibility and the antibacterial effects of the alloys.

Facile Synthesis of TiO2-SiO2-P2O5/CaO/ZnO with a Core-Shell Structure for Bone Implantation.

A facile synthesis method was developed to synthesize TiO2-SiO2-P2O5/CaO or TiO2-SiO2-P2O5/ZnO with a core-shell structure. The carboxylic cation exchanger Tokem-250 has a high selectivity for Ca2+/Zn2+ ions and was used in this study. The framework of the material in the shell was TiO2-SiO2-P2O5, and the inner part was filled with CaO (sample TiO2-SiO2/CaO) or ZnO (sample TiO2-SiO2-P2O5/ZnO). A stepwise heat treatment (drying in a drying oven at 60 °C for 30 min, then annealing in a muffle furnace for 30 min at 150, 250, and 350 °C, at 600 °C for 6 h, and at 800 °C for 1 h) was needed to obtain a homogeneous material. The poly(vinyl alcohol) was used as a binding additive. The obtained composites were characterized by a regular structure and highly developed surface. The samples exhibit bioactive properties in the simulated body fluid (SBF) solution, since the surface contains active centers (Si4+, Ti4+) which contribute to mineralization and precipitation of the calcium-phosphate compounds on the surface from biological media. The TiO2-SiO2-P2O5/CaO-PVA samples did not exceed acceptable hemolysis levels for medical materials.

Corrosion of NiTi stents induced by galvanic interaction with radiopaque materials

Nickel titanium (NiTi) alloys are used as a base material for biomedical devices and implants, such as stents. One limitation associated with NiTi stents is the low radiopacity. Thus, radiopaque markers, made of noble materials, are usually attached to NiTi stents to increase the stent radiopacity, raising concerns regarding galvanic corrosion in body fluid environments. This research aims to assess the galvanic interactions of NiTi alloys and NiTi stent when coupled to radiopaque markers materials in simulated body fluid solution (NaCl 0.9%). Electrochemical measurements, using flat specimens and NiTi stents were carried out. After the tests, scanning electron microscopy (SEM) surface analysis was performed. The results from polarization curves indicate that the NiTi/Platinum (NiTi/Pt) couple is more susceptible to galvanic corrosion than the pairs of NiTi/Palladium (NiTi/Pd) and NiTi/Gold (NiTi/Au). The potential difference of 628 mV presented by the NiTi/Pt couple was the highest among the galvanic couples investigated. Higher values of galvanic potential and galvanic current were also obtained by the pair NiTi/Pt. In direct galvanic short-term measurements with NiTi stent/Pt, no increase in the current density or presence of pits on the NiTi stent surface was observed. However, long-term potentiostatic test, applying 280 mV, which corresponds to the galvanic potential of the NiTi/Pt couple, resulted in current peaks of 1.500 µA and led to severe localized corrosion of NiTi stents, revealing a risk of corrosion induced by coupling Pt markers to NiTi stent.

Thermal stability, grain growth kinetics, mechanical properties, and bio-corrosion resistance of pure Mg, ZK30, and ZEK300 alloys: A comparative study

Thermal stability, grain growth kinetics, tensile properties, and corrosion resistance of commercially pure (CP) magnesium can be tailored by zinc addition in conjunction with small additions of zirconium and rare earth (RE) elements, which need to be systematically investigated. Accordingly, the thermal stability, grain growth kinetics, tensile properties, and bio-corrosion resistance of hot rolled CP Mg, and ZK30 (Mg-3Zn-0.5Zr) and ZEK300 (Mg-3Zn-0.5RE-0.5Zr) alloys were compared in this work. The solute drag effect of Zn in the ZK30 alloy and the Zener pinning effect of CeZn 5 compound in the ZEK300 alloy were responsible for the improved thermal stability and higher grain growth activation energy of these alloys compared to CP Mg. The tensile properties of hot rolled ZK30 and ZEK300 alloys were superior due to their fine grain sizes. Moreover, corrosion tests in simulated body fluid (SBF) solution confirmed the higher corrosion resistance of the ZEK300 alloy for biomedical implant applications. The shear punch testing (SPT) results revealed that the ZEK300 alloy can better retain its superior mechanical properties during deformation/testing at elevated temperatures. Grain growth annealing led to a decrement in strength but an increment in the total elongations, and hence, the highest tensile toughness was obtained for the ZEK300 alloy with an average grain size of ~ 8.5 μm. Accordingly, this work proposed that RE addition at the micro-alloying level to a lean Mg-Zn alloy is quite effective in the enhancement of thermal stability, room/elevated-temperature mechanical properties, and bio-corrosion resistance.

Development of Ti–Ta–Nb–Mo–Zr high entropy alloy by μ-plasma arc additive manufacturing process for knee implant applications and its biocompatibility evaluation

It describes development of equiatomic Ti–Ta–Nb–Mo–Zr HEA by μ-plasma arc additive manufacturing process for knee implant applications, its microstructure study and in-vitro biocompatibility evaluation using cell viability, released metallic ions, and corrosion behaviour. Cell viability was evaluated by treating HeLa, HEK-293, and BHK cells with 20, 40, 60, and 100 μl concentrations of prepared media for the developed HEA for 24, 48, 72 h incubation durations. Released amounts of Ti, Ta, Nb, Mo, and Zr ions were estimated in 4.4; 5.4; and 7.4 pH value simulated body fluid solution (SBF) for immersion durations of 1, 3, and 7 weeks. Corrosion behaviour was studied in 4.4; 5.4; and 7.4 pH value SBF solution at 37 °C. Ti–Ta–Nb–Mo–Zr HEA consists of BCC major and minor phases having fine dendritic and inter-dendritic structure. Average % cell viability decreased with increase in prepared media concentration. Overall average values of viability for HeLa, HEK-293, and BHK cells treated with prepared media are 90%; 88%; and 92% respectively. BHK cells showed maximum cell viability at each media concentration and for each incubation duration. Ti–Ta–Nb–Mo–Zr HEA did not harm appearance of HeLa, HEK-293, and BHK cells. Overall averaged released amounts of Ti, Ta, Nb, Mo, and Zr ions are 37, 26; 57; 38, and 28 ppb respectively. Ti–Ta–Nb–Mo–Zr HEA has minimum values of all essential corrosion parameters without causing any pitting. It showed excellent biocompatibility hence referred as bio-HEA which is a new class of biomaterials for knee implants that can overcome limitations of the present materials.

Microstructural evolution and biological properties of PEO coating on SLM-prepared NiTi alloy

Selective laser melting (SLM)-prepared NiTi alloy is considered to have great application potential in the fabrication of complex-structured metal implant materials. However, the SLM-NiTi alloy still suffers from some disadvantages, such as poor bio-corrosion resistance, bio-compatibility, and health hazards caused by the release of nickel ions. In order to improve the surface biological properties of SLM-NiTi alloys, bio-active coatings rich in Ca and P elements were prepared on SLM-NiTi alloys by PEO process in this work. Confocal laser scanning microscopy, SEM, EDX, XRD, and XPS were utilized to feature the micro-structure, thickness, element information, and composition of SLM/PEO coatings at different oxidation times. The adhesion strength was determined using scratch testing. A potential polarization test and a simulated body fluid (SBF) immersion test were applied to assess the corrosion resistance and detect the biological activity of SLM/PEO coatings at varied oxidation periods, respectively. The results showed that the growth of SLM/PEO coatings was hindered due to the overflow of Ni elements at the spark discharge stage (stage II). However, with the PEO process, the inhibition effect of Ni element was gradually eliminated. The pore size, thickness and the TiO2 rutile phase content of the SLM/PEO coatings gradually increased over time. However, the coating density, roughness and adhesion strength increased first and then decreased, and the SLM/PEO coatings were maximized at 15 min. The main composition of SLM/PEO coatings was TiO2, CaO, CaHPO4 and Ca3(PO4)2, and hydroxyapatite (HA) was gradually formed in the coating with time. The SLM/PEO-15 min coating with high thicknesses and rutile phase content, as well as optimum density provided optimum corrosion resistance (1.615 × 10−6 A cm−2). Meanwhile, the SLM/PEO-15 min coating possessed the best surface roughness and higher active element content, providing an excellent nucleation point and growth environment for the deposition of apatite. And the Ni element on the SLM-NiTi alloy substrate surface (oxidation time from 0 to 20 min) was significantly reduced from 12.49 % to 0.52 % after immersing in SBF solution for 24 h. Therefore, the PEO process can effectively improve the corrosion resistance and biological activity of SLM-NiTi alloy and inhibit the release of Ni elements.

The effect of friction stir process on the mechanical, tribological, and biocompatibility properties of AZ31B magnesium alloy as a biomaterial: A pilot study.

Recently, AZ31B magnesium alloy has been widely employed in automotive, aerospace, and bio implant industries due to its light-weight and biocompatibility properties. However, the equilibrium of ductility and strength of this material and the negativity brought by its poor wear behavior have limited its versatile use. Friction stir processing (FSP) has been commonly used as severe plastic deformation method for improving mechanical and tribological properties of metal sheets. The effect of this method on the biocompatibility of materials is a matter of curiosity that should be emphasized. So, the present study aims to investigate the effect of friction stir process on the mechanical, tribological, and biocompatibility properties of AZ31B magnesium alloy. It is observed that FSP enhanced the tensile properties of the alloy but decreased its elongation. It was determined that the base material exhibited ductile character on the fracture surface of the specimens, and mixed ductile/brittle fracture was evident with the FSP. In the FSP zone, the hardness value was improved by 17% compared to the base material. Also, the wear performance of the alloy enhanced in ambient air and Simulated Body Fluid (SBF) solution. Wear properties in SBF solution were better due to less adhesive bonds between the friction surfaces. This assessment was supported by SEM images of the wear path and surface of counter bodies. On the other hand, FSPed AZ31B alloy materials with improved strength properties were not cytotoxic for human gingival fibroblasts, and these results may suggest that the materials are safe for clinical uses.

Green synthesized graphene-hydroxyapatite nanocomposites for bioimplant applications

Graphene-hydroxyapatite (HA) nanocomposites are fabricated using betel leaf extract as a green reducing agent. UV-Visible, Raman, and XRD techniques proved graphene's formation and the HA's α-TCP crystal structure. The mechanical properties obtained from Nanoindentation and Vicker indentation techniques demonstrated the enhancement in the elastic modulus, microhardness, and fracture toughness values by 114%, 36%, and 141%. The SEM analysis of radial cracks confirmed that reinforced graphene sheets hindered the crack propagation by ridge growth and bridging. Surface roughness (110%) and coefficient of friction (40%) values are also enhanced for these nanocomposites. Further, the nanocomposites also showed in vitro cell viability (140% at 200 μg/mL) for human embryonic kidney cells and osteoconductivity in simulated body fluid solution.

Surface modification of activated carbon cloth with calcium silicate and hydroxyapatite: bioactive composite material

In this study new compounds consisting of activated carbon cloths (ACC) modified with calcium silicate (CaSiO3) were prepared for hydroxyapatite (HAP) generation. ACC samples were oxidized with 8 M HNO3 at different times (15 min and 2 h), to increase oxygenated functional groups. The CaSiO3 fine powders were prepared by chemical coprecipitation using Ca(NO3)2∙4H2O and Si(OC2H5)4, and 5 M NaOH was used as precipitant. The resulting powders were mixed with ethanol by ultrasound stirring and the previously oxidized activated carbon fibers were placed leaving under stirring for 30 min to allow particle dispersion. Once the formed compounds were dried, the samples were immersed in a simulated body fluid (SBF) solution for 21 days in conical tubes at 36.5 °C to allow the HAP formation on the ACC/CaSiO3 composite surface. The results indicated that the increase in oxidation time improves HAP formation on the surface from ACC/CaSiO3 compounds and this bioactive composite may be a potential material for bone regeneration.

Corrosion and in vitro cytocompatibility investigation on the designed Mg-Zn-Ag metallic glasses for biomedical application

In the present work, seven Mg-Zn-Ag alloys with the nominal composition of Mg96-xZnxAg4 (x = 17, 20, 23, 26, 29, 32, 35 in at.%) were prepared by induction melting and single-roller melt-spinning. The X-ray diffraction (XRD) analyses indicate the metallic glasses with three composition of Mg73Zn23Ag4, Mg70Zn26Ag4, and Mg67Zn29Ag4 were obtained successfully. The differential scanning calorimetry (DSC) measurement was used to obtain the characteristic temperature of Mg-Zn-Ag metallic glasses for the glass-forming ability analysis. The maximum glass transition temperature (Trg) was found to be 0.525 with a composition close to Mg67Zn29Ag4, which results in the best glass-forming ability. Moreover, the immersion test in simulated body fluid (SBF) demonstrate the relative homogeneous corrosion behavior of the Mg-Zn-Ag metallic glasses. The corrosion rate of Mg-Zn-Ag metallic glasses in SBF solution decreases with the increase of Zn content. The sample Mg67Zn29Ag4 has the lowest corrosion rate of 0.19 mm/yr, which could meet the clinical application requirement well. The in vitro cell experiments show that the Madin-Darby canine kidney (MDCK) cells cultured in sample Mg67Zn29Ag4 and its extraction medium have higher activity. However, the Mg-Zn-Ag metallic glasses exhibit obvious inhibitory effect on human rhabdomyosarcoma (RD) tumor cells. The present investigations on the glass-forming ability, corrosion behavior, cytocompatibility and tumor inhibition function of the Mg-Zn-Ag based metallic glass could reveal their biomedical application possibility.

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.

Physico-chemical, mechanical and antibacterial properties of the boron modified biphasic larnite/bredigite cements for potential use in dentistry

In recent years, there has been a growing interest in developing more reactive calcium silicate cements (CSCs) with superior bioactivity, self-setting properties and mechanical strength, allowing them to be used for various dental applications. In this study, we have produced a biphasic larnite/bredigite calcium magnesium silicate cement (CaMgSi) by the low-temperature sol-gel method and calcination of xerogels at 700 °C. The effect of boron (B) incorporation (0.25 and 0.5 mol) on the structural and physico-chemical properties of CaMgSi and boron-modified CaMgSi/0.25B and CaMgSi/0.5B cements was evaluated using various characterization techniques, such as X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), scanning and transmission electron microscopy (SEM/TEM) and solid-state NMR spectroscopy (ssNMR). The results showed that with the increasing boron content, the cements hydration, self-setting and mechanical properties were improved. Hence, the final setting time of CaMgSi/0.5B cement decreased from 30 (undoped cement) to 19 min, while the compressive (CST) and diametral tensile strengths (DTS) increased almost twice to the highest values of 85 ± 9 MPa and 8.8 ± 1 MPa, respectively. The in-vitro bioactivity and degradation of cements were examined in simulated body fluid (SBF) solution during 8 weeks of soaking. Interestingly, the prevalence of calcite and aragonite crystals of various morphologies was observed on all cement surfaces, whereas a plate-like particles of precipitated calcium phosphate layer were found only in the boron-modified CaMgSi/0.25B and CaMgSi/0.5B cements. In addition, a very good antibacterial activity of the cement suspensions was revealed against all the tested bacteria, i.e. Staphylococcus aureus, Escherichia coli and Enterococcus faecalis, showing a promising result for potential use in dentistry.