Bioactive Glass Coatings Research Articles

Bioactive coating of zirconia toughened alumina ceramic implants improves cancellous osseointegration

Bioactive coatings have the potential to improve the bony integration of mechanically loaded orthopedic ceramic implants. Using the concept of mimicking the natural bone surface, four different coatings of varying thickness on a zirconia toughened alumina (ZTA) ceramic implant were investigated regarding their osseointegration in a drill-hole model in sheep. The hypothesis that a bioactive coating of ZTA ceramics would facilitate cancellous bone integration was investigated. The bioactive coatings consisted of either a layer of covalently bound multi phosphonate molecules (chemical modification = CM), a nano hydoxyapatite coating (HA), or two different bioactive glass (BG) coatings in micrometer thickness, forming a hydroxyl-carbonate apatite layer on the implant surface in vivo (dip-coated 45S5 = DipBG; sol-gel 70S30C = SGBG). Coated surfaces were characterized by scanning electron microscopy and X-ray photoelectron spectroscopy. After 12 weeks, osseointegration was evaluated via mechanical push-out testing and histology. HA enhanced the maximum push-out force (HA: mean 3573.85 ± 1119.91 N; SGBG: mean 1691.57 ± 986.76 N; p = 0.046), adhesive shear strength (HA: mean 9.82 ± 2.89 MPA; SGBG: mean 4.57 ± 2.65 MPA; p = 0.025), and energy release rate (HA: mean 3821.95 ± 1474.13 J/mm2; SGBG: mean 1558.47 ± 923.47 J/mm2; p = 0.032) compared to SGBG. The implant-bone interfacial stiffness increased by CM compared to SGBG coating (CM: mean 6258.06 ± 603.80 N/mm; SGBG: mean 3565.57 ± 1705.31 n/mm; p = 0.038). Reduced mechanical osseointegration of SGBG coated implants could be explained histologically by a foreign body reaction surrounding the implants.

Bioactive Glass and Silicate-Based Ceramic Coatings on Metallic Implants: Open Challenge or Outdated Topic?

The overall success and long-term life of the medical implants are decisively based on the convenient osseointegration at the hosting tissue-implant interface. Therefore, various surface modifications and different coating approaches have been utilized to the implants to enhance the bone formation and speed up the interaction with the surrounding hosting tissues, thereby enabling the successful fixation of implants. In this review, we will briefly present the main metallic implants and discuss their biocompatibility and osseointegration ability depending on their chemical and mechanical properties. In addition, as the main goal of this review, we explore the main properties of bioactive glasses and silica-based ceramics that are used as coating materials for both orthopedic and dental implants. The current review provides an overview of these bioactive coatings, with a particular emphasis on deposition methods, coating adhesion to the substrates and apatite formation ability tested by immersion in Simulated Body Fluid (SBF). In vitro and in vivo performances in terms of biocompatibility, biodegradability and improved osseointegration are examined as well.

Electrophoretic deposition and characterization of bioglass-whisker hydroxyapatite nanocomposite coatings on titanium substrate

Electrophoretic deposition of bioactive glass (BG) coatings reinforced by whisker hydroxyapatite (WHA) particles was investigated in this work. Different BG powders as freeze dried (FBG) with fine particle size and calcined (CBG) with coarse particle size were used. Hydroxyapatite with whisker morphology reinforced microstructure of BG composite coatings and improved their mechanical properties. CBG and FBG coatings with 50 and 75 wt% WHA respectively, showed the highest bonding strength and bioactivity response as optimum coatings. Combination of WHA and BG particles had synergistic effect on the generation of apatite layer on the coatings during bioactivity test. Cellular behavior was influenced by surface roughness and environment alkalinization generated by BG dissolution. Finer particle size of FBG compared to CBG had positive effect on bioactivity and antibacterial characteristics of the coatings due to its rapid dissolution. FBG powder calcination conducted simultaneously with sintering of corresponding coated samples without negative effect on BG characteristics.

Bioactive glass coating using aerosol deposition

Abstract This work demonstrates the successful deposition of bioactive glass (BG) 45S5 coatings on various metallic and ceramic substrates at room temperature under low vacuum condition by using aerosol deposition (AD). This room temperature and particle impact consolidation-based deposition method enabled us to deposit well-adhered and dense BG coatings directly on metallic and ceramic substrates. In vitro tests with human osteoblast-like cells on substrates with a 45S5 BG coating demonstrated high cell activity on the surfaces. All tested materials exhibited high in vitro biocompatibility as no inhibition in cell proliferation could be observed. The utilization of AD process for achieving non-crystalline BG coatings is promising for practical bio-medical applications, e.g. , bioactive coatings on bioinert metallic and ceramic substrates.

Functional Polyethylene Terephthalate with Nanometer‐Sized Bioactive Glass Coatings Stimulating In Vitro and In Vivo Osseointegration for Anterior Cruciate Ligament Reconstruction

Functional Polyethylene Terephthalate with Nanometer‐Sized Bioactive Glass Coatings Stimulating In Vitro and In Vivo Osseointegration for Anterior Cruciate Ligament Reconstruction

In Vitro Assessment of Bioactive Glass Coatings on Alumina/Zirconia Composite Implants for Potential Use in Prosthetic Applications.

Achieving the stable osteointegration of prosthetic implants is one of the great challenges of modern orthopedic surgery. The fixation of ceramic acetabular cups of hip joint prostheses is usually achieved using a metal shell provided with screws or pegs that penetrate into the host pelvic bone. The deposition of bioactive coatings on the implant surface to be put in contact with bone could be a valuable strategy to promote a more “physiological” osteointegration. In this work, bioactive glass porous coatings were manufactured on the top of alumina/zirconia composite implants by two different methods, i.e., sponge replication and laser cladding. The coated samples underwent immersion studies in Kokubo’s simulated body fluid (SBF) to assess in vitro bioactivity and were found to exhibit an excellent hydroxyapatite-forming ability, which is key to allow bonding to bone. Biological tests using mesenchymal stem and osteoblast-like cells revealed the good biocompatibility of both types of materials. Furthermore, a higher level of mineralization was induced by the sponge-replicated coatings at 10 days. Overall, these results are highly promising and encourage further research on these materials.

Surface properties of Ce-TZP/Al2O3 composite ceramics by coating mesoporous bioactive glass

The Ce-TZP/Al2O3 composite ceramic substrate coated mesoporous bioactive glass was obtained by the sol-gel dip-coating method. As a comparative investigation, the traditional bioactive glass (BG) coatings were prepared. The results displayed that BG coatings surface could found many cracks, while MBG coatings were crack-free and intact. Hydroxyapatite (HAp) formation was confirmed by XRD and SEM after the vitro SBF soaking. Cells experiments were carried to analyze cell viability, cell proliferation and cell attachment upon BG and MBG coatings surface. Compared to BG coatings, crack-free MBG coatings can greatly improve the bioactivity of Ce-TZP/Al2O3 composite ceramic substrate. The present results suggest that the composite material of Ce-TZP/Al2O3 coated MBG has excellent bioactivity and is expected to be the potential bone replacement materials.

Cu-Releasing Bioactive Glass Coatings and Their in Vitro Properties.

Bioactive glasses are well-known materials suitable for bone-related applications thanks to their biocompatibility and osteoconductivity. In order to improve their in vivo performance, the modification of the glass composition by adding ions with specific biological functions is required. As copper (Cu) possesses antibacterial properties, in this study, 5 wt % of CuO has been added to the 45S5 bioactive glass composition. The investigation of the effect of the Cu-containing bioactive glass on cellular behavior has revealed that the presence of Cu induces an early differentiation of human mesenchymal stem cells through osteoblast phenotype, promotes the expression of anti-inflammatory interleukin, and reduces proinflammatory interleukin expression. With the aim to produce coatings with antibacterial properties, the Cu-containing bioactive glass was used as the target material for the pulsed laser deposition (PLD) of bioactive thin films. PLD experiments were carried out at different substrate temperatures to study the effect on the film's characteristics. All of the films are compact, crack-free, and characterized by a rough morphology and good wettability. The in vitro bioactivity was demonstrated by the apatite growth on the coating surface, after soaking in simulated body fluid, revealed by Raman spectroscopy and scanning electron microscopy-energy dispersive X-ray analyses. The antibacterial study proved that the material showed more effective activity against three Gram-negative bacteria ( Pseudomonas aeruginosa, Escherichia coli, Salmonella enterica) rather than against Gram-positive bacteria ( Staphylococcus aureus).

Modelling aspects of laser cladding of bioactive glass coatings on ultrafine-grained titanium substrates

Titanium alloys, due to their exceptional mechanical properties and biocompatibility, are commonly used to produce medical implants nowadays. However, the presence of such elements as aluminium and vanadium can be harmful to human health. One of the possible solutions could be replacing the titanium alloys with ultrafine-grained commercially pure titanium (cpTi). The yield and also the ultimate strength of cpTi can exceed 1000 MPa. One of the most promising methods in manufacturing medical implants with improved biological fixation is laser cladding in which bioactive glass coatings are imposed on metallic substrates. The aim of this work is development of a 3D numerical model of the above mentioned additive manufacturing process. The obtained model is able to predict the stress-strain and temperature distributions during the processing. A sequentially coupled finite element (FE) model of laser cladding has been developed by applying element birth and death technique to calculate the transient temperature fields used in the stress analysis. The concentrated volumetric heat source from the laser beam moving along the metal surface has been represented by the Gaussian distribution in the radial and exponential decay in the depth direction. The developed FE based numerical model is capable to support the optimal design of such advanced multi-layered structural materials using the laser cladding technique.

Microstructural and in vitro characterization of 45S5 bioactive glass coatings deposited by solution precursor plasma spraying (SPPS)

The present work focused on the development of bioactive glass coatings employing Solution Precursor Plasma Spraying. Precursors of SiO2, CaO, Na2O and P2O5 were mixed in distilled water to prepare concentrated solutions with a composition close to the 45S5 bioactive glass.Solutions were rheologically characterized to assess their stability with time and deposited onto AISI type 304 stainless steel to develop coatings under different parameters related to the thermal spraying technique. The effect of these parameters on coatings microstructure was studied by scanning electron microscopy. Coatings were also analysed by X–ray diffraction and scratch test to complete the microstructural characterization. Moreover, coatings bioactivity was evaluated by immersing them in Simulated Body Fluid.The study showed that using short spraying distances and low argon flow rates, gave rise to the typical microstructure derived from liquid feedstocks whereas some crystallization associated to the long spray distance used occurred. Scratch test revealed that the resulting coating possessed good mechanical properties when compared with similar coatings obtained by other plasma spraying techniques. Moreover, the obtained coating could develop an hydroxycarbonate apatite layer when in contact with Simulated Body Fluid as demonstrated by scanning electron microscopy, X–ray diffraction and Fourier transform infrared spectroscopy.

Post-deposition heat treatment effect on microstructure of suspension plasma sprayed bioactive glass coatings

This research addresses a simple and easy method to improve the microstructure of suspension plasma sprayed bioactive glass coatings. Based on previous research of the group, a SPS bioactive glass coating was deposited under optimised variables employing a stable suspension feedstock.After the microstructural characterisation, the coatings were subjected to a heat treatment at 400, 500 and 600 °C peak temperatures. These temperatures have been chosen according to the shrinkage curve of the working glass which results from a hot stage microscope. Results show an improvement of the coatings microstructure (reduction in both porosity and thickness and increment of the adhesion) after a heat treatment at 500 °C with respect to the original coating. However, for a temperature of 400 °C the coating microstructure is not altered (porosity, thickness and adherence are the same as those of the original sample) while at 600 °C the entire coating is completely delaminated.

Effect of suspension medium on the characteristics of electrophoretically deposited bioactive glass coatings on titanium substrate

Bioactive glasses (BGs) have been extensively investigated for use in medical applications due to their excellent biocompatibility and bioactivity. In this work, synthesized BG nanoparticles were deposited on titanium substrate by electrophoretic deposition (EPD) method. Suspensions of BG nanoparticles were prepared in different solvents (methanol, ethanol, isopropanol and butanol) using triethanolamine (TEA) as dispersing additive. Adsorption of TEA on BG particles increased with molecular size of alcohols; so the optimum concentration of TEA obtained at less amounts in larger molecular size alcohols: 0.4, 0.2 and 0.13Vol% for ethanol, isopropanol and butanol based suspensions, respectively. Suspension medium had the great effect on the microstructure of obtained coatings. Microstructures with mostly coarse, mixed (fine and coarse) and fine particles were obtained using ethanol, isopropanol and butanol based suspensions, respectively. Among the suspensions, the isopropanol based one with optimum TEA amount had the highest stability. Also the coatings obtained from isopropanol based suspension had the relatively high sinterability and roughness. So, the isopropanol based coating was chosen as the optimum one. The amorphous structure of optimum BG coating was survived even after sintering at 800 °C. The optimum coating showed good fibroblast cell adhesion and antibacterial activity against Escherichia coli and Staphylococcus aureus bacteria.

Laser coating of bioactive glasses on bioimplant titanium alloys

AbstractLaser‐assisted material processing is a promising field for new material synthesis. This study explores the feasibility of using laser as a tool to synthesize SiO2‐Na2O‐CaO‐P2O5 bioactive glass coatings on Ti‐6Al‐4V alloy for bio‐implant application. Various laser processing conditions were explored to investigate their effects on coating characteristics. Detailed microstructure and elemental distribution on the top surface and in the cross‐sectional region of the bioactive glass‐coated alloy were investigated by scanning electron microscope and energy dispersive spectroscopy. Bio‐mineralization in simulated body fluid for both representative‐coated samples and uncoated control sample for comparison was carried out. The thermokinetic effects during laser processing were simulated using a multi‐physics finite element model. The results demonstrated synthesis of bioactive glass coating on the metal substrate with local segregation of Na, P, and Si elements and considerable dilution of Al and Ti in the coating from the alloy substrate impacted the bioactivity of the coating. Although the observations suggest that the laser processing is a promising method in applying bioactive glasses coatings, further efforts are warranted to optimize laser processing conditions to produce adherent coating while retaining its bioactivity.

A Facile Flow-Casting Production of Bioactive Glass Coatings on Porous Titanium for Bone Tissue Engineering.

Additive manufacturing enabled the fabrication of porous titanium (PT) with customized porosity and mechanical properties. However, functionalization of PT surfaces with bioactive coatings is being challenged due to sophisticated geometry and highly porous structure. In this study, a facile flow-casting technique was developed to produce homogeneous 45S5 bioactive glass (BG) coatings on the entire surface of PT. The coating weight as a function of BG concentration in a BG-PVA slurry was investigated to achieve controllable coating yield without blocking macropore structure. The annealing-treated BG coating not only exhibited compact adhesion confirmed by qualitative sonication treatment, but also enhanced the mechanical properties of PT scaffolds. Moreover, in-vitro assessments of BG-coated PT cultured with MC3T3-E1 cells was carried out having in mind their potential as bioactive bone implants. The experimental results in this study offer a simple and versatile approach for the bio-functionalization of PT and other porous biomedical devices.

Bioactive sol-gel glass-coated wood-derived biocarbon scaffolds

Bioactive glass coatings were deposited for the first time onto wood-derived biocarbon scaffolds using the sol-gel technique. The cellular pore structure of the beech wood was retained during the sol-gel coating process. Owing to the presence of the bioactive glass layer, the originally bioinert biocarbon scaffold was fully covered with newly-formed hydroxyapatite (HA) upon soaking in simulated body fluid. The ability to form HA is generally accepted as the proof of in vitro bioactivity. This opens up the possible application of wood-derived scaffolds in biomedicine (bone repair) and biotechnology.

Solution Precursor Plasma Spraying (SPPS): A novel and simple process to obtain bioactive glass coatings

This research addresses the use of an emerging plasma spray technique known as Solution Precursor Plasma Spraying (SPPS) to obtain bioactive glass coatings. In SPPS, the feedstock is a sol precursor of the bioactive glass instead of glass particles. Precursor feedstock composition (presence or not of acid catalyst), plasma torch enthalpy and stand-off distance of the spraying process have been varied to produce bioactive glass coatings of nominally 45S5 composition. A good quality coating was obtained when catalyst (0.2 M acid nitric) was used in the precursor and the plasma spraying took place with shorter stand-off distance and higher plasma enthalpy. Bioactivity in Simulated Body Fluid test was confirmed and an effect of the coating interconnected porosity to enhance bioactivity was observed.

Synergistic Effect of Copper-Containing Mesoporous Bioactive Glass Coating on Stimulating Vascularization of Porous Hydroxyapatite Orbital Implants in Rabbits

Rapid and complete vascularization of the porous orbital implants after enucleation is vital for reducing postoperative complications, such as exposure and infection. In this study, the porous hydroxyapatite (pHA) scaffolds modified with the mesoporous bioactive glass with and without adding copper (MBG, Cu-MBG) were prepared by sol-gel technique and followed by evaporation induced self-assembly (EISA) process. The macro-/microstructure analysis of the modified scaffolds (i.e., MBG/pHA, Cu-MBG/pHA) showed highly interconnected macropores, and unique mesoporous structures in the pore wall with higher surface area. A primary angiogenic test in a panniculus carnosus muscle model in rabbit indicated that the Cu-MBG coating was significantly beneficial for the vascularization in the porous architecture of the scaffolds in the early stage. These results suggest that the Cu-MBG modification provides a simple and effective strategy to endow favorable biological performances with pHA implants and greater potential for future application in orbit reconstruction.

Electrophoretic Deposition as a New Bioactive Glass Coating Process for Orthodontic Stainless Steel

This study investigated the surface modification of orthodontic stainless steel using electrophoretic deposition (EPD) of bioactive glass (BG). The BG coatings were characterized by spectrophotometry, scanning electron microscopy with energy dispersive X-ray spectrometry, and X-ray diffraction. The frictional properties were investigated using a progressive load scratch test. The remineralization ability of the etched dental enamel was studied according to the time-dependent mechanical properties of the enamel using a nano-indentation test. The EPD process using alternating current produced higher values in both reflectance and lightness. Additionally, the BG coating was thinner than that prepared using direct current, and was completely amorphous. All of the BG coatings displayed good interfacial adhesion, and Si and O were the major components. Most BG-coated specimens produced slightly higher frictional forces compared with non-coated specimens. The hardness and elastic modulus of etched enamel specimens immersed with most BG-coated specimens recovered significantly with increasing immersion time compared with the non-coated specimen, and significant acid-neutralization was observed for the BG-coated specimens. The surface modification technique using EPD and BG coating on orthodontic stainless steel may assist the development of new non-cytotoxic orthodontic metallic appliances having satisfactory appearance and remineralization ability.

Evaluating the critical strain energy release rate of bioactive glass coatings on Ti6Al4V substrates after degradation.

It has been reported that the adhesion of bioactive glass coatings to Ti6Al4V reduces after degradation, however, this effect has not been quantified. This paper uses bilayer double cantilever (DCB) specimens to determine GIC and GIIC, the critical mode I and mode II strain energy release rates, respectively, of bioactive coating/Ti6Al4V substrate systems degraded to different extents. Three borate-based bioactive glass coatings with increasing amounts of incorporated SrO (0, 15 and 25mol%) were enamelled onto Ti6Al4V substrates and then immersed in de-ionized water for 2, 6 and 24h. The weight loss of each glass composition was measured and it was found that the dissolution rate significantly decreased with increasing SrO content. The extent of dissolution was consistent with the hypothesis that the compressive residual stress tends to reduce the dissolution rate of bioactive glasses. After drying, the bilayer DCB specimens were created and subjected to nearly mode I and mode II fracture tests. The toughest coating/substrate system (one composed of the glass containing 25mol% SrO) lost 80% and 85% of its GIC and GIIC, respectively, in less than 24h of degradation. The drop in GIC and GIIC occurred even more rapidly for other coating/substrate systems. Therefore, degradation of borate bioactive glass coatings is inversely related to their fracture toughness when coated onto Ti6A4V substrates. Finally, roughening the substrate was found to be inconsequential in increasing the toughness of the system as the fracture toughness was limited by the cohesive toughness of the glass itself.

Titanium addition influences antibacterial activity of bioactive glass coatings on metallic implants.

In an attempt to combat the possibility of bacterial infection and insufficient bone growth around metallic, surgical implants, bioactive glasses may be employed as coatings. In this work, silica-based and borate-based glass series were synthesized for this purpose and subsequently characterized in terms of antibacterial behavior, solubility and cytotoxicity. Borate-based glasses were found to exhibit significantly superior antibacterial properties and increased solubility compared to their silica-based counterparts, with BRT0 and BRT3 (borate-based glasses with 0 and 15 mol% of titanium dioxide incorporated, respectively) outperforming the remainder of the glasses, both borate and silicate based, in these respects. Atomic Absorption Spectroscopy confirmed the release of zinc ions (Zn2+), which has been linked to the antibacterial abilities of glasses SRT0, BRT0 and BRT3, with inhibition effectively achieved at concentrations lower than 0.7 ppm. In vitro cytotoxicity studies using MC3T3-E1 osteoblasts confirmed that cell proliferation was affected by all glasses in this study, with decreased proliferation attributed to a faster release of sodium ions over calcium ions in both glass series, factor known to slow cell proliferation in vitro.