Bioactivity In Simulated Body Fluid Research Articles

Synthesis and in vitro bioactivity of sodium metasilicate-derived silicon-substituted hydroxyapatite

Structural alteration of synthetic implants aims to achieve better bioactivity, higher cellular response, and regulated degradability, all of which are critical criteria for a biomaterial to serve as a graft in bone regeneration. The aim of this work was to synthesize silicon-substituted hydroxyapatite and test its bioactivity in simulated body fluid (SBF) by proving the use of sodium metasilicate (Na2SiO3.9H2O) as an affordable precursor of silica. Thus, the study evaluated the in vitro bone-bonding capacity of hydroxyapatite (Ca10(PO4)6(OH)2) (HA) substituted with silicate ion (Ca10(PO4)6-x(SiO4)x(OH)2-x; SixHA). The SixHA with x = 0.4 was synthesized by utilizing a wet precipitation method with sodium metasilicate as a low-cost silica alternative for alkoxysilane precursors. The SixHA was then examined for properties such as morphology, elemental composition, phase composition, and the nature of chemical bonds using scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX), X-ray diffractometry (XRD), and Fourier transformed infrared spectroscopy (FTIR), respectively. An in vitro bioactivity experiment was also carried out by incubating the SixHA in simulated body fluid (SBF) at 36.5 °C for 7 and 14 days. The obtained results revealed the substitution of SiO44- for some PO43- groups in the hydroxyapatite structure. The SixHA nucleated more apatite crystals on its surface and demonstrated some degradability during the periods of immersion in SBF. The characteristics of the SixHA imply that it could be used as a graft in bone restoration applications, thus signifying that sodium metasilicate could serve as an economic silica source for silicon-substituted hydroxyapatite production.

Imparting a better corrosion resistance and bioactivity for magnesium through the formation of zinc - zinc oxide - zinc phosphate (hopeite) - magnesium ammonium phosphate (struvite) composite coatings

The present study aims to develop zinc-zinc oxide-zinc phosphate (hopeite)-magnesium ammonium phosphate (struvite) composite coatings to reduce the rate of degradation and to impart a better bioactivity for Mg. Galvanic deposition was employed to form Zn-ZnO coating on Mg, which was subsequently converted to hopeite and struvite by chemical conversion method using diammonium hydrogen phosphate. The structural and morphological characteristics, nature of functional groups, degradation behaviour in Hanks’ balanced salt solution (HBSS) and bioactivity in simulated body fluid (SBF) were evaluated. The findings of the study revealed that Zn-ZnO-hopeite-struvite composite coating has considerably reduced the rate of degradation of Mg in HBSS and promoted the bioactivity of Mg in SBF. The rate of degradation of Mg is decreased from 1.27 ± 0.11 mm/y to 0.13 ± 0.04 mm/y, amounting to ⁓90 % reduction in the corrosion rate. The morphological features reveal that the extent of corrosion attack on Zn-ZnO-hopeite-struvite composite coated Mg is very much limited when compared to that of the uncoated one. The surface of Zn-ZnO-hopeite-struvite composite coated Mg shows many thin needle-like crystals as well as globular-like particles after immersion in SBF when compared to that of uncoated and Zn-ZnO coated Mg. The uniform and compact coating with good adherence, improved corrosion resistance and better bioactivity suggest that Zn-ZnO-hopeite-struvite composite coating is a promising surface modification approach towards the development of Mg-based degradable implants.

Modified Titanium Surface with Nano Amorphous Calcium Phosphate@Chitosan Oligolactate as Ion Loading Platform with Multifunctional Properties for Potential Biomedical Application.

Titanium (Ti) is widely used in medical and dental implants. Calcium phosphate (CPs) coatings enhance Ti implants' osteoinductive properties, and additives further improve these coatings. Recently, a nano amorphous calcium phosphate (nACP) coating decorated with chitosan oligolactate (ChOL) and selenium (Se) showed immunomodulatory effects. This study investigates the surface morphology, composition, bioactivity, mechanical properties, and Se-release mechanism of the nACP@ChOL-Se hybrid coating on Ti substrates. Amorphous calcium phosphate (ACP) was synthesized, and the nACP@ChOL-Se hybrid coating was deposited on Ti substrates using in situ anaphoretic deposition. Physico-chemical characterization was used to analyze the surface of the coating (scanning electron microscopy (SEM), X-ray diffraction (XRD), and Fourier Transform Infrared Spectroscopy). The distribution of Se within the coating was examined with energy-dispersive X-ray spectroscopy (EDS). Bioactivity was evaluated in simulated body fluid (SBF), and adhesion was tested using a scratch test method. In vitro testing determined the release mechanism of Se. SEM images illustrated the surface morphology, while AFM provided a detailed analysis of surface roughness. XRD analysis revealed structural and phase composition, and EDS confirmed Se distribution within the coating. The coating exhibited bioactivity in SBF and showed good adhesion according to the scratch test. In vitro testing uncovered the release mechanism of Se from the coating. This study successfully characterized the surface morphology, composition, bioactivity, and Se-release mechanism of the nACP@ChOL-Se hybrid coating on Ti substrates, offering insights for developing immunomodulatory coatings for medical and dental applications.

Doxorubicin loaded cerium substituted hydroxyapatite nanoparticles: A promising new therapeutic approach for bone regeneration, doxorubicin delivery, and cancer treatment

The current study used the precipitation method to prepare pure calcium hydroxyapatite (HA) and cerium-substituted hydroxyapatite (Ce-HA) nanoparticles, where cerium ions were exchanged into the HA structure at different concentrations ranging from 3 to 7 wt%. X-ray powder diffraction (XRD), field emission scanning electron microscopy (FE-SEM), high resolution transmission electron microscopy (HR-TEM), Fourier transform infrared (FTIR) spectroscopy, Brunauer-Emmett-Teller (BET) surface area measurements, and zeta potential were used to examine the structural characteristics of the nanoparticles. Additionally, the antibacterial and antifungal effects of the produced materials on Gram-positive, Gram-negative, and fungal bacterial species were studied. Nanoparticles with cerium doping showed effective antibacterial and antifungal properties. All samples were tested for bioactivity in simulated body fluid (SBF), and the formation of an apatite layer on their surfaces was highlighted using SEM in conjunction with energy-dispersive X-rays (EDX).Doxorubicin (DOX) release from Ce-HA nanoparticles and pure HA was tested in phosphate-buffered saline (PBS) for up to 28 days. Both nanoparticles were able to release the drug while still being semi-fully loaded. Similarly, the cytotoxic effect of all produced samples on the MG-63 cell line was evaluated, and all samples showed good cytocompatibility. The cytotoxic effect of doxorubicin-loaded nanoparticles showed promising anticancer activity against bone cancer cells, especially samples with high cerium content. The resulting nanoparticles show excellent promising ability for the delivery of doxorubicin to bone cancer with the capacity for bone regeneration.

Preparation of trivalent rare-earth element-substituted bioactive glass robocast scaffolds for osteosarcoma treatment: structural, morphological, mechanical, drug delivery, and biological properties

In this study, trivalent rare-earth ion (Eu3+, Gd3+, and Yb3+)-substituted silicate-based bioactive glass scaffolds were prepared by robocasting method using sol–gel-derived bioactive glass powders for tissue engineering applications and cancer therapy. The structural, morphological, and mechanical properties of the prepared scaffolds as well as their in vitro bioactivity in simulated body fluid (SBF) were investigated in detail. In addition, an anticancer drug (5-FU) adsorption and release behavior of the scaffolds was studied as a function of time. In vitro, cytotoxicity and alkaline phosphatase activity were investigated using human skin fibroblast BJ and osteosarcoma SaOS-2 cells. Results showed that using lanthanide ion-containing (0.5, 1, 3, and 5 wt%) sol–gel-derived bioactive glass powders it was possible to successfully fabricate periodic, mesh-like patterned robocast glass scaffolds. All of the scaffolds prepared in the study sintered at 675 °C showed an amorphous structure. The compressive strength of scaffolds was in the range of 8.8 MPa to 13.6 MPa and the highest strength values were obtained in the Yb3+-containing scaffolds. Hydroxyapatite formation was obtained for the scaffolds immersed in SBF for 28 days. The fluorouracil adsorption amount was calculated to be ~ 25% for all types of scaffolds and the cumulative drug release was in the range of 20–25% depending on the dopant concentration. Results of the in vitro cell culture experiments revealed that all of the scaffolds fabricated in the study were not cytotoxic to fibroblast and osteosarcoma cells for up to 7 days under in vitro conditions. An increase was obtained for the ALP activities for both types of cells as the incubation time was increased.

Enhanced antimicrobial properties and bioactivity of 3D-printed titanium scaffolds by multilayer bioceramic coating for large bone defects

The restoration of large bone defects caused by trauma, tumor resection, or infection is a major clinical problem in orthopedics and dentistry because postoperative infections, corrosion, and limited osteointegration of metal implants can lead to loosening of the implant. The aim of this study was to improve the surface properties of a 3D-printed (electron beam melting) Ti6Al4V-based macroporous scaffold by multilayer coating with bioactive silicate glasses (BAGs) and hydroxyapatite doped with a silver (AgHAP) or AgHAP additionally sonochemically modified with ZnO (ZnO-AgHAP). The coated scaffolds AgHAP_BAGs_Ti and ZnO-AgHAP_BAGs_Ti enhanced cytocompatibility in L929 and MRC5 cell lines and expressed bioactivity in simulated body fluid. A lower release of vanadium ions in coated samples compared to bare Ti scaffold indicates decreased dissolution of Ti alloy in coated samples. The coated samples reduced growth of Escherichia coli and Staphylococcus aureus for 4–6 orders of magnitude. Therefore, the 3D-printed Ti-based scaffolds coated with BAGs and (ZnO-)AgHAP have great potential for application as a multifunctional implant with antibacterial properties for the restoration of defects in load-bearing bones.

3D Printing of Bone Scaffolds Based on Alginate/Gelatin Hydrogel Ink Containing Bioactive Glass 45S5 and ZIF‐8 Nanoparticles with Sustained Drug‐Release Capability

Herein, 3D printing coupled with drug‐release systems introduces many advantages to bone‐regenerative medicine. In this research, hydrogel‐based nanocomposite inks comprising alginate/gelatin (Alg/Gel) matrix supplemented with mesoporous bioactive glass (MBG) and zeolite‐imidazole framework‐8 (ZIF‐8) nanoparticles are presented. A fixed wt% of mixed nanoparticles at MBG/ZIF weight ratios of 85:15 and 70:30 is added to Alg/Gel to prepare nanocomposite inks. All inks have shear‐thinning behavior, facilitating scaffolds’ 3D printing via extrusion. Scaffolds’ 3D spatial and nanocomposite microstructures are confirmed using field‐emission scanning electron microscope and energy‐dispersive X‐ray (FESEM/EDX) and Fourier transform infrared (FT‐IR). Shear punch testing indicates an enhanced shear strength of 85:15 samples in both dry (9.49 ± 0.23 MPa) and wet conditions (1.19 ± 0.16 MPa). After 1 month, nanocomposite scaffolds have a higher degradation rate (65%) than Alg/Gel (50%) in phosphate‐buffered saline. In vitro drug‐release study using UV–visible spectrophotometry exhibits a similar prolonged release profile for 85:15 and 70:30 nanocomposites compared to Alg/Gel. Due to its better mechanical performance, 85:15 is used for bioactivity and cellular tests. MBG provides bioactivity in simulated body fluid by the rapid development of hydroxyapatite validated by FESEM/EDX, XRD, and FT‐IR. Nanocomposite scaffolds exhibit significantly higher MG‐63 cell viability (>90%) than Alg/Gel. Finally, these scaffolds provide a potential additive‐manufacturing solution to bone tissue regeneration.

Polyvinylpyrrolidone Nanofibers Incorporating Mesoporous Bioactive Glass for Bone Tissue Engineering.

Composite biomaterials that combine osteoconductive and osteoinductive properties are a promising approach for bone tissue engineering (BTE) since they stimulate osteogenesis while mimicking extracellular matrix (ECM) morphology. In this context, the aim of the present research was to produce polyvinylpyrrolidone (PVP) nanofibers containing mesoporous bioactive glass (MBG) 80S15 nanoparticles. These composite materials were produced by the electrospinning technique. Design of experiments (DOE) was used to estimate the optimal electrospinning parameters to reduce average fiber diameter. The polymeric matrices were thermally crosslinked under different conditions, and the fibers' morphology was studied using scanning electron microscopy (SEM). Evaluation of the mechanical properties of nanofibrous mats revealed a dependence on thermal crosslinking parameters and on the presence of MBG 80S15 particles inside the polymeric fibers. Degradation tests indicated that the presence of MBG led to a faster degradation of nanofibrous mats and to a higher swelling capacity. The assessment of in vitro bioactivity in simulated body fluid (SBF) was performed using MBG pellets and PVP/MBG (1:1) composites to assess if the bioactive properties of MBG 80S15 were kept when it was incorporated into PVP nanofibers. FTIR and XRD analysis along with SEM-EDS results indicated that a hydroxy-carbonate apatite (HCA) layer formed on the surface of MBG pellets and nanofibrous webs after soaking in SBF over different time periods. In general, the materials revealed no cytotoxic effects on the Saos-2 cell line. The overall results for the materials produced show the potential of the composites to be used in BTE.

3D printing of chitooligosaccharide-polyethylene glycol diacrylate hydrogel inks for bone tissue regeneration.

To date, lack of functional hydrogel inks has limited 3D printing applications in tissue engineering. This study developed a series of photocurable hydrogel inks based on chitooligosaccharide (COS)-polyethylene glycol diacrylate (PEGDA) for extrusion-based 3D printing of bone tissue scaffolds. The scaffolds were prepared by aza-Michael addition of COS and PEGDA followed by photopolymerisation of unreacted PEGDA. The hydrogel inks showed sufficient shear thinning properties required for extrusion 3D printing. The printed scaffolds exhibited excellent shape fidelity and fine microstructure with a resolution of 250 μm. By increasing the COS content, the swelling ratio of the scaffolds decreased, while the compressive strength increased. 3D printed COS-PEGDA scaffolds showed high viability of human bone mesenchymal stem cells in vitro. In addition, scaffolds containing 2 wt% COS showed significantly higher alkaline phosphatase activity, calcium deposition, and bioactivity in simulated body fluid compared to the control (PEGDA). Altogether, 3D printed COS-PEGDA scaffolds represent promising candidates for bone tissue regeneration.

Characterization of nano-hydroxyapatite incorporated carboxymethyl chitosan composite on human dental pulp stem cells.

To compare the odontogenic differentiation potential of a composite scaffold (CSHA) comprising of nano-hydroxyapatite (nHAp) and carboxymethyl chitosan (CMC) with Biodentine on human dental pulp stem cells (hDPSCs). A CSHA scaffold was prepared through an ultrasonication route by adding nHAp and CMC (1:5 w/w) in water medium followed by freeze-drying. Physicochemical characterization was achieved using scanning electron microscopy with energy-dispersive X-ray spectroscopy, X-ray diffraction and Fourier transform infrared spectroscopy. In-vitro bioactivity and pH assessments were done by soaking in simulated body fluid (SBF) for 28 days. The angiogenic and odontogenic differentiation abilities were assessed by expression of vascular endothelial growth factor (VEGF) and Dentine sialophosphoprotein (DSPP) markers on cultured hDPSCs by flow cytometry and RT-qPCR at 7, 14 and 21 days. Cell viability/proliferation and biomineralization abilities of CSHA were compared with Biodentine by MTT assay, alkaline phosphatase (ALP) activity, Alizarin Red Staining (ARS) and osteopontin (OPN) expression on hDPSCs following 7 and 14 days. Data were statistically analysed with Kruskal Wallis and Friedman tests as well as one way anova followed by appropriate post hoc tests (p < .05). Characterization experiments revealed a porous microstructure of CSHA with pore diameter ranging between 60 and 200 μm and 1.67 Ca/P molar ratio along with the characteristic functional groups of both HAp and CMC. CSHA displayed bioactivity in SBF by forming apatite-like crystals and maintained a consistent pH value of 7.70 during 28 days' in vitro studies. CSHA significantly upregulated VEGF and DSPP levels on hDPSCs on day 21 compared with day 7 (p < .05). Further, CSHA supported cell viability/proliferation over 14 days like Biodentine with no statistical differences (p > .05). However, CSHA exhibited increased ALP and ARS activity with an intense OPN staining compared with Biodentine after 14 days (p < .05). The results highlighted the odontogenic differentiation and biomineralization abilities of CSHA on hDPSCs with significant VEGF and DSPP gene upregulations. Further, CSHA exhibited enhanced mineralization activity than Biodentine, as evidenced by increased ALP, ARS and OPN activity on day 14. The nHAp-CMC scaffold has the potential to act as an effective pulp capping agent; however, this needs to be further validated through in-vivo animal studies.

Processing of gelatine coated composite scaffolds based on magnesium and strontium doped hydroxyapatite and yttria-stabilized zirconium oxide

Limited bone bank capacity and risk of infection are some of the main drawbacks of autologous and allogenic grafts, giving rise to synthetic materials for bone tissue implants. The aim of this study was to process and evaluate the mechanical properties and bioactivity of magnesium and strontium doped hydroxyapatite (HAp) scaffolds and investigate the effect of adding zirconium oxide and gelatine coating the scaffolds. Doped nanosized hydroxyapatite powder was synthesized by the hydrothermal method and the scaffolds were made by the foam replica technique and sintered at different temperatures. Yttria-stabilized zirconium oxide (YSZ), synthesized by plasma technology, was used as reinforcement of calcium phosphate scaffolds. Element analysis, phase composition, morphology of the powders and microstructure of the scaffolds were investigated, as well as the compressive strength of the coated and uncoated scaffolds and bioactivity in simulated body fluid (SBF). A microporous structure was achieved with interconnected pores and bioactivity in SBF was confirmed in all cases. The best mechanical properties were given by the coated composite HAp/YSZ scaffolds, withstanding average stresses of over 1019 kPa. These results encourage the idea of use of these scaffolds in bone regenerative therapy and bone tissue engineering.

Effect of tantalum interlayer on hydroxyapatite biointerface for orthopedic applications

Various attempts have been made during recent decades to improve the functionality, biocompatibility and osseointegration of metallic implants. With technological advancement, modifying superficial properties of orthopedic implants has undergone great evolution. Current efforts of scientists and the orthopedic industry have focused on modifying surface properties to achieve a specific biointerface that can reduce patient's healing time and prevent aseptic loosening. This study investigates the contribution of a protective tantalum interlayer deposited on titanium substrates on the growth of hydroxyapatite (HAp) crystals with hydrothermal synthesis method. We investigated the morphology and structure of the produced coatings, as well as in vitro bioactivity in simulated body fluid and biocompatibility in osteoblast-like cell culture. The hydrothermal method allows to synthesize coating with micro-sized HAp crystallites that exhibit rod-like hexagonal shape. The diameter of HAp crystallites may be controlled and driven by nature of the interlayer (tantalum, tantalum oxide or titanium oxide) previously formed on the titanium substrate. Coatings with smaller diameters of HAp crystals (between 0,3 μm and 0,6 μm) synthesized on tantalum-based films were found to be more favorable for cell viability and attachment. High bioactivity and positive effect on the osteoblast-like cells of the HAp biointerface with a tantalum intermediate layer was observed.

Robocasting of multicomponent sol-gel–derived silicate bioactive glass scaffolds for bone tissue engineering

Robocasting is universally recognized as an affordable and reproducible manufacturing strategy to process glass and glass-ceramic materials in the form of highly ordered porous scaffolds for bone tissue engineering (BTE) applications. Nevertheless, while being widely applied to melt-derived bioactive glasses, this technique was seldom implemented with sol-gel materials due to the intrinsic difficulties in producing suitable inks for extrusion and thus, good printing outcomes. The present experimental work describes a new and relatively easy method to manufacture multicomponent sol-gel bioactive silicate scaffolds (oxide system: 47.5SiO2–20CaO–10MgO–10Na2O-10 K2O-2.5P2O5, mol.%) using dried gels as basic material within the ink composition, which allows by-passing intermediate heat treatments that are usually detrimental to the bioactive potential of the material in physiological environment. The scaffolds, exhibiting a total porosity of 81 vol%, were characterized in terms of morphological-compositional features and bioactivity in simulated body fluid (SBF), paying special attention to ion release and surface modifications occurring upon soaking (apatite-forming ability). The compressive strength of the scaffolds (around 5 MPa) was comparable to that of human cancellous bone. Collectively, the results supported the possibility of using robocast sol-gel–derived scaffolds in BTE approaches. Furthermore, a comparison with robocast scaffolds based on a melt-derived glass with the same composition was reported in order to investigate the effect of the synthesis route on the dissolution behavior and morphological features of the final biomaterials.

Effect of Zn and Ga doping on bioactivity, degradation, and antibacterial properties of borate 1393-B3 bioactive glass

Borate 1393-B3 bioactive glasses doped with ZnO or Ga2O3 (1, 3, and 6% mol) were produced by conventional melt quenching. All doped glasses showed in-vitro bioactivity in simulated body fluid (SBF). For the first time, the dissolution behavior of the glasses both in phosphate-buffered saline (PBS) and cell culture medium was investigated. The ion release rate in the cell culture medium increased compared to that in PBS solution. All tested glass compositions, including the parent 1393-B3 glass, showed antibacterial effect against S. aureus and E. coli. The incorporation of Zn and Ga enhanced the viability of MG-63 osteoblast-like cells compared to the base 1393-B3 glass. The results show the potential of Zn and Ga-doped borate glasses in multifunctional tissue engineering applications.

Copper-doped cotton-like malleable electrospun bioactive glass fibers for wound healing applications

The combination of electrospinning and sol-gel methods is attracting the interest of the scientific community for developing three-dimensional bioactive glass (BG)-based fibers. This paper reports the fabrication of cotton-like copper-doped BG fibers by combining electrospinning and sol-gel techniques. Acellular bioactivity in simulated body fluid, ion release, cell viability and scratch cell tests were performed. Results showed that copper was successfully incorporated in the fibers and Cu ions were released in limited concentration over seven days. The presence of copper delayed the mineralization of the fibers upon immersion in simulated body fluid (SBF), but it did not affect keratinocyte viability and migration. Wound closure in the scratch cell test was achieved in 48 h for all the investigated samples.

Controlling the rate of degradation of Mg using magnesium fluoride and magnesium fluoride-magnesium phosphate duplex coatings

The thin and porous Fluoride Conversion Coating FCC with many cracks could not offer a significant improvement in corrosion resistance for Mg. Magnesium phosphate coating improves the corrosion resistance of Mg, good bioactivity, promotes cell viability and cyto-compatibility and exhibits antibacterial activity. However, rapid dissolution in Mg in acidic magnesium phosphate containing solutions leads to the development of an inhomogeneous coating. The present study attempts to prevent the excessive dissolution of Mg by forming a fluoride conversion coating as a pre-treatment in the first stage followed by deposition of magnesium phosphate coating in the second stage to develop magnesium fluoride-magnesium phosphate duplex coatings. The morphological features, structural characteristics, nature of functional groups, corrosion behavior in Hanks’ balanced salt solution and bioactivity in simulated body fluid are assessed to ascertain the suitability of the magnesium fluoride-magnesium phosphate duplex coating in controlling the rate of degradation of Mg and improving its bioactivity using uncoated Mg and fluoride conversion coated Mg as reference. The findings of the study reveal that the magnesium fluoride-magnesium phosphate duplex coating could offer an excellent corrosion resistance and improve the bioactivity of Mg.

Effect of Washing Treatment on the Textural Properties and Bioactivity of Silica/Chitosan/TCP Xerogels for Bone Regeneration.

Silica/biopolymer hydrogel-based materials constitute very attractive platforms for various emerging biomedical applications, particularly for bone repair. The incorporation of calcium phosphates in the hybrid network allows for designing implants with interesting biological properties. Here, we introduce a synthesis procedure for obtaining silica–chitosan (CS)–tricalcium phosphate (TCP) xerogels, with CS nominal content varying from 4 to 40 wt.% and 10 to 20 wt.% TCP. Samples were obtained using the sol-gel process assisted with ultrasound probe, and the influence of ethanol or water as washing solvents on surface area, micro- and mesopore volume, and average pore size were examined in order to optimize their textural properties. Three washing solutions with different soaking conditions were tested: 1 or 7 days in absolute ethanol and 30 days in distilled water, resulting in E1, E7, and W30 washing series, respectively. Soaked samples were eventually dried by evaporative drying at air ambient pressure, and the formation of interpenetrated hybrid structures was suggested by Fourier transformed infrared (FTIR) spectroscopy. In addition the impact that both washing solvent and TCP content have on the biodegradation, in vitro bioactivity and osteoconduction of xerogels were explored. It was found that calcium and phosphate-containing ethanol-washed xerogels presented in vitro release of calcium (2–12 mg/L) and silicon ions (~60–75 mg/L) after one week of soaking in phosphate-buffered saline (PBS), as revealed by inductive coupled plasma (ICP) spectroscopy analysis. However, only the release of silicon was detected for water-washed samples. Besides, all the samples exhibited in vitro bioactivity in simulated body fluid (SBF), as well as enhanced in vitro cell growth and also significant focal adhesion development and maturation.

Mechanical Properties of Different Nanopatterned TiO2 Substrates and Their Effect on Hydrothermally Synthesized Bioactive Hydroxyapatite Coatings.

Nanotechnology is a very attractive tool for tailoring the surface of an orthopedic implant to optimize its interaction with the biological environment. Nanostructured interfaces are promising, especially for orthopedic applications. They can not only improve osseointegration between the implant and the living bone but also may be used as drug delivery platforms. The nanoporous structure can be used as a drug carrier to the surrounding tissue, with the intention to accelerate tissue–implant integration as well as to reduce and treat bacterial infections occurring after implantation. Titanium oxide nanotubes are promising for such applications; however, their brittle nature could be a significantly limiting factor. In this work, we modified the topography of commercially used titanium foil by the anodization process and hydrothermal treatment. As a result, we obtained a crystalline nanoporous u-shaped structure (US) of anodized titanium oxide with improved resistance to scratch compared to TiO2 nanotubes. The US titanium substrate was successfully modified with hydroxyapatite coating and investigated for bioactivity. Results showed high bioactivity in simulated body fluid (SBF) after two weeks of incubation.

Chitosan-GPTMS-Silica Hybrid Mesoporous Aerogels for Bone Tissue Engineering.

This study introduces a new synthesis route for obtaining homogeneous chitosan (CS)-silica hybrid aerogels with CS contents up to 10 wt%, using 3-glycidoxypropyl trimethoxysilane (GPTMS) as coupling agent, for tissue engineering applications. Aerogels were obtained using the sol-gel process followed by CO2 supercritical drying, resulting in samples with bulk densities ranging from 0.17 g/cm3 to 0.38 g/cm3. The textural analysis by N2-physisorption revealed an interconnected mesopore network with decreasing specific surface areas (1230–700 m2/g) and pore sizes (11.1–8.7 nm) by increasing GPTMS content (2–4 molar ratio GPTMS:CS monomer). In addition, samples exhibited extremely fast swelling by spontaneous capillary imbibition in PBS solution, presenting swelling capacities from 1.75 to 3.75. The formation of a covalent crosslinked hybrid structure was suggested by FTIR and confirmed by an increase of four hundred fold or more in the compressive strength up to 96 MPa. Instead, samples synthesized without GPTMS fractured at only 0.10–0.26 MPa, revealing a week structure consisted in interpenetrated polymer networks. The aerogels presented bioactivity in simulated body fluid (SBF), as confirmed by the in vitro formation of hydroxyapatite (HAp) layer with crystal size of approximately 2 µm size in diameter. In vitro studies revealed also non cytotoxic effect on HOB® osteoblasts and also a mechanosensitive response. Additionally, control cells grown on glass developed scarce or no stress fibers, while cells grown on hybrid samples showed a significant (p < 0.05) increase in well-developed stress fibers and mature focal adhesion complexes.

Preparation and characterization of sintered bioactive borate glass tape

Non-aqueous tape casting was used to prepare flexible green tapes from borate glass (1393B3) particles. The tapes were sintered at 550, 575, 600 °C: dense tapes were prepared at 600 °C. In-vitro bioactivity in simulated body fluid (SBF) of tapes sintered at different temperatures was evaluated. SEM, FTIR and XRD results showed slow degradation of dense borate glass tape in SBF compared to the non-dense tapes sintered at different temperatures. Formation of HCA (hydroxy carbonated apatite) on sample surfaces was confirmed after 7D in SBF.