Development of multiphase bioceramics from a filler-containing preceramic polymer

Multiphase bioceramics based on wollastonite and wollastonite/hydroxylapatite (W/HAp) have been successfully prepared by the heat treatment of a filler-containing preceramic polymer. CaO-bearing precursors (Ca-carbonate, Ca-acetate, and CaO nano-particles) were dispersed in a solution of silicone resin, subsequently dried and pyrolysed in nitrogen. The reaction between silica, deriving from the oxycarbide (SiOC) residue of the silicone resin, and CaO “active filler” led to the formation of several calcium silicates, mainly consisting of wollastonite (CaSiO₃), in both low and high temperature forms. The phase assemblage of the final ceramic varied with the pyrolysis temperature (varying from 1000 to 1200 °C). HAp was additionally inserted, as “passive filler” (i.e. not reacting with SiOC), for the preparation of bioceramics based on W/HAp mixtures.     

Polymer nanocomposites for bone tissue substitutes

Following the quest for new composite biomaterials for bone tissue engineering, this work presents the processing of new nanocomposite made of polycaprolactone matrix and wollastonite particles. Wollastonite nanopowder was obtained by thermal treatment of polymethyloxosilane resin mixed with silica and calcium hydroxide. Bioactive character of the ceramic nanopowder was verified in simulated body fluid (SBF). The apatite formation on wollastonite grain surface after immersion in SBF was observed. Basic mechanical properties of the samples containing various amount of ceramic nanoparticles have been examined. It was shown that the presence of small amount of wollastonite nanoparticles (0.5–1.0 wt%) improves significantly the Young's modulus, tensile strength, and work-of-fracture of polymer matrix composite. Increased content of ceramic nanoadditive (>2%) in nanocomposites resulted in degradation of their mechanical characteristics.     

Marine biological waste as a source of hydroxyapatite for bone tissue engineering applications

The demand for bone graft substitutes for orthopedics and dentistry is constantly growing due to the increase of ageing-related diseases. Synthetic hydroxyapatite (HA) is largely used as a bone graft material thanks to its biocompatibility, osteointegration, osteoconductive and osteoinductive properties and similarity to biological apatite, the main mineral component of bones and teeth. Biogenic apatite has gained attention due to its peculiar intrinsic characteristics: multi-doped ion composition and micro- and nano-scale architecture make natural-derived HA particularly promising for biomedical applications.At the same time, the growing interest in green materials is pushing towards the use of more sustainable biomaterials precursors, including re-use materials: marine waste, such as mollusk-shells, shellfish carapaces, cuttlefish bone, and fishbone have become widely studied sources of biogenic HA. Indeed, they are rich in calcium carbonate (CaCO₃), which can be converted into HA by environmentally sustainable processes. This allows the transformation of waste into valuable materials, while paying attention to the issues of sustainability and circular economy.In this review, we listed and discussed the methods to produce HA starting from shell-derived CaCO₃, describing all the steps and synthesis routes proposed for the conversion procedure, with a special focus on the different species of marine shells used. We discussed the use of HA alone or in combination with other materials (natural and synthetic polymers), used to enhance the mechanical and biological properties.We summarized the types of devices obtained by marine-derived HA, including nanorods, particulates and scaffolds and we described their in vitro and in vivo behavior.The up-to-date literature was summarized in tables with a special focus on the in vitro and in vivo biological evaluation of such materials.In conclusion, composite biomaterials based on marine-derived biogenic HA are reported as potential candidates for synthetic bone substitutes highlighting their potential, limitations and future perspectives.     

Electrophoretic deposition (EPD) of nanohydroxyapatite - nanosilver coatings on Ti13Zr13Nb alloy

Titanium and its alloys are the biomaterials most frequently used in medical engineering, especially as parts of orthopedic and dental implants. The surfaces of titanium and its alloys are usually modified to improve their biocompatibility and bioactivity, for example, in connection with the deposition of hydroxyapatite coatings.The objective of the present research was to elaborate the technology of electrophoretic deposition (EPD) of nanohydroxyapatite (nanoHAp) coatings decorated with silver nanoparticles (nanoAg) and to investigate the mechanical and chemical properties of these coatings as determined by EPD voltage and the presence of nanoAg. The deposition of nanoHAp was carried out at two voltage values, 15 and 30 V. The decoration of nanoHAp coatings with nanoAg was carried out using the EPD process at a voltage value of 60 V and a deposition time of 5 min. The thickness of the undecorated coatings was found to be 2.16 and 5.14 µm for applied EPD voltages of 15- and 30-V, respectively. The release rate of silver nanoparticles into an artificial saliva solution increased with exposure time and EPD voltage. The corrosion current, between 1 and 10 nA/cm², was significantly higher for undecorated nanoHAp coatings and close to that of the substrate for decorated nanoHAp coatings. The hardness of the undecorated nanoHAp coatings obtained at 15 and 30 V of EPD voltage attained 0.2245±0.036 and 0.0661±0.008 GPa, respectively. Resistance to nanoscratching was higher for thicker coatings. The wettability angle was lower for coatings decorated with nanoAg.     

Fabrication,characterization and cellular biocompatibility of porous biphasic calcium phosphate bioceramic scaffolds with different pore sizes

Facile wet-chemical methods are applied to synthesize hydroxyapatite and β-tricalcium phosphate nanoparticles, respectively. Porous biphasic calcium phosphate (BCP) bioceramic scaffolds are then fabricated using as-prepared HA and β-tricalcium phosphate nanoparticle powders. The macro pore diameter of BCP bioceramic scaffolds can be controlled by adjusting the amount of surfactants. The average diameter of the macro pores in BCP bioceramic scaffolds increases from 100 to 600 µm with the decrease amount of sodium dodecyl sulfate from 0.8 to 0.5 g, respectively. The BCP bioceramic scaffolds gradually degrade and the calcium-phosphate compounds fully deposit when soaking in simulated body fluid solution. Moreover, The BCP bioceramic scaffolds have outstanding biocompatibility to promote the cellular growth and proliferation of human dental pulp stem cells (hDPSCs). The hDPSCs also demonstrate favorable cellular adhering capacity on the pore surface of scaffolds, especially on the scaffolds with 100–200 µm pore diameter. The porous BCP bioceramic scaffold with inter-connected pore structure, outstanding in vitro cellular biocompatibility, favorable cell viability and adhesion ability will be a promising biomaterial for bone or dentin tissue regeneration.     

Studies on novel bioactive glasses and bioactive glass-nano-HAp composites suitable for coating on metallic implants

A series of novel zinc oxide (ZnO) containing bioactive glass compositions in SiO₂-Na₂O-CaO-P₂O₅ system and composite with hydroxyapatite (HAp) nano-particles were developed and applied as coating on Ti-6Al-4V substrates. The bioactive glasses and their composites were also processed to yield dense scaffolds, porous scaffolds and porous bone filler materials. The coating materials and the coatings were characterized and evaluated by different in vitro techniques to establish their superior mechanical properties. The cytotoxicity test of the coating material, porous and dense scaffolds and coated specimens showed non-cytotoxicity, biocompatibility and promising in vitro bioactivity for all tested samples. The dissolution behaviour studies of the bioactive glasses and the composites in simulated body fluid showed promising in vitro release pattern and bioactivity for all tested samples. Addition of nanosized HAp improves mechanical properties of the bioactive glass coating without affecting the in vitro bioactivity.     

Improvements in microstructural,mechanical, and biocompatibility properties of nano-sized hydroxyapatites doped with yttrium and fluoride

Hydroxyapatite was doped with Y³⁺ (2.5, 5 and 7.5 mol%) and F⁻ (2.5 mol%) ions (2.5YFHA, 5YFHA, 7.5YFHA, respectively) to compare its structural and mechanical properties and cellular response with pure-hydroxyapatite. No second phases were observed by X-ray diffraction spectra of 2.5YFHA. Doped hydroxyapatites had F⁻ bonds in addition to OH⁻ bonds. Hydroxyapatites sintered at 900 and 1100 °C were in nano-size. 7.5YFHA sintered at 1300 °C had the highest microhardness value. 2.5YFHA sintered at 1100 °C had the highest fracture toughness value. MTT viability assays showed high cell attachments on 2.5YFHA. Cell proliferation on 2.5YFHA and 5YFHA sintered at 1100 and 1300 °C was comparable with the control after 5-day culture. The highest ALP production and calcium deposition were observed on all hydroxyapatites sintered at 1100 °C. 2.5YFHA sintered at 1100 °C can be an alternative for hydroxyapatite in orthopedic applications.     

Effect of the fluoride content on the bioactivity of calcium silicate-based endodontic cements

This study was aimed at investigating the effect of the fluoride content (added as NaF) on the in vitro bioactivity of an experimental calcium silicate-based cement (wTC-Bi) obtained from white Portland cement. To this purpose, wTC-Bi and fluoride-doped wTC-Bi cements (i.e. FTC-Bi and F10TC-Bi with fluoride contents of 1% and 10% w/w, respectively) were aged in Dulbecco's Phosphate Buffered Saline (DPBS) and were comparatively analysed by micro-Raman and IR spectroscopy to investigate the presence of deposits on the surface of the cements and the composition changes of the cement as a function of the storage time. Commercial White ProRoot MTA was analyzed as reference.     

Fabrication of CaSiO3 bioceramics with open and unidirectional macro-channels using an ice/fiber-templated method

Porous CaSiO₃ bioceramics with open and unidirectional macro-channels of pore size more than 200 μm are of particular interest for biomedical applications. An ice/fiber-templated method was employed for the fabrication of CaSiO₃ bioceramics with interconnected lamellar pores and macro-channels of pore size more than 200 μm. The pores formed by ice crystals transformed from cellular to lamellar, while the pores formed by fibers were aligned macro-channels, which were also in alignment with the lamellar pores. Keeping the initial slurry concentration constant and increasing the packing density of fibers, the volume fraction of macro-channels and open porosity increased, and the compressive strength decreased. Maintaining the packing density of fibers and increasing the initial slurry concentration, the pore sizes of lamellar pores and open porosity decreased, and the compressive strength increased. The results indicated that it was possible to manufacture porous CaSiO₃ bioceramics with the macro-channels of 250–350 μm, lamellae spacing of 50–100 μm, open porosity of 71.12–83.94% and compressive strength of 0.87–3.59 MPa, indicating the suitability for tissue engineering.     

Porous boron nitride nanofibers/PVA hydrogels with improved mechanical property and thermal stability

Polyvinyl alcohol (PVA) hydrogel is a promising material possessing good chemical stability, high water absorption, excellent biocompatibility and biological aging resistant. However, the poor mechanical performance of PVA hydrogel limits its applications. Here we report the utilization of one-dimensional (1D) BN nanofibers (BNNFs) as nanofillers into PVA matrix to prepare a novel kind of BNNFs/PVA composite hydrogel via a cyclic freezing and thawing method. For comparison, the composite hydrogels using spherical BN nanoparticles i.e. BN nanospheres (BNNSs) as fillers were also prepared. The mechanical properties, thermal stabilities and swelling behaviors of the composite hydrogels were investigated in detail. Our study indicates that the mechanical properties of the hydrogels can be improved by adding of BNNFs. After loading of BNNFs into PVA with content of 0.5?wt%, the compressive strength of the composite hydrogel increases by 252% compared with that of pure PVA hydrogel. The tensile performance of BNNFs/PVA composite hydrogels has also been improved. Impressive 87.8% increases in tensile strengths can be obtained with 1?wt% BNNFs added. In addition, with the increase of BNNFs content, the thermal stability and the swelling ratio of hydrogels are increased gradually. The swelling ratio of hydrogel increases by 56.3% with only 1?wt% BNNFs added. In comparison, the improvement effects of the BNNS fillers on the mechanical strengths and swelling ratios are much weaker. The enhanced effects of BNNFs can be ascribed to the strong hydrogen bond interaction between BNNFs and PVA. The high aspect ratios of the nanofibers should also be took into account.     

Properties of calcium phosphates ceramic composites derived from natural materials

In this study, ceramics containing mixed phases of hydroxyapatite/beta-tricalcium phosphate (HA/β-TCP) were fabricated by a solid-state reaction technique. The HA powder was synthesized from cockle shells while the β-TCP powder was synthesized from egg shells. Pure HA and β-TCP fine powders were successfully obtained. The HA and β-TCP were mixed and subjected to a thermal treatment up to 1100 °C. To form the mixed phase ceramics, the resulting powders were sintered at 1350 °C. Effects of HA concentration on the properties of the studied ceramic were investigated. X-ray diffraction analysis revealed that all samples presented multiphase of calcium phosphate compounds. Average grain size of the ceramics decreased with the HA additive content. The 75 wt% HA ceramic showed the maximum hardness value (5.5 GPa) which is high when compared with many calcium phosphate ceramics. In vitro bioactivity test indicated that apatite forming increased with the HA additive content. To increase antibacterial activity, selected ceramics were coated with AgNO₃. Antibacterial test suggested that an Ag compound coating on the ceramics could improve the antibacterial ability of the studied ceramics. In addition, the antibacterial ability for the Ag coated ceramics depended on the porosity of the ceramics.     

One step method to synthesize flower-like hydroxyapatite architecture using mussel shell bio-waste as a calcium source

Mussel shell, a calcium-rich resource, is found plenty in nature. We have developed a novel and facile method to convert mussel shell bio-waste into hydroxyapatite (HAp) biomaterial using microwave irradiation with the aid of ethylenediaminetetraacetic acid (EDTA) as chelating agent. The obtained HAp had flower-like morphology which can be a potential candidate for developing biomaterial for orthopedic applications. Moreover, the developed method has the potential to recover the bio-waste and reduce environment pollution.     

Size and morphology-controlled synthesis of mesoporous hydroxyapatite nanocrystals by microwave-assisted hydrothermal method

We report the rapid microwave-assisted hydrothermal synthesis of mesoporous hydroxyapatite (HAp) nanocrystals with controlled size, morphology, and surface area using various organic modifiers as regulators. The products were analyzed for their crystalline nature, phase purity, morphology, particle size and pore size distribution. Results indicated that ascorbic acid, cetyltrimethyl ammonium bromide (CTAB) and polyvinylpyrrolidone (PVP) play an important role to obtain needle like, rod like and fiber like mesoporous HAp nanocrystals with different specific surface area by controlling growth habit of HAp along c-axis. In addition, the prepared samples were B-type carbonated HAp similar to bone minerals. Therefore, the present approach can be a promising way to obtain precursor for making tissue engineering scaffolds, drug/protein delivery carriers and bone fillers with tunable characteristics.     

Sodium dodecyl sulfate mediated microwave synthesis of biocompatible superparamagnetic mesoporous hydroxyapatite nanoparticles using black Chlamys varia seashell as a calcium source for biomedical applications

Designing biocompatible superparamagnetic mesoporous nanoparticles for advanced healthcare applications has received much attention. In this research, we have synthesized intrinsic mesoporous superparamagnetic hydroxyapatite (HAp) nanoparticles using bio-waste of black Chlamys varia seashell as a calcium source by sodium dodecyl sulfate (SDS)–enabled microwave-assisted synthesis approach. The synthesized Fe-doped HAp nanoparticles were characterized using various characterization techniques to know the phase purity and morphological features. The incorporation of Fe greatly affected the morphology of HAp nanoparticles without affecting their crystalline phase. Superparamagnetic behavior was observed with the incorporation of Fe in the HAp nanoparticles. Further, saturation magnetization was enhanced with higher incorporation of Fe ions. The cytotoxicity studies of the synthesized pure and Fe-doped HAp samples conducted using a human osteoblasts cell line (MG63), which indicated that Fe-doped HAp nanoparticles are biocompatible. Further, antibacterial activity analysis also confirmed their excellent antibacterial performance against different pathogens. Hence, SDS-enabled microwave-assisted synthesis approach using seashell as a calcium source would be a better approach for the production of intrinsic mesoporous superparamagnetic HAp nanoparticles for various biomedical applications, such as drug targeting, hyperthermia cancer therapy, and magnetic resonance imaging.     

Solution combustion synthesis of bioceramic calcium phosphates by single and mixed fuels—A comparative study

Calcium phosphate based bioceramics have been synthesized by a modified combustion synthetic route using both citric acid and succinic acid separately and in mixture as fuels and nitrate and nitric acid as oxidants. Calcium nitrate and diammonium hydrogen phosphate were used as calcium and phosphate sources. The effects of citric acid to succinic acid ratio on the phase formation have been investigated. The precursors and the calcined products have been characterized by powder X-ray diffraction, Fourier-transform infrared spectroscopy and scanning electron microscopy. Succinic acid has been used as a fuel for the first time to synthesize hydroxyapatite.     

Influence of concentration of hydroxyapatite surface modifier agent on bioactive composite characteristics

The characterization of chitosan – hydroxyapatite (CH – HAp) composite sponges prepared via freeze-drying methodology is reported in this study. Stearic acid (SA), added as a surface modifier of the HAp nanoparticles, induced changes in the TG/DTG results, particle size distribution and particle morphology. Composite sponges prepared with SA coated HAp demonstrated enhanced biocompatibility and structural properties, as compared to the composites prepared with uncoated HAp. SA coating modified the morphology of the composite, promoting a better dispersion of HAp particles within the composite sponges, and better homogeneity of the polymeric cover with HAp particles. The viability of the composites for cell culture applications was analyzed, and the results suggest that the sponges are biocompatible. Therefore, SA proved to be a good candidate for surface coating of HAp nanoparticles prevent agglomerations, and could be used effectively in the preparation of biocompatible composite sponges with chitosan.     

Preparation of the reticulated hydroxyapatite ceramics using carbon-coated polymeric sponge with elongated pores as a novel template

This paper proposes a novel, simple way to improve the compressive strength of reticulated porous hydroxyapatite (HA) ceramics using carbon-coated polymeric sponges with elongated pores as a novel template. This template allowed samples to have two interconnected pore networks with a preferential orientation, in which an addition pore network was newly formed by removing the carbon-coated polymeric struts, while preserving the pre-existing pore network. The compressive strength of the sample was as high as 2.9 ± 0.3 MPa with a porosity of 76% when tested parallel to the direction of pore elongation. In addition, the in vitro cell test using a pre-osteoblast cell line revealed the samples to have good biocompatibility.     

Cordierite ceramics from silicone resins containing nano-sized oxide particle fillers

Many silicates and alumino-silicates feature remarkable mechanical properties at high temperatures, low thermal expansion and high thermal shock resistance, optimum dielectric properties, etc. The poor interdiffusion, due to their characteristic partially covalent bonding however, greatly complicates the obtainment of dense and/or phase pure articles, by conventional sintering. The present paper concerns the realization of high-purity cordierite (2MgO·2Al₂O₃·5SiO₂) components by direct thermal treatment in air of preceramic polymers embedding suitable nano-sized oxide particles. More precisely, a selection of silicone resins allowed the obtainment of both dense and highly porous bodies.     

Structure of the hydroxyapatite plasma-sprayed coatings deposited on pre-heated titanium substrates

Plasma spraying is the most commonly used thermal spray method for the application of hydroxyapatite (HA, Ca₁₀(PO₄)₆(OH)₂) coatings. In the present study, the HA coatings were plasma spraying deposited onto plates of titanium pre-heated to 20 °C, 300 °C and 550 °C. The obtained HA coatings were investigated by means of X-ray diffraction and scanning electron microscopy. It is found that the coatings, in addition to HA, contain the tetracalcium phosphate (TTCP, (Ca₄(PO₄)₂O) phase (~10%) and a small amount of CaO (<2%). Crystal structure of HA in the coatings is revealed to be distorted. The PO4 tetrahedrons are deformed (Baur distortion coefficient D1(TO) ~0.2). The distances Ca1-O1 and Ca1-O2 are changed as compared to these in stoichiometric hydroxyapatite. These distortions are considered as a result of internal stresses, which are demonstrated in the broadening of peaks on X-ray diffraction pattern of HA. Microstructure of coatings consisting of flattened splats was formed by fully molten particles. The axial base texture was developed in the coatings. Ultrastructure is columnar with a preferred orientation of c-axes of the crystals parallel to the normal of plane coating n. The heating of substrate has a marked effect on the ultrastructure of coatings: the domain size increases from 790 to 1100 Å, the strain Δ decreases from 1.6·10^-3 to 1,2·10^–3, TTCP content diminishes from 12% to 7%. These results show that the effects due to heating of the substrate may be associated with partial recovery of HA microstructure.     

High thermally stable Mg-substituted tricalcium phosphate via precipitation

Tricalcium phosphates incorporating small amounts of Mg show attractive biological performances in terms of enhanced bone apposition, bone in-growth and cell-mediated degradation. A systematic investigation on Mg-stabilized β-TCP (β-tricalcium phosphate, β-Ca₃(PO₄)₂) is presented. Microstructure, composition and thermal behaviour were investigated by means of thermogravimetry and differential thermal analysis (TG-DTA), induced coupled plasma-atomic emission spectroscopy (ICP-AES), Fourier transform infrared spectroscopy (FT-IR), N₂ adsorption isotherms, X-ray diffraction (XRD and HT-XRD), and scanning electron microscopy (SEM). Pure and Mg-substituted tricalcium phosphate precursors consisted of calcium-deficient hydroxyapatite, the specific surface area being 128 m²/g and 87 m²/g, respectively. Tricalcium phosphate nanostructured powders were obtained by thermal treatment above 800 °C. The incorporation of Mg within the calcium phosphate lattice promoted the formation of the β-TCP phase at slightly lower temperature and resulted in the stabilization of the β-polymorph at high temperature (i.e. 1600 °C).