Nd-induced honeycomb structure of intermetallic phase enhances the corrosion resistance of Mg alloys for bone implants.

Mg-5.6Zn-0.5Zr alloy (ZK60) tends to degrade too rapid for orthopedic application, in spite of its natural degradation, suitable strength and good biocompatibility. In this study, Nd was alloyed with ZK60 via laser melting method to enhance its corrosion resistance. The microstructure features, mechanical properties and corrosion behaviors of ZK60-xNd (x = 0, 1.8, 3.6, 5.4 wt.%) were investigated. Results showed that laser melted ZK60-xNd were composed of fine ɑ-Mg grains and intermetallic phases along grain boundaries. And the precipitated intermetallic phases experienced successive changes: divorced island-like MgZn phase → honeycomb-like T phase → coarsened and agglomerated W phase with Nd increasing. It was worth noting that ZK60-3.6Nd with honeycomb-like T phase exhibited an optimal corrosion behavior with a corrosion rate of 1.56 mm year-1. The improved corrosion behavior was ascribed to: (I) dense surface film caused by the formation of Nd2O3 hindered the invasion of immersion solution; (II) the three-dimensional honeycomb structure of intermetallic phases formed a tight barrier to restrain the propagation of corrosion. Moreover, ZK60-3.6Nd exhibited good biocompatibility. It was suggested that ZK60-3.6Nd was a preferable candidate for biodegradable bone implant.

Preparation and characterization of laser-melted Mg-Sn-Zn alloys for biomedical application.

The rapid degradation rate of Magnesium (Mg) alloy limits its biomedical application even though it possesses outstanding biological performance and biomechanical compatibility. In this study, a combined method of laser rapid melting and alloying Zinc (Zn) was proposed to decrease the degradation rate of Mg-Sn alloy. The microstructure, degradation behaviors and mechanical properties of the laser-melted Mg-5Sn-xZn (x = 0, 2, 4, 6 and 8 wt.%) alloys were investigated. The results indicated that the grain size of the alloys decreased with increasing Zn content, due to the increased number of nucleation particles formed in the process of solidification. Moreover, the laser-melted Mg-Sn alloys possessed finer grains compared with traditional as-cast and as-rolled Mg-Sn alloys. The degradation rate of the alloys decreased with increasing Zn content (0-4 wt.%), which was ascribed to the grain refinement and the formation of Zn(OH)2 protective layer. However, the degradation rate increased as the Zn content further increased (4-8 wt.%), which was caused by the galvanic corrosion between the Mg matrix and the generated Mg7Zn3 phase. Besides, Zn also increased the hardness of the alloys owing to the grain refinement strengthening and solid solution strengthening.

Functionalization of Calcium Sulfate/Bioglass Scaffolds with Zinc Oxide Whisker.

There are urgent demands for satisfactory antibacterial activity and mechanical properties of bone scaffolds. In this study, zinc oxide whisker (ZnOw) was introduced into calcium sulfate/bioglass scaffolds. Antimicrobial behavior was analyzed using Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). The results showed that the scaffolds presented a strong antibacterial activity after introducing ZnOw, due to the antibacterial factors released from the degradation of ZnO. Moreover, ZnOw was also found to have a distinct reinforcing effect on mechanical properties. This was ascribed to whisker pull-out, crack bridging, crack deflection, crack branching and other toughening mechanisms. In addition, the cell culture experiments showed that the scaffolds with ZnOw had a good biocompatibility.

Akermanite scaffolds reinforced with boron nitride nanosheets in bone tissue engineering.

Akermanite (AKM) is considered to be a promising bioactive material for bone tissue engineering due to the moderate biodegradability and excellent biocompatibility. However, the major disadvantage of AKM is the relatively inadequate fracture toughness, which hinders the further applications. In the study, boron nitride nanosheets (BNNSs) reinforced AKM scaffolds are fabricated by selective laser sintering. The effects of BNNSs on the mechanical properties and microstructure are investigated. The results show that the compressive strength and fracture toughness increase significantly with BNNSs increasing from 0.5 to 1.0 wt%. The remarkable improvement is ascribed to pull out and grain wrapping of BNNSs with AKM matrix. While, overlapping sheets is observed when more BNNSs are added, which results in the decline of mechanical properties. In addition, it is found that the composite scaffolds possess good apatite-formation ability when soaking in simulated body fluids, which have been confirmed by energy dispersed spectroscopy and flourier transform infrared spectroscopy. Moreover, MG63 osteoblast-like cells and human bone marrow stromal cells are seeded on the scaffolds. Scanning electron microscopy analysis confirms that both cells adhere and proliferate well, indicating favorable cytocompatibility. All the facts demonstrate the AKM scaffolds reinforced by BNNSs have potential applications for tissue engineering.

Nano SiO2 and MgO improve the properties of porous ß-TCP scaffolds via advanced manufacturing technology.

Nano SiO2 and MgO particles were incorporated into ß-tricalcium phosphate (ß-TCP) scaffolds to improve the mechanical and biological properties. The porous cylindrical ß-TCP scaffolds doped with 0.5 wt % SiO2, 1.0 wt % MgO, 0.5 wt % SiO2 + 1.0 wt % MgO were fabricated via selective laser sintering respectively and undoped ß-TCP scaffold was also prepared as control. The phase composition and mechanical strength of the scaffolds were evaluated. X-ray diffraction analysis indicated that the phase transformation from ß-TCP to α-TCP was inhibited after the addition of MgO. The compressive strength of scaffold was improved from 3.12 ± 0.36 MPa (ß-TCP) to 5.74 ± 0.62 MPa (ß-TCP/SiO2), 9.02 ± 0.55 MPa (ß-TCP/MgO) and 10.43 ± 0.28 MPa (ß-TCP/SiO2/MgO), respectively. The weight loss and apatite-forming ability of the scaffolds were evaluated by soaking them in simulated body fluid. The results demonstrated that both SiO2 and MgO dopings slowed down the degradation rate and improved the bioactivity of ß-TCP scaffolds. In vitro cell culture studies indicated that SiO2 and MgO dopings facilitated cell attachment and proliferation. Combined addition of SiO2 and MgO were found optimal in enhancing both the mechanical and biological properties of ß-TCP scaffold.

Liquid phase sintered ceramic bone scaffolds by combined laser and furnace.

Fabrication of mechanically competent bioactive scaffolds is a great challenge in bone tissue engineering. In this paper, ß-tricalcium phosphate (ß-TCP) scaffolds were successfully fabricated by selective laser sintering combined with furnace sintering. Bioglass 45S5 was introduced in the process as liquid phase in order to improve the mechanical and biological properties. The results showed that sintering of ß-TCP with the bioglass revealed some features of liquid phase sintering. The optimum amount of 45S5 was 5 wt %. At this point, the scaffolds were densified without defects. The fracture toughness, compressive strength and stiffness were 1.67 MPam1/2, 21.32 MPa and 264.32 MPa, respectively. Bone like apatite layer was formed and the stimulation for apatite formation was increased with increase in 45S5 content after soaking in simulated body fluid, which indicated that 45S5 could improve the bioactivity. Furthermore, MG-63 cells adhered and spread well, and proliferated with increase in the culture time.

Current progress in bioactive ceramic scaffolds for bone repair and regeneration.

Bioactive ceramics have received great attention in the past decades owing to their success in stimulating cell proliferation, differentiation and bone tissue regeneration. They can react and form chemical bonds with cells and tissues in human body. This paper provides a comprehensive review of the application of bioactive ceramics for bone repair and regeneration. The review systematically summarizes the types and characters of bioactive ceramics, the fabrication methods for nanostructure and hierarchically porous structure, typical toughness methods for ceramic scaffold and corresponding mechanisms such as fiber toughness, whisker toughness and particle toughness. Moreover, greater insights into the mechanisms of interaction between ceramics and cells are provided, as well as the development of ceramic-based composite materials. The development and challenges of bioactive ceramics are also discussed from the perspective of bone repair and regeneration.

A dual redox system for enhancing the biodegradability of Fe-C-Cu composite scaffold.

Fe-based biocomposites are emerging as temporary orthopedic implants due to natural biodegradability and high mechanical strength. Yet, the slow degradation kinetics restricts their biomedical applications. In this work, Cu-initiated redox system was established to accelerate the biodegradation of Fe-C composite scaffold prepared by selective laser melting. On the one hand, Cu induced micro-galvanic corrosion with Fe matrix due to their differences in potentials, accelerating the electron separation from Fe and further the dissolution of Fe matrix. On the other hand, Cu, as a good conductor of electron transfer, reduced the electron transfer impedance and increased the corrosion current density in Fe/C micro-galvanic cells. Consequently, the degradation rate of Fe-C scaffold was increased by 69% from 0.16 mm/y to 0.27 mm/y in the immersion tests. Additionally, the composite scaffold exhibited compression strength of 128 MPa and hardness of 148 HV, respectively. After co-culturing with the composite scaffold, MG-63 cells presented classical fusiform shape and good cell viability, indicating favorable biocompatibility. These results showed the potential applications of the developed redox systems as highly efficient initiator in accelerating the biodegradation of Fe-based biocomposites.

Dual-functional scaffolds of poly(L-lactic acid)/nanohydroxyapatite encapsulated with metformin: Simultaneous enhancement of bone repair and bone tumor inhibition.

Bone defects caused by tumors are difficult to repair clinically because of their poor morphology and residual tumor cell-induced recurrence. Scaffolds with the dual function of bone repair and bone tumor treatment are urgently needed to resolve this problem. In this study, a poly(L-lactic acid) (PLLA)/nanoscale hydroxyapatite (nHA)/metformin (MET) nanocomposite scaffold was constructed via selective laser sintering. The scaffolds were expected to combine the excellent mechanical strength and biodegradability of PLLA, the good bioactivity of nHA, and the water solubility and antitumor properties of MET. The PLLA/nHA/MET scaffolds showed improved cell adhesion, appropriate porosity, good biocompatibility and osteogenic-induced ability in vitro because metformin improves water solubility and promotes the osteogenic differentiation of cells within the scaffold. The PLLA/nHA/MET scaffold had an extended drug release time because the MET particles were wrapped in the biodegradable polymer PLLA and the wrapped MET particles were slowly released into body fluids as the PLLA was degraded. Moreover, the scaffold induced osteosarcoma (OS) cell apoptosis by upregulating apoptosis-related gene expression and showed excellent tumor inhibition characteristics in vitro. In addition, the scaffold induced osteogenic differentiation of bone marrow mesenchymal cells (BMSCs) by promoting osteogenic gene expression. The results suggest that the PLLA/nHA/MET composite scaffold has the dual function of tumor inhibition and bone repair and therefore it provides a promising new approach for the treatment of tumor-induced bone defects.

Interfacial reinforcement in bioceramic/biopolymer composite bone scaffold: The role of coupling agent.

The combination of biopolymer and bioceramic can mimic the chemical composition of the native bone extracellular matrix which is composed of inorganic minerals and organic collagenous. However, the poor interfacial compatibility between organic biopolymer and inorganic bioceramic restricts the full development of bioceramic/biopolymer composite scaffold for bone regeneration application. Coupling agents have been widely used to build a "molecular bridge" in the interface between biopolymer and bioceramic due to the two different functional groups in its structure. One is organophilic functional groups which can react with polymer molecules, and the other is special functional groups which can adsorb on bioceramic surface to form a firm bond. As a result, the stress transfer efficiency between biopolymer and bioceramic can be enhanced, and thereby improving the mechanical properties of the composite scaffold. In this study, the interfacial features between bioceramic and biopolymer and the methods to improve interface bonding were presented, and the interfacial reaction mechanisms under the action of coupling agents especially silane coupling agents were focused on discussing. In addition, the mechanical properties, in vitro and in vivo biological properties of the bioceramic/biopolymer composite scaffold after coupling agent modification were systematically summarized. Finally, suggestions for further work were put forward, including the study on controlling coupling agent content, and more in vitro and in vivo experimental evaluation.

TiO2-Induced In Situ Reaction in Graphene Oxide-Reinforced AZ61 Biocomposites to Enhance the Interfacial Bonding.

Graphene oxide (GO) can improve the degradation resistance of biomedical Mg alloy because of its excellent impermeability and outstanding chemical inertness. However, the weak interfacial bonding between GO and Mg matrix leads to easily detaching during degradation. In this study, in situ reaction induced by TiO2 took place in the AZ61-GO biocomposite to enhance the interfacial bonding between GO and Mg matrix. For the specific process, TiO2 was uniformly and tightly deposited onto the GO surface by hydrothermal reaction (TiO2/GO) first and then used for fabricating AZ61-TiO2/GO biocomposites by selective laser melting (SLM). Results showed that TiO2 was in situ reduced by magnesiothermic reaction during SLM process, and the reduzate Ti, on the one hand, reacted with Al in the AZ61 matrix to form TiAl2 and, on the other hand, reacted with GO to form TiC at the AZ61-GO interface. Owing to the enhanced interfacial bonding, the AZ61-TiO2/GO biocomposite showed 12.5% decrease in degradation rate and 10.1% increase in compressive strength as compared with the AZ61-GO biocomposite. Moreover, the AZ61-TiO2/GO biocomposite also showed good cytocompatibility because of the slowed degradation. These findings may provide guidance for the interfacial enhancement in GO/metal composites for biomedical applications.

Rod-like Eutectic Structure in Biodegradable Zn-Al-Sn Alloy Exhibiting Enhanced Mechanical Strength.

Zn alloy is recognized as a promising biodegradable metal for bone implant applications because of its good biocompatibility and moderate degradation rate. Nevertheless, the insufficient strength limits its applications. In this study, a rod-like eutectic structure was fabricated in Zn-Al-Sn alloy with the addition of Sn via selective laser melting. It was found that the Al-enriched phase nucleated primarily during cooling and caused the rapid precipitation of Zn. This inevitably consumed the liquid Zn and increased the ratio of Sn to Zn in the liquid phase, resulting in the formation of the eutectic, which was composed of the Sn-enriched phase and the Zn-enriched phase. More importantly, the coupled growth of the Sn-enriched and Zn-enriched phases and their volume differences together led to a rod-like morphology of the eutectic according to the volume fraction theory. Consequently, the yield and ultimate compressive strengths were enhanced to 180 ± 18.8 and 325 ± 29.6 MPa for the Zn-Al-2Sn alloy, respectively. This could be attributed to the pinning effect of the rod-like eutectic, which could block dislocation motion and result in dislocation pile-up, thereby conducing to the mechanical reinforcement. In addition, the Zn-Al-Sn alloy also exhibited good biocompatibility and increased degradation rate because of the enhanced galvanic corrosion. This study showed the potential of rod-like eutectic for the mechanical enhancement of the biodegradable Zn alloy.

In Situ Generation of Hydroxyapatite on Biopolymer Particles for Fabrication of Bone Scaffolds Owning Bioactivity.

Hydroxyapatite (HAP) can endow a biopolymer scaffold with good bioactivity and osteoconductive ability, while the interfacial bonding is fairly weak between HAP and biopolymers. In this study, HAP was in situ generated on poly(l-lactic acid) (PLLA) particles, and then they were used to fabricate a scaffold by selective laser sintering. Detailedly, PLLA particles were first functionalized by dopamine oxide polymerization, which introduced abundance active catechol groups on the particle surface, and subsequently, the catechol groups concentrated Ca2+ ions by chelation in a simulated body fluid solution, and then, Ca2+ ions absorbed PO43- ions through electrostatic interactions for in situ nucleation of HAP. The results indicated that HAP was homogeneously generated on the PLLA particle surface, and HAP and PLLA exhibited good interfacial bonding in the HAP/PLLA scaffolds. Meanwhile, the scaffolds displayed excellent bioactivity by inducing apatite precipitation and provided a good environment for human bone mesenchymal stem cell attachment, proliferation, and osteogenic differentiation. More importantly, the ingrowth of blood vessel and the formation of new bone could be stimulated by the scaffolds in vivo, and the bone volume fraction and bone mineral density increased by 44.44 and 41.73% compared with the pure PLLA scaffolds, respectively. Serum biochemical indexes fell within the normal range, which indicated that there was no harmful effect on the normal functioning of the body after implanting the scaffold.

Enhanced osteoinductivity and corrosion resistance of dopamine/gelatin/rhBMP-2-coated ß-TCP/Mg-Zn orthopedic implants: An in vitro and in vivo study.

Magnesium-based biomaterials are attracting increasingly more attention for orthopedic applications based on their appropriate mechanical properties, biodegradability, and favorable biocompatibility. However, the high corrosion rate of these materials remains to be addressed. In this study, porous ß-Ca3(PO4)2/Mg-Zn (ß-TCP/Mg-Zn) composites were fabricated via a powder metallurgy method. The ß-TCP/Mg-Zn composites with 6% porosity exhibited optimal mechanical properties, and thus, they were selected for surface modification. A novel dopamine/gelatin/recombinant human bone morphogenetic protein-2 (rhBMP-2) coating with demonstrated stability was prepared to further improve the corrosion resistance of the composite and enhance early osteoinductivity. The homogeneously coated ß-TCP/Mg-Zn composite showed significantly improved corrosion resistance according to electrochemical and immersion tests. In addition, extracts from the dopamine/gelatin/rhBMP-2-coated ß-TCP/Mg-Zn composite not only facilitated cell proliferation but also significantly enhanced the osteogenic differentiation of Sprague-Dawley rat bone marrow-derived mesenchymal stem cells in vitro. Furthermore, in vivo experiments were performed to evaluate the biodegradation, histocompatibility, and osteoinductive potential of the coated composite. No obvious pathological changes in the vital visceral organs were observed after implantation, and radiography and hematoxylin-eosin staining showed strong promotion of new bone formation, matched composite degradation and bone regeneration rates, and complete absorption of the released hydrogen gas. Collectively, these results indicate that the dopamine/gelatin/rhBMP-2-coated ß-TCP/Mg-Zn composite offers improved corrosion resistance, favorable biocompatibility, and enhanced osteoinductive potential for use in the fabrication of orthopedic implants.

Characterizations and interfacial reinforcement mechanisms of multicomponent biopolymer based scaffold.

It is difficult for a single component biopolymer to meet the requirements of scaffold at present. The development of multicomponent biopolymer based scaffold provides an effective method to solve the issue based on the advantages of each kind of the biomaterials. However, the compatibility between different components might be very poor due to the difficulties in forming strong interfacial bonding, and thereby significantly degrading the integrated mechanical properties of the scaffold. In recent years, interface phase introduction, surface modification and in situ growth have been the major strategies for enhancing interfacial bonding. This article presents a comprehensive overview on the research in the area of constructing multicomponent biopolymer based scaffold and reinforcing their interfacial properties, and more importantly, the interfacial bonding mechanisms are systematically summarized. Detailly, interface phase introduction can build a bridge between biopolymer and other components to form strong interface bonding with the two phases under the action of interface phase. Surface modification can graft organic molecules or polymers containing functional groups onto other components to crosslink with biopolymer. In situ growth can directly in situ synthesize other components with the action of nucleating agent serving as an adherent platform for the nucleation and growth of other components to biopolymer surface by chemical bonding. In addition, the mechanical properties (including strength and modulus) and biological properties (including bioactivity, cytocompatibility and biosensing in vitro, and tissue compatibility, bone regeneration capacity in vivo) of multicomponent biopolymer based scaffold after interfacial reinforcing are also reviewed and discussed. Finally, suggestions for further research are given with highlighting the need for specific investigations to assess the interface formation, structure, properties, and more in vivo studies of scaffold before applications.

Ag-Introduced Antibacterial Ability and Corrosion Resistance for Bio-Mg Alloys.

Bone implants are expected to possess antibacterial ability and favorable biodegradability. Ag possesses broad-spectrum antibacterial effects through destroying the respiration and substance transport of bacteria. In this study, Ag was introduced into Mg-3Zn-0.5Zr (ZK30) via selective laser melting technology. Results showed that ZK30-Ag exhibited a strong and stable antibacterial activity against the bacterium Escherichia coli. Moreover, the degradation resistance was enhanced due to the comprehensive effect of positive shifted corrosion potential (from -1.64 to -1.53 V) and grains refinement. The positive shifted corrosion potential reduced the severe galvanic corrosion by lowering the corrosion potential difference between the matrix and the second phase. Meanwhile, the introduction of Ag caused the grain refinement strengthening and precipitated-phase strengthening, resulting in improved compressive yield strength and hardness. Furthermore, ZK30-0.5Ag exhibited good biocompatibility. It was suggested that Ag-modified ZK30 was potential candidate for bone implants.

A combined strategy to enhance the properties of Zn by laser rapid solidification and laser alloying.

The orthopedic application of Zn is limited owing to the poor strength and low plasticity. In this study, a novel strategy by combining rapid solidification obtained by selective laser melting (SLM) and alloying with Mg was proposed to improve the mechanical properties of Zn. The microstructures, mechanical properties, as well as in vitro cytocompatibility of SLM processed Zn-xMg (x = 0-4 wt%) were studied systematically. Results shown that SLM processed Zn-xMg alloys consisted of fine equiaxed α-Zn grains with homogeneously precipitated Mg2Zn11 along grain boundaries. More importantly, the grains size of α-Zn was decreased from 104.4 ±â€¯30.4 µm to 4.9 ±â€¯1.4 µm with Mg increasing. And Mg mainly dissolved in α-Zn developing into supersaturated solid solution due to rapid solidification effect. As a consequence, the ultimate tensile strength and elongation were enhanced by 361% and 423%, respectively, with Mg containing up to 3 wt%. Meanwhile, alloying with Mg enhanced the corrosion resistance of Zn, with the degradation rate decreasing from 0.18 ±â€¯0.03 mm year-1 to 0.10 ±â€¯0.04 mm year-1. Furthermore, SLM processed Zn-xMg exhibited good biocompatibility. This research suggested that SLM processed Zn-3Mg alloy was a potential biomaterial for orthopedic applications.

Carbon nanotube, graphene and boron nitride nanotube reinforced bioactive ceramics for bone repair.

The high brittleness and low strength of bioactive ceramics have severely restricted their application in bone repair despite the fact that they have been regarded as one of the most promising biomaterials. In the last few years, low-dimensional nanomaterials (LDNs), including carbon nanotubes, graphene and boron nitride nanotubes, have gained increasing attention owing to their favorable biocompatibility, large surface specific area and super mechanical properties. These qualities make LDNs potential nanofillers in reinforcing bioactive ceramics. In this review, the types, characteristics and applications of the commonly used LDNs in ceramic composites are summarized. In addition, the fabrication methods for LDNs/ceramic composites, such as hot pressing, spark plasma sintering and selective laser sintering, are systematically reviewed and compared. Emphases are placed on how to obtain the uniform dispersion of LDNs in a ceramic matrix and maintain the structural stability of LDNs during the high-temperature fabrication process of ceramics. The reinforcing mechanisms of LDNs in ceramic composites are then discussed in-depth. The in vitro and in vivo studies of LDNs/ceramic in bone repair are also summarized and discussed. Finally, new developments and potential applications of LDNs/ceramic composites are further discussed with reference to experimental and theoretical studies. STATEMENT OF SIGNIFICANCE: Despite bioactive ceramics having been regarded as promising biomaterials, their high brittleness and low strength severely restrict their application in bone scaffolds. In recent years, low-dimensional nanomaterials (LDNs), including carbon nanotubes, graphene and boron nitride nanotubes, have shown great potential in reinforcing bioactive ceramics owing to their unique structures and properties. However, so far it has been difficult to maintain the structural stability of LDNs during fabrication of LDNs/ceramic composites, due to the lengthy, high-temperature process involved. This review presents a comprehensive overview of the developments and applications of LDNs in bioactive ceramics. The newly-developed fabrication methods for LDNs/ceramic composites, the reinforcing mechanisms and the in vitro and in vivo performance of LDNs are also summarized and discussed in detail.

Graphene oxide as an interface phase between polyetheretherketone and hydroxyapatite for tissue engineering scaffolds.

The poor bonding strength between biopolymer and bioceramic has remained an unsolved issue. In this study, graphene oxide (GO) was introduced as an interface phase to improve the interfacial bonding between polyetheretherketone (PEEK) and hydroxyapatite (HAP) for tissue engineering scaffolds. On the one hand, the conjugated structure of GO could form strong π-π stacking interaction with the benzene rings in PEEK. On the other hand, GO with a negatively charge resulting from oxygen functional groups could adsorb the positively charged calcium atoms (C sites) of HAP. Consequently, the dispersibility and compatibility of HAP in the PEEK matrix increased with increasing GO content up to 1 wt%. At this time, the compressive strength and modulus of scaffolds increased by 79.45% and 42.07%, respectively. Furthermore, the PEEK-HAP with GO (PEEK-HAP/GO) scaffolds possessed the ability to induce formation of bone-like apatite. And they could support cellular adhesion, proliferation as well as osteogenic differentiation. More importantly, in vivo bone defect repair experiments showed that new bone formed throughout the scaffolds at 60 days after implantation. All these results suggested that the PEEK-HAP/GO scaffolds have a promising potential for bone tissue engineering application.

Mechanical reinforcement of bioceramics scaffolds via fracture energy dissipation induced by sliding action of MoS2 nanoplatelets.

The inherent brittleness of bioceramics restricts their applications in load bearing implant, although they possess good biocompatibility and bioactivity. In this study, molybdenum disulfide nanoplatelets (MSNPs) were used to reinforce bioceramics (Mg2SiO4/CaSiO3) scaffolds fabricated by selective laser sintering (SLS). The fracture mode of scaffolds was transformed from transgranular to mixed trans- and intergranular. It could be explained that MSNPs could slide easily due to their weak interlayer van der Waals interactions and provide elastic deformation due to their high elastic modulus. Such sliding action and elastic deformation synergistically induced crack bridging, crack deflection, pull-out and break of MSNPs. Those effects effectively increased the fracture energy dissipation and strain capacity as well as changed the fracture mode, contributing to high fracture toughness and compression strength. Additionally, the scaffolds with MSNPs not only formed a bioactive apatite layer in simulated body fluid, but also supported cell adhesion and proliferation.