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Highly porous scaffolds of Si 3 N 4 are fabricated by direct ink writing method (Robocasting) with a pattern of macroporous cavities of 650-700μm. Two different Si 3 N 4 ink compositions regarding the oxide sintering aids (namely, Y 2 O 3 , Al 2 O 3 , and SiO 2 ) are tried. Both inks reach solid volume fractions of ~0.40 with about 10-12wt% of polymeric additive content that imparts the necessary pseudoplastic characteristics. The printed structures are sintered under controlled N 2 atmosphere either in a conventional graphite furnace or by the spark plasma sintering technique. Skeleton of the scaffolds reaches densities above 95% of the theoretical value with ≈18-24% of linear shrinkage. Analysis of the crystalline phases, microstructure and mechanical properties are comparatively done for both compositions. The bioactivity of these structures is addressed by evaluating the ion release rate in simulated body fluid. In parallel, atomic force microscopy is used to determine the effect of the filaments surface roughness on protein adsorption (Bovine Serum Albumin) for assessing the potential application of 3D-Si 3 N 4 scaffolds in bone regeneration., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier B.V. All rights reserved.)

Osteosarcoma remains one of the most common malignant primary bone tumors. Post-surgical defect repair combined with tumor suppression remains a major clinical challenge. Investigations of alternative treatments for osteosarcoma, while promising, have led to multi-drug resistance. These constraints of common treatment strategies have triggered the need for new therapeutic candidates in bone cancer treatment. Chitosan, a common biopolymer utilized in bone and tissue engineering applications, has recently been studied as a pro-apoptotic agent in metastatic cell lines like breast cancer, but has not been utilized in bone cancer applications. In this study, chitosan was directly loaded onto HA disks to evaluate its in vitro release and effects on human fetal osteoblast (hFOB) and human osteosarcoma (MG-63) cell lines. It is hypothesized that the sustained release of chitosan will decrease osteosarcoma cell proliferation and enhance proliferation of osteoblast cells. Through morphological characterization and MTT assay analysis, chitosan showed no toxicity to human fetal osteoblast (hFOB) cells. Chitosan was also shown to decrease human osteosarcoma cell viability by up to 96% compared to control samples. This suggests a pro-apoptotic mechanism against osteosarcoma as well as the potential clinical application of chitosan as a drug candidate in ceramic scaffolds at tumor resected sites., Competing Interests: Declaration of competing interest The authors have no affiliation with any organization with a direct or indirect financial interest in the subject matter discussed in the manuscript., (Copyright © 2020 Elsevier B.V. All rights reserved.)

The development of highly biomimetic scaffolds in terms of composition and structures, to repair or replace damaged bone tissues, is particularly relevant for tissue engineering. This paper investigates a 3D printed porous scaffold containing aligned multi-walled carbon nanotubes (MWCNTs) and nano-hydroxyapatite (nHA), mimicking the natural bone tissue from the nanoscale to macroscale level. MWCNTs with similar dimensions as collagen fibres are coupled with nHA and mixed within a polycaprolactone (PCL) matrix to produce scaffolds using a screw-assisted extrusion-based additive manufacturing system. Scaffolds with different material compositions were extensively characterised from morphological, mechanical and biological points of views. Transmission electron microscopy and polarised Raman spectroscopy confirm the presence of aligned MWCNTs within the printed filaments. The PCL/HA/MWCNTs scaffold are similar to the nanostructure of native bone and shows overall increased mechanical properties, cell proliferation, osteogenic differentiation and scaffold mineralisation, indicating a promising approach for bone tissue regeneration., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Chitosan (CTS) and mesoporous calcium silicate (MCS) have been developed for bone defect healing; however, their bone regeneration capacity still does not satisfy the patients with bone diseases. Gadolinium (Gd) is accumulated in human bones, and plays a beneficial role in regulating cell performance and bone regeneration. We firstly constructed Gd-doped MCS/CTS (Gd-MCS/CTS) scaffolds by a lyophilization technology. The interconnected arrangement of CTS films lead to forming macropores by using ice crystals as templates during the lyophilization procedure, and the Gd-MCS nanoparticles dispersed uniformly on the macropore walls. The biocompatible chemical components and hierarchical pores facilitated the attachment and spreading of rat bone marrow-derived mesenchymal stem cells (rBMSCs). Interestingly, the Gd dopants in the scaffolds effectively activated the Wnt/β-catenin signaling pathway, resulting in excellent cell proliferation and osteogenic differentiation capacities. The osteogenic-related genes such as alkaline phosphatase (ALP), runt-related transcription factor 2 (Runx2) and collagen type1 (COL-1) were remarkably up-regulated by Gd-MCS scaffolds as compared with MCS scaffolds, and their expression levels increased in a positive correlation with Gd doping amounts. Moreover, in vivo rat cranial defect tests further confirmed that Gd-MCS/CTS scaffolds significantly stimulated collagen deposition and new bone formation. The exciting finding suggested the beneficial effects of Gd 3+ ions on osteogenic differentiation and new bone regeneration, and Gd-MCS/CTS scaffolds can be employed as a novel platform for bone defect healing., (Copyright © 2019 Elsevier B.V. All rights reserved.)

There still remains a need for new methods of healing large bone defects, i.e., gaps in bone tissue that are too big to naturally heal. Bone regrowth scaffolds can fill the bone gap and enhance the bone regeneration by providing cells with a support to for new tissue formation. Coating of the scaffolds surface with nanocrystalline hydroxyapatite may enhance the osteoinductivity or osteoconductivity of such scaffolds. Here we present the sonocoating method to coat scaffolds with bioactive hydroxyapatite nanoparticles. We show a method, where the material to be coated is immersed in a colloidal suspension of nanoparticles with mean sizes of 10 nm and 43 nm in water, and high-power ultrasound waves are applied to the suspension for 15 min at 30 °C. High power ultrasounds lead to growth of cavitation bubbles in liquid, which implode at a critical size. The implosion energy propels the nanoparticles towards the material surface, causing their attachment to the scaffold. Using this technique, we produced a uniform layer of nanohydroxyapatite particles of thickness in the range 200 to 300 nm on two types of scaffolds: a porous β-TCP ceramic scaffold and a 3D-printed scaffold made of PCL fibers. In vivo tests in rabbits confirmed that the novel coating strongly stimulated new bone tissue formation, with new bone tissue occupying 33% for the nHAP-coated PCL scaffold and 68% for the nHAP-coated β-TCP after a 3-month test. The sonocoating method leads to formation of a bioactive layer on the scaffolds at temperature close to room temperature, very short time and in water. It is a green technological process, promising for bone tissue regeneration applications., (Copyright © 2019. Published by Elsevier B.V.)

Multifunctional magnetic 3D scaffolds are recently of particular interest because of their applications in hyperthermia-based therapy and localized drug delivery beside of their basic properties to be applied in bone tissue regeneration. In the current study, a magnetic nanocomposite is designed and synthesized through a two-step synthesis strategy in which CoFe 2 O 4 nanoparticles are prepared via sol-gel combustion method and then they are coated through sol-gel method with Mg 2 SiO 4 . The characterization relates to the nanocomposite shows that Mg 2 SiO 4 -CoFe 2 O 4 is successfully synthesized and it has a core-shell structure. Then, 3D scaffolds are fabricated through polymer sponge technique from the nanocomposite. Physiochemical and biological properties of the scaffolds are assessed in vitro amongst which bioactivity, biodegradability, mechanical properties, hyperthermia capability, controlled release potential, antibacterial activity, cell compatibility and attachment can be mentioned. The results demonstrate that the scaffolds have high porous structure with interconnected porosity and desirable mechanical properties close to cancellous bone. The magnetic scaffold is biodegradable and bioactive and exhibits controlled release of rifampin as an antibiotic drug up to 96 h. Moreover, in the exposure of different magnetic fields it has potential to produce heat for different kinds of hyperthermia-based therapies. The antibacterial activity of drug-loaded scaffold is assessed against S. aureus bacteria. The results suggest that Mg 2 SiO 4 -CoFe 2 O 4 nanocomposite scaffold with multiple capabilities has a great potential to be applied in the case of large bone defects which are caused by tumors to not only eradicate remained cancerous tissues, but also prevent infection after surgery and regenerate bone defect., (Copyright © 2019 Elsevier B.V. All rights reserved.)

This study prepares biodegradable bone scaffolds helping the recovery of damaged tibias of rats. Polyvinyl alcohol (PVA) plied yarns are fabricated into hollow braids. The braids are combined with hydroxyapatite (HA)/gelatin/PVA mixtures and processed using freeze-thawing and freeze-drying processes in order to form bone scaffolds. These bone scaffolds are observed by scanning electron scope (SEM) and tested for compression strength. Afterwards, recovery of damaged bone, the morphology of the bone, and the histological observation are evaluated. Results indicate a small amount of HA helps in enhancing the compressive strength of bone scaffolds. Results of in vivo assay indicate the damaged tibias of rats recover and function well eight weeks after the implantation, and exhibit a normal morphology. Histological observation confirms the bone scaffolds gradually decompose, allowing tissue infiltration and facilitating ossification. This study successfully produces bone scaffolds with satisfactory mechanical properties helping in the recovery of damaged tibias of rats., (Copyright © 2017 Elsevier B.V. All rights reserved.)

The present paper studies the physico-chemical, bioactivity and biological properties of hydroxyapatite (HA) which is derived from fish scale (FS) (FSHA) and compares them with those of synthesized HA (sHA) obtained by co-precipitation from chemical solution as a standard. The analysis shows that the FSHA is composed of flat-plate nanocrystal with a narrow width size of about 15-20 nm and having a range of 100 nm in length and that the calcium phosphate ratio (Ca/P) is 2.01 (Ca-rich CaP). Whereas, synthesized HA consists of sub-micron HA particle having a Ca/P ratio of 1.65. Bioactivity test shows that the FSHA forms more new apatite than does the sHA after being incubated in simulated body fluid (SBF) for 7 days. Moreover, the biocompatibility study shows a higher osteoblast like cell adhesion on the FSHA surface than on the sHA substrate after 3 days of culturing. Our results also show the shape of the osteoblast cells on the FSHA changes from being a rounded shape to being a flattened shape reflecting its spreading behavior on this surface. MTT assay and ALP analysis show significant increases in the proliferation and activity of osteoblasts over the FSHA scaffold after 5 days of culturing as compared to those covering the sHA substrates. These results confirm that the bio-materials derived from fish scale (FSHA) are biologically better than the chemically synthesized HA and have the potential for use as a bone scaffold or as regenerative materials., (Copyright © 2016. Published by Elsevier B.V.)

Several synthetic scaffolds are being developed using polymers, ceramics and their composites to overcome the limitations of auto- and allografts. Polymer-ceramic composites appear to be the most promising bone graft substitute since the natural bone itself is a composite of collagen and hydroxyapatite. Ceramics provide strength and osteoconductivity to the scaffold while polymers impart flexibility and resorbability. Natural polymers have an edge over synthetic polymers because of their biocompatibility and biological recognition property. But, very few natural polymer-ceramic composites are available as commercial products, and those few are predominantly based on type I collagen. Disadvantages of using collagen include allergic reactions and pathogen transmission. The commercial products also lack sufficient mechanical properties. This review summarizes the recent developments of biocomposite materials as bone scaffolds to overcome these drawbacks. Their characteristics, in vitro and in vivo performance are discussed with emphasis on their mechanical properties and ways to improve their performance., (Copyright © 2015 Elsevier B.V. All rights reserved.)

Bone scaffolds require a three-dimensional structure, high porosity, interconnected pores, adequate mechanical strengths, and non-toxicity. A high porosity is incongruent with mechanical strengths. Therefore, this study combines a braiding method and microsphere solution to create bone scaffolds with a high porosity and sufficient mechanical strengths. First, poly-L-lactide (PLLA) plied yarns are braided into 5-, 10-, 15-, 20-, and 25-layer hollow braids, and then thermally treated at 165 °C for various durations. Next, sodium alginate (SA) microspheres, cross-linked with CaCl2 solution with various concentrations, are combined with PLLA porous braided bone scaffolds to form PLLA/SA/CS microsphere hybrid scaffolds, which are then observed for surface observation, and tested for porosity, water contact angle, compressive strength, MTT assay, bioactivity, alkaline phosphatase (ALP) assay, cell attachment, and statistical analyses. The test results show that the layer amount of the bone scaffold is proportional to the compressive strength. With the same number of layers, the compressive strength is inversely proportional to the concentration of the CaCl2 solution. The results of surface observation, porosity, and water contact angle tests show that PLLA/SA/CS microsphere hybrid scaffolds possess a high porosity and good hydrophilicity; as a result, the braiding manufacture and the bonding technique effectively solve the confliction between porosity and mechanical strength. The concentration of CaCl2 does not pertain to cell activity and ALP results, exemplified by good cell attachment on bone scaffolds for each specification., (Copyright © 2015 Elsevier B.V. All rights reserved.)

Biphasic calcium phosphate (BCP), which is composed of hydroxyapatite [HAP, Ca10(PO4)6(OH)2] and β-tricalcium phosphate [β-TCP, β-Ca3(PO4)2], is usually difficult to densify into a solid state with selective laser sintering (SLS) due to the short sintering time. In this study, the sintering ability of BCP ceramics was significantly improved by adding a small amount of polymers, by which a liquid phase was introduced during the sintering process. The effects of the polymer content, laser power and HAP/β-TCP ratios on the microstructure, chemical composition and mechanical properties of the BCP scaffolds were investigated. The results showed that the BCP scaffolds became increasingly more compact with the increase of the poly(l-lactic acid) (PLLA) content (0-1 wt.%) and laser power (6-10 W). The fracture toughness and micro-hardness of the sintered scaffolds were also improved. Moreover, PLLA could be gradually decomposed in the late sintering stages and eliminated from the final BCP scaffolds if the PLLA content was below a certain value (approximately 1 wt.% in this case). The added PLLA could not be completely eliminated when its content was further increased to 1.5 wt.% or higher because an unexpected carbon phase was detected in the sintered scaffolds. Furthermore, many pores were observed due to the removal of PLLA. Micro-cracks and micro-pores occurred when the laser power was too high (12 W). These defects resulted in a deterioration of the mechanical properties. The hardness and fracture toughness reached maximum values of 490.3±10 HV and 1.72±0.10 MPa m(1/2), respectively, with a PLLA content of approximately 1 wt.% and laser power of approximately 10 W. Poly(l-lactic-co-glycolic acid) (PLGA) showed similar effects on the sintering process of BCP ceramics. Rectangular, porous BCP scaffolds were fabricated based on the optimum values of the polymer content and laser power. This work may provide an experimental basis for improving the mechanical properties of BCP bone scaffolds fabricated with SLS., (Copyright © 2013 Elsevier B.V. All rights reserved.)