Scaffolds For Bone Tissue Regeneration Research Articles

Improved biomechanical behavior of 316L graded scaffolds for bone tissue regeneration produced by laser powder bed fusion

Graded lattice scaffolds based on rhombic dodecahedral (RD) elementary unit cell geometry were manufactured in 316L stainless steel (SS) by laser powder bed fusion (LPBF). Two different strategies based on varying strut thickness layer-by-layer in the building direction were adopted to obtain the graded scaffolds: a) decreasing strut size from core to edge to produce the dense-in (DI) structure and b) increasing strut size in the same direction to produce the dense-out (DO) structure. Both graded structures (DI and DO) were constructed with specular symmetry with respect to the central horizontal axis. Structural, mechanical, and biological characterizations were carried out to evaluate feasibility of designing appropriate biomechanical performances of graded scaffolds in the perspective of bone tissue regeneration. Results showed that mechanical behavior is governed by graded geometry, while printing parameters influence structural properties of the material such as density, textures, and crystallographic phases. The predominant failure mechanism in graded structures initiates in correspondence of thinner struts, due to high stress concentrations on strut junctions. Biological tests evidenced better proliferation of cells in the DO graded scaffold, which in turn exhibits mechanical properties close to cortical bone. The combined control of grading strategy, printing parameters and elementary unit cell geometry can enable implementing scaffolds with improved biomechanical performances for bone tissue regeneration.

Proliferation kinetics and mineralization properties of MC3T3‐E1 cells on whey protein isolate scaffolds for bone tissue regeneration

AbstractThe purpose of the study is to assess the influence of scaffold composition and properties on the cellular proliferation and scaffold mineralization on a whey protein isolate (WPI) scaffold. Scaffolds of varying concentrations of WPI, calcium chloride, and amylopectin are seeded with cells, and growth curves are constructed from cell density measurements following incubation. Non‐linear regression yields kinetic growth parameters which are compared for quantitative assessment of scaffold performance. Scaffolds show biocompatibility and the ability to sustain a culture for the length of the study. For up to 14 days, the data are well described by exponential growth. Thereafter, saturation behavior appears, and the data fit well to a sigmoidal model. The seeding efficiency improves with increasing WPI concentration, peaking at 5 mM CaCl2, and decreases with added amylopectin. The growth constant is almost independent of scaffold composition, with possible increases with added CaCl2 and amylopectin. The retardation constant is independent of composition. Scaffolds cultured in differentiation and mineralization conditions, shows development of a mineralized matrix both on acellular scaffold surfaces and in osteoblast cultures. The ability of the unmodified WPI gel surfaces to promote the growth and differentiation of a model preosteoblast provides valuable trends and concentration effects for further scaffold design.

EXPLOITING NOVEL 3D JELLYFISH COLLAGEN SPONGES FOR BONE TISSUE REGENERATION

Jellyfish collagens exhibit auspicious perspectives for tissue engineering applications primarily due to their outstanding compatibility with a wide range of cell types, low immunogenicity and biodegradability. Furthermore, derived from a non-mammalian source, jellyfish collagens reduce the risk of disease transmission, minimising therefore the ethical and safety concerns. The current study aims to investigate the potential of 3-dimensional jellyfish collagen sponges (3D-JCS) in promoting bone tissue regeneration.Both qualitative and quantitative analyses were performed in order to assess adhesion and proliferation of MC3T3 cells on 3D-JCL, as well as cell migration and bone-like ECM production. Histological and fluorescent dyes were used to stain mineral deposits (i.e. Alizarin Red S (ARS), Von Kossa, Tetracycline hydrochloride) while images were acquired using optical and confocal microscopy.Qualitative data indicated successful adhesion and proliferation of MC3T3 cells on the 3D-JCS as well as cell migration along with ECM production both on the inner and outer surface of the scaffolds. Moreover, quantitative analyses indicated a four-fold increase of ARS uptake between 2- and 3-dimensional cultures (N=3) as well as an eighteen-fold increase of ARS uptake for the 3D-JCS (N=3) when cultured in osteogenic conditions compared to control. This suggests the augmented osteogenic potential of MC3T3 cells when cultured on 3D-JCS. Nevertheless, the cell-mediated mineral deposition appeared to alter the mechanical properties of the jellyfish collagen sponges that were previously reported to exhibit low mechanical properties (compressive modulus: 1-2 kPa before culture).The biocompatibility, high porosity and pore interconnectivity of jellyfish collagen sponges promoted adhesion and proliferation of MC3T3 cells as well as cell migration and bone-like ECM production. Their unique features recommend the jellyfish collagen sponges as superior biomaterial scaffolds for bone tissue regeneration. Further studies are required to quantify the change in mechanical properties of the cell-seeded scaffolds and confirm their suitability for bone tissue regeneration. We predict that the 3D-JCS will be useful for future studies in both bone and bone-tendon interface regeneration.AcknowledgmentsThis research has been supported by a Medical Research Scotland Studentship award (ref: -50177-2019) in collaboration with Jellagen Ltd.

Advanced injectable hydrogels for bone tissue regeneration.

Diseases or defects of the skeleton are hazardous because of their specificity and intricacy. Bone tissue engineering has become an important area of research that offers promising new tools for making biomimetic hydrogels that can be used to treat bone diseases. New hydrogels with a distinctive 3D network structure, high water content, and functional capabilities are ranked among the most promising candidates for bone tissue engineering. This makes them helpful in treating cartilage injury, skull deformity, and arthritis. This review will briefly introduce the variety of biocompatible functional hydrogels used in cell culture and bone tissue regeneration. Many gel design concepts, such as crosslinking procedures, controlled release properties, and alternative bionic methodology, were stressed regarding injectable hydrogels to form bone tissue. Hydrogels manufactured from biocompatible materials are a promising option for minimally invasive surgery because of their adaptable physicochemical qualities, ability to fill irregularly shaped defect sites, and ability to grow hormones or release drugs in response to external stimuli. Also included in this overview is a quick rundown of the more practical designs employed in treating bone disorders. Essential details on injectable hydrogel scaffolds for bone tissue regeneration are described in this article.

Incorporation of strontium-containing bioactive particles into PEOT/PBT electrospun scaffolds for bone tissue regeneration

The combination of biomaterials and bioactive particles has shown to be a successful strategy to fabricate electrospun scaffolds for bone tissue engineering. Among the range of bioactive particles, hydroxyapatite and mesoporous bioactive glasses (MBGs) have been widely used for their osteoconductive and osteoinductive properties. Yet, the comparison between the chemical and mechanical characteristics as well as the biological performances of these particle-containing scaffolds have been characterized to a limited extent. In this work, we fabricated PEOT/PBT-based composite scaffolds incorporating either nanohydroxyapatite (nHA), strontium-containing nanohydroxyapatite (nHA_Sr) or MBGs doped with strontium ions up to 15 wt./vol% and 12,5 wt./vol% for nHA and MBG, respectively. The composite scaffolds presented a homogeneous particle distribution. Morphological, chemical and mechanical analysis revealed that the introduction of particles into the electrospun meshes caused a decrease in the fiber diameter and mechanical properties, yet maintaining the hydrophilic nature of the scaffolds. The Sr2+ release profile differed according to the considered system, observing a 35-day slowly decreasing release from strontium-containing nHA scaffolds, whereas MBG-based scaffolds showed a strong burst release in the first week. In vitro, culture of human bone marrow-derived mesenchymal stromal cells (hMSCs) on composite scaffolds demonstrated excellent cell adhesion and proliferation. In maintenance and osteogenic media, all composite scaffolds showed high mineralization as well as expression of Col I and OCN compared to PEOT/PBT scaffolds, suggesting their ability to boost bone formation even without osteogenic factors. The presence of strontium led to an increase in collagen secretion and matrix mineralization in osteogenic medium, while gene expression analysis showed that hMSCs cultured on nHA-based scaffolds had a higher expression of OCN, ALP and RUNX2 compared to cells cultured on nHA_Sr scaffolds in osteogenic medium. Yet, cells cultured on MBGs-based scaffolds showed a higher gene expression of COL1, ALP, RUNX2 and BMP2 in osteogenic medium compared to nHA-based scaffolds, which is hypothesized to lead to high osteoinductivity in long term cultures.

Zinc and Strontium-Substituted Bioactive Glass Nanoparticle/Alginate Composites Scaffold for Bone Regeneration.

The global population is growing older and entering an aging society. Aging results in severe tissue disorder and organ dysfunction. Bone-related injuries are particularly significant. The need for alternative bone replacement materials for human implants has grown over the past few decades. Alginate has the potential for use as a cell scaffold for bone tissue engineering due to its high bio-compatibility. To improve the bioactivity of alginate scaffolds, zinc- and strontium-containing sol-gel-derived bioactive glass nanoparticles (Zn-Sr-BGNPs) with sizes ranging from 100 to l40 nm were incorporated. Zn-Sr-BGNPs synthesized through the sol-gel process have a high sur-face-to-volume ratio, homogeneity, and purity, resulting in faster degradation. The therapeutic bivalent ions released from Zn-Sr-BGNPs strengthen the cell scaffold and improve the stimulation of the production and development of bone cells. Zn-Sr-BGNPs with different Zn to Si nominal ratios of 0, 1, and 1.5 were mixed with alginate in this research. The ratio of Zn in Zn-Sr-BGNPs and the ratio of Zn-Sr-BGNPs in scaffolds impact the pore size, swelling, and biological properties of synthesized composite scaffolds. The surface area and pore volume of a 1:1 1Zn-Sr-BGNP:Alg composite scaffold were 22.58 m2/g and 0.055 cm3/g, respectively. The incorporation of Zn-Sr-BGNPs improved the mechanical performance of the scaffolds up to 4.73 ± 0.48 MPa. The swelling rate decreased slightly from 2.12 (pure Alg) to 1.50 (1Zn-Sr-BGNP:Alg (1:1)). The 1Zn-Sr-BGNP:Alg (1:1) composite scaffold promoted bioactivity through apatite layer formation, increased bone cell proliferation via the dissolution products released from the scaffold, enhanced calcium deposition, and facilitated cell attachment. Thus, 1Zn-Sr-BGNP:Alg (1:1) composite scaffold is proposed as a possible artificial bone scaffold in bone tissue regeneration.

Composite PLGA–Nanobioceramic Coating on Moxifloxacin-Loaded Akermanite 3D Porous Scaffolds for Bone Tissue Regeneration

Silica-based ceramics doped with calcium and magnesium have been proposed as suitable materials for scaffold fabrication. Akermanite (Ca2MgSi2O7) has attracted interest for bone regeneration due to its controllable biodegradation rate, improved mechanical properties, and high apatite-forming ability. Despite the profound advantages, ceramic scaffolds provide weak fracture resistance. The use of synthetic biopolymers such as poly(lactic-co-glycolic acid) (PLGA) as coating materials improves the mechanical performance of ceramic scaffolds and tailors their degradation rate. Moxifloxacin (MOX) is an antibiotic with antimicrobial activity against numerous aerobic and anaerobic bacteria. In this study, silica-based nanoparticles (NPs) enriched with calcium and magnesium, as well as copper and strontium ions that induce angiogenesis and osteogenesis, respectively, were incorporated into the PLGA coating. The aim was to produce composite akermanite/PLGA/NPs/MOX-loaded scaffolds through the foam replica technique combined with the sol-gel method to improve the overall effectiveness towards bone regeneration. The structural and physicochemical characterizations were evaluated. Their mechanical properties, apatite forming ability, degradation, pharmacokinetics, and hemocompatibility were also investigated. The addition of NPs improved the compressive strength, hemocompatibility, and in vitro degradation of the composite scaffolds, resulting in them keeping a 3D porous structure and a more prolonged release profile of MOX that makes them promising for bone regeneration applications.

3D bioprinting of human mesenchymal stem cells-laden hydrogels incorporating MXene for spontaneous osteodifferentiation

Contemporary advances in three-dimensional (3D) bioprinting technologies have enabled the fabrication of tailored live 3D tissue mimetics. Furthermore, the development of advanced bioink materials has been highlighted to accurately reproduce the composition of a native extracellular matrix and mimic the intrinsic properties of laden cells. Recent research has shown that MXene is one of promising nanobiomaterials with osteogenic activity for bone grafts and scaffolds due to its unique atomic structure of three titanium layers between two carbon layers. In this study, the MXene-incorporated gelatin methacryloyl (GelMA) and hyaluronic acid methacryloyl (HAMA) (i.e., GelMA/HAMA-MXene) bioinks were prepared to explore if they have the potential to enable the spontaneous osteodifferentiation of human mesenchymal stem cells (hMSCs) when the hMSCs-laden GelMA/HAMA-MXene bioinks were 3D printed. The physicochemical and rheological characteristics of the GelMA/HAMA-MXene hydrogels were proven to be unprecedentedly favorable supportive matrices suited for the growth and survival of hMSCs. Furthermore, hMSCs were shown to spontaneously differentiate into osteoblasts within GelMA-HAMA/MXene composites to provide favorable microenvironments for osteogenesis. Therefore, our results suggest that the remarkable biofunctional advantages of the MXene-incorporated GelMA/HAMA bioink can be utilized in a wide range of strategies for the development of effective scaffolds in bone tissue regeneration.

Bioactive 3D-printed chitosan-based scaffolds for personalized craniofacial bone tissue engineering

• 3D-printing of chitosan-based hydrogel • Increase in pore size and porosity was observed in the 3D-printed scaffolds containing hydroxyapatite. • Hydroxyapatite incorporation increased apatite formation and decreased the size of formed apatite crystals. • No considerable toxicity on MSCs was observed in 3D-printed scaffolds. Regeneration of craniofacial bone defects is a key issue in the bone regeneration field. Hence, novel treatment strategies, such as tissue engineering using porous scaffolds, have been developed. An ideal tissue-engineered scaffold for bone tissue regeneration should possess pores to facilitate nutrients transmission and support reparative tissue ingrowth, bioactivity for osteoconduction and osseointegration, and biocompatibility to improve cell attachment, proliferation, and extracellular matrix formation. In the present study, we manufactured chitosan-based hydrogels substituted with alginate with optimized properties by extrusion-based three-dimensional (3D) printing. 3D printing of the scaffolds enables the designing and developing of complex architectures for craniofacial reconstruction using computer-aided design (CAD). Different ratios (2.5, 5, and 10%) of hydroxyapatite were added to the hydrogel, printed, and subsequently lyophilized to augment the physical and biological characteristics of the scaffolds. Hydroxyapatite incorporation into the chitosan-based scaffolds increased the porosity and pore size of the printed scaffolds. In addition, the presence of hydroxyapatite amplified apatite formation and decreased the size of formed apatite crystals. All the scaffold samples showed biocompatible properties and did not have toxicity toward rat bone marrow mesenchymal stem cells. Furthermore, the scaffolds containing 5% w/V hydroxyapatite exhibited significant growth in cell viability compared to the control. Overall, it is concluded that chitosan-based scaffolds adorned with hydroxyapatite are considerable for regenerating craniofacial bone defects. Graphical Abstract:

Heterogeneous porous PLLA/PCL fibrous scaffold for bone tissue regeneration

Bone tissue engineering has become one of the most promising therapeutic methods to treat bone defects. A suitable scaffolding material to regenerate new bone tissues should have a high specific surface area, high porosity and a suitable surface structure which benefit cell attachment, proliferation, and differentiation. In this study, an acetone post-treatment strategy was developed to generate heterogeneous structure. After PLLA/PCL nanofibrous membranes were electrospun and collected, they were treated with acetone to generate a highly porous structure. Meanwhile, part of PCL was extracted from the fibre and enriched on the fibre surface. The cell affinity of the nanofibrous membrane was verified by human osteoblast-like cells assay. The proliferation rate of heterogeneous samples increased 190.4 %, 265.5 % and 137.9 % at day 10 compared with pristine samples. These results demonstrated that the heterogeneous PLLA/PCL nanofibrous membranes could enhance osteoblast adhesion and proliferation. With high surface area (average surface area 36.302 m2/g) and good mechanical properties (average Young's modulus 1.65 GPa and average tensile strength 5.1 MPa), the heterogeneous PLLA/PCL membrane should have potential applications in the field of bone regeneration.

Microfluidic-templated cell-laden microgels fabricated using phototriggered imine-crosslinking as injectable and adaptable granular gels for bone regeneration.

Injectable granular gels consisting of densely packed microgels serving as scaffolding biomaterial have recently shown great potential for applications in tissue regeneration, which allow administration via minimally invasive surgery, on-target cargo delivery, and high efficiency in nutrient/waste exchange. However, limitations such as insufficient mechanical strength, structural integrity, and uncontrollable differentiation of the encapsulated cells in the scaffolds hamper their further applications in the biomedical field. Herein, we developed a new class of granular gels via bottom-up assembly of cell-laden microgels via photo-triggered imine-crosslinking (PIC) chemistry based on the microfluidic technique. The particulate nature of the granular gels rendered them with shear-thinning and self-healing behavior, thereby functioning as an injectable and adaptable cellularized scaffold for bone tissue regeneration. Specifically, single cell-laden, monodisperse microgels composed of methacrylate- and o-nitrobenzene-functionalized hyaluronic acid and gelatin were prepared using a high-throughput microfluidic technique with a production rate up to 3.7×108 microgels/hr, wherein the PIC chemistry alleviated the oxygen inhibition on free-radical polymerization and facilitated enhanced fabrication accuracy, accelerated gelation rate, and improved network strength. Further in vitro and in vivo studies demonstrated that the microgels can serve as carriers to support the activity of the encapsulated mesenchymal stem cells; these cell-laden microgels can also be used as cellularized bone fillers to induce the regeneration of bone tissues as evidenced by the in vivo experiment using the rat femoral condyle defect model. In general, these results represent a significant step toward the precise fabrication of engineered tissue mimics with single-cell resolution and high cell-density and can potentially offer a powerful tool for the design and applications of a next generation of tissue engineering strategy. STATEMENT OF SIGNIFICANCE: Using microfluidic droplet-based technology, we hereby developed a new class of injectable and moldable granular gels via bottom-up assembly of cell-laden microgels as a versatile platform for tissue regeneration. Phototriggered imine-crosslinking chemistry was introduced for microgel cross-linkage, which allowed for the fabrication of microgels with improved matrix homogeneity, accelerated gelation process, and enhanced mechanical strength. We demonstrated that the microgel building blocks within the granular gels facilitated the proliferation and differentiation of the encapsulated mesenchymal stem cells, which can further serve as a cellularized scaffold for the treatment of bone defects.

Morphological and Mechanical Study of Gelatin/Hydroxyapatite Composite based Scaffolds for Bone Tissue Regeneration

<p>Gelatin-Hydroxyapatite (GHA) composite has been synthesized as a scaffold in bone tissue engineering. The purpose of this study was to find the optimal composition of the GHA scaffold composite which has the best mechanical properties. The independent variable in this study was the composition of HAp. Hydroxyapatite was synthesized by precipitation method from Ca(OH)<sub>2</sub> and (NH<sub>4</sub>)<sub>2</sub>HPO<sub>4</sub> as raw materials. Scaffold from GHA Composite was made by freeze-drying technique with freezing time for 8 hours at -80º C and drying with lyophilizer. The results were characterized using XRD, optical microscopy and tested for compressive strength. The results of the XRD showed that there was no change in a compound or the formation of new bonds on the GHA scaffold when it became a composite which was indicated by the absence of new peaks. It is also known that the peaks decrease in intensity as the amount of polymer in the composite increases. The highest degree of crystallinity was found in the 1:3 GHA sample because it had the highest concentration of HAp. The results of observations with an optical microscope showed that the most homogeneous pore surface morphology was GHA 1:2 with an average pore size of 225.12 ± 16.57 μm. From the results of the compressive strength test, the best value for the 1:2 GHA scaffold was 18.1 ± 0.61 MPa. The values obtained by this scaffold are following the minimum requirements for canceled scaffold so that it can be used as a scaffold candidate in bone tissue engineering.</p>

In vitro and in vivo evaluation of biomimetic hydroxyapatite/whitlockite inorganic scaffolds for bone tissue regeneration

Native bone tissue can be formed by developing collagen fibrils coated with hydroxyapatite (HA) and whitlockite (WH) nanoparticles after mineralization. WH has attracted much attention as the second most abundant bone mineral in human bones. It has a negatively charged surface, which can adsorb osteogenesis-related proteins such as bone sialoprotein in vivo, thus having a stronger possibility to induce osteogenesis. However, due to its poor thermodynamic stability and intermediate phases, the preparation of WH is relatively tricky, so WH inorganic scaffolds are still rarely studied. Therefore, this study explored the preparation of WH inorganic scaffolds using the hydrothermal method and prepared pure inorganic WH scaffolds. The prepared scaffolds exhibited apparent WH crystal phases in the x-ray powder diffraction (XRD) characterization. In the scanning electron microscopy (SEM) images, the WH scaffolds had an apparent hexagonal crystal form, which had a pronounced effect on promoting cell proliferation and differentiation in vitro experiments compared to the HA and HA/WH scaffolds. Furthermore, the scaffolds were used to verify the osteogenic properties of subcutaneous ectopic osteogenesis or repair of the calvarial defect in vivo and proved that the WH inorganic scaffolds have an excellent synergistic osteogenic ability.

Synthesis and characterization of a bioactive scaffold for bone tissue regeneration based on poly (vinylidene fluoride) (PVDF)

Synthesis and characterization of a bioactive scaffold for bone tissue regeneration based on poly (vinylidene fluoride) (PVDF)

Controlled Structure of Polyester/Hydroxyapatite Microparticles Fabricated via Pickering Emulsion Approach.

Biodegradable polyester/hydroxyapatite microparticles are widely proposed as microcarriers for drug/cell delivery or scaffolds for bone tissue regeneration. The current research implements the surfactant-free approach for the fabrication of polyester-based microparticles filled with hydroxyapatite nanoparticles (nHA) via the oil/water Pickering emulsion solvent evaporation technique for the first time, to the best of our knowledge. The process of polyester microparticle fabrication using nHA for the oil/water interface stabilization was studied as a function of phase used for nHA addition, which allows the preparation of a range of microparticles either filled with nHA or having it as a shell over the polymeric core. The effect of processing conditions (polymer nature, polymer/nHA ratio, ultrasound treatment) on particles’ total yield, size distribution, surface and volume morphology, and chemical structure was analyzed using SEM, EDX, Raman spectroscopy, and mapping. Addition of nHA either within the aqueous or oil phase allowed the effective stabilization of the oil/water interface without additional molecular surfactants, giving rise to hybrid microparticles in which total yield, size distribution, and surface morphology depended on all studied processing conditions. Preliminary ultrasound treatment of any phase before the emulsification process led to a complex effect but did not affect the homogeneity of nHA distribution within the polymeric core of the hybrid microparticles.

Robocasting and Laser Micromachining of Sol-Gel Derived 3D Silica/Gelatin/β-TCP Scaffolds for Bone Tissue Regeneration.

The design and synthesis of sol-gel silica-based hybrid materials and composites offer significant benefits to obtain innovative biomaterials with controlled porosity at the nanostructure level for applications in bone tissue engineering. In this work, the combination of robocasting with sol-gel ink of suitable viscosity prepared by mixing tetraethoxysilane (TEOS), gelatin and β-tricalcium phosphate (β-TCP) allowed for the manufacture of 3D scaffolds consisting of a 3D square mesh of interpenetrating rods, with macropore size of 354.0 ± 17.0 μm, without the use of chemical additives at room temperature. The silica/gelatin/β-TCP system underwent irreversible gelation, and the resulting gels were also used to fabricate different 3D structures by means of an alternative scaffolding method, involving high-resolution laser micromachining by laser ablation. By this way, 3D scaffolds made of 2 mm thick rectangular prisms presenting a parallel macropore system drilled through the whole thickness and consisting of laser micromachined holes of 350.8 ± 16.6-micrometer diameter, whose centers were spaced 1312.0 ± 23.0 μm, were created. Both sol-gel based 3D scaffold configurations combined compressive strength in the range of 2–3 MPa and the biocompatibility of the hybrid material. In addition, the observed Si, Ca and P biodegradation provided a suitable microenvironment with significant focal adhesion development, maturation and also enhanced in vitro cell growth. In conclusion, this work successfully confirmed the feasibility of both strategies for the fabrication of new sol-gel-based hybrid scaffolds with osteoconductive properties.

Generation of graphene oxide and nano-bioglass based scaffold for bone tissue regeneration

Graphene oxide (GO) offers a distinct opportunity in the field of biomedical engineering owing to its exceptionally high mechanical strength, excellent electrical conductivity, high optical transparency, and favorable biocompatibility. In this article, nanocomposite biocompatible GO-based scaffolds (chitosan/gelatin/nanobioglass/GO) Ch-G-NBG-GO were successfully fabricated through freeze drying technique (−40 °C) and evaluated for various physico-chemical and biological properties. The prepared Ch-G-NBG-GO composites have been investigated for their structural, physiochemical, and surface morphology via x-ray diffraction (XRD), high resolution scanning electron microscope, Fourier transform infrared spectroscopy, thermogravimetric analysis (TGA), energy-dispersive x-ray Spectroscopy and, differential scanning colorimetry (DSC) respectively. The morphological analysis showed the porous interconnected network of scaffold formed. Average pore size for the Ch-G-NBG-GO scaffolds were in between 90 and 120 μm, which was very close to the control scaffolds. XRD data revealed the successful incorporation of NBG and GO and distribution across the scaffolds. Porosity of the fabricated scaffolds were in the range between 75.3% and 77.3% which was very close to the control scaffold with 79% porosity. The studies also reveal that after GO incorporation, the weight loss reduced (0.11 ± 0.02–0.095 ± 0.03), scaffolds were firmly stable at room temperature even after a long duration of 28 d. The crystallinity added to the scaffolds due to addition of GO nanoparticles improved the mechanical strength of these scaffolds. The compressive modulus changed from (5.7 to 8.51) MPa after GO addition. Swelling ratio changed drastically especially in case of Ch-NBG-90%GO (4.9 ± 0.04–4 ± 0.01). DSC and TGA data revealed the thermal stability of GO incorporated scaffolds due to the proper interaction between GO/NBG with chitosan-gelatin blend. The scaffold’s potential for bone tissue engineering was evaluated by testing its cytocompatibility for MG-63 cell line. It revealed suitable cell attachment and proliferation of cells compared to the Ch-G-NBG scaffold. MTT assay showed that Ch-G-NBG-GO scaffold below 90% GO concentration possess best biocompatibility. But in case of Ch-G-NBG-90%GO scaffold, the cell proliferation was reduced when compared to control scaffolds. Alkaline phosphatase activity suggested improved osteogenic differentiation of MG-63 cells over GO based scaffolds and this was due to the osteogenic potential of NBG and GO present in the scaffolds. Based on these results, the nano-biocomposite scaffold appears to have the potential for utilization in bone tissue restoration, replacement and regeneration.

Mechanochemical synthesis and cold sintering of mussel shell-derived hydroxyapatite nano-powders for bone tissue regeneration

According to the circular economy principles, processing routes aiming at reducing the natural resources consumption and the energy demand can be addressed as ‘green’. In this framework, mussel shells, a natural feedstock of calcium carbonate, were successfully transformed into nano-crystalline hydroxyapatite by mechanochemical synthesis at room temperature after mixing with a phosphoric acid solution. The as-synthesized powder was then consolidated up to 82 % relative density by cold sintering (600 MPa, 200 °C). The materials were fully investigated by physical, chemical and thermal characterization techniques. Cold-sintered samples were also subjected to biaxial flexural strength test, showing a flexural resistance of 23 MPa. Cell viability assessment revealed that cold sintered hydroxyapatite derived from mussel shells promotes faster adhesion and spreading of human bone marrow-derived mesenchymal stem cells, in comparison to a commercial hydroxyapatite sintered at 1050 °C. Therefore, cold-sintered mussel shells-derived hydroxyapatite can be a promising future candidate scaffold for bone tissue regeneration.

3D calcium silicophosphate porous scaffold: In vitro and in vivo response

The elderly population (65 years and older) is expected to increase from 524 million people in 2010 to 1.5 billion by 2050, with the corresponding increase in bone-related and joint damage problems. Many of these problems can be solved by using scaffolds for bone tissue regeneration, and material selection is a critical step to obtain satisfactory results. This selection is crucial for the cell division process, cell-cell communication pathways, nutrient transport and osteogenic differentiation. In this study, we designed a tridimensional porous ceramic scaffold composed of 85 wt%C2S – 15 wt%TCP by the polymer sponge replica method combined with ceramic slurry, and we analyzed its biocompatibility and osteoinductive capacity by in vitro and in vivo assays. The in vitro tests showed good biocompatibility because the cells that were seeded over the biomaterial had spread over the entire surface. The in vivo results showed no cytotoxicity signs at the implant site, and the percentages of defect closure and residual biomaterial, and the resorption rate, were adequate. All these results demonstrate that 85 wt%C2S – 15 wt%TCP bioceramics can be taken as potential bone substitutes to be employed for a range of medical applications.

Design Strategies and Biomimetic Approaches for Calcium Phosphate Scaffolds in Bone Tissue Regeneration.

Bone is a complex biologic tissue, which is extremely relevant for various physiological functions, in addition to movement, organ protection, and weight bearing. The repair of critical size bone defects is a still unmet clinical need, and over the past decades, material scientists have been expending efforts to find effective technological solutions, based on the use of scaffolds. In this context, biomimetics which is intended as the ability of a scaffold to reproduce compositional and structural features of the host tissues, is increasingly considered as a guide for this purpose. However, the achievement of implants that mimic the very complex bone composition, multi-scale structure, and mechanics is still an open challenge. Indeed, despite the fact that calcium phosphates are widely recognized as elective biomaterials to fabricate regenerative bone scaffolds, their processing into 3D devices with suitable cell-instructing features is still prevented by insurmountable drawbacks. With respect to biomaterials science, new approaches maybe conceived to gain ground and promise for a substantial leap forward in this field. The present review provides an overview of physicochemical and structural features of bone tissue that are responsible for its biologic behavior. Moreover, relevant and recent technological approaches, also inspired by natural processes and structures, are described, which can be considered as a leverage for future development of next generation bioactive medical devices.