Hard Tissue Engineering Applications Research Articles

Achieving biomimetic porosity and strength of bone in magnesium scaffolds through binder jet additive manufacturing

Magnesium (Mg) alloys are a promising candidate for synthetic bone tissue substitutes. In bone tissue engineering, achieving a balance between pore characteristics that facilitate biological functions and the essential stiffness required for load-bearing functions is extremely challenging. This study employs binder jet additive manufacturing to fabricate an interconnected porous structure in Mg alloys that mimics the microporosity and mechanical properties of human cortical bone types. Using scanning electron microscopy, micro-computed tomography, and mercury intrusion porosimetry, we found that the binder jet printed and sintered (BJPS) MgZnZr alloys possess an interconnected porous structure, featuring an overall porosity of 13.3 %, a median pore size of 12.7 μm, and pore interconnectivity exceeding 95 %. The BJPS MgZnZr alloy demonstrated a tensile strength of ~130 MPa, a yield strength of ~100 MPa, an elastic modulus of ~21.5 GPa, and an ultimate compressive strength of ~349 MPa. These values align with the ranges observed in human bone types and outperform those of porous Mg alloys produced using the other conventional and additive manufacturing methods. Moreover, the BJPS MgZnZr alloy showed level 0 cytotoxicity with a greater MC3T3-E1 cell viability, attachment, and proliferation when compared to a cast MgZnZr counterpart, since the highly interconnected 3D porous structure provides cells with an additional dimension for infiltration. Finally, we provide evidence for the concept of using binder jet additive manufacturing for fabricating Mg implants tailored for applications in hard tissue engineering, including craniomaxillofacial procedures, bone fixation, and substitutes for bone grafts. The results of this study provide a solid foundation for future advancements in digital manufacturing of Mg alloys for biomedical applications.

Biomolecule-functionalized exfoliated-graphene and graphene oxide as heteronucleants of nanocrystalline apatites to make hybrid nanocomposites with tailored mechanical, luminescent, and biological properties

Nanocrystalline apatite (Ap), known for its exceptional biological properties, faces limitations in hard tissue engineering due to its poor mechanical properties. To overcome this limitation, we investigated the preparation of nanocomposites through heterogeneous nucleation of calcium phosphate on exfoliated graphene (G) and graphene oxide (GO) flakes, selected for their outstanding mechanical properties. The flakes were treated (functionalized) with amino acids of varying isoelectric points—namely L-Arginine (Arg), L-Alanine (Aln) and L-Aspartic acid (Asp)— as well as citrate (Cit) molecules. Furthermore, Tb3+ was incorporated into the formulations to introduce luminescence and further enrich the functionality of the composite. The synthesis was conducted using the sitting drop vapor diffusion method. Functionalized GO/Ap nanocomposites significantly improved roughness, adhesion forces and elastic modulus compared to Ap and G-based particles. GO-Asp-Ap-Tb nanocomposites exhibited the highest roughness (163.8 ± 116.2 nm), while G-Cit-Ap had the lowest (6.8 ± 5.6 nm). In terms of adhesion force, GO-Cit-Ap-Tb reached the highest value (31.06 ± 13.3 nN), while G-Arg-Ap had the lowest (3.7 ± 1.8 nN) compared to Ap (13.6 ± 3.2 nN). For the elastic modulus, GO-Aln-Ap-Tb demonstrated the greatest stiffness (3489 ± 101.01 MPa) compared to Ap (30.2 ± 6.5 MPa), while G-Aln-Ap-Tb showed the lowest (17.2 ± 8.4 MPa). Concerning their luminescence, regardless of G/Ap and GO/Ap, the relative luminescence intensities depended on the biomolecule used and decreased in the order Arg > Aln >Asp and Cit. Furthermore, G/Ap and GO/Ap nanocomposites demonstrated good biocompatibility on murine mesenchymal stem cells at low concentrations, showing cell viabilities exceeding 80% at 0.1 μg/mL. This research offers a novel approach to enhancing the mechanical properties of apatites while preserving their good biocompatibility properties and introducing new functionalities (i.e. luminescence) in the composites, thereby expanding their range of applications in hard tissue engineering.

Regulation of Osteogenic and Angiogenic Markers in Alkali Treated Titanium for Hard Tissue Engineering Applications.

Titanium (Ti) and Ti alloys are of great interest in bone and dental tissue engineering applications due to their biocompatibility, corrosion resistance, and close mechanical properties to natural bone. However, the formation of fibrous tissue prevents osteointegration and results in implant loosening. Thus, physical and chemical methods are used to improve the surface properties of Ti. This study aimed to understand the role of alkali treatment conditions, including alkali medium concentration, temperature, rotation speed, and post-heat treatment. Our results showed that alkali treatment using 5 and 10 molar sodium hydroxide solution allows the formation of web-like microstructure. However, a higher concentration of 15 molar resulted in cracks along the surface. Interaction between the human fetal osteoblast cells (hfOBs) and Ti samples showed that heat treatment is necessary for increased cellular proliferation, which was not significantly different at later time points compared to the polished Ti. Alkali heat treatment did not induce inflammatory reactions at later time points. It showed an increase in vascular endothelial growth factor, osteoprotegerin/nuclear factor kappa-В ligand ratio, and osteocalcin expression, which is evidence for accelerated osteoblast cell maturation and bone remodeling in surface-modified samples. Together, these data show that alkali treatment using 5 or 10 molar of NaOH followed by heat treatment may have therapeutic effect and assist with bone tissue integration with Ti implant.

The Story, Properties and Applications of Bioactive Glass “1d”: From Concept to Early Clinical Trials

Bioactive glasses in the CaO–MgO–Na2O–P2O5–SiO2–CaF2 system are highly promising materials for bone and dental restorative applications. Furthermore, if thermally treated, they can crystallize into diopside–fluorapatite–wollastonite glass-ceramics (GCs), which exhibit appealing properties in terms of mechanical behaviour and overall bone-regenerative potential. In this review, we describe and critically discuss the genesis, development, properties and applications of bioactive glass “1d” and its relevant GC derivative products, which can be considered a good example of success cases in this class of SiO2/CaO-based biocompatible materials. Bioactive glass 1d can be produced by melt-quenching in the form of powder or monolithic pieces, and was also used to prepare injectable pastes and three-dimensional porous scaffolds. Over the past 15 years, it was investigated by the authors of this article in a number of in vitro, in vivo (with animals) and clinical studies, proving to be a great option for hard tissue engineering applications.

Synergistic utilization of cost-effective glycerophosphate and biologically active zein for innovative minimally invasive smart thermo-responsive hydrogels for potential hard tissue engineering applications

Skeletal defects are the second-leading cause of disability worldwide, prompting the development of smart solutions for treatment. Calcium glycerophosphate (Ca–GP), chitosan (CS), hydroxyapatite (HA), and zein (ZN) were used to fabricate these thermo-responsive hydrogels. Ca–GP, an economically viable and bioactive glycerophosphate source, remains relatively underexplored. Natural protein ZN and the gold standard bone regenerative biomaterial HA were incorporated as reinforcing agents. The resulting composite hydrogels (HGs) exhibit a sol phase at 4 °C–10 °C and transition to gels at body temperature within 4–6 min. Their good injectability and the ability to be easily shaped into complex structures further support their great potential as minimally invasive solutions for treatment. The addition of ZN significantly improved the mechanical and biological properties of the HGs. The highest ZN concentration resulted in the strongest mechanical strength, measuring 52.2 MPa at 40% strain. HGs exhibited optimal swelling and degradation rates. Scanning electron microscopy analysis supported their porous nature. In vitro cell culture assays and wound healing assays demonstrated their excellent biocompatibility and regenerative potential. Drug-loaded HGs exhibited up to 90% drug release and antibacterial activity. All these results support their promising potential to support the regeneration of skeletal defects in a minimally invasive manner.

Strontium and Zinc Co-Doped Mesoporous Bioactive Glass Nanoparticles for Potential Use in Bone Tissue Engineering Applications.

Mesoporous bioactive glass nanoparticles (MBGNs) have attracted significant attention as multifunctional nanocarriers for various applications in both hard and soft tissue engineering. In this study, multifunctional strontium (Sr)- and zinc (Zn)-containing MBGNs were successfully synthesized via the microemulsion-assisted sol-gel method combined with a cationic surfactant (cetyltrimethylammonium bromide, CTAB). Sr-MBGNs, Zn-MBGNs, and Sr-Zn-MBGNs exhibited spherical shapes in the nanoscale range of 100 ± 20 nm with a mesoporous structure. Sr and Zn were co-substituted in MBGNs (60SiO2-40CaO) to induce osteogenic potential and antibacterial properties without altering their size, morphology, negative surface charge, amorphous nature, mesoporous structure, and pore size. The synthesized MBGNs facilitated bioactivity by promoting the formation of an apatite-like layer on the surface of the particles after immersion in Simulated Body Fluid (SBF). The effect of the particles on the metabolic activity of human mesenchymal stem cells was concentration-dependent. The hMSCs exposed to Sr-MBGNs, Zn-MBGNs, and Sr-Zn-MBGNs at 200 μg/mL enhanced calcium deposition and osteogenic differentiation without osteogenic supplements. Moreover, the cellular uptake and internalization of Sr-MBGNs, Zn-MBGNs, and Sr-Zn-MBGNs in hMSCs were observed. These novel particles, which exhibited multiple functionalities, including promoting bone regeneration, delivering therapeutic ions intracellularly, and inhibiting the growth of Staphylococcus aureus and Escherichia coli, are potential nanocarriers for bone regeneration applications.

Eco-friendly synthesis of mesoporous bioactive glass ceramics and functionalization for drug delivery and hard tissue engineering applications

Hard tissue regenerative mesoporous bioactive glass (MBG) has traditionally been synthesized using costly and toxic alkoxysilane agents and harsh conditions. In this study, MBG was synthesized using the cheaper reagent SiO2 by using a co-precipitation approach. The surface properties of MBG ceramic were tailored by functionalizing with amino and carboxylic groups, aiming to develop an efficient drug delivery system for treating bone infections occurring during or after reconstruction surgeries. The amino groups were introduced through a salinization reaction, while the carboxylate groups were added via a chain elongation reaction. The MBG, MBG-NH2, and MBG-NH-COOH were analyzed by using various techniques: x-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Brunauer–Emmett–Teller (BET), scanning electron microscopy and energy-dispersive x-ray spectroscopy. The XRD results confirmed the successful preparation of MBG, and the FTIR results indicated successful functionalization. BET analysis revealed that the prepared samples were mesoporous, and functionalization tuned their surface area and surface properties. Cefixime, an antibiotic, was loaded onto MBG, MBG-NH2, and MBG-NH-COOH to test their drug-carrying capacity. Comparatively, MBG-NH-COOH showed good drug loading and sustained release behavior. The release of the drug followed the Fickian diffusion mechanism. All prepared samples displayed favorable biocompatibility at higher concentration in the Alamar blue assay with MC3T3 cells and exhibited the good potential for hard tissue regeneration, as carbonated hydroxyapatite formed on their surfaces in simulated body fluid.

Magnesium-Substituted Brushite Cement: Physical and Mechanical Properties

Brushite cements (BrCs) are calcium phosphate-based materials that are being widely used in hard tissue engineering applications due to their osteoconductivity, injectability, and bioresorbability. Therefore, the goal was to evaluate the effects of Mg concentration on the phase composition, setting time, and strength of BrC. Mg, which plays a vital role in bodily functions and bone health, was added to BrC at concentrations of 0.25, 0.50, 1.00, 1.50, 2.00, and 2.50 wt.%. The results showed that Mg stabilizes the TCP structure and increases the TCP content in final BrC. The initial and final setting times of BrCs increase with higher concentrations of Mg. Although 0.25 wt.% Mg did not change the setting of BrCs significantly, a higher concentration of 1.00 wt.% increased the initial setting time from 4.87 ± 0.38 min to 15.14 ± 0.88 min. Cements with Mg concentrations of 1.5 wt.% and above did not set after 4 h. Mg addition up to 0.5 wt.% did not change the compressive strength; however, higher concentrations decreased it significantly and 2.5 Mg-BrC had the lowest strength of 0.45 ± 0.09 MPs. Together, our results show that Mg can be added up to 1.00 wt.% without any adverse effect on the physical and mechanical properties of BrC.

Recent Achievements in the Development of Biomaterials Improved with Platelet Concentrates for Soft and Hard Tissue Engineering Applications.

Platelet concentrates such as platelet-rich plasma, platelet-rich fibrin or concentrated growth factors are cost-effective autologous preparations containing various growth factors, including platelet-derived growth factor, transforming growth factor β, insulin-like growth factor 1 and vascular endothelial growth factor. For this reason, they are often used in regenerative medicine to treat wounds, nerve damage as well as cartilage and bone defects. Unfortunately, after administration, these preparations release growth factors very quickly, which lose their activity rapidly. As a consequence, this results in the need to repeat the therapy, which is associated with additional pain and discomfort for the patient. Recent research shows that combining platelet concentrates with biomaterials overcomes this problem because growth factors are released in a more sustainable manner. Moreover, this concept fits into the latest trends in tissue engineering, which include biomaterials, bioactive factors and cells. Therefore, this review presents the latest literature reports on the properties of biomaterials enriched with platelet concentrates for applications in skin, nerve, cartilage and bone tissue engineering.

Intrafibrillar calcium carbonate mineralization of electrospinning polyvinyl alcohol/collagen films with improved mechanical and bioactive properties.

Collagen films play an essential role in guided bone-regeneration (GBR) techniques, which create space, promote cell adhesion, and induce osteogenic differentiation. It is therefore crucial to design appropriate GBR films to facilitate bone regeneration. However, current electrospun collagen scaffolds used as bioactive materials have limited clinical applications due to their poor mechanical properties. In this study, polyvinyl alcohol (PVA)/collagen (Col) films were electrospun by mixing PVA and type I collagen solution. For the first time, the intrafibrillar mineralization of aragonite nanocrystals within the PVA/Col fibrils was achieved, resulting in the formation of a hierarchical, bioactive film. The PVA/Col-CaCO3 film exhibited good mechanical properties, with hardness and Young's modulus values of 211.6 ± 0.1 MPa and 5.6 ± 1.7 GPa, respectively. Furthermore, bone marrow mesenchymal stem cells (BMSCs) inoculated onto the PVA/Col-CaCO3 film demonstrated robust adhesion and proliferation. The mineralized fibrils effectively stimulated the growth of BMSCs while suppressing cell apoptosis. Besides, the PVA/Col-CaCO3 film significantly induced the osteogenic differentiation of BMSCs, revealing its potential biomedical applications in hard tissue engineering.

An HA/PEEK scaffold with modified crystallinity via 3D-bioprinting for multiple applications in hard tissue engineering

Hard tissues, especially teeth and bones, are highly mineralized and the large-scale defect or total loss of them is irreversible. There is still no ideal strategy for the reconstruction of various hard tissue defects that can achieve the balance between biological and mechanical properties. Polyether ether ketone (PEEK) has the potential to substitute for natural hard tissue in defect areas but is limited by its biological inertness. The addition of hydroxyapatite (HA) can significantly improve the osteogenic properties and osteointegration of PEEK materials. But the mechanical properties of HA/PEEK scaffolds are far from satisfaction making scaffolds easy to fracture. We put forward a strategy to balance the mechanical and biological properties of HA/PEEK scaffolds via the regulation of the inner crystallinity and HA mixing ratio and we systematically evaluated the modified HA/PEEK scaffolds through material characterization, in vitro and in vivo experiments. And we found that the 20%HA/PEEK scaffolds with low crystallinity achieved the required strength and elasticity, and exhibited the characteristics of promoting the proliferation, migration and osteogenic differentiation of bone marrow mesenchymal stem cells. The results of the implantation of beagles’ teeth, mandible and rib showed that the 20%HA/PEEK scaffold with low crystallinity could well withstand the local complex force in the defect area and combine well with natural bone tissue, which made it a candidate for a practical versatile hard tissue engineering scaffold.

Evaluation of Physicochemical Properties of a Hydroxyapatite Polymer Nanocomposite for Use in Fused Filament Fabrication.

Over the last decade, there has been an increasing interest in the use of bioceramics for biomedical purposes. Bioceramics, specifically those made of calcium phosphate, are commonly used in dental and orthopaedic applications. In this context, hydroxyapatite (HA) is considered a viable option for hard tissue engineering applications given its compositional similarity to bioapatite. However, owing to their poor mechanobiology and biodegradability, traditional HA-based composites have limited utilisation possibilities in bone, cartilage and dental applications. Therefore, the efficiency of nano HA (nHA) has been explored to address these limitations. nHA has shown excellent remineralising effects on initial enamel lesions and is widely used as an additive for improving existing dental materials. Furthermore, three-dimensional printing (3DP) or fused deposition modelling that can be used for creating dental and hard tissue scaffolds tailored to each patient's specific anatomy has attracted considerable interest. However, the materials used for producing hard tissue with 3DP are still limited. Therefore, the current study aimed to develop a hybrid polymer nanocomposite composed of nHA, nanoclay (NC) and polylactic acid (PLA) that was suitable for 3DP. The nHA polymer nanocomposites were extruded into filaments and their physiochemical properties were evaluated. The results showed that the addition of nHA and NC to the PLA matrix significantly increased the water absorption and contact angle. In addition, the hardness increased from 1.04 to 1.25 times with the incorporation of nHA. In sum, the nHA-NC-reinforced PLA could be used as 3DP filaments to generate bone and dental scaffolds, and further studies are needed on the biocompatibility of this material.

Sol-gel synthesis of spherical monodispersed bioactive glass nanoparticles co-doped with boron and copper

In this work, an optimized sol-gel process for the synthesis of spherical and monodispersed bioactive glass nanoparticles doped with boron and copper was developed, by investigating different synthesis parameters. The obtained glasses were characterized in terms of morphology, composition, dispersibility, structure and in vitro reactivity. The performed characterizations demonstrated that shape, dimension and dispersion can be tailored by acting on the timing of the addition of the catalyst and on the synthesis process, in particular the centrifugation step. The optimized glass particles showed a spherical shape, good ions incorporation and good dispersion. In vitro bioactivity test demonstrated that the boron and copper addition did not interfere with the glass ability to induce the precipitation of hydroxyapatite. The shape, dispersion, bioactive behavior and content of boron and copper of these novel bioactive glass particles make them very promising for both hard and soft tissue engineering applications.

Porous bioceramic scaffolds based on akermanite obtained by 3D printing for bone tissue engineering

Porous bioceramic scaffolds were obtained by the 3D printing technique starting from a mixture of hydroxypropyl methyl cellulose and a powder obtained by sol-gel method which contains merwinite, monticellite, pseudowolastonie and periclase.The scaffolds were thermally treated at 1370 °C for 3 h and the main mineralogical compound assessed by XRD was akermanite. The obtained scaffolds have adequate mechanical and biological properties thus a great potential for applications in hard tissue engineering. The positive results obtained for this type of scaffolds are due to the precision of 3D printing technique, i.e. ability to control shape and size of both scaffolds and pores, as well as the high reproducibility. The porous bioactive ceramic scaffolds have adequate compressive strength (up to 3.5 MPa) and exhibit mineralization capacity and potential in stimulating cell adhesion and proliferation as well as bacteriostatic properties.

Incorporation of graphene oxide as a coupling agent in a 3D printed polylactic acid/hardystonite nanocomposite scaffold for bone tissue regeneration applications

3D printing fabrication has become a dominant approach for the creation of tissue engineering constructs as it is accurate, fast, reproducible and can produce patient-specific templates. In this study, 3D printing is applied to create nanocomposite scaffold of polylactic acid (PLA)/hardystonite (HT)-graphene oxide (GO). GO is utilized as a coupling agent of alkaline treated HT nanoparticles within PLA matrix. The addition of HT-GO nanoparticles of up to 30 wt% to PLA matrix was found to increase the degradability from 7.33 ± 0.66 to 16.03 ± 1.47 % during 28 days. Also, the addition of 20 wt% of HT-GO nanoparticles to PLA scaffold (PLA/20HTGO sample) significantly increased the compressive strength (from 7.65 ± 0.86 to 14.66 ± 1.01 MPa) and elastic modulus (from 94.46 ± 18.03 to 189.15 ± 10.87 MPa). The apatite formation on the surface of nanocomposite scaffolds in simulated body fluid within 28 days confirmed the excellent bioactivity of nanocomposite scaffolds. The MG63 cell adhesion and proliferation and, also, the rat bone marrow mesenchymal stem cells osteogenic differentiation were highly stimulated on the PLA/20HTGO scaffold. According to the sum of results obtained in the current study, the optimized PLA/20HTGO nanocomposite scaffold is highly promising for hard tissue engineering applications.

Recent progress of bio‐printed PEGDA‐based bioinks for tissue regeneration

AbstractThree‐dimensional (3D) bioprinting is a promising method for the fabrication of tissue engineering constructs. The bioprintable materials with cells or other biological parts, which are called bioinks, are arranged layer by layer and make multicellular structures. Not all materials can be printed, and a set of requirements should be met to formulate the appropriate bioink. Poly (ethylene glycol) (PEGDA), as a synthetic polymer, is a promising choice for regenerative medicine applications due to its biocompatibility, ease of crosslinking, and adjustability of its mechanical and chemical properties depending on the application. This review aims to guide and familiarize the reader with the PEGDA‐based bioink as a raw material of the 3D‐bioprinting method, its properties, and applications in soft and hard tissue engineering.

Potential Use of Nucleic Acids as a Preceramic Polymer to Synthesize Nanodiamond-Embedded Phosphate Glass for Hard Tissue Engineering.

In recent years, nucleic acid has emerged as a versatile molecule that has been strategically used in material synthesis and biomedical applications. Keeping in mind the presence of the phosphate group, a glass former in the nucleic acids, we synthesized a transparent glass-like material by the thermal treatment of nucleic acids (DNA and RNA) at 900 °C at atmospheric pressure. Characterization of this material by transmission electron microscopy, X-ray photoelectron spectroscopy, and confocal fluorescence microscopy suggested the presence of in situ-formed nanodiamonds within the phosphate glass matrix. The molecular structure of glass investigated by X-ray photoelectron and infrared spectroscopy indicated a nearly equal proportion of metaphosphates and smaller phosphate units (pyro- and ortho-phosphate) that form the phosphate glass matrix. Thereafter, in vitro biological experiments showed that the nucleic acid-derived glass was non-toxic and cytocompatible, enhanced extracellular matrix secretion, and increased intracellular alkaline phosphatase activity, with potential application in hard tissue engineering. Our work offers insights into nanodiamond synthesis at atmospheric pressure and proves that nucleic acids could be used as a precursor to making an innovative glass-ceramic biomaterial.

Poly(ε-caprolactone)/bioactive glass composite electrospun fibers for tissue engineering applications.

In this work, composite electrospun fibers containing innovative bioactive glass nanoparticles were produced and characterized. Poly(ε-caprolactone), benign solvents, and sol-gel B- and Cu-doped bioactive glass powders were used to fabricate fibrous scaffolds. The retention of bioactive glass nanoparticles in the polymer matrix, the electrospinnability of this novel solution and the obtained electrospun composites were extensively characterized. As a result, composite electrospun fibers characterized by biocompatibility, bioactivity, and exhibiting overall properties adequate for both hard and soft tissue engineering applications, have been produced. The addition of these bioactive glass nanoparticles was, indeed, able to impart bioactive properties to the fibers. Cell culture studies show promising results, demonstrating proliferation and growth of cells on the composite fibers. Wettability, degradation rate, and mechanical performance were also tested and are in line with previous results.

DFT theoretical and experimental studies unraveling the structural and electronic properties of niobium doped calcium apatite ceramics

Calcium apatite ceramics consisting of a biphasic structure of hydroxyapatite (HAP) and tricalcium phosphate (β-TCP) have been widely explored by biomedical communities for hard-tissue engineering applications, especially bone replacement as it has the potential to mimic the properties of the natural bones. Doping of cations in the hydroxyapatite (NbHAP) is expected to promote the alkaline phosphatase activity and thereby generation of new bone, which, however, depends on its structural and electronic properties. In the present investigation, the variation in the structural and electronic properties of NbHAP prepared by the chemical precipitation method is determined theoretically by employing density functional theory (DFT) using the B3LYP functional method in the Gaussian 09 package program and experimentally using various characterization tools. The experimental investigation by X-ray diffraction (XRD) studies revealed notable variation in the β-TCP content in NbHAP when compared to the pristine HAP, while the Inductively Coupled Plasma spectroscopic results revealed the presence of Nb ions in doped HAP and along with the percentage increase in β-TCP content in NbHAP by Ca/P molar ratio variation, when compared with the HAP system. In addition, experimentally determined Raman spectroscopic values revealed the formation of substitution-type solid solutions in the NbHAP system. The doping of niobium ions was shown to cause noticeable variations in the reactivity indices, as indicated by a number of electronic characteristics that were calculated using DFT. Furthermore, variations in the theoretical parameters such as dipole moment, polarizability, and electric susceptibility revealed that NbHAP is better bioceramic material for hard-tissue engineering applications in comparison to HAP.

Additive manufacturing of PLA-Mg composite scaffolds for hard tissue engineering applications

Polylactic acid (PLA) is considered as a great option to be employed as 3D porous scaffold in hard tissue engineering applications owing to its excellent biocompatibility and processability. However, relatively weak mechanical properties and inappropriate biodegradability limit its extensive usage. In order to overcome the mentioned challenges, micrometric magnesium particles were incorporated into the PLA matrix by the fused deposition modeling (FDM) technique. The effects of various Mg contents (i.e., 2, 4, 6, 8 and 10 wt%) on the structural, thermal, rheological, mechanical, wettability, degradability characteristics and cellular behavior of the 3D porous PLA-Mg composite scaffolds were examined. The developed PLA-Mg composites exhibit an interconnected porous structure with a mostly uniform distribution of Mg particles in the PLA matrix. It was found that incorporation of Mg particles into the PLA matrix enhances the mechanical, physical, chemical and biological characteristics of PLA. The cell studies demonstrate that the PLA-6Mg composite scaffold provides the best cellular response in terms of cell atachment and viability. The obtained results in this investigation greatly suggest that the 3D-printed PLA-Mg composite scaffold is a promising candidate for hard tissue engineering applications.