Biodegradable macroporous scaffold with nano-crystal surface microstructure for highly effective osteogenesis and vascularization

Fabricating oxygen self-supplying 3D printed bioactive hydrogel scaffold for augmented vascularized bone regeneration

Limited cells and factors, inadequate mechanical properties, and necrosis of defects center have hindered the wide clinical application of bone-tissue engineering scaffolds. Herein, we construct a self-oxygenated 3D printed bioactive hydrogel scaffold by integrating oxygen-generating nanoparticles and hybrid double network hydrogel structure. The hydrogel scaffold possesses the characteristics of extracellular matrix; Meanwhile, the fabricated hybrid double network structure by polyacrylamide and CaCl2-crosslinked sodium carboxymethylcellulose endows the hydrogel favorable compressive strength and 3D printability. Furthermore, the O2 generated by CaO2 nanoparticles encapsulated in ZIF-8 releases steadily and sustainably because of the well-developed microporous structure of ZIF-8, which can significantly promote cell viability and proliferation in vitro, as well as angiogenesis and osteogenic differentiation with the assistance of Zn2+. More significantly, the synergy of O2 and 3D printed pore structure can prevent necrosis of defects center and facilitate cell infiltration by providing cells the nutrients and space they need, which can further induce vascular network ingrowth and accelerate bone regeneration in all areas of the defect in vivo. Overall, this work provides a new avenue for preparing cell/factor-free bone-tissue engineered scaffolds that possess great potential for tissue regeneration and clinical alternative.

The development of magnesium-based biomaterials in bone tissue engineering: A review

Bone regeneration is a vital clinical challenge in massive or complicated bone defects. Recently, bone tissue engineering has come to the fore to meet the demand for bone repair with various innovative materials. However, the reported materials usually cannot satisfy the requirements, such as ideal mechanical and osteogenic properties, as well as biocompatibility at the same time. Mg-based biomaterials have considerable potential in bone tissue engineering owing to their excellent mechanical strength and biosafety. Moreover, the biocompatibility and osteogenic activity of Mg-based biomaterials have been the research focuses in recent years. The main limitation faced in the applications of Mg-based biomaterials is rapid degradation, which can produce excessive Mg2+ and hydrogen, affecting the healing of the bone defect. In order to overcome the limitations, researchers have explored several ways to improve the properties of Mg-based biomaterials, including alloying, surface modification with coatings, and synthesizing other composite materials to control the degradation rate upon implantation. This article reviewed the osteogenic mechanism and requirement for appropriate degradation rate and focused on current progress in the biomedical use of Mg-based biomaterials to inspire more clinical applications of Mg in bone regeneration in the future.

Alkaline earth metals for osteogenic scaffolds: From mechanisms to applications

Regeneration of bone defects is a significant challenge today. As alternative approaches to the autologous bone, scaffold materials have remarkable features in treating bone defects; however, the various properties of current scaffold materials still fall short of expectations. Due to the osteogenic capability of alkaline earth metals, their application in scaffold materials has become an effective approach to improving their properties. Furthermore, numerous studies have shown that combining alkaline earth metals leads to better osteogenic properties than applying them alone. In this review, the physicochemical and physiological characteristics of alkaline earth metals are introduced, mainly focusing on their mechanisms and applications in osteogenesis, especially magnesium (Mg), calcium (Ca), strontium (Sr), and barium (Ba). Furthermore, this review highlights the possible cross-talk between pathways when alkaline earth metals are combined. Finally, some of the current drawbacks of scaffold materials are enumerated, such as the high corrosion rate of Mg scaffolds and defects in the mechanical properties of Ca scaffolds. Moreover, a brief perspective is also provided regarding future directions in this field. It is worth exploring that whether the levels of alkaline earth metals in newly regenerated bone differs from those in normal bone. The ideal ratio of each element in the bone tissue engineering scaffolds or the optimal concentration of each elemental ion in the created osteogenic environment still needs further exploration. The review not only summarizes the research developments in osteogenesis but also offers a direction for developing new scaffold materials.

Biomaterials based on hyaluronic acid, collagen and peptides for three-dimensional cell culture and their application in stem cell differentiation

In recent decades, three-dimensional (3D) cell culture technologies have been developed rapidly in the field of tissue engineering and regeneration, and have shown unique advantages and great prospects in the differentiation of stem cells. Herein, the article reviews the progress and advantages of 3D cell culture technologies in the field of stem cell differentiation. Firstly, 3D cell culture technologies are divided into two main categories: scaffoldless and scaffolds. Secondly, the effects of hydrogels scaffolds and porous scaffolds on stem cell differentiation in the scaffold category were mainly reviewed. Among them, hydrogels scaffolds are divided into natural hydrogels and synthetic hydrogels. Natural materials include polysaccharides, proteins, and their derivatives, focusing on hyaluronic acid, collagen and polypeptides. Synthetic materials mainly include polyethylene glycol (PEG), polyacrylic acid (PAA), polyvinyl alcohol (PVA), etc. In addition, since the preparation techniques have a large impact on the properties of porous scaffolds, several techniques for preparing porous scaffolds based on different macromolecular materials are reviewed. Finally, the future prospects and challenges of 3D cell culture in the field of stem cell differentiation are reviewed. This review will provide a useful guideline for the selection of materials and techniques for 3D cell culture in stem cell differentiation.

Magnetic Hydroxyapatite Composite Nanoparticles for Augmented Differentiation of MC3T3-E1 Cells for Bone Tissue Engineering

Progressive aging harms bone tissue structure and function and, thus, requires effective therapies focusing on permanent tissue regeneration rather than partial cure, beginning with regenerative medicine. Due to advances in tissue engineering, stimulating osteogenesis with biomimetic nanoparticles to create a regenerative niche has gained attention for its efficacy and cost-effectiveness. In particular, hydroxyapatite (HAP, Ca₁₀(PO₄)₆(OH)₂) has gained significant interest in orthopedic applications as a major inorganic mineral of native bone. Recently, magnetic nanoparticles (MNPs) have also been noted for their multifunctional potential for hyperthermia, MRI contrast agents, drug delivery, and mechanosensitive receptor manipulation to induce cell differentiation, etc. Thus, the present study synthesizes HAP-decorated MNPs (MHAP NPs) via the wet chemical co-precipitation method. Synthesized MHAP NPs were evaluated against the preosteoblast MC3T3-E1 cells towards concentration-dependent cytotoxicity, proliferation, morphology staining, ROS generation, and osteogenic differentiation. The result evidenced that MHAP NPs concentration up to 10 µg/mL was non-toxic even with the time-dependent proliferation studies. As nanoparticle concentration increased, FACS apoptosis assay and ROS data showed a significant rise in apoptosis and ROS generation. The MC3T3-E1 cells cocultured with 5 µg/mL MHAP NPs showed significant osteogenic differentiation potential. Thus, MHAP NPs synthesized with simple wet chemistry could be employed in bone regenerative therapy.

Nanofibrous Hydrogel Nanocomposite Based on Strontium-Doped Bioglass Nanofibers for Bone Tissue Engineering Applications

Simple Summary

Currently, bone defects, diseases, and injuries are common and global problems. These defects can be treated with several surgical methods and bone grafting, but these methods have limitations, including immune disorders, risk of infection, long-term recovery, movement problems, and high costs. A promising treatment option for bone replacement is the design and construction of scaffolds that mimic the properties of bone tissue and provide a suitable environment for cell and tissue growth. Achieving successful results in this method is dependent on the composition and structure of materials used as scaffolds. Bone is a composite consisting of a mineral fraction, mainly a combination of calcium phosphate, and an organic matrix. Here, we designed and produced a porous, non-toxic, and degradable scaffold made of alginate natural polymer and bioactive glass that contains strontium as well as the common elements of bioglasses—silica, calcium, sodium, and phosphorus. The scaffold is degraded at an optimized rate with the simultaneous proliferation and growth of cells, thus providing a suitable environment for the growth and development of new tissue and blood vessels. The outcomes of this study presented this scaffold as a functional structure to be used in treating bone defects and reconstructing damaged bone.

Abstract

The main aim of the current study is to fabricate an osteocompatible, bioactive, porous, and degradable bone tissue engineering scaffold. For this purpose, bioactive glasses (BGs) were chosen due to their similarity to bone’s natural mineral composition, and the effect of replacing Ca ions with Sr on their properties were considered. First, strontium-containing BGs (Sr-BGs) were synthesized using the electrospinning technique and assembled by the sol–gel method, then they were incorporated into the alginate (Alg) matrix. Photographs of the scanning electron microscope (SEM) showed that the BG nanofibers have a diameter of 220 ± 36 nm, which was smaller than the precursor nanofibers (275 ± 66 nm). The scaffolds possess a porous internal microstructure (230–330 nm pore size) with interconnected pores. We demonstrated that the scaffolds could be degraded in the acetate sodium buffer and phosphate-buffered saline. The osteoactivity of the scaffolds was confirmed via visual inspection of the SEM illustrations after seven days of immersing them in the SBF solution. In vitro assessments disclosed that the produced Alg-based composites including Sr-BGs (Alg/Sr-BGs) are blood-compatible and biocompatible. Accumulating evidence shows that Alg/Sr-BG (5%, 10%, and 15%) hydrogels could be a promising scaffold for bone regeneration.

Synthesis and Properties of Magnetic Fe3O4/PCL Porous Biocomposite Scaffolds with Different Sizes and Quantities of Fe3O4 Particles

In clinical practice, to treat diseases such as osteosarcoma or chondrosarcoma with broad surgical ostectomy, it would be ideal to have scaffolds that not only fill up the bone void but also possess the ability to regulate the subsequent regimes for targeted chemotherapy and/or bone regeneration. Magnetic targeting of therapeutic agents to specific sites in the body provides certain advantages such as minimal side-effects of anti-cancer drugs. The objective of this study was to characterize novel magnetic scaffolds that can be used as a central station to regulate the drug delivery of a magnetic nanoparticle system. Different sizes and quantities of Fe3O4 particles were mixed with poly-ε-caprolactone (PCL) to construct the magnetic scaffolds, and their mechanical properties, degradation performance, and cell biocompatibility were evaluated. It appeared that the presence of Fe3O4 particles influenced the magnetic, mechanical, and biological performances of the scaffolds. The prepared bio-nanocomposite scaffolds provided predominantly magnetic/superparamagnetic properties. Scaffolds with a micron-sized Fe3O4 to PCL weight (wt) ratio of 0.1:0.9 exhibited higher mechanical performances among samples, with Young’s modulus reaching 1 MPa and stiffness, 13 N/mm. Although an increased Fe3O4 particle proportion mildly influenced cell growth during the biocompatibility test, none of the Fe3O4/PCL scaffolds showed a cytotoxic effect.

Stereocomplexation Reinforced High Strength Poly(L-lactide)/Nanohydroxyapatite Composites for Potential Bone Repair Applications

Composite materials composed of polylactide (PLA) and nano-hydroxyapatite (n-HA) have been recognized as excellent candidate material in bone repai The difference in hydrophilicity/hydrophobicity and poor interfacial compatibility between n-HA filler and PLA matrix leads to non-uniform dispersion of n-HA in PLA matrix and consequent poor reinforcement effect. In this study, an HA/PLA nanocomposite was designed based on the surface modification of n-HA with poly(D-lactide) (PDLA), which not only can improve the dispersion of n-HA in the poly(L-lactide) (PLLA) matrix but also could form a stereocomplex crystal with the matrix PLLA at the interface and ultimately lead to greatly enhanced mechanical performance The n-HA/PLA composites were characterized by means of scanning electron microscopy, Fourier transform infrared spectroscopy, X-Ray diffraction, thermal gravity analysis, differential scanning calorimetry, and a mechanical test; in vitro cytotoxicity of the composite material as well as its efficacy in inducing osteogenic differentiation of rat bone marrow stromal cells (rMSCs) were also evaluated. Compared with those of neat PLLA, the tensile strength, Young’s modulus, interfacial shear strength, elongation at break and crystallinity of the composites increased by 34%, 53%, 26%, 70%, and 17%, respectively. The adhesion and proliferation as well as the osteogenic differentiation of rMSCs on HA/PLA composites were clearly evidenced. Therefore, the HA/PLA composites have great potential for bone repai.

Development of hierarchical porous bioceramic scaffolds with controlled micro/nano surface topography for accelerating bone regeneration

Mimicking hierarchical porous architecture of bone has been considered as a valid approach to promote bone regeneration. In this study, hierarchical porous β-tricalcium phosphate (β-TCP) scaffolds were constructed by combining digital light processing (DLP) printing technique and in situ growth crystal process. Macro/micro hierarchical scaffolds with designed macro pores for facilitating the ingrowth of bone tissue were fabricated by DLP printing. Three types of micro/nano surface topography were obtained by in situ growth crystal process to regulate stem cells behavior. The attachment and proliferation of rat bone marrow mesenchymal stem cells (rBMSCs) were strongly dependent on the surface roughness and the specific surface area. The micro/nano surface topography distinctly facilitated the differentiation of rBMSCs by targeting MAPK, STAT and AKT signaling pathways, in which the sodium hydroxide treatment group showed the highest promoting effect. Furthermore, in vivo results of skull defect repair model of rats indicated that hierarchical scaffolds with micro/nano topographies exhibited appealing bone regeneration capacity. The hierarchical porous bioceramic scaffolds constructed by integrating structural design and physical stimulation of the external surface topography have great potential for rapid bone repair via modulation of microenvironmental regulatory pathways at the bone defect site.

A 3D printed Ga containing scaffold with both anti-infection and bone homeostasis-regulating properties for the treatment of infected bone defects

Large bone defects face a high risk of infection, which can also lead to bone homeostasis disorders. This seriously hinders the bone healing process; therefore, the help of a dual-functional scaffold that has both anti-infection and bone-homeostasis-regulating capacities is needed in the treatment of infected bone defects. In this study, a 3D printed dual-functional scaffold composed of poly-ε-caprolactone (PCL), mesoporous bioactive glasses (MBG), and gallium (Ga) was produced. In vitro experiments demonstrated the excellent antibacterial ability of the PCL/MBG/Ga scaffold against methicillin-resistant Staphylococcus aureus (MRSA) and Escherichia coli (E. coli). The scaffold also significantly inhibited osteoclastic activity and promoted osteogenic differentiation. Furthermore, a rabbit model with an infected bone defect in the radius was used to evaluate the in vivo bone healing capability of PCL/MBG/Ga. The results demonstrate that the PCL/MBG/Ga scaffold can significantly accelerate bone healing and prevent bone resorption, suggesting its potential for application in repairing infected bone defects.

The effect of enhanced bone marrow in conjunction with 3D-printed PLA-HA in the repair of critical-sized bone defects in a rabbit model

Background

Traditionally, the iliac crest has been the most common harvesting site for autologous bone grafts; however, it has some limitations, including poor bone availability and donor-site morbidity. This study sought to explore the effect of enhanced bone marrow (eBM) in conjunction with three-dimensional (3D)-printed polylactide–hydroxyapatite (PLA-HA) scaffolds in the repair of critical-sized bone defects in a rabbit model.

Methods

First, 3D-printed PLA-HA scaffolds were fabricated and evaluated using micro-computed tomography (µCT) and scanning electron microscopy (SEM). Twenty-seven New Zealand white rabbits were randomly divided into 3 groups (n=9 per group), and the defects were treated using 3D-printed PLA-HA scaffolds (the PLA-HA group) or eBM in conjunction with 3D-printed PLA-HA scaffolds (the PLA-HA/eBM group), or were left untreated (the control group). Radiographic, µCT, and histological analyses were performed to evaluate bone regeneration in the different groups.

Results

The 3D-printed PLA-HA scaffolds were cylindrical, and had a mean pore size of 500±47.1 µm and 60%±3.5% porosity. At 4 and 8 weeks, the lane-sandhu X-ray score in the PLA-HA/eBM group was significantly higher than that in the PLA-HA group and the control group (P<0.01). At 8 weeks, the µCT analysis showed that the bone volume (BV) and bone volume/tissue volume (BV/TV) in the PLA-HA/eBM group were significantly higher than those in the PLA-HA group and the control group (P<0.01). Hematoxylin and eosin staining indicated that the new bone area in the PLA-HA/eBM group was significantly higher than that in the PLA-HA group and the control group (P<0.01).

Conclusions

The group that was treated with eBM in conjunction with 3D-printed PLA-HA showed enhanced bone repair compared to the other 2 groups. PLA-HA/eBM scaffolds represent a promising way to treat critical-sized bone defects.

Biological Roles and Delivery Strategies for Ions to Promote Osteogenic Induction

Bone is the most studied tissue in the field of tissue regeneration. Even though it has intrinsic capability to regenerate upon injury, several pathologies and injuries could hamper the highly orchestrated bone formation and resorption process. Bone tissue engineering seeks to mimic the extracellular matrix of the tissue and the different biochemical pathways that lead to successful regeneration. For many years, the use of extrinsic factors (i.e., growth factors and drugs) to modulate these biological processes have been the preferred choice in the field. Even though it has been successful in some instances, this approach presents several drawbacks, such as safety-concerns, short release profile and half-time life of the compounds. On the other hand, the use of inorganic ions has attracted significant attention due to their therapeutic effects, stability and lower biological risks. Biomaterials play a key role in such strategies where they serve as a substrate for the incorporation and release of the ions. In this review, the methodologies used to incorporate ions in biomaterials is presented, highlighting the osteogenic properties of such ions and the roles of biomaterials in controlling their release.

Biphasic ceramic biomaterials with tunable spatiotemporal evolution for highly efficient alveolar bone repair

Alveolar bone defects, which are characterized by a relatively narrow space and location adjacent to the cementum, require promising substitute biomaterials for their regeneration. In this study, we introduced novel yolk-shell biphasic bio-ceramic granules with/without a customized porous shell and evaluated their biological effect together with structural transformation. Firstly, a self-made coaxial bilayer capillary system was applied for the fabrication of granules. Secondly, thorough morphological and physicochemical characterizations were performed in vitro. Subsequently, the granules were implanted into critical-size alveolar bone defects (10 × 4 × 3 mm) in New Zealand white rabbits, with Bio-Oss® as the positive control. Finally, at 2, 4, 8, and 16 weeks postoperatively, the alveolar bone specimens were harvested and assessed via radiological and histological examination. Our results showed that the yolk-shell biphasic bio-ceramic granules, especially those with porous shells, exhibited a tunable ion release performance, improved biodegradation behavior and satisfactory osteogenesis compared with the homogeneously hybrid and Bio-Oss® granules both in vitro and in vivo. This study provides the first evidence that novel yolk-shell bio-ceramic granules, on account of their adjustable porous microstructure, have great potential in alveolar bone repair.

Assessment of the Release of Vascular Endothelial Growth Factor from 3D-Printed Poly-ε-Caprolactone/Hydroxyapatite/Calcium Sulfate Scaffold with Enhanced Osteogenic Capacity

Vascular endothelial growth factor (VEGF) is one of the most crucial growth factors and an assistant for the adjustment of bone regeneration. In this study, a 3D scaffold is fabricated using the method of fused deposition modeling. Such a fabricated method allows us to fabricate scaffolds with consistent pore sizes, which could promote cellular ingrowth into scaffolds. Therefore, we drafted a plan to accelerate bone regeneration via VEGF released from the hydroxyapatite/calcium sulfate (HACS) scaffold. Herein, HACS will gradually degrade and provide a suitable environment for cell growth and differentiation. In addition, HACS scaffolds have higher mechanical properties and drug release compared with HA scaffolds. The drug release profile of the VEGF-loaded scaffolds showed that VEGF could be loaded and released in a stable manner. Furthermore, initial results showed that VEGF-loaded scaffolds could significantly enhance the proliferation of human mesenchymal stem cells (hMSCs) and human umbilical vein endothelial cells (HUVEC). In addition, angiogenic- and osteogenic-related proteins were substantially increased in the HACS/VEGF group. Moreover, in vivo results revealed that HACS/VEGF improved the regeneration of the rabbit’s femur bone defect, and VEGF loading improved bone tissue regeneration and remineralization after implantation for 8 weeks. All these results strongly imply that the strategy of VEGF loading onto scaffolds could be a potential candidate for future bone tissue engineering.

Effects of a Coating of Nano Silicon Nitride on Porous Polyetheretherketone on Behaviors of MC3T3-E1 Cells in Vitro and Vascularization and Osteogenesis in Vivo

To improve the bioperformances of porous polyetheretherketone (PPK) for bone repair, silicon nitride-coated PPK (CSNPPK) was prepared by a method of suspension coating and melt binding. The results revealed that, as compared with PPK, the surface roughness, compressive strength, and water absorption of CSNPPK increased, while the pore size and porosity of CSNPPK exhibited no obvious changes. In addition, the cellular responses (including attachment, proliferation, and differentiation as well as osteogenically related gene expressions) of the MC3T3-E1 cells to CSNPPK were remarkably promoted compared with PPK and dense polyetheretherketone in vitro. Moreover, in the model of rabbit femoral condyle defects, the results of micro computed tomography and histological and mechanical evaluation revealed that the ingrowth of new vessels and bone tissues into CSNPPK was significantly greater than that into PPK in vivo. Furthermore, the load-displacement and push-out loads for CSNPPK with bone tissues were higher than for PPK, indicating good osseointegration. In short, CSNPPK not only promoted vascularization but also enhanced osteogenesis as well as osseointegration in vivo. Therefore, it can be suggested that CSNPPK with good biocompatibility, osteogenic activity, and vascularization might be a promising candidate as an implant for bone substitute and repair.

Promoting osteoblasts responses in vitro and improving osteointegration in vivo through bioactive coating of nanosilicon nitride on polyetheretherketone

Objective

To enhance the bioactivity of polyetheretherketone (PEEK) while maintain its mechanical strengths.

Methods

Suspension coating and melt bonding.

Results

Silicon nitride (Si₃N₄, SN) coating lead to higher surface roughness, hydrophilicity and protein absorption; SN coating could slowly release Si ion into simulated body fluid (SBF), which caused weak alkaline of micro-environment owing to the slight dissolution of SN; SN coating resulted in the improvements of adhesion, proliferation, differentiation and gene expressions of MC3T3-E1 cells in vitro; SN coating of PEEK with bioactive SN coating (CSNPK) obviously promoted bone regeneration and osseointegration in vivo.

Conclusions

CSNPK with SN coating as bone implant might be a promising candidate for orthopedic implants.

The Translational Potential of this Article

The silicon nitride-coated polyetheretherketone (CSNPK) prepared in this article could induce MC3T3-E1 cells adhesion, proliferation and differentiation in vitro; it could also induce bone regeneration in bone defect in vivo, which indicate its good cytocompatibility and biocompatibility. If the raw materials are medical grade, and preparation process as well as production process of this article are further improved, it will have great translational potential.

Template-assisted, Sol-gel Fabrication of Biocompatible, Hierarchically Porous Hydroxyapatite Scaffolds

Hierarchically porous hydroxyapatite (HHA) scaffolds were synthesized by template-assisted sol-gel chemistry. Polyurethane foam and a block copolymer were used as templates for inducing hierarchically porous structures. The HHA scaffolds exhibited open porous structures with large pores of 400-600 µm and nanoscale pores of ~75 nm. In comparison with conventional hydroxyapatite (CHA), HHA scaffolds exhibited significantly higher surface areas and increased protein adsorption for bovine serum albumin and vitronectin. Both the HHA and CHA scaffolds exhibited well in vitro biocompatibility. After 1 day, Saos-2 osteoblast-like cells bound equally well to both HHA and CHA scaffolds, but after 7 days in culture, cell proliferation was significantly greater on the HHA scaffolds (p < 0.01). High surface area and hierarchical porous structure contributed to the selective enhancement of osteoblast proliferation on the HHA scaffolds.

Osteogenesis, vascularization and osseointegration of a bioactive multiphase macroporous scaffold in the treatment of large bone defects

We report a segmental radial bone defect model used to evaluate the osteogenesis, vascularization and osseointegration of a bioactive multiphase macroporous scaffold with nano-crystal surface microstructures that can release bioactive ions.