Load-bearing Bone Regeneration Research Articles

Mineralized Collagen/Polylactic Acid Composite Scaffolds for Load-Bearing Bone Regeneration in a Developmental Model.

Repairing load-bearing bone defects in children remains a big clinical challenge. Mineralized collagen (MC) can effectively simulate natural bone composition and hierarchical structure and has a good biocompatibility and bone conductivity. Polylactic acid (PLA) is regarded as a gold material because of its mechanical properties and degradability. In this study, we prepare MC/PLA composite scaffolds via in situ mineralization and freeze-drying. Cell, characterization, and animal experiments compare and evaluate the biomimetic properties and repair effects of the MC/PLA scaffolds. Phalloidin and DAPI staining results show that the MC/PLA scaffolds are not cytotoxic. CCK-8 and scratch experiments prove that the scaffolds are superior to MC and hydroxyapatite (HA)/PLA scaffolds in promoting cell proliferation and migration. The surface and interior of the MC/PLA scaffolds exhibit rich interconnected pore structures with a porosity of ≥70%. The XRD patterns are typical HA waveforms. X-ray, micro-CT, and H&E staining reveal that the defect boundary disappears, new bone tissue grows into MC/PLA scaffolds in a large area, and the scaffolds are degraded after six months of implantation. The MC/PLA composite scaffold has a pore structure and composition similar to cancellous bone, with a good biocompatibility and bone regeneration ability.

Bamboo-Based Biomaterials for Cell Transportation and Bone Integration.

The construction of hierarchical porous structure in biomaterials is of great significance for improving nutrient transport and biological performance. However, it is still challenging to design porous bone substitutes with high strength and biological properties, which limits their clinical applications in load-bearing bone regeneration. Herein, based on hierarchical porous structure of renewable bamboo, the mineralized calcium phosphate/bamboo composite scaffolds with high strength and excellent transport performance are successfully prepared in combination of biotemplated approach and biomimetic mineralization. The mineralized biomaterials have simultaneously achieved high mechanical strength and low modulus, similar to those of cortical bone. Furthermore, the mineralized biomaterials exhibit good liquid transport capacity and can transport cells along anti-gravity direction. Based on density functional theory (DFT) calculations, the mineralized calcium phosphate reveals the optimal H2 O adsorption energy (-0.651eV) and low diffusion energy barrier (0.743eV), which is conducive to enhance hydrophilicity and liquid transport performance. Moreover, owing to the synergistic effect of the porous structure of biotemplate and bioactive mineralized components, the mineralized biomaterials possess enhanced bone integration and osteoconduction properties. The present study shed light on deeper understanding of mineralized biosourced materials, offering a strategy of combining green chemistry with tissue engineering to prepare eco-friendly biomaterials.

Developing of Load-bearing Bones Replacement Based on Cerium Compounds/Nano-hydroxyapatite Composites

The importance of implantable biomaterials is growing up in recent days for modern medicine, especially fixation, replacement, and regeneration of load-bearing bones. Through the past several years, metals, ceramics, polymers, and their composites, have been used for the reconstruction of hard tissues. Special standards such as adequate mechanical and biocompatible properties are required to avoid rejection reactions of the tissues. Recently, a number of novel advanced biomaterials are developed as promising candidates. Amongst those, cerium-based biomaterials acquired attention as a substitution material for hard tissues reconstruction because of cerium antioxidative properties, which enabled it to be used to decrease mediators of inflammation. In addition, the eminent mechanical properties, as well as the perfect chemical and biological compatibilities, make cerium-based biomaterials attractive for biomedical application.

Fabrication and Characterization of Ta–GelMA–BG Scaffolds by Chemical Crosslinking Processing for Promotion Osteointegration

The repair of bone defects in load-bearing positions still faces great challenges. Tantalum (Ta) has attempted to repair bone defects based on the excellent mechanical properties. However, the osseointegration of Ta needs to be improved due to the lack of osteoinduction. Herein, tantalum–gelatin–methacryloyl–bioactive glass (Ta–GelMA–BG) scaffolds were successfully fabricated by loading BG in 3D-printed Ta scaffolds through a chemical crosslinking method. The results showed that the composite scaffolds have the ability to promote cell adhesion and proliferation. The incorporation of BG resulted in a significant increase in apatite-forming and osteogenesis differentiation abilities. In vivo results indicated that the Ta–GelMA–BG scaffolds significantly enhanced the osteointegration at the early stage after implantation. Overall, the Ta–GelMA–BG scaffolds are a promising platform for the load bearing bone regeneration field.

Three-Dimensional Zirconia-Based Scaffolds for Load-Bearing Bone-Regeneration Applications: Prospects and Challenges.

The design of zirconia-based scaffolds using conventional techniques for bone-regeneration applications has been studied extensively. Similar to dental applications, the use of three-dimensional (3D) zirconia-based ceramics for bone tissue engineering (BTE) has recently attracted considerable attention because of their high mechanical strength and biocompatibility. However, techniques to fabricate zirconia-based scaffolds for bone regeneration are in a stage of infancy. Hence, the biological activities of zirconia-based ceramics for bone-regeneration applications have not been fully investigated, in contrast to the well-established calcium phosphate-based ceramics for bone-regeneration applications. This paper outlines recent research developments and challenges concerning numerous three-dimensional (3D) zirconia-based scaffolds and reviews the associated fundamental fabrication techniques, key 3D fabrication developments and practical encounters to identify the optimal 3D fabrication technique for obtaining 3D zirconia-based scaffolds suitable for real-world applications. This review mainly summarized the articles that focused on in vitro and in vivo studies along with the fundamental mechanical characterizations on the 3D zirconia-based scaffolds.

Hybrid porous zirconia scaffolds fabricated using additive manufacturing for bone tissue engineering applications

For the formation of new bone in critical-sized bone defects, bioactive scaffolds with an interconnected porous network are necessary. Herein, we fabricated three-dimensional (3D) porous hybrid zirconia scaffolds to promote hybrid functionality, i.e., excellent mechanical properties and bioactive performance. Specifically, the 3D printed scaffolds were subjected to Zn-HA/glass composite coating on glass-infiltrated zirconia (ZC). In addition, to pertain the extracellular matrix of bone, biopolymer (alginate/gelatine) was embedded in a developed 3D construct (ZB and ZCB). A zirconia-printed scaffold (Z) group served as a control. The structural and mechanical properties of the constructed scaffolds were studied using essential characterization techniques. Furthermore, the biological performance of the designed scaffolds was tested by a sequence of in vitro cell tests, including the attachment, proliferation, and osteogenic differentiation of dental pulp cells (DPCs). The ZC and ZCB scaffolds exhibited 20% higher compression strength than the zirconia (Z) scaffolds. More importantly, the ZC constructs exhibited superior cell-adhesion, distribution, and osteogenic differentiation ability due to the synergistic effects of the composite coating. In addition, the biopolymer-embedded scaffolds (ZB, ZCB) showed an excellent biological and mechanical performance. Thus, our results suggest that the Zn-HA/glass composite-coated glass-infiltrated zirconia (ZC, ZCB) scaffolds are a dynamic approach to designing bioactive 3D scaffolds for the load-bearing bone regeneration applications.

A modular design strategy to integrate mechanotransduction concepts in scaffold-based bone tissue engineering

Repair or regeneration of load-bearing bones has long been an incentive for the tissue engineering community to develop a plethora of synthetic bone scaffolds. Despite the key role of physical forces and the mechanical environment in bone regeneration, the mechanotransduction concept has rarely been incorporated in structural design of bone tissue scaffolds, particularly those made of bioactive materials such as hydrogels and bioceramics. Herein, we introduce a modular design strategy to fabricate a load bearing device that can support a wide range of hydrogel- and ceramic-based scaffolds against complex in-vivo loading conditions to induce desirable mechanical strains for bone regeneration within the scaffolds. The device is comprised of a fenestrated polymeric shell and ceramic structural pillars arranged in a sophisticated configuration to provide ample internal space for the scaffold, also enabling it to purposely regulate the levels of strains and stresses within the scaffolds. Utilizing this top-down design approach, we demonstrate that the failure load of alginate hydrogels increases 3200-fold in compression, 300-fold in shear and 75-fold in impact, achieving the values that enable them to withstand physiological loads in weight-bearing sites, while allowing generation of osteoinductive strains (i.e., 0.2-0.4%) in the hydrogel. This modular design approach opens a broad range of opportunities to utilize various bioactive but mechanically weak scaffolds for the treatment of load-bearing defects and exploiting mechanobiology strategies to improve bone regeneration.

Bioinspired Biomaterials with a Brick-and-Mortar Microstructure Combining Mechanical and Biological Performance.

The fabrication of bone regeneration biomaterials, which simultaneously possess superior mechanical performances and excellent bioactivity, remains challenging because these properties are usually mutually exclusive. Herein, inspired by the brick-and-mortar architecture of nacre, lamellar silicate-based bioceramic composites are successfully prepared by constructing orderly layered bioceramics infiltrated with a biomedical resin interlayer via the bidirectional freezing technique. The lamellar composites possess high strength and proper Young's moduli, which match with human cortical bone. Furthermore, the lamellar composites can release bioactive ions with a controlled profile, which significantly enhance the cell proliferation of both rabbit bone mesenchymal stem cells and periodontal ligament cells in vitro. Moreover, with the degradation of silicate bioceramics in vivo, newly formed bone tissue can grow into the materials to present the bioceramic/new bone/resin sandwich-like lamellar microstructure. The silicate-based bioceramic composites with brick-and-mortar architecture represent an excellent biomaterial in combination of superior mechanical performances matching that of human cortical bone, and excellent bioactivity for potential load-bearing bone regeneration.

Strontium ion reinforced bioceramic scaffold for load bearing bone regeneration.

Bone defects in load bearing areas require bone reconstruction with strong biomaterial having mechanical characteristics like cortical bone. Bioceramics are biomaterials that support bone formation as well as provide adequate mechanical properties. A strontium substitution of the bioceramic is expected to further increase its bioactivity by enhancing osteogenesis and protect the bone from osteoclastic resorption. The study involves development, characterization and in vivo testing of a newly developed strontium substituted hydroxyapatite based bioceramic scaffold (SrHAB) with sufficient biomechanical properties. Optimal concentration of strontium ion required for enhanced osteogenic differentiation was identified by comparing three compositions of SrHAB scaffold; namely Sr10HAB, Sr30HAB and Sr50 HAB for their Alkaline phosphatase activity in vitro. The selected Sr10HAB scaffold demonstrated in vivo bone formation with osteogenic differentiation of stromal derived mesenchymal stem cells (MSC) from human and ovine sources in ectopic and ovine models. Thus, Sr10HAB scaffold has a potential for application in load bearing bone requirements of orthopaedics and dentistry.

A novel route for the synthesis of macroporous bioceramics for bone regeneration

A novel forming process based on direct foaming of ceramic suspensions was set up and optimized to produce highly porous hydroxyapatite (HA) scaffolds. A high-energy planetary ball milling was used to obtain stable foamed suspensions and to shorten the whole process, in comparison to previous approaches. The new process enabled the introduction of air bubbles in the ceramic suspension in tailored volume and size thus giving rise, upon sintering, to HA bodies with open and interconnected porosity associated with remarkable mechanical properties (e.g. a compressive strength σ=16.3±4.3MPa was exhibited by HA bodies with 65% pore volume). The reliability of the process in obtaining scaffolds was also assessed by the analysis of Weibull modulus. On this basis, this process can be considered as a novel promising route to develop macro-porous apatite scaffolds for regeneration of load-bearing bones, thus opening to new regenerative therapies for still unmet clinical needs.

Improving PEEK bioactivity for craniofacial reconstruction using a 3D printed scaffold embedded with mesenchymal stem cells.

Polyetheretherketone (PEEK) is a bioinert thermoplastic that has been investigated for its potential use in craniofacial reconstruction; however, its use in clinical practice is limited by a poor integration with adjacent bone upon implantation. To improve the bone-implant interface, two strategies have been employed: to modify its surface or to impregnate PEEK with bioactive materials. This study attempts to combine and improve upon the two approaches by modifying the internal structure into a trabecular network and to impregnate PEEK with mesenchymal stem cells. Furthermore, we compare the newly designed PEEK scaffolds' interactions with both bone-derived (BMSC) and adipose (ADSC) stem cells. Customized PEEK scaffolds were designed to incorporate a trabecular microstructure using a computer-aided design program and then printed via selective laser sintering (SLS), a 3D-printing process with exceptional accuracy. The scaffold structure was evaluated using microCT. Scanning electron microscopy (SEM) was used to evaluate scaffold morphology with and without mesenchymal stem cells (MSCs). Adipose and bone marrow mesenchymal cells were isolated from rats and cultured on scaffolds. Cell proliferation and differentiation were assessed using alamarBlue and alkaline phosphatase assays, respectively. Cell morphology after one week of co-culturing cells with PEEK scaffolds was evaluated using SEM. SLS 3D printing fabricated scaffolds with a porosity of 36.38% ± 6.66 and density of 1.309 g/cm(2). Cell morphology resembled viable fibroblasts attaching to the surface and micropores of the scaffold. PEEK scaffolds maintained the viability of both ADSCs and BMSCs; however, ADSCs demonstrated higher osteodifferentiation than BMSCs (p < 0.05). This study demonstrates for the first time that SLS 3D printing can be used to fabricate customized porous PEEK scaffolds that maintain the viability of adipose and bone marrow-derived MSCs and induce the osteodifferentiation of the adipose-derived MSCs. The combination of 3D printed PEEK scaffolds with MSCs could overcome some of the limitations using PEEK biopolymers for load-bearing bone regeneration in craniofacial reconstruction.

Macroporous and nanofibrous PLLA scaffolds reinforced with calcium phosphate-coated multiwalled carbon nanotubes

Scaffolds with both macro- and nanoscale structures have shown promise in tissue engineering; however, their mechanical properties are not satisfactory for load-bearing bone regeneration. In this study, calcium phosphate-coated multiwalled carbon nanotubes (MWCNTs-CaP) were developed to reinforce macroporous poly(L-lactide) (PLLA) scaffolds with nanofibrous pore walls. The scaffolds were prepared using a phase separation/particle-leaching method. One-dimensional MWCNTs-CaP were prepared via phosphorylation and mineralization. The addition of the MWCNTs-CaP did not affect the nanofibrous pore walls of the resulting PLLA scaffolds. In comparison with pure PLLA scaffolds, the compressive properties of PLLA/MWCNTs-CaP composite scaffolds were significantly improved, indicating their potential in bone regeneration applications.

Injectable Photocrosslinkable Nanocomposite Based on Poly(Glycerol Sebacate) Fumarate and Hydroxyapatite: Development, Biocompatibility and Bone Regeneration in A Rat Calvarial Bone Defect Model

An injectable, photocrosslinkable nanocomposite was prepared using a fumarate derivative of poly(glycerol sebacate) and nanohydroxyapatite. Polymers with varying physical and mechanical properties were synthesized. Furthermore, nanocomposites were developed using a homogenization process by combining nanohydroxyapatite within poly(glycerol sebacate) matrix via photocrosslinking and evaluated both in vitro and in vivo. The nanocomposites were injectable, highly bioactive and biocompatible. Addition of nanohydroxyapatite led to enhanced mechanical properties with an ultimate strength of 8 MPa. The optimized nanocomposite showed good in vitro cell attachment, proliferation and differentiation of rat bone marrow-derived mesenchymal stem cells. The in vivo evaluation in a rat calvarial bone defect model showed significantly high alkaline phosphatase activity and bone regeneration. This injectable, biocompatible and bioactive in situ hardening composite graft was found to be suitable for load-bearing bone regeneration applications using minimally invasive surgery.

Non-rigid calcium phosphate cement containing hydrogel microbeads and absorbable fibres seeded with umbilical cord stem cells for bone engineering

The need for bone repair has increased as the population ages. Non-rigid calcium phosphate scaffolds could provide compliance for micro-motions within the tissues and yet have load-supporting strength. The objectives of this study were to: (a) develop a non-rigid calcium phosphate cement (CPC) with microbeads and fibre reinforcement; and (b) investigate human umbilical cord mesenchymal stem cell (hUCMSC) proliferation, osteodifferentiation and mineralization on non-rigid CPC for the first time. Non-rigid CPC was fabricated by adding extra tetracalcium phosphate in the traditional CPC and by incorporating chitosan, absorbable fibres and hydrogel microbeads. The non-rigid CPC-microbead scaffold possessed a strain-at-failure of 10.7%, much higher than the traditional CPC's strain of 0.05% which is typical for brittle bioceramics. Flexural strength of non-rigid CPC-microbead was 4-fold that of rigid CPC-microbead scaffold, while work-of-fracture (toughness) was increased by 20-fold. The strength of non-rigid CPC-microbead-fibre scaffold matched that of cancellous bone. hUCMSCs on non-rigid CPC proliferated from 100 cells/mm(2) at 1 day to 600 cells/mm(2) at 8 days. Alkaline phosphatase, osteocalcin and collagen gene expressions of hUCMSCs were greatly increased, and the cells synthesized bone minerals. hUCMSCs on non-rigid CPC-microbead-fibre constructs had higher bone markers and more mineralization than those on rigid CPC controls. In conclusion, this study developed the first non-rigid, in situ-setting calcium phosphate-microbead-fibre scaffold with a strain-at-failure exceeding 10%. hUCMSCs showed excellent proliferation, osteodifferentiation and mineralization on non-rigid CPC scaffold. The novel non-rigid CPC-hUCMSC construct with good strength, high strain-at-failure and toughness, as well as superior stem cell proliferation, osteodifferentiation and mineralization, is promising for load-bearing bone regeneration applications.

Porous and strong bioactive glass (13–93) scaffolds fabricated by freeze extrusion technique

Scaffolds fabricated by current methods often lack the combination of high strength and high porosity for skeletal substitution of load-bearing bones. In this work, freeze extrusion fabrication (FEF), a solid freeform fabrication technique, was investigated for the creation of porous and strong bioactive glass (13–93) scaffolds for potential applications in the repair of loaded bone. The process parameters for forming three-dimensional (3D) scaffolds with a pre-designed, grid-like microstructure by FEF were determined. Following thermal treatment of the as-formed constructs at temperatures up to 700 °C, scaffolds consisting of dense glass struts and interconnecting pores (porosity ≈ 50%; pore width ≈ 300 μm) were obtained. These scaffolds showed an elastic mechanical response in compression, with a compressive strength of 140 ± 70 MPa and an elastic modulus of 5.5 ± 0.5 GPa, comparable to the values for human cortical bone. The scaffolds supported the proliferation of osteogenic cells in vitro, showing their biocompatibility. These results indicate that 13–93 bioactive glass scaffolds created by the FEF method could have potential application in the repair and regeneration of load-bearing bones.

Bone Repair Using a Hybrid Scaffold of Self-Assembling Peptide PuraMatrix and Polyetheretherketone Cage in Rats

Self-assembling peptide scaffold (SAPS) is well known to have very good bone conduction properties. However, the intensity of SAPS is too weak to actually use it for a clinical bone regeneration. Therefore, we have produced a hybrid scaffold system that involves fabricating a cage from polyetheretherketone (PEEK) that has high intensity, filling the interior of this cage with SAPS, and then transplanted this hybrid scaffold to bone defects in rat femurs. After 28 days, soft X-ray radiographs and histological assessment revealed that good new bone formation was clearly observed in the defects transplanted the PEEK cage with SAPS, but not in the PEEK cage only. The PEEK cage maintained a form and osteoconduction ability of internal SAPS, and SAPS promoted bone formation inside the PEEK; therefore, each was in charge of intensity and bone regeneration separately. The present study suggests that hybrid scaffolds made from PEEK cages and SAPS can be useful tools for the regeneration of load-bearing bones, based on the idea that it should be possible to develop ideal bone filler materials by combining the strength of artificial bone with the bone regeneration and bone conduction properties of SAPS.

Preparation and in vitro evaluation of bioactive glass (13–93) scaffolds with oriented microstructures for repair and regeneration of load‐bearing bones

Bioactive glass (13-93) scaffolds with oriented microstructures, referred to as 'columnar' and 'lamellar', were prepared by unidirectional freezing of suspensions, and evaluated in vitro for potential use in the repair and regeneration of load-bearing bones in vivo. Both groups of scaffolds showed an 'elastic-plastic' mechanical response in compression, large strain for failure (>20%), and strain rate sensitivity, but the columnar scaffolds had the additional advantages of higher strength and larger pore width. At the equivalent porosity (55-60%) and deformation rate (0.5 mm/min), the columnar scaffolds had a compressive strength of 25 +/- 3 MPa, elastic modulus of 1.2 GPa, and pore width of 90-110 microm, compared to values of 10 +/- 2 MPa, 0.4 GPa, and 20-30 microm, respectively, for the lamellar scaffolds. Cellular response to the scaffolds was evaluated using murine MLO-A5 cells, an osteogenic cell line. While the cellular response to both groups of scaffolds was better than control wells, the columnar scaffolds with the larger pore width provided the most favorable substrate for cell proliferation and function. These results indicate that 13-93 bioactive glass scaffolds with the columnar microstructure could be used for the repair and regeneration of load-bearing bones in vivo.

Bioinspired structure of bioceramics for bone regeneration in load-bearing sites

The major problem with the use of porous bioceramics as bone regeneration grafts is their weak mechanical strength, which has not been overcome to date. Here we described a novel way to solve this problem. Beta-tricalcium phosphate (β-TCP) bioceramics with a bioinspired structure were designed and prepared with a porous cancellous core (porosity: 70–90%) inside and a dense compact shell (porosity: 5–10%) outside that mimics the characteristics of natural bone. They showed excellent mechanical properties, with a compressive strength of 10–80 MPa and an elastic modulus of 180 MPa–1.0 GPa, which could be tailored by the dense/porous cross-sectional area ratio obeying the rule of exponential growth. The in vitro degradation of the bioinspired bioceramics was faster than that of dense bioceramics but slower than that of porous counterparts. The changes in mechanical properties of the bioinspired ceramics during in vitro degradation were also investigated. A concept of the bioinspired macrostructure design of natural bone was proposed which provided a simple but effective way to increase the mechanical properties of porous bioceramics for load-bearing bone regeneration applications. It should be readily applicable to other porous materials.