Three dimensional melt-deposition of polycaprolactone/bio-derived hydroxyapatite composite into scaffold for bone repair

Advancements in reliability of mechanical performance of 3D PRINTED Ag-doped bioceramic antibacterial scaffolds for bone tissue engineering

The current gold-standard approach for addressing bone defects in load-bearing applications sees the use of either autographs or allographs. These solutions, however, have limitations as autographs and allographs carry the risk of additional trauma, the threat of disease transmission, and potential donor rejection. An attractive candidate for overcoming the challenges associated with the use of autographs and allographs is a 3D porous scaffold displaying the needed mechanical competency for use in load-bearing applications that can stimulate bone tissue regeneration and provide antibacterial capabilities. To date, no reports document a 3D porous scaffold that fully meets the criteria specified above. In this work, we show how the use of fused filament fabrication (FFF) 3D printing technology in combination with a bimodal distribution of Ag-doped bioactive glass-ceramic (Ag-BG) micro-sized particles can successfully deliver porous 3D scaffolds with attractive and reliable mechanical performance characteristics capable of stimulating bone tissue regeneration and the ability to provide inherent antibacterial properties. To characterize the reliability of the mechanical performance of the FFF-printed Ag-BG scaffolds, Weibull statistics were evaluated for both the compressive (N = 25; m = 13.6 ± 0.9) and flexural (N = 25; m = 7.3 ± 0.7) strengths. Methicillin-resistant Staphylococcus aureus (MRSA) was used both in planktonic and biofilm forms to highlight the advanced antibacterial characteristics of the FFF-printed Ag-BG scaffolds. Biological performance was evaluated in vitro through indirect exposure to human marrow stromal cells (hMSCs), where the FFF-printed Ag-BG scaffolds were found to provide an attractive environment for cell infiltration and mineralization. Our work demonstrates how fused filament fabrication technology can be used with bioactive and antibacterial materials such as Ag-BG to deliver mechanically competent porous 3D scaffolds capable of stimulating bone tissue regeneration while simultaneously providing antibacterial performance capabilities.

A 3D multifunctional bi-layer scaffold to regulate stem cell behaviors and promote osteochondral regeneration

Osteochondral defect (OCD) regeneration remains a great challenge. Recently, multilayer scaffold simulating native osteochondral structures have aroused broad interest in osteochondral tissue engineering. Here, we developed a 3D multifunctional bi-layer scaffold composed of a kartogenin (KGN)-loaded GelMA hydrogel (GelMA/KGN) as an upper layer mimicking a cartilage-specific extracellular matrix and a hydroxyapatite (HA)-coated 3D printed polycaprolactone porous scaffold (PCL/HA) as a lower layer simulating subchondral bone. The bi-layer scaffolds were subsequently modified with tannic acid (TA) prime-coating and E7 peptide conjugation (PCL/HA-GelMA/KGN@TA/E7) to regulate endogenous stem cell behaviors and exert antioxidant activity for enhanced osteochondral regeneration. In vitro, the scaffolds could support cell attachment and proliferation, and enhance the chondrogenic and osteogenic differentiation capacity of bone marrow-derived mesenchymal stem cells (BMSCs) in a specific layer. Besides, the incorporation of TA/E7 significantly increased the biological activity of the bi-layer scaffolds including the pro-migratory effect, antioxidant activity, and the maintenance of cell viability against oxidative stress. In vivo, the developed bi-layer scaffolds enhanced the simultaneous regeneration of cartilage and subchondral bone when implanted into a rabbit OCD model through macroscopic, micro-CT, and histological evaluation. Taken together, these investigations demonstrated that the 3D multifunctional bi-layer scaffolds could provide a suitable microenvironment for endogenous stem cells, and promote in situ osteochondral regeneration, showing great potential for the clinical treatment of OCD.

Marine plankton exoskeletone-derived hydroxyapatite/polycaprolactone composite 3D scaffold for bone tissue engineering

3D porous scaffolds based on biodegradable polymers are one of the materials for bone tissue regeneration. In this study, a porous scaffold was prepared using a solvent casting/particulate leaching method that used polycaprolactone (PCL) and hydroxyapatite (OceanBone-HAp) extracted from a marine plankton exoskeleton to achieve excellent bone regeneration. In this study, the morphology and physicochemical properties of the PCL/OceanBone-HAp scaffolds were evaluated using scanning electron microscopy, X-ray diffraction, and porosity analysis. The results confirmed the porous structure of the scaffold and removal of the solvent and porogen particles. In vitro test results revealed superior cell adhesion, proliferation, and viability of PCL/OceanBone-HAp scaffolds compared to PCL scaffolds alone. The enhanced alkaline phosphatase activity and expression of bone morphogenetic protein 2, collagen type I α 1, osteocalcin, and bone sialoprotein in the PCL/OceanBone-HAp scaffolds were confirmed through ALP and real-time polymerase chain reaction assays. Moreover, in vivo experiments using a rabbit calvarial defect model showed that the PCL/OceanBone-HAp scaffold exhibited enhanced bone regeneration compared to the PCL scaffold. Therefore, the PCL/OceanBone-HAp scaffold is a promising scaffold for bone repair.

Fabrication, morphological, mechanical and biological performance of 3D printed poly(ε-caprolactone)/bioglass composite scaffolds for bone tissue engineering applications

Several techniques, such as additive manufacturing, have been used for the manufacture of polymer-ceramic composite scaffolds for bone tissue engineering. A new extruder head recently developed for improving the manufacturing process is an experimental 3D printer Fab@CTI that enables the use of ceramic powders in the processing of composite materials or polymer blends. Still, the manufacturing process needs improvement to promotes the dispersion of ceramic particles in the polymer matrix. This article addresses the manufacture of scaffolds by 3D printing from mixtures of poly(ε-caprolactone) (PCL) and a glass powder of same composition of 45S5Bioglass®, labeled as synthesized bioglass (SBG), according to two different methods that investigated the efficiency of the new extruder head. The first one is a single extrusion process in a Fab@CTI 3D printer, and the other consists in the pre-processing of the PCL-SBG mixture in a mono-screw extruder with a Maddock^®element, followed by direct extrusion in the experimental Fab@CTI 3D printer. The morphological characterization of the extruded samples by SEM showed an architecture of 0o/90o interconnected struts and suitable porosity for bone tissue engineering applications. Scaffolds fabricated by two methods shows compressive modulus ranging from 54.4 ± 14.2 MPa to 155.9 ± 20.4 MPa, results that are compatible to use in bone tissue engineering. Cytotoxicity assays showed non-toxic effects and viability for in vitro MG-63 cell proliferation. Alizarin Red staining test showed calcium deposition in all scaffolds, which suggests PCL/SBG composites promising candidates for use in bone tissue engineering. Results of cell morphology suggest more cell growth and adhesion for scaffolds fabricated using the pre-processing in a mono-screw extruder.

Effect of high content nanohydroxyapatite composite scaffolds prepared via melt extrusion additive manufacturing on the osteogenic differentiation of human mesenchymal stromal cells

The field of bone tissue engineering seeks to mimic the bone extracellular matrix composition, balancing the organic and inorganic components. In this regard, additive manufacturing (AM) of high content calcium phosphate (CaP)-polymer composites holds great promise towards the design of bioactive scaffolds. Yet, the biological performance of such scaffolds is still poorly characterized. In this study, melt extrusion AM (ME-AM) was used to fabricate poly(ethylene oxide terephthalate)/poly(butylene terephthalate) (PEOT/PBT)-nanohydroxyapatite (nHA) scaffolds with up to 45 wt% nHA, which presented significantly enhanced compressive mechanical properties, to evaluate their in vitro osteogenic potential as a function of nHA content. While osteogenic gene upregulation and matrix mineralization were observed on all scaffold types when cultured in osteogenic media, human mesenchymal stromal cells did not present an explicitly clear osteogenic phenotype, within the evaluated timeframe, in basic media cultures (i.e. without osteogenic factors). Yet, due to the adsorption of calcium and inorganic phosphate ions from cell culture media and simulated body fluid, the formation of a CaP layer was observed on PEOT/PBT-nHA 45 wt% scaffolds, which is hypothesized to account for their bone forming ability in the long term in vitro, and osteoconductivity in vivo.

Phosphorous pentoxide-free bioactive glass exhibits dose-dependent angiogenic and osteogenic capacities which are retained in glass polymeric composite scaffolds

Bioactive glasses (BGs) are attractive materials for bone tissue engineering because of their bioactivity and osteoinductivity. In this study, we report the synthesis of a novel phosphorous pentoxide-free, silicate-based bioactive glass (52S-BG) composed of 52.1% SiO₂, 23.2% Na₂O and 22.6% CaO (wt%). The glass was thoroughly characterized. The biocompatibility and osteogenic properties of 52S-BG particles were analyzed in vitro with human adipose-derived mesenchymal stem cells (AdMSCs) and human osteoblasts. 52S-BG particles were biocompatible and induced mineralized matrix deposition and the expression of osteogenic markers (RunX2, alkaline phosphatase, osteocalcin, osteopontin, collagen I) and the angiogenic marker vascular endothelial growth factor (VEGF). Angiogenic properties were additionally confirmed in a zebrafish embryo model. 52S-BG was added to poly-ε-caprolactone (PCL) to obtain a composite with 10 wt% glass content. Composite PCL/52S-BG scaffolds were fabricated by additive manufacturing and displayed high porosity (76%) and pore interconnectivity. The incorporation of 52S-BG particles increased the Young's modulus of PCL scaffolds from 180 to 230 MPa. AdMSC seeding efficiency and proliferation were higher in PCL/52S-BG compared to PCL scaffolds, indicating improved biocompatibility. Finally, 52S-BG incorporation improved the scaffolds' osteogenic and angiogenic properties by increasing mineral deposition and inducing relevant gene expression and VEGF protein secretion. Overall, 52S-BG particles and PCL/52S-BG composites may be attractive for diverse bone engineering applications requiring concomitant angiogenic properties.

An interleukin-4-loaded bi-layer 3D printed scaffold promotes osteochondral regeneration

Multilayer scaffolds fabricated by 3D printing or other techniques have been used to repair osteochondral defects. However, it remains a challenge to regenerate the articular cartilage and subchondral bone simultaneously with higher performance. In the present study, we enhanced the repair efficiency of osteochondral defects by developing a bi-layer scaffold: an interleukin-4 (IL-4)-loaded radially oriented gelatin methacrylate (GelMA) scaffold printed with digital light processing (DLP) in the upper layer and a porous polycaprolactone and hydroxyapatite (PCL-HA) scaffold printed with fused deposition modeling (FDM) in the lower layer. An in vitro test showed that both layers supported cell adhesion and proliferation, as the lower layer promoted osteogenic differentiation and the upper layer with IL-4 relieved the negative effects of inflammation on murine chondrocytes, which were induced by interleukin-1β (IL-1β) and M1 macrophages. In a rabbit osteochondral defect repair model, the IL-4-loaded bi-layer scaffold group obtained the highest histological score (24 ± 2) compared to the nontreated (11 ± 1) and pure bi-layer scaffold (16 ± 1) groups after 16 weeks of implantation, which showed that the IL-4-loaded bi-layer scaffold promoted regeneration of both cartilage and subchondral bone with increased formation of neocartilage and neobone tissues. Thus, the IL-4-loaded bi-layer scaffold is an attractive candidate for repair and regeneration of osteochondral defects.

Three-Dimensional-Printed Poly-L-Lactic Acid Scaffolds with Different Pore Sizes Influence Periosteal Distraction Osteogenesis of a Rabbit Skull

The repair of bone defects is a big challenge in reconstructive surgery. Periosteal distraction osteogenesis (PDO), as a promising technique used for bone regeneration, forms a space between the periosteum and bone cortex to regenerate the new bone merely by distracting the periosteum. In order to investigate the influence of distractor framework on the PDO, we utilized three-dimensional (3D) printing technology to fabricate three kinds of poly-L-lactic acid (PLLA) scaffolds with different pore sizes in this study. The in vitro experiments showed that the customized PLLA scaffolds had different-sized microchannels with low toxicity, good biocompatibility, and enough mechanical strength. Then, we built up an in vivo bioreactor under the skull periosteum of New Zealand white rabbits. The distractors with different pore sizes all could satisfy the demand of periosteal distraction in the animal experiments. After 8 weeks of consolidation period, the quality and quantity of the newly formed bone were improved with the increasing pore sizes of the distractors. Moreover, the newly formed bone also displayed an increasing degree of vascularization. In conclusion, 3D printing technology could promote the innovation of PDO devices and fabricate optimized scaffolds with appropriate pore sizes, shapes, and structures. It would help us regenerate more functional tissue-engineered bone and provide new ideas for further clinical application of the PDO technique.

A three-dimensional hydroxyapatite/polyacrylonitrile composite scaffold designed for bone tissue engineering

In recent years, various composite scaffolds based on hydroxyapatite have been developed for bone tissue engineering. However, the poor cell survival micro-environment is still the major problem limiting their practical applications in bone repairing and regeneration. In this study, we fabricated a class of fluffy and porous three-dimensional composite fibrous scaffolds consisting of hydroxyapatite and polyacrylonitrile by employing an improved electrospinning technique combined with a bio-mineralization process. The fluffy structure of the hydroxyapatite/polyacrylonitrile composite scaffold ensured the cells would enter the interior of the scaffold and achieve a three-dimensional cell culture. Bone marrow mesenchymal stem cells were seeded into the scaffolds and cultured for 21 days in vitro to evaluate the response of cellular morphology and biochemical activities. The results indicated that the bone marrow mesenchymal stem cells showed higher degrees of growth, osteogenic differentiation and mineralization than those cultured on the two-dimensional hydroxyapatite/polyacrylonitrile composite membranes. The obtained results strongly supported the fact that the novel three-dimensional fluffy hydroxyapatite/polyacrylonitrile composite scaffold had potential application in the field of bone tissue engineering.

A fluffy and porous (3D) HA composite fibrous scaffold was fabricated by employing an improved electrospinning technique combined with a bio-mineralization process.

Three dimensional printed polylactic acid-hydroxyapatite composite scaffolds for prefabricating vascularized tissue engineered bone: An in vivo bioreactor model

The repair of large bone defects with complex geometries remains a major clinical challenge. Here, we explored the feasibility of fabricating polylactic acid-hydroxyapatite (PLA-HA) composite scaffolds. These scaffolds were constructed from vascularized tissue engineered bone using an in vivo bioreactor (IVB) strategy with three-dimensional printing technology. Specifically, a rabbit model was established to prefabricate vascularized tissue engineered bone in two groups. An experimental group (EG) was designed using a tibial periosteum capsule filled with 3D printed (3DP) PLA-HA composite scaffolds seeded with bone marrow stromal cells (BMSCs) and crossed with a vascular bundle. 3DP PLA-HA scaffolds were also combined with autologous BMSCs and transplanted to tibial periosteum without blood vessel as a control group (CG). After four and eight weeks, neovascularisation and bone tissues were analysed by studying related genes, micro-computed tomography (Micro-CT) and histological examinations between groups. The results showed that our method capably generated vascularized tissue engineered bone in vivo. Furthermore, we observed significant differences in neovascular and new viable bone formation in the two groups. In this study, we demonstrated the feasibility of generating large vascularized bone tissues in vivo with 3DP PLA-HA composite scaffolds.

Three dimensional printed macroporous polylactic acid/hydroxyapatite composite scaffolds for promoting bone formation in a critical-size rat calvarial defect model

We have explored the applicability of printed scaffold by comparing osteogenic ability and biodegradation property of three resorbable biomaterials. A polylactic acid/hydroxyapatite (PLA/HA) composite with a pore size of 500 μm and 60% porosity was fabricated by three-dimensional printing. Three-dimensional printed PLA/HA, β-tricalcium phosphate (β-TCP) and partially demineralized bone matrix (DBM) seeded with bone marrow stromal cells (BMSCs) were evaluated by cell adhesion, proliferation, alkaline phosphatase activity and osteogenic gene expression of osteopontin (OPN) and collagen type I (COL-1). Moreover, the biocompatibility, bone repairing capacity and degradation in three different bone substitute materials were estimated using a critical-size rat calvarial defect model in vivo. The defects were evaluated by micro-computed tomography and histological analysis at four and eight weeks after surgery, respectively. The results showed that each of the studied scaffolds had its own specific merits and drawbacks. Three-dimensional printed PLA/HA scaffolds possessed good biocompatibility and stimulated BMSC cell proliferation and differentiation to osteogenic cells. The outcomes in vivo revealed that 3D printed PLA/HA scaffolds had good osteogenic capability and biodegradation activity with no difference in inflammation reaction. Therefore, 3D printed PLA/HA scaffolds have potential applications in bone tissue engineering and may be used as graft substitutes in reconstructive surgery.

A specific groove design for individualized healing in a canine partial sternal defect model by a polycaprolactone/hydroxyapatite scaffold coated with bone marrow stromal cells

The reconstruction of sternal defects remains clinically challenging for thoracic surgeons. Here we aimed to explore the individualized reconstruction of partial sternal defects with new biodegradable material in a large animal model. We used the fused deposition modeling (FDM) technique to manufacture polycaprolactone/hydroxyapatite (PCL/HA) tissue scaffolds with individualized grooves to repair the sternal defect. The defects were surgically created in a sternocostal joint of eighteen Beagle dogs. The animals were separated into three groups (n = 6): Blank group, PCL/HA group, and PCL/HA/BMSCs group. Radiographic examination, histological, and histomorphometric analyses were performed to evaluate the result. In the blank group, the defect site couldn't maintain its original integrity due to no bone union. In the PCL/HA group and PCL/HA/BMSCs group, it was observed that the scaffolds retained their shapes without significant degradation at 12 weeks. Both groups could observe new bone-union by radiographic and histological examination. And PCL/HA/BMSCs would be more mineralized tissue area at implant sites (p < 0.05). These results reveal that using the FDM technique to manufacture the PCL/HA scaffolds with specific grooves could repair the sternal defect satisfactorily. Furthermore the scaffolds with BMSCs-seeded could enhance the amount of bone ingrowth and seemed to be more promising.