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Objective To study mechanical properties of porous scaffolds with lattice Weaire-Phelan (LWP) structure and precisely simulate the whole process of compression test using finite element method. Methods The Ti6Al4V (TC4) porous scaffolds with different porosities were manufactured by selective laser melting (SLM) technology, and their mechanical properties were measured by uniaxial compressive tests, and compared with those of human bones and porous scaffolds with other cellular structures. Four types of material models were verified for their effects on the simulation of porous scaffold compression. Results LWP samples presented the elastic modulus close to that of human cancellous bone and significantly higher yield strength than that of cortical bone in most parts of human body. Compared with other scaffold structures, LWP samples exhibited the lowest elastic modulus and highest yield strength. The simulated results derived from the proposed material model in this study, namely, Johnson-Cook constitutive model and failure model based on dynamic geometric strain (JCDG), were proved very consistent with the experimental data. Conclusions LWP scaffolds as the bone repair biomaterials exhibite more excellent mechanical properties than the scaffolds with other structures. JCDG is more beneficial for establishing the reasonable simulation model of porous scaffolds compression, compared with other reported material models.
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BACKGROUND: The three-dimensional organic/inorganic scaffold materials using polymer/bioceramic composites can endow the necessary physical and chemical properties and enhance the mechanical properties of the materials. However, most bone substitution materials cannot prevent infection at the defect site. It has been found that the degradation of magnesium can produce local alkaline environment, so that magnesium has certain antibacterial activity. OBJECTIVE: To investigate the in vitro antibacterial activity and cytocompatibility of magnesium-containing scaffolds. METHODS: Polylactic acid/β-tricalcium phosphate/magnesium porous scaffolds were prepared by low-temperature rapid prototyping technology. The PTM (2:1) and PTM (1:2) groups referred to two mixing mass ratios (β-tricalcium phosphate:magnesium = 2:1 and 1:2), respectively. Two scaffolds of polylactic acid (P group) and polylactic acid/β-tricalcium phosphate (PT group) were also prepared by low-temperature rapid prototyping technology. The surface morphology, pore size, porosity and compression modulus of the scaffolds were measured. Staphylococcus aureus (ATCC 35923) was seeded on the scaffolds of each group for 24 hours. The antibacterial activity of the scaffolds was observed through spread plate method and confocal laser scanning microscopy. Mouse preosteoblasts MC3T3-E1 were co-cultured with the scaffolds of each group. The cell attachment and proliferation were evaluated by cell counting kit-8 assay. RESULTS AND CONCLUSION: (1) A relatively uniform porous structure was found on the scaffold surfaces in each group. There were no significant differences in the pore size and porosity among groups (P > 0.05). (2) The compression modulus in the PTM (2:1) and PTM (1:2) groups were significantly higher than those in the P and PT groups (P 0.05). (4) After 6 hours of culture, the number of attached cells in the PT, PTM (2:1) and PTM (1:2) groups was greater than that in the P group (P 0.05). (5) At 1 day of culture, the cell proliferation in the PT group was superior to that in the P group (P 0.05). (6) These results indicate that the polylactic acid/β-tricalcium phosphate/magnesium scaffold not only possesses good antibacterial activity, but also exhibits excellent cytocompatibility and certain anti-compressive ability.
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The high elastic modulus of scaffolds or implants will result in stress shielding effect, which may lead to bone resorption and scaffold or implant loosening in the late stage. Porous scaffolds and implants can adjust their porosity and elastic modulus according to the mechanical environment, thereby reducing stress shielding; meanwhile, porous structures are beneficial to bone tissue growth, which is conducive to osseointegration. Three kinds of basic structure for porous scaffolds and implants by 3D printing were summarized, namely, uniform porous structure, bone-like trabecular structure and functionally graded structure. The design methods of these structures were introduced respectively, including computer-aided design (CAD)-based, implicit surface-based, image-based and topology optimization-based design method, so as to provide references for solving the stress shielding problem, as well as designing porous scaffolds and implants.
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Objective To investigate the biomechanical behavior of porous scaffold with different materials (Ti, Ta, PEEK, HA) for repairing rabbit femur defects under immediate loading by three-dimensional finite element analysis (FEA), so as to explore the best porous scaffold material from the perspective of biomechanics. Methods The CBCT combined with software such as Mimics, SolidWorks, Geomagic Studio, ANSYS were used to establish an immediate loading model for the repair of rabbit femur defects with porous scaffolds at different stages of bone healing. The stress and strain distributions on the scaffolds and the surrounding tissues were calculated. Results The maximum equivalent stress of porous scaffold decreased along with the bone healing. In the granulation tissue and fibrous tissue model, the ratio of the maximum equivalent stress to the yield strength of porous scaffold was: HA＞Ta＞PEEK＞Ti. The maximum equivalent stress of the HA porous scaffold was greater than its yield strength. The number of suitable strain elements in tissues around the porous scaffolds was: PEEK＞Ta＞Ti＞HA. The number of potential fracture strain elements in tissues around the porous scaffolds was: HA＞Ta＞PEEK＞Ti. Conclusions The HA porous scaffold could not bear the immediate load and guide bone healing well under immediate loading. The elastic modulus of PEEK porous scaffold was similar to that of bone tissues, which could preferably guide bone healing. PEEK was an ideal porous scaffold material under immediate loading. The research findings provide
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The high elastic modulus of scaffolds or implants will result in stress shielding effect, which may lead to bone resorption and scaffold or implant loosening in the late stage. Porous scaffolds and implants can adjust their porosity and elastic modulus according to the mechanical environment, thereby reducing stress shielding; meanwhile, porous structures are beneficial to bone tissue growth, which is conducive to osseointegration. Three kinds of basic structure for porous scaffolds and implants by 3D printing were summarized, namely, uniform porous structure, bone-like trabecular structure and functionally graded structure. The design methods of these structures were introduced respectively, including computer-aided design (CAD)-based, implicit surface-based, image-based and topology optimization-based design method, so as to provide references for solving the stress shielding problem, as well as designing porous scaffolds and implants.
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Objective: To investigate the possibility and effect of chitosan porous scaffolds combined with bone marrow mesenchymal stem cells (BMSCs) in repair of neurological deficit after traumatic brain injury (TBI) in rats. Methods: BMSCs were isolated, cultured, and passaged by the method of bone marrow adherent culture. The 3rd generation BMSCs were identified by the CD29 and CD45 surface antigens and marked by 5-bromo-2-deoxyuridine (BrdU). The chitosan porous scaffolds were produced by the method of freeze-drying. The BrdU-labelled BMSCs were co-cultured in vitro with chitosan porous scaffolds, and were observed by scanning electron microscopy. MTT assay was used to observe the cell growth within the scaffold. Fifty adult Sprague Dawley rats were randomly divided into 5 groups with 10 rats in each group. The rat TBI model was made in groups A, B, C, and D according to the principle of Feeney's free fall combat injury. Orthotopic transplantation was carried out at 72 hours after TBI. Group A was the BMSCs and chitosan porous scaffolds transplantation group; group B was the BMSCs transplantation group; group C was the chitosan porous scaffolds transplantation group; group D was the complete medium transplantation group; and group E was only treated with scalp incision and skull window as sham-operation group. Before TBI and at 1, 7, 14, and 35 days after TBI, the modified neurological severity scores (mNSS) was used to measure the rats' neurological function. The Morris water maze tests were used after TBI, including the positioning voyage test (the incubation period was detected at 31-35 days after TBI, once a day) and the space exploration test (the number of crossing detection platform was detected at 35 days after TBI). At 36 days after TBI, HE staining and immunohistochemistry double staining [BrdU and neurofilament triplet H (NF-H) immunohistochemistry double staining, and BrdU and glial fibrillary acidic protein (GFAP) immunohistochemistry double staining] were carried out to observe the transplanted BMSCs' migration and differentiation in the damaged brain areas. Results: Flow cytometry test showed that the positive rate of CD29 of the 3rd generation BMSCs was 98.49%, and the positive rate of CD45 was only 0.85%. After co-cultured with chitosan porous scaffolds in vitrofor 48 hours, BMSCs were spindle-shaped and secreted extracellular matrix to adhere in the scaffolds. MTT assay testing showed that chitosan porous scaffolds had no adverse effects on the BMSCs' proliferation. At 35 days after TBI, the mNSS scores and the incubation period of positioning voyage test in group A were lower than those in groups B, C, and D, and the number of crossing detection platform of space exploration test in group A was higher than those in groups B, C, and D, all showing significant differences ( P0.05). HE staining showed that the chitosan porous scaffolds had partially degraded, and they integrated with brain tissue well in group A; the degree of repair in groups B, C, and D were worse than that of group A. Immunohistochemical double staining showed that the transplanted BMSCs could survive and differentiate into neurons and glial cells, some differentiated neural cells had relocated at the normal brain tissue; the degree of repair in groups B, C, and D were worse than that of group A. Conclusion: The transplantation of chitosan porous scaffolds combined with BMSCs can improve the neurological deficit of rats following TBI obviously, and also inhabit the glial scar's formation in the brain damage zone, and can make BMSCs survive, proliferate, and differentiate into nerve cells in the brain damage zone.
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[Abstract ] Objective At present, the majority of injectable tissue engineering bones or carrier stents are gel , whose surface area , intensity, and hardness cannot satisfy the requirements of the repair of complex and varied bone and cartilage defects .This paper evaluated the new injectable microspherical porous chitosan/biological properties of the hydroxyapatite ceramic scaffold . Methods Injectable porous chitosan /hydroxyapatite composite microspheres with mass fractions of 30%, 50%, and 70% were prepared respectively . The hydroxyapatite ceramic ball was obtained by sintering with liquid nitrogen freezing ( liquid nitrogen group ) or without liquid nitrogen pro-cessing ( non-liquid nitrogen group ) as a new carrier of bone tissue engineering scaffold material .The microstructure of the scaffold was observed and the porosity measured under the scanning electron microscope .The mechanical properties were determined through biome-chanical experiments.Human umbilical vein endothelial cells (HUVECs) were grown in the porous chitosan/hydroxyapatite ceramic scaf-fold followed by observation of the growth of the cells and validation of the biological fusion of the scaffold . Results No difference was observed with the naked eye in the ceramic scaffold of different mass fractions in the liquid nitrogen and non -liquid nitrogen groups . Scanning electron microscopy exhibited spherical shape , uniform size, and regular morphology of the ceramic scaffolds in both groups .A large number of irregular pores were seen in the surface of the microspherical ceramic scaffolds treated with liquid nitrogen but not in the surface of those not treated .With increased mass percentage of chitosan/hydroxyapatite , the internal pores were reduced and the interior structure compacted.In the liquid nitrogen group, the scaffold of 50%mass fraction had a significantly larger diameter ([0.48 ±0.11] mm), higher compression intensity ([1.75 ±0.14] MPa), and lower porosity ([79 ±2]%) than that of 30%mass fraction ([0.40 ± 0.08] mm, [1.21 ±0.12] MPa, and [87 ±1]%) (all P<0.05).Electron microscope scanning revealed well -grown HUVECs with multiple synapses in the porous tricalcium phosphate scaffold. C onclusion The porous chitosan /hydroxyapatite ceramic scaffold of 50%mass fraction treated with liquid nitrogen , with its strong mechanical intensity and high biological fusibility , can be used as a new carrier of bone tissue engineering scaffolds .
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Magnesium alloys have been a hotspot in the field of implanted medical devices due to their biodegradable absorbability, excellent mechanical properties and good biocompatibility.The reduction in their rapid corrosion rates becomes the key to the application of implant medical device materials.In this paper, the latest research progress and the existing problems of magnesium alloys as the material for implantation of medical devices in the fracture internal fixation, bone tissue porous scaffold, and cardiovascular stent are reviewed.Improving corrosion resistant of magnesium alloys by means of alloying, improving purity, surface modification,rapid solidification, deformation processing, non crystallization and preparation of nano alloy technology in body fluid are expounded, and research direction and application prospect of magnesium alloys in the field of implanted medical devices are also expected.
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<p><b>OBJECTIVE</b>To develop a dressing with desired antibacterial activity, good water maintaining ability and mechanical properties for wound healing and skin regeneration.</p><p><b>METHODS</b>The chitosan with different concentrations were added in keratin solution to form porous keratin/chitosan (KCS) scaffolds. The morphological characteristics, chemical composition, wettability, porosity, swelling ratio and degradation of the scaffolds were evaluated. The antibacterial activity was tested by using S. aureus and E. coli suspension for 2 h. And L929 fibroblast cells culture was used to evaluate the cytotoxicity of the KCS scaffolds.</p><p><b>RESULTS</b>The adding of chitosan could increase the hydrophobicity, decrease porosity, swelling ratio and degradation rate of the KCS porous scaffolds. Mechanical properties of KCS scaffolds could be enhanced and well adjusted by chitosan. KCS scaffolds could obviously decrease bacteria number. The proliferation of fibroblast cells in porous KCS patch increased firstly and then decreased with the increase of chitosan concentration. It was appropriate to add 400 μg/mL chitosan to form porous KCS scaffold for achieving best cell attachment and proliferation compared with other samples.</p><p><b>CONCLUSION</b>The porous KCS scaffold may be used as implanted scaffold materials for promoting wound healing and skin regeneration.</p>
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Humans , Anti-Bacterial Agents , Bandages , Cell Line , Cell Proliferation , Chitosan , Fibroblasts , Cell Biology , Keratins , Microscopy, Electron, Scanning , Porosity , Spectroscopy, Fourier Transform Infrared , Wound HealingABSTRACT
PURPOSE: The purpose of this study was to evaluate the properties of a porous zirconia scaffold coated with bioactive materials and compare the in vitro cellular behavior of MC3T3-E1 preosteoblastic cells to titanium and zirconia disks and porous zirconia scaffolds. MATERIALS AND METHODS: Titanium and zirconia disks were prepared. A porous zirconia scaffold was fabricated with an open cell polyurethane disk foam template. The porous zirconia scaffolds were coated with beta-TCP, HA and a compound of beta-TCP and HA (BCP). The characteristics of the specimens were evaluated using scanning electron microscopy (SEM), energy dispersive x-ray spectrometer (EDX), and x-ray diffractometry (XRD). The dissolution tests were analyzed by an inductively coupled plasma spectrometer (ICP). The osteogenic effect of MC3T3-E1 cells was assessed via cell counting and reverse transcriptase-polymerase chain reaction (RT-PCR). RESULTS: The EDX profiles showed the substrate of zirconia, which was surrounded by the Ca-P layer. In the dissolution test, dissolved Ca2+ ions were observed in the following decreasing order; beta-TCP > BCP > HA (P<.05). In the cellular experiments, the cell proliferation on titanium disks appeared significantly lower in comparison to the other groups after 5 days (P<.05). The zirconia scaffolds had greater values than the zirconia disks (P<.05). The mRNA level of osteocalcin was highest on the non-coated zirconia scaffolds after 7 days. CONCLUSION: Zirconia had greater osteoblast cell activity than titanium. The interconnecting pores of the zirconia scaffolds showed enhanced proliferation and cell differentiation. The activity of osteoblast was more affected by microstructure than by coating materials.
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Cell Count , Cell Differentiation , Cell Proliferation , Ions , Microscopy, Electron, Scanning , Osteoblasts , Osteocalcin , Plasma , Polyurethanes , RNA, Messenger , TitaniumABSTRACT
Background: Scaffolds for bone tissue engineering must meet functional requirements, porosity, biocompatibility, and biodegradability. Different polymeric scaffolds have been designed to satisfy these properties. Composite materials could improve mechanical properties compared with polymers, and structural integrity and flexibility compared with brittle ceramics. Objective: Fabricate poly (lactic-co-glycolic acid) (PLGA) /hydroxyapatite (HA) porous scaffolds by freezeextraction method, and evaluate the possibility for optimizing their biocompatibility by changing their HA content. Methods: Porous PLGA/HA composites structure were prepared by freezing a polymer solution, and then the solvent was extracted by a non-solvent and subsequently air-dried. The scaffolds were coated with triblock copolymer and sterilized by ultraviolet light. Human mesenchymal stem cells were cultured on the prepared scaffolds and were studied after three days by 4, 6-diamidino-2-phenylindole (DAPI) fluorescence microscopy. Results: Microstructural studies with SEM showed the formation of about 50 micrometer size porous structure and interconnected porosity so that cells were adhered well into the structure of the coated samples. DAPI fluorescence microscopy showed more cell adhesion to the coated scaffolds and cell diffusion into the pores are visible. Direct assay of cell proliferation performed with MTT test showed cell growing on the scaffold similar to or more than on control samples. Conclusion: The triblock-coated PLGA/HA porous scaffolds may provide cell adhesion and proliferation, demonstrating their potential application in bone engineering.