Ultrasonication‐Induced Modification of Hydroxyapatite Nanoparticles onto a 3D Porous Poly(lactic acid) Scaffold with Improved Mechanical Properties and Biocompatibility

A 3D porous poly(lactic acid) (PLA) scaffold with high porosity and well‐connected pores is fabricated using a vacuum‐assisted solvent casting technique. Its surface is modified with hydroxyapatite (HA) nanoparticles using ultrasonication to prepare an HA‐modified PLA/HA scaffold. For reference, an HA‐blended (b‐PLA‐HA) scaffold is fabricated via the solution blending method. The morphology, porosity, hydrophilicity, swelling ratio, mechanical properties, and cell viability of the PLA, b‐PLA‐HA, and PLA/HA scaffolds are systematically studied. The results show that HA nanoparticles are successfully introduced onto the surface of the PLA/HA scaffold, and strong interactions occur between the HA nanoparticles and the PLA matrix. The PLA/HA scaffold still has a high porosity of more than 85% after ultrasonication. The hydrophilicity and mechanical properties of the PLA/HA scaffold are significantly higher than those of the PLA and b‐PLA‐HA scaffolds. Compared with the PLA and b‐PLA‐HA scaffolds, the attachment and growth of mouse embryonic osteoblasts cells (MC3T3‐E1) cultured on the PLA/HA scaffold significantly improve, due to most HA nanoparticles on the surface, resulting in a good and direct interaction between the cells and the scaffold. Therefore, the PLA/HA scaffold possesses great potential to be used as a tissue engineering scaffold.     

Electrospun polylactide/silk fibroin–gelatin composite tubular scaffolds for small‐diameter tissue engineering blood vessels

Many synthetic scaffolds have been used as vascular substitutes for clinical use. However, many of these scaffolds may not show suitable properties when they are exposed to physiologic vascular environments, and they may fail eventually because of some unexpected conditions. Electrospinning technology offers the potential for controlling the composition, structure, and mechanical properties of scaffolds. In this study, a tubular scaffold (inner diameter = 4.5 mm) composed of a polylactide (PLA) fiber outside layer and a silk fibroin (SF)–gelatin fiber inner layer (PLA/SF–gelatin) was fabricated by electrospinning. The morphological, biomechanical, and biological properties of the composite scaffold were examined. The PLA/SF–gelatin composite tubular scaffold possessed a porous structure; the porosity of the scaffold reached 82 ± 2%. The composite scaffold achieved the appropriate breaking strength (1.28 ± 0.21 MPa) and adequate pliability (elasticity up to 41.11 ± 2.17% strain) and possessed a fine suture retention strength (1.07 ± 0.07 N). The burst pressure of the composite scaffold was 111.4 ± 2.6 kPa, which was much higher than the native vessels. A mitochondrial metabolic assay and scanning electron microscopy observations indicated that both 3T3 mouse fibroblasts and human umbilical vein endothelial cells grew and proliferated well on the composite scaffold in vitro after they were cultured for some days. The PLA/SF–gelatin composite tubular scaffolds presented appropriate characteristics to be considered as candidate scaffolds for blood vessel tissue engineering. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Tetracycline hydrochloride-containing poly (ε-caprolactone)/poly lactic acid scaffold for bone tissue engineering application: in vitro and in vivo study

In the current study, tetracycline hydrochloride (TCH), an antibiotic against most of the medically relevant bacteria, was incorporated into poly (ε-caprolactone)/poly lactic acid solution in order to develop a composite scaffold with both antibacterial and osteoinductive properties for the repair of infected bone defects. The composite scaffolds were produced from poly (ε-caprolactone) (PCL) and poly lactic acid (PLA) solution (1:1 (w/w)) incorporated with 3, 5, and 10% (w/w) of TCH by thermally induced phase separation technique. The scaffolds were evaluated regarding their morphology, wettability, porosity, degradation, mechanical properties, and cellular response. The scaffold containing 10% of TCH (PCL/PLA/TCH10%) was chosen as the optimum scaffold for further investigation in a rat femoral defect model. The study showed that after eight weeks, the bone formation was relatively higher in PCL/PLA/TCH10%-treated group with completely filled defect when compared with control (PCL/PLA scaffold without TCH). Histopathological evaluation showed that the defect in PCL/PLA/TCH10%-treated group was fully replaced by new bone and connective tissue. Our results provide evidence supporting the possible applicability of TCH-containing scaffolds for successful bone regeneration.     

Solvent-Free Fabrication of Tissue Engineering Scaffolds With Immiscible Polymer Blends

A completely organic solvent-free fabrication method is developed for tissue engineering scaffolds by gas foaming of immiscible polylactic acid (PLA) and sucrose blends, followed by water leaching. PLA scaffolds with above 90% porosity and 25–200 µm pore size were fabricated. The pore size and porosity was controlled with process parameters including extrusion temperature and foaming process parameters. Dynamic mechanical analysis showed that the extrusion temperature could be used to control the scaffold strength. Both unfoamed and foamed scaffolds were used to culture glioblastoma (GBM) cells M059 K. The results showed that the cells grew better in the foamed PLA scaffolds. The method presented in the paper is versatile and can be used to fabricate tissue engineering scaffolds without any residual organic solvents.     

3D Composite scaffolds using strontium containing bioactive glasses

In this study, it was aimed to fabricate and characterize three-dimensional composite scaffolds derived from Sr-doped bioactive glass for bone tissue engineering applications. The scaffolds were fabricated by using polymer foam replication technique and coated with gelatin to be able to improve the properties of them. The porous scaffolds were successfully synthesized using optimized process parameters. Both coated and uncoated scaffolds favored precipitation of calcium phosphate layer when they were soaked in simulated body fluid (SBF). Gelatin coating improved the mechanical properties of the scaffold and also it did not change the bioactive behavior of the scaffold. It was observed that there was a good pore interconnectivity maintained in the scaffold microstructure. Results indicated that scaffolds can deliver controlled doses of strontium toward the SBF medium. That is the determinant for bone tissue regeneration, as far as strontium is known to positively act on bone remodeling.     

Development of bone scaffold using Puntius conchonius fish scale derived hydroxyapatite: Physico-mechanical and bioactivity evaluations

Naturally derived Hydroxyapatite (HAp) from fish scale is finding wide applications in the development of bone scaffold to promote bone regeneration. But porous HAp scaffold is fragile in nature making it unsuitable for bone repair or replacement applications. Thus, it is essential to improve the mechanical property of HAp scaffolds while retaining the interconnected porous structure for tissue ingrowth in vivo. In this study solvent casting particulate leaching technique is used to develop novel Puntius conchonius fish scale derived HAp bone scaffold by varying the wt.% of the HAp from 60 to 80% in PMMA matrix. Physico-chemical, mechanical, structural and bioactive properties of the developed scaffolds are investigated. The obtained results indicate that HAp-PMMA scaffold at 70?wt % HAp loading shows optimal properties with 7.26?±?0.45?MPa compressive strength, 75?±?0.8% porosity, 8.0?±?0.68% degradation and 190?±?11% water absorption. The obtained results of the scaffold can meet the physiological demands to guide bone regeneration. Moreover, in vitro bioactivity analysis also confirms the formation of bone like apatite in the scaffold surface after 28 days of SBF immersion. Thus, the developed scaffold has the potential to be effectively used in bone tissue engineering applications.     

Effect of particle size and freezing conditions on freeze-casted scaffold

Freeze casting is one of the emerging and novel manufacturing routes to fabricate porous scaffolds for various applications including orthopedic implants, drug delivery, energy storing devices etc. Thus, it becomes important to understand this process in a deeper sense. Present work was focused to study the effect/influence of basic parameters, particle sizes, and freezing conditions on the mechanical properties and microstructures of porous scaffold fabricated by freeze casting. β-tricalcium phosphate (β-TCP) and hydroxyapatite (HAp) powder with particle sizes of 10?μm and 20?nm were used. Prepared slurries were freeze casted at constant freezing temperature (5?°C) and constant freezing rate (1.86?°C/min) to study the effect of freezing conditions on mechanical and microstructural properties of the porous scaffold. It was observed that porous scaffold fabricated by nanoparticles has given better porosity (63.22–76.16%), than scaffold fabricated by microparticles (13–43.05%) at given solid loading of both freezing conditions. Although, the range of pore size of the scaffold fabricated by nanoparticles (CFR: 2.60–0.84?μm; CFT: 1.66–0.46?μm) was lower than that of scaffold fabricated by microparticles (CFR: 9.45–4.83?μm; CFT: 4.72–2.84?μm). The compressive strength of scaffolds prepared by nanoparticles was in the range of trabecular bone. Moreover, the results of present work will pave the way for the fabrication of porous scaffold with desired pore size and porosity for various implants, energy, and drug delivery applications.     

Preparation and characterization of poly ε-caprolactone-gelatin/multi-walled carbon nanotubes electrospun scaffolds for cartilage tissue engineering applications

Abstract

Designing scaffolds with appropriate mechanical properties is a challenge in tissue engineering. In this study the poly ε-caprolactone (PCL)/gelatin with 1?wt.% of multi-walled carbon nanotubes (MWNTs) fabricated through electrospinning method. The presence of MWNTs led to an increase in the hydrophilicity and tensile strength, while maintaining an appropriate level of porosity percentage. The bioactivity and biodegradation evaluation demonstrated that the scaffolds containing MWNTs presented more bioactivity and slower degradation rate. Cell culture study showed that the nanocomposite scaffolds did not have any cytotoxicity. According to the results, the PCL-gelatin/MWNTs nanocomposite scaffold can be appropriate for cartilage tissue engineering applications.     

Fabrication of porous scaffolds with a controllable microstructure and mechanical properties by porogen fusion technique

Macroporous scaffolds with controllable pore structure and mechanical properties were fabricated by a porogen fusion technique. Biodegradable material poly (d, l-lactide) (PDLLA) was used as the scaffold matrix. The effects of porogen size, PDLLA concentration and hydroxyapatite (HA) content on the scaffold morphology, porosity and mechanical properties were investigated. High porosity (90% and above) and highly interconnected structures were easily obtained and the pore size could be adjusted by varying the porogen size. With the increasing porogen size and PDLLA concentration, the porosity of scaffolds decreases, while its mechanical properties increase. The introduction of HA greatly increases the impact on pore structure, mechanical properties and water absorption ability of scaffolds, while it has comparatively little influence on its porosity under low HA contents. These results show that by adjusting processing parameters, scaffolds could afford a controllable pore size, exhibit suitable pore structure and high porosity, as well as good mechanical properties, and may serve as an excellent substrate for bone tissue engineering.     

Fabrication and performance of calcium phosphate cement/small intestinal submucosa composite bionic bone scaffolds with different microstructures

The microstructure of the tissue has a very important determining effect on its performance. Herein, two calcium phosphate cement (CPC)/small intestinal submucosa(SIS) composites bionic bone scaffolds with different microstructures were fabricated by rolling or/ and assembling method. The microstructure, 3D morphology, the crystal phase and mechanical properties of the scaffolds were investigated by micro CT, XRD, FIIR, SEM and electronic universal testing machines respectively. The results showed that the pore size of all scaffolds are in the range of 100–400?µm, which are beneficial to cells growth, migration, and tissue vascularization. Their porosity and the specific surface area were 14.53?±?0.76%, 8.74?±?1.38?m²/m³ and 32?±?0.58%, 26.75?±?2.69?m²/m³ separately. The high porosity and the large specific surface area can provide a larger space and contact area for cells adhesion and proliferation. Meanwhile, compressive strength of the scaffolds soaked were 10?MPa and 27?MPa, about 1.2 folds and 3.2 folds of the original scaffolds, respectively. The results are derived from different microstructures of the scaffolds and chemical bonds between SIS and new phases (hydroxyapatite), and the scaffolds performance steadily increased at near the physiological conditions. Finally, biocompatibility of the scaffolds was evaluated by CCK8, bionic microstructure scaffolds are no cytotoxicity and their biocompatibility is favorable. Based on the microstructure, compressive strength and cytotoxicity of the scaffolds, bionic Harvarsin microstructure CPC/SIS composite scaffold is expected to turn into a scaffold with the excellent properties of real bone.     

Surface Modification of Electrospun TPU Nanofiber Scaffold with CNF Particles by Ultrasound‐Assisted Technique for Tissue Engineering

A straightforward, fast, and versatile technique is developed to fabricate nanofibrous scaffold with excellent hydrophilicity, mechanical properties, and biocompatibility for tissue engineering. The thermoplastic polyurethane (TPU) nanofiber is fabricated by utilizing electrospinning, and then its surface is modified through simply immersing it into cellulose nanofibrils (CNF) dispersion and subjecting to ultrasonication. The results show that the CNF particles are successfully absorbed on the surface of TPU nanofiber. By introducing CNF particles on the surface of TPU nanofiber, the hydrophilicity, mechanical properties of fabricated CNF‐absorbed TPU scaffold are significantly increased. Additionally, the adhesion and proliferation of human umbilical vein endothelial cells cultured on CNF‐absorbed TPU scaffold are prominently enhanced in comparison with those of cultured on TPU scaffold. These findings suggest that the ultrasound‐assisted technique opens up a new way to simply and effectively modify the surface of various scaffolds and the modified scaffold could be shown a great potential in tissue engineering.     

Cells integration onto scaffolds prepared from polyester based polymers – importance of polymer thermal properties in addition to hydrophilicity

Abstract

Three-dimensional (3D) scaffolds represent valuable tools for biological studies and tissue engineering applications. They offer better biological environment that better mimic 3?D dynamic in vivo conditions compared with conventional bidimentional (2D) cell culture systems. The integration of cells within the scaffolds is, however, dependent on their properties. In the present study, porous scaffolds were prepared from poly lactide (PLA), poly lactide polyethylene glycol copolymer (PLA-PEG) and poly lactide-co-glycolide – polyethylene glycol copolymer (PLGA-PEG) using porogen leaching method with NaCl particles as porogen. The three scaffolds were prepared with identical conditions (concentration, dimensions, porogen weight fraction and particle size) in order to evaluate the impact of polymer composition and properties on scaffold characteristics (internal architecture and pores distribution), as well as fibroblasts integration and proliferation within the scaffold 3?D network. The impact of hydrophilicity, water uptake and protein adsorption are discussed. The data shows that amorphous polymers, which have glass transition temperature close to cell culture temperature, may be advantageous for scaffold construction and cell integration. This fact needs to be considered when interpreting data of cell interaction with scaffolds obtained using amorphous polymers developed for 3?D cell culture and tissue engineering applications.     

Fabrication of a porous wall and higher interconnectivity scaffold comprising gelatin/chitosan via combination of salt-leaching and lyophilization methods

A novel gelatin/chitosan scaffold with higher porosity and interconnectivity was designed through salt-leaching/lyophilization (SLL) method. The properties of the fabricated scaffolds were compared with conventional scaffolds, which are obtained by thermally induced phase-separation (TIPS) method. The scaffolds made by phase-separation method have high tensile strength, but suffer from less channel interconnectivity, pore uniformity and also low surface porosity. The microstructure, porosity, phosphate-buffered saline (PBS) solution absorption and tensile strength of the prepared scaffolds by SLL method were studied. In this work, SLL as a two-step technique is introduced for creating porosity to improve both channel interconnectivity and pore uniformity for water-soluble polymers in comparison with the TIPS method. The SLL technique includes two mechanisms: the first, leaching of mixed sodium chloride crystals and particles created during recrystallization of the dissolved NaCl and the second, phase separation during lyophilization at the pore walls. These two steps in porosity formation lead to special pore morphology, which is more suitable for cell culturing because of higher interconnectivity and rich surface porosity in comparison with the phase-separated scaffolds. The prepared scaffolds, using this technique with different salt/polymer ratios and salt crystal size, have 91?C97% porosity and 94?C190???m mean pore size with tensile strength of 72?C215?kPa and PBS solution absorption between 12.4 and 19 times dry weight. The pore size of scaffolds prepared using the SLL method could be adjusted independently of polymer solution concentration. These scaffolds have a great potential in skin tissue engineering application.     

Characterisation of Bioglass based foams developed via replication of natural marine sponges

A comparative characterisation of Bioglass based scaffolds for bone tissue engineering applications developed via a replication technique of natural marine sponges as sacrificial template is presented, focusing on their architecture and mechanical properties. The use of these sponges presents several advantages, including the possibility of attaining higher mechanical properties than those scaffolds made by foam replica method (up to 4?MPa) due to a decrease in porosity (68–76%) without affecting the pore interconnectivity (higher than 99%). The obtained pore structure possesses not only pores with a diameter in the range 150–500?μm, necessary to induce bone ingrowth, but also pores in the range of 0–200?μm, which are requested for complete integration of the scaffold and for neovascularisation. In this way, it is possible to combine the main properties that a three-dimensional scaffold should have for bone regeneration: interconnected and high porosity, adequate mechanical properties and bioactivity.     

Fabrication of polylactic acid/polyethylene glycol (PLA/PEG) porous scaffold by supercritical CO2 foaming and particle leaching

PLA/PEG/NaCl blends were melt‐blended followed by gas foaming and particle leaching process to fabricate porous scaffold with high porosity and interconnectivity. A home‐made triple‐screw compounding extruder was used to intensify the mixability and dispersion of NaCl and PEG in the PLA matrix. Supercritical carbon dioxide was used as physical blowing agent for the microcellular foaming process. Sodium chloride (NaCl) was used as the porogen to further improve the porosity of PLA scaffold. This study investigated the effects of PEG and NaCl on the structure and properties of the PLA‐based blend, as well as the porosity, pore size, interconnectivity, and hydrophilicity of porous scaffolds. It was found that the incorporation of PEG and NaCl significantly improved the crystallization rate and reduced viscoelasticity of PLA. Moreover, scaffolds obtained from PLA/PEG/NaCl blends had an interconnected bimodal porous structure with the open‐pore content about 86% and the highest porosity of 80%. And the presence of PEG in PLA/NaCl composite improved the extraction ability of NaCl particles during leaching process, which resulted in a well‐interconnected structure. The biocompatibility of the porous scaffolds fabricated was verified by culturing fibroblast cells for 10 days. POLYM. ENG. SCI., 55:1339–1348, 2015. © 2015 Society of Plastics Engineers     

Bioactive Ceramic/Polyamide 6 Scaffold for Bone Regeneration: In vitro and in vivo Evaluation

A porous scaffold of bio-ceramic/polyamide 6 (PA 6) has been fabricated through a thermally induced phase separation technique. The scaffold was characterized by XPS, SEM and mechanical test. The results revealed that bio-ceramic/PA 6 scaffold had an interconnected porous structure with a porosity of about 78%. Moreover, bio-ceramic/PA 6 scaffolds were cultured with BMSCs to investigate their in vitro cytocompatibility, and they were implanted in subcutaneous sites of mice for 4 and 8 weeks to evaluate their in vivo histocompatibility. The result showed the composite scaffolds provided a favourable environment for initial cell adhesion, maintained cell viability and cell proliferation, and had good tissue compatibility.     

Laser‐made 3D Auxetic Metamaterial Scaffolds for Tissue Engineering Applications

Exploiting the unique properties of three‐dimensional (3D) auxetic scaffolds in tissue engineering and regenerative medicine applications provides new impetus to these fields. Herein, the results on the fabrication and characterization of 3D auxetic scaffolds for tissue engineering applications are presented. The scaffolds are based on the well‐known re‐entrant hexagonal geometry (bowtie) and they are fabricated by multiphoton lithography using the organic?inorganic photopolymer SZ2080. In situ scanning electron microscopy–microindentations and nanoindention experiments are employed to characterize the photocurable resin SZ2080 and the scaffolds fabricated with it. Despite SZ2080 being a stiff material with a positive Poisson’s ratio, the scaffolds exhibit a negative Poisson’s ratio and high elasticity due to their architecture. Next, mouse fibroblasts are used to seed the scaffolds, showing that they can readily penetrate them and proliferate in them, adapting the scaffold shape to suit the cells’ requirements. Moreover, the scaffold architecture provides the cells with a predilection to specific directions, an imperative parameter for regenerative medicine in many cell‐based applications. This research paves the way for the utility of 3D auxetic metamaterials as the next‐generation adaptable scaffolds for tissue engineering.     

改进粒子沥滤法制备PLA/HA支架及其性能

采用溶剂浇铸/真空挥发/粒子沥滤法(SC/VV/PL)制备了聚乳酸(PLA)和PLA/羟基磷灰石(HA)多孔支架,研究了支架的结构、力学性能、亲水性能等.从扫描电镜结果可以看出支架孔径与所用的致孔剂氯化钠(NaCl)的粒径符合良好,PLA和PLA/HA支架的孔隙率均大于79%,压缩模量、接触角、吸水率的测试结果表明,HA的加入显著改善了PLA支架的力学性能和亲水性能.     

Development and Evaluation of Biomimetic 3D Coated Composite Scaffold for Application as Skin Substitutes

Skin injuries are an urgent health issue, which raises a great concern in the clinic. Although numerous strategies have been proposed to fabricate skin substitutes for treatment of wounds over the past several decades, fabricating an ideal skin substitute to replace the damaged one can still be a problem. In this study, a novel biomimetic 3D composite skin scaffold is fabricated by combining electrohydrodynamic (EHD) jetting, electrospinning, and coating techniques. Here, the first polycaprolactone (PCL) porous structure is produced by the EHD jetting. Next, the second polylactic acid (PLA) membrane consisted of nanoscale fibers is prepared on the PCL porous structure via the electrospinning. The PCL porous structure and PLA fibers membrane can mimic the dermis and epidermis layer, respectively. Furthermore, gelatin is used as coating solution to enhance the biocompatibility of the scaffold. The structure and morphology of the fabricated scaffolds are analyzed, and the mechanical properties are investigated as well. Moreover, the in vitro and in vivo experiments demonstrate the biocompatibility of the materials and the fabrication process. In conclusion, these results demonstrate that the composite scaffold is effective and holds great potential for skin regeneration in the clinic.     

3D printed polylactide-based zirconia-toughened alumina composites: fabrication,mechanical, and in vitro evaluation

Fused deposition modeling (FDM) has been a commonly used technique in the fabrication of geometrically complex biodegradable scaffolds for bone tissue engineering. Generally, either individual polylactide (PLA) or its combination with calcium phosphates or bioglass has been employed to design scaffolds through the principles of FDM. In this study, FDM protocol has been employed to design 3D printed PLA/zirconia-toughened alumina (ZTA). A series of PLA/ZTA combinations have been attempted to determine the feasibility of the resultant in filament extrusion and their subsequent capacity to obtain a stable 3D printed component. A maximum of 80 wt.% PLA and 20 wt.% ZTA has been determined as an optimum combination to yield a stable 3D structure beyond which an enhanced ZTA content in the PLA matrix yielded a fragile filament that lacked effectiveness in 3D printing. 5 and 10 wt.% of ZTA addition in the PLA matrix produced a better 3D design that reasonably displayed good mechanical properties. Depending on the ceramic content, a homogeneous dispersion of the constituent elements representative of ZTA has been determined throughout the PLA matrix. Simulation studies through finite element analysis (FEA) exhibited good corroboration with the test results obtained from the mechanical studies.