Scaffolds For Soft Tissue Engineering Research Articles

Systematic selection of solvents for the fabrication of 3D combined macro- and microporous polymeric scaffolds for soft tissue engineering

In this study, we investigate the fabrication of 3D porous poly(lactic-co-glycolic acid) (PLGA) scaffolds using the thermally-induced phase separation technique. The current study focuses on the selection of alternative solvents for this process using a number of criteria, including predicted solubility, toxicity, removability and processability. Solvents were removed via either vacuum freeze-drying or leaching, depending on their physical properties. The residual solvent was tested using gas chromatography-mass spectrometry. A large range of porous, highly interconnected scaffold architectures with tunable pore size and alignment was obtained, including combined macro- and microporous structures and an entirely novel 'porous-fibre' structure. The morphological features of the most promising poly(lactic-co-glycolic acid) scaffolds were analysed via scanning electron microscopy and X-ray micro-computed tomography in both two and three dimensions. The Young's moduli of the scaffolds under conditions of temperature, pH and ionic strength similar to those found in the body were tested and were found to be highly dependent on the architectures.

Fiber-Based Chitosan Tubular Scaffolds for Soft Tissue Engineering: Fabrication and in Vitro Evaluation

Porous, two-ply tubular chitosan conduits for guided tissue regeneration were fabricated by combining the textile technique (inner layer) with the thermally induced phase separation process (outer layer). A hollow chitosan tube was prepared using an industrial warp knitting process with chitosan yarns. Then, an appropriate diameter mandrel was inserted into the pre-fabricated tube. The tube and the mandrel were dipped into the chitosan solution together, taken out, and freeze-dried. After being neutralized in alkaline solution and dried at room temperature, the mandrel was removed to create the chitosan tubular scaffold. Scanning electron micrographs show that the resulting tubes have a biphasic wall structure, with a fibrous inner layer and a semipermeable outer layer. The swelling properties and the mechanical strength before and after in vitro degradation were investigated. The biocompatibility of the scaffolds was also investigated by co-culturing neuroblastoma cells (N2A, mouse) with the scaffolds. The results suggest that these chitosan tubular scaffolds are useful for the regeneration of tissues requiring a tubular scaffold.

Preparation of Electrospun PLA Nanofiber Scaffold and the Evaluation In Vitro

A electrospinning process to prepare soft tissue engineering scaffold was introduced in this study. This kind of scaffold was composed with ultrathin fiber and characterized with high porosity, well-interconnected pores and high surface-to-volume ratio. Biodegradable polylaticacid (PLA) was used to spin the scaffold and the scaffold was evaluated in vitro by analysis the microscopic structure, porosity, mechanical property, especially cytocompatibility. The results indicated that the electrospun PLA scaffold showed good cytocompatibility and the tensile property of electrospun scaffold was similar to human’s soft tissue. It could be expected that the electrospun scaffold would be potential in soft tissue engineering or soft tissue repair.

Architecture control of three-dimensional polymeric scaffolds for soft tissue engineering. I. Establishment and validation of numerical models.

One of the most important functions of artificial three-dimensional (3D) polymeric scaffolds is to serve as a physical support to provide tissues with an appropriate architecture for in vitro cell culture as well as in vivo tissue regeneration. The production of three-dimensional (3D) polymeric scaffolds with tailored macroporous architecture is thus a crucial step in promoting controlled vascularization and tissue growth within host environments. In this study, 3D poly(lactic-co-glycolic acid) (PLGA) scaffolds were manufactured by a thermally induced phase-separation (TIPS) technique. By controlling the quenching strategy, 3D interconnected PLGA scaffolds with tunable pore size and alignment were obtained and characterized with the use of scanning electron microscopy (SEM). A series of numerical heat-transfer models were established in an effort to describe the cooling process within the PLGA freezing regime. Among them, a two-dimensional (2D) solidification model has proved to be the most successful in describing the quenching of the polymer solution and has the potential to be used to infer the various 3D macroporous architectures created from different quenching conditions.

Preparation and characterisation of poly(lactide-co-glycolide) (PLGA) and PLGA/Bioglass® composite tubular foam scaffolds for tissue engineering applications

Polylactide-co-glycolide (PLGA) and PLGA/Bioglass® foams of tubular shape have been prepared with a 1 wt.% 45S5 Bioglass® content. Porous membranes with varying thickness and porosity were fabricated via a thermally induced phase separation process, from which tubes of controlled diameter and wall thickness in the range 1.5–3 mm were produced. Scanning electron microscopy (SEM) revealed that the structure of the tubular foams consisted of radially oriented and highly interconnected pores with two distinct pore sizes, i.e. macropores ∼100-μm average diameter and interconnected micropores of 10–50-μm diameter. Foams with Bioglass® inclusions showed similarly well-defined tubular and interconnected pore morphology. Cell culture studies using mouse fibroblasts (L929) were conducted to assess the biocompatibility of the scaffolds in vitro. L929 fibroblasts cultured in medium that was pre-conditioned by incubating with PLGA tubes containing Bioglass® had a significant reduction in cell proliferation compared with fibroblasts grown in unconditioned medium ( p<0.0001). The PLGA and PLGA/Bioglass® tubular foams developed here are candidate materials for soft-tissue engineering scaffolds, holding promise for the regeneration of tissues requiring a tubular shape scaffold, such as intestine, trachea and blood vessels.

Assessment of polyglycolic acid mesh and bioactive glass for soft-tissue engineering scaffolds

Sufficient neovascularization of neotissue is currently a limiting factor for the engineering of large tissue constructs. 45S5 Bioglass ® has been investigated extensively in bone tissue engineering but there has been relatively little previous research on its application to soft-tissue engineering. The objectives of this study were to investigate the use of 45S5 Bioglass ® in soft-tissue engineering scaffolds using in vitro and in vivo models. A fibroblast cell line (208F) was used for in vitro evaluation of surfaces coated with 45S5 Bioglass ®. Increased proliferation of fibroblasts was observed after growth on polystyrene surfaces coated with low concentrations (0.01–0.2% wt/vol) of 45S5 Bioglass ® for 24 h in vitro, determined as a change in total cell number by measuring lactate dehydrogenase. At higher concentrations of 45S5 Bioglass ® and longer periods of incubation (48 and 72 h) on coated surfaces, cell proliferation was reduced. Light microscopy revealed that the morphology of fibroblasts grown on 45S5 Bioglass ®-coated surfaces was not altered at low concentrations, but at higher concentrations fibroblasts became vacuolated. Enzyme-linked immunosorbent assay of conditioned culture medium collected from fibroblasts grown for 24 h on surfaces coated with low concentrations of 45S5 Bioglass ® (0.01% wt/vol) was found to contain significantly higher concentrations of vascular endothelial growth factor. Histological examination of polyglycolic acid (PGA)/45S5 Bioglass ® composite scaffolds that had been implanted subcutaneously into rats revealed that 45S5 Bioglass ®-coated meshes were well tolerated. Light microscopy revealed that neovascularization into 45S5 Bioglass ®-coated meshes was significantly increased at 28 and 42 days. Electron microscopy revealed fibroblasts adhering closely to the PGA mesh but not to 45S5 Bioglass ® particles. The apparent ability of 45S5 Bioglass ® incorporated into scaffolds to increase neovascularization would be extremely beneficial during the engineering of larger soft-tissue constructs.

Production and surface modification of polylactide-based polymeric scaffolds for soft-tissue engineering.

Production and surface modification of polylactide-based polymeric scaffolds for soft-tissue engineering.

In vitro release kinetics of proteins from bioactive foams.

This study describes an approach to obtaining 3-D scaffolds for tissue engineering that allows the incorporation and release of biologically active proteins to stimulate cell function. Laminin was adsorbed on the textured surfaces of binary 70S30C (70 mol % SiO(2), 30 mol % CaO) and ternary 58S (60 mol % SiO(2), 36 mol % CaO, 4 mol % P(2)O(5)) foams. The covalent bonds between the binding sites of the proteins and the ligands on the scaffolds' surfaces did not denaturate the proteins. In vitro studies show that the foams modified with chemical groups and coated with laminin were bioactive, as demonstrated by the formation of a crystalline hydroxy carbonate apatite (HCA) layer formed on the surfaces of the foams upon exposure to simulated body fluid (SBF). The release of proteins from the foams also was investigated. Sustained and controlled release from the scaffolds over a 30-day period was achieved. Laminin release from the bioactive foams followed the dissolution rate of the material network. These results suggest that bioactive foams have the potential to act as scaffolds for soft-tissue engineering with a controlled release of proteins that can induce tissue formation or regeneration.

Biodegradable elastomeric scaffolds for soft tissue engineering

Elastomeric copolymers of 1,3-trimethylene carbonate (TMC) and ε-caprolactone (CL) and copolymers of TMC and d,l-lactide (DLLA) have been evaluated as candidate materials for the preparation of biodegradable scaffolds for soft tissue engineering. TMC-DLLA copolymers are amorphous and degrade more rapidly in phosphate-buffered saline (PBS) of pH 7.4 at 37 °C than (semi-crystalline) TMC-CL copolymers. TMC-DLLA with 20 or 50 mol% TMC loose their tensile strength in less than 5 months and are totally resorbed in 11 months. In PBS, TMC-CL copolymers retain suitable mechanical properties for more than a year. Cell seeding studies show that rat cardiomyocytes and human Schwann cells attach and proliferate well on the TMC-based copolymers. TMC-DLLA copolymers with either 20 or 50 mol% of TMC are totally amorphous and very flexible, making them excellent polymers for the preparation of porous scaffolds for heart tissue engineering. Porous structures of TMC-DLLA copolymers were prepared by compression molding and particulate leaching techniques. TMC-CL (co)polymers were processed into porous two-ply tubes by means of salt leaching (inner layer) and fiber winding (outer layer) techniques. These grafts, seeded with Schwann cells, will be used as nerve guides for the bridging of large peripheral nerve defects.

Elastomeric biodegradable polyurethane blends for soft tissue applications

Four biodegradable polyurethane blends were made from segmented polyurethanes that contain amino acid-based chain extender and diisocyanate groups. The soft segments of these parent polyurethanes were either polyethylene oxide (PEO) or polycaprolactone (PCL) diols. The blends were developed to investigate the effect of varying soft segment compositions on the overall morphological, mechanical, and degradative properties of the materials, with a view to producing a family of materials with a wide range of properties. The highly hydrophilic PEO material was incorporated to increase the blend's susceptibility to degradation, while the PCL polyurethane was selected to provide higher moduli and percent elongations (strains) than the PEO parent materials can achieve. All four blends were determined to be semi-crystalline, elastomeric materials that possess similarly shaped stress-strain curves to that of the PCL-based parent polyurethane. As the percent composition of PEO polyurethane within the blend increased, the material became weaker and less extensible. The blends demonstrated rapid initial degradation in buffer followed by significantly slower, prolonged degradation, likely corresponding to an initial loss of primarily PEO-containing polymer, followed by the slower degradation of the PCL polyurethane. All four blends were successfully formed into three-dimensional porous scaffolds utilizing solvent casting/particulate leaching methods. Since these new blends possess a range of mechanical and degradation properties and can be shaped into three-dimensional objects, these materials may hold potential for use in soft tissue engineering scaffold applications.