Silver nanowire loaded poly(ε-caprolactone) nanocomposite fibers as electroactive scaffolds for skeletal muscle regeneration.

Volumetric muscle loss (VML) due to trauma and tumor removal operations affects millions of people every year. Although skeletal muscle has a natural repair mechanism, it cannot provide self-healing above a critical level of VML. In this study, nanocomposite aligned fiber scaffolds as support materials were developed for volumetric skeletal muscle regeneration. For this purpose, silver nanowire (Ag NW) loaded poly(ε-caprolactone) (PCL) nanocomposite fiber scaffolds (PCL-Ag NW) were prepared to mimic the aligned electroactive structure of skeletal muscle and provide topographic and conductive environment to modulate cellular behavior and orientation. A computer-aided rotational wet spinning (RWS) system was designed to produce high-yield fiber scaffolds. Nanocomposite fiber bundles with lengths of 50 cm were fabricated via this computer-aided RWS system. The morphological, chemical, thermal properties and biodegradation profiles of PCL and PCL-Ag NW nanocomposite fibers were characterized in detail. The proliferation behavior and morphology of C2C12 mouse myoblasts were investigated on PCL and PCL-Ag NW nanocomposite fibrous scaffolds with and without electrical stimulation. Significantly enhanced cell proliferation was observed on PCL-Ag NW nanocomposite fibers compared to neat PCL fibers with electrical stimulations of 1.5 V, 3 V and without electrical stimulation.

Recycled algae-based carbon materials as electroconductive 3D printed skeletal muscle tissue engineering scaffolds.

Skeletal muscle is an electrically and mechanically active tissue that contains highly oriented, densely packed myofibrils. The tissue has self-regeneration capacity upon injury, which is limited in the cases of volumetric muscle loss. Several regenerative therapies have been developed in order to enhance this capacity, as well as to structurally and mechanically support the defect site during regeneration. Among them, biomimetic approaches that recapitulate the native microenvironment of the tissue in terms of parallel-aligned structure and biophysical signals were shown to be effective. In this study, we have developed 3D printed aligned and electrically active scaffolds in which the electrical conductivity was provided by carbonaceous material (CM) derived from algae-based biomass. The synthesis of this conductive and functional CM consisted of eco-friendly synthesis procedure such as pre-carbonization and multi-walled carbon nanotube (MWCNT) catalysis. CM obtained from biomass via hydrothermal carbonization (CM-03) and its ash form (CM-03K) were doped within poly(ɛ-caprolactone) (PCL) matrix and 3D printed to form scaffolds with aligned fibers for structural biomimicry. Scaffolds were seeded with C2C12 mouse myoblasts and subjected to electrical stimulation during the in vitro culture. Enhanced myotube formation was observed in electroactive groups compared to their non-conductive counterparts and it was observed that myotube formation and myotube maturity were significantly increased for CM-03 group after electrical stimulation. The results have therefore showed that the CM obtained from macroalgae biomass is a promising novel source for the production of the electrically conductive scaffolds for skeletal muscle tissue engineering.

Facile modification of polycaprolactone nanofibers with egg white protein.

Synthetic polymers remain to be a major choice for scaffold fabrication due to their structural stability and mechanical strength. However, the lack of functional moieties limits their application for cell-based therapies which necessitate modification and functionalization. Blending synthetic polymers with natural components is a simple and effective way to achieve the desired biological properties for a scaffold. Herein, nanofibrous mats made of polycaprolactone (PCL) and egg white protein (EWP) blend were developed and further evaluated for use as a scaffold for tissue engineering applications. Homogeneous distribution of EWP was achieved throughout the nanofibrous mats, as shown by immunohistochemistry. ATR-FTIR analysis and contact angle measurements have further confirmed the presence of EWP on the surface of the samples. The swelling test showed that PCL/EWP nanofibers have higher water uptake than PCL nanofibrous mats. Also, EWP addition on the nanofibrous mats resulted in an increase in the tensile strength and Young's modulus of the mats, indicating that the presence of protein can greatly enhance the mechanical properties of the mats. A significantly higher, more uniform, and dispersed cell spreading was observed on days 7 and 14 than that on neat PCL mats, demonstrating the importance of providing the required cues for cell homing by the availability of EWP. Hence, EWP is shown to be a simple and low-cost source for the functionalization of PCL nanofibrous mats. EWP is, therefore, a facile candidate to enhance cellular interactions of synthetic polymers for a wide range of tissue engineering applications.

3D cellular alignment and biomimetic mechanical stimulation enhance human adipose-derived stem cell myogenesis.

Determination of a stem cell source with sufficient myogenic differentiation capacity that can be easily obtained in large quantities is of great importance in skeletal muscle regeneration therapies. Adipose-derived stem cells (ASCs) are readily available, can be isolated from fat tissue with high yield and possess myogenic differentiation capacity. Consequently, ASCs have high applicability in muscle regenerative therapies. However, a key challenge is their low differentiation efficiency. In this study, we have explored the potential of mimicking the natural microenvironment of the skeletal muscle tissue to enhance ASC myogenesis by inducing 3D cellular alignment and using dynamic biomimetic culture. ASCs were entrapped and 3D aligned in parallel within fibrin-based microfibers and subjected to uniaxial cyclic stretch. 3D cell alignment was shown to be necessary for achieving and maintaining the stiffness of the construct mimicking the natural tissue (12 ± 1 kPa), where acellular aligned fibers and cell-laden random fibers had stiffness values of 4 ± 1 and 5 ± 2 kPa, respectively, at the end of 21 d. The synergistic effect of 3D cell alignment and biomimetic dynamic culture was evaluated on cell proliferation, viability and the expression of muscle-specific markers (immunofluorescent staining for MyoD1, myogenin, desmin and myosin heavy chain). It was shown that the myogenic markers were only expressed on the aligned-dynamic culture samples on day 21 of dynamic culture. These results demonstrate that 3D skeletal muscle grafts can be developed using ASCs by mimicking the structural and physiological muscle microenvironment.

Design of a new dual mesh with an absorbable nanofiber layer as a potential implant for abdominal hernia treatment.

Dual meshes are often preferred in the treatment of umbilical and incisional hernias where the abdominal wall defect is large. These meshes are generally composed of either two nonabsorbable layers or a nonabsorbable layer combined with an absorbable one that degrades within the body upon healing of the defect. The most crucial point in the design of a dual mesh is to produce the respective layers based on the structure and requirements of the recipient site. We herein developed a dual mesh that consists of two layers: a nanofibrous layer made of poly (glycerol sebacate)/poly (caprolactone) (PGS/PCL) to support the healing of the abdominal wall defect and a nondegradable, nonadhesive smooth layer made of polycarbonateurethane (PU) with suitable properties to avoid the adhesion of the viscera to the mesh. To prepare the double-sided structure, PGS/PCL was directly electrospun onto the PU film. This processing approach provided a final product with well-integrated layers as observed by a scanning electron microscope. Tensile test performed at the dry state of the samples showed that the dual mesh has the ability to elongate seven times more as compared with the commercially available counterparts, mimicking the native tissue properties. The degradation test carried out at physiological conditions revealed that PGS started to degrade within the first 15 days. in vitro studies with human umbilical vein endothelial cells demonstrated the double function of the meshes, in which PU layer did not allow cell adhesion, whereas PGS/PCL layer has the ability to support cell adhesion and proliferation. Therefore, the material developed in this study has the potential to be an alternative to the existing hernia mesh products.

A novel polyurethane-based biodegradable elastomer as a promising material for skeletal muscle tissue engineering.

A key challenge in skeletal muscle tissue engineering is the choice of a proper scaffolding material as it should demonstrate elastic behavior to withstand and support the dynamic loading of the tissue microenvironment while being biodegradable and biocompatible. In this study, we tested the applicability of a novel biodegradable polyurethane (PU) elastomer chain extended with fibrinogen (Fib) to fulfill these requirements. Biodegradable polyurethane-fibrinogen (PU-Fib) elastomers were synthesized by step-wise condensation polymerization. Firstly, PU prepolymer was synthesized and then Fib was integrated into PU prepolymer during the second step of polymerization. The chemical, thermal, viscoelastic, mechanical and biodegradation properties of PU-Fib were characterized. FTIR-ATR spectrum showed amide bands specific to PU and Fib, DSC thermograms showed the suitable integration between the components. Dynamic mechanical analysis revealed Tg and Tα* transitions at 64.5 °C and 38.4 °C, respectively. PU and Fib had shown chemically compatible interactions and when compared to PCL, PU-Fib possessed viscoelastic properties more suitable to the native tissue. PU-Fib films were produced and seeded with C2C12 mouse myoblasts. Uniaxial cyclic stretch was applied to the cell seeded films for 21 d to mimic the native dynamic tissue microenvironment. Cell proliferation, viability and the expression of muscle-specific markers (immunofluorescent staining for myogenin and myosin heavy chain) were assessed. Myoblasts proliferated well on PU-Fib films; aligned parallel along their long edge, and express myogenic markers under biomimetic dynamic culture. It was possible to culture myoblasts with high viability on PU-Fib elastomeric films mimicking native muscle microenvironment.

Infrapatellar Fat Pad-Derived Stem Cell-Based Regenerative Strategies in Orthopedic Surgery.

Infrapatellar fat pad is a densely vascularized and innervated extrasynovial tissue that fills the anterior knee compartment. It plays a role in knee biomechanics as well as constitutes a source of stem cells for regeneration after knee injury. Infrapatellar fat pad-derived stem cells (IPFP-ASCs) possess enhanced and age-independent differentiation capacity as compared to other stem cells, which makes them a very promising candidate in stem cell-based regenerative therapy. The aims of this review are to outline the latest advances and potential trends in using IPFP-ASCs and to emphasize the advantages over other sources of stem cells for applications in orthopedic surgery.