Hybrid scaffolds of Mg alloy mesh reinforced polymer/extracellular matrix composite for critical‐sized calvarial defect reconstruction

The challenge of developing scaffolds to reconstruct critical‐sized calvarial defects without the addition of high levels of exogenous growth factor remains relevant. Both osteogenic regenerative efficacy and suitable mechanical properties for the temporary scaffold system are of importance. In this study, a Mg alloy mesh reinforced polymer/demineralized bone matrix (DBM) hybrid scaffold was designed where the hybrid scaffold was fabricated by a concurrent electrospinning/electrospraying of poly(lactic‐co‐glycolic acid) (PLGA) polymer and DBM suspended in hyaluronic acid (HA). The Mg alloy mesh significantly increased the flexural strength and modulus of PLGA/DBM hybrid scaffold. In vitro results demonstrated that the Mg alloy mesh reinforced PLGA/DBM hybrid scaffold (Mg‐PLGA@HA&DBM) exhibited a stronger ability to promote the proliferation of bone marrow stem cells (BMSCs) and induce BMSC osteogenic differentiation compared with control scaffolding materials lacking critical components. In vivo osteogenesis studies were performed in a rat critical‐sized calvarial defect model and incorporated a variety of histological stains and immunohistochemical staining of osteocalcin. At 12 weeks, the rat model data showed that the degree of bone repair for the Mg‐PLGA@HA&DBM scaffold was significantly greater than for those scaffolds lacking one or more of the principal components. Although complete defect filling was not achieved, the improved mechanical properties, promotion of BMSC proliferation and induction of BMSC osteogenic differentiation, and improved promotion of bone repair in the rat critical‐sized calvarial defect model make Mg alloy mesh reinforced PLGA/DBM hybrid scaffold an attractive option for the repair of critical‐sized bone defects where the addition of exogenous isolated growth factors is not employed.     

A humanised tissue‐engineered bone model allows species‐specific breast cancer‐related bone metastasis in vivo

Bone metastases frequently occur in the advanced stages of breast cancer. At this stage, the disease is deemed incurable. To date, the mechanisms of breast cancer‐related metastasis to bone are poorly understood. This may be attributed to the lack of appropriate animal models to investigate the complex cancer cell–bone interactions. In this study, two established tissue‐engineered bone constructs (TEBCs) were applied to a breast cancer‐related metastasis model. A cylindrical medical‐grade polycaprolactone‐tricalcium phosphate scaffold produced by fused deposition modelling (scaffold 1) was compared with a tubular calcium phosphate‐coated polycaprolactone scaffold fabricated by solution electrospinning (scaffold 2) for their potential to generate ectopic humanised bone in NOD/SCID mice. While scaffold 1 was found not suitable to generate a sufficient amount of ectopic bone tissue due to poor ectopic integration, scaffold 2 showed excellent integration into the host tissue, leading to bone formation. To mimic breast cancer cell colonisation to the bone, MDA‐MB‐231, SUM1315, and MDA‐MB‐231BO breast cancer cells were cultured in polyethylene glycol‐based hydrogels and implanted adjacent to the TEBCs. Histological analysis indicated that the breast cancer cells induced an osteoclastic reaction in the TEBCs, demonstrating analogies to breast cancer‐related bone metastasis seen in patients.     

Bioactive nano‐fibrous scaffold for vascularized craniofacial bone regeneration

There has been a growing demand for bone grafts for correction of bone defects in complicated fractures or tumours in the craniofacial region. Soft flexible membrane like material that could be inserted into defect by less invasive approaches; promote osteoconductivity and act as a barrier to soft tissue in growth while promoting bone formation is an attractive option for this region. Electrospinning has recently emerged as one of the most promising techniques for fabrication of extracellular matrix such as nano‐fibrous scaffolds that can serve as a template for bone formation. To overcome the limitation of cell penetration of electrospun scaffolds and improve on its osteoconductive nature, in this study, we fabricated a novel electrospun composite scaffold of polyvinyl alcohol (PVA)‐poly (ε) caprolactone (PCL)‐Hydroxyapatite based bioceramic (HAB), namely, PVA‐PCL‐HAB. The scaffold prepared by dual electrospinning of PVA and PCL with HAB overcomes reduced cell attachment associated with hydrophobic PCL by combination with a hydrophilic PVA and the HAB can contribute to enhance osteoconductivity. We characterized the physicochemical and biocompatibility properties of the new scaffold material. Our results indicate PVA‐PCL‐HAB scaffolds support attachment and growth of stromal stem cells; [human bone marrow skeletal (mesenchymal) stem cells and dental pulp stem cells]. In addition, the scaffold supported in vitro osteogenic differentiation and in vivo vascularized bone formation. Thus, PVA‐PCL‐HAB scaffold is a suitable potential material for therapeutic bone regeneration in dentistry and orthopaedics.     

Genipin-Cross-linked Electrospun Collagen Fibers

The fabrication of a fibrous collagen scaffold using electrospinning is desirable for tissue-engineering applications. Previously, electrospun collagen fibers were shown to be unstable in aqueous environments and, therefore, cross-linking is essential to stabilize these fibers. In this study genipin, a significantly less cytotoxic cross-linking agent compared to glutaraldehyde, was used to cross-link electrospun collagen fibers. The significance of this research lies in the use of four alcohol/water solvent systems to carry out the crosslinking reaction to maintain fibrous morphology during cross-linking. The four cross-linking conditions established were: (1) ethanol, 5% water and 3 days, (2) ethanol, 3% water and 5 days, (3) ethanol, 5% water and 5 days, and (4) isopropanol, 5% water and 5 days at a genipin concentration of 0.03 M. Results illustrated that genipin-cross-linking was effective in maintaining collagen fiber integrity in aqueous and cell culture media environments for up to 7 days. In addition, it was shown that fiber swelling could be controlled by using different cross-linking conditions. Swelling of cross-linked fibers immersed in Dulbecco's modified eagle medium for 7 days ranged from 0 to 59 ± 4%. The cross-linked fibers were analyzed using scanning electron microscopy, Fourier transform infrared spectroscopy and ninhydrin assay. Finally, studies using primary human fibroblasts indicated good cell adhesion to these scaffolds. Overall, our data suggest that these stabilized fibrous collagen scaffolds provide a promising environment for tissue-regeneration applications.     

Tri-layered chitosan scaffold as a potential skin substitute

A tri-layered chitosan-based scaffold was successfully made to replicate the striation of a full-thickness skin more accurately than a single- or bi-layered scaffold, which needed weeks of co-culturing of fibroblasts and keratinocytes to achieve similar striation. Chitosan solution was freeze-dried and made into porous disks. Chitosan or chitosan–pectin in acetic acid solution was electrospun onto the chitosan disk to form a nanofibrous layer and a thin film. Examinations based on scanning electron spectroscopy showed that the scaffold was composed of a porous layer (2 mm) to simulate the dermis, a thin film (25–45 μm) to mimic the basement membrane, and a layer of nanofibers (100–200 μm) to serve as the protective epidermis. The tensile strength and modulus of the composite scaffold were significantly higher than those of the chitosan disk (p < 0.01). The composite was able to quickly absorb water and stayed intact throughout the course of the 14-day cell culture tests. The fibroblast cells seeded on both sides of the scaffolds were able to proliferate and stayed separated by the thin film.     

In vitro evaluation of random and aligned polycaprolactone/gelatin fibers via electrospinning for bone tissue engineering

Scaffold, as an essential element of tissue engineering, should provide proper chemical and structural cues to direct tissue regeneration. In this study, aligned and random polycaprolactone (PCL)/gelatin fibrous scaffolds with different mass ratio were electrospun. Chemical, structural, and mechanical properties of PCL/gelatin fibrous scaffolds were characterized by FTIR and tensile measurements. The average diameters of different groups were between 334.96?±?41.43?nm and 363.78?±?50.49?nm. Blending PCL with gelatin increased the mechanical properties of the scaffolds. The cell culture results demonstrated that the mass ratio of PCL and gelatin showed no obvious effects on cell behavior, whereas the cell growth behavior was affected by the fibers orientation. Higher elongation ratio, enhanced cell proliferation and elevated alkaline phosphatase activity were observed for cells cultured on aligned fibers. The findings in our research provide insightful information for the design and fabrication of scaffolds for bone tissue engineering.     

Pectin-chitosan-PVA nanofibrous scaffold made by electrospinning and its potential use as a skin tissue scaffold

Scaffolds made of chitosan nanofibers are often too mechanically weak for their application and often their manufacturing processes involve the use of harmful and flammable organic solvents. In the attempt to improve the mechanical properties of nanofibrous scaffolds made of chitosan without the use of harmful chemicals, pectin, an anionic polymer was blended with chitosan, a cationic polymer, to form a polyelectrolyte complex and electrospun into nanofibers for the first time. The electrospun chitosan-pectin scaffolds, when compared to electrospun chitosan scaffolds, had a 58% larger diameter, a 21% higher Young’s modulus, a 162% larger strain at break, and a 104% higher ultimate tensile strength. Compared to the chitosan scaffolds, the chitosan-pectin scaffolds’ swelling ratios decreased by 55% after 60?min in a saline solution and more quickly released the preloaded tetracycline HCl. The L929 fibroblast cells proliferated slightly slower on the chitosan-pectin scaffolds than on the chitosan scaffolds. Nonetheless, cells on both materials deposited similar levels of extracellular type I collagen on a per DNA basis. In conclusion, a novel chitosan-pectin nanofibrous scaffold with superior mechanical properties than a chitosan nanofibrous scaffold was successfully made without the use of harmful solvents.     

Functional recovery guided by an electrospun silk fibroin conduit after sciatic nerve injury in rats

The aim of this study was to evaluate the regenerative capacity of a newly developed nerve guidance conduit using electrospun silk fibroin (SFNC) implanted in a 10‐mm defect of the sciatic nerve in rats. After evaluating the physical properties and cytocompatibility of SFNC in vitro, rats were randomly allocated into three groups: defect only, autograft and SFNC. To compare motor function and abnormal sensation among groups, ankle stance angle (ASA) and severity of autotomy were observed for 10 weeks after injury. Immunostaining with axonal neurofilament (NF) and myelin basic protein (MBP) antibodies were performed to investigate regenerated nerve fibres inside SFNC. ASA increased significantly in the SFNC group at 1, 7 and 10 weeks after injury compared to the defect only group (p < 0.05). At one week, mean ASA of the SFNC group was significantly higher than that of the autograft group (p < 0.05). Onset and severity of autotomy decreased significantly in the SFNC group compared to other groups (p < 0.05). Autotomy in the SFNC group started at 4 weeks and maximally reached toe level. However, the defect only and autograft groups first showed autotomy at 2 and 1 weeks following injury, respectively, and then reached the sole level. Well myelinated nerve fibres stained with NF and MBP were found inside SFNC. In conclusion, SFNC could be helpful in restoring motor function and preventing abnormal sensations after nerve injury. Copyright © 2012 John Wiley & Sons, Ltd.     

Bacterial Biofilm Formation Using PCL/Curcumin Electrospun Fibers and Its Potential Use for Biotechnological Applications

Electrospun nanofibers are used for many applications due to their large surface area, mechanical properties, and bioactivity. Bacterial biofilms are the cause of numerous problems in biomedical devices and in the food industry. On the other hand, these bacterial biofilms can produce interesting metabolites. Hence, the objective of this study is to evaluate the efficiency of poly (Ɛ- caprolactone)/Curcumin (PCL/CUR) nanofibers to promote bacterial biofilm formation. These scaffolds were characterized by scanning electron microscopy (SEM), which showed homogeneous fibers with diameters between 441–557 nm; thermogravimetric analysis and differential scanning calorimetry (TGA and DSC) demonstrated high temperature resilience with degradation temperatures over >350 °C; FTIR and ¹H-NMR serve as evidence of CUR incorporation in the PCL fibers. PCL/CUR scaffolds successfully promoted the formation of Escherichia coli, Staphylococcus aureus and Pseudomonas aeruginosa biofilms. These results will be valuable in the study of controlled harvesting of pathogenic biofilms as well as in metabolites production for biotechnological purposes.