ABSTRACT
Porous scaffolds based on alginate-polymethacrylate hybrid hydrogels intended for bone and cartilage regeneration were prepared through controlled calcium ions diffusion from an agar mould. The double interconnected network of such materials combines into a single porous structure maintained by both noncovalent crosslinks (calcium ions for alginate) and covalent crosslinks (polymethacrylate crosslinked by the addition of mixtures of mono and bifunctional monomers). The alginate component ensures the appropriate micro-environment to mimic the extra-cellular matrix, whereas the polymethacrylate improves the mechanical performances of the hybrid hydrogels, helping to overcome the mechanical limitations of the alginate component. Morphological characterization and porosity analysis of the hybrid scaffolds were assessed by scanning electron microscopy and micro-computed tomography. Relative concentration and distribution of calcium ions were evaluated by atomic absorption and dispersive X-ray analysis, respectively. Uniaxial compressive mechanical tests were conducted to evaluate the compressive elastic modulus of the hybrid hydrogels that was correlated with their swelling ratio and crosslinking degree. As was envisaged a much higher modulus (about seven times) was obtained for the hybrid Alg/HE hydrogel than with alginate alone.
Subject(s)
Alginates/chemistry , Bone Regeneration , Hydrogels/chemical synthesis , Methacrylates/chemistry , Tissue Scaffolds/chemistry , Compressive Strength , Elasticity , PorosityABSTRACT
Fibrous membrane with a fibre diameter of 229 +/- 35 nm was fabricated from polyimide solution by electrospinning. Nanofibrous membrane with a fibre diameter of 251 +/- 37 nm was fabricated by combined electrospinning and electrospraying for polyimide/TiO2. Among the different solvents studied, ethanol was the effective solvent for dispersing the TiO2 nanoparticles in the nanofibrous matrix during electrospraying. The average pore size of polyimide membrane was obtained in the range 0.79-0.89 microm whereas the average pore size of polyimide/TiO2 membrane was found to be in the range 1.23 microm. The tensile stress of polyimide nanofibrous membrane and also polyimide/TiO2 composite fibrous membrane determined to be 0.36 MPa and 0.65 MPa respectively. Nanofibrous membrane containing TiO2 nanoparticles on the surface of the polyimide nanofibres improved the mechanical stability of the membrane.
ABSTRACT
Currently, the application of nanotechnology in bone tissue regeneration is a challenge for the fabrication of novel bioartificial bone grafts. These nanostructures are capable of mimicking natural extracellular matrix with effective mineralization for successful regeneration of damaged tissues. The simultaneous electrospraying of nanohydroxyapatite (HA) on electrospun polymeric nanofibrous scaffolds might be more promising for bone tissue regeneration. In the current study, nanofibrous scaffolds of gelatin (Gel), Gel/HA (4:1 blend), Gel/HA (2:1 blend) and Gel/HA (electrospin-electrospray) were fabricated for this purpose. The morphology, chemical and mechanical stability of nanofibres were evaluated by means of field emission scanning electron microscopy (FESEM), Fourier transform infrared spectroscopy and with a universal tensile machine, respectively. The in vitro biocompatibility of different nanofibrous scaffolds was determined by culturing human foetal osteoblasts and investigating the proliferation, alkaline phosphatase (ALP) activity and mineralization of cells. The results of cell proliferation, ALP activity and FESEM studies revealed that the combination of electrospinning of gelatin and electrospraying of HA yielded biocomposite nanofibrous scaffolds with enhanced performances in terms of better cell proliferation, increased ALP activity and enhanced mineralization, making them potential substrates for bone tissue regeneration.
Subject(s)
Bone Regeneration/physiology , Coated Materials, Biocompatible/chemistry , Electrochemical Techniques/methods , Nanofibers/chemistry , Tissue Scaffolds/chemistry , Animals , Bone and Bones/cytology , Bone and Bones/metabolism , Calcification, Physiologic , Cell Adhesion , Cell Proliferation , Cells, Cultured , Durapatite/chemistry , Electrochemical Techniques/instrumentation , Fetus/cytology , Gelatin/chemistry , Humans , Materials Testing , Osteoblasts/cytology , Osteoblasts/physiologyABSTRACT
The microstructures of N-methylmorpholine-N-oxide (NMMO) regenerated silk fibers have been characterized by atomic force microscopy from the micrometer to the nanometer scale and compared with those previously found from natural silks. Regenerated fibers show poor tensile properties and a brittle behavior, but their mechanical properties improve if subjected to post-spinning drawing. Consequently, it was hypothesized that post-spinning drawing would lead to a microstructure more similar to that of the natural material. Here we show that the microstructure of the samples not subjected to post-spinning drawing is composed of nanoglobules that differ from those found in natural silkworm silk both in size and orientation with respect to the macroscopic axis of the fiber. The microstructure of samples subjected to post-spinning drawing evolves in the sense of decreasing the size but increasing the orientation of the nanoglobules, but these effects are only observed in some regions of the fibers.
