ABSTRACT
In this work, a bilayer chitosan/sodium alginate scaffold was prepared via a needleless electrospinning technique. The layer of sodium alginate was electrospun over the layer of chitosan. The introduction of partially deacetylated chitin nanowhiskers (CNW) stabilized the electrospinning and increased the spinnability of the sodium alginate solution. A CNW concentration of 7.5% provided optimal solution viscosity and structurization due to electrostatic interactions and the formation of a polyelectrolyte complex. This allowed electrospinning of defectless alginate nanofibers with an average diameter of 200-300 nm. The overall porosity of the bilayer scaffold was slightly lower than that of a chitosan monolayer, while the average pore size of up to 2 µm was larger for the bilayer scaffold. This high porosity promoted mesenchymal stem cell proliferation. The cells formed spherical colonies on the chitosan nanofibers, but formed flatter colonies and monolayers on alginate nanofibers. The fabricated chitosan/sodium alginate bilayer material was deemed promising for tissue engineering applications.
ABSTRACT
A bilayer nonwoven material for tissue regeneration was prepared from chitosan (CS) and hyaluronic acid (HA) by needleless electrospinning wherein 10-15 wt% (with respect to polysaccharide) polyethylene oxide was added as spinning starter. A fiber morphology study confirmed the material's uniform defect-free structure. The roughness of the bilayer material was in the range of 1.5-3 µm, which is favorable for cell growth. Electrospinning resulted in the higher orientation of the polymer structure compared with that of corresponding films, and this finding may be related to the orientation of the polymer chains during the spinning process. These structural changes increased the intermolecular interactions. Thus, despite a high swelling degree of 1.4-2.8 g/g, the bilayer matrix maintained its shape due to the large quantity of polyelectrolyte contacts between the chains of oppositely charged polymers. The porosity of the bilayer CS-HA nonwoven material was twice lower, while the Young's modulus and break stress were twice higher than that of a CS monolayer scaffold. Therefore, during the electrospinning of the second layer, HA may have penetrated into the pores of the CS layer, thereby increasing the polyelectrolyte contacts between the two polymers. The bilayer CS-HA scaffold exhibited good compatibility with mesenchymal stem cells. This characteristic makes the developed material promising for tissue engineering applications.
ABSTRACT
A series of water-soluble sulfoethylated chitosans (SEC) with degrees of substitution (DS) up to 130% were obtained using a heterogeneous reaction of chitosan with sodium 2-chloroethanesulfonate in 85% isopropanol in the presence of NaOH. NMR and FTIR spectroscopy confirmed that sulfoethylation of chitosan preferentially happens at hydroxyl groups and to some extent at amino groups, giving mixed substituted O,N-SEC. Chitosan shows positive birefringence, whereas SEC shows negative values, indicating self-organization in dilute solution. Dynamic light scattering studies revealed the presence of aggregates in dilute solutions of chitosan and SEC. The sizes of the SEC aggregates are sensitive to the DS and the nature of the solvent. X-ray diffraction of SEC films revealed that the introduction of sulfoethyl groups into chitosan leads to amorphization, which is more pronounced at higher DS. During the storage of SEC films, the samples loose solubility due to the formation of ionic crosslinks upon dehydration.
ABSTRACT
Chitosan scaffolds have gained much attention in various tissue engineering applications, but the effect of their microstructure on cell-material spatial interactions remains unclear. Our objective was to evaluate the effect of chitosan-based matrices doping with chitin nano-whiskers (CNW) on adhesion, spreading, cytoskeleton structure, and proliferation of rat bone marrow stromal cells (BMSCs). The behavior of BMSCs during culture on chitosan-CNW films was determined by the molecular mass, hydrophobicity, porosity, crosslinking degree, protonation degree and molecular structure of the composite chitosan-CNW films. The shape, spreading area, cytoskeleton structure, and proliferation of BMSCs on chitosan matrices with a crystalline structure and high porosity were similar to that observed for BMSCs cultured on polystyrene tissue culture plates. The amorphous polymer structure and high swelling led to a decrease in the spreading area and cell proliferation. Thus, we can control the behavior of cells in culture (adhesion, spreading, and proliferation) by changing the physico-chemical properties of the chitosan-CNW films.
