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Keywords:

  • chitosan;
  • alginate;
  • chondroitin;
  • compression-tensile tester;
  • freeze-dry;
  • correlation length;
  • fractal dimensions;
  • scanning electron microscopy (SEM);
  • small-angle neutron scattering (SANS)

Abstract

Networks made from chitosan and alginate have been utilized as prospective tissue engineering scaffolds due to material biocompatibility and degradability. Calcium (Ca2+) is often added to these networks as a modifier for mechanical strength enhancement. In this work, we examined changes in the bulk material properties of different concentrations of chitosan/alginate mixtures (2, 3, or 5% w/w) upon adding another modifier, chondroitin. We further examined how material properties depend on the order the modifiers, Ca2+ and chondroitin, were added. It was found that the addition of chondroitin significantly increased the mechanical strength of chitosan/alginate networks. Highest elastic moduli were obtained from samples made with mass fractions of 5% chitosan and alginate, modified by chondroitin first and then Ca2+. The elastic moduli in dry and hydrated states were (4.41 ± 0.52) MPa and (0.11 ± 0.01) MPa, respectively. Network porosity and density were slightly dependent on total polysaccharide concentration. Average pore size was slightly larger in samples modified by Ca2+ first and then chondroitin and in samples made with 3% starting mass fractions. Here, small-angle neutron scattering (SANS) was utilized to examine mesh size of the fibrous networks, mass-fractal parameters and average dimensions of the fiber cross-sections prior to freeze-drying. These studies revealed that addition of Ca2+ and chondroitin modifiers increased fiber compactness and thickness, respectively. Together these findings are consistent with improved network mechanical properties of the freeze-dried materials. © 2011 Wiley Periodicals, Inc. Biopolymers 95: 840–851, 2011.