Sodium alginate, as the most common alginate salt derivative, is soluble in water and once
dissolved, forms viscous solutions. The properties of the solution depend on the concentration
and molecular weight of the biopolymer. Sodium alginate, as a form of flavorless gum, is often
used in the food industry to increase viscosity. Sodium alginate can be crosslinked in aqueous
solution with the presence of calcium ions. The solution-gel transition is caused by calcium ions
exchanging with sodium ions, and binding the guluronic residues together to form crosslinks in
the material. These crosslinks have an “egg-box” structure [142], as previously shown in Figure
1-4, and show viscoelastic solid behavior. Because of its biocompatibility and low toxicity, and
spontaneous gelation, alginate gel crosslinked with calcium ions (Ca2+) has been widely applied
for variety of tissue engineering studies. Previous studies show that the mechanical properties of
alginate hydrogel have an influence on both the structure of the fabricated scaffold and the
proliferation and metabolism of encapsulated cells [86]. Unfortunately, these studies were all
focusing on shear modulus, which is a quantity for describing the stiffness of the material and its
response to a shear strain, and little was reported regarding the compressive properties of
alginate hydrogel, which is of importance in order to form 3D structure in the fabrication of
hydrogel scaffolds, as concerned in the present study. This chapter presents a study on
compressive properties of alginate hydrogel, with emphasis on identifying the influence of the
fabrication process parameters.