In this study, alginate polymers are used to get
homogeneous cylindrical or spherical gels. MRI techniques
are employed to study homogeneity of these gels. Four different
alginates are used and, for each one, five different concentrations
for mechanical tests and three different concentrations
for release tests are studied. Mechanical tests are
performed to get gels’ linear viscoelasticity region and then
to evaluate their crosslink density in relation to polymer concentration.
Afterwards, three model molecules (theophylline,
vitamin B12, and myoglobin) are loaded within gels to study
the release kinetics in water from both cylindrical and spherical
gels. Diffusion coefficients calculated from these experiments
are then used to estimate the polymeric network mesh
wideness. This work shows how crosslink density increases
with polymer concentration regardless of the alginate type
considered. In addition, while vitamin B12 diffusion coefficient
is inversely proportional to crosslink density, myoglobin
is too large to diffuse through the polymeric network,
whatever the alginate type and polymer concentration. At
the same time, theophylline is too small to be sensibly
affected by increasing the polymeric network crosslink density.
Finally, MRI analysis and vitamin B12 diffusion coefficient
values prove that, structurally speaking, cylinders and
spheres are similar and homogeneous. 2008 Wiley Periodicals,
Inc. J Biomed Mater Res 87A: 808–818, 2008
