Structural Characterization of Calcium Alginate Matrices by Means of Mechanical and Release Tests

Abstract

In this paper we have concentrated on the characterization of calcium alginate hydrogels loaded with a model drug (myoglobin) by means of a mechanical approach; in addition, release tests of myoglobin from alginate hydrogels were performed. At a fixed temperature, relaxation tests (mechanical study) were carried out on matrices constituted by different polymer concentrations. The interpretation of the relaxation behavior of the different matrices was conducted using the generalized Maxwell model; as a result of this investigation it was possible to conclude that for polymer concentrations greater than 0.5 g/ 100 mL the matrices behaved as solid materials. In addition, it was observed that the mechanical properties of the matrices increased with polymer concentration. With regard to the release tests, the diffusion coefficient of myoglobin in the matrix in relation to polymer concentrations was determined. The mechanical and release data where then analyzed by Flory’s theory and by a modified free-volume theory, respectively, to estimate the network mesh size ξ. The comparison between the mesh sizes obtained by the two approaches showed a satisfactory agreement for polymer concentrations greater than 0.5 g/100 mL. It should be noted that the approach proposed here to determine the polymeric network meshes is absolutely general and can be advantageously applied to the characterization of other similar polymeric systems.

Mass Production of Cell‐Laden Calcium Alginate Particles with Centrifugal Force

“…This argument indicates that the decreased production speed was caused by the reduced volume of the Na‐alginate solution during the centrifugal process and the resulting low height of the solution in the tank, and not by increased viscosity of Na‐alginate solution resulting from unexpected alginate gelation in the capillary; therefore, changes of the tank dimensions could facilitate the production of Ca‐alginate particles using an entirely Na‐alginate solution loaded in the tank. Furthermore, to confirm that alginate chains were cross‐linked with calcium ions under the same condition during the mass production process of Ca‐alginate particles, we calculated changes of calcium ion concentration in CaCl 2 solution using the cross‐link density of Ca‐alginate gel shown in a previous paper . As a result, we estimated that the calcium ion concentration slightly decreased by only 2% (calcium ion concentration was changed from 150 to 147 × 10 −3 m ) (Sup.…”

Microfluidic generation of alginate microgels for the controlled delivery of lentivectors

“…Diffusion of lentivectors through an alginate meshwork will be severely diminished due to the relative size of lentivectors (B100 nm) 65 and alginate mesh size (B10 nm). [66][67][68] Nevertheless, we have observed release of lentivectors from both macroscopic alginate hydrogels 14 and microgels. For microgels it is possible that increased surface area contributes to the amount of lentivectors released.…”

Recent Advances in Hydrogels for Biomedical Applications

“…The mechanical properties which are desired in a hydrogel can be achieved by altering the degree of cross-linking. The estimation of cross-linking density of hydrogels was made possible on the basis of Young modulus and Flory's theory [31]; consequently, the generalized Maxwell model helped to control hydrogel linear viscoelastic range along with the relaxation spectra [29].…”