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Molecules 2009, 14(8), 3003-3017; doi:10.3390/molecules14083003

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

1,* , 2
1 Dipartimento di Ingegneria Chimica, dell'Ambiente e delle Materie prime, Università di Trieste, P.le Europa 1, 34127 Trieste, Italy 2 Dipartimento di Chimica e Tecnologie del Farmaco, Università di Roma “La Sapienza”, P.le Aldo Moro 5, 00185 Roma, Italy 3 PROTOS Research Institute, Via Flavia 23/1, 34100 Trieste, Italy 4 Dipartimento di Scienze della vita, Università di Trieste, Via L. Giorgieri 1, I-34127 Trieste, Italy
* Author to whom correspondence should be addressed.
Received: 25 June 2009 / Revised: 4 August 2009 / Accepted: 10 August 2009 / Published: 12 August 2009
(This article belongs to the Special Issue Macromolecules Applied to Pharmaceutics)
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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.
Keywords: calcium alginates; mechanical tests; diffusive tests; mesh size; equivalent network theory calcium alginates; mechanical tests; diffusive tests; mesh size; equivalent network theory
This is an open access article distributed under the Creative Commons Attribution License (CC BY) which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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Grassi, M.; Sandolo, C.; Perin, D.; Coviello, T.; Lapasin, R.; Grassi, G. Structural Characterization of Calcium Alginate Matrices by Means of Mechanical and Release Tests. Molecules 2009, 14, 3003-3017.

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