Mesh size distribution determination of interpenetrating polymer network hydrogels

The importance of Interpenetrating Polymer Networks ( IPNs) in biomedical and pharmaceutical fields is continuously growing because of their mechanical and drug carrier tailoring opportunities. This paper deals with the physico-chemical characterization of an IPN hydrogel based on calcium-alginate and a dextran methacrylate derivative. The attention is focused on the determination of IPN mesh size distribution. For this purpose, two different approaches were applied, namely using a combination of rheological and low field NMR characterization, and cryoporosimetry. Appropriate mathematical models were developed for the interpretation of the experimental data. Both approaches led to a mono-modal mesh size distribution spanning the same size range but characterized by different mean values (25 nm, Rheo-NMR; 44 nm, cryoporosimetry). This is probably due to mesh widening upon water freezing. Moreover, release experiments of a model protein - myoglobin - from the IPN were performed and the obtained data were combined with the results of the two above mentioned approaches. Release tests yielded an estimation of the mean mesh size that is closer to that obtained according to the rheology-NMR approach than that resulting from cryoporosimetry measurements.