NSTI Nanotech 2009

Effect of Silica Nanoparticles on Rheological Properties and Gelation Temperature of Biodegradable Polymer Gels

V. Florián-Algarín, A. Acevedo
University of Puerto Rico, Mayaguez, PR

Keywords: gelation, biopolymer, rheology, silica nanoparticles


The discovery of new potent and insoluble drugs has emphasized the need for personalized dosages and novel drug-delivery systems. The use of biodegradable polymers is a good alternative to form films in which a solid active pharmaceutical ingredient is suspended. In the processing of films, the rheology and gelation of biodegradable polymers are of particular interest. This work presents the rheological study and gelation kinetics of solid nanoparticle dispersions in aqueous sodium alginate (NaAlg) and gelatin solutions. NaAlg and gelatin are biodegradable polymers that had been used in the food and pharmaceutical industry in several applications such as a thickener, immobilization agent, to produce films and coating, amongst others. Silica nanoparticles with a hydrodynamic diameter of 30 nm where used as surrogate particles in this study. Silica dispersion of up to 5.0 wt% in the specified biopolymers where prepared from a commercial LUDOX silica dispersion. Rheological characterization was performed on a Reologica Stress Tech HR stress controlled rheometer. The thermotropic gelation (Tgel) was experimentally determined independently by the constant-stress temperature ramp method at constant cooling rates and stress, dynamic viscoelastic moduli and thixotropy tests. While the steady-state rheological behavior of solutions above the Tgel was determined at constant temperatures as a function of shear rate.
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