Rheology, microstructure and diffusion in soft gelatin nanocomposites packed with anionic nanogels

The colloidal stability of therapeutic nanoparticles for improving human health is a significant challenge, owing to aggregation and sedimentation. To overcome such limitations, gelatin-based nanocomposites are designed with increasing concentration of anionic nanogels. Complementa r y steady-state and oscillator y rheolog y revealed that the pre-yielding viscosity of nanocomposites scales with nanogel packing density, eta(similar to)(0)similar to phi(0.5)(c) . Upon shearing, nanocomposites transform into a shear gel , which exhibits a power law shear-thinning behaviour. Nanogel loading also increases the G', increases the sol-gel transition temperatures and decreases the charac-teristic mesh size of the nanocomposites. We postulate that electrostatic and hydrogen-bonding interactions between nanogels and gelatin play a synergistic role in the observed structural, micromechanical and rheological behaviour. Fluorescent nanogel-labelling combined with centrifugation, revealed that ca. 60 % of nanogels precipitate together with gelatin, indicating the extent of nanogel-gelatin interactions. These interactions are probed using molecular modelling, temperature dependence of G' and time-temperature superimposition prin-ciple combined with the Arrhenius model. The remaining nanogels (ca. 40 %) demonstrate diffusive mobilit y (5.51 x 10(-10) m(2) s(-1)) and are located in the bu l k solvent existin g in the pores and channels of the nano-composites. Taking advantage of nanogels' diffusive mobility, bioresponsive release under conditions of swal-lowing is simulated via computational fluid dynamics.