Speaker
Description
Nature offers amazing examples of nanostructured molecules and materials. I will focus on phytoglycogen, a highly branched polymer of glucose produced in the form of dense, monodisperse nanoparticles by some varieties of plants such as sweet corn. The particles are chemically simple, but have a special dendrimeric or tree-like structure that produces interesting and unusual properties such as extraordinary water retention, and low viscosity and exceptional stability in water. These properties point to a wide variety of potential applications from cosmetics to drug delivery, yet these applications need to be enabled by a deeper understanding of the unique structure of the particles and their interaction with water. To achieve this, we have used a wide range of techniques. Neutron scattering has revealed that the nanoparticles have uniform size and density and are highly hydrated, with each nanoparticle containing about 250% of its mass in water. Surface-sensitive infrared absorption measurements on phytoglycogen films show that the high degree of branching in phytoglycogen leads to a well ordered “network” structure of the hydration water within the particles. Rheology measurements have revealed weak interactions between the particles, allowing loading of the particles into water up to 20% w/w before significant increases in viscosity are observed, showing that this is an interesting model system for studying soft colloid physics. This work has also benefitted from molecular dynamics simulations by the group of Hendrick de Haan. Taken together, these studies provide new insights that are key to fully understanding and exploiting these materials in new technologies and therapies.
