(732d) Optimizing the Coating of Hydrogel Microparticles with Nanoparticles

Microparticles coated with oppositely charged nanoparticles are very versatile compared to their
uncoated counterparts. Nanoparticle coating is useful for improving microparticle stability and
flowability. These coated particles can also be used for pH dependent tunable release, among
other applications. In this work, we examine how a system of oppositely charged hydrogel
microparticles and nanoparticles interact in dilute and concentrated environments. We aim to
optimize the overall yield of coated microparticles at higher concentrations without uncontrolled
aggregation.
The experimental system that we used to model this interaction consists of cationic red
fluorescently-tagged chitosan nanoparticles and anionic green fluorescently-tagged alginate
microparticles in water. The interactions are characterized using fluorescence spectroscopy
along with optical microscopy to quantify the level of coating. A phase diagram is developed
regarding particle behavior at various ratios of nanoparticle to microparticle surface area.
Multiple overall particle concentrations are also tested to determine differences between
dilute and concentrated regimes in the phase diagram. Known shear fields are used as well to
manipulate the phase space at higher overall particle concentrations.