(550b) Investigation of Novel Core-Shell Microparticles with Degradable Shells for Controlled-Delivery Applications

The use of advanced multi-functional microparticles is immensely important for applications (e.g., biological, dental, energetic, sensor) that require adjustable, predictable, and controlled release of functionalized packages. The unique core-shell structure of a microcapsule rather than a homogeneous microsphere offers protection of high-value cargoes from the surrounding environment until the core is later released in a controlled manner. The thickness, morphology, and composition of the outer-shell of the microcapsule can be adjusted for controlled-release of the inner-core material under conditions that are specific to the targeted application of the microcapsule. An unlimited variety of substances can be employed as the core and shell materials of the microcapsule; however, delivery of a functional core that is induced by simultaneous chemical degradation and mass loss of the outer-shell material provides precise release mechanisms that are suitable for advanced applications that require precise delivery. Crosslinkable polymeric systems that are based on anhydrides are promising candidates for shell materials with their surface-eroding mechanism and their ability to selectively and efficiently polymerize the material at high resolutions. In this work, a synthesis protocol was developed to produce unique, bio-compatible, surface-eroding anhydride-based oligomers that later react to form crosslinked networks upon exposure to UV light. A double flow-focusing PDMS microfluidic device will be utilized for continuous droplet formation to most precisely control the size, composition, and uniformity of the multi-phase (liquid/liquid/liquid) emulsions before photo-polymerization of the degradable polymeric outer shell (liquid/solid/liquid). By controlling the channel geometries, the viscous and interfacial properties of the working fluids, the overall flow rate, and the flow rate ratios of the phases that are involved, the diameter of liquid cores, the thickness of shells, and the overall size of the particles can be controlled. These parameters, along with the chemical composition of the outer shell material, will affect the release profile of the inner liquid core, which determines the applicability of the resulting microcapsules to advanced delivery applications. In-depth analysis of the degradation rates and erosion mechanisms with a novel and adaptable flow apparatus can be coupled with previously explored methods of analysis to provide insight into the complex mechanisms that take place during erosion of the microcapsule shell. Given the high flexibility of material selection for the anhydride-based degradable shells that are provided by the novel synthesis technique, microcapsules with shells of different resin formulations can demonstrate nearly identical release kinetics by select differences in shell thickness.