All-aqueous microfluidic emulsions for templated fabrication of biomaterials

Abstract

In the first chapter of this dissertation, we introduce the all-aqueous emulsions as a suitable template for fabricating biomaterials. Such emulsions take advantages of the phase separation between the incompatible solutes dissolved in water. Compared to the conventional water/oil emulsions, the all-aqueous emulsion is superior in processing of biomolecules. We also present the manipulation on the structure of all-aqueous emulsions, such as droplets and interfaces, by applying the microfluidic technology. Moreover, different strategies have been adopted to facilitate the fabrication; however, intensive external inputs are always involved and may deteriorate the active ingredients encapsulated. Therefore, new strategies should be applied to enhance the biocompatibility of the all-aqueous emulsions-templated fabrication. In the second chapter, we illustrate the overall research hypothesis that the principles of osmotic dehydration and affinity partitioning in all-aqueous emulsions have the potential of facilitating the fabrication of biomaterials in a biocompatible manner. To get controllable all-aqueous emulsion templates for the subsequent fabrication, electrical field is used to facilitate the manipulation of all-aqueous emulsions in microfluidic devices in Chapter 3. Then in Chapter 4, we choose all-aqueous emulsion droplets as the templates and present an osmo-solidification process that can solidify droplets to particles by applying the principle of osmotic dehydration. The process exhibits good compatibility with proteins and the fabricated particles represent promising vehicles for delivery of bioactive proteins. In Chapter 5, 6 and 7, all-aqueous emulsion interfaces are used as the templates. Affinity partitioning of hydrophilic solutes in all-aqueous emulsions is introduced to direct the assembly of oppositely charged polyelectrolytes at the interfaces to fabricate polyelectrolyte microcapsules in Chapter 5. The fabricated microcapsules show remarkable stimuli-responsiveness and cytocompatibility. Moreover, we also change the partitioning of polyelectrolytes in all-aqueous emulsions to optimize and even vary the fabricated structures in Chapter 6. Besides synthetic macromolecules, the partitioning of oppositely charged proteins is also applied to facilitate the fabrication of protein-based biomimetic microparticles. We demonstrate that the resultant particles can mimic key characters of natural red blood cells, such as remarkable softness, flexibility and high oxygen carrying capacity. In summary, all-aqueous microfluidic emulsions have been developed for the fabrication of different biomaterials in this dissertation. Novel strategies are proposed to facilitate the fabrication. The biocompatibility of the fabricated biomaterials can be dramatically improved and their potentials to be applied in various biomedical applications can be drastically expanded.