Biomimetic all-aqueous droplets for biomedical applications

Abstract

Traditionally, aqueous two-phase systems have only found applications in extraction of molecules and in green chemical synthesis. Its potential and value as a system for studying novel interfacial phenomena and for novel nanobiomedicine have been largely overlooked. The ultralow interfacial tension of the system has called for new ways to induce formation of uniformly sized droplets in microfluidic devices. The passivity of the interface allows visualization and recording of sound and music on a liquid-liquid interface for the first time. The diffuse interfaces of these aqueous interfaces create new opportunities to assembly particles and macromolecules, such as enzymes, for form new structures with enhanced bio- & cyto-compatibility. In particular, the all-aqueous system allows phase separation between liquid phases rich in proteins, polysaccharides and salts simply by adjusting their concentrations without changing the temperature. This not only allows a phase-separation-based strategy to modify the structures of droplets, possibly mimicking biological droplets, but it also provides an excellent model system for studying the intricate relationships between interfacial phenomena and degree of phase separation. Such aqueous phase separation has been shown to influence cytoplasmic dynamics in biological cells discovered by other researchers. As an example, we have incorporated proteins into our all-aqueous droplets to form a new type of vesicles, which we coined “fibrillosomes”. By manipulating the proteins and the network that it forms, we also demonstrate the overcoming of the thermodynamically favored coalescence dynamics, and induce division of emulsion droplets. This inspires a new way to achieve biomimetic behaviors in droplet-based materials that have potential for a new class of programmable carriers for nanomedicine. In this talk, I will introduce the design and generation of all-aqueous droplets, demonstrate their unique characteristics and discuss the potential of all-aqueous droplets for bio-encapsulation.