ABSTRACT
Controllable construction and manipulation of artificial multi-compartmental structures are crucial in understanding and imitating smart molecular elements such as biological cells and on-demand delivery systems. Here, we report a liquid crystal droplet (LCD) based three-dimensional system for controllable and reversible ingestion and release of guest aqueous droplets (GADs). Induced by interfacial thermodynamic fluctuation and internal topological defect, microscale LCDs with perpendicular anchoring condition at the interface would spontaneously ingest external components from the surroundings and transform them as radially assembled tiny GADs inside LCDs. Landau-de Gennes free-energy model is applied to describe and explain the assembly dynamics and morphologies of these tiny GADs, which presents a good agreement with experimental observations. Furthermore, the release of these ingested GADs can be actively triggered by changing the anchoring conditions at the interface of LCDs. Since those ingestion and release processes are controllable and happen very gently at room temperature and neutral pH environment without extra energy input, these microscale LCDs are very prospective to provide a unique and viable route for constructing hierarchical 3D structures with tunable components and compartments.
ABSTRACT
Water-in-water (w/w) emulsions are particularly advantageous for biomedical-related applications, such as cell encapsulation, bioreactors, biocompatible storage, and processing of biomacromolecules. However, due to ultralow interfacial tension, generation and stabilization of uniform w/w droplets are challenging. In this work, we report a strategy of creating stable and size-controllable w/w droplets that can quickly form polyelectrolyte microcapsules (PEMCs) in a microfluidic device. A three-phase (inner, middle, outer) aqueous system was applied to create a stream of inner phase, which could be broken into droplets via a mechanical perturbation frequency, with size determined by the stream diameter and vibration frequency. The interfacial complexation is formed via electrostatic interaction of polycations of poly(diallyldimethylammoniumchloride) with polyanions of polystyrene sodium sulfate in the inner and outer phases. With addition of negatively charged silica nanoparticles, the stability, permeability, and mechanical strength of the PEMC shell could be well manipulated. Prepared PEMCs were verified by encapsulating fluorescein isothiocyanate-labeled dextran molecules and stimuli-triggered release by varying the pH value or osmotic pressure. A model enzyme, trypsin, was successfully encapsulated into PEMCs and released without impairing their catalytic activity. These results highlight its potential applications for efficient encapsulation, storage, delivery, and release of chemical, biological, pharmaceutical, and therapeutic agents.
