Department of Chemical and Biomolecular Engineering, University of Pennsylvania , Philadelphia, Pennsylvania 19104, United States.
ACS Appl Mater Interfaces. 2016 Sep 28;8(38):25603-11. doi: 10.1021/acsami.6b07939. Epub 2016 Sep 13.
Diverse fields including drug and gene delivery and live cell encapsulation require biologically compatible encapsulation systems. One widely adopted means of forming capsules exploits cargo-filled microdroplets in an external, immiscible liquid phase that are encapsulated by a membrane that forms by trapping of molecules or particles at the drop surface, facilitated by the interfacial tension. To eliminate the potentially deleterious oil phase often present in such processes, we exploit the aqueous two phase system of poly(ethylene glycol) (PEG) and dextran. We form capsules by placing dextran-rich microdroplets in an external PEG-rich phase. Strong polyelectrolytes present in either phase form complexes at the drop interface, thereby forming a membrane encapsulating the fluid interior. This process requires considerable finesse as both polyelectrolytes are soluble in either the drop or external phase, and the extremely low interfacial tension is too weak to provide a strong adsorption site for these molecules. The key to obtaining microcapsules is to tune the relative fluxes of the two polyelectrolytes so that they meet and complex at the interface. We identify conditions for which complexation can occur inside or outside of the drop phase, resulting in microparticles or poor encapsulation, respectively, or when properly balanced, at the interface, resulting in microcapsules. The resulting microcapsules respond to the stimuli of added salts or changes in osmotic pressure, allowing perturbation of capsule permeability or triggered release of capsule contents. We demonstrate that living cells can be sequestered and interrogated by encapsulating Pseudomonas aeruginosa PAO1 and using a Live/Dead assay to assess their viability. This method paves the way to the formation of a broad variety of versatile functional membranes around all aqueous capsules; by tuning the fluxes of complexing species to interact at the interface, membranes comprising other complexing functional moieties can be formed.
包括药物和基因传递以及活细胞封装在内的多个领域都需要生物相容性的封装系统。一种广泛采用的形成胶囊的方法是利用充满货物的微滴在外部不混溶的液相中，通过在液滴表面捕获分子或颗粒形成的膜来封装，这得益于界面张力。为了消除此类过程中可能存在的有害油相，我们利用聚乙二醇（PEG）和葡聚糖的水相两亲系统。我们通过将富含葡聚糖的微滴置于富含 PEG 的外部相中形成胶囊。两种相中存在的强聚电解质在液滴界面形成复合物，从而形成封装流体内部的膜。这个过程需要相当的技巧，因为两种聚电解质都可溶于滴或外部相，而极低的界面张力太弱，无法为这些分子提供强吸附位。获得微胶囊的关键是调节两种聚电解质的相对通量，使其在界面相遇并发生络合。我们确定了在内部或外部液滴相中发生络合的条件，分别导致微颗粒或封装不良，或者在适当平衡时，在界面处发生络合，形成微胶囊。所得微胶囊响应添加盐或渗透压变化的刺激，允许干扰胶囊渗透性或触发胶囊内容物的释放。我们证明可以通过封装铜绿假单胞菌 PAO1 并使用 Live/Dead 测定法来评估其活力来隔离和检测活细胞。这种方法为在所有水相胶囊周围形成各种多功能功能膜铺平了道路；通过调节络合物种的通量在界面上相互作用，可以形成包含其他络合功能部分的膜。
