Stabilizing Coacervate by Microfluidic Engulfment Induced by Controlled Interfacial Energy

Abstract

Low interfacial energy, an intrinsic property of complex coacervate, enables the complex coacervate to easily encapsulate desired cargo substances, making it widely used in encapsulation applications. Despite this advantage, the low interfacial energy of the complex coacervate makes it unstable against mechanical mixing, and changes in pH and salt concentration. Hence, a chemical cross-linker is usually added to enhance the stability of the complex coacervate at the expense of sacrificing all intrinsic properties of the coacervate, including phase transition of the coacervate from liquid to solid. In this study, we observed an abrupt increase in the interfacial energy of the coacervate phase in mineral oil. By controlling the interfacial energy of the coacervate phase using a microfluidic device, we successfully created double engulfed PEG-diacrylate (PEGDA) coacervate microparticles, named DEPOT, in which the coacervate is engulfed in a cross-linked PEGDA shell. The engulfed coacervate remained as a liquid phase, retained its original low interfacial energy property to encapsulate the desired cargo substances, and infiltrated into the target site by a simple solvent exchange from oil to water.

Multiphasic Coacervates Assembled by Hydrogen Bonding and Hydrophobic Interactions

“…43 To understand the formation of core−shell multiphasic coacervates, we examined the spreading coefficients (S i ) of the coacervates, where S i = γ jk − (γ ij + γ ik ). The γ ij , γ jk , and γ ik are the interfacial tensions between two liquid phases i and j, j and k, and i and k. 89 These spreading coefficients determine three possible scenarios for the organization of two immiscible droplets, immiscible, partial wetting, and core−shell (complete wetting), as shown in Figure 6D. As an example, we analyzed 2) for the formation of a C4−E1 in C2−E0 core−shell structure, which is the same as experimental observations (Figure 6F).…”

“…43 To understand the formation of core−shell multiphasic coacervates, we examined the spreading coefficients (S i ) of the coacervates, where S i = γ jk − (γ ij + γ ik ). The γ ij , γ jk , and γ ik are the interfacial tensions between two liquid phases i and j, j and k, and i and k. 89 These spreading coefficients determine three possible scenarios for the organization of two immiscible…”

Coacervate Droplets for Synthetic Cells

“…This terpolymer was assumed to have a sufficient length to span the coacervate/water interface. [ 257 ] Last, components forming a “gelled” corona, e.g., via polymer cross‐linking [ 260 ] or gelation [ 261 ] or DNA hybridization, [ 196 ] have also been reported to prevent coacervate fusion.…”