Chemical Engineering Group, Engineering and Technology Institute Groningen (ENTEG), University of Groningen, Nijenborgh 4, Groningen 9747 AG, The Netherlands.
Programa Institucional de Fomento a la Investigación, Desarrollo e Innovación (PIDi), Universidad Tecnológica Metropolitana, Ignacio Valdivieso 2409, San Joaquín, Santiago 8940577, Chile.
Langmuir. 2022 Jan 11;38(1):182-190. doi: 10.1021/acs.langmuir.1c02320. Epub 2021 Dec 16.
Micrometer-sized double emulsions and antibubbles were produced and stabilized via the Pickering mechanism by colloidal interfacial layers of polymeric nanoparticles (NPs). Two types of nanoparticles, consisting either of polylactic acid (PLA) or polylactic--glycolic acid (PLGA), were synthesized by the antisolvent technique without requiring any surfactant. PLA nanoparticles were able to stabilize water-in-oil (W/O) emulsions only after tuning the hydrophobicity by means of a thermal treatment. A water-in-oil-in-water (W/O/W) emulsion was realized by emulsifying the previous W/O emulsion in a continuous water phase containing hydrophilic PLGA nanoparticles. Both inner and outer water phases contained a sugar capable of forming a glassy phase, while the oil was crystallizable upon freezing. Freeze drying the double emulsion allowed removing the oil and water and replacing them with air without losing the three-dimensional (3D) structure of the original emulsion owing to the sugar glassy phase. Reconstitution of the freeze-dried double emulsion in water yielded a dispersion of antibubbles, i.e., micrometric bubbles containing aqueous droplets, with the interfaces of the antibubbles being stabilized by a layer of adsorbed polymeric nanoparticles. Remarkably, it was possible to achieve controlled release of a flourescent probe (calcein) from the antibubbles through heating to 37 °C leading to bursting of the antibubbles.
通过胶体界面层的聚合物纳米粒子（NPs）的Pickering 机制，制备并稳定了微米级的双乳液和反气泡。两种类型的纳米粒子，由聚乳酸（PLA）或聚乳酸- 聚乙二醇酸（PLGA）组成，通过反溶剂技术合成，不需要任何表面活性剂。PLA 纳米粒子只有通过热处理调节疏水性后，才能稳定油包水（W/O）乳液。通过在含有亲水性 PLGA 纳米粒子的连续水相中乳化先前的 W/O 乳液，实现了水包油包水（W/O/W）乳液。内水相和外水相都含有一种能够形成玻璃态的糖，而油在冷冻时可结晶。双乳液的冷冻干燥允许去除油和水，并在不失去原始乳液的三维（3D）结构的情况下用空气代替它们，这是由于糖的玻璃态。在水中重构冷冻干燥的双乳液会产生抗气泡的分散体，即含有水滴的微米级气泡，抗气泡的界面由吸附的聚合物纳米粒子层稳定。值得注意的是，通过加热至 37°C 可以实现从抗气泡中释放荧光探针（钙黄绿素）的控制释放，从而导致抗气泡破裂。
