Light-Regulated Liquid–Liquid Phase Separation for Spatiotemporal Protein Recruitment and Cell Aggregation
Nao Ikeuchi, Takuya Komachi, Keiji Murayama, Hiroyuki Asanuma, Atsushi Maruyama, Naohiko Shimada
Abstract
We have previously shown that the upper critical solution temperature-type thermoresponsive ureido polymers such as polyallylurea and poly(2-ureidoethylmethacrylate) derivatives show liquid–liquid phase separation (LLPS), also known as simple coacervation, under physiological conditions below their phase-separation temperatures (Tp). The addition of the polymer-rich coacervate droplets that result from LLPS to a monolayer cell culture induced aggregation of cells into multicellular spheroids. In this study, we prepared a ureido copolymer, poly(vinylamine-co-vinylurea), with azobenzene substituents (Azo-PVU) and demonstrated light-guided assembly and disassembly of LLPS coacervates. Azo-PVUs with Tp values ranging from 10 to 52 °C were prepared by changing the azobenzene content. Ultraviolet light caused a decrease in the Tp of Azo-PVU because of trans-to-cis photoisomerization of the azobenzene and irradiation with visible light increased the Tp. Thus, LLPS of Azo-PVU was reversibly controlled. The coacervate droplets deposited on a dish surface were immediately dissolved by targeted UV irradiation (owing to a decrease in the Tp). Spatially controlled recruitment of proteins on the dish surface was achieved when protein solution was added to the light-patterned surface. Furthermore, the light-guided deposition of coacervates resulted in the spatiotemporal transformation of monolayer cells to aggregates. This light-controlled LLPS will allow the preparation of novel liquid-based materials for biomolecular and cellular engineering.