Light-Regulated Liquid-Liquid Phase Separation for Spatiotemporal Protein Recruitment and Cell Aggregation.


Ikeuchi N(1), Komachi T(1), Murayama K(2), Asanuma H(2), Maruyama A(1), Shimada N(1).
Author information:
(1)Department of Life Science and Technology, Tokyo Institute of Technology, 4259 Nagatsuta-cho, Midori-ku, Yokohama, Kanagawa 226-8503, Japan.
(2)Department of Biomolecular Engineering, Graduate School of Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603, Japan.


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.