Liquid-liquid phase separation (LLPS) has great attention in biological science since it is important not only for understanding cell structure formation but also for applications such as artificial cell research, drug delivery, etc. Thus, LLPS droplet generation in a spatiotemporally controlled manner under the microscope is desirable. Laser-induced phase separation would become a powerful tool. However, there have been few reports on droplet generation which is applicable in biological experiments. One reason would be related to the fact that droplets generated by laser-induced phase separation generally need continuous laser irradiation to be kept, which becomes a drawback for the treatment of droplets and limits their applications.
The research group of Project Lecturer Mika Kobayashi (at the time of research), Assistant Professor Yoshihiro Minagawa, and Professor Hiroyuki Noji at the University of Tokyo discovered a method to produce highly stable laser-induced LLPS droplets even after switching off the laser in an aqueous two-phase system of dextran and polyethylene glycol (PEG) which has been widely used in biological applications. Using this new feature, the research group succeeded in DNA enrichment in droplets with a high enrichment factor of thousands, and the droplet exhibited extremely high longevity; the droplet retained for more than two days. In principle, the system used in this study can enrich other biomolecules such as RNA, proteins, antibodies, etc., and the method allows us a wide variety of manipulations such as patterning, division, and coalescence of droplets. Thus, the study opens new avenues for biological and medical experiments which have not able to perform before. Further, the mechanism of counterintuitive longevity poses an interesting question to physics.
Heart shape patterned by DNA-enriched droplets.
Papers
Journal: Communications Chemistry
Title: Metastable phase-separated droplet generation and long-time DNA enrichment by laser-induced Soret effect
Authors: Mika Kobayashi*, Yoshihiro Minagawa, and Hiroyuki Noji*
DOI: 10.1038/s42004-025-01438-w