The findings provide new insight into the development of cellular condensates — organized droplets that form from cells’ liquid content. Condensates play critical roles in health and disease, and their discovery about 15 years ago drastically changed science’s understanding of cellular operation. Many fundamental aspects of how condensates arise and grow within complex cellular environments remain poorly understood.

The Princeton study looked at how condensates’ development is affected by cells’ fibrillar networks. These networks are made of thin polymer strings that stretch throughout cells. The researchers found that condensates form in spaces between the strings in a process of liquid-liquid phase separation, akin to how oil separates from water. The condensates apply physical pressure to the networks and then grow in big, abrupt bursts at the polymer strings fracture. Subsequent condensate growth then proceeds based on the condensates’ ability to draw in more biomolecules and the strength of the network to resist further fracturing.

Jason Liu, a postdoctoral researcher in the lab of PMI's Rodney D. Priestley, is lead author of the study. In addition to Liu and Priestley, the research team included PMI professors Mikko Haataja, Sujit Datta and Craig Arnold. The collaboration was supported by the Princeton Center for Complex Materials, a National Science Foundation Materials Research Science and Engineering Center.

Photo: Researchers created a physical model that mimics the material structure within cells, where small liquid droplets form within fibrous networks. In the model, individual strands confined the droplets’ expansion, squeezing the separating oily liquids into disjointed, aspherical shapes. When enough oily liquid glommed together, strands cracked, and the droplets swelled into fully formed globules. The image was provided by the researchers. Its color has been adjusted for display.