Assistant Professor of Physics Viva Horowitz works with Clare Nele '24, Trevor Scheuing '23, and Matt Jankowski '22 on a project to build and investigate the dynamics of a simple artificial cell in their lab.
Assistant Professor of Physics Viva Horowitz was working as a postdoctoral fellow at Harvard when she began to take a more serious interest in the dynamics of a cell’s cytoplasm. “In physics, we have equations that allow us to model things and predict how things will move,” Horowitz said. “And it turns out that the cytoplasm completely breaks those rules — there’s motors pushing things around.”

This knowledge inspired Horowitz to begin the project of replicating certain parts of cells. Six years later, she is continuing this work with the help of three Hamilton students: Matt Jankowski ’22, Trevor Scheuing ’23, and Clare Nelle ’24. By the end of the summer, Horowitz said, the team hopes to build a “minimal” yet effective model of a cell and its motors. 

To accomplish this, they are using water suspended in oil for the cytoplasm and plastic-platinum “Janus swimmers” for the motors. These are a kind of Janus particle, which, as the name suggests, are composed of two different materials. In this case, one half of the particles is plastic, and the other half is platinum —asymmetry that propels the “swimmers” via a chemical reaction between the platinum side and the addition of hydrogen peroxide. 

The team plans to track the dynamics of the cytoplasm using tracers, inert particles that will help to illuminate the patterns of motion within the cell. By introducing a chemical “crowding agent” into the cells, Scheuing said that the fluid will “become more viscous … and then that would hopefully cause the Janus particles to push the tracers along faster.” This, they expect, will make the results of their experiment easier to observe. 

While waiting for a fresh batch of Janus swimmers to arrive at the lab, the students are working to address other challenges presented by the project. Among these is “drift,” or the unwanted movement of the artificial cells as a whole that hinders the students’ ability to image and analyze them.

They have tried using a computer program to mitigate the impact of drift, Nelle said, but with mixed success. “If the whole cell was moving across the screen, the program would recognize that that’s not part of the random motion we’re trying to observe because it’s obvious that everything’s moving with it,” Nelle said. “But that doesn’t work perfectly, and our goal is to not have that be an issue at all.”

All the same, dealing with such challenges is a big theme in any scientific endeavor, Horowitz said. Experience working with students on actual research in the lab, she added, is both enjoyable for her and incredibly valuable for them: “I have the opportunity to tell the students that you’re contributing to research goals that I really care about, and that the world might care about … we are pushing at the boundaries of human knowledge.”

Reflecting on the project so far, Jankowski expressed his appreciation for its interdisciplinary nature—combining elements of biology, chemistry, and physics. “This project is a pretty nice synthesis of what a Hamilton student may experience during their time as a natural science student, because it draws from so many different fields that you would not have thought would have been able to come together otherwise,” he explained. “I’ve had a blast.”

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