Nain explained that cell membrane disruption is linked to the loss of contractility-bearing cytoskeleton inside the cell. He described the cytoskeleton as a dynamic and responsive meshwork; its re-establishment is required for recovery of the cell’s contractility and shape.
“It is remarkable how the cell cytoskeleton can fully recover within just a couple of hours, despite extensive damage caused by electric fields,” Jana said. “This shows the strong will of cells to live even after extreme perturbations. Such incredible cell adaptability in our suspended nanofibers further highlights how cancer cells can evade electric field treatments and still continue on metastasizing.”
“It was amazing to see just how dynamic and responsive cells really are after electrical disruption,” added Graybill. “It was exciting to find that the loss of contractile force measured in one cell type also occurred in other cell types, because this suggested that this behavior is consistent across many cell types.
"This was exciting, because a better understanding of cell recovery may improve techniques where cell recovery is desirable, such as in gene transfection, electrofusion, electrochemotherapy, or where cell recovery is undesirable, such as in cancer treatments, where it’s preferable for the cancerous cells to die.”
The researchers believe their new understanding of cell contraction and recovery has important implications for electroporation’s use in various applications, including molecular medicine, genetic engineering, and cellular biophysics. Nain said that the biphasic response they observed could enable the injection of larger particles into the cell, without having to use a higher electric voltage.
The cell membrane is like an insulator, and when you apply a voltage, the electrical pulse travels across the membrane, explained Davalos. At a critical voltage, pores form on the cell. The magnitude of the electric field controls whether or not pores will form in the membrane, while the various pulse parameters dictate the size of the particle that can be put into the cell.
Trying to increase those parameters could affect the particle size one can inject, but the higher the electrical voltage, the more likely the cell is to die. There is also a very narrow window where pores are open and able to receive materials before the cell reseals. The overall goal of electroporation is to disrupt the cell so that substances – such as medicine or DNA – can be injected into it. Identifying and understanding how long the disruption lasts is thus very important.
“This shows the strength of collaboration across disciplines,” Nain said. “I knew about the electric field research by Davalos and wondered how we could integrate nanonet force microscopy, the cell force measurement platform developed in my lab, with electrical fields. Together, we have discovered a new phenomenon in a well-established field.”
In Nain and Davalos’ study, the cells attached to suspended fibers were able to sustain high electrical voltages while enabling the precise measurement of forces. This holds great promise to deliver macromolecules in the cells efficiently, they said.
“This platform has broadened that reversible window,” Davalos said. “This is exciting because the opportunity for introducing larger particles increases without the risk of killing the cell. This could have major implications in genetic engineering and molecular medicine. Achieving this in realistic fibrous environments opens new possibilities for translating the technology.”
The research was conducted by an interdisciplinary team from multiple engineering backgrounds. Philip Graybill and Aniket Jana, Ph.D. students in mechanical engineering, are equal authors on the publication, and are joined by Rakesh Kapania, Norris and Laura Mitchell Professor in the Kevin T. Crofton Department of Aerospace & Ocean Engineering.
-Written by Laura McWhinney and Alex Parrish