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A team of Harvard researchers has recently developed a new laser scalpel which enables the unprecedented precision of operating on a single cell.
McKay Professor of Physics Eric Mazur led the effort to develop and implement the laser scalpel, which experts say will revolutionize the world of mechanobiology and nanobiology.
“The most important thing is that the technique is now more precise. We can focus the laser down to a point, where the region of damage is less than one micrometer in diameter within tissues or cells,” said second year graduate student Sam Chung, who was one of the researchers.
The laser puts an “incredible” amount of power in an “exquisitely” small space because the laser is focused through an objective lens, according to fellow collaborator Donald Ingber, professor of pathology at Harvard Medical School and the Vascular Biology Program at Children’s Hospital. Ingber said that the laser then creates plasma which vaporizes everything in that small space.
The apparatus is called a femtosecond laser because it emits pulses of light in extremely short bursts—the equivalent of a millionth of a billionth of a second.
According to Chung, the laser emits 1,000 bursts of light per second.
“This is actually considered slow, but because the light is crammed into such a short time, the intensity of light is very high. Because of that high intensity, there is high power at the focal point,” he said. “For example, normally, light will pass through a window, but in our case, our light will stop in the cell at the focal point and cause damage. Outside of the focal volume, there is no collateral damage. Thus, damage is confined and we don’t have to cut anything.”
Many professors are utilizing the new laser technique to help their research.
“We are trying to develop an in vitro way to study the motor mechanism of the flagella,” Smith Professor of Physics and Professor of Molecular and Cellular Biology Howard C. Berg said.
The laser is also being used to study nerve cells in C. elegans nematodes. Each nematode is comprised of 1,000 cells and has 302 neurons, each connected to each other the same way. Utilizing the exactness of the laser, researchers can now sever precise axon connections—akin to cutting wires in a circuit—to note behavioral changes within the worm, according to Assistant Professor of Physics Aravinthan Samuel.
The ability of the laser beam to create plasma within the cell, vaporizing matter in the process, makes it invaluable in the field of mechanobiology—which is primarily concerned with the importance of mechanics and structure in the regulation of cell form and function, as well as tissue development, Ingber said.
“For example, cells contain an internal filamentous framework or a ‘cytoskeleton’ that...is critical for how cells move, change shape and grow, and thus is critical for tissue development and wound healing. The nanosurgical method we developed...allows us to manipulate structures in the nanometer scale. We hope to use it to study how molecular filaments and structural elements in cells contribute to their form and function,” he said.
In addition, scientists have predicted uses for the laser to knock out certain organelles in cells to watch cellular responses.
“For instance, you could wipe out all of the neurotransmitter secretory vesicles in a part of a neuron, and then watch how new vesicles are made and trafficked to the site of secretion,” said David W. Piston, professor of molecular physiology and biophysics at Vanderbilt University.
“Ultimately, however, chemical and biological tools have only species specificity, but you don’t have spatial selectivity. So, we have given biologists the ability to add spatial selectivity to their array of research tools,” Mazur said.
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