Episode 24: Gold nanoparticles modify electrical behavior inside living cells

Sophia Chen of MRS Bulletin interviews Frankie Rawson of the University of Nottingham, UK, about wirelessly manipulating the electrical behavior of living cells. His research group does so by applying an external voltage to Au nanoparticles inserted into the cell. The voltage causes a molecule attached to each Au nanoparticle to undergo a redox reaction, in which atoms give up or accept electrons from each other. Read the abstract in Applied Nano Materials.
Transcript
SOPHIA CHEN: Tiny electrical currents flow in many parts of the human body. For example, ions moving inside cells or crossing cell membranes. Many instances of these electrical currents occur because of a type of chemical reaction in the cell known as a redox reaction, in which atoms give up or accept electrons from each other. 

FRANKIE RAWSON: Ultimately, redox reactions underpin how cells make energy. 

SC: Frankie Rawson is a bioengineer at the University of Nottingham in the UK. He’s designing materials that can be placed into a live cell—and modify its electrical behavior.

FR: Biology is largely underpinned by electrical behavior, and we’re starting to realize that if we can merge and develop materials that seamlessly integrate with that biology we can control the electrical input and output on a really targeted scale. 

SC: In the past, to manipulate a cell’s electrical behavior, researchers would have to place nanowires inside the cell. Rawson and his team have recently demonstrated that they can do this wirelessly. Essentially, they drove a redox reaction in the cell, and they did it like this. They inserted modified gold nanoparticles into the cell. Then, they applied an external voltage. They applied a relatively low 150 volts compared to the kilovolts used in prior experiments. This basically causes a molecule attached to each gold nanoparticle to undergo a redox reaction. The nanoparticle helps direct the external electric field. 

FR: The gold nanoparticle acts as an electrical antennae, effectively. 

SC: The researchers confirmed that the redox reaction occurred using two different methods. First, they illuminated the molecule attached to the gold nanoparticle, a type of molecule known as zinc porphyrin, with yellow light and monitored its fluorescence. Zinc porphyrin’s fluorescence changes depending on its number of electrons. When the molecule gains an electron, its fluorescence dims, signifying that the redox reaction has occurred. At the same time, the researchers also performed a measurement known as cyclic voltammetry, in which they measure electrical behavior of the nanoparticle while changing an applied voltage. These two methods collectively indicated that they had triggered a redox reaction at the surface of the gold nanoparticle inside the cell wirelessly. 

FR: What that means is, that’s moving toward that step where you don’t need a physical wire connection inside the cell to actuate electrochemical behavior inside the cell. 

SC: Ultimately, the bigger goal is to use the zinc porphyrin redox reaction to drive other reactions inside the cell. Rawson wants to trigger redox reactions in a cell that would kill it. 

FR: If everything goes to plan, the research hypothesis is that you can use this as a bioelectronic drug. You put this in an organism; you can target the electric field in a location in that organism, and switch on cell death. Our hypothesis is to use this to kill cancer cells. 

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