Many of us may think of a cell membrane as the structure that holds a cell together, creating a building block of life. To Wei Zhou, however, it can also be a barrier to understanding what lies within. The assistant professor of ECE seeks to help scientists understand the biophysical and biochemical processes inside living cells.
By combining nanophotonics and nanoelectronics, he is building tools and processes to access the information hidden beneath the cell membrane in real time. Understanding the activities and signals inside of living cells is key to understanding disease and improving medical diagnoses and therapies, he says.
Zhou has been awarded a Young Investigator award from the U.S. Air Force Office of Scientific Research to develop a nanoscale multimodal transducer—a miniature device that takes advantage of optical and electrical phenomena at the nanometer level—to monitor and control the biological processes unfolding inside a living cell.
Combining fields at the nano level
Because of the distinct natures of electrons and photons, the operation and design rules of the device's nanoelectronic and nanophotonic components are totally different. They are products of separate fields with long, established histories, says Zhou, who specializes in both.
"Unsurprisingly, there is very limited research on hybrid electrical-optical nanodevices for interfacing with biological systems," he says.
A key innovation for his project is the plasmonic nano-optoelectrode, which can simultaneously serve as a nanoelectrode for detecting and adjusting local bioelectrical activities and as a nanoantenna for gaining intracellular access and sensing biomolecular fingerprints inside cells.
"This technology will go beyond the capability of purely electrical or purely optical methods," says Zhou. "No existing device has the ability to measure both optical and electrical signals in the same place at the same time."
Overcoming the cell membrane barrier
Before nano-transducers can interface with the cell, they need to slip inside it. Zhou will equip his devices with a way to create a "side door" from which they can observe activity or send signals in a controlled and minimally invasive manner.
By converting optical energy into thermal heating, the device can generate a miniscule vapor bubble to open a nano-sized hole on the cell's membrane.
By slipping into the bubble, the device can be internalized into the cell itself, where it will perform its electrical and optical duties.
"Establishing a reliable intracellular interface between living cells and external materials or devices can lead to significant opportunities not only for cell studies, but also for healthcare diagnosis and therapy," says Zhou.
In its role as a nanoantenna, the device concentrates light into a nanoscale spot beyond the diffraction limit—causing the photons to be absorbed or scattered, depending on how they interact with biomolecules.
While most of the scattered photons retain their original energy, a few of them are permanently, or inelastically, affected. Their energy shifts either up or down. This phenomenon, called Raman scattering, provides information about real-time biochemical signals.
Bioelectrical activity governs the movement of ions and metabolites across the cell membrane, and provides communication, processing, and coordination throughout large networks of cells.
Understanding these interactions requires accurate recording and control of voltage changes within the cell and across networks of cells, says Zhou.
Zhou will be using nanoelectronic components within his device to probe subcellular features and map bioelectrical behavior.
Measuring drug response
When the nanoscale multimodal transducer is operational, Zhou and his team plan to monitor and study the correlation between bioelectrical and biochemical activities of cells in response to drugs. Among others, they plan to study the effects of norepinephrine, because it can function in the heart and brain as a hormone and neurotransmitter.
The Air Force's Young Investigator Research Program annually awards funding to U.S. scientists and engineers who show exceptional ability and promise for conducting basic research.