Our bodies are marvels of electrical activity, enabling us to move, sense, and interact with the world around us. While much of this electrical activity is orchestrated by the complex workings of our brains, even simpler biological entities possess the ability to generate electricity.
A recent study published in Advanced Materials unveils an intriguing discovery: a bioengineered virus capable of generating electricity when exposed to heat, a phenomenon known as pyroelectricity. Through the exploration of viruses, researchers aim to deepen our understanding of bioelectricity within the human body and harness this knowledge to develop innovative biomaterials.
Historical Background
The investigation into bioelectricity traces back to the 18th century, marked by Luigi Galvani's experiments demonstrating that electrical stimulation could induce muscle contraction in frogs. However, despite centuries of study, the molecular mechanisms underlying this bioelectric phenomenon remain elusive. Seung-Wuk Lee, a bioengineer at the University of California, Berkeley, and coauthor of the paper, remarks, "Still, we don't understand how this bioelectric phenomenon is actually happening at the molecular level."
M13 Bacteriophage
At the heart of this study lies the M13 bacteriophage, a rod-shaped virus that infects bacteria. This virus is cloaked in a molecular coat woven from nearly 3,000 copies of a helical protein. Interestingly, this protein exhibits a unique charge distribution—positively charged on the inside and negatively charged on the outside—yet the dense arrangement of the protein coat maintains charge symmetry.
Piezoelectricity
Over a decade ago, Lee's research team applied pressure to the coat proteins, inducing piezoelectricity, the ability to convert mechanical force into electricity. This pressure caused the coat proteins to change shape, breaking charge symmetry and creating polarization, resulting in the generation of an electric field and current.
In their latest study, the researchers investigated whether heat could similarly induce charge shifts and generate electricity. They modified the genetic code of the viruses to include a specific protein sequence attracted to nickel. This modification caused the viruses to bind to a thin nickel-coated plate, resembling a cityscape of skyscrapers. Upon subjecting these viral structures to heat, either through fire or laser, the proteins underwent melting and unfolding, leading to unbalanced charges and voltage generation. Lee explains, "The heat induced a polarization change, and the polarization change induced the electric potential."
While the naturally occurring helical protein exhibited some pyroelectricity, the researchers sought to enhance this property. They genetically altered the bacteriophage by adding a string of glutamate, a negatively charged building block of proteins, to the exterior of the coat protein. This modification significantly amplified the polarization change, more than doubling the pyroelectricity of the normal protein.
Syed Tofail, a physicist at the University of Limerick, praises the research, stating,
The very fact that they can genetically mutate the virus and make them pyroelectric—it's fascinating work.
To demonstrate the practical applications of this enhanced virus, Lee's team engineered the protein coat to bind to xylene, a hazardous chemical. When subjected to heat, the proteins underwent a shapeshifting process, resulting in increased electricity production. This difference in electricity could potentially be utilized to detect harmful gases, serving as biosensors.
Currently, the most successful application of pyroelectricity is in pyroelectric sensors.
says Tofail, highlighting the appeal of biological materials due to their sustainability compared to lead or lithium-based sensors.
Although the voltage generated by heating the viruses was initially small, the researchers envision scaling up the virus to power more complex electronics. Given the self-replicating nature of M13 viruses, Lee explains, "We can amplify the electricity in a similar way. It’s a big motivation."
REFERENCES
Kim H, et al. Virus-based pyroelectricity. Adv Mater. 2023;35(46):e2305503.
Piccolino M. Luigi Galvani and animal electricity: Two centuries after the foundation of electrophysiology. Trends Neurosci. 1997;20(10):443-448.
Lee BY, et al. Virus-based piezoelectric energy generation. Nat Nanotechnol. 2012;7(6):351-356.
Lee JH, et al. Vertical self-assembly of polarized phage nanostructure for energy harvesting. Nano Lett. 2019;19(4):2661-2667.
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