Electrons travel one of two routes in a nanobiohybrid system

Peanut butter and jelly. Simon and Garfunkel. Semiconductors and bacteria. Some combinations are more durable than others. In recent years, an interdisciplinary team of Cornell researchers combines microorganisms with semiconducting nanocrystals known as quantum dots with microorganisms, and microorganisms, and aims to create nanobiohybrid systems that can capture sunlight for complex chemical transformations to apply materials and energy.

Now, the team has identified for the first time what happens when microorganisms receive electrons from quantum dots. The charge can either follow a direct pathway or be transmitted indirectly via microorganism shuttle molecules.

The findings are published in the minutes of the National Academy of Sciences. The main author is Mokshin Suri.

“In short, we discovered that there are various pathways to communicate,” said Tobias Hanrath, David Kroll professor at the Smith School of Chemistry and Biomolecular Engineering at Cornell Engineering. “It’s doubted and debated in itself, but it’s not quantified and imaged exactly as we did. This is the first fundamental step towards a long-term vision of combining digital information processing with microbial biochemistry.”

The project was launched in 2019. This initiative summarizes the microscopy capabilities of Penchen, a professor of chemistry at the University of Arts and Sciences. In 2023, the team developed a platform that imaged biohybrid systems at single-cell resolutions and analyzes where essentially electrochemical activity occurred.

For new research, researchers have decided to use a different but free approach, particularly to understand how to knock out electrons from quantum dots to microorganisms. They turned to Warren Zipfel, associate professor of biomedical engineering at Cornell Engineering. Cornell Engineering specializes in using optical microscopes for biomedical research such as tissue analysis.

“The lovely a-ha moment that Moxin contributed to this was the realization that using the same tool we could investigate the interactions between quantum dots and microorganisms that have never been done before,” Hanlas said. “So, just measuring it on its own, it’s novelty beyond the insights that came from it.”

Quantum dots are characterized by the interaction of strong light and matter, and their optical and electronic properties can be custom tailed by resizing. They have already found a way to commercial technology in the form of QD LED displays, which inject electrons and pop out photons. They work in other ways too.

“Our research essentially utilized LED functionality in reverse,” Hanlas said. “Instead of ejecting photons from injected electrons, we inject photons and see how electrons are injected from the illuminated quantum dot into nearby microorganisms.”

Quantum dots have strong interactions with light, but they are limited to relatively basic chemical transformations, and the opposite applies to microbial cells, Hanrath said. Therefore, quantum dot miclove hybrids have a very strong synergistic effect.

Fluorescence lifetime imaging microscopy was used to encourage selenide quantum quantities and Shewanella oneidensis bacteria to 2-photon excitation, identifying distinct halos surrounding microorganisms. It is seen that electrons can either migrate directly from quantum dots to microorganisms or through shuttle molecules called redox mediators.

“They have different rates, different types of distinctive time constants,” Hanras said. “And we can measure that with the fluorescence lifetime measurements we did.”

This type of photosynthetic biosystem can convert carbon dioxide into value-added chemical products such as bioplastics and biofuels, and control other microbial processes.

“It’s exciting to think about everything possible when you combine digital information processing with what microorganisms do,” Hanlas said. “If there’s a way to communicate with microorganisms, if not, you can tell them not to do that or do something really difficult by other means.”

In addition to Chen, Zipfel and Barstow, co-authors include Dr. Farshid Salimijazi. PhD student Jack Crawley. Postdoctoral researchers Young Chanpark and Binghu.