Chemists unravel the workings of an essential contrast agent, paving the way for the development of new markers necessary for correlative microscopy, which can capture both the structure and signaling processes of cells simultaneously.
Two research groups at the University of Utah’s Department of Chemistry collaborated to enhance imaging tools, potentially allowing scientists to gain deeper insights into cellular signaling and other vital molecular processes essential for life.
The Noriega and Hammond laboratories, which specialize in materials chemistry and chemical biology, made significant findings released this month in the Journal of the American Chemical Society. Their collaborative effort began with a team development grant from Utah’s College of Science and the 3i Initiative, aimed at promoting interdisciplinary research to tackle larger scientific questions.
“We are working on a novel imaging technique that allows for observation of cells’ intricate structural features while simultaneously capturing their activity,” remarked co-author Ming Hammond. “Existing methods achieve excellent resolution for cellular structure but often miss functional aspects. In this research, we investigate a tool that could potentially be utilized in electron microscopy to provide insights into both structure and function at once.”
Biological samples frequently require “markers,” or molecules that emit detectable signals, according to co-author Rodrigo Noriega. One common type of marker is flavoproteins, which, when activated by light, initiate a chemical reaction generating metal-absorbing polymer particles that contrast sharply in electron microscopy.
“Earlier research concentrated on the markers without incorporating the materials they produce, but our study includes the materials chemistry aspects in the model,” explained Noriega, who was recently awarded the Sloan Research Fellowship, which recognizes promising early-career scientists aiming to transform their disciplines.
For a long time, scientists believed that singlet oxygen generation, a unique form of reactive oxygen species, was key to the mechanism. However, the University of Utah team discovered that the primary factor is the electron transfer between the photoexcited marker and the polymer precursors.
“We are investigating a tool frequently used for this novel imaging and that many assumed functioned in a particular manner,” Hammond noted, “but our photophysical research uncovered an unexpected mechanism.” This previously unnoticed electron transfer pathway produces reactive species that provide the necessary contrast for electron microscopy without relying on singlet oxygen.
This new understanding may assist researchers in refining the design of these markers, according to Noriega and Hammond. The collaborative team has built on these findings to diversify the types and combinations of polymer building blocks utilized, as well as implement markers that are less effective as singlet oxygen sources but excel in electron transfer, and to create contrast agents in previously challenging environments.
“In addition to their applications in electron microscopy, these markers enable the generation of two images from the same sample: one through light microscopy and the other via electron microscopy. This multi-layered approach yields significantly more information than each method alone,” Noriega stated. He likened this method, known as correlative microscopy, to the various layers seen in Google Maps.
These advancements may enhance scientists’ comprehension of cell signaling—an essential aspect of life—both within single cells and across cell communities.
“Cells communicate through chemical signals, which is their method of determining whether neighboring cells are amicable or hostile. This communication influences how they collaborate, compete, and even camouflage themselves in a community,” Hammond added. Mapping these chemical signals among groups of cells in a complex arrangement necessitates detecting activity levels within the spatial context of the sample structure. “We aspire to visualize their interactions, as well as their surroundings.”