Fluorescent proteins have revolutionized science, allowing researchers to tag and visualize individual molecules in living cells, tissues, and animals. Researchers have used these tools to watch viruses infect cells in real time, watch cells collect garbage, and track the signaling that drives tumor growth.
Salk scientists and collaborators at the Albert Einstein College of Medicine have advanced this visualization technology. This new technology, called visible spectrum antigen-stabilized fluorescent nanobodies (VIS-Fbs), has been validated in multiple mammalian cell types and provides a powerful tool for a wide range of life science research applications.
This research nature method April 22, 2026.
“This study establishes a versatile platform for imaging proteins with high specificity and minimal background,” said co-corresponding author Axel Nimmerjahn, Ph.D., Salk University Professor and Françoise Giraud Salk Professor. “This opens new opportunities to study how molecular and cellular processes unfold in real time across diverse biological systems.”
How can current mobile imaging technology be optimized?
The innovation began with small protein fragments called nanobodies that could be engineered to bind to specific protein targets within living cells. When fused to fluorescent proteins, these nanobody-based probes can reveal the location of target proteins and their behavior. However, traditional versions can generate signal even when unbound, which can result in background fluorescence that obscures details.
Salk and Einstein’s team designed a new type of probe that significantly reduces background fluorescence while preserving the targeting ability of nanobodies. VIS-Fb stably fluoresces only when bound to the target of interest. This binding-dependent (“on-demand”) fluorescence reduces background noise by up to approximately 100-fold, allowing for clearer visualization of protein position and dynamics.
Additionally, the researchers have developed multiple versions of this new probe that fluoresce across nearly the entire visible spectrum, from blue to far red. With so many color options, you can track multiple cell targets simultaneously. Certain VIS-Fb variants can also be turned “on” and “off” by light, making it possible to track protein behavior over time with high spatial and temporal precision. The researchers also established a modular design framework that allows the VIS-Fb probe to be rapidly adapted to different targets and functional readouts.
What do scientists use optical probes to study?
This new technology will enable scientists to gain more accurate and timely insights into cellular activity, even in complex environments such as living brain tissue. Researchers demonstrated the functionality of VIS-Fbs across a variety of biological models.
In a mouse model, the VIS-Fb probe enabled selective labeling and ratiometric imaging of calcium activity in behaving neurons and astrocytes. In zebrafish, this technology has made it possible to track dynamic changes in real time early in development and in response to drugs that alter signaling pathways.
“Our results show that this imaging platform provides a clearer and more accurate view of how proteins behave within living systems,” said study co-author Vladislav Verkuša, Ph.D., professor and co-director of the Grass Ripper Center for Biophotonics at Albert Einstein College of Medicine. “This opens the door to studying complex biological processes such as cell signaling, development, and disease progression in new ways.”
Other authors and funding
Other authors include Erin Carey of Salk; Natalia Barykina, Juliana Mendonça-Gomez, and Sofia de Oliveira from Albert Einstein College of Medicine; Olena Olynik of the University of Helsinki.
This study was funded by the National Institutes of Health (GM122567, NS123719, GM147416), the Jane and Artos Erkko Foundation, the Finnish Research Council, the Finnish Cancer Foundation, the Chan Zuckerberg Initiative Foundation, the NOMIS Foundation (Salk Neuroimmunology Initiative), and the Edwards Jaeckel Research Foundation.
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Reference magazines:
Ballykina, Nevada; others. (2026). Synthetic multicolor antigen-stabilized nanobody platform for cross-labeling and functional imaging. nature method. DOI: 10.1038/s41592-026-03056-3. https://www.nature.com/articles/s41592-026-03056-3
