Bioluminescent probes are powerful tools for visualizing biology in live tissues and whole animals. Recent years have seen a surge in the number of new luciferases, luciferins, and related tools available for bioluminescence imaging. Many were crafted using classic methods of optical probe design and engineering. Here we highlight recent advances in bioluminescent tool discovery and development, along with applications of the probes in cells, tissues, and organisms. Collectively, these tools are improving in vivo imaging capabilities and bolstering new research directions.
Bioluminescence
imaging with luciferase-luciferin pairs is commonly
used for monitoring biological processes in cells and whole organisms.
Traditional bioluminescent probes are limited in scope, though, as
they cannot be easily distinguished in biological environments, precluding
efforts to visualize multicellular processes. Additionally, many luciferase-luciferin
pairs emit light that is poorly tissue penetrant, hindering efforts
to visualize targets in deep tissues. To address these issues, we
synthesized a set of π-extended luciferins that were predicted
to be red-shifted luminophores. The scaffolds were designed to be
rotationally labile such that they produced light only when paired
with luciferases capable of enforcing planarity. A luciferin comprising
an intramolecular “lock” was identified as a viable
light-emitting probe. Native luciferases were unable to efficiently
process the analog, but a complementary luciferase was identified
via Rosetta-guided enzyme design. The unique enzyme–substrate
pair is red-shifted compared to well-known bioluminescent tools. The
probe set is also orthogonal to other luciferase-luciferin probes
and can be used for multicomponent imaging. Four substrate-resolved
luciferases were imaged in a single session. Collectively, this work
provides the first example of Rosetta-guided design in engineering
bioluminescent tools and expands the scope of orthogonal imaging probes.
Engineered luciferases and luciferins have dramatically expanded the scope of bioluminescence imaging in recent years. Multicomponent tracking remains challenging, though, due to a lack of streamlined methods to visualize combinations of bioluminescent reporters. Here we report a strategy for rapid, multiplexed imaging with a wide range of luciferases and luciferins. Sequential addition of orthogonal luciferins, followed by substrate unmixing, enabled facile detection of multiple luciferases in vitro and in vivo. Multicomponent imaging in mice was also achieved on the minutes-to-hours time scale, a vast improvement over conventional protocols..
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