Researchers at the University of California San Diego have developed a tool called TRACE (tetrazine release and activation by cellular enzymes) that enables cell-specific activation of tetrazine-based chemical reactions. The work was published in Nature Chemical Biology.
Background
Bioorthogonal chemistry involves chemical reactions that occur in living systems without interfering with native biochemical processes. Tetrazine molecules are commonly used in bioorthogonal reactions due to their fast reaction kinetics. However, tetrazine reactions can be indiscriminate across cell types.
Method
TRACE uses molecular cages that encase tetrazine molecules, preventing them from reacting until a specific cellular enzyme unlocks the cage. The researchers studied various tetrazine structures to optimize uncaging rates and reaction times. They also used a competing tetrazine-reactive scavenger to suppress activation outside target cells.
Applications
The tool was tested with enzymes overexpressed in certain diseases, including using doxorubicin (DOX), a cancer drug with high toxicity. DOX was only released when the cages encountered a specific enzyme. Fluorescent probes were also developed that activate only after TRACE activation. One probe labeled cells with high alkaline phosphatase (ALP) activity, a marker elevated in some tumors, enabling precise visualization of enzyme activity on live cells.
Significance
According to Neal K. Devaraj, the method allows programming of chemical reactions in specific cell types, potentially improving drug efficacy and reducing side effects.
Funding
The research was supported by the National Institutes of Health (R35GM141939) and the German Research Foundation (KN 1447/1-1).
Authors
Authors include Caroline H. Knittel, Stormi R. Chadwick, Jacob A. Vance, Cedrik Kuehling, and Neal K. Devaraj, all from UC San Diego.