Journal: Nature Communications
Article Title: Near-infrared fluorogenic RNA for in vivo imaging and sensing
doi: 10.1038/s41467-024-55093-1
Figure Lengend Snippet: a Modular design of the Squash-based NIR fluorescent sensor for small molecule targets. The target binding aptamer (blue) was fused to Squash (beige) through a transducer module (black). Target binding induces the allosteric conformation of tetracycline aptamer, then stabilizes the helix structure of the transducer domain, thus enabling Squash to bind NIR fluorophore. b , c Optimization of the transducer for small molecules sensor. The optimal tetracycline sensor ( b ) containing transducer 2 domain (black box), or SAM sensor ( c ) was chosen with the highest signal-to-background of 14-fold or 5-fold, respectively. Data represent mean values ± s.d. for n = 3 independent experiments. d Using Squash-based NIR fluorescent sensors to image tetracycline in living cells. We expressed the tetracycline sensor in HEK293T cells. Cells treated with tetracycline (0.1 mM) showed increased NIR fluorescence. Image acquisition time, 500 ms. Scale bar, 20 µm. Data represent mean values ± s.d. for n = 3 independent experiments. e Squash-based NIR fluorescent sensor for tetracycline imaging in vivo. We incubated sensor-expressing cells (10 8 cells) in the presence or absence of tetracycline (0.1 mM). Then, we transplanted these cells to mice by subcutaneous injection. After 2 h, DFQL-1T (10 µM) was injected in situ for imaging. Mice transplanted with tetracycline-treated cells exhibit higher NIR fluorescence (bottom row). Image acquisition time, 500 ms. Data represent mean values ± s.d. for n = 3 independent experiments. f Imaging SAM in live cells in the NIR channel. We readily detected NIR fluorescence in cells expressing SAM sensors. After being treated with cycloleucine (30 mM), NIR fluorescence decreased significantly. Scale bar, 20 µm. Data represent mean values ± s.d. for n = 3 independent experiments. g Monitoring SAM metabolites in vivo. Engineered HEK 293T cells expressing SAM sensor (10 8 cells) were incubated with cycloleucine (30 mM) for 1 h. Cells were then transplanted into mice by subcutaneous injection. About 2 h after transplant, DFQL-1T (10 µM) was injected in situ for imaging. Sensor-expressing cells display pronounced skin-permeable NIR fluorescence in mice. Cycloleucine treatment induced a significant decrease in fluorescence. Image acquisition time, 500 ms. Data represent mean values ± s.d. for n = 3 independent experiments.
Article Snippet: After adding cycloleucine (30 mM, Ark Pharm AK-29341), we imaged the cells for 2 h at 15-min intervals.
Techniques: Binding Assay, Fluorescence, Imaging, In Vivo, Incubation, Expressing, Injection, In Situ