 |
| Chemical name: | Cy7-Bis-dipicolylamine-zinc |  |
| Abbreviated name: | Cy7-DPA-Zn | |
| Synonym: | ||
| Agent Category: | Compound | |
| Target: | Phosphatidylglycerol and phosphates (anionic surface of bacteria) | |
| Target Category: | Binding | |
| Method of detection: | Optical near-infrared (NIR) fluorescence | |
| Source of signal/contrast: | Cy7 | |
| Activation: | No | |
| Studies: |
| Click on the above structure for additional information in PubChem. |
[PubMed]
Optical fluorescence imaging is increasingly being used to obtain images of biological functions of specific targets in vitro and in small animals (1, 2). Near-infrared (NIR) fluorescence (700–900 nm) detection avoids the background fluorescence interference of natural biomolecules, providing a high contrast between target and background tissues. NIR fluorescence imaging is becoming a non-invasive alternative to radionuclide imaging in vitro and in small animals.
Gram-negative bacterium (e.g., Escherichia coli) and Gram-positive bacterium (e.g., Staphylococcus aureus) contain negatively charged molecules such as phosphatidylglycerol and phosphates in their cell membranes (3), whereas healthy mammalian cells primarily contain phospholipids of nearly neutral charge (4). Bis-dipicolylamine-zinc (DPA-Zn) showed selective affinity for anionic phospholipids (5, 6). Cy7, a NIR carbocyanine dye, was conjugated to DPA-Zn to form Cy7-DPA-Zn for in vivo imaging of bacterial infection in mice (7, 8).
[PubMed]
The synthesis of Cy7-DPA-Zn was described by Leevy et al. (8). Cy7 was conjugated to bis-dipicolylamine via a reaction with 4-hydroxybenzoic acid to form Cy7-bis-dipicolylamine (Cy7-DPA). Zinc nitrate was added to Cy7-DPA in ethanol. After 30 min of incubation, the solution was evaporated to provide Cy7-DPA-Zn. The extinction coefficient of Cy7-DPA-Zn is 110,000 cm-1M-1, and the quantum yield is 0.14. The absorption maximum of Cy7-DPA-Zn is 794 nm, and the emission maximum is 810 nm.
[PubMed]
Leevy et al. (7) showed that incubation of Cy7-DPA-Zn with S. aureus in culture for 10 min effectively stained the periphery of the bacteria as observed with fluorescence microscopy. Leevy et al. (6) also showed that bacteria were clearly stained in preference to the membrane surface of human epithelial cells isolated from human saliva. Hanshaw et al. (5) showed that phosphatidylserine on the membrane surface of apoptotic cells (Jurkat, CHO, HeLa) were clearly stained in preference to the membrane surface of the counterpart healthy cells.
[PubMed]
Leevy et al. (7) performed in vivo fluorescence imaging in nude mice (n = 4) with an in vivo leg infection model in which 5 × 107 S. aureus colony-forming units were injected intramuscularly into the muscles overlaying the tibia bone. Cy7-DPA-Zn (0.075 mmol) was injected intravenously at 6 h after infection. The target/muscle ratio was 4.0 at 3 h and decreased slightly to 3.9 at 21 h. On the other hand, the target/liver ratio was 1.5 at 3 h and gradually increased to 2.7 at 21 h. Ex vivo imaging showed that the infected leg exhibited four-fold greater intensity than the liver and kidneys. Histoimmunochemical studies of frozen tissue sections confirmed the colocalization of Cy7-DPA-Zn with S. aureus in the infected leg. No blocking experiment was performed.
CA94056, GM059078
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