Majima et al. synthesized a new far-red fluorescence probe composed of silicon-containing rhodamine and anthracene moieties, namely Si-DMA, as a chromophore and a ¹O₂ reactive site, respectively. In the presence of ¹O₂, fluorescence of Si-DMA increases 17 times due to endoperoxide formation at the anthracene moiety^(1),(2). Among seven different ROS, Si-DMA is able to selectively detect the ¹O₂ (Fig. 3). In addition, Si-DMA is able to visualize the real-time generation of ¹O₂ from protoporphyrin IX in mitochondria with 5-aminolevulinic acid (5-ALA), a precursor of heme(Fig. 4).

Usage ExampleFluorescence microscopic detection of ¹O₂ in HeLa cells after added 5-aminolevulinic acid (5-ALA)1. HeLa cells (2.4×10⁵ cells/ml, Hanks’ HEPES buffer 200 μl) were seeded on a μ-slide 8 well (Ibidi) and cultured at 37^oC in a 5%CO₂ incubator overnight.2. Cells were washed with 200 μl Hanks’ HEPES buffer twice.3. 150 μg/ml of 5-ALA in Hanks’ HEPES buffer was added to the μ-slide and cultured at 37^oC in a 5%CO₂ incubator for 4 hours.4. Cells were washed with 200 μl Hanks’ HEPES buffer twice.5. 200 μl of Si-DMA working solution (40 nmol/L) was added and cultured at 37^oC in a 5%CO₂ incubator for 45 minutes.6. Cells were washed with 200 μl Hanks’ HEPES buffer twice.7. 200 μl Hanks’ HEPES buffer was added and observe the cells under a fluorescence microscope.