Siderophore-antibiotic conjugate, "SAC", is one of a method to break through antibiotic resistance in Gram-negative bacteria. Pharmaceutical companies have used a simple bidentate chelator, catechol or ortho-pyridone, as drug carriers, as in the example of cefideracol. In this case, antibiotics available are limited because they cannot pass through the endometrium when administered to gram-negative bacteria, allowing drug delivery only to periplasm. On the other hand, it has been reported that drugs can be delivered to cytoplasm in natural SAC, as in examples of albomycin. However, there are still a few examples of success, and the pattern varies depending on the type of siderophores. Accordingly, it is necessary to develop a systematic method for delivering drugs to cytoplasm using natural siderophores.
In this poster, fluorescent probes were proposed to systematically test the possibility of transmission in the Gram-negative bacterial cytoplasm of a specific composite design. The drug delivery destination is determined by siderophores, junction sites, and linkers. Based on the difference in the cellular environment in which the cytoplasm is a reducing environment rich in glutathione (GSH), whereas the periplasm is oxidative environment, the probe library was designed as a structure capable of changing optical characteristics. Enterobactin, a kind of siderophore used by Gram-negative pathogens was connected to fluorescent probe through various linkers. After the synthesized probe was treated on cells, a structure capable of cytoplasmic delivery was derived through fluorescence microscopy and flow cytometry analysis. Based on this study, it is hoped that it can be helpful in discovering SAC effective substances that actually target cytoplasm.