Site-selective modification of aminoglycoside antibiotics for therapeutic and diagnostic applications

Aminoglycosides are a potent class of broad-spectrum bactericidal antibiotics and promising starting building blocks for the development of new leads. However, their further use requires a better understanding of the drug modes of action and their derivatives and getting more insights into mechanisms of bacterial resistance. In Chapter 1, the structures, mode of action, and currently known mechanisms of bacterial resistance to aminoglycosides and some of the most potent strategies to overcome bacterial resistance are described. Chapter 2 describes the design and chemical modification of the aminoglycoside neomycin B to improve its antimicrobial function against resistant bacteria. Moreover, we crystalized and resolved the structure of the previously unknown AAC(3)IIIa enzyme, in complex with its natural substrates and the newly developed, most potent derivative. We proposed the mechanism of enzymatic modification catalyzed by the enzyme in the presence of the substrate neomycin B and showed that the newly developed derivative binds to the enzyme in a changed configuration. In Chapter 3, we aimed to achieve spatial and temporal control over aminoglycoside activity by transforming the drug to a temporarily inactivated derivative, which can be re-activated by light. In Chapter 4, we synthesised a library of fluorescently labelled aminoglycosides and investigated their photophysical properties, structure related function, activity and the uptake in E. coli. In Chapter 5, we applied developed fluorescent aminoglycosides conjugates as probes for imaging of Gram-negative bacteria in vitro and in vivo in mouse models rendering the developed fluorescent aminoglycoside conjugates very promising tracers for in-situ diagnostics of infections induced by Gram-negative bacteria.