Bacterial resistance represents an increasingly significant problem in healthcare, which is why researchers are focusing on developing new approaches for the prevention of bacterial infections. Escherichia coli is one of such bacteria causes urinary tract infections and triggers the relapse of Crohn's disease. It develops resistance through the formation of biofilms, which protect it from external influences. Of key importance for infection initiation and biofilm formation, is the adhesion of the bacterial cell to the mucosal surface through specialized fimbriae, containing the lectin FimH at their tip, capable of binding to D-mannose residues of glycoproteins on the surface of human cells. Therefore, our main objective is the successful preparation of functionalised magnetic nanorods that would rotate in a rotating magnetic field, bind to FimH, and mechanically remove bacterial cells from biofilms.
As part of the experimental work, we designed and synthesized a D-mannose antagonist of the FimH lectin based on a biaryl lead compound discovered by the research group of Prof. Dr. Tomašič and co-workers. Instead of the terminal ester group, we attached a protected silanol functional group via an amide bond and a linker. In addition to the antagonist, we also designed a D-glucose and a polyethylene glycol derivative, as negative controls for the FimH antagonist. We successfully synthesized the D-glucose derivative to evaluate the selectivity of antagonist binding to the binding site of the FimH. The antagonist was successfully isolated and characterized using appropriate analytical methods, while difficulties were encountered during the isolation of the negative control derivative due to the lability of the silanol protecting groups. The formation of negative control derivative was confirmed by liquid chromatography coupled with mass spectrometry.
Separately, magnetic nanorods were prepared from superparamagnetic iron oxide nanoparticles and stabilized with a silica coating. Their formation and superparamagnetic properties were analyzed by transmission electron microscopy and a vibrating sample magnetometer. Our final compounds were attached to the magnetic nanorods through the chemistry of alkoxysilanes, and the conjugation was verified by measuring zeta potential. As a result, functionalised magnetic nanorods were obtained, to be further tested on Escherichia coli and its biofilms.
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