[Microorganism Immobilization Device Using Artificial Siderophores]

Inspired by the mechanism by which microorganisms utilize siderophores to ingest iron, four different Fe^III complexes of typical artificial siderophore ligands containing catecholate and/or hydroxamate groups, K₃[Fe^III-L_C3], K₂[Fe^III-L_C2H1], K[Fe^III-L_C1H2], and [Fe^III-L_H3], were prepared. They were modified on an Au substrate surface (Fe-L/Au) and applied as microorganism immobilization devices for fast, sensitive, selective detection of microorganisms, where H₆L_C3, H₅L_C2H1, H₄L_C1H2, and H₃L_H3 denote the tri-catecholate, biscatecholate-monohydroxamate, monocatecholate-bishydroxamate, and tri-hydroxamate type of artificial siderophores, respectively. Their adsorption properties for the several microorganisms were investigated using scanning electron microscopy (SEM), quartz crystal microbalance (QCM), and electric impedance spectroscopy (EIS) methods. The artificial siderophore-iron complexes modified on the Au substrates Fe-L_C3/Au, Fe-L_C2H1/Au, Fe-L_C1H2/Au, and Fe-L_H3/Au showed specific microorganism immobilization behavior with selectivity based on the structure of the artificial siderophores. Their specificities corresponded well with the structural characteristics of natural siderophores that microorganisms release from the cell and/or use to take up an iron. These findings suggest that release and uptake are achieved through specific interactions between the artificial siderophore-Fe^III complexes and receptors on the cell surfaces of microorganisms. This study revealed that Fe-L/Au systems have specific potential to serve as effective immobilization probes of microorganisms for rapid, selective detection and identification of a variety of microorganisms.