Adsorption of microorganisms onto an artificial siderophore-modified Au substrate

The hydroxamate-type artificial siderophore, tris2-{3-(N-acetyl-N-hydroxamino)propylamido}propyl]aminomethane (TAPPA) and its Fe(III) complex, Fe(III)-TAPPA were prepared and characterized by several spectroscopic methods. Fe(III)-TAPPA exhibits biological activity for the hydroxamate-type siderophore auxotrophic microorganism, Microbacterium flavescens, suggesting that Fe(III)-TAPPA can permeate the cell membrane of the microorganism. The adsorption of the Fe(III)-siderophore complex onto a deposited Au substrate was achieved by a stepwise self-assembling method. The modification of Fe(III)-TAPPA on the surface was confirmed from the cyclic voltammogram of the resultant Au electrode, Fe(III)-TAPPA/Au. The adsorption experiments of M. flavescens with Fe(III)-TAPPA/Au were monitored by optical, scanning electron, and atomic force microscopy and quartz crystal microbalance (QCM) measurements. These results clearly indicate that Fe(III)-TAPPA/Au can immobilize M. flavescens. This adsorption characteristic is due to the interaction between Fe(III)-TAPPA on an Au electrode and a receptor/binding protein within the cell membrane.