Adsorption of microorganisms onto an artificial siderophore-modified Au substrate

The hydroxamate-type artificial siderophore, tris[2-{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.