β-CD-Functionalized Microdevice for Rapid Capture and Release of Bacteria

Most procedures for detecting pathogens in liquid media require an initial concentration step. In this regard, carbohydrates have proven to be attractive affinity ligands for the solid-phase capture of bacteria that use lectins for adhesion to host cell membranes. However, the use of cyclodextrin-immobilized substrates to selectively trap bacteria has not been explored before. Here, using quartz-crystal microbalance with dissipation monitoring experiments, we demonstrate that functionalization of surfaces by β-cyclodextrin (β-CD) can not only allow for rapid and efficient capture of bacterial cells in liquid but also their facile elution with an aqueous solution of a selectively methylated β-CD derivative as a competitive molecule. This capture/elution strategy, which is based on host–guest interactions between membrane components of the bacterial cell and the CD cavities, is performed in physiological conditions and can be integrated in a microchip. Indeed, proof-of-concept studies showed the potential of β-CD-modified micropillar-integrated microfluidic devices for concentration of bacteria. The results obtained with Escherichia coli suggest that this approach could be broadly applicable among Gram-negative bacteria, which share common cell membrane structures.