Comparison of Versatile Immobilization Methods for Gram-Positive Bacteria on a Silicon Cantilever

Force spectroscopy and especially single cell force spectroscopy with bacterial probes provide a powerful tool for the investigation of bacterial adhesion to different surfaces. Thereby, a crucial step is the immobilization of the bacteria on the cantilever. Until today, there have been developed versatile methods to attach bacteria to a cantilever, but only few studies compare these methods in a quantitative way. In this work, different functionalizations of the cantilever as well as two picking-up parameters for three gram-positive bacteria are evaluated. While there is no functionalization which works best for all of the bacteria, polydopamine, the adhesive protein Cell-Tak^TM and a gas phase silanization in combination with an activation of the bacteria are the most promising candidates. Further, some general trends how the two investigated picking-up parameters influence the adhesive behavior of the bacteria on the cantilever, which also depends strongly on the shape of the bacteria are presented.