Micro- and macro-flow systems to study Escherichia coli adhesion to biomedical materials

Micro- and macro-flow systems have been used as in vitro platforms to study bacterial adhesion under physiological conditions. The decision of which platform to use has been dictated by the dimensions of the in vivo systems that they are supposed to mimic and by the available resources in each laboratory. In this work, a microchannel and a parallel plate flow chamber were operated in order to observe the adhesion of Escherichia coli to different materials that are commonly used to construct biomedical devices for the urinary and reproductive systems. The surface properties of cellulose acetate, glass, poly-l-lactide, and polydimethylsiloxane were thermodynamically characterized by contact angle measurement and the flow along the platforms was simulated by computational fluid dynamics. The results presented in this study demonstrate that different adhesion rates were obtained on different materials but similar values were obtained in the micro- and macro-platforms for each material under the same shear stress (0.022 Pa). This suggests that despite the scale factor (80×) both platforms may be equally used to mimic the same biomedical biofilms for a specified shear stress. Thus, depending on the expertise and equipment availability in different labs, micro-flow systems can be used taking advantage of lower hold-up volumes or macro-flow systems can be selected in order to obtain a higher biofilm mass which can be used for further biochemical analysis.