Microfluidics-Based Assay On The Effects Of Microenvironmental Geometry And Aqueous Flow On Bacterial Adhesion Behaviors

As a general phenomenon, bacterial adhesion to surfaces often occurs in aqueous flow such as river beds, hulls and water pipes. It often causes bacterial infections, bacterial corrosions and biofilms, which are greatly harmful in human. For the prevention of bacterial adhesion, a great many of studies have been performed in microbiology and medicine. In bacterial adhesion experiments, parallel plate flow chamber systems have been used as a conventional implement. But their defections (e.g. To change their structures is difficult.) limit the development of bacterial adhesion. Recent years, a new flow system, microfluidic flow chambers have been used in bacterial adhesion studies. The new system has many advantages over conventional parallel flow chambers, including control of structures, more accurate control of fluid kinetic and low reagent volume requirements. These advantages ensure microfluidic flow chamber systems can achieve progresses which have were not accomplished by conventional equipments.In this study, a one-layer microfluidic flow chamber system for bacterial adhesion assay is presented. The chip that contains 16 symmetrical channels with four geometrical chambers (Circle and Concave polygons with 4, 6 and 8 angles) is used to demonstrate the factors affecting bacterial adhesion to surfaces: cultural time, flow rate and geometry of flow chambers. A bacteria strain E. coli, pGLO which can produce green fluorescence protein is prepared to perform the observation and analysis of adhesion. And a numerical simulation by software CFD-ACE+ is used to explain the results. As our main novelty, the influence of geometry on bacteria adhesion has not been performed due to the limit of conventional equipments until now.The main results of this study include:(1) A bacterial strain which could stably generated fluorescence induced by L-Arabinose, was made by electrotransformation. A one-layer microfluidc flow chamber chip was fabricated use soft lithography with PDMS. Numerical simulation of flow in this chip was performed by software CFD-ACE+. (2) The bacterial adhesion changed with cultural time was demonstrated: initially, the bacterial adhesion occurred at the microchamber sides, and then covered the entire chamber as times go on.(3) The arrangement of bacterial adhesion changed with flow rates was observed: at low flow rates, the orientation of adhered bacteria was random and disorderly. When the flow increased, the orientation became close to the streamline and was influenced by the chamber side.。(4) The difference of bacterial adhesion among different zones of the chambers was analyzed: The densities of adherent bacteria were higher in substratum far away from the chamber side than in substratum near the chamber side.(5) The influence of geometry of flow environment on bacterial adhesion was discovered and demonstrated: the densities of adhered bacteria increased with the complexities of the chambers.The results give the prevention of bacteria an important cue: simple structure in flow supplement could reduce bacterial adhesion. The microfluidic flow chamber chip fabricated also provided a new platform to study the effects of geometry of flow environment on bacteria behaviors.