Abstract
Biofilm formation in microfluidic channels is difficult to detect because sampling volumes are too small for conventional turbidity measurements. To detect biofilm formation, we used an ion-sensitive field-effect transistor (ISFET) measurement system to measure pH changes in small volumes of bacterial suspension. Cells of Micrococcus luteus (M. luteus) were cultured in polystyrene (PS) microtubes and polymethylmethacrylate (PMMA)-based microfluidic channels laminated with polyvinylidene chloride. In microtubes, concentrations of bacteria and pH in the suspension were analyzed by measuring turbidity and using an ISFET sensor, respectively. In microfluidic channels containing 20 μL of bacterial suspension, we measured pH changes using the ISFET sensor and monitored biofilm formation using a microscope. We detected acidification and alkalinization phases of M. luteus from the ISFET sensor signals in both microtubes and microfluidic channels. In the alkalinization phase, after 2 day culture, dense biofilm formation was observed at the bottom of the microfluidic channels. In this study, we used an ISFET sensor to detect biofilm formation in clinical and industrial microfluidic environments by detecting alkalinization of the culture medium.
Highlights
Bacterial biofilm formation often causes serious problems in the dental care field [1], artificial urinary tracts [2], and wastewater treatment systems [3]
We demonstrate that the ion-sensitive field-effect transistor (ISFET) sensor can be applied to detect biofilm formation in microfluidic channels using only 20–30 μL of bacterial suspension
These results indicated that alkalinization occurred after the marked growth of the bacteria and that this phase could be suitable for biofilm detection because the temporal profile of alkalinization was similar to that of biofilm formation
Summary
Bacterial biofilm formation often causes serious problems in the dental care field [1], artificial urinary tracts [2], and wastewater treatment systems [3]. Basic technologies for the detection and control of biofilm formation in food processing plants have been reported [4], the underlying mechanism is not well understood and solutions to these problems are eagerly awaited. Given that bacterial proliferation increases the pH of medium [8], precise measurement of pH changes induced by bacterial proliferation and/or metabolism would contribute to the detection of biofilm formation in microfluidic channels. Using this technology, problems induced by bacterial growth in the channels of artificial urinary tracts and industrial plants can be detected. Because bacterial metabolism produces basic compounds such as urea and arginine, these substances may be indicators of bacterial growth-related problems [9]
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