Filter-based microfluidic device as a platform for immunofluorescent assay of microbial cells

Abstract

A filter-based microfluidic device was combined with immunofluorescent labeling as a platform to rapidly detect microbial cells. The coin-sized device consisted of micro-chambers, micro-channels and filter weirs (gap = 1-2 microm), and was demonstrated to effectively trap and concentrate microbial cells (i.e., Cryptosporidium parvum and Giardia lamblia), which were larger in size than the weir gap. After sample injection, a staining solution containing fluorescently-labeled antibodies was continuously provided into the device (flow rate = 20 microl min(-1)) to flush the microbial cells toward the weirs and to accelerate the fluorescent labeling reaction. Using a staining solution that was 10 to 100 times more dilute than the recommended concentration used in a conventional glass method, those target cells with a fluorescent signal-to-noise ratio of 12 could be microscopically observed at single-cell level within 2 to 5 min prior to secondary washing.

Focusing of sub-micrometer particles and bacteria enabled by two-dimensional acoustophoresis

“…Thus, considerations such as initial sample volume or batch volume are no longer relevant. Previously used methods for handling of sub-micrometer particles included filters, 4,5 dielectrophoresis, [6][7][8] inertia in combination with hydrodynamic forces, 9 magnetophoresis, 10,11 deterministic lateral displacement, 12 and surface acoustic waves (SAW). 13 These methods have been mainly used for handling of bacteria and particles of around 1 μm in diameter.…”

Autonomous microfluidics with stimuli-responsive hydrogels

“…Significant progress has been made to realize a variety of sensors, such as biochemical, 9 fluorescence, 10 flow, 11 temperature, 12 and pressure 13 sensors. Other important elements, such as valves, 14 pumps, 15 mixers, 16 filters, 17 reactors, 18 and heating and cooling elements 19,20 have also been demonstrated. As the microfluidic systems become increasingly complicated to provide more functions, more functional elements need to be integrated on a miniaturized chip.…”

Dean flow-coupled inertial focusing in curved channels

“…In addition, the requirement of external forces, on-chip integration of interfacing components, such as mechanical moving parts, electrodes, or heaters often complicates fabrication procedures and increases the complexity of resulting devices. Passive continuous-flow techniques based on filtering through sieving structures [5][6][7] or by differential interaction of particles with local flow profiles [8][9][10][11] (such as pinch flow fractionation, deterministic lateral displacement) have proven to be relatively simple to operate. However, the need for narrow channel geometries makes these systems less versatile and may lead to channel clogging and particle-particle interactions.…”