Enrichment of viable bacteria in a micro-volume by free-flow electrophoresis

Abstract

Macro- to micro-volume concentration of viable bacteria is performed in a microfluidic chip. The enrichment principle is based on free flow electrophoresis and is demonstrated for Gram positive bacteria. Bacteria from a suspension flow are trapped on a gel interface that separates the trapping location from integrated actuation electrodes in order to enable non-destructive trapping. The microfluidic chip contains integrated electrolytic gas expulsion structures and phaseguides for gel and liquid handling. Trapping efficiency is systematically optimized to reach 25 times the initial concentration from a theoretical maximum of 30. Finally, enrichment from analytically relevant concentrations down to 3 × 10(2) colony forming units per millilitre is demonstrated with a trapping efficiency of 80% which represents the most important parameter in enrichment.

Microfluidic concentration of bacteria by on-chip electrophoresis

“…Compared with previously used gram positive bacteria, E. coli are far more sensitive to lysis. 40 Furthermore, Fig. 5 shows a significant decrease of viable cells in TBE between 30 min and 60 min, whereas the cell number in SB medium almost remains constant within this time frame.…”

“…Therefore, in addition to previous results, 40 three concentration experiments of E.coli XL1-blue at 15 ll/min without HPMC were performed and showed an capture efficiency of 87.29 6 6.95%. In contrast, in experiments with 0.1% HPMC and the same species the efficiency was 98.39 6 1.02% as summarized in Table I.…”

“…Besides the throughput also the capture efficiency was still unsatisfyingly at around 80%. 40 In this contribution, we analyze the influencing factors and present an optimized device and method for concentration of bacteria by means of FFE. A highly efficient but gentle concentration of gram negative bacteria, which are far more sensitive to lysis is demonstrated.…”

In-Situ Electrophoretic Mobility Determination by Particle Image Velocimetry for Efficient Microfluidic Enrichment of Bacteria

“…Environmental samples often contain low amounts of bacteria as well as substances that inhibit PCR, necessitating preprocessing of the raw sample. In former work, both the enrichment of bacteria from suspension as well as size-selective purification of target nucleic acids on microfluidic platforms have been demonstrated [1,2].…”

Enrichment of diluted cell populations from large sample volumes using 3D carbon-electrode dielectrophoresis

“…Sample volume was only 400 ll and was processed at 200 ll/min. Free flow zone electrophoresis (FFE) was also used as an enrichment technique 17,18 by exploiting the charge distribution on the surface of the cells. For example, Podszun and colleagues processed a 100 ll-volume of a laboratory sample featuring E. faecalis at concentration as low as 266 6 35 cells/ml to obtain a maximum enrichment factor of 11 when sample was processed at 3 ll/min.…”