Continuous concentration of bacteria in a microfluidic flow cell using electrokinetic techniques

Abstract

A novel method for the concentration of bacterial solutions is presented that implements electrokinetic techniques, zone electrophoresis (ZE) and isoelectric focusing (IEF), in a microfluidic device. The method requires low power (< 3e-5 W) and can be performed continuously on a flowing stream. The device consists of two palladium electrodes held in a flow cell constructed from layers of polymeric film held together by a pressure-sensitive adhesive. Both ZE and IEF are performed with carrier-free solutions in devices in which the electrodes are in intimate contact with the sample fluid. IEF experiments were performed using natural pH gradients; no carrier ampholyte solution was required. Experiments performed in buffer alone resulted in significant electroosmotic flow. Pretreatment of the sample chamber with bleach followed by a concentrated solution of cationic detergent effectively suppressed electroosmotic flow.

Biomolecular gradients in cell culture systems

“…11) which consist of two or more microchannels that join into a single microchannel in a T-shaped configuration. T-sensor-based devices have been used to combine dissimilar fluid streams to create combinatorial mixtures of different chemicals, 112 perform biological assays, 110,111,114,115 study bacterial chemotaxis, 118 and infect cells with different viral titrations. 84 T-sensor-based devices generate steady-state gradients that are reproducible and can be characterized quantitatively.…”

Manipulation of bacteriophages with dielectrophoresis on carbon nanofiber nanoelectrode arrays

“…The development of microdevices for the on-chip capture, sorting, and concentration of microbes is critical for developing rapid pathogen detection technologies based on microfluidics [1,2] and other miniaturized biosensor chips [3,4]. Dielectrophoresis (DEP) is one of the most effective techniques for interacting with any polarizable particle using easily generated electric fields [5,6].…”

“…In most studies, an alternating current (AC) voltage is applied to a pair of electrodes to generate the electric field. The time averaged DEP force (F DEP ) exerted on a spherical particle is given by [6]: (1) where r is the radius of the particle, ε m is the absolute permittivity of the suspending medium, ∇E 2 is the gradient of the square of the applied electric field strength, and Re[K(ω)] is the real component of the complex Clausius-Mossotti (CM) factor given by [6]: (2) with ε * representing the complex permittivity and the indices p and m referring to the particle and medium respectively. σ is the conductivity, ω is the angular frequency (ω = 2πf) of the applied electric field, and j = √-1.…”

Integrated microfluidic preconcentrator and immunobiosensor

“…A number of preconcentration techniques have been developed that can achieve high concentration factors in small time durations. Some examples include surfacebinding techniques like solid-phase extraction (Jemere et al 2002;Ramsey and Collins 2005;Yu et al 2001) and electrokinetic manipulation techniques like isoelectric focusing (Li et al 2003;Tan et al 2002;Cabrera and Yager 2001), field-amplified sample stacking (Jung et al 2003;Lichtenberg et al 2001), isotachophoresis (Jung et al 2006;Wainright et al 2002;Wang et al 2009), and dielectrophoresis (Lapizco-Encinas et al 2005;Moncada-Hernandez and Lapizco-Encinas 2010). However, the limitations of these techniques are that they either involve buffer handling challenges or fabrication complexities making them difficult to integrate with lab-on-chip systems.…”