Radio Frequency Tank Circuit for Probing Planar Lipid Bilayers

Abstract

We present first results from a hybrid coplanar waveguide microfluidic tank circuit for monitoring lipid bilayer formation and fluctuations of integrated proteins. The coplanar waveguide is a radio frequency resonator operating at ~250 MHz. Changes within the integrated microfluidic chamber, such as vesicle bursting and subsequent nanopore formation alter the reflected signal, and can be detected with nanosecond resolution. We show experimental evidence of such alterations when the microfluidic channel is filled with giant unilamellar vesicles (GUVs). Subsequent settling and bursting of the GUVs form planar lipid bilayers, yielding a detectable change in the resonant frequency of the device. Results from finite element simulations of our device correlate well with our experimental evidence. These simulations also indicate that nanopore formation within the bilayer is easily detectable. The simulated structure allows for incorporation of microfluidics as well as simultaneous RF and DC recordings. The technique holds promise for high throughput drug screening applications and could also be used as an in-plane probe for various other applications. It opens up possibilities of exploring ion channels and other nano scale pores in a whole new frequency band allowing for operating at bandwidths well above the traditional DC methods.

Label-free single-cell counting and characterization in the GHz-range

“…Based on recent progress in micro-electronic andfluidic device technology [19][20][21], in conjunction with RF-circuits [22][23][24][25] dielectric spectroscopy now holds huge potential as a noninvasive and label free characterization method for single cells [26,27]. An advanced approach based on tubular CPWs (T-CPWs), was demonstrated by Bausch et al Here, the tubular CPW was employed for T cell counting, enabling enhanced detection sensitivity in the radio-frequency range at 177 MHz [28].…”

Radio-frequency response of single pores and artificial ion channels

“…The aperture is fabricated in such a way that phospholipid bilayers can be spanned. The micro-strip line geometry is shown in an aerial view in figure 2(c), which is used as the basis for finite-element simulations of this particular TL [12]. The central area marked by gray boxes indicates the region where the on-chip unit is positioned.…”

Tank Circuit for Ultrafast Single-Particle Detection in Micropores

“…Our prior experiments have demonstrated that resolving the translocation of single molecules through an α-hemolysin pore tracing the RF-response is indeed feasible [10]. The necessary next step is to place such a setup in a planar fashion with an increased sensitivity, which we have recently reported on by using a coplanar waveguide (CPW) for tracing the formation of lipid bilayers in the frequency domain [11]. In this letter we bring these first results to fruition by an enhanced CPW tank circuit design, which resolves sub-micron particle translocations with BWs greater than 30 MHz.…”