AC-Electroosmosis-Assisted Surface Plasmon Resonance Sensing for Enhancing Protein Signals with a Simple Kretschmann Configuration

Abstract

A surface plasmon resonance (SPR) sensor chip fabricated with a comb-shaped microelectrode array to supply alternating current (AC) voltage is reported. The chip induces circulating flow near the surface (i.e., AC electroosmosis). The circulating flow provides a mixing effect, which enhances the binding of the analyte molecules. We evaluated the SPR characteristics of the chip and demonstrated an improvement in protein binding to the chip surface. SPR sensor chips with comb-shaped microelectrodes were fabricated using standard UV lithography. Sensing experiments were conducted using a standard Kretschmann-type SPR measurement system. To demonstrate the mixing effect of AC electroosmosis, we evaluated the binding of immunoglobulin G molecules onto the sensor surface where anti-immunoglobulin G antibodies were covalently immobilized. The result indicates that the amount of binding increases by a factor of 1.7 above that achieved by using a conventional chip, suggesting enhancement of the protein signal.

Rapid fabrication of interdigitated electrodes by laser ablation with application to electrokinetically enhanced surface plasmon resonance imaging

“…9,10 Terao et al recently demonstrated an electrokinetically active SPR sensor for the specific monitoring of molecular interactions, but dedicated the entire sensor surface to one probe and did not extend the technique to multiplexed SPRi. 14 The ability to monitor interactions between immobilized AMPs and bacteria with the patterned IDE array demonstrates the compatibility of this method of fabrication with SPRi sensing.…”

“…32 The choice of 1.54 mmol NaCl as the carrier fluid was four-fold: it permitted a minimum mobile charge carrier density to enable ACEO 32 , to yield pDEP within the desired frequency range, to minimize hypo-osmotic shock to the bacteria, and finally to minimize the oxidation of the gold film as a result of the applied alternating current. 14 SPRi has previously been demonstrated for the specific detection of bacteria using arrays of immobilized antimicrobial peptides. 26 However, the time-to-results with this method was long, taking several hours to reveal interactions between AMPs and challenge bacteria.…”

“…The combination of this amplitude and range of frequencies has been shown in similar conditions not to result in electrochemical oxidation of the electrodes. 14…”

“…9,10 Terao developed this technique for the monitoring of specific interactions between immunoglobulin G (IgG) and sensorimmobilized anti-IgG antibodies. 14 To the authors' knowledge, this work represents the first time that LDW has been used to rapidly fabricate electrodes directly into an SPR sensor; and furthermore, the first time electrokinetic SPR imaging (EK-SPRi) has been demonstrated for parallel, multiplexed sensing with multiple probes of a clinically relevant, antibiotic-resistant strain of Staphylococcus aureus.…”

“…5,[7][8][9]11 Traditionally, fabrication of electrodes necessitates some or all of: deposition of the electrode material and adhesion layers onto a suitable substrate, fabrication of a hard mask, and deposition of photoresist followed by lithography and associated wet or dry etching techniques. [12][13][14][15] Such methods are time-consuming, expensive, and incompatible with rapid iteration of component design, slowing the pace of research and obligating researchers to handle etchant chemicals and perform lengthy lithography processes and other steps which require skills that may be unrelated to their scientific training.…”