Electrokinetic Formation of “Microbridges” for Protein Biomarkers as Sensors

Abstract

We demonstrate a technique to detect protein biomarkers contained in vulnerable coronary plaque using a platform-based microelectrode array (MEA). The detection scheme is based on the property of high specificity binding between antibody and antigen similar to most immunoassay techniques. Rapid clinical diagnosis can be achieved by detecting the amount of protein in blood by analyzing the protein's electrical signature. Polystyrene beads which act as transportation agents for the immobile proteins (antigen) are electrically aligned by application of homogenous electric fields. The principle of electrophoresis is used to produce calculated electrokinetic movement among the anti-C-reactive protein (CRP), or in other words antibody funtionalized polystyrene beads. The electrophoretic movement of antibody-functionalized polystyrene beads results in the formation of “Microbridges” between the two electrodes of interest which aid in the amplification of the antigen—antibody binding event. Sensitive electrical equipment is used for capturing the amplified signal from the “Microbridge” which essentially behaves as a conducting path between the two electrodes. The technique circumvents the disadvantages of conventional protein detection methods by being rapid, noninvasive, label-free, repeatable, and inexpensive. The same principle of detection can be applied for any receptor—ligand-based system because the technique is based only on the volume of the analyte of interest. Detection of the inflammatory coronary disease biomarker CRP is achieved at concentration levels spanning over the lower microgram/milliliter to higher order nanogram/milliliter ranges.

Patterned Polymer Nanofibers Based Biosensors

“…A planar microelectrode array (MEA) with four gold electrode arms was fabricated on a 1x1 in 2 silicon chip using standard photolithography techniques [1]. The arms had a base width of 250 m and tapered to a tip width of 50 m, and were patterned to face each other at the sensing site.…”

“…Polystyrene microbeads offer ample surface area, and are easily used to conduct biofunctionalization procedures [3]. Reports suggest that polystyrene microbeads can be employed as carriers for the nanoscale proteins, enabling protein detection in immunosensor applications [1]. However, polystyrene nanofibers further improve detection by enhancement of the measured signal strength, due to the greater surface area to volume ratio than microbeads.…”

Nanostructured surfaces for enhanced protein detection toward clinical diagnostics

“…Electrochemical label-free immunoassay detection technologies or immunosensors are portable, hand-held sensor devices that present a promising alternative to their contemporary labeled counterparts. 8,9 Electrical detection methods greatly simplify traditional immunoassay techniques by making the device more cost-effective, through miniaturization and automation. We present here an affinity ligand-based biosensor device that couples immunochemical reactions to capture electronics via sensitive transducers on a polystyrene (PS) platform.…”

“…11 Reports suggest that PS microbeads can be employed as microscopic carriers for the nanoscale proteins for electrical detection for immunosensor applications. 8 However, the microtextured surface generated via the assembly of the PS microbeads does not enhance the detected signal strength as compared with detection from microscale gold electrodes. In comparison, PS nanofibers demonstrate an enhancement in the measured signal strength, because they present a much higher surface-to-volume ratio than microbeads, thereby increasing the immobilization locations for the protein biomolecules and hence increasing the chemoelectronic transduction along the nanotextured surface.…”

“…8 The MEA of 1 inch × 1 inch lateral dimensions consisted of four gold stepwise tapering metallic arms, each ending with a 50-μm tip and patterned to face each other centrally at the sensing site. The tapered electrode has a base width of 250 μm and tapers to a tip width of 50 μm.…”