Enhancement of biomolecule binding on biosensors using AC electrokinetics

Abstract

The goal of this research was to investigate AC Electrokinetic forces with the purpose of using them to improve protein binding onto the surfaces of biosensors. Biomolecules typically diffuse slowly and react quickly to biosensor surfaces. This leads to transport limitations of analyte to the transducer surface and results in long detection times. Microscale electrodes supplied with an AC field can generate forces, known as AC electrokinetics, that act on particles submerged within a liquid or that operates on the fluid itself. Using these phenomena, the transport limitations can be alleviated by advective mixing or by concentrating local particles. Though there are several important phenomena that contribute to the overall behavior of particles and fluids, current predictive techniques consider special conditions where only a single phenomenon may be considered. A finite element model was therefore developed to predict more general conditions where the various AC electrokinetic forces coexist and to understand how these forces affect protein binding onto a surface. The simulation predictions were corroborated with experimental observations of collected microparticles as well as fluorescent protein adsorption assays. Design and operational parameters that affect protein binding were investigated using these means. The simulations indicated that binding times can be reduced by up to a factor of 6. Fluorescent intensity of the protein assays indicated an enhancement of about 1.9 times at the center of the device and 6.7 times at the edges of the best device type. Finally, the development of a hybrid sensor-actuator was constructed by fabricating interdigitated electrodes capable of generating AC Electrokinetics onto the surface of a quartz crystal microbalance. Directly adsorbed antibodies were bound to the surface of this new device using AC electrokinetics and the signal was consequently enhanced by a factor of about 5.6 for a 15 minute reaction. Modification of the QCM resulted in little reduction of quality factor and an increased sensitivity to viscosity changes This research is expected to help translate biosensors and microfluidic devices that have applications in point-of-care diagnostics, environmental monitoring and counterterrorism.%%%%Ph.D., Biomedical Engineering – Drexel University, 2010