(381g) Selective Biomolecular Detection Using Interfacial Electrokinetic Transduction (IET) Biosensors

Biosensors are analytical devices that combine biological sensing elements with physicochemical transducers to detect and quantify biomolecular interactions. Development of portable sensors capable of rapidly detecting specific biomolecules is of central importance for the diagnosis and treatment of disease, biowarfare/anti-terrorism applications, environmental monitoring, drug discovery, cell biology, cancer research and point-of-care diagnostic testing. The combination of biosensors with microfluidics has potential to fulfill the need for cheap, portable sensors capable of rapid and sensitive detection, as they are amenable to miniaturization, automation and integration. In this work we report the first label-free biosensor for detecting and monitoring bioaffinity interactions in solution at microfluidic liquid interfaces. The approach is based on a novel electrical method that combines continuous flow microfluidics with alternating current (AC) electrokinetics. Bioaffinity binding is initiated at a microfluidic laminar liquid interface. Simultaneously, an AC electrical field is applied to electrokinetically displace the interface across the main flow channel. The magnitude and direction of the interfacial displacement is a function of the applied frequency and the interface electrical properties. We demonstrate that interfacial frequency response is influenced by biomolecular binding. Biosensor detection is based on interfacial electrokinetic transduction (IET); binding changes the electrical properties of the fluid interface, which is electrokinetically transduced, and detected by monitoring the frequency response of the liquid interface. In this manner, the liquid interface serves as both the substrate for specific binding and the transducer for biomolecular recognition. We use IET to electrokinetically detect avidin in solution without labels. The IET biosensor is specific and able to distinguish low concentrations of avidin against a background of bovine serum albumin (BSA). Through this study, we establish a methodology for rapid label-free IET biosensing at electrical liquid interfaces, and demonstrate sensor performance and sensitivity for the detection of biomolecules at low picomolar concentrations. This new electrokinetic approach could provide a low-cost, rapid, and portable biosensing strategy for biomolecular diagnostics.