Biosensing in microfluidic channels using fluorescence polarization

Abstract

Microfabricated microfluidic devices provide useful platforms for sensing and conducting immunoassays for high throughput screening and drug discovery. In this paper, fluorescence polarization (FP) has been used as a technique for probing binding events within 500 μm and smaller microfluidic channels fabricated in polydimethylsiloxane. The binding of concanavalin A to a lectin-dextran and a glycoprotein-acetylcholinesterase has been used to demonstrate the homogeneous, ratioing format of fluorescence polarization for the quick and accurate determination of extremely low concentrations. Concentrations of concanavalin A in the 0.2–1.0 nmole range were detected within 500 μm channels. Polarization has also been used to sense for a polyaromatic hydrocarbon (PAH) within a microfluidic channel using binding to a TRITC-labeled antibody. Specifically, concentrations of pyrene in a 10–40 nmole range were sensed in 500 μm microfluidic channels. We have also demonstrated a simple pH sensor based on the change in anisotropy of a pH sensitive fluorophore-SNAFL. The ease of fabrication and measurement using such polarization-based devices make them extremely suitable for micro-sized sensors, assays and total analysis systems.