Sinéad M. Matthews

The application of frequency-domain Fluorescence Lifetime Imaging Microscopy as a quantitative analytical tool for microfluidic devices

We describe the application of wide-field frequency domain Fluorescence Lifetime Imaging Microscopy (FLIM) to imaging in microfluidic devices. FLIM is performed using low cost, intensity modulated Light Emitting Diodes (LEDs) for illumination. The use of lifetime imaging for quantitative analysis within such devices is demonstrated by mapping the molecular diffusion of iodide ions across a microchannel.

Refolding of a membrane protein in a microfluidics reactor

Membrane protein production for structural studies is often hindered by the formation of non-specific aggregates from which the protein has to be denatured and then refolded to a functional state. We developed a new approach, which uses microfluidics channels, to refold protein correctly in quantities sufficient for structural studies. Green fluorescent protein (GFP), a soluble protein, and bacteriorhodopsin (BR), a transmembrane protein, were used to demonstrate the efficiency of the process. Urea-denatured GFP refolded as the urea diffused away from the protein, forming in the channel a uniform fluorescent band when observed by confocal microscopy. Sodium dodecyl sulphate-denatured BR refolded within the channel on mixing with detergent–lipid mixed micelles. The refolding, monitored by absorbance spectroscopy, was found to be flow rate dependent. This potential of microfluidic reactors for screening protein-folding conditions and producing protein would be particularly amenable for high-throughput applications required in structural genomics.

Integration of enzyme immobilised single-walled carbon nanotube arrays into microfluidic devices for glucose detection

Microfluidic devices for glucose detection have been constructed and developed by integration of glucose oxidase covalently immobilised single-walled carbon nanotube arrays into a poly (dimethylsiloxane)-based microfluidic channel. This microfluidic device was tested for electrochemical glucose detection, and the results showed that the glucose can be detected with a linear response up to a concentration of 5times10-3 mol L-1. Because of the small amounts of fluids and enzyme used in microchannels, this approach offers a number of technical advantages, such as portability, shorter analysis time and lower consumption of expensive analytes.