2007 NSTI Nanotechnology Conference and Trade Show - Nanotech 2007 - 10th Annual

Quantitative measurements of the strength of adhesion of human neutrophils to a substratum in a microfludic device: A novel inflammation diagnostic tool

E. Gutierrez and A. Groisman
University of California, San Diego, US

Keywords:
neutrophils, shear stress, microfluidic, inflammation, fMLP, fibrinogen

Abstract:
We describe a quantitative assay of the strength of adhesion of activated and non-activated human neutrophils to a substratum, which is carried out in a custom-made microfluidic device. The strength of adhesion is quantified by the fraction of cells remaining adherent (ACF) after a given time of exposure to shear stress in a test microchannel. The microfluidic device is made of two layers of polydimethylsiloxane (PDMS) with integrated membrane valves. This construction allows concurrent testing of two different populations of cells, as well as setting well-defined times of exposure of cells to stress and of their incubation prior to the exposure. The test microchannels have a tapered profile, exposing cells to nearly an order-of-magnitude range of shear stress. ACF is measured periodically by video-microscopy scans of the device, with up to 60,000 individual cells identified within a 90 sec scan. The high throughput of the scans allows reliable quantitative assessment of the ACF. Adhesion of untreated neutrophils and neutrophils activated with fMLP (formyl-Met-Leu-Phe) was tested concurrently in a series of experiments with a fibrinogen-coated glass substratum. At optimized testing conditions, the ACF of activated cells was consistently found to be three times higher than that of non-activated cells. The proposed device and assay could be used to assess the state of activation of neutrophils in human blood with a potential application to diagnostics of inflammation.

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