Mapping Cell Adhesion Patterns with a Modified DNA Hairpin

Abstract

New contrast methods and sample preparation techniques for microscopy have made it possible to collect quantitative data from images while offering a less invasive and more direct experimental approach. Fluorescence, for instance, takes advantage of the versatility of labeling chemistry and spectral properties of probes to provide spatial and temporal resolution in multiple channels of information. Alternatively, a higher power light source can be introduced to a sample to manipulate molecules mechanically through an anchor. However, while fluorescence can be readily adapted to a system of interest, mechanical measurements often require specialized instrumentation and thus lack the versatility offered by fluorescence microscopy. To bring mechanical detection to a more common microscope platform, we need a contrast scheme that combines mechanical sensitivity with fluorescence imaging. Taking advantage of the well characterized chemical, mechanical, and physical properties of DNA, we previously presented the force-fluorescence relationship for a DNA hairpin. Given the low force of unzipping, 18pN, we expect that the hairpin molecule will be sensitive to molecular-scale mechanical changes. We modified this DNA hairpin by adding a cell adhesion peptide, RGD, to its terminus. Accordingly, we hypothesize that the hairpin can be used to detect cell adhesions to a surface coated with the hairpin molecule. Here, we present steps towards a molecular contrast scheme for imaging patterns of cell-surface adhesions as changes in fluorescence intensity.