Passive fluid transport by cryogel filled capillaries for the realization of POC assays

Abstract:
Over the past years, point-of-care testing (POCT) gained increasingly importance in medical diagnostics. Paper (nitrocellulose) based lateral flow tests which are the standard in POCT, have some limitations due to their nitrocellulose membrane which e.g. causes non-specific protein adsorption and has unfavorable optical properties which lead to a reduced assay sensitivity. To address those limitations, a microfluidic platform which could be used to realize immunochromatographic assays for point-of-care testing is investigated. The platform is made of a transparent capillary filled with cryogel compartments. For their generation, solutions containing a photo-copolymer and biomolecules e.g. biotin, of interest are sucked into the capillary separated by air plugs to avoid mixing. After freezing the solutions within the capillary, through a photo-induced cross-linking process the solutions are transformed into spongelike cryogel compartments which are covalently attached at the capillary walls. After preparation, the surface attached gel compartments are dried and used in assays. We demonstrate that the platform was successfully used for the detection of a model assay based on biotin-streptavidin interactions.