Filter Method for Separating Unbound Ferrofluid from Target-bound Ferrofluid in a Biological Sample

摘要

A filtering system for separating unbound ferrofluid from bound ferrofluid in the enrichment of a target entity in a biological sample. The filtering device of the present invention has application in the isolation target cells from unbound ferrofluid during separation with a permanent magnet (floater) mechanism. This process reduces interference of unbound ferrofluid during subsequent image analysis or enumeration of cells by image cytometry. The system has application in the assessment of target populations such as leukocyte subsets in different bodily fluids or bacterial contamination in environmental samples, food products and bodily fluids. Briefly, fluorescently labeled target cells are linked to magnetic particles or beads. The linkage process results in a mixture having a population of contaminating unbound magnetic particles. In one embodiment for separation, a small, permanent magnet is inserted directly into the chamber containing the labeled cells. The magnets are coated with PDMS silicone rubber to provide a smooth and even surface which allows imaging on a single focal plane. A filter is positioned on a cover of the floater device to allow unbound ferrofluid to pass through the pores, but restrict the passage of the target entity. The floater and filter are removed from the sample and the filter surface is illuminated with fluorescent light emitted by the target cells captured by a CCD camera. Image analysis can be performed with a novel algorithm to provide a count of the cells on the surface, reflecting the target cell concentration of the original sample.