Amplified Micromagnetic Field Gradients Enable High-Resolution Profiling of Rare Cell Subpopulations.

Analyzing small collections of cells is challenging because of the need for extremely high levels of sensitivity. We recently reported a new approach, termed magnetic ranking cytometry (MagRC), to profile nanoparticle-labeled cells. Using antibody-functionalized magnetic nanoparticles, we label cells so that each cell's magnetization is proportional to its surface expression of a selected biomarker. Using a microfluidic device that sorts the cells into 100 different zones based on magnetic labeling levels, we generate profiles that report on the level and distribution of surface expression in small collections of cells. Here, we present a new set of studies investigating in depth parameters such as flow rate and magnetic nanoparticle size that affect device performance using both experiments and modeling. We present a model that further elucidates the mechanism of cell capture and use it to optimize device performance to efficiently capture rare cells. We show that this method has excellent specificity and can be used to characterize rare cells even in the presence of whole blood.