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Cancer is a major health problem in the United States with extremely high mortality. The detection and isolation of cancer cells are becoming increasingly important for cancer diagnosis. We describe a microfluidic device modified with silica nanoparticles to enhance the isolation of cancer cells using affinity separation. The isolation of seven different cancer cell lines spiked into liquid biopsies was demonstrated and compared with unmodified separation devices. Cancer cells were isolated using CD71 which has already been demonstrated to be a widespread "net" for capturing cancer cells of any phenotype as the affinity target. The capture efficiency of our nanoparticle (NP)-modified HB chip showed significant differences compared with the normal HB chip, exhibiting an average increase of 16%. The cell enrichment increased by a factor of 2 over unmodified chips. Patient-derived ALL cells, COG-LL-332, were spiked into blood with concentrations ranging from 1% to 20% of total leukocytes, and isolated with the purity of 41%-65%. The results of this study demonstrated that the increase of cell-chip interactions after nanoparticle modification improved capture efficiency and capture purity, and can be applied to a wide range of cell separations.

The high purity of target cells enriched from blood samples plays an important role in the clinical detection of diseases. However, non-specific binding of blood cells in the isolated cell samples can complicate downstream molecular and genetic analysis. In this work, we report a simple solution to non-specific binding of blood cells by modifying the surface of microchips with a multilayer nanofilm, with the outmost layer containing both PEG brushes for reducing blood cell adhesion and antibodies for enriching target cells. This layer-by-layer (LbL) polysaccharide nanofilm was modified with neutravindin and then conjugated with a mixture of biotinylated PEG molecules and biotinylated antibodies. Using EpCAM-expressing and HER2-expressing cancer cells in blood as model platforms, we were able to dramatically reduce the non-specific binding of blood cells to approximately 1 cell per mm2 without sacrificing the high capture efficiency of the microchip. To support the rational extension of this approach to other applications for cell isolation and blood cell resistance, we conducted extensive characterization on the nanofilm formation and degradation, antifouling with PEG brushes and introducing functional antibodies. This simple, yet effective, approach can be applied to a variety of microchip applications that require high purity of sample cells containing minimal contamination from blood cells.