Peptide Terminated Polymer Brush Nanomaterials for Label-Free Separation of Cancer Cells Based on Relative Adhesion

Separation of cell types from complex tissue-derived populations is a priority goal in biomedical research with direct implications for medical diagnostics and bioprocessing. Dense poly(ethylene glycol) methyl ether methacrylate (PEGMEMA) brush films synthesized by surface-initiated atom transfer radical polymerization yield a linear growth rate of 0.83 nm min^{- 1} and thicknesses up to 120 nm. Quartz crystal microbalance with dissipation monitoring confirms suppression of non-specific protein adsorption from fetal bovine serum. Terminal azide functionalization followed by strain-promoted copper-free click chemistry enables immobilization of linear Arg-Gly-Asp (linRGD) and cyclic (cRGD) peptides at independently tunable densities, a design space of brush thickness, peptide density, and RGD conformation not previously achieved in microfluidics. Integration into polydimethylsiloxane microfluidic channels with a progressive force ramp (0-25 dynes cm^{- 2}) achieves selective displacement of A375 melanoma from A2780 ovarian cancer cells with 88 ± 15% recovery and >93% viability. Differential focal adhesion maturation underlies separation: A375 cells express 29.7% lower α5β1 integrin density and form nascent adhesions retracting at 120 min (actin falls 37%), whereas A2780 cells develop mature focal adhesions with 92% and 125% increases in talin and actin. This platform transduces integrin profiles and cytoskeletal competence into measurable adhesion phenotypes, enabling precise, gentle label-free cell separation.