Screening cell surface receptors using micromosaic immunoassays

Abstract

This report presents a general method for screening cell surface receptors using so-called micromosaic immunoassays. This method employs a microfluidic chip having n (n = 11) independent flow paths to move cells over m (m = 11) lines of surface-patterned antibodies for screening individual cells in a parallel, combinatorial, fast and flexible manner. The antibodies are patterned as 30-μm-wide lines on a poly(dimethylsiloxane) layer used to seal the area of the chip in which screening is being monitored. Mouse hybridoma cells having CD44 cell surface receptors and anti-CD44 antibodies were used to establish a proof-of-concept for this method. Both the capture antibodies and the cells were fluorescently labelled to allow the position of the cells to be accurately tracked over the binding sites using an inverted fluorescence microscope. The chips and cells were maintained at a constant temperature between 20 to 37°C, and flow velocities of the cells over the capture areas were 100–280 μm~s⁻¹, resulting in a ∼0.1–0.3 s residency time of the cells on each of the eleven 30 × 30 μm s2 capture areas. Binding of the cells appeared to be specific to the capture areas, with a yield of 30% when the assay was performed at a temperature of 37°C and with a slow flow velocity. We suggest that this proof-of-concept is broadly applicable to the screening of cells for medical/diagnostic purposes as well as for basic research on the interaction of cells with surfaces.