Cytophobic surface modification of microfluidic arrays for in situ parallel peptide synthesis and cell adhesion assays

A combination of PEG-based surface passivation techniques and spatially addressable SPPS (solid-phase peptide synthesis) was used to demonstrate a highly specific cell-peptide adhesion assay on a microfluidic platform. The surface of a silicon-glass microchip was modified to form a mixed self-assembled monolayer that presented PEG moieties interspersed with reactive amino terminals. The PEG provided biomolecular inertness and the reactive amino groups were used for consequent peptide synthesis. The cytophobicity of the surface was characterized by on-chip fluorescent binding assays and was found to be resistant to nonspecific attachment of cells and proteins. An integrated system for parallel peptide synthesis on this reactive amino surface was developed using photogenerated acid chemistry and digital microlithography. A constant synthesis efficiency of >98% was observed for up to 7mer peptides. To demonstrate specific cell adhesion on these synthetic peptide arrays, variations of a 7mer cell binding peptide that binds to murine B lymphoma cells were synthesized. Sequence-specific binding was observed on incubation with fluorescently labeled, intact murine B lymphoma cells, and key residues for binding were identified by deletional analysis.