Proteins grouped into a variety of regular micro-patterns by substrate-guided domains of self-assembling poly(ethylene oxide)/polystyrene blends

Abstract

Spin-casting of polymer blends provides one-step deposition and self-assembly of domains with contrasting surface properties. Resulting irregular structures are commonly used to guide protein adsorption and cell seeding. However, a more regular arrangement of biological material is required for more advanced biomedical applications. In this report, blends of poly(ethylene oxide) (PEO) and polystyrene (PS) (1 : 1 and 1 : 2 w/w) admixed with pentaerythritol triacrylate spin-cast (with inherent domain scale 1.6 ≤ 2R ≤ 4.0 μm) onto gold, micro-contact printed with hexadecanethiol (SAM) stripes (with periodicity λ = 4 and 8 μm), and cross-linked with ultraviolet are used as adsorption templates to group fluorescently labelled concanavalin A (ConA) into periodic protein micro-patterns with different morphologies depending on the 2R/λ ratio: strings of islands (2R/λ ≈ 0.2), branched stripes (∼0.33), stripe pairs (∼0.5) and stripes (∼1). Hierarchical (for 2R/λ < 1) protein micro-patterns reflect the phase rich in PS, assembled during spin-casting into domains elevated above the neighbouring PEO-rich phase on Au regions, and covered by the PEO-rich lamella with intermediate height on periodically repeated SAM areas. The relation between long-ranged regular ordering of blend films (adsorption templates), visualized with atomic force microscopy, and micro-patterns (grouped proteins), revealed with fluorescence microscopy, is examined with Fourier analysis.