Processing-Dependent Self-Assembly of Protein-Polymer Diblock Copolymers

Self-assembly of globular protein-polymer diblock copolymers is a novel method for nanopatterning protein-based materials which maintains a high fraction of protein activity as well as the folded protein structure. By subjecting these copolymers to different processing conditions, long range ordering and the fraction of active protein can be controlled. Here, self-assembly of model mCherry-b-poly(N-isopropyl acrylamide) (PNIPAM) block copolymers is induced by water evaporation from dilute aqueous solutions of conjugate material, and followed by solvent annealing of the resulting nanostructures. Different pathways towards self-assembly are accessed by orthogonally manipulating the solvent quality for each block of the copolymer using temperature and pH. Small-angle scattering and transmission electron microscopy show nanostructure depends heavily on PNIPAM coil fraction and solvent annealing condition, with solution self-assembly reflected in the solid state structure under certain conditions. Protein structure is unaffected by the processing pathway, while protein activity levels in the nanodomains depend strongly on processing conditions and can retain up to 80\% of the initial activity.