(308f) Self-Assembled Protein-Inorganic Hybrid Supraparticles for Robust Protein Immobilization

Biomineralization is a process during which mineral clusters and biomacromoecules self-assemble into nanostructured composite materials. Proteins serve dual roles in these hybrid materials, first as templating agents to regulate structural and physical properties of the material, and second as ligands for biological communication. Inspired by this natural process, we developed a method to fabricate self-assembled and porous hybrid supraparticles with specific affinity recognition for robust protein immobilization. First, we constructed a recombinant fusion protein that contains naturally derived leucine zipper coiled coil motifs, which can enable non-covalent conjugation of proteins via a high affinity interaction between the zippers. In the fusion protein, two identical leucine zipper motifs were combined with a random-coil midblock. Second, the engineered protein directs formation of flower-like nanohybrids that are further self-organized into porous supraparticles. When calcium phosphate was precipitated in the presence of the fusion protein, it provided nucleation sites and directed the growth of calcium phosphate petals into flower-like nanohybrids. The van der Waals interactions between the flower-shaped nanostructures resulted in their colloidal assembly into interlocked chains, which were packed into hierarchically structured and porous supraparticles on the micrometer length scale. The protein-inorganic supraparticles are biocompatible, and provide large surface on which leucine zipper motifs, the high-affinity conjugation sites, are available. Globular proteins fused with the leucine zippers can be immobilized on the supraparticles via simple incubation in aqueous solution. In particular, immobilization of enzymes can enhance their stability and catalytic activity, thus providing benefits for many applications. Thus, our approach provides a versatile method to fabricate complex biomaterials by mimicking both specific biomolecular recognition and the natural biomineralization process for formation of hybrid nanostructures.