Construction of binary protein superlattices composed of inorganic nanoparticles and fluorophores

Abstract

Protein containers have gained interest as building blocks for the assembly of novel biohybrid materials. The cargo loading as well as the assembly of the protein containers can be altered, resulting in various materials with novel emerging properties. Highly ordered assemblies can easily be achieved with protein containers, overcoming major challenges in nanoparticle assemblies. Nanoscale biohybrid materials based on nanoparticle loaded protein containers are created by an innovative design approach with oppositely charged protein containers as building blocks. In this work, crystallization conditions for novel supercharged protein containers were screened and optimized. Depending on the protein variant and crystallization condition, different assemblies were found and discussed within this work. Moreover, the influence of temperature on the crystallization was observed. Protein containers were loaded with nanoparticles via dis- and reassembly approach. Gold nanoparticle loaded proteins were crystallized towards biocompatible substrates for future applications such as surface enhanced Raman scattering. Protein containers of different sizes were assembled into novel hetero binary structures. Both containers were loaded with nanoparticles, resulting in densely packed nanoparticle superlattices. The nanoparticle superlattices might give access to future applications in traceable catalysis or magneto-plasmonics. Moreover, new approaches for structure determination based on nanoparticle superlattices were applied on protein-based assemblies. In cases, where the resolution of a protein crystal from X-ray diffraction experiments was not sufficient, diffraction of the nanoparticle superlattices could be investigated. In addition, highly efficient fluorophore labeling of protein containers was achieved. Fluorescent protein containers were used as a novel building block for the assembly of fluorescent protein crystals. In the end, interactions between gold nanoparticles and fluorophores were investigated in confocal microscopy.