Exploiting the Interactions of Solid Binding Proteins with Silica to form Colloidal Assemblies

Abstract

Solid binding peptides (SBPs) are short sequences of amino acids selected by combinatorial techniques for their high affinity for inorganic surfaces. When genetically encoded within proteins, SBPs can function as linkers to create hybrid materials comprising inorganic components and the proteins to which they are fused. Here, we show how such solid binding proteins may be employed to achieve dynamic control over the assembly and disassembly of silica nanoparticles and how the process is influenced by SBP sequence, insertion point within the protein, and solution conditions. Using fluorescent-resonant energy transfer (FRET), dynamic light scattering (DLS) and scanning electron microscopy (SEM), we show that bifunctional derivatives of superfolder green fluorescent protein (sfGFP) engineered with two strong, or with a strong and a weak silica-binding peptide support the pH-dependent aggregation and disaggregation of rhodamine-containing silica nanoparticle (RhSiNP). We further demonstrate that pH shifts can be used to cycle nanoparticles between assembled and dispersed states and that aggregate size can be tuned with different SBPs, NP sizes, and salt concentrations. Additionally, we designed multimeric de novo and natural proteins for increased control over the pattering of silica nanoparticles (SiNPs) and designed ZnS binding and cysteine binding sfGFP for the association of QDs into protein-linked nanomaterials. This new paradigm for the synthesis of dynamic nanoparticle systems should find applications in biosensing, diagnostics, and advanced materials.