Biomimetic synthesis of bimorphic nanostructures

The widespread interest in the use of biomimetic approaches for inorganic nanomaterial synthesis have led to the development of biomolecules (peptides, nucleic acids) as key components in material synthesis. Using biomolecules as building blocks, additional functionalities can be introduced by engineering multifunctional peptides that are capable of binding, nucleating, and assembling multiple materials at the nanoscale. We describe methodologies that exploit peptides for the synthesis of bimorphic nanostructures.

Bio-based approaches to inorganic material synthesis

Nature is an exquisite designer of inorganic materials using biomolecules as templates. Diatoms create intricate silica wall structures with fine features using the protein family of silaffins as templates. Marine sponges create silica spicules also using proteins, termed silicateins. In recent years, our group and others have used biomolecules as templates for the deposition of inorganic materials. In contrast with the traditional materials science approach, which requires high heat, extreme pH and non-aqueous solutions, the bio-based approaches allow the reactions to proceed usually at near ambient conditions. Additionally, the biological templates allow for the control of the inorganic nanoparticle morphology. The use of peptides and biomolecules for templating and assembling inorganics will be discussed here.

Peptide-assembled optically responsive nanoparticle complexes

The design of active nanostructures whose form and properties can be modulated by remote means is an important challenge in nanoscience. Here we report two types of active nanoparticle complexes, with properties controlled by near-infrared illumination, resulting from the assembly of photothermally responsive plasmonic nanoparticles with thermally labile biomolecular linkers. Au nanoshells (NS) and quantum dots (QD) are assembled using coiled-coil peptides into NS-NS and NS-QD complexes. Illumination of the NS-NS complexes results in reversible disassembly reassembly, while illumination of NS-QD complexes results in a large, reproducible modulation of the quantum dot fluorescence without disassembly of the nanoparticle-peptide complex.

Screening of combinatorial Peptide libraries for nanocluster synthesis

A significant challenge in bionanotechnology is the discovery of effective biological interfaces that allow inorganic nanoscale materials to mimic effectively their biological counterparts. Much like de novo design of proteins, the rational design of such interfaces is a daunting task. An alternative approach is to screen libraries of peptides, inspired by known biological examples of such hybrid protein-material interfaces, for peptide ligands capable of not only stabilizing a size-discrete population of nanoclusters, but providing the requisite biological compatibility. The protocol described in this chapter is an approach for the simultaneous screening of spatially addressable combinatorial libraries for the stabilization of a variety of metal sulfide, metal oxide, and zero-valent nanoclusters. Additionally, the screening process allows the researcher to characterize the resulting nanoclusters in terms of a variety of physical properties. Ultimately, an informatics structure-function analysis may be performed in order to elucidate specific properties of the ligand sets, which provides access to certain desired material characteristics.

Biomimetic mineralization of noble metal nanoclusters

A number of biological systems have developed highly orchestrated detoxification mechanisms toward the bioreduction and mineralization of noble metals. These systems incorporate small peptides and proteins as nucleation sites for metal binding and nanocluster stabilization. Herein, we present the use of biologically relevant ligands ranging from single amino acids (histidine, imidazole, and cysteine) to linear peptides (glutathione and a histidine rich peptide) in the stabilization of a variety of noble metal surfaces (Au(0), Ag(0), Pt(0), and Cu(0)). As a result, the different nanocluster/ligand combinations offered a broad range of sizes and stabilitites. The peptide coat also affords a unique functional handle for the formation of larger assemblies. Using Ni chelation and immunomolecular approaches, strategies for the assembly of nanocluster heterostructures were investigated.