Self-Assembly of Dendrimer-Encapsulated Nanoparticle Arrays Using 2-D Microbial S-Layer Protein Biotemplates

Abstract

We investigated the formation of self-assembled two-dimensional (2-D) arrays of dendrimer-encapsulated platinum nanoparticles (Pt-DENs) using prokaryotic surface-layer (S-layer) proteins as biomacromolecular templates. The Pt-DENs (mean core diameter 1.8 +/- 0.5 nm) were synthesized by chemical reduction of metal ion species complexed within the interior of fourth-generation, hydroxyl-terminated, starburst poly(amidoamine) dendrimers (G4 PAMAM-OH). Detailed structural and elemental composition analyses performed using high-resolution transmission electron microscopy, energy-dispersive X-ray spectroscopy, electron energy loss spectroscopy, and X-ray photoelectron spectroscopy indicated that the dendrimer-metal nanocomposite particles were crystalline in nature rather than amorphous and that at least some quantity of the platinum found within the particles is present in the expected zerovalent state. By using the S-layer lattices from the acidothermophilic archaeon Sulfolobus acidocaldarius and the Gram-positive bacterium Deinococcus radiodurans as a biotemplate, hexagonal- and honeycomb-ordered arrays of the Pt-DENs were successfully fabricated under a range of different pH conditions via noncovalent nanoparticle-protein interactions. Fast Fourier transform analyses of transmission electron microscopy images verified that the fabricated Pt-DEN assemblies displayed mean periodicities that corresponded well with the lattice constants of the native protein templates (i.e., 22 and 18 nm for S. acidocaldarius and D. radiodurans S layers, respectively). Our results demonstrate that utilizing pre-synthesized Pt-DENs in conjunction with microbial S-layer proteins displaying highly periodic topochemical properties can be an effective, novel route for creating patterned arrays of Pt nanoparticles with potential technological applications.

Self‐Assembling Nanoparticles at Surfaces and Interfaces

“…[189] In another example, the formation of self-assembled two-dimensional (2D) arrays of dendrimer (G4 PAMAM-OH) -encapsulated platinum nanoparticles (1.8 nm) using prokaryotic surface-layer (S-layer) proteins as bio-macromolecular templates is reported. [190] Other genetically engineered proteins such as chaperonins, having pores of 3 or 9 nm surrounded by thiols, formed assembled CdSe-ZnS quantum dots with a size of 4.5 nm. [191] Viral proteins are extensively applied by Belcher and co-workers to align Au NPs.…”

Entropically Driven Self‐Assembly of Lysinibacillus sphaericus S‐Layer Proteins Analyzed Under Various Environmental Conditions

“…[27][28][29][30] there is currently no high-resolution structural data of a full protein available for members of this class of proteins. [31][32][33] Because of this lack of structural information, recently cysteine residues were incorporated by point mutations on the S-layer protein from Geobacillus stearothermophilus PV72/p2 to be used to map the location of those individual residues in the protein surface.…”

Biophysical Methods for the Elucidation of the S-Layer Proteins/Metal Interaction

“…The use of SLP as insulating templates [63] for the synthesis of metal nanoparticles and nanowires offers a simple pathway toward the design of "hybrid bioelectronic devices", combining the advantages of typical supramolecular nanosystems with bioelectronic systems [64]. In these "hybrid systems", S-layers embedded with metal nanoparticles can be used to carry out electrochemical functions, thus mimicking the functions of enzymes (biomimetics) [65].…”