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We report the self-assembly of monolayers of spider silk-like block copolymers. Langmuir isotherms were obtained for a series of bioengineered variants of the spider silks, and stable monolayers were generated. Langmuir-Blodgett films were prepared by transferring the monolayers onto silica substrates and were subsequently analyzed by atomic force microscopy (AFM). Static contact angle measurements were performed to characterize interactions across the interface (thin film, water, air), and molecular modeling was used to predict 3D conformation of spider silk-like block copolymers. The influence of molecular architecture and volume fraction of the proteins on the self-assembly process was assessed. At high surface pressure, spider silk-like block copolymers with minimal hydrophobic block (fA=12%) formed oblate structures, whereas block copolymer with a 6-fold larger hydrophobic domain (fA=46%) formed prolate structures. The varied morphologies obtained with increased hydrophobicity offer new options for biomaterials for coatings and related options. The design and use of bioengineered protein block copolymers assembled at air-water interfaces provides a promising approach to compare 2D microstructures and molecular architectures of these amphiphiles, leading to more rationale designs for a range of nanoengineered biomaterial needs as well as providing a basis of comparison to more traditional synthetic block copolymer systems., Published in Langmuir v27 n3 p1000-1008, 2011. Supported in part by NSF.

A novel type of all-natural, biocompatible, and very robust nanoscale freestanding biohybrids are reported. They are obtained by integrating a silk fibroin matrix with functional inorganic nanoplatelets using a spin-assisted layer-by-layer assembly. The organized assembly of the silk fibroin with clay (montmorillonite) nanosheets results in highly transparent nanoscale films with significantly enhanced mechanical properties, including strength, toughness, and elastic modulus, as compared to those for the pristine silk nanomaterials. Moreover, replacing clay nanoplatelets with a highly reflective Langmuir monolayer of densely packed silver nanoplates causes a similar enhancement of the mechanical properties, but in contrast to the materials above, highly reflective, mirror-like, nanoscale flexible films are created. This strategy offers a new perspective for the fabrication of robust all-natural flexible nanocomposites with exceptional mechanical properties important for biomedical applications, such as reinforced tissue engineering. On the other hand, the ability to convert silk-based nanoscale films into mirror-like biocompatible flexible films can be intriguing for prospective photonics and optical exploitation of these nanobiohybrids., Published in Advanced Functional Materials, v20 p840-846, 2010. Sponsored in part by Air Force Research Lab and the Office of Naval Research.

We report on preparation of redox-active nanoscale layer-by-layer (LbL) films with polyaminoacid-decorated surfaces that serve for both nucleation and growth of uniformly distributed gold nanoparticles at ambient conditions. We found that a poly-L-tyrosine (pTyr), a synthetic polyaminoacid, was able to direct nanoparticle formation to solid, flexible, and patterned surfaces preventing particle agglomeration. The gold particles were 8 +/- 2 nm in diameter, surrounded by 3-6 nm polyaminoacid shell, and confined to the topmost polyaminoacid layer. The reported results on bioinspired gold formation can be readily expanded to any inorganic-selective surface and provide a simple, robust, and nontoxic method to obtain nonaggregated inorganic nanoparticles at ambient conditions., Published in Chemistry of Materials, v20 p5822-5831, 2008. Prepared in collaboration with Air Force Research Laboratory, Materials and Manufacturing Directorate, Wright-Patterson Air Force Base, OH. Sponsored in part by Office of Naval Research.