Tech

April 18, 2014

AFRL researchers uncover structural, function relationships in bioinspired nanomaterials

Tim Anderl
Wright-Patterson AFB, Ohio

In his 1954 work, The Nature of Science, Edwin Powell Hubble said, “Equipped with his five senses, man explores the universe around him and calls the adventure Science.”

During his tenure with the Air Force Research Laboratory, National Research Council associate Dr. Nick Bedford, embarked on such an adventure that applied both biological and physical principles prevalent in the world around him to uncover scientific phenomena and understanding.

“For over millennia, nature has devised methods for the creation of hierarchical nano/micro scale inorganic structures under benign aqueous conditions,” Bedford explained. “The precise synthesis and arrangement of biogenic inorganic materials is only achievable because of the level of functional and structural sophistication found in biomolecules such as proteins, peptides, and nucleic acids. Inspired by such processes, the material science community has seen a significant increase in the use of biological molecules to create nanomaterials.”

Further, scientists recognize that by exploiting the inherent complexity/programmability of peptides, it may be possible to achieve tunable materials functionality and spatial arrangement by simple alteration of the amino acid sequence, Bedford added. However, such precise nanoscale control can only be accomplished if a thorough understanding of biotic/abiotic interactions is known.

With this understanding, Bedford came to AFRL research leader Dr. Rajesh Naik, who he’d collaborated with during a Dayton Area Graduate Studies Institute fellowship program, with an idea. The NRC mentor suggested he submit the proposal to AFRL via the NRC associateship program. Naik and his team at the Materials and Manufacturing Directorate at AFRL are actively engaged in understanding the design rules that govern the interaction between biomolecules and abiotic materials such as metal, carbon nanomaterials and polymers.

“The proposal scored well and I was invited to begin working in March 2013,” Bedford said.

The collaborative research effort is already yielding results that represent a critical step forward to fully understand the complete biotic/abiotic scope of materials, and uncovering fundamental science that has never previously been understood.

According to Bedford, the discovery has the potential to enhance the properties and change the structures of materials allowing them perform in different and better ways. Uncovering better, stronger materials with enhanced capabilities is of paramount importance to Air Force scientists working towards next generation aerospace systems.

Until now, experimental and theoretical techniques have been used to help understand peptide surface morphology at this critical interface, yet virtually nothing is known about the underlying inorganic structure. “Research I conducted with peers at AFRL, Argonne National Laboratory, the University of Miami, Florida, University of Akron, Central Michigan University and Brookhaven National Laboratory illuminates the precise relationships and interactions at the biotic/abiotic interface and within the inorganic nanomaterial,” Bedford said.

Using synchrotron radiation characterization techniques, Bedford and collaborators at AFRL can determine atomic scale structural differences in nanoparticles generated with peptides of varying amino acid diversity. “Using bio-inspired Palladium (Pd) nanocatalysts as a model system, we were able to generated nanoparticle configurations by modelling atomic pair distribution functions (PDF), obtained from high-energy X-ray diffraction data, using a reverse Monte Carlo (RMC) algorithm.”

“Potential structural differences caused by slight changes in the amino acid content of the capping peptide, ultimately have a direct impact on the catalytic activity,” Dr. Bedford added “The results from the RMC fitting, shown in the accompanying figure, corroborate this hypothesis, demonstrating different amounts of surface disorder for each peptide analog.

“Such structural information is important, as it can help elucidate sequence dependent structure/function relationships needed to create a nanomaterial with tunable properties.”

While peptide-capped Pd is a noteworthy material in terms of its catalytic properties, other bio-inspired materials are also being studied in a similar manner to obtain universal and material specific peptide induced structure/function relationships. These materials include Gold, and Titania with applications in sensing, optics, energy storage and energy harvesting.

Moving forward, computational methods will also be used in conjunction with atomic PDF data to help determine the morphology of the peptide on these surface disordered structures. With the combined diffraction/computational characterization efforts, it is envisioned that a set of “design rules” will be developed for the creation of highly programmable nanomaterials and nanomaterial assemblies, potentially allowing for creation nanomaterials with the precision of nature.

Bedford and his collaborators are currently completing a research paper and will publish their discoveries. In the meantime Dr. Bedford is searching for new opportunities and weighing his career options as an independent researcher, in academia or at another government laboratory.

“The opportunity, collaborations and freedom this NRC associateship provided were extremely valuable and fruitful,” Bedford admitted. “The result is the discovery of new, fundamental science nobody knew about.”




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