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Novel biomimetic nanosprings: Protein-based elastomer for engineering applications

Research Area: Biopolymers, nanomaterials, biological nanoengineering

Supervisors: A/Prof Naba Dutta, Prof Namita Roy Choudhury, Dr Anita Hill (CSIRO Manufacturing and Infrastructure Technology) and Dr Chris Elvin (CSIRO Livestock Industries) 

Aim: To understand, control and exploit the unique chemical and hierarchical structures in resilin protein for promising applications. 

Description: Elastic proteins occur in a wide range of biological systems, where they have been evolved to fulfil precise biological roles. In general, they exhibit rubber-like elasticity, undergoing high deformation under stress, without rupture and recovering to their original state when the stress is removed. The best-known elastic proteins are proteins in vertebrate's muscles and connective tissues (titin, elastin, fibrillin, spider silks), byssus and abductin from bivalve molluscs, resilin from arthropods and gluten from wheat. They are widely distributed, and exhibit unique characteristics, however, only a few have been characterised in detail. Resilin is the most efficient elastomeric protein known and is present in most, if not all insects, where it has been adapted for flight, jumping and sensory mechanisms. The contraction and efficient manipulation of resilin enable the organisms to carry out organised and sophisticated movements generating mechanical energy. The elastic efficiency of the resilin isolated from locust tendon has been reported to be 97% - only 3% of stored energy is lost as heat. It confers long-range elasticity to the cuticle and probably functions as both an energy store and a damper of vibrations in insect flight. It is also used in the jumping mechanisms of fleas and grasshoppers. The most dramatic example of the effect of resilin is the jumping power of fleas. Some fleas can jump 150 times their own length. To match that record, a human would have to spring over the length of two and a quarter football fields, or a height of a 100 story building, in a single bound. 

Over the past number of years, synthetic polymer gels have been employed to create many artificial soft machines such as gel valves, chemical motors, artificial muscles, etc; however, the lack of hierarchical structures in the synthetic polymers lead to a decreased response and restricted their further applications for practical uses. Protein-based polymers can be designed with properties and functions that go beyond those of known proteins, once the rules for protein engineering have been established. Currently, elastomeric proteins attract significant research interest due to: (i) their biological and medical significance, particularly in human disease; and (ii) their unusual properties provide the opportunity to develop novel materials for diverse applications. Kakugo et al. [1] proposed gel machines constructed from chemically crosslinked muscle proteins actins and myosins. Urry and co-workers [2] reported the idea of using the sequence of the protein elastin as a building block to emulate the natural properties of elastin. To date, very little has appeared in the literature about the structure, properties and the potential application of the remarkable protein, resilin. Recently, Elvin [3] has shown, for the first time, that purified recombinant resilin from the insect Drosophila, can be formed into a highly elastic biomaterial via enzymatic crosslinking. In this multidisciplinary project we propose to investigate the idea of using the sequence of the protein resilin as a building block for polymer structures that emulate the remarkable properties of resilin. The research in the area will be divided into three different areas. 

Project 1: This project will aim to produce new functional protein-based elastomeric materials using the sequence of unique elastomeric protein resilin as the building block for polymer structure. Recombinant DNA technology that has revolutionized and is having an ever-increasing impact on clinical medicine will be employed for understanding of the molecular basis, manipulation of DNA sequence and construction of chemical molecules. An effective expression system will be developed. This research investigation will also aid in our understanding of the structural basis for the high resilience and robustness of these novel proteins and how different insects have evolved different physical functions through alteration of the structure of the resilin protein. The researcher on this project will use extensively polymerase chain reaction (PCR), quantitative PCR, circular dichroism (CD), AFM and NMR. This research will bridge the gap between synthetic polymer and biological structures by using hybrid structures containing elements of biomaterial (made by biotechnological approach). This part of the project will be conducted in very close collaboration with Dr.Chris Elvin - CSIRO - Livestock Industries. 

Project 2: Resilin exhibit unusual elasomeric behaviour only when swollen in polar solvents such as water. The resultant polymer synthesized from part I of the project is expected to emulate the unique elstomeric and fatigue resistance characteristic of natural resilin only in the gel state. Therefore, different means of forming and optimising hydrogels using crosslinks in the soluble recombinant protein will be crucial. Extensive investigation on the structures, origin of elasticity, thermodynamic, kinetics, morphology and biomechanical properties of the swollen crosslinked resilin; will be the goal of the project. Differential scanning calorimeter (DSC), spectroscopy, microscopy, AFM, thermal AFM, rheology, dynamic mechanical analysis and scattering techniques (including SANS) will be employed, extensively in this part of the project. 

Project 3: In project 3 we want to explore the functional and fatigue properties of the crosslinked recombinant protein, and to initiate the development of device applications utilising the superior properties of resilin-based nanosprings and nanohinges. In this part we intend to explore the physical and chemical and fatigue behaviour of the crosslinked elastomer gels in aqueous media and study the effect of different variables on these properties. This information will provide a basis for utilizing the resilin protein as an engineering product. 

Finally, we aim to make recommendations for highly efficient device development based on our new understanding of the structure property relationships and effects of processing variables on the properties of resilin-based nanosprings and nanohinges. Bioelastomers developed from this research will find application in microelectronic mechanical devices (MEMS) such as highly efficient actuators, drug delivery vehicles and systems, or in medicine as synthetic vascular prostheses. They will be useful in designing diverse biomolecular machines and materials with promising application for society in low cost. This part of the project will be carried in close collaboration with DR. Anita Hill, CSIRO - Manufacturing and Infrastructure Technology. 

Collaboration: This is a collaborative project and the research methodology will primarily cover investigations carried out in IWRI laboratories, UniSA; at CSIRO - Livestock Industries and CSIRO - Manufacturing and Infrastructure Technology. 

References
1. A Kakugo, S Sugimoto, JP Gong and Y Osada., Adv. Mater. 14,( 2002) 1124. 
2 DW Urry, J. Phys. Chem. B, 101 (1997) 11007. 
3. CM Elvin (2002) A Bioelastomer. Australian Patent Application No. PS2423. 

Funding: This is a successful ARC discovery grant. The grant will support two IWRI fully-funded scholarships. 

International students should also apply for an International Postgraduate Research Scholarship (IPRS) and a UniSA President's Scholarship (UPS). To be eligible for UPS, applicants must have a supervisor willing to nominate them for consideration. 

Australian students should also apply for an Australian Postgraduate Award (APA) and a UniSA Australian Postgraduate Research Award (USAPRA). 

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