Re-engineering nature through molecular design: self-assembled soft materials

Posted by | November 09, 2019 | Our past, present and future | No Comments
Microscopic image of water droplets

Smart biopolymers

What we need to do is design monomers by taking inspiration from nature.

Dr Brendan Wilkinson, Chemistry, School of Science and Technology

The term “soft matter” evokes rather obvious connotations for many – materials that are soft and squishy! What is perhaps less obvious is how omnipresent and important they are, being widely used in food, medicine, electronics, textiles, tyres, plastics and chemicals refining. It is impossible to quantify their impact on modern society and on how we interact with our environment. Dr Brendan Wilkinson and his team at UNE are developing new classes of ‘smart’ biopolymers. Unlike traditional polymers that are constructed through covalent (bond-forming) reactions, these polymers emulate biological self-assembly processes in water to give adaptable materials that could be used as vaccines, cryoprotectants, and gel-like scaffolds for tissue engineering.

Molecular design is an important cornerstone of the chemical sciences. The shape, structure and electric properties of a molecule are all key factors that determine a substance’s bioactivity, reactivity and physical properties; whether this be a drug, a catalyst or a polymeric material. Whatever the properties we are interested in, and the intended application of the material, these are ultimately driven by molecular design. “Molecular design of individual monomers allows us to pre-program the physical and biological properties of a substance across multiple length scales, ranging from the nanoscale, right up to the macroscopic level that we observe and interact with,” explains Dr Wilkinson. “If we incorporate some chemical functionality at the molecular level that enables the formation of reversible connections between individual monomers, rather than the static irreversible bonds holding together traditional polymers, this would endow the material with the unique ability to self-heal and self-replicate in the presence of an external stress such as changes in pH, temperature, and biological recognition. Such microscopic reversibility between individual monomers is the key – they are weak, but cumulative, a sort of ‘glue’ that can be pulled apart and reformed depending on its environment. The major limitation of traditional polymers is that they are constructed from irreversible bonds between monomers, and so they are ‘fixed’ and cannot respond reversably to changes in the environment, at least not easily,” he adds.

“What we need to do is design monomers by taking inspiration from nature. The dazzling array of functional soft materials produced by nature, all from a handful of molecular building blocks, is absolutely mind-boggling.” Emulating processes found in nature through the design and synthesis of bio-functionalized monomers would provide countless, exciting opportunities in translational and medical research and for the development of new diagnostics, therapeutics, vaccines, and drug delivery vehicles. “It’s a fertile area of research, and a lot of fun to work in. It overlaps strongly with the physical, theoretical and biological sciences so I enjoy working with colleagues on interdisciplinary projects.”

In this respect, much of the progress made to date is grounded in peptide-based building blocks, which have been employed in a proof-of-principle way as gel-like scaffolds for tissue engineering and regenerative medicine. “However, most proteins in the body are glycosylated with sugars,” explains Dr Wilkinson, “and in most cases these sugars impart important bioactivity to the protein, such signalling events that underpin many important physiological processes, including microbial virulence, immune regulation, fertilization, and so on.” Other naturally occurring glycoproteins isolated from certain species of fish have antifreeze properties and so mimicking such materials may even allow for the development of new cryoprotectants. The use of glycopeptide monomers that self-assemble into structures that mimic natural glycosylated polymers is a very exciting prospect and is research led by Dr Wilkinson’s team at UNE. The lessons learnt will not only serve to advance soft materials science, but will also give us a more complete understanding of how biological self-assembly, and hence many life-governing processes, actually works.

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