Amazing spider mite silk key to new nanomaterial “stronger than steel”

Many new technologies need new materials to make them work. And when dealing with medicine, science and engineering, many of these new materials must also be micro-sized to do the business. Enter Miodrag (Mike) and Vojislava (Vava) Grbic.

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Spider mite feeding on bean leaf with eggs nearby. Image by Vladimir Zhurov, Zoran Culo and Nicolas Bensoussan

The Western husband-and-wife research team mines the biosphere for inspiration in developing advanced materials, and their most prolific muse – the spider mite – has delivered the goods again. A specific species of spider mite, the gorse spider mite (Tetranychus lintearius), has provided a genomic framework for new bio-nanomaterials based on its silk.

In a study published in Scientific Reports, the Grbics and their collaborators, who include Western biophysicist Jeffrey Hutter, share their latest findings on this fibre, which is twice as stiff as spider silk and 400 times thinner. Incredibly, on a gram-for-gram basis, the silk of gorse spider mites has a tensile strength up to four times higher than steel. All these amazing properties open the door to countless applications as a nanomaterial.

“Silk produced by mites and spiders is one of the most elegant and well-designed materials in existence,” said Mike Grbic, an associate professor in Western’s biology department. “Silk is a polymer, meaning that it is made of a chain of repeating protein units – kind of like a nanoscale pearl necklace.”

The protein chains in the gorse spider mite’s “pearl necklace” create nano-fibres that can be converted into novel bio-nanoparticles using specific technologies advanced by the Grbic group. Potential applications range from vaccine delivery to food production and even regenerative medicine. And since these new nanomaterials are also biocompatible, biodegradable and non-toxic, the potential for use in diverse sectors becomes even greater, says Grbic.

In their latest paper, the Western team and their research partners at the Barcelona Institute of Photonic Sciences, the University of La Rioja, and the Murcia Institute for Agricultural and Food Research analyzed the characteristics of gorse spider mite silk, which produces near-boundless amounts of the highly important – and highly functional – nano-fibres. Using radiation and light, and a series of nanoscale force measurements led by Hutter, the team also determined their biophysical makeup.

And since the Grbics provided the genomic sequence of spider mites in their landmark 2011 Nature study, the researchers were also able to tweak the code and manufacture new nanoparticles and biofilm based entirely on original spider-mite silk.

Adults Feeding

Two spider mites feeding on bean leaf with eggs nearby. Image by Vladimir Zhurov, Zoran Culo and Nicolas Bensoussan

For example, the new nanoparticles could be combined with specific sequences of antibodies or molecular recognition tags to precisely locate cancer cells in the body or serve as carriers for targeted drug delivery. According to Vava Grbic, current cancer treatments are difficult and expensive to produce, and have uncertain toxicity effects. The versatile and non-toxic nature of a new silk protein means it could be used to target thousands of cell types beyond cancer, making it an ideal bio-molecule “messenger” for directing pharmaceuticals to infected cells.

“We know the alarming effects of inorganic and synthetic polymer compounds in the human body,” said Vava Grbic. “Targeted therapies are laser-precise compared to the sledgehammer that is chemotherapy, but we can do so much better by using a natural bio-molecule that is biocompatible, biodegradable and non-toxic.”

The total market for drug-delivery nanotechnology is expected to reach $136-billion (U.S.) in 2021, making their latest discovery enticing to industry partners and investors. And the Grbic group – armed with the spider mite genome sequence and its patent – plans to research how to manufacture the new nano-material at low cost and mass scale.

The potential applications can hardly be overstated: the nanoparticles can even be used to develop rapid virus tests through combination with a specific antibody and a fluorescent molecule, or to serve as a carrier for vaccines, according to Mike Grbic.

“A current blood sample COVID-19 test cannot tell you if you are currently infected, only that you have the antibodies protecting you from the virus. With a nano-particle, the virus protein can be detected by an anti-virus-protein antibody and the signal of its presence can be amplified to give a rapid reading of infection,” said Mike Grbic.

The nanoparticles could also be used to coat slow-release fertilizer pellets, pesticides and herbicides to create “smart agrochemicals” for use in sustainable agriculture, says Grbic. And when applied in prosthetic implants, the material could dramatically lower the risk of rejection by the body. Further applications may include natural stabilizers to increase the shelf life of food and drinks, and skin-safe additives for cosmetics.

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