The arms and tentacles of cephalopods are used by the animal for prey capture and handling
Smart material made from squid ring teeth a potential plastic alternative
Monday, March 04, 2019, 05:00 (GMT + 9)
Nylon and polyester could one day be a thing of the past, reducing microplastic pollution in the oceans and paving the way for self-repairing safety clothing or garments with built-in, flexible screens.
ACS Biomater. Sci. Eng., 2017, 3 (5), pp 680–693 | American Chemical Society
A newly-discovered material made from squid teeth could one day replace man-made fibres like nylon and polyester, according to a review by scientists at Pennsylvania State University. This would help to reduce microplastic pollution in the oceans, as well as paving the way for new possibilities such as self-repairing safety clothing, or garments with built-in, flexible screens.
Molecular architecture and repetitive sequences of fibrous protein polymers: (i) coiled-coils (e.g., collagen and keratin), (ii) β-turns/spirals (e.g. elastin and resilin), and (iii) β-sheets (e.g., silks and squid ring teeth).(Photo: frontiersin.org) | Click on the photo to enlarge
The arms and tentacles of Decapodiform cephalopods (squids and cuttlefish) are lined with suckers, each of which contains embedded sucker ring teeth (SRT), which are used by the animal for prey capture and handling. SRT exhibit intriguing physicochemical and thermomechanical characteristics that have so far not been observed in other protein-based biomaterials. Notably, despite their comparatively high mechanical properties, SRT are almost fully soluble in chaotropic solvents and can be readily reconstituted after solvent evaporation into three-dimensional structures. SRT also exhibit thermoplastic characteristics: they can be melted and reshaped multiple times with no–or only minimal–loss of mechanical performance postprocessing.
Squid ring teeth (SRT) are found inside suction cups of squid species, which are composed of a protein complex. Proteins can be extracted directly from natural sources, or expressed (A) recombinant and (B) de novo via biosynthetic routes (genetically modified bacteria, yeast). Adapted with permission (Pena-Francesch et al., 2018b). Copyright 2018 American Chemical Society.(Photo: .frontiersin.org) | Click on the picture to enlarge
The smart materials in question are made from a material found in the suckers on a squid’s tentacles. In some species, these suckers have a ring of ‘teeth’ to help the squid grip onto a surface. These are known as SRTs – squid ring teeth – and it’s the proteins they’re made of that have scientists excited.
SRT proteins are made up ‘building blocks’ that can combine in different ways to produce materials with different properties. Depending on the arrangement of the blocks, the material that results may be electrically conductive, or have self-healing properties, for instance.
Tunable properties of tandem repeat proteins inspired by SRT. Mechanical behavior in (A) dry and (B) wet conditions is highly dependent on tandem repetition. Reproduced with permission (Jung et al., 2016; Pena-Francesch et al., 2018c). Copyright 2016 National Academy of Sciences. Copyright 2018 American Chemical Society. (C) Mechanical and conducting (proton and thermal transport) properties of SRT-based materials are programmable and controlled by the amino acid composition, nanostructure, and network morphology. Reproduced with permission (Pena-Francesch et al., 2018b,c; Tomko et al., 2018). Copyright 2018 American Chemical Society. Copyright 2018 Nature Publishing Group. | Click on the picture to enlarge
“Nature produces a variety of smart materials capable of environmental sensing, self-healing and exceptional mechanical function,” said Melik Demirel, director of Penn State’s Center for Research on Advanced Fiber Technologies, who led the research. “These materials, or biopolymers, have unique physical properties that are not readily found in synthetic polymers like plastic. Importantly, biopolymers are sustainable and can be engineered to enhance their physical properties.”
Microfibres becoming detached from items of clothing in the washing machine are currently one major source of microplastic pollution, whereas clothing coated with SRT protein-based materials would be more durable.
Similarly, self-healing smart materials could be used to manufacture better safety wear, such as hazmat suits, say the researchers. By using layers of different SRT materials, interwoven with other layers, you could even create garments that change colour when air pollution hits dangerous levels, or with a built-in, flexible display.
Multifunctional films fabricated from squid-derived proteins. SRT proteins are processed via (a) solution-based or (b) thermal-based methods into a variety of materials. Reproduced with permission (Pena-Francesch et al., 2014b). Copyright 2014 Wiley. (c)Colloids. Reproduced with permission (Pena-Francesch et al., 2014b). Copyright 2014 Wiley. (d) Free-standing transparent flexible films. Reproduced with permission (Yilmaz et al., 2017). Copyright 2017 American Chemical Society. (e) Complex 3D geometries. Reproduced with permission (Pena-Francesch et al., 2018b). Copyright 2017 American Chemical Society. (f) Biomimetic materials. Reproduced with permission (Michaels et al., 2015). Copyright 2015 Springer (g) Optical microresonators. Reproduced with permission (Yilmaz et al., 2017). Copyright 2017 American Chemical Society. (h)Nanostructured surfaces. Reproduced with permission (Guerette et al., 2013). Copyright 2013 Nature Publishing Group. (i)SRT-based membranes. | Click on the picture to enlarge
“SRT photonics are biocompatible and biodegradable, so could be used to make not only wearable health monitors but also implantable devices for biosensing and biodetection,” adds Demirel.
Best of all, there’s no cruelty to animals involved, either – the SRT proteins can be grown in a lab, using genetically modified E.coli bacteria, without needing to trouble the already dwindling squid population. Indeed, it’s far more efficient to grow them from scratch than it would be to ‘harvest’ them from nature.
Abrasion-resistant SRT protein coatings for advanced textiles. (a) FTIR spectra of SRT-coated and non-coated microfiber cloth. (b) Pre-abrasion non-coated microfibers are bundled, but they are (c) damaged and frayed after the abrasion test. (d) Pre-abrasion SRT-coated microfibers are bundled as well, but (e) after the abrasion test the microfibers are aligned and not damaged.(Photo: frontiersin.org) | Click on the picture to enlarge
“We don’t want to deplete natural squid resources, and hence we produce these proteins in genetically modified bacteria. The process is based on fermentation and uses sugar, water and oxygen to produce biopolymers,” Demirel explains.
“Scaling up these materials requires additional work,” he continues. “We are now working on the processing technology of these materials so that we can make them available in industrial manufacturing processes.”
By Alice Lipscombe-Southwell/sciencefocus.com