June 13, 2018 | David F. Coppedge

Nature Knows Best

Recent news articles show how engineers and inventors are helping mankind by imitating what plants, cells and animals do every day.

A new kind of vaccine based on spider silk (Science Daily). Because spider silk is tough and yet biodegradable, it can be used as a delivery capsule for vaccines that might otherwise be resisted by the body’s immune system. Based on that fact,

researchers from the universities of Geneva (UNIGE), Freiburg (UNIFR), Munich, and Bayreuth, in collaboration with the German company AMSilk, have developed spider silk microcapsules capable of delivering the vaccine directly to the heart of immune cells. This process, published in the journal Biomaterials, could also be applied to preventive vaccines to protect against infectious diseases, and constitutes an important step towards vaccines that are stable, easy to use, and resistant to the most extreme storage conditions.

A world specialist in spider silk explains the motivation. “More and more, scientists are trying to imitate nature in what it does best,” adds Thomas Scheibel. “This approach even has a name: bioinspiration, which is exactly what we have done here.

Speaking of spider silk, Japanese scientists at RIKEN have made progress understanding how the spider makes it. Phys.org says that they “examined the soluble precursor of spider silk and found that a previously undiscovered structural element is key to how the proteins form into the beta-sheet conformation that gives the silk its exceptional strength.” And why is spider silk so attractive as a bio-inspirational material?

According to Keiji Numata, who is a project leader of JST ImPACT and led the research group, “Spider silk is a wonderful material, as it is extremely tough but does not contain harmful substances and is readily biodegradable, so it does not exert any harmful load on the environment. We hope that this discovery will help make it possible to create artificial silk that will prove useful for society.

Fluid jets from navel orange (PNAS).

High-speed microjets issue from bursting oil gland reservoirs of citrus fruit (PNAS). Why do lemons squirt you in the eye? Squeeze most citrus fruits as you peel them, and you are blasted by high-speed jets of oil from the inner rind. Scientists decided to figure this out. In a somewhat amusing paper, four scientists intentionally squeezed navel oranges to film the jets at slow motion, and found that they are among the fastest jets in nature. The only animal that gets more G’s of acceleration is the mantis shrimp with its hammer claw. The orange accelerates oil to 10 meters per second in just 1 millimeter! That’s 5,100 G’s. Short video clips in the paper show the jets in action. The team doesn’t know why citrus fruits do this, or what function it serves the plant, but it gave them ideas.

Here we show a unique, natural method for microscale jetting of fluid made possible by the tuning of material properties from which the jets emanate. The composite, layered construction of the citrus exocarp allows for the buildup of fluid pressure in citrus oil gland reservoirs and their subsequent explosive rupture. Citrus jetting has not been documented in literature, and its purpose is unknown. This method for microscale fluid dispersal requires no auxiliary equipment and may open avenues for new methods of medicine and chemical delivery. We show how jet kinematics are related to substrate properties and reservoir shape.

Bent bird feathers repair themselves when soaked in water (New Scientist). Would you like an umbrella that can repair itself in the rain? Scientists may be able to make those, if they follow the inspiration of bird feathers. Watch that bird in the bird bath. “Splashing around in water doesn’t just get a bird clean,” writes Leah Crane: “– it can also repair broken feathers from the inside.” A spongy matrix of fibers in the feather absorbs water. Parts expand; other parts do not. Water fills the matrix like air in a balloon, expanding the broken feather to its original shape. “Because the fibres bend elastically, they ‘remember’ their previous straight shape – once the matrix was softened by water, internal pressure from the swollen matrix encouraged the bent fibres to spring taut again.” Marc Meyers at the University of California says, “artificial materials engineered to mimic feathers could be used for self-healing structures, like antennae that repair themselves in the rain.”

Nature’s traffic engineers have come up with many simple but effective solutions  (Tanya Latty at The Conversation). Too bad Tanya begins with Darwin worship:

As more and more people move to cities, the experience of being stuck in impenetrable gridlock becomes an increasingly common part of the human experience. But managing traffic isn’t just a human problem. From the tunnels built by termites to the enormous underground networks built by fungi, life forms have evolved incredible ways of solving the challenge of moving large numbers of individuals and resources from one place to another.

Once her Darwin trance subsided, Latty described the elegant solutions devised by ants to find the optimum path, how army ants march in lanes, and how they will fill potholes with their own bodies so others can march over them. And did you hear about the Humongous Fungus?

It’s not just insects that build transport networks. Brainless organisms such as fungi and slime moulds are also master transportation designers.

Fungi build some of the biggest biological transportation systems on Earth. One giant network of honey fungus (Armillaria solidipes) spanned 9.6km. The network is made up of tiny tubules called mycelia, which distribute nutrients around the fungi’s body.

A video clip shows how the lowly slime mold can map the Tokyo Subway System. “Nature has found many different solutions to the universal problem of building and managing a transport system,” she concludes. “By studying biological systems, perhaps we can pick up a few tips for improving our own systems.

Addendum: Some Technical Papers on Biomimetics

Biological tissue-inspired tunable photonic fluid (PNAS). “We design an amorphous material with a full photonic bandgap inspired by how cells pack in biological tissues,” three engineers report. “The size of the photonic bandgap can be manipulated through thermal and mechanical tuning.”

A bioinspired flexible organic artificial afferent nerve (Science). “Sensory (or afferent) nerves bring sensations of touch, pain, or temperature variation to the central nervous system and brain. Using the tools and materials of organic electronics, Kim et al. combined a pressure sensor, a ring oscillator, and an ion gel–gated transistor to form an artificial mechanoreceptor (see the Perspective by Bartolozzi).”

In vitro biomimetic engineering of a human hematopoietic niche with functional properties (PNAS). This team tried to imitate human bone marrow. “Here, we report the development of a human 3D (BM) analogue in a perfusion-based bioreactor system, partially recapitulating structural, compositional, and organizational features of the native human osteoblastic niche environment. The engineered tissue supports the maintenance of some hematopoietic stem and progenitor cell (HSPC) properties.”

Robust nonequilibrium pathways to microcompartment assembly (PNAS). Two researchers tried to imitate the carboxysome, a cellular “cage” that packages biological material. “We identify experimentally tunable parameters that modulate the shape and size of the assembled structure, advancing strategies to repurpose natural microcompartments and to create synthetic mimics.”

How electrostatic networks modulate specificity and stability of collagen (PNAS). By studying the electrostatics of triple-helix collagen, scientists hope to mimic its properties. “The critical balance of electrostatic and hydrogen-bonding interactions is dramatically revealed in an atomic-resolution structure of the design,” the six authors say. “A predictive model of collagen stability and specificity is developed for engineering novel collagen structures.

In 21st century biology, design science is where it’s at. Darwin is toast. He’s so 1859. Time to ditch natural selection (3 October 2015) and look at life with an eye to engineering.

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