The parable of those who take to them other than God for guardians (to entrust their affairs to) is like a spider: it has made for itself a house, and surely the frailest of houses is the spider’s house. If only they knew this! (Qur’an, 29:41)

A prehistoric Greek fairytale says a young girl named Arachne was a superb spinner and knitted the most gorgeous cloth. She dared the goddess Athena to a competition. When Athena saw Arachne’s stunning work, she ripped the cloth and hit the young girl. Disgraced, Arachne committed suicide by hanging herself. Athena regretted and transformed Arachne into a spider, so that she could whirl repeatedly and endlessly. Arachnida is the scientific name for spiders. It comes from the young girl in the famous Greek fairytale.

Although usually feared and disliked by people, spiders in fact make life easy for us by feeding on mosquitoes, flies, and locusts, thus saving our crops and eliminate the need for man-made insecticides which pose environmental problems. Besides, spiders are much less dangerous than people think they are; most spiders are keen to avoid interaction with people and will bite only when wounded or scared. Even poisonous spiders are rarely as dangerous as popular myths would have us believe: though black widows are poisonous, and their bites painful, they rarely kill people. If handled properly and quickly the adverse consequences of a black widow’s bite typically diminish in a few hours, and, after a couple of days’ rest or cessation of activities, the victim will fully recuperate [1].

There are countless features of spiders. But their silk is exceptionally unique and this article covers its various aspects.

Spider silk

Biomaterials, having developed over millions of years, frequently surpass man-made substances in their properties. Spider silk is an exceptionally stringy biomaterial which is made almost completely of substantial proteins. Silk fibers have stretchy powers similar to steel and some silks are practically as elastic as rubber on a weight-to-weight basis. In uniting these two properties, silks disclose a hardiness that is two to three times that of artificial fibers like Nylon or Kevlar. In addition, spider silk is also antimicrobial, hypoallergenic, and completely biodegradable [2].

The power of spider silk, so fragile in manifestation, is astonishingly great. A filament can be outstretched as much as one half its normal length before breaking, and has a tensile strength exceeded only by fused quartz fibers. Fine fibers are sturdier than others, the power to some degree depending on the velocity with which they are pulled out of the spider’s body. The higher the speed, the superior the strength.

Most of the silken fibers are not single fibers but are made up of two or more strings. A thread may be as fine as a millionth of an inch in width but, frequently, it is ten or twenty times as dense, and the assemblage of these threads unsurprisingly creates larger threads of a diversity of thicknesses. Furthermore, some threads are gluey whereas others are not.

Scientific research demonstrates that a single thread of spider silk, thick as a pencil, could stop a 747 Jumbo Jet in flight, and that on an equivalent footing, the spider’s silk is stronger than steel, per unit weight. It has been shown that the dragline silk of the golden orb spider is one of the planet’s hardest threads.

Spiders employ silk for webs, but also for trap lines, draglines, ballooning lines, for egg pouches and nursery nets, for compartments in which to sleep through winter or to copulate, and for entrapping and wrapping their victims. Silk for all these objectives is not accomplished with one kind of gland; there are at least seven distinct kinds. A few distinctive spiders have as many as six kinds and probably have more than six hundred independent glands; others have fewer than this [1].

Mechanism behind the formation of spider silk

A batch of scientists headed by researchers from the RIKEN Center for Sustainable Resource Science (CSRS) have scrutinized spider silk and discovered that a formerly undiscovered organizational constituent is critical to how the proteins form into the beta-sheet conformation that gives the silk its extraordinary power [3]. If humans can cultivate equivalents to spider silk, they could be applied in industrial and medical applications. It is well-known that the beta-sheets in spider silk are significant to its strength, but how the sheets are created is scantily comprehended, making it difficult to produce synthetic variations. It is hard to comprehend the process: the silk is originally produced as soluble proteins, which very swiftly crystalize into a solid form.

To explain this, the CSRS scientists obtained silk proteins using genetically altered bacteria that can generate silk from a golden orb-web spider (Nephila clavipes) and then executed multifaceted examinations of the soluble proteins. They discovered that the reiterating area is comprised of two designs – unsystematic spirals and a design called polyproline type II helix. Their investigations confirmed that the polyproline type II helix is critical for the creation of the stiff construction, which can then be rapidly converted into beta-sheets, letting the silk be swiftly intertwined. Fascinatingly, it was discovered that pH – which is supposed to be significant for the molecular exchanges of the N- and C- terminus areas – does not play a significant role of the foldup of the recurring areas, and that it is rather the elimination of water and mechanistic forces through the silk gland.

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” [4]. Numata hopes that this discovery may lead to the production of artificial silk that will prove useful for society.

Analysis of silk

The silk itself is a material identified as a “scleroprotein.” When created in the glands it is a fluid; only when dragged outside the body does it solidify into thread. Once it was believed that contact with air produced the toughening, but it currently looks that the drawing-out activity alone is accountable for the change.

To carry out the exertion done by the glands, a spider is armed with spinnerets, usually six in number. These are as accommodating as fingers; they can be prolonged, compacted, and overall be applied like human hands. In the “spinning field,” where the spinnerets are congregated, single threads are joined into numerous compound threads, and some of the dehydrated threads may be covered with a gluey substance. Thus, a completed thread may be thin or thick, dry or sticky. It may also have the look of a bead-trimmed necklace. For the last kind, the spider spins rather unhurriedly and, drawing out the gluey thread, lets it go with a jolt. The liquid thus is organized in beads spread out lengthwise across the completed line.

The strand known as the dragline may be understood as a spider’s “life line” because it performs as a lifeguard in all kinds of situations. The dragline goes along with the spider, no matter where or how far it journeys, winding out from spinnerets at the back of the body. It forms a portion of the building of webs, it grips its tiny builder firmly in problematic places, and it helps in absconding from adversaries. When a spider is inactive in a web, the dragline enables a rapid descent and escape. It allows energetic chasing spiders to jump from buildings, cliffs, or any tall position with absolute security. [1]  

Benefits of spider silk to us

The silk of the silkworm could be very profitable and marketable. There are, however, challenges. One is the changing thickness of a spider’s strand; the other is that it doesn’t well endure the interweaving process. Housing and feeding large numbers of silkworms is not difficult. But housing and feeding large numbers of spiders? There are enormous difficulties.

Native inhabitants of New Guinea have used spider silk in a variety of conditions. They make fishing nets, traps, and such objects as bags, headdresses that will keep away rain, and caps. These are not formed from single threads but from tangled, warped threads. The aboriginals of North Queensland, Australia, look to spiders for their angling supplies.

Spider silk has been valuable to the manufacturers of such complex instruments as astronomical telescopes, guns, and engineers’ levels. The threads, being exceedingly fine but nonetheless robust, are outstanding for sighting marks. Throughout the Second World War, there was a significant demand for spider thread for surveying and laboratory instruments. Black widow spiders were utilized for the manufacture of this silk.

One drawback to the use of spider silk in industry is that it might slump in a moist environment. To overcome this problem, strands of platinum or etching on glass plates take its place in such instruments as periscopes and bombsights. [1]

Spider’s silk also might have healing properties. Due to its antibacterial properties and because the silk is abundant in vitamin K, it may be efficient at clotting blood. Because of the problems in obtaining and handling extensive amounts of spider silk, the largest known piece of cloth made of spider silk is an 11 by 4-foot (3.4 by 1.2 m) fabric made in Madagascar in 2009. Eighty-two persons labored for a period of four years to gather over one million golden orb spiders and extract silk from them. [5]  

Applications of spider silk

As mentioned, human beings have been using spider silk for thousands of years.

The manufacture of contemporary synthetic super-fibers such as Kevlar (bulletproof material) includes petrochemicals, which adds to pollution. Kevlar is also strained from concentrated sulphuric acid. In comparison, the manufacture of spider silk is totally ecologically sustainable. It is created by spiders at ambient temperature and pressure and is strained from water. Furthermore, silk is totally biodegradable. If the manufacture of spider silk ever becomes industrially practical, it could be a substitute for Kevlar and be used to create a varied extent of articles such as: bulletproof vests, wear-resistant lightweight clothing, ropes, nets, seat belts, parachutes, rust-free boards on motor vehicles or boats, biodegradable bottles, bandages, surgical thread, artificial tendons or ligaments, and backings for weak blood vessels. [6]

Synthetic spider silk [5]

Duplicating the multifaceted settings needed to make threads that are similar to spider silk has been difficult to both research and manufacture. Through genetic engineering, Escherichia coli bacteria, yeasts, plants, silkworms, and animals have been utilized to produce spider silk proteins. Yet, these synthetic threads have diverse, simpler features than those of a spider. Manmade spider silks have lesser and unsophisticated proteins than natural dragline silk, and have subsequently half the diameter, strength, and flexibility.

One tactic is to remove the spider silk gene and utilize additional life forms to generate the spider silk. Canadian biotechnology company Nexia effectively produced spider silk protein in transgenic goats that passed the gene for it; the milk made by the goats comprised noteworthy amounts of the protein: 1-2 grams of silk proteins per liter of milk. To make spider silk, Nexia utilized damp whirling and pressed the silk protein across minor extrusion cavities in order to mimic the performance of the spinneret, but this process was not adequate to duplicate the sturdier characteristics of innate spider silk.

In March 2010, investigators from the Korea Advanced Institute of Science and Technology was able to produce spider silk by means of the bacteria E. coli, altered with definite genes of the spider Nephila clavipes. This tactic removes the necessity of milking spiders.

It should be noted that the manufacture of spider silk is not easy and there are intrinsic difficulties. First of all, spiders cannot be cultivated like silkworms since they are flesh-eaters and will merely eat each other if in proximity to each other. The silk produced is very slight, so 400 spiders would be required to make only one square yard of cloth. The other problem is, silk also toughens when subjected to air, which makes working with it problematic.

A different tactic is to study how spiders whirl silk and then replicate this process to make artificial spider silk. The silk itself would also have to be synthetically produced. Chemical production of spider silk is not feasible at present due to the absence of information about the makeup of silk. Randolph V. Lewis, Professor of Molecular Biology at the University of Wyoming in Laramie, has introduced silk genes into Escherichia coli bacteria so that the recurring sections of spidroin 1 and spidroin 2 efficaciously come to form. Others theorize about the likely gene introduction into fungi and soya plants. It may also be possible to modify the silk genes for precise intentions.

Why a spider’s house is the frailest of houses

Spider silk is stronger than steel, but the Qur’an (29:41) states that the flimsiest of houses is the spider’s house. The per unit weight of the dragline silk of the golden orb spider is one of the world’s hardest fibers. Webs are combinations of many kinds of spider silk, all able to be produced by the same spider. The web radials are strong, but the somewhat feebler circumferential (quasi-circular concentric) fibers are flexible and gluey to absorb the energy of a flying insect and hold it in place. The strongest of all is the fiber, which the spider uses for transport, the dragline silk. In summary, the spider fabricates both sturdy as well as feeble fibers and the web it weaves to catch flying insects is weaker; this may be the reason why it is referred to in the Qur’an as the “frailest” of houses.

Conclusions

Scientists are foreseeing many potential uses for biosilk. Textile usages are noticeable one. The flexibility and potency of prevailing merchandises such as spandex and nylon have to be improved. Since it is lightweight, hardy and flexible, biosilk may also have uses in satellites and aircraft. More prominently, the new group of progressive things that spider silk investigation may cause has the prospective to alter our lives in innumerable manners that we can barely imagine. More than 72 years have passed since the inventions of Wallace and Carothers that gave the world nylon that led us into the age of polymers. Artificial spider silk may help produce super-performing clothes of the future. Earthquake resistant suspension bridges hung from cables of synthetic spider silk fibers may someday be a reality. [1]

References

1. Syed, I. B. : Spider Silks http://www.irfi.org/articles/articles_1_50/spider_silks.htm
2. Romer, L and Scheibel, T.: The elaborate Structure of spider silk, PRION, Oct-Dec. 2(4) 154-161, 2008. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2658765/
3. RIKEN Center for Sustainable Resource Science (CSRS). Scientists discover key mechanism behind the formation of spider silk. Materials Science. May 29, 2018, https://phys.org/news/2018-05-scientists-key-mechanism-formation-spider.html

4. Nur Alia Oktaviani, Akimasa Matsugami, Ali D. Malay, Fumiaki Hayashi, David L. Kaplan, Keiji Numata, “Conformation and dynamics of soluble repetitive domain elucidates the initial β-sheet formation of spider silk”, Nature Communications, 10.1038/s41467-018-04570-5 https://en.wikipedia.org/wiki/Riken
5. Service, Robert F. (18 October 2017). “Spinning spider silk into startup gold”. Science Magazine, American Association for the Advancement of Science. Retrieved 26 November 2017. https://en.wikipedia.org/wiki/Spider_silk
6. Vivienne Li, University of Bristol, Spider Silk and Venom. Molecule of the Month – July 2002. http://www.chm.bris.ac.uk/motm/spider/page4.htm

{module Science Square (Issue 128)}

First miniature human heart printed

Noor N et al. 3D Printing of Personalized Thick and Perfusable Cardiac Patches and Hearts.  Advanced Science, April 2019.

In a major breakthrough, researchers have “printed” the world’s first 3D vascularized engineered heart using a patient’s own cells and biological materials. This could have huge repercussions for human health: the World Health Organization said that last year, ischemic heart disease and stroke were the world’s leading cause of death for both men and women. Heart transplantation is currently the only treatment available to patients with end-stage heart failure. Given the serious shortage of heart donors, scientists have been trying to develop new “3D organ printing” approaches to regenerate the diseased heart. Past studies were only able to print simple tissues without blood vessels. The new study showed for the first time that an entire heart with cells, blood vessels, ventricles, and chambers could be successfully engineered and printed. The researchers first took a biopsy of fatty tissue from patients and separated the cellular and a-cellular materials of the tissue. While the cells were reprogrammed to become pluripotent stem cells, the extracellular matrix – a 3D network of extracellular macromolecules such as collagen and glycoproteins – were processed into a personalized hydrogel that served as the printing “ink.” After being mixed with the hydrogel, the cells were then robustly differentiated to cardiac or endothelial cells to create patient-specific, immune-compatible cardiac patches with blood vessels and, subsequently, an entire heart. The heart was 3D-printed in about three hours and was too small for humans. It was the size of a rabbit’s heart (~ 2.5 centimeters). But it is completely biocompatible and, most importantly, matches the patient, which reduces the chances of organ rejection inside the body. A human-sized heart might take a whole day to print and would require billions of cells, compared to the millions used to print these mini-hearts. While it’s not clear if a printer can produce hearts that are equal or superior to human ones, perhaps by printing patches there will be a possibility to improve or take out diseased areas in the heart and replace them with something that works. Researchers hope that maybe in 10 years, there will be organ printers in the finest hospitals around the world, and these procedures will be conducted routinely.

Bacterial factories for spider silk

Zhang F et al. Synthetic Biology for Microbial Production of Protein-based Materials, the American Chemical Society (ACS) National Meeting & Exposition, Spring 2019.

Spider silk has always fascinated researchers due to its lightweight and superior strength and numerous applications in areas such as drug delivery, smart textiles, and artificial muscles. It is one of the strongest natural materials in the world. It is thinner than a human hair, but its strength is more than that of steel, pound for pound. Since farming spiders is incredibly inefficient, scientists have been trying for decades to find a way to mass produce the material from genetically modified bacteria, yeast, and even goat milk, but these efforts have always fallen short. The biggest challenge was that the genetic information for dragline silk is a long string of repeating DNA, and, in previously tested organisms, cellular machinery arbitrarily alters or chops up such DNA sequences. To circumvent this problem, researchers precisely separated the repeating DNA into bits and inserted each repeating piece separately into bacterial genome. These smaller DNA pieces produced small peptides that ended up combining in bacteria and formed a strand of silk. The researchers also added to the end of each strand a chemical tag that glued the individual fibers together. This method was able to produce 2 grams of spider silk for each liter of bacteria and the resulting material behaved exactly like dragline silk. Its tensile strength was measured at 1.03 gigapascals, about the same as for naturally produced dragline silk. The engineered silk’s toughness measured 114 megajoules per cubic meter, compared with around 100 megajoules for silk made by spiders. And the engineered silk strands could stretch 18 percent before breaking, the same as natural dragline silk. The new silk was developed in part with NASA funding for applications such as giving astronauts a means of producing tough materials while on Mars. But the substance could be used in designing stronger materials for robotic, medical, or textile applications.

Electricity from falling snow

Ahmet A et al. All printable snow-based triboelectric nanogenerator. Nano Energy, April 2019.

Researchers have designed a new device with which we can now obtain electricity from falling snow. This new energy conversion method could become a new source of electricity in the future, especially in remote areas, as it does not need batteries. Researchers called it a Snow-based TriboElectric NanoGenerator, or Snow TENG. It is inexpensive, small, thin, and flexible like a sheet of plastic. After starting a charge from static electricity, energy is generated from the exchange of electrons. Snow is already positively charged by giving up its electrons, while silicone, a rubber-like material which consists of silicon atoms and oxygen atoms, is combined with carbon, hydrogen, and other elements to be negatively charged. When the positive-charged snow falls onto the surface of the silicone, the charges interact, and the Snow TENG captures the charge, which allows it to turn snowfall into electricity. 30% of Earth’s surface is covered by snow each winter, which is also the time when solar panels, one of the most reliable renewable sources of energy, aren’t very effective. Snow accumulation reduces the amount of sunlight that reaches the solar array, which makes them unable to operate. Snow TENG could be integrated into solar panels and provide a continuous power supply, even at a time when it’s snowing. Researchers used 3D printing to design the small device. It consists of a layer of silicone and an electrode which can capture the electric charge. Given that silicone is widely used in the industry, this method could dramatically reduce the global costs of producing electricity.