Spider silk is considered one of the strongest natural materials known to man. It is five times stronger than steel on an equal weight basis. However, harvesting spider silk at an industrial scale has always been a challenge due to spiders' territorial and cannibalistic nature. Researchers are now working on developing synthetic spider silk that can replicate the incredible properties of natural spider silk through genetic engineering and biomimicry.

The Amazing Properties of Natural Spider Silk
Spider silk is known for its amazing strength, elasticity and toughness which enables spiders to spin web for catching prey and lowering from tall surfaces safely using silk. The major types of silk produced by spiders include dragline silk,Attachment fibers, and Capture fibers. Dragline silk is the toughest and strongest and forms the structure of spider web. It has a tensile strength 200 times greater than nylon. Some key properties of natural spider silk include:

- Tensile Strength: Dragline silk of Golden silk orb-weaver spiders has a tensile strength of 1.3 GPa, almost 5 times stronger than steel on a weight basis.

- Elasticity: Spider silk has an elasticity of 30%, meaning it can stretch to 30% of its original length without breaking. This allows spiders to absorb shocks from trapped insects.

- Toughness: Spider silk has an extremely high toughness value, which refers to the amount of energy absorbed before the material breaks. Some silks can absorb over 100 J/g of energy before failure which is twice as much as Kevlar.

- Transparency: Spider silk filaments are very fine, usually less than 5 micrometres in diameter, and are thus optically transparent to various degrees.

- Biodegradability: Spider silk is made of proteins and slowly degrades when exposed to humidity and microbial enzymes, making it biodegradable.

The Challenges with Traditional Harvesting of Spider Silk
While spider silk is a wonder biomaterial, massive farming of spiders for silk production is not feasible due to spiders' solitary and territorial nature. Spiders are unlikely to thrive if kept in very close proximity to one another. Also, female spiders often kill and consume the males after mating, ruling out the possibility of sustained breeding in captivity. Researchers have been exploring natural and synthetic routes to produce silk independently of spiders for decades.

Generating Spider Silk Through Genetic Engineering
In the 1990s, researchers at University of Wyoming were able to decode the genetic sequence that allows spiders to produce different types of silk. This opened up the possibility of transferring silk protein gene sequences into other organisms like bacteria, yeast, plants and silkworms which could then Synthetic Spider Silk proteins. Several approaches are now being explored:

- Transgenic Goats, Silkworms and Plants: Spider silk protein coding gene sequences have been transferred to these organisms which then produce recombinant spider silk proteins in their milk or silkworm cocoons. However, spinning these proteins into continuous fibers remains a challenge.

- Bacterial and Yeast Systems: Spider silk genes introduced in E.coli and other bacteria/yeast result in secretion of silk proteins which can then be processed into fibers. Scaling up protein production and controlling fiber assembly is still being researched.

- Cell Culture Systems: spider silk genes can be expressed in cultured mammalian, plant or insect cells which secrete silk proteins that are collected and artificially spun into fibers. Startups like Kraig Biocraft are focused on this approach.

- Synthetic Biology Methods: Researchers are developing new bioengineering methods like molecular cloning, genome editing and synthetic gene design to program microbes into highly productive spider silk "factories".

One challenge common to all biomimetic approaches is faithfully reproducing the composition and properties of natural spider silks, which are finely tuned by evolution. But significant progress is being made in this direction.

Recent Advancements in Synthetic Spider Silk Production
Over the past decade, some major advancements have been achieved in generating synthetic spider silks at larger scales:

- In 2021, researchers spun artificial spider silk fibers from yeast-produced spider silk proteins and reported mechanical properties matching natural dragline silk. Mass production in fermenters is now feasible.

- A startup called Bolt Threads developed a proprietary fermentation process in 2018 to produce their synthetic spider silk called Microsilk at commercial scales. It is claimed to be identical to natural silk.

- Kraig Biocraft developed Transgenic silkworms (2012) and moths (2021) that can produce artificial spider silk fibers continuously through their spinning glands. Scale-up is ongoing.

- Spiber, a Japanese company, has produced synthetic spider silk fibers through their recombinant bacterial system at ton-scale capacities annually since 2014 and is moving towards commercial products.

- Engineered Fiber Systems, a startup is working on producing silk proteins through genetically modified plants like tobacco and spinning them into fibers. Upscaling is still underway.

While synthetic spider silks are yet to perfectly match all properties of natural dragline silk, the materials are becoming stronger, tougher and more biomimetically accurate with every further increment of research. Full-scale commercial production of certain grades of synthetic spider silk for textiles and high-performance materials is likely within the next 5 years according to analysts. The innovation is revolutionizing sustainable production of high-strength biomaterials.

Potential Applications of Synthetic Spider Silk
Besides apparel fabrics, synthetic spider silks are projected to find multifarious applications if produced in bulk, thanks to their lightweight yet robust nature:

- Bulletproof vests, helmets and armor: Silk based materials can provide ballistic protection rivaling or surpassing existing options like Kevlar.

- Medical implants and tissues: Silks are biocompatible and can serve as scaffolds for cell and tissue growth. They are studied for ligament and tendon replacements.

- High-performance fibers: Reinforcing composites, cables, ropes and tires with silk fibers can enhance strength, toughness and durability.

- Optical and electronic devices: Transparent silk fibers enable applications in flexible displays, sensors and photovoltaics.

- Aerospace components: Light yet resilient silk composites are suited for aircraft structures, wings and engines.

- Sports gear: Fishing lines, tennis rackets, bicycle tires etc. can benefit from advanced silk materials.

To conclude, synthetic spider silk has the potential to revolutionize many industries through strong, lightweight and sustainable biomaterials. While challenges remain, innovations in genetic engineering and biomimicry are bringing this unique natural wonder within our reach.

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