Spider silk is one of the most remarkable materials in nature, combining strength, flexibility, lightness, and biodegradability.
However, harvesting spider silk from natural sources is impractical and inefficient, due to the spiders' territorial and cannibalistic behavior.
Therefore, scientists have been trying to create artificial spider silk that mimics the properties and structure of the natural fiber, using various methods such as genetic engineering, chemical synthesis, and biomimetic spinning.
The latest breakthrough in artificial spider silk production was achieved by a team of researchers from Japan's RIKEN Center for Sustainable Resource Science and RIKEN Cluster for Pioneering Research.
They have developed an artificial silk gland that can spin continuous silk fibers from a protein solution, using a microfluidic device that replicates the physical and chemical conditions of the spider's silk gland.
The Artificial Silk Gland: A Biomimetic Approach
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The key to producing artificial spider silk that resembles the natural fiber is to understand and replicate the complex molecular structure and hierarchical organization of spider silk proteins, also known as spidroins.
Spidroins are large and repetitive proteins that consist of two terminal domains and a central core domain.
The terminal domains are responsible for initiating and terminating the fiber formation, while the core domain provides the mechanical properties of the fiber.
In nature, spidroins are stored in a liquid state in the spider's silk gland, where they undergo a series of physical and chemical changes that trigger their self-assembly into solid silk fibers.
These changes include a decrease in pH, an increase in ionic strength, and a shear stress applied by the spider's spinneret.
The resulting silk fibers have a unique structure that consists of crystalline beta sheets embedded in an amorphous matrix, giving them high strength and toughness.
To mimic this natural process, the researchers from RIKEN designed a microfluidic device that consists of a narrow channel with a pH gradient and a tapered outlet. They used recombinant spidroins that they had previously engineered in bacteria, and dissolved them in an aqueous solution with a high pH.
Then, they injected the solution into the microfluidic device, where it flowed through the channel and encountered a lower pH environment.
This caused the spidroins to change their conformation and interact with each other, forming nanofibrils that aligned along the flow direction.
As the solution reached the outlet, it experienced a negative pressure and a shear stress, which further induced the fiber formation and alignment.
The resulting fibers were collected by a rotating drum, and could be spun continuously for several kilometers.
The researchers analyzed the structure and properties of the artificial silk fibers, and found that they had a similar hierarchical organization and molecular orientation as natural spider silk.
They also measured the tensile strength, toughness, and elasticity of the fibers, and found that they were comparable or superior to those of natural spider silk, as well as other synthetic and natural fibers.
Moreover, the artificial silk fibers were biocompatible and biodegradable, making them suitable for various biomedical applications.
The Potential Applications and Benefits of Artificial Spider Silk
The successful creation of artificial spider silk using a biomimetic approach opens up new possibilities for the large-scale production and utilization of this remarkable material.
One of the most promising areas where artificial spider silk could make a significant impact is the textile industry, which is currently facing many challenges and problems related to sustainability, environmental impact, and social responsibility.
The textile industry is one of the largest and most polluting industries in the world, consuming huge amounts of water, energy, and chemicals, and generating enormous amounts of waste and greenhouse gas emissions.
Additionally, the textile industry relies heavily on non-renewable and non-biodegradable materials, such as petroleum-based synthetic fibers and conventional cotton, which have negative effects on the environment and human health.
Artificial spider silk could offer a more sustainable and eco-friendly alternative to conventional fabrics, as it is derived from renewable and biodegradable sources, and does not require harsh chemicals or solvents for its production.
It could also provide superior performance and functionality, as it has exceptional mechanical properties, such as strength, toughness, elasticity, and lightness, as well as other desirable features, such as thermal insulation, moisture regulation, UV protection, and antimicrobial activity.
Moreover, the artificial spider silk could be used to create various types of textiles, such as clothing, accessories, sportswear, protective gear, medical textiles, and biotextiles, that could meet the diverse and changing needs and preferences of consumers and society.
