Spider Silk for Drug Delivery, Regenerative Medicine and Wound Healing
Authors: Rajni Singh and Shraddha Jain

Spider silk is a fiber protein made or spun by spiders. Spiders normally use their silk to make webs or other many structure and use as sticky nets to catch other animal or to wrap up prey. Spiders uses there silken threads to catch prey are amazing methods of natural engineering. The silk that spiders produce is five to six times stronger than high-grade steel by weight, stronger and more elastic than any known natural or synthetic fiber on Earth. Without breaking spider silk can stretch up to 140 percent of its length. The dragline silk's tensile strength is comparable to that of high-grade alloy steel (450 - 2000 MPa). Silks are about a sixth of the density of steel (1.3 g/cm 3). It is waterproof, does not break at temperatures as low as -40oC and ductile (able to stretch upto 40% of its length without breaking). The combination of strength and ductility gives dragline silks a very high toughness which "equals that of commercial polyaramid (aromatic nylon) filaments, which themselves are benchmarks of modern polymer fibre technology.

Types of Silk:

All spiders produce silk, but a single spider can produce up to six different types of silk for many uses.

Types Function Uses
1) major ampullate (dragline) silk It is used to construct the outer covering of the web and spokes for the lifelines. It is very strong as steel but it is tougher. It is used in making bullet-proof clothing.
2) minor ampullate silk It is a stretchable silk and it is used in temporary scaffolding during web construction. It is used in making bandages, surgical threads.
3) capture spiral silk Used for the capturing lines of web. Sticky, extremely tough. It is used in making of ropes, nets, seat belts, parachutes.
4) Aciniform silk Used to wrap or capture prey. Used to wrap or capture prey.
5) tubiliform silk This is the stiffest silk. Used for the protection of the egg sacs. Used in making wear-resistant light weight clothing.
6) Piriform silk It is the silk which is used for the construction of a stable web. It is uses in making reusable bottles.
Artificial Production of Spider Silk:

Because of the complex protein molecules (50% fibroin and sericin), repetitive DNA sequences and various compounds (used to enhance the fiber's properties) it is very difficult to artificially recreate silk. Presently, scientists are manipulating other organisms to produce same molecules of spider silk and experimenting with animals like goat, bacteria, yeasts and plants like Alfalfa, and potatoes. By insertion of specific spider genes into these organisms (gene manipulation), spider silk can be produced along with their own proteins.

Researchers have developed a process where they take a synthetic version of the spider gene that causes the spider to produce the silk protein and inject it into E. coli. The E. coli then produces the protein which is more easily extracted from the bacterium. Then the produced silk has been washed off, precipitated and freeze dried before finally ready to be dissolved to make fibers and gel. This method or technique allows the molecules to be clicked into the soluble protein silk; once they are attached the silk is converted to fibers. This technique can be used to create a biodegradable mesh.

Application of Spider Silk:

There are some medicinal properties of the spider silk. Current research in spider silk involves its potential use as an incredibly strong and versatile material. Manufactured spider silk could be used for artificial tendons and ligaments, sutures, parachutes and bulletproof vests. Spider silk is strong, biodegradable and biocompatible protein based material that does not cause a strong immune, inflammatory and allergic reaction and hence can be used to treat slow healing wounds such as diabetic ulcers.

The biodegradable mesh produced by artificial silk can do two jobs at once, one that it can replace the extra cellular matrix that our own cell generate. Second it helps in accelerating growth of the new tissue. The antibiotic levofloxacin can be added onto the silk fibers which slowly released from the fibers for at least 5 days. This technique also helps in slow release of the antibiotics. It is possible to use the silk in advance dressing for the slow treatment of wound healing such as diabetic ulcers preventing the infection over weeks and months.

The interest in spider silk is mainly due to a combination of its mechanical properties and the non-polluting way in which it is made. The researchers have found that spider webs could be used as scaffolds for regenerative damaged ligaments. Spider silk could rapidly advance the field of transplants as it triggers little, if any, immune responses which cause rejection of medical transplants. This spider web is mostly used in making bandages, surgical threads and artificial tendons or ligaments, supports for weak blood vessels along with the applicability as drug carriers.

Advantages of Spider Silk Bandages

1) The spider silk web have natural antiseptic and antifungal properties that help keep wound clean and free of infection.

2) The spider silk bandages help in quick heal because they are rich in vitamin K- clotting vitamin.

3) The bandages are not causing allergic reaction, no inflammation in people when used.

4) Used for dressing for the slow healing wound such as diabetic ulcers.

5) Spider silk bandages were used in the ancient time for cleaning up the blood because it is biodegradable.

References:

• David Harvey, Philip Bardelang, Sara L. Goodacre, Alan Cockayne, Neil R. Thomas. Antibiotic Spider Silk: Site-Specific Functionalization of Recombinant Spider Silk Using "Click" Chemistry. Advanced Materials, 2016
• Lehrstuhl Biomaterialien, Fakultat fur Ingenieurwissenschaften, Universitat Bayreuth, Universitatsstrabe 30, 95447, Bayreuth, Germany.
• Griffiths, J. R.; Salanitri, V. R. (1980). "The strength of spider silk". Journal of Materials Science. 15 (2): 491-6. Bibcode:1980JMatS..15.491G. Doi:10.1007/BF00551703


About Author / Additional Info:
I am working as Additional Director and Head in Amity Institute of Microbial Biotechnology, Amity University Uttar Pradesh, Noida, India. I have 17 patents, executed 6 different projects and authored, co-authored or presented over 50 scientific papers, articles, book and chapters and received different grants from Govt. organization to present paper at different international platforms.