What is the difference between spider silk and silk?

The diameter of mulberry silk is 13- 18 micron.

The diameter of tussah silk is 2 1-30 microns.

Spider line

The diameter of thick wire is 0.93~ 1.4μm, and the diameter of thin wire is 0.56 μ m.

Study on protein silk (silk and spider silk) as medical biomaterials

The components of silk are fibroin and sericin, and sericin wraps silk. The content of silk fibroin is about 70%, sericin is about 25%, and the rest is a little carbohydrate, wax and pigment. Silk fibroin forms tiny microfibers in anti-parallel folded chain conformation (β-lamellae), then many microfibers form fine fibers with a diameter of about 1μm, and then dozens of fine fibers form silk with a diameter of 10 ~ 18 μ m. Silk fibroin and sericin contain 18 kinds of human amino acids, so silk. The mechanical properties of silk fibroin vary with its existing form, and the mechanical properties are the best when it exists in the form of fiber. The fracture micro-analysis of raw silk tensile test shows that silk fibroin membrane is brittle in dry environment and organic environment. This is one of the reasons why the mechanical properties of silk are not as good as that of spider silk.

In the past, surgical sutures were composed of polyglycerol acid organic substances, which remained in human body after operation, and then decomposed into water and CO2, which polluted human tissues. Now the surgical suture is made of silk. Silk surface is covered with a layer of silica gel, and then woven into soft spun silk suture, which has good compatibility with human body and will not produce any pollution and inflammation. Using the flexibility and permeability of silk, chitosan polymer is added to silk fibroin to make silk fibroin membrane with certain strength and elasticity, which can be used as protective film for artificial skin or silk fibroin wound. This film is elastic, not easy to break, has good adhesion and moisture permeability, and prevents wound infection. Silk can also be made into biosensors for diagnosis. Silk fibroin membrane can be used as antithrombotic medical material. The study on the mechanical properties of silk shows that its strength and stiffness are very close to those of human tendons, so it can be used in the medical treatment of artificial tendons and ligaments.

There are many kinds of spiders, and the web types of cobwebs vary widely. There are obvious differences in the diameter of spider silk. Spider web consists of three kinds of spider silk: frame silk, radial net silk and spiral hoop silk. The first two kinds of filaments are the skeleton filaments of cobwebs, which are thicker in diameter and higher in strength; The spiral wire has a smaller diameter and lower strength, and its surface is covered with mucus, which contains 80% water and is rich in amino acids. Generally, the diameter of skeleton silk is above 65438 0 μ m, and the diameter of circumferential silk is about 0.6 μ m. Sometimes spiders spin back and forth to form 5~ 10 strands in order to increase their strength. According to the experimental results of common garden spider silk provided by literature, the diameter of thick silk is 0.93~ 1.4μm, the diameter of thin silk is 0.56μm, the elongation at break is 126~ 146%, and the tensile strength is 717.5 ~1499. Microscopy shows that the molecular arrangement in spider silk is tight and orderly, and it is crystal-like, similar to the crystal structure of metal, and the molecular arrangement in some sections is similar to that of rubber. These cross sections appear alternately, which is the fundamental reason why spider silk has high strength, high elasticity and high toughness.

The disadvantages of silk are insufficient strength and limited elasticity. Spider silk has much higher strength and elasticity than silk, and it is the protein fiber with the highest strength and elasticity among the known natural animal fibers. The elongation of spider silk can reach 130% without breaking. At the same time, it also has the characteristics of moisture resistance and low temperature resistance. Spider silk can still maintain high elasticity, antibacterial and mildew resistance at the low temperature of-500 ~ 600℃. At present, spider silk is the best material for manufacturing lightweight bulletproof vests and aerial gyro suspension wires.

As early as Li Shizhen's Compendium of Materia Medica, it was recorded that spiders have medical value in treating sores, swelling, proctoptosis and other diseases. After 1980s, the Chinese Zoological Society established the "Professional Committee of Spider Zoology", and Bethune Medical University studied the medical value of spiders. At present, the medical research of spider silk is developing rapidly.