Collagen Peptide

Fish Collagen Peptide

(The main component of animal collagen biopolymer, connective tissues)

Biopolymer, main components in animal connective tissue, functional protein in mammals is most abundant and most widely distributed, accounting for 25% of the total protein to 30%, some even as high as 80% or more organisms.

Animal tissue is the main way to obtain natural collagen and collagen peptides. However, due to the related animal diseases and certain religious beliefs, the use of collagen and its products in terrestrial mammals is now being gradually turned to marine life. The European Food Safety Authority (EFSA) has confirmed that even the source of animal bone collagen is not infected with mad cow disease and other related diseases may.

Because of the differences in amino acid composition and crosslinking degree, the rich collagen protein in aquatic animals, especially its processing waste, bone and scale, has many advantages, and the other source from marine animals is better than that of terrestrial animals. Therefore, aquatic collagen may gradually replace the terrestrial animal collagen.

There are many kinds of common types of collagen type I and type II, III, V and Xi type.

Collagen has been widely used in the fields of food, medicine, tissue engineering, cosmetics and other fields because of its good biocompatibility, biodegradability and biological activity. For example, health care products, the traditional Chinese collagen gelatin ", is the main raw material (donkey skin is actually donkey skin contains collagen), nourishing health function has a high reputation as one of the traditional Chinese medicine, sambo.

Classification

Collagen is a protein family, has been found at least 30 kinds of genes encoding collagen chains, collagen molecules can form more than 16, according to its structure, can be divided into collagen, collagen membrane, micro collagen fiber, anchoring collagen, collagen fiber, six non collagen and collagen membrane. According to their distribution and function in vivo, collagen can be divided into collagen, collagen and extracellular Zhou Jiaoyuan. Collagen type collagen protein molecules, including collagen type I, II, III type collagen protein, collagen type I mainly distributed in skin, tendons and other tissues, but also the content of water products processing waste (skin, bone and scale) protein, accounting for about 80-90%, the most widely used in medicine. Collagen type I collagen in fish in one of the most notable characteristics of thermal stability is relatively low, and showed the specificity of species. Type II collagen produced by chondrocytes; basement membrane collagen usually refers to type IV collagen, which is mainly distributed in basement membrane cells; peripheral collagen type V collagen usually refers to a large presence in the connective tissue. According to the function, collagens can be divided into two groups, the first group is the fibroblast collagen, including Chapter I, II, III, IV, Xi x x and X collagen; the other second groups, non collagen fiber. The non fibroblast collagen alpha chain contains three helices (, COL), and is also a non - three - helix domain (non - collagen, NC), which is about 90% of the total number of collagen.

Distribution

The content of collagen in aquatic animal than terrestrial animal, such as protein content of silver carp and Bighead Carp and grass carp were 25.9%, 23.6% and 29.8%, protein content was higher than that of their corresponding fish: 17.8%, 15.3% and 16.6%. The collagen content of skin can be more than the highest of the total protein of 80%, compared with other parts of the fish is much higher, there are reports of collagen protein in the skin of red sea bream accounted for 80.5%, the eel is as high as 87.3%. Such a high percentage of mean rate is high, such as small skipjack 42.5% Japanese sea bass; 40.7%; Ayu 53.6%; Yellow Sea Bream 40.1%; HorseMackerel 43.5% (based on dry weight). But the type of collagen is much less, have been isolated from fish collagen types are widely distributed in the dermis, bone, muscle, bladder scales, etc. I, cartilage and notochord type II and type XI and type V muscle. The type I collagen from skin and bone with collagen is the main. In addition, also found that collagen XVIII, however rich the content of type III collagen in mammals, have been found in aquatic animal. Only type I collagen price people can accept; other types such as collagen III, IV and V were prepared only in the study, due to the high prices are not suitable for mass production.

The relatively late XVIII collagen found, homology, and different sub categories, mainly in the lung, liver and kidney tissues. C, which is known as the multi-plexin, has a special structure that contains no (regions non-triple-heli-cal, NC1), a special structure which has a better flexibility than other collagen which is composed of only three helices. Study of collagen XVIII is mainly concentrated in the field of medicine and molecular biology, such as transcription in embryos of expression

Physical and chemical properties

Chemistry

Generally white, transparent powder, molecules are elongated, relative molecular weight ranging from about 2kD to 300kD. Collagen has very much

Collagen IR

Strong extension, insoluble in cold water, dilute acid, dilute alkali solution, with good water retention and emulsification. The collagen protein is not easy to be hydrolyzed by the general protease, but it can be broken by the animal collagenase, and the broken fragments can be automatically modified. When the environment pH is lower than the neutral, the denaturation temperature of collagen is 40~41, when the pH is acidic, the denaturation temperature of collagen is 38~39.

Collagen is a kind of amphoteric electrolyte, which depends on two factors, one side of each peptide based collagen has many acidic or alkaline; second, both ends of each peptide with alpha carboxyl and alpha amino, with proton accepting or giving ability, they can be in a specific range of pH values, dissociation have a positive or negative charge, in other words, with the collagen DSC map

The pH value of the medium, which is different from that of the medium, is an ion with many positive or negative charges. Collagen peptide side groups of the pKa value and the composition of amino acid side group pKa value is slightly different, this is because the protein molecules affected by adjacent charge. The isoelectric point is 7.5~7.8, showing alkaline, alkaline collagen peptide amino acid because of a little more than acidic amino acids. Because it is a polymer, in aqueous solution with colloid properties and a certain viscosity, viscosity at the isoelectric point, the lowest, and the lower the temperature, the greater the viscosity.

The viscosity of collagen solution with different molecular weight distribution was related to the concentration of solute, solvent, pH, temperature and the addition of electrolyte. At the isoelectric point, the viscosity of collagen solution was lowest, the pH value was lower or higher than the isoelectric point, the collagen protein and peptide were charged, the viscosity of solution increased, the viscosity of solution increased. The higher the molecular weight of collagen protein, the higher the concentration, the higher the viscosity of solution, the viscosity of polymer solution increased with the concentration increasing, while the viscosity of low molecular weight collagen solution increased with the increase of concentration.

The hydrolyzed collagen protein contains many kinds of amino acids, which is the most abundant of glycine. Followed by alanine, glutamic acid and arginine, cysteine, tryptophan, tyrosine and methionine and other essential amino acid content is low, therefore, the collagen is not complete protein. The peptide hydrolysis product of pigskin collagen contains 19 kinds of amino acids, including 7 kinds of essential amino acids and 2 kinds of adult children of essential and semi essential amino acids; the total amino acids reached as high as 90%. In eight kinds of human essential amino acids containing six: isoleucine (Ile) 1.21% (Leu), leucine and phenylalanine (Phe) was 4.89%, valine (Val) 2.95% (Thr), threonine 1.95%, lysine 1.94% (Lys).

The relative molecular weight of the collagen was big, and there were 2 bands in the 100kD. The 1 bands in the vicinity of the kD were 1 and 2, respectively. The collagen of each polypeptide chain molecular weight is 100kD, 1 collagen molecules with molecular weight of 300kD. Determination of molecular weight of peptides by SDS-PAGE, gel chromatography and mass spectrometry. Gel filtration chromatography was used to determine the molecular weight distribution of collagen hydrolysate in the process of the removal of chromium from leather. The distribution of molecular weight of collagen in the skin of the flounder was mainly concentrated in 0.6 ~ 1.8kD. The molecular weight of the collagen peptide in the hydrolysis of animal protein was 2 ~ 7kD, and the molecular weight of the collagen peptide was more than that of the protease.

The thermal stability of collagen was determined by the determination of the thermal shrinkage temperature (Ts), or the heat denaturation temperature (Td) of the molecules in the water system. The difference between Td and Td is 20 ~ 25, and the Ts value is easier to determine. Td also said the collagen helix was destroyed by the temperature, in addition to its sub amino acids (proline and hydroxyproline) is related to the content, especially the content of hydroxyproline, there is a positive correlation between them, cold water fish hydroxyproline content was the lowest, so cold water fish collagen protein Td was significantly lower than that of warm water fish, and are lower than the land animal. But the fish skin collagen and collagen compared to the dermal Td to 1 DEG C lower than muscle, and the muscle collagen proline hydroxylation rate is high on the dermal collagen. There are a variety of amino acid composition of fish soluble collagen was determined, and compared with all amino acids, found in fish skin collagen hydroxyproline and proline imidic acid content than low leather. In addition, compared with the leather skin gelatin gelatin, its inherent viscosity and thermal denaturation temperature were relatively low.

 Hydrolyzed collagen and collagen polypeptides are not the same, can be considered to be the macro and micro relations. Collagen molecules are mainly formed by the hydrolysis of collagen polypeptide, because of the unique structure of three strands of collagen, which is very stable. The processing temperature and short time can not be decomposed. After hydrolysis, the absorption rate of the absorption can be increased, and the absorption of other proteins in food can be promoted. In addition to the ends of the collagen polypeptide peptide containing terminal carboxyl and amino no condensation, in the side chain also contains Lys and Asp e -NH2 and Glu -COOH. Collagen polypeptides can be completely dissolved in water (cold water can also be dissolved), water solution with low viscosity, the high concentration of 60% also has the mobility, good acid and alkali resistance, in the presence of acid, alkali, no precipitation; high temperature performance is good, 200 is no precipitation, but it also has good oil absorption, foaming and water absorption, etc..

Structure

 Extraction and separation

Because collagen is the extracellular matrix in vivo in insoluble macromolecular structure, and proteoglycan, glycoprotein etc. together, so the separation of collagen preparation including material selection, pretreatment, extraction, enzyme alkali brine method and purification of different types of collagen. 

Pretreatment

In addition to collagen, animal bones also contain oil, a variety of minerals and other impurities, so it must be pre processed before being used to extract collagen. Remove the remnants of animal bones and tendons and other debris, after crushing with normal butanol or hexane extract bone oil. Finally remove the inorganic substance in the bone to increase the rate of collagen. Removing minerals from the bone may be available for dilute acid or EDTA solution. Some people use raw materials in 5 times the mass of 1.0moL/LHCL 2D with n-hexane decalcification, and pepsin after degreasing, 150U/g in the amount of enzyme, pH value of 1.7 120min at 37 DEG C, and then at the solid-liquid ratio of 1: 6 case was 5h, under this condition, the extraction rate can reach 18%; and people with EDTA solution (pH7.4) for aggregate 5D, can effectively remove hydroxyapatite in aggregate.

There are three methods of extracting collagen: one is the physical method of high pressure; the two is the chemical method of the combination of Solvent Pretreatment with low temperature or hot water extraction. In general, high pressure and hot water extraction for the extraction of gelatin, and low temperature extraction and enzymatic method for the extraction of collagen, but its basic principle is based on the characteristics of collagen protein in the external environment, the collagen protein isolated from other proteins.

In the actual process of extraction, the different extraction methods are often combined with each other, which can get better results. High pressure treatment system was used to give high pressure treatment for a period of time, so that the structure and collagen of the three strands of the structure of the structure of the loose, degeneration, ease of separation and extraction.

water law

Hot water extraction method is used to extract the raw material after the treatment, and then directly under a certain condition, the water extract has been denatured collagen or water extract collagen protein hydrolysate, the use of temperature is 100 degrees Celsius boiling water bath, 60-70, 40-45.

Acid method

Acid extraction is the use of certain concentration of acid solution under certain conditions to extract collagen protein, mainly by the use of low concentrations of acidic conditions for the extraction of collagen protein salt bond and Schiff base, which caused by fiber expansion, dissolution, the use of acid extraction of collagen protein often become acid soluble collagen. Collagen molecules can be dissolved by acid dissolved out without cross-linking, can also be dissolved with aldehyde amine cross-linking of collagen fibers, and then released to the solvent. Acid extraction method is a common and effective method to extract collagen protein, and the maximum degree of collagen extracted by low temperature acid method is the most common and effective method. The usual practice is the proper concentration of acid solution according to a certain ratio of material to liquid added to the pretreated bone, in 0 to 25 DEG C, stirring extraction time. In the use of acid method for the extraction of collagen, attention should be paid to the extraction temperature is not too high, so as to avoid the destruction of collagen biological activity. The collagen acid-soluble (ASC) was obtained by using acid leaching solution at low temperature after the sample was treated. Acid, phosphoric acid, formic acid, acetic acid, malic acid, citric acid and so on, but most of the research concentrated on the extraction of bone collagen, such as Sadowska Maria and 0.5mol/L. Citric acid is not produced by color and odor can be used extensively in the food industry, the extraction of collagen protein.

 Enzymatic extraction refers to soluble and acid soluble collagen was extracted, with some proteases, such as collagenase, pepsin, papain and collagen gel electrophoresis after salting out chymotrypsin hydrolysis, different enzyme soluble collagen. The use of protease is mainly divided into 3 types: Animal proteases (such as trypsin, pepsin), plant proteases (such as papain, bromelain), microbial protease (such as alkaline protease, neutral protease). In the study of enzymatic hydrolysis of collagen, the application of alkaline protease was the most.

 The restriction to collagen degradation, terminal peptide cutting down, due to the covalent bond between the collagen peptide is formed by molecular terminal peptide in lysine and hydroxylysine interacting amino acids, peptides were cut off after the end, the main part of the content of soluble three helix structure in rare organic acid by extraction out. With the enzyme treatment, the collagen protein can be hydrolyzed to the end peptide, improve the yield of collagen, and it will not destroy the collagen of the three strands of spiral structure, maintain its characteristics. There are many factors that affect the enzyme extraction, such as the ratio of enzyme concentration, enzyme to substrate, the time of enzyme hydrolysis, the temperature of hydrolysis, pH value and the ratio of material to liquid. In practice, most of the enzymatic extraction of 

Purification

Can be used for purification methods including salting out, dialysis and centrifugation, electrophoresis and chromatography of collagen, the salting out method, centrifugation and electrophoresis is the most commonly used. Because the single method can not be completely separated and purified collagen, the actual operation is achieved by the composite method to achieve the purpose of separation and purification of collagen. Salting out method commonly used high concentration NaCl; centrifugation was used for preparing Supercentrifuge; electrophoresis with polyacrylamide gel electrophoresis of twelve alkyl sodium sulfate (SDS-PAGE), this method can be used for separation and purification of the collagen, can also be used to determine the relative molecular mass of collagen molecules. Like a crushing, enzymolysis, salting out three step purification of Sunite sheep bone collagen type I with people. After removing non collagen material in bone, and then to 10% of the precipitation of pepsin, at the temperature of 4 DEG C to 14000r/min 24h digestion, centrifugal 40min. NaCL, so that the final concentration of I in the supernatant reached 0.9moL/L, resting for the night, then centrifuge, the final deposition is the type of collagen type.

Modified

 Cross-linking

The method of increasing the tension and stability of the collagen fibers by covalent bond between the inner and the molecules of the collagen molecules. This method is divided into physical method, chemical method and low temperature plasma method, biological method, physical method and chemical method is the most commonly used method of cross linking modification.

 Physical method

By physical means, the collagen modified by UV irradiation, severe dehydration, and thermal crosslinking, and other methods. Collagen solution, such as UV irradiation, will be in the intermolecular cross-linking, viscosity increased, the formation of gel. The commonly used method of UV cross-linking collagen membrane is to put the collagen membrane on the aluminum foil, the distance of 254 cm ultraviolet lamp 20 nm height, irradiation 1 ~ 5 h. The mechanical properties and collagenase test showed that the mechanical properties and the ability of the Ts and the ability to resist collagenase were significantly higher than those of the non crosslinked collagen membrane.

Severe dehydration is a common method used in the physical modification of collagen, which is caused by dehydration of collagen molecules, thus increasing the temperature and improving the properties of collagen. The biocompatibility of the modified collagen membrane was improved, which reduced the water solubility, and affected the biocompatibility of the membrane and osteoblasts. The advantage of physical method to modify the original protein is to avoid the exogenous toxic chemicals into the collagen, the disadvantage is the low degree of cross-linking of collagen membrane, and it is difficult to obtain uniform and consistent cross linking.

Chemical method

Chemical method is more effective than physical method, and it can get a uniform and consistent link, which is effective in regulating and controlling the properties of collagen. Has been widely used in various chemical reagents to cross link collagen, in order to improve the degree of crosslinking, mechanical properties and biocompatibility. Chemical modification method can be divided into three kinds of methods, which use chemical reagent, side chain modification and physiological activity.

Chemical reagent, which is commonly used in chemical reagents, has glutaraldehyde, isocyanate, two, two, and two phenyl phosphate. Among them glutaraldehyde is the most widely used reagent. In addition, with the increase of crosslinking degree, water absorption capacity and the expansion degree will be decreased. Acyl azide, polyepoxide or genipin, no obvious toxicity, and can obtain the ideal effect of crosslinking. In the report, the use of single crosslinking agent on the collagen crosslinking modification, but also the use of mixed crosslinking agent, such as to solve the problem of artificial heart valve calcification, the method of chemical modified glutaraldehyde modified glutaraldehyde treatment of biological valve, can significantly reduce the content of collagen in the valve group. Animal experiments show that the modified valve tissue can maintain good tissue stability and mechanical tensile strength, immunogenicity test is negative, in accordance with clinical application.

Side chain modification is to modify the amino and carboxyl groups on the side chains of the collagen molecules, improve the charge distribution, so that the new characteristics of collagen, such as the collagen amino group two, can be changed into a negative charge. Compared with the non modified collagen, platelet adhesion, fibrin formation can be weak, there are anti thrombus; however, the collagen carboxyl methylation is obtained by the positive charge of collagen, platelet adhesion energy, activation energy. In the field of biomaterials, the use of side chain modification in the field of biological materials is less than that in the modification of collagen.

Although the chemical method can obtain uniform and uniform crosslinking, but there are disadvantages of introducing the foreign toxic reagent, the residual reagent is difficult to remove. Some reports indicate that the low temperature plasma technology modified collagen or collagen composite membrane can make the material surface to introduce different groups, change the surface chemical composition and structure, so as to change the material properties, such as to make it more cell recognition, improve the surface energy, improve the surface polarity, etc..

And other polymer blends

Collagen alone, physical and mechanical properties (which is almost a common weakness in natural materials), the performance of a single, and because of the strong hydrophilic, in the body is easy to be collagenase degradation and other inevitable weaknesses limit its application. But if the collagen and other physical and chemical properties of different synthetic or natural polymer blend, a multiphase solid materials, in the performance of collagen and other polymer complement each other, the collagen based composite material concept.

It has been reported that the synthesis of polymer with collagen blend has the non biodegradable poly methyl ester, maleic acid ester, polyurethane, polyamide and biodegradable polyvinyl alcohol, poly lactic acid, poly (lactic acid), poly (vinyl alcohol) and polyvinyl alcohol (PHEMA), which is the most representative in the 80 to 90 years. Then the biodegradable polylactic acid, polyglycolic acid, poly acid anhydride, poly glutamic acid, ethyl acetate and four poly collagen blend modified preparation of absorbable surgical suture, tissue engineering scaffold materials (such as guided tissue regeneration materials) related research relative increase. However, synthetic polymer and collagen composite some problems, such as nylon and other non degradable polymer materials can not carry out physiological metabolism, and collagen composite can only be used to make skin, and can not permanently replace the skin, while the other biodegradable materials, such as fruit relative molecular weight is not enough, the relative molecular weight is difficult to dissolve in water, dissolved also appear degradation, affecting the mechanical strength of the material.

Natural polymer material is the most representative of natural protein and natural polysaccharides, polysaccharides are mainly chondroitin and HA (hyaluronic acid), chitosan, heparin, polysaccharide composite materials are relatively concentrated in the absorbable surgical sutures, drug delivery carrier, skin substitute, dialysis membrane, hemostatic agent, medical guided tissue regeneration, bone substitute material, tissue culture system support.

Biological character

Low immunogenicity

Collagen is a medical biomaterial, the most important feature is its low immunogenicity, and other proteins with immunogenicity compared to the immune response of collagen protein collagen protein clinical application is very low. It was even thought that collagen was not of the antigen, and the research showed that the collagen had a low immunogenicity, and the immunogenicity was especially low when the peptide was not included. There are three types of collagen protein, peptide end first is non helical collagen peptide chain, exist in native and denatured collagen. Because of the high degree of evolutionary stability, the three helix region of the 2 different kinds of mammals has a high degree of evolutionary stability, but in this region almost 50% of the amino acid residues show different properties. The second category is the conformation of the three strands of collagen, which is only present in the natural collagen molecule, which is located in the three helix structure of collagen, which is exposed in the process of separation and purification, especially in the central end of the 2 single chain exposure. The third category is the order of amino acids in the chain of the chain, but only in the collagen. Immunological analysis and research results show that the use of collagen and complete with the adjuvant, can produce a number of collagen and monoclonal antibodies. The immune response of T cells to collagen was identified by the response of the H-2 cells to collagen, and the immune response of the immune response genes in the A or B region was identified. The clinical evaluation of the immunogenicity of collagen protein is usually a skin allergy test (cellular immune index, delayed type IV response) and the presence of reactive antibodies (humoral immune index) to determine the. It is proved that the two evaluation is reasonable in patients. Before treatment, patients with allergic skin test dose of implanted collagen, about 3% potential reactions, repeated treatment of patients, about 1% to 2% will have clinical symptoms of tardive hypersensitivity, typical symptoms include edema and erythema reaction, sometimes accompanied by hardening and itching, duration 4 to 6 months, some even up to 1 years.

Compatibility

Biocompatibility refers to the interaction between collagen and host cells and tissues. The collagen itself is a skeleton of the extracellular matrix, and the fiber or network formed by the structure of the strands and the cross-linked network plays a role in anchoring and supporting cells, and provides a suitable microenvironment for cell growth. As the skeleton of the new organization, it is absorbed and assimilated into the host as a part of the host. It has a good interaction with the surrounding matrix, which is a part of the whole cell and the normal physiological function of cells. For example, sponge type I collagen and rabbit adipose stem cells have good in vitro biocompatibility, can provide suitable three-dimensional space for tissue engineering seed cells, can be used as the carrier materials of the fat tissue engineering seed cells.

Biodegradable property

Collagen can be degraded by a specific protease, that is, biodegradation. Because collagen has a spiral structure closely, so the vast majority of protease can only cut off the side chain, only the collagenase and elastase specific proteases to degrade collagen in certain conditions, the fracture of collagen peptide. Collagen peptide bond is broken, then the spiral structure was destroyed and completely hydrolyzed into small peptides or amino acids, small molecules can enter the bloodstream, recycling or excretion by the body. Biodegradable is the basis for the use of collagen protein can be used for organ transplantation.

Coagulation

Collagen has the function of hemostasis, the performance of the play through two aspects, that is, to promote platelet aggregation and plasma agglomeration. Collagen can be formed by adhesion and aggregation of platelets to stop bleeding. When the endothelial cells of the blood vessel wall are stripped, the collagen fibers in the blood are exposed to the blood, and the blood platelets immediately and the collagen fibers are adsorbed together. Collagen of the natural structure of collagen has the ability to gather the foundation. Collagen is the major structural protein involved in wound healing. Hemostatic activity depends on the size of the collagen aggregates and the molecular structure of the native structure, and the degeneration of collagen (gelatin) induces hemostasis. Studies show that collagen can effectively induce platelet aggregation, compared with the two camp, collagen induced by the initial dose, concentration and other factors, the performance is rapid and thorough.

Application

Biomedical materials:

Collagen is a natural protein in the body, on the surface of the skin protein molecule has a strong affinity, weak antigenicity, good biocompatibility and biological degradation of safety, biodegradable, good adhesion. Surgical suture by collagen made of both high strength and natural silk, and absorbable, when using both excellent platelet aggregation properties, good hemostatic effect, but also has better smoothness and elasticity, suture knot is not easy to loose, not easy to damage the body tissue during the operation, there are very good adhesion to the wound, pressure needed only a short time under normal circumstances can achieve satisfactory hemostasis. So collagen can be made into powder, flat and sponge like hemostatic agent. At the same time, the research and application of synthetic materials or collagen in the repair of plasma substitutes, artificial skin, artificial blood vessels, bone and artificial bone and immobilized enzyme carrier and other aspects are very extensive.

With a variety of reactive groups of collagen peptide, such as hydroxyl, carboxyl and amino, easily absorbed and combined with a variety of enzymes and cells, the solid collagen medical products in clinical application of it has the characteristics of good affinity, strong adaptability and enzyme and cell. In addition, collagen is easy to process, so the collagen can be made into many different forms of material, such as film, tape, film, sponge, beads, etc., but in the form of membrane application of the report. Preparation of collagen membrane for biomedical, besides the biodegradability, tissue compatibility, weak antigenicity and biological absorption, also include: strong hydrophilicity, high tensile strength, morphology is similar to dermis, permeability is good; high resistance to biological plastic tensile strength and low ductility decision; functional groups many can moderate crosslinking modification, which can control the rate of biodegradation; adjustable dissolved (swelling); and other bioactive components used together have a synergistic effect; it can interact with drugs; crosslinking or enzyme treatment to end peptides can make the antigenicity reducing, isolating microorganisms, physiological activity if the blood coagulation effect etc.. There are also the following shortcomings: the separation and purification of collagen and the complexity of processing, the density of collagen, the size of the fiber, and so on. Collagen enzymolysis speed changing, it is difficult to control conditions; and the pure collagen dry crisp texture, film-forming ability is not strong, the film of low ductility, easy to crack, poor water resistance, easy water swelling, the in vivo degradation in damp environment and susceptible to bacterial erosion and deterioration, moreover may also lead to some side effects, such as tissue calcification. In practical application, it is often through a certain method to modify collagen protein, through the modification of collagen to avoid the shortcomings of the material, improve the tensile strength and anti degradation ability, reduce the expansion rate, improve the mechanical properties and water resistance. Clinical application form of water solution, gel, granules, sponge and film, etc.. The same shape can be used for drug delivery, has approved the release of collagen and collagen drug delivery applications are being developed, mostly concentrated in the Department of Ophthalmology, anti infection and glaucoma treatment, local treatment and wound repair in the treatment of infection, and the Department of cervical dysplasia and surgical local anesthesia, etc..

Tissue engineering

Because collagen is widely distributed in various tissues of human body, the important component of the system is composed of Extracelluarmatrix (ECM), which is a kind of natural tissue scaffold material. From the point of view of clinical application, people made a variety of tissue engineering. However, in the case of collagen itself, there are two major categories, namely, the scaffold of pure collagen, and the composite scaffold with other ingredients. Pure collagen scaffolds have good biocompatibility, easy processing, plasticity and can promote cell adhesion, proliferation and other advantages, but also has the mechanical properties of collagen, is shaping in the water, unable to support the reconstruction of tissue deficiency. Second, the new tissue in the repair department will produce a wide variety of enzymes, the collagen hydrolysis, lead to the collapse of the scaffold, and the use of crosslinking or composite approach can improve and improve. It has been successfully used in artificial skin, artificial bone, artificial bone, cartilage transplantation, nerve conduit and other tissue engineering products. It was used to repair cartilage defects and to try to use epithelial, endothelial and corneal cells attached to the collagen sponge to adapt to the corneal tissue. There are also human mixed autologous mesenchymal stem cells in the mesenchymal cells and collagen gel for the production of tendons for tendon repair. Collagen protein as the main component of the tissue engineered artificial skin drug delivery system is widely used. It can be used to form various forms of drug delivery system, such as collagen sponge, collagen gel, collagen gel, and gene delivery. In addition, it can be used as the matrix, artificial blood vessel and valve of the tissue engineering including cell culture system.

Burn

Autologous skin grafting has been a global standard for treating two degrees and three degrees burn. However, for severely burned patients, the lack of suitable skin cells can be the most serious problem. There is a lack of autologous transplantation for the treatment of skin tissue, which can be cured by the use of biological engineering technology. The collagen tissue can be cured in 3 weeks and 18 months. There are artificial synthetic poly -DL- lactic acid (PLGA) and natural collagen to cultivate three-dimensional human skin fibroblast cells, the results showed that the cells grow faster on the synthetic mesh, and the proliferation of cells and the secretion of extracellular matrix is more uniform, this fiber is implanted in the back of the skin without skin, 2 weeks after a long dermal tissue, 4 weeks after the epithelial tissue.

Cosmetology

Collagen extraction from animal skin, skin in addition to collagen also contain hyaluronic acid and chondroitin proteoglycan, they contain a large number of polar groups, is a moisturizing factor, and prevent skin tyrosine into melanin, so the collagen has pure natural moisturizing, whitening, wrinkle, freckle effect. Can be widely used in cosmetic products. The chemical composition and structure of the collagen are the basis of beauty. The structure of collagen and collagen in human skin is similar to that of the non water soluble sugar containing fibrous protein, rich in amino acids and hydrophilic molecules, has certain surface activity and good compatibility, and because its molecule contains a large number of hydroxyl groups, so it is a good moisturizing effect. In the relative humidity of 70%, still can maintain its own weight of 45% of the water. 0.01% of collagen can form a very good water retention layer, with the growth of the age, the ability to reduce the synthesis of fibroblasts, if the lack of collagen, collagen fibers will occur, so that the cell adhesion and more sugar reduction, the skin will lose soft, elastic and shiny, aging, while the fiber fracture, fat atrophy, sweat glands and sebaceous gland secretion decreased, so that the skin pigmentation, wrinkles and a series of aging phenomenon. As active substance used in cosmetics, the latter can spread to the skin deep, which contains tyrosine and tyrosine in the skin, and the catalytic center of tyrosinase, thus inhibiting the production of melanin, so that the skin collagen activity, maintain the integrity of the stratum corneum moisture and fiber structure, promote the metabolism of skin tissue, the skin to produce a good moisturizing, wrinkle beauty effect. In early 1970s, the United States launched the first injection of bovine collagen, except for freckle wrinkles and scar repair. However, in cosmetics, the use of raw materials for nutritional care is usually required in the amount of molecular weight in the 2KD, in order to allow the hydrolysis of collagen can penetrate into the skin. The hair care cosmetics in addition to the requirements of the hydrolysis of collagen with moisture, but also should have a certain amount of film, so that the molecular weight of hydrolyzed collagen will be higher.

Food

Collagen can also be used in food, as early as in twelfth Century, St.Hilde-gard Bingen described the use of calf's cartilage soup as a drug to treat joint pain, for a long time, some products containing collagen is considered to be very beneficial to the joint. Because it has a number of properties for food: food grade is usually white, soft, light, easy to digest. Can reduce blood triglyceride and cholesterol, and can increase the body of certain lack of essential trace elements to make it in a relatively normal range, it is a kind of ideal for lowering blood lipids food. In addition, studies have shown that collagen can help rid the body of aluminum, reduce the aluminum accumulation in the body, reduce both the harm to human body, and to a certain extent, promote the growth of hair and nails. Type II collagen is the main protein in articular cartilage, which is a potential self antigen. T cells can induce immune tolerance, which can inhibit T cell mediated autoimmune diseases. Collagen peptide is collagen or gelatin by protease degradation after prepared with high absorption and the molecular weight is about 2000 ~ 30000 of the product, does not have the gel properties of gelatin, sold on the market for collagen collagen polypeptide.

Some quality collagen makes it in many food used as functional material and nutrients with other alternative materials incomparable advantages: helical structure of collagen molecules and crystalline region which has certain thermal stability; natural collagen close fiber structure showed strong toughness and strength of the rubber raw materials, application in the fabrication of films; the hydrophilic groups containing a large amount of collagen on the molecular chain, so the ability to combine with water is very strong, the nature of the collagen in the food can be used as a filler and collagen gel; swelling in acidic and alkaline medium, process of this nature is also used in the preparation of collagen based materials in.

Collagen powder can be directly added to the meat products, in order to affect the meat tenderness and texture of meat after cooking. Research shows that the formation of collagen protein in the meat and cooking meat is very important, the higher the collagen content, the more hard the meat texture. Like meat tenderization is thought to be related to type V collagen degradation caused by the destruction of cells in the peripheral peptide cleavage of collagen fibers is considered to be the main reason of muscle tenderness phenomenon. By breaking the hydrogen bonds in the collagen molecules, the structure of the compact structure is destroyed, the formation of small molecules and the structure of the gelatin can improve the quality and increase the protein content. Japan also developed animal collagen was prepared by collagenase hydrolysis, modulation and developed a new type of spices and wine, not only has a special flavor, but also add some amino acids. With all kinds of sausage products for meat products in an increasingly large proportion, the serious lack of natural casing products. Researchers are committed to the development of alternatives, with collagen as the main collagen casing itself is high protein nutritious substances, in the heat treatment process with evaporation and melting of water and oil, collagen is almost consistent with the shrinkage of the meat dish, and other edible packaging materials have not been found to have this quality. In addition, collagen protein itself has the function of the immobilized enzyme, which has antioxidant properties, it can improve the flavor and quality of food. Product stress is proportional to the amount of collagen, and the strain is inversely proportional to the amount of strain.

Bones

Collagen is an important component of human bone, especially in the cartilage tissue. Collagen is like a piece of bone in a small hole in the net, it will firmly keep the loss of calcium. No such a small hole in the net, even if it is added to the excess of calcium, will be lost in vain. The characteristic amino acid hydroxyl proline is a tool for transporting calcium to bone cells in plasma. Bone cells in collagen hydroxyapatite and hydroxyapatite adhesive, it constitutes the skeleton body. But the essence of osteoporosis is the synthesis of bone collagen could not keep pace with the need, in other words, the generation rate of new bone collagen than the old collagen variation or aging speed. Studies have indicated that, if the lack of collagen, supplement and more calcium can not prevent osteoporosis, therefore, only the intake of adequate calcium and collagen, can make calcium in the body is rapidly digested and absorbed, and can quickly reach the bone site and deposition.

-PVP polymer (C-PVP) was prepared in the citric acid buffer solution. The results showed that the reinforcement of the injured bone was good, safe and high, even if the long period of continuous use, whether it is the experimental or clinical trials are not showing lymph nodes, DNA damage, will not cause liver and kidney metabolic disorders, but also does not induce the body to produce anti PVP C- antibody.