Research The Rehologic In Vitro Self-assembly Of Collagen

Collagen is a kind of extracellular matrix structure protein, It is widely exists in biological organism. Recent years,scientists have paid more attention on collagen study. Based on its good biodegradable properties, low antigenicity, biocompatibility act, collagen has been well used in the food industry, biomedical engineering and cosmetics fields. The research use channa argus acid-soluble collagen and pepsin-soluble collagen as raw materials, apply the method of rheology and its theory, targeted to carry out the system research of freshwater fish collagen self-assembly process, effect of the relative properties of the gel by rheological properties, mechanical properties, the change process of modulus value in freshwater fish collagen gel assembly process and the collagen of different conditions, sources, types was fully analysed, the self-assembly theory of natural collagen in vitro was further perfected and valuable scientific theory basis of the development and application of fish collagen in biomedical materials was provided.The method combining the turbidity and viscoelastic experiment have preliminary studied vitro self-assembly behavior of collagen in the PBS buffer system.The results show that the mode of self-assembly of collagen is divided into four stages, namely the initial stage (nucleation period), the rapid rise, slow rise and equilibrium phase.Among them, the increase rate of collagen elastic modulus in the rapidly rising stage is significantly higher than that in slow phase.At the beginning of the assembly (initial stage), collagen solution show the typical fluid perfor-mance, the viscous modulus is greater than the elastic modulus, as the extension of assembly time,both elastic modulus and viscous modulus start to rise, but the elastic modulus value increase faster and cause the appearance of the intersection between two kinds of modulus.Determining degree of self-assembly at different assembly time points respectively,the experimental results show that as assembly time extend,the degree of self-assembly are also on the rise,the degree of self-assembly reflect the new collagen fiber number increase,which shows that the correlation between the inhance of new collagen fiber number and the fast growth of collagen elastic modulus is not obvious.Results of the scanning electron microscopy in different assembly time point show that the difference of collagen fiber diameter among time points are amostly identical, the rise of collagen fiber diameter occurs mainly in the rapidly rising stage.But, the results of viscoelastic experimental show that the collagen system modulus value in the slow rise stage changes significantly, when reaching the final balance, it"s elastic modulus is almost20times as many as the end elastic modulus in rapidly rising period.From comprehensive analysis of the above results,We can find that in the collagen in the self-assembly process, the rapidly rising stage is the growth period of collagen fiber that collagen molecules orderly gather and the slow rise stage is mainly the ordering arrangement of space of collagen fibers and leads to the formation of a gel grid. Ordering and grid of collagen fiber is the most important factors of rapid increase of elastic modulus of collagen gelViscoelastic experiments under the conditions of different frequency show that as the frequency increases, the elastic and viscous modulus also will increase and lead to intersection of modulus ahead, and found that the intersection of modulus approach the gel time point after calculating greatly.TEM results show that the collagen fiber firstly have lateral growth, then longitudinal growth, near the end of rapidly rising period,the D cycle began to appear when it reach the first balance soon, collagen fiber grid form near the intersection of modulus,a large number of fibers appear behind the balance of modulus,they have formed a dense network meanwhile. By studying the different assembly conditions on the influence of collagen in vitro self-assembly. The result shows that the higher the concentration of collagen, the faster the rate of self-assembly, the higher of the gel elastic modulus value; During the denaturation temperature, the assembly speed increased with a rise of temperature, in the same time,gel elastic modulus and fiber diameter also increase; Compared with Tris, water system,PBS buffer have a significant role in promoting the collagen self-assembly behavior,this phenomenon shows that phosphate ions can promote collagen molecules aggregate;The ionic strength has inhibitory effect on collagen assemble, the greater of the ionic strength, the stronger of the repulsion, inhibiting ability stronger assembly; Among the several kinds of cationic, Ca2+assembly strongest inhibition of collagen; The higher of the pH value, the faster rate of the self-assembly, but when the value of the pH greater than10, the assembly capacity also began to decline.Used the channa argus acid-soluble collagen and pepsin-soluble collagen, grass carp skin pepsin-soluble collagen as raw material, through the method of the turbidity experiment and viscoelastic experiment to compare the different kinds and sources of self-assembly behavior of collagen. The results showed that the acid-soluble collagen is quicker than the pepsin-soluble collagen in assembly speed,so the same as the modulus;Under the same conditions,compared the channa argus pepsin-soluble collagen with the grass carp skin pepsin-soluble collagen self-assembly kinetics, shows the channa argus in the speed of assemble is quicker than grass carp, so the same as the modulus.