Changdao Mu

Ultrasonic irradiation in the enzymatic extraction of collagen.

The application of ultrasonic irradiation (40KHz, 120W) in the enzymatic extraction of bovine tendon collagen has been investigated. Our results show that using the ultrasonic irradiation increases the yield of collagen up to approximately 124% and significantly shortens the extraction time in comparison with the conventional pepsin isolation method. Such improvements are attributed to the enhancement of the enzyme activity and the dissolution of collagen substrate because the ultrasonic irradiation disperses the pepsin aggregates and opens up the collagen fibrils, thus the enzymatic hydrolysis is facilitated. AFM imaging shows the same fibrillar structure of tendon collagens generated from both the methods. The CD and FT-IR measurements reveal that the triple helix structure of collagen remains intact even after the ultrasonic irradiation. This study shows that the mild ultrasound irradiation can effectively improve the efficiency of pepsin extraction of natural collagen without any compromise of the resultant collagen quality.

Preparation, physicochemical characterization and release behavior of the inclusion complex of trans-anethole and β-cyclodextrin

Trans-anethole (AT) has a variety of antimicrobial properties and is widely used as food functional ingredient. However, the applications of AT are limited due to its low water solubility, strong odor and low physicochemical stability. Therefore, the aim of this work was to encapsulate AT with β-cyclodextrin (β-CD) for obtaining inclusion complex by co-precipitation method. The measurements effectively confirmed the formation of inclusion complex between AT and β-CD. The results showed that the inclusion complex presented new solid crystalline phases and was more thermally stable than the physical mixture and β-CD. The phase solubility study showed that the aqueous solubility of AT was increased by being included in β-CD. The calculated stability constant of inclusion complex was 1195M-1, indicating the strong interaction between AT and β-CD. Furthermore, the release study suggested that β-CD provided the protection for AT against evaporation. The release behavior of AT from the inclusion complex was controlled.

Ring‐opening polymerization of genipin and its long‐range crosslinking effect on collagen hydrogel

Polymeric genipin macromers, prepared by ring-opening polymerization at various pH values, are used as crosslinking agents to fix collagen hydrogels. The results indicate that as the dark color of polymeric genipin itself and the networks formed by long-range intermolecular crosslinking, the genipin-fixed collagen hydrogels displace darker color. The polymeric genipin prepared at higher pH value needs longer time to fully crosslink with collagen molecules. Moreover, polymerization of genipin reduces the yield of genipin-fixed collagen hydrogels due to low extent of crosslinking. Specially, the microscope photographs present the porous networks structures of genipin-fixed collagen hydrogels. The pore size increases with the increase in polymerization degree of genipin. The data of FTIR indicate the likely transition of -NH(2) groups in collagen chains into C=N. Owning to much more number of hydrophilic groups and more porous networks, collagen hydrogels fixed by genipin with higher polymerization degree have higher water absorption capacity. The equilibrium swelling of genipin-fixed collagen hydrogels is pH-responsive, which show M type changes with the pH values. The results obtained in the study suggest that the polymeric genipin prepared at various pH values lead to significant influence to the crosslinking characteristics and properties of collagen hydrogels.

Short-range and long-range cross-linking effects of polygenipin on gelatin-based composite materials.

Genipin is an ideal cross-linking agent in biomedical applications, which can undergo ring-opening polymerization in alkaline condition. The polygenipin can create short-range and long-range intermolecular cross-linking between protein chains. In this article, the polygenipin with different degree of polymerization was successfully prepared and used to fix gelatin composite materials. The short-range and long-range cross-linking effects of polygenipin were systematically studied. The results show that the composite materials present porous structure with tunable pore sizes in the gel state, which can be easily controlled by adjusting the degree of polymerization of polygenipin. Long-range cross-linking can increase the pore size of the gel. However, during the drying process, the composite films cross-linked by polygenipin with higher degree of polymerization shrank to smaller size to create more compact structure, resulting in the improvement of water resistance properties, thermal stability, tensile strength, and darker color for the composite films. It is interesting that the composite films can partly swell to the original gel structure when in contact with water and saturated water vapor. All the composite films have excellent barrier properties against UV light. However, the compatibility of gelatin and polygenipin is reduced when the degree of polymerization of polygenipin increases to a certain extent, which will result in the formation of phase separation structure. The obtained composite films are ideal candidates for food and pharmaceutical packaging materials.