Alginate is slightly soluble in water and insoluble in most organic solvents. It is soluble in alkaline solution, which makes the solution sticky. Sodium alginate powder becomes wet when it meets water, and the hydration of particles makes its surface sticky. Then the particles quickly stick together to form a ball and slowly hydrate and dissolve completely. If the water contains other compounds that compete with alginate for hydration, sodium alginate is more difficult to dissolve in water. Sugar, starch or protein in water will reduce the hydration rate of sodium alginate, so it is necessary to extend the stirring time. When the concentration is higher than 0.5%, salts of monovalent cations (such as NaCl) have similar effects. The pH value of sodium alginate in 1% distilled water solution is about 7.2.
stability
Sodium alginate has hygroscopicity, and the amount of water in equilibrium depends on relative humidity. The dried sodium alginate is quite stable in a sealed container at 25℃ and below. Sodium alginate solution is stable at pH 5 ~ 9. The degree of polymerization and molecular weight are directly related to the viscosity of sodium alginate solution, and the decrease of viscosity during storage can be used to measure the degree of depolymerization of sodium alginate. The stability of sodium alginate with high polymerization degree is not as good as that of sodium alginate with low polymerization degree. It is reported that sodium alginate can be hydrolyzed by protons, which depends on time, pH and temperature. Propylene glycol alginate solution is stable at room temperature and pH 3 ~ 4. When the pH value is less than 2 or greater than 6, the viscosity will decrease rapidly even at room temperature.
Immunogenicity and biocompatibility
Sodium alginate is a natural biodegradable biopolymer. The chemical components and mitogenic impurities found in sodium alginate are the main reasons for its immunogenicity. Many reports show that implantation of sodium alginate will produce fibrosis reaction. It is known that sodium alginate may contain pyrogens, polyphenols, protein and complex carbohydrates. The existence of polyphenols is likely to be harmful to immobilized cells, while pyrogens, protein and complex carbohydrates can induce immune response in the host.
Yang prepared gelatin/sodium alginate composite absorbable sponge by a new cross-linking method. SEM observation shows that the sponge is basically homogeneous, which proves that its morphology depends on the ratio of gelatin/sodium alginate and has nothing to do with the degree of crosslinking. Although cross-linking reaction occurred, sponge was still degradable in collagenase saline buffer.
Alginate/collagen * * * mixed fiber has good biocompatibility, strong adhesion, active functions of promoting wound healing and hemostasis, and good drug and growth slow-release effects, and can be combined with local antibacterial drugs to make genetic engineering dressings for infected wounds; It can also be combined with active growth factors or active cells to make genetically engineered dressings for intractable ulcers and burn wounds. Sterile, low allergen, non-toxic and calorie-free.
The strength of alginate/(collagen) gelatin fiber is obtained by calcium ion crosslinking and polyelectrolyte effect between them. Sodium alginate can be complexed with calcium ions to form hydrogel. The main reaction mechanism is that G units are complexed and crosslinked with Ca++ to form an egg box structure, and G groups are piled up to form a crosslinked network structure, which is transformed into hydrogel fibers and precipitated. The main function of acid bath is to obtain -NH3+, because when preparing spinning solution, it is necessary to adjust the pH value of (collagen) gelatin to weak alkalinity to shield -NH3+ in (collagen) gelatin, avoid gel precipitation between (collagen) gelatin and sodium alginate, and improve their compatibility; After spinning into fibers, -NH2 of (collagen) gelatin is converted into -NH3+ in acid bath, and NH3+ and-COO-produce polyelectrolyte effect, which improves the cross-linking degree between fibers and the breaking strength of fibers.