Polysaccharides cross-linked, heterogeneous

The network structure of gels is generally highly heterogeneous from the structural and dynamic points of view. The existence of solid-like domains from the cross-linked region is characteristic of the formation of the gel network. Such a domain in polysaccharide gels is ascribed to formation of cross-links due to the physical association of chains adopting an ordered conformation. It is now obvious that the secondary structure of such ordered polysaccharide chains is readily determined on the basis of the conformation-... 

Heterogeneous, cross-linked polysaccharides containing dissimilar polysaccharides have been produced by treating such glycosaminogly-curonans as chondroitin sulfate, dermatan sulfate, and heparin with cyclic imidocarbonate derivatives of agarose (Sepharose). The cross-linking is probably mediated by the nucleophilic attack of a free amino group... 

These relationships used in the theory of elasticity and developed for ideal networks make it possible to determine the degree of polysaccharide reticulation and establish the maximal degree of cross-linking in the hyaluronan gel, after which its injection into derma becomes technically impossible. Specifically, this determines comparatively short (up to half a year) times of the correction of the skin volume changes by intradermal administration of the cross-linked HA-based monophase (homogeneons) fillers. The solution to the problem of increasing the duration of correction lies in the field of biphase (heterogeneous) micro-implant administration. 

Chitin, one of the most abundantly available natural polysaccharides, can be readily modified by acetylation reactions to form chitosan (CHI) [37]. CHI was modified with the four-member oxetane (OXE), followed by cross-Hnking with trifunctional hexamethylene di-isocyanate (HDI) in the presence of polyethylene glycol to form heterogeneous cross-linked polyurethane (PUR) network. When there is mechanical damage of the network, self-repairing occurs upon exposure of the damaged area to UV radiation. While the reactions leading to network formation are shown... 

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