Synthesis And Characterization Of Novel Nitric Oxide Donors Diazeniumdiolates

Chemical structures and properties of Diazeniumdiolates that make them such excellent for designing materials capable of targeting reliable and controllable fluxes of bioactive NO have become one of the forefronts and highlights of novel NO donors. The toxicity and poor biocompatibility of the nucleophile (polyamines) and the formation of potentially carcinogenic nitrosamine are the problems associated with its successful clinical application. In this dissertation, the modified products of chitosan, amino acid and glucosamine were used as biocompatible nitric oxide carrier, a series of novel diazeniumdiolates were synthesized and characteristic, and their NO release properties were investigated. The main content could be classified into five parts as follows:1. Effect of Re-acetylation and Degradation on the Chemical and Crystal Structures of Chitosan. The changes of chemical and crystal structures of the re-acetylation and degraded chitosans caused by sonication, acid hydrolysis and H2O2 oxidation were studied systematically. During the re-acetylation of chitosan, acetic anhydride can result in the degradation of chitosan when its concentration exceeds a certain value (the acetic anhydride/amine ratio > 0.3). Three crystalline polymorphs appear during the re-acetylation process of chitosans that the degree of deacetylation range from 94% to 5%. The increase of acetyl group leads to a notable crystal structure transition from crystal'formⅡ'with constrained chain conformation to'form I'having a more extended chain structure, and finally to a crystalline form similar to that of chitin. The degree of deacetylation of chitosans is not altered by sonication and acid hydrolysis, but decrease obviously because of deamination occurring in the chain scission of H2O2 oxidation. The crystallinity will increase with decreasing molecular weight for sonication and acid hydrolysis, whereas a deeper degradation by H2O2 will decrease the cystallinity.Effects of molecular weight, degree of acetylation and ionic strength on surface tension of chitosan in dilute solution. The effects of molecular weight, degree of acetylation and ionic strength on surface tension of chitosan in dilute aqueous solution were studied systematically using the maximum bubble pressure (MBP) technique. The results show that the surface tension decreases slightly with increasing chitosan concentration in the high dilution (<0.01×10-2 Kg﹒L-1), above the critical aggregation concentration (0.01×10-2 Kg﹒L-1), the surface tension...