Effects of selective oxidation of chitosan on physical and biological properties.
Chitosan was selectively oxidized at C-6 primary alcohol groups by TEMPO in the presence of sodium hypochlorite (NaOCl) and sodium bromide (NaBr), and also non-specifically oxidized only by NaOCl. Sequentially oxidized chitosan samples from 25 to 100% were produced by 25% increment, from both oxidation processes. By introducing carbonyl groups in chitosan structure with either oxidizing process, the water solubility was shown to be enhancing from all the oxidized sample groups. At the 25% of non-specific oxidation, 0.56% of solubility was detected but there was no proportional increase in solubility as the oxidation level increased. Moreover, the decreases in solubility were observed at 50%-oxidized (0.43%) and 100%-oxidized (0.45%) chitosan samples. During the specific oxidation process, 25%-oxidized 6-oxychitosan had the highest solubility, and the solubility decreased substantially from 0.72 to 0.15% as the degree of oxidation increased from 25 to 100%. Possibly, excessive incorporation of negative charges on chitosan resulted in the aggregation among 6-oxychitosan molecules by charge-charge interactions. The strongest cholic acid-retardation index (CRI, %) of highly soluble 25%-oxidized 6-oxychitosan was consistently observed until 24h of dialysis, which means the CRI is closely related to the water solubility of 6-oxychitosan. Therefore, the solubility improvement should be considered for enhancing the biological activity such as bile acid-binding capacity. Also, it was suggested that negative charge increase in chitosan structure above a certain level led to adverse effect on the binding capacity.
Yoo
Sang-Ho
SH
Department of Food Science and Technology, Sejong University, 98 Gunja-Dong, Gwangjin-Gu, Seoul 143-747, South Korea.
Lee
Ji-Soo
JS
Park
Seung Young
SY
Kim
Young-Suk
YS
Chang
Pahn-Shick
PS
Lee
Hyeon Gyu
HG
D000438:Alcohols / Q000737:chemistry; D001647:Bile Acids and Salts / Q000737:chemistry; D001672:Biocompatible Materials / Q000737:chemistry*; D001965:Bromides / Q000737:chemistry; D048271:Chitosan / Q000737:chemistry*; D019826:Cholic Acid / Q000737:chemistry; D003497:Cyclic N-Oxides / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D006863:Hydrogen-Ion Concentration; D046911:Macromolecular Substances / Q000737:chemistry*; D010100:Oxygen / Q000737:chemistry* / Q000378:metabolism; D011108:Polymers / Q000737:chemistry; D017670:Sodium Compounds / Q000737:chemistry; D012973:Sodium Hypochlorite / Q000737:chemistry; D012995:Solubility; D013696:Temperature; D014867:Water / Q000737:chemistry
D000438:Alcohols; D001647:Bile Acids and Salts; D001672:Biocompatible Materials; D001965:Bromides; D003497:Cyclic N-Oxides; D046911:Macromolecular Substances; D011108:Polymers; D017670:Sodium Compounds; D014867:Water; D048271:Chitosan; D012973:Sodium Hypochlorite; D019826:Cholic Acid; C027938:sodium bromide; D010100:Oxygen; C003959:TEMPO