title: Enzymatic synthesis of catechol and hydroxyl-carboxic acid functionalized chitosan microspheres for iron overload therapy.
abstract: Excess "free" iron which occurs under certain physiological conditions participates in the formation of toxic reactive oxygen species via the "fenton" chemistry. The reactive oxygen species oxidize biomolecules and have been implicated in many oxidative stress-related diseases. However, the ideal therapy for treating iron overload problems in humans has not yet been developed. In this study, the phenolic molecules catechol, caffeic acid, and 2,5-dihydroxybenzoic acid were successfully coupled to glucosamine as model substrate in a 1:1 ratio using laccase. Furthermore, coupling of these molecules onto chitosans of different sizes was demonstrated, resulting in decrease in -NH(2) groups as quantified via derivatization. A concomitant increase in iron-chelating capacity from below 3% to up to 70% upon phenolic functionalization was measured for the chitosans based on reduced ferrozine/Fe(2+) complex formation. Interesting these phenolic compounds seems to also participate as cross-linkers in producing characteristic microspheres. This work therefore opens-up new strategies aimed at developing a new generation of iron-chelating biomedical polymers.
authors.affiliation: Institute of Environmental Biotechnology, Graz University of Technology, Graz, Austria.
authors.forename: Ivana
authors.initials: I
authors.lastname: Brzonova
authors.forename: Walter
authors.initials: W
authors.lastname: Steiner
authors.forename: Armin
authors.initials: A
authors.lastname: Zankel
authors.forename: Gibson S
authors.initials: GS
authors.lastname: Nyanhongo
authors.forename: Georg M
authors.initials: GM
authors.lastname: Guebitz
mesh_terms: D002109:Caffeic Acids / Q000737:chemistry; D002396:Catechols / Q000138:chemical synthesis / Q000737:chemistry*; D048271:Chitosan / Q000138:chemical synthesis / Q000737:chemistry*; D005841:Gentisates / Q000737:chemistry*; D005944:Glucosamine / Q000737:chemistry; D017665:Hydroxyl Radical / Q000737:chemistry*; D007501:Iron / Q000737:chemistry; D007502:Iron Chelating Agents / Q000737:chemistry*; D019190:Iron Overload / Q000188:drug therapy; D042845:Laccase / Q000737:chemistry*; D008863:Microspheres; D010084:Oxidation-Reduction; D018384:Oxidative Stress; D017382:Reactive Oxygen Species / Q000737:chemistry
chemical_list: D002109:Caffeic Acids; D002396:Catechols; D005841:Gentisates; D007502:Iron Chelating Agents; D017382:Reactive Oxygen Species; D017665:Hydroxyl Radical; D048271:Chitosan; D007501:Iron; D042845:Laccase; C034221:catechol; D005944:Glucosamine; C040048:caffeic acid; C010925:2,5-dihydroxybenzoic acid