Formation, Characterization And Application Of Oxidized Konjac Glucomannan Microspheres

Konjac has a scientific name Amorphophallus konjac, it is a kind of Acrceae Amorphophallus Perennial herb. It appeared in several provinces in China such as Sichuan, Shaanxi, Yunna, Guizhou, Hubei provinces, especially in Sichuan, which has the most abundant resources of konjac. Developing the Konjac product with high value is important for local economy of western China. Most importantly, Konjac will be a potential biomaterial for food and biomedical applications.This thesis focused on konjac glucomannan (KGM) microspheres. After TEMPO-oxidation of KGM, oxidized-KGM (O-KGM) of various degree of oxidation were prepared. The microspheres were made of ferric ions cross-linked DO80 (degree of oxidation 80%) O-KGM polymers using emulsion polymerization method. After that we characterized physical chemical properties of the microspheres and studied the gel formation mechanism. Later O-KGM microspheres were used as the drug delivery system for doxorubicin (DOX). The O-KGM microspheres are light-responsive since the cross-linker Fe3+ can be reduced into Fe2+ by light. We found that DOX can be released under light and the presence of reducing agent. The main results are as follows:1. The degree of oxidation can be precisely controlled. Different degree of oxidation of O-KGM can be obtained. The generation of carboxyl groups can be proved by the qualitative analysis by infrared spectrum. The quantity of carboxyl group can be obtained by proton titration, and there is a good linear relationship between the degree of oxidation and the amount of carboxyl groups. The results showed that the oxidation degree is accurate.2.O-KGM microspheres were prepared based on the stronger affinity between O-KGM and ferric ions rather than ferrous ions. Ferric ions was obtained from oxidation of ferrous ion, thus the gel was formed and became a 3D gel network during the oxidation process. We found that during the formation of gel network ferrous ions decreased and ferric ions increased gradually. The microsphere size shrunk along with the formation of the solid system. The zeta potential of the microspheres became more and more negative during the gel formation.3.The zeta potential of the particles became more and more negative with the increasing pH and decreasing ionic strength.4. Mossbauer spectroscopy and infrared spectroscopy analysis revealed that Fe element in the particle were ferric ions. Two kinds of COO-Fe3+ coordination modes were detected:31.6% unidentate binding and 68.4% bridge binding.5.The O-KGM nanosphreres were prepared by nanoemulsion polymerization method. We discovered that the concentration of the O-KGM, the condition of the emulsifying processing, the composition of surfactants and its HLB value had an influence on the average size of the nano-emulsion.6.Negatively charged O-KGM microspheres can adsorb positively charged DOX. The maximal amount of adsorption can reach 12 mg DOX HCL/100 mg particles.7.Ferric ion cross-linked O-KGM particles were responsive to UV light and reducing agent GSH. The release rate can be controlled by adjusting the light weave length, intensity, concentration of lactic acid and concentration of GSH added in the environment.In summary, the water solubility and functionality of KGM were improved by TEMPO oxidation. O-KGM became a potential biomaterial in food,biomedical application.