Biodegradable poly(3-hydroxyalkanoate)s & fullerene-derived drugs

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Biodegradable poly(3-hydroxyalkanoate)s & fullerene-derived drugs


Author: He, Jidong
Title: Biodegradable poly(3-hydroxyalkanoate)s & fullerene-derived drugs
Degree: Ph.D.
Year: 2005
Subject: Hong Kong Polytechnic University -- Dissertations.
Polymeric drug delivery systems.
Antibacterial agents.
Department: Dept. of Applied Biology and Chemical Technology
Pages: xvii, 106 leaves : ill. ; 30 cm.
Language: English
InnoPac Record:
Abstract: The major objectives of this dissertation are to assess the structure-properties relationships of (1) polyhydroxyalkanoates (PHAs), and of (2) a new water-soluble [60]fullerol synthesized by me that has potential as a therapeutic agent. PHAs are biodegradable polyesters that can be synthesized from renewable sources by numerous bacteria. There is considerable potential for the design of PHAs for applications in drug delivery. PHB, P(HB-HV), and P(HB-HHx) are the most commonly found members of the PHA family. PHB has a narrow thermal processing window. However, the properties of P(HB-HV) and P(HB-HHx) vary widely depending on the mole percentage of HV and HHx in the copolymers. So it is important to determine the thermal properties in order to improve the thermal processing of these biopolymers. Water-soluble C60 derivatives can interact with DNA, proteins and living cells. Due to their photochemistry and radical quenching, multiple hydroxyl water-soluble fullerol will have abroad clinical applications including drug synthesis. In the first part of the experiment, thermal analyses of PHB, P(HB-HV), and P(HB-HHx) were conducted with thermogravimetry (TG) and diferential scanning calorimetry (DSC). The experimental results show that the incorporation of 30 mol % 3-hydroxyvalerate (HV) and 15 mol % 3-hydroxyhexanoate (HHx) components into the polyester increased the various thermal degradation relative to those of PHB by 3-12oC (measured at B = 40oC min-1). DSC measurements showed that the incorporation of HV and HHx decreased the melting temperature relative to that of PHB by 70oC. In the second part of the experiment, the thermal degradation kinetics of PHB and P(HB-HV) under nitrogen was studied by TG. The thermal degradation mechanism of PHB and P(HB-HV) under nitrogen was investigated with TG-FTIR and Py-GC/MS. The results show that the degradation products of PHB are mainly propene, 2-butenoic acid, propenyl-2-butenoate and butyric-2-butenoate, whereas, those of P(HB-HV) are mainly propene, 2-butenoic acid, 2-pentenoic acid, propenyl-2-butenoate, propenyl-2-pentenoate, butyric-2-butenoate, pentanoic-2-pentenoate and CO2. The degradation is probably initiated from the chain scission of the ester linkage. In the third part, the experiment focused on the synthesis and characterization of water-soluble ethoxy [60]fullerol. A novel fullerene derivative C60(OCH2CH3)8(OH)16 was synthesized through the substitution of bromine atoms from C60Br24in CH3CH2OH/H2O/NaOH solution at ambient temperature (23oC). Both the results of IR and NMR determination showed that the hydoxyl groups and ethoxy groups were bonded to the [60]fulerene cage. The antioxidant activity of ethoxy [60]fullerol is very weak. Ethoxy [60]fullerol has antitumor activity.

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