| Co-Investigator(Kenkyū-buntansha) |
YAGI Kazuo Univ.Mie, Dept.Mech.Enge., Lecturer, 工学部, 講師 (50201819)
HANAICHI Takamasa N.I.T., Dept.Electri.and comput.Eng., Assistant, 工学部, 助手 (90252311)
KAWAGUCHI Takeshi N.I.T., Dept.Electri.and comput.Eng., Lecturer., 工学部, 講師 (80144195)
SKAMOTO Isao N.I.T., Dept.Physics, Associate Prof., 工学部, 助教授 (80094267)
FUJITSUKA Noriaki N.I.T., Dept.Health & Phys.Edu., Prof., 工学部, 教授 (60101268)
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| Research Abstract |
Dextran and its derivative-iron oxide complexes (DM) were developed as a magnetic fluid applicable to biological and medical fields. The results obtained in this developmental scientific research are summarized as follows.
(1) Dextrain-magnetite samples with two different types, ATDM and CMDM,were synthesized without any surfactant. They are composed of ultrafine magnetite (core) with 3.5-10 nm in diameter and alkali-treated dexttran (ATD) and of the core and carboxymethyl dextran derivatives (CMD), of which 10-20% hydrogen atoms of hydroxy groups are replaced by carboxymethyl radicals. The obtained DM have a high biochemical stability, as well as chemical and physical stability, low toxicity and the superpara magnetic properties.
(2) The confomation of dextran and its derivative molecular chains in ATDM and CMDM magnetic fluid, bonding structure and number of bonding site between the core and dextran have been defined. The electrophoretic measurements in simulated physiological fluid sh
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ows that ATDM and CMDM carry a positively charge and negatively one, respectively. The fact that the dissociation constant of dextran chains in ATDM fluid takes a value as small as 10^<-6> order at 20ﾟC is strongly suggestive that the dextran is jointed to the magnetite core (Fe_3O_4=FeO・Fe_2O_3).
(3) The results of Moessbauer effect of the magnetite core, ATDM and CMDM powder samples showed that the bonding of dextran to magnetite core results in the increase of Fe^<3+> component with the largest internal magnetic field and then the effect is a large for ATDM than CMDM.This might be thought to be due to the stronger electronegativity of carboxyl radicals in ATD.
(4) The behavior (uptake and metabolization) of DM in organs of rat (blood, spleen, liver, cortex and medulla of kidney, lung, pancreas, duodenum, cerebrum etc.), intravenous-injected to rat bodies, were examined through the experiments of TEM observation and optical microscopy, as well as T1 and T2 relaxation time by pulse NMR method, after an elapse of various period (1h-2weeks) in compliance with the research purpos. The concentration of DM in blood after administration was decreased exponentially, closely related to the remarkable uptake of DM in spleen and liver, and the change in the decrease of ATDM was faster than CMDM.The DM iv-injected is mainly uptaked in lysosomes of Kupffer's cell and macrophage at liver tissue and spleen one, respectively, and subsequently metabolized for a relatively short period of time (about 1 week for ATDM and about 2 weeks for CMDM).
(5) It has been found that DM magnetic fluid is especially available as MRI constant agent for liver and spleen.
(6) The results of thermally-induced magnetic properties have showed that the cores of ATDM and CMDM are not oxidized up to 850ﾟC even in air, as well as in helium, but they are changed into ferrite (alpha-Fe) for ATDM and ferrite and cementite for CMDM,respectively. Less
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