Hamoudeh Misara, Fessi Hatem
LAGEP, Laboratoire d'Automatique et de Génie de Procédés, Pharmaceutical Technology Department (UCB), CPE-Lyon, 43 Bd. du 11 Novembre 1918, 69622 Villeurbanne Cedex, France.
J Colloid Interface Sci. 2006 Aug 15;300(2):584-90. doi: 10.1016/j.jcis.2006.04.024. Epub 2006 Jun 6.
Magnetic microparticles (MMP) have shown to be applied in increasing applications in various fields of biotechnology and medicine. One of their most promising utilization is the magnetic resonance imaging (MRI) in which superparamagnetic substances as magnetite are used in a nanometric size (less than 30 nm) and encapsulated within locally injected biodegradable microparticles. In this paper, magnetite has been encapsulated in polymer-based microparticles. The MMP have been prepared by an emulsion evaporation method. The different parameters influencing the particles size were investigated. The size was found to decrease as the stirring speed or the stabilizer amount (to certain limit) increases. The encapsulation efficacy was more than 90% yielding a magnetite loading of up to 30%, w/w. The X-ray photoelectron spectroscopy (XPS) showed less than 2% of iron atoms at the microparticles surface. The zeta potential response of MMP towards pH variation was very similar to that of magnetite-free microparticles confirming the encapsulation of magnetite within the microparticles. X-ray diffraction assays showed that magnetite crystalline structure was conserved after emulsification and MMP formation. Vibration simple magnetometer (VSM) showed a superparamagnetic profile of the MMP with a magnetic saturation increasing with the increased magnetite amount in the microparticles. These magnetic microparticles can enable clinicians to control microparticles distribution after a local administration in tumors by MRI. They can also be administered to target a defined tumor area by focusing a magnetic field on the surfaces covering the cancerous tissue.
磁性微粒（MMP）已在生物技术和医学的各个领域中得到越来越广泛的应用。其最具前景的应用之一是磁共振成像（MRI），其中超顺磁性物质如磁铁矿以纳米尺寸（小于30 nm）使用，并封装在局部注射的可生物降解微粒中。在本文中，磁铁矿已被封装在聚合物基微粒中。MMP通过乳液蒸发法制备。研究了影响颗粒尺寸的不同参数。发现随着搅拌速度或稳定剂用量（达到一定限度）的增加，颗粒尺寸减小。包封率超过90%，磁铁矿负载量高达30%（w/w）。X射线光电子能谱（XPS）显示微粒表面铁原子含量低于2%。MMP对pH变化的zeta电位响应与无磁铁矿微粒非常相似，证实了磁铁矿在微粒中的包封。X射线衍射分析表明，乳化和MMP形成后磁铁矿的晶体结构得以保留。振动样品磁强计（VSM）显示MMP具有超顺磁性特征，其磁饱和度随着微粒中磁铁矿含量的增加而增加。这些磁性微粒能够使临床医生在局部给药后通过MRI控制微粒在肿瘤中的分布。它们还可以通过将磁场聚焦在覆盖癌组织的表面来靶向特定的肿瘤区域。
