基于叶酸靶向PEG修饰型超支化聚合物制备氧化铁纳米晶体及磁转染应用研究

The superparamgnetic Fe3O4 nanocrystals have significant prospect on bio-medicine such as magnetofection, magnetic resonance imaging, etc. Until now, Fe3O4 nanocrystals are often prepared by small stabilizers such as oleic acid and polymers with carboxylic acid groups. However, the resulting Fe3O4 nanocrystals can not be directly used in magnetofection, etc. The cationic hyperbranched polymers such as hyperbranched polyamines are regarded as ideal nanoreactors for the preparation of nanocrystals. Moreover, they are also a kind of excellent nonviral gene vectors. By preparing Fe3O4 nanocrystals within cationic hyperbranched polymers, the gene transfection property of cationic hyperbranched polymers and the magnetic behavior of Fe3O4 nanocrystals can be effectively combined. In addtion, proper modification can be conducted to increase the biocompatibility of cationic hyperbranched polymers and to introduce specific targeting, thus magetic nonviral gene vectors with double targeting, little cytotoxicity and high gene transfection efficiency can be obtained. The defect of current gene vetors such as high cytotoxictiy, low transfection efficiency and lack of targeting can be resolved by this method. In this program, we would like to construct hyperbranced polyamines with folate receptor, low cytotoxicity and high gene transfection efficiency and then to prepare size-controlled magnetic Fe3O4 nanocrystals. The application on magnetofection of the resulting magetic nonviral gene vectors with folate and Fe3O4 double targeting will be also investigated.

具有超顺磁特性的Fe3O4纳米晶体在磁转染、核磁共振成像等生物医学领域具有重要的应用前景。目前，Fe3O4纳米晶体多是采用油酸等小分子或含有羧酸基团的聚合物制备，不能直接应用于磁转染等领域。阳离子型超支化聚合物如超支化聚胺是一类制备无机纳米晶体材料的理想纳米反应器，它们还是优良的非病毒基因载体。基于阳离子超支化聚合物制备磁性Fe3O4纳米晶体，把阳离子超支化聚合物的基因转染特性和Fe3O4纳米晶体的磁性有效结合起来，辅以适当的修饰以提高聚合物生物相容性、引入特异靶向性，能够得到具有双重靶向特性、低细胞毒性和高转染效率的磁性非病毒基因载体。基于此能够有效解决目前基因载体普遍存在的细胞毒性大、转染效率低和缺乏靶向性等缺点。项目拟构建具有叶酸受体、低细胞毒性和高转染效率的超支化聚胺，并用于制备尺寸可控的磁性Fe3O4纳米晶体，探索叶酸和Fe3O4双靶向型磁性非病毒基因载体在磁转染等领域的应用。

具有超顺磁特性的Fe3O4纳米晶体在磁转染、核磁共振成像等生物医学领域具有重要的应用前景。目前，Fe3O4纳米晶体多是采用油酸等小分子或含有羧酸基团的聚合物制备，不能直接应用于磁转染等领域。阳离子型超支化聚合物如超支化聚胺是一类制备无机纳米晶体材料的理想纳米反应器，它们还是优良的非病毒基因载体。基于阳离子超支化聚合物制备磁性Fe3O4纳米晶体，把阳离子超支化聚合物的基因转染特性和Fe3O4纳米晶体的磁性有效结合起来，辅以适当的修饰以提高聚合物生物相容性、引入特异靶向性，能够得到具有双重靶向特性、低细胞毒性和高转染效率的磁性非病毒基因载体。基于此能够有效解决目前基因载体普遍存在的细胞毒性大、转染效率低和缺乏靶向性等缺点。在本项目支持下申请者构建了具有叶酸受体、低细胞毒性和高转染效率的超支化聚乙烯亚胺，并用于制备了尺寸可控的磁性Fe3O4纳米晶体，探索了叶酸和Fe3O4双靶向型磁性非病毒基因载体在磁转染等领域的应用，该双靶向型载体的磁转染效率最高可达超支化聚乙烯亚胺（Mw 25000）的74倍。