复合微球作为一种新型的功能材料，由于其物理化学性质及胶体性质可随环境变化（如温度、pH、电场和磁场等），近年来被广泛研究，特别是在生物分离、磁共振成像、靶向药物传输、肿瘤热疗等生物医学领域得到了广泛的应用.
我们用改进的微乳液法合成了磁性海藻酸微球并用溶胶-凝胶法对其表面进行SiO2修饰，用透射电子显微镜（TEM），热重分析（TGA）和振动样品磁强计（VSM）对其尺寸，磁含量及磁性进行了表征并用其分离提取血浆DNA。结果表明复合微球平均粒径约为4.4 µm且尺寸比较均一; 微球呈超顺磁性，其饱和磁化强度为15.1 emu/g, 磁含量为31.7%. 此外,该复合微球能很好地稳定分散于水中并具有较高的磁响应性. 用得到的复合微球分离提取血浆DNA操作简便、快速，提取率约为30%.
Scheme 1. Schematic illustration of the synthesis of MAMs@SiO2 particles.
Figure 4. TEM image of MAMs (a), a representative microsphere in high magnification (b), and MAMs@SiO2 particles (c).
Figure 7. A typical TGA curve of as-synthesized MAMs.
Figure 10. Room-temperature hysteresis loops of the MAMs (a) and MAMs@SiO2 particles synthesized with TEOS content of 20 µL (b), 50 µL (c) and 100 µL (d), respectively. Fixed ammonia solution volume (0.3 mL) was used. The insets show room-temperature hysteresis loops of bare γ-Fe2O3 NPs and DMSA-coated γ-Fe2O3 NPs and the photographic image of the as-synthesized MAMs@SiO2 particles in the presence of an external magnet.
Figure 11. 1% Agarose gel electrophoresis of isolated plasma DNA Lane 1: DNA 20 bp ladder; lane 2: DNA isolated using the magnetic silica microspheres; lane 3: DNA obtained from commercially available kits.
