关键词：氧化铁；纳米颗粒；聚甘油；功能化
摘 要：Superparamagnetic iron oxide nanoparticle (SPION) has attracted a great deal of attention in the fields of medicine and biology due to its non-toxicity, large specific surface area, amenability to various surface fuctionalization, and unique magnetic properties. For biomedical applications, we synthesized two kinds of SPIONs by co-precipitation and polyol methods, designated as C- and P-SPIONs, respectively. To increase their solubility and stability in an aqueous solution, both of the SPIONs were functionalized with hyperbranched polyglycerol (PG) through ring-opening polymerization of glycidol. Scanning transmission electron microscopy (STEM) and dynamic light scattering (DLS) measurements revealed that the P-SPION provided individual nanoparticles without aggregation after the PG fuctionalization. This P-SPION-PG was highly soluble not only in pure water (＞ 40 mg/mL), but also in a phosphate buffer solution (＞ 25 mg/mL). Such high solubility enabled separation of P-SPION-PG according to their size by size exclusion chromatography (SEC). The size-separated P-SPION-PG shows a gradual increase in transverse relaxivity (r_2) with increasing particle size. The hydroxyl group in PG also serves as a scaffold for further surface functionalization. For targeted cell labeling, we functionalized P-SPION-PG through multi-step organic transformations (-OH → -OTs (tosylate) → -N_3 → -RGD) including click chemistry as a key step to impart targeting specificity by immobilization of cyclic RGD peptide on the surface. The targeting effect was demonstrated by the cell experiments; P-SPION-PG-RGD was taken up by the cells overexpressing α_vP_3-integrin such as U87MG and A549. In addition, near-infrared (NIR) fluorescence dye (IRdye 800CW) was immobilized on the surface of P-SPION-PG through amide linkage. The resulting P-SPION-PG-IRdye showed good solubility in phosphate buffered saline (PBS) and strong fluorescence in NIR region, which may find application in optical/MR bimodal imaging.