Size-controlled preparation of magnetic iron oxidenanocrystals within hyperbranched polymers and their magnetofection in vitro

Abstract

A new strategy for the size-controlled preparation of magnetic iron oxide nanocrystals (NCs) within hyperbranched poly(ethylenimine)s (HPEIs) has been described. HPEI was not only utilized as the nanoreactors and stabilizers to prepare size-controlled magnetic NCs, but also skillfully used as a base supplier to avoid introducing alkali hydroxide or ammonia. By changing the weight ratio of FeSO₄·7H₂O to HPEI, magnetic iron oxide NCs with various sizes were obtained. Owing to the efficient gene transfection properties of HPEI, the resulting iron oxide/HPEI nanocomposites were used as magnetic nonviral gene vectors for magnetofection and showed to be good gene vectors. It was found that the size of magnetic iron oxide had a significant effect on the magnetofection properties while a pure HPEI transfection enhancer was not introduced. When the mean size of magnetic iron oxide increased, the transfection efficiency was enhanced. With the addition of a pure HPEI transfection enhancer, the size of magnetic iron oxide showed a slight impact on the magnetofection properties. The luciferase expression levels mediated by iron oxide/HPEI nanocomposites with various iron oxide sizes in COS-7 cells under a magnetic gradient field were all more than 115 fold of that of standard HPEI transfection.