Covalently bonded dendrimer-maghemite nanosystems: nonviral vectors for in vitro gene magnetofection

In this work novel nonviral nanosystems for in vitro gene magnetofection are presented. The multifunctional vectors consist of superparamagnetic iron oxide nanoparticles functionalized with low generations of poly(propyleneimine) dendrimers. The dendrimers are attached to the iron oxide nanoparticles through covalent bonds via a one-pot sol-gel synthetic route. This approach allows a direct dendritic decoration of the iron oxide NPs without any additional surface modification. Furthermore, this strategy avoids the multistep procedures of dendritic growth onto solid surfaces. The core-shell hybrid structures are water soluble as colloidal ferrofluids which are long-term stable at physiological pH. In vitro transfection experiments were assayed with Saos-2 osteoblasts, using as reporter gene a plasmid DNA that codes for the green fluorescent protein. Gene delivery experiments were carried out in the presence and in the absence of a magnetic field. The transfection efficiency strongly depends on the presence of the magnetic field and the dendrimer generation. The covalent bonding between the dendrimers and the magnetic nanoparticles surface ensures the vector integrity throughout storage and application. The nanosystems couple the DNA fragments and safely transport them under magnetic stimulus from the extracellular environment to the interior of the cell.