|415. Majewski, A.P.; Schallon, A.; Jérôme, V.; Freitag, R.; Müller, A.H.E.; Schmalz, H.: Dual-Responsive Magnetic Core-Shell Nanoparticles for Nonviral Gene Delivery and Cell Separation, Biomacromolecules 13(3), 857 (2012) -- DOI: 10.1021/bm2017756|
We present the synthesis of dual-responsive (pH and temperature) magnetic core-shell nanoparticles utilizing the grafting-from approach. First, oleic acid stabilized superparamagnetic maghemite (γ-Fe2O3 nanoparticles (NP’s), prepared by thermal decomposition of iron pentacarbonyl, were surface-functionalized with ATRP initiating sites bearing a dopamine anchor group via ligand exchange. Subsequently, 2-(dimethylamino)ethyl methacrylate (DMAEMA) was polymerized from the surface by ATRP, yielding dual-responsive magnetic core-shell NP’s (γ-Fe2O3@PDMAEMA). The attachment of the dopamine anchor group on the nanoparticles´ surface is shown to be reversible to a certain extent, resulting in a grafting density of 0.15 chains per nm² after purification. Nevertheless, the grafted NP’s show excellent long-term stability in water over a wide pH range, and exhibit a pH- and temperature-dependent reversible agglomeration as revealed by turbidimetry. The efficiency of γ-Fe2O3@PDMAEMA hybrid nanoparticles as a potential transfection agent was explored under standard conditions in CHO-K1 cells. Remarkably, γ-Fe2O3@PDMAEMA led to a twofold increase of the transfection efficiency without increasing the cytotoxicity as compared to polyethyleneimine (PEI) and yielded on average more than 50% transfected cells. Moreover, after transfection with the hybrid nanoparticles the cells acquired magnetic properties that could be used for selective isolation of transfected cells.