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Silica-Iron Oxide Magnetic Nanoparticles Modified for Gene Delivery: A Search for Optimum and Quantitative Criteria

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An Erratum to this article was published on 03 February 2012



To optimize silica-iron oxide magnetic nanoparticles with surface phosphonate groups decorated with 25-kD branched polyethylenimine (PEI) for gene delivery.


Surface composition, charge, colloidal stabilities, associations with adenovirus, magneto-tranduction efficiencies, cell internalizations, in vitro toxicities and MRI relaxivities were tested for the particles decorated with varying amounts of PEI.


Moderate PEI-decoration of MNPs results in charge reversal and destabilization. Analysis of space and time resolved concentration changes during centrifugation clearly revealed that at >5% PEI loading flocculation gradually decreases and sufficient stabilization is achieved at >10%. The association with adenovirus occurred efficiently at levels over 5% PEI, resulting in the complexes stable in 50% FCS at a PEI-to-iron w/w ratio of ≥7%; the maximum magneto-transduction efficiency was achieved at 9–12% PEI. Primary silica iron oxide nanoparticles and those with 11.5% PEI demonstrated excellent r2* relaxivity values (>600 s−1(mM Fe)−1) for the free and cell-internalized particles.


Surface decoration of the silica-iron oxide nanoparticles with a PEI-to-iron w/w ratio of 10-12% yields stable aqueous suspensions, allows for efficient viral gene delivery and labeled cell detection by MRI.

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American Type Culture Collection


Dulbecco’s modified Eagle’s medium


Ethylenediaminetetraacetic acid


fetal calf serum


multi-echo gradient echo


magnetic nanoparticles


mouse pancreatic ductal adenocarcinoma


magnetic resonance imaging


Dulbecco’s phosphate buffered saline




silica-iron oxide magnetic nanoparticle

SiOx :

silica-like coating of the iron oxide nanoparticles


Transmission Electron Microscopy


tetraethyl orthosilicate


3-(trihydroxysilyl) propylmethylphosphonate


transducing units


virus particle


X-ray photoelectron spectroscopy


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Correspondence to Olga Mykhaylyk.

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Mykhaylyk, O., Sobisch, T., Almstätter, I. et al. Silica-Iron Oxide Magnetic Nanoparticles Modified for Gene Delivery: A Search for Optimum and Quantitative Criteria. Pharm Res 29, 1344–1365 (2012).

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