Magnetically deliverable calcium phosphate nanoparticles for localized gene expression

Abstract

Iron oxide doped tricalcium phosphate (Fe₂O₃@TCP) nanoparticles were designed as transfection vehicles and prepared by flame spray synthesis. Both components are known to be non-toxic and biocompatible. Calcium phosphate (CaP) facilitates DNA entry into cells without the need for toxic cationic mediators, while magnetic iron oxide allows for particle localization at a target site. Flame spray synthesis ensures easy and low-cost nanoparticle production in a reproducible way. Fe₂O₃@TCP nanoparticles, exhibiting DNA-binding capacity in the presence of CaCl₂, were tested for transfection of a green fluorescent protein (GFP) encoding plasmid with Human Embryonic Kidney 293 (HEK 293) cells. Commercial magnetic agents, polyethylenimine (PEI) and standard calcium phosphate-mediated transfection were used for comparison. Transfection efficiency was estimated by GFP expression detected by fluorescence microscopy, while hoechst/ethidium homodimer-1 staining allowed the evaluation of method toxicity. We were able to efficiently transfect HEK 293 cells, and showed that Fe₂O₃@TCP particles and bound DNA can be concentrated in specific sites in a culture plate through the application of a magnetic field gradient to achieve localized transfection. While the commercial magnetic controls strongly affected cell growth and morphology, Fe₂O₃@TCP particles did not show marked toxicity and had only limited effects on cell proliferation. Overall performance in terms of transfection efficiency, cell proliferation and viability, were comparable to that of CaP and PEI, which lack magnetic targeting capability. The newly synthetized Fe₂O₃@TCP are, therefore, improved tools to deliver nucleic acids into cells and achieve spatial control of transfection.