Novel Magnetic Hydroxyapatite Nanoparticles as Non-Viral Vectors for the Glial Cell Line-Derived Neurotrophic Factor Gene

Nanoparticles (NPs) of synthetic hydroxyapatite (Hap) and natural bone mineral (NBM) are rendered magnetic by treatment with iron ions using a wet‐chemical process. The magnetic NPs (mNPs), which are about 300 nm in diameter, display superparamagnetic properties in a superconducting quantum interference device, with a saturation magnetization of about 30 emu g−1. X‐ray diffraction and transmission electron microscopy reveal that the magnetic properties of the NPs are the result of the hetero‐epitaxial growth of magnetite on the Hap and NBM crystallites. The mNPs display a high binding affinity for plasmid DNA in contrast to magnetite NPs which do not bind the plasmid well. The mHap and mNBM NPs result in substantial increases in the transfection of rat marrow‐derived mesenchymal stem cells with the gene for glial cell line‐derived neurotrophic factor (GDNF), with magnetofection compared to transfection in the absence of a magnet. The amount of GDNF recovered in the medium approaches therapeutic levels despite the small amount of plasmid delivered by the NPs. Magnetic synthetic hydroxyapatite and natural bone mineral nanoparticles are synthesized as non‐viral vectors for gene delivery. The magnetic calcium phosphate nanoparticles display a high binding affinity for plasmid DNA in contrast to magnetite nanoparticles and enable substantial increases in the transfection of mesenchymal stem cells in vitro with the gene for a neurotrophic factor, under the action of an external magnet.