Calcium phosphate nanoparticles for the transfection of cells

Transfection is a widely used method in molecular biology for the introduction of foreign nucleic acids (DNA or RNA) into eukaryotic cells that permits to control intracellular processes, i.e. the induction or inhibition of protein expression. Nucleic acids alone cannot penetrate the cell membrane, therefore special carriers like cationic polymers or inorganic nanoparticles are required. Single-shell and multi-shell calcium phosphate nanoparticles were prepared and functionalized with DNA and siRNA. Thereby, the expression of enhanced green fluorescing protein (EGFP) can be induced (by using pcDNA3-EGFP) or silenced (by using siRNA). The single-shell nanoparticles were prepared by rapid mixing of aqueous solutions of calcium nitrate and diammonium hydrogen phosphate. The multi-shell nanoparticles were produced by adding further layers of calcium phosphate and DNA to protect DNA from the intracellular degradation by endonucleases. The size of the nanoparticles according to dynamic light scattering and electron microscopy was up to 100 nm with a zeta potential around -30 mV. The transfection efficiency of the nanoparticles was tested in vitro in cell culture.