Functionalisation of calcium phosphate nanoparticles by oligonucleotides and their application for gene silencing

In molecular biology, the production of proteins can be effectively inhibited by introducing specific oligonucleotides into a living cell ( gene silencing or antisense strategy; important for gene therapy). Calcium phosphate nanoparticles can serve as carriers for biomolecules in such therapeutic applications due to their high biocompatibility and biodegradability. Stable colloids were prepared by coating the inorganic nanoparticles with single- and double-stranded oligonucleotides. The dispersions were analysed by dynamic light scattering, zeta potential measurements, transmission electron microscopy, and scanning electron microscopy. Particles with a diameter of about 100 nm were obtained under optimized conditions. The efficiency of such nanoparticles to specifically inhibit protein synthesis was tested on HeLa-EGFP cells whose green fluorescence was turned off by the coated nanoparticles ( gene silencing with siRNA). If siRNA was incorporated into the calcium phosphate particle and thereby protected from intracellular degradation, the transfection efficiency was significantly increased. The dispersions were stable and could be stored at 4 degrees C without loss of activity for several weeks, making them available as biochemical reagents.