Design of TiO2∼DNA nanocomposites for penetration into cells

Methods of noncovalent immobilization of DNA fragments on titanium dioxide nanoparticles (TiO2) were developed to design TiO2 similar to DNA nanocomposites, which were capable of penetrating through cell membranes. TiO2 nanoparticles of different forms (amorphous, anatase, brookite) with enhanced agglomeration stability were synthesized. The particles were characterized by X-ray diffraction, small-angle X-ray scattering, infrared spectroscopy and atomic force microscopy. Three approaches to the preparation of nanocomposites are described: 1) sorption of polylysine-containing oligonucleotides onto TiO2 nanoparticles, 2) the electrostatic binding of oligonucleotides to TiO2 nanoparticles bearing immobilized polylysine, and 3) sorption of oligonucleotides on TiO2 nanoparticles in the presence of cetyltrimethylammonium bromide (cetavlon). All three methods provide an efficient and stable immobilization of DNA fragments on nanoparticles that leads to nanocomposites with a capacity of up to 40 nmol/mg for an oligonucleotide. DNA fragments in nanocomposites were shown to retain their ability to form complementary complexes. It was demonstrated by confocal laser microscopy that the proposed nanocomposites penetrated into cells without transfection agents and other methods of exposure.