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The development of efficient and convenient systems for the delivery of nucleic-acid-based drugs into cells is an urgent task. А promising approach is the use of various nanoparticles. Silica nanoparticles can be used as vehicles to deliver nucleic acid fragments into cells. In this work, we developed a method for the synthesis of silicon–organic (Si–NH2) non-agglomerated nanoparticles by the hydrolysis of aminopropyltriethoxysilane (APTES). The resulting product forms a clear solution containing nanoparticles in the form of low molecular weight polymer chains with [─Si(OH)(C3H6NH2)O─] monomer units. Oligonucleotides (ODN) were conjugated to the prepared Si–NH2 nanoparticles using the electrostatic interaction between positively charged amino groups of nanoparticles and negatively charged internucleotide phosphate groups in oligonucleotides. The Si–NH2 nanoparticles and Si–NH2·ODN nanocomplexes were characterized by transmission electron microscopy, atomic force microscopy and IR and electron spectroscopy. The size and zeta potential values of the prepared nanoparticles and nanocomplexes were evaluated. Oligonucleotides in Si–NH2·ODN complexes retain their ability to form complementary duplexes. The Si–NH2Flu nanoparticles and Si–NH2·ODNFlu nanocomplexes were shown by fluorescence microscopy to penetrate into human cells. The Si–NH2Flu nanoparticles predominantly accumulated in the cytoplasm whereas ODNFlu complexes were predominantly detected in the cellular nuclei. The Si–NH2·ODN nanocomplexes demonstrated a high antisense activity against the influenza A virus in a cell culture at a concentration that was lower than their 50% toxic concentration by three orders of magnitude.

Synthetic DNA molecules of 10-23 deoxyribozymes (Dz) are known to be efficient and site-specific agents for the RNA cleavage in a catalytic manner. To provide the penetration of Dz into cells, we have proposed the new delivery system for deoxyribozymes in the form of TiO 2 •PL-Dz nanocomposite. These nanocomposites consist of catalytically ac- tive Dz molecules noncovalently immobilized through the polylysine linker to TiO 2 nanoparticles, which provide the penetration of Dz into cells. Deoxyribozymes in the prepared TiO 2 •PL-Dz nanocomposites were shown to retain their ability to cleave RNA targets albeit at a slower rate but with the same site-specificity and similar efficiency as free Dz. Unlike free Dz, the proposed TiO 2 •PL-Dz nanocomposites penetrate into cells without auxiliary actions.

A system for delivery of analogues of 2'-deoxyribonucleoside triphosphate (dNTP) based on SiO(2) nanoparticles was proposed. A simple and versatile method was developed for the preparation of SiO(2)-dNTP conjugates using the 'click'-reaction between premodified nanoparticles containing the azido groups and dNTP containing the alkyne-modified γ-phosphate group. The substrate properties of SiO(2)-dNTP were tested using Klenow fragment and HIV reverse transcriptase. Nucleoside triphosphates being a part of the SiO(2)-dNTP nanocomposites were shown to be incorporated into the growing DNA chain. The rate of polymerization with the use of SiO(2)-dNTP or common dNTP in case of HIV reverse transcriptase differed insignificantly. It was shown by confocal microscopy that the proposed SiO(2)-dNTP nanocomposites bearing the fluorescent label penetrate into cells and even into cellular nuclei.

Various materials, such as glass, plastic, metals, etc., are utilized for preparing DNA chips. In each particular case special approaches are used for immobilization of different oligonucleotide derivatives on the solid supports. We describe a general technique for DNA chips preparation on various unmodified surfaces using one type of oligonucleotide derivative, polylysine-oligonucleotide conjugates (PL-oligo). A long polyamine spacer in the PL-oligo conjugates provides a durable irreversible non-covalent immobilization onto a variety of solid supports and enough distance between oligonucleotides and the surface. The resulting DNA chips were shown to be useful for the detection of PCR DNA fragments and to be sensitive to single nucleotide discrepancies. They represent a promising instrument for revealing genetic diseases, genotyping viruses and bacteria, and for displaying their drug-resistant strains.