Composites of peptide nucleic acids with titanium dioxide nanoparticles. II. Dissociation of DNA/PNA duplexes within TiO2 · polylysine · DNA/PNA nanocomposites and in solution. Effect of polylysine

When creating effective drugs, it is important not only to transport them into cells, but also allow them to be released from the “transporter” after the delivery. It was shown that the dissociation of peptide nucleic acids (PNA) from TiO2 · PL · DNA/PNA nanocomposites occurred according to a typical thermal denaturation, and polylysine (PL) in the nanocomposite has almost no effect on the dissociation. These data suggest that the immobilization of PNA in the TiO2 · PL · DNA/PNA nanocomposite is reversible and PNA can be easily released from TiO2 carrier into solution. In contrast to that, the dissociation of DNA/DNA and DNA/PNA duplexes in physiological solution in the presence of PL was not observed. PL in solution dramatically influences the dependence of the optical density on temperature and time for DNA/DNA duplexes and to a lesser degree for DNA/PNA duplexes. It has been assumed that PL and DNA/DNA duplexes in physiological solutions form triple polycomplexes (DNA/DNA · PL)m, which can aggregate and precipitate. PL in solution can also interact with DNA/PNA duplexes to form monocomplexes PL · (DNA/PNA)n consisting of one PL chain and one or more (n) DNA/PNA duplexes. Although these monocomplexes do not precipitate, the dissociation of DNA/PNA duplexes from them is complicated.