  TiO$_{2}$ nanoparticles (NPs) have unique photocatalytic properties, which
are used in food industries, medicine, biosensorics, and solar energy
conversion. Since the toxic properties of TiO$_{2}$ NPs have been
insufficiently studied, additional information on the molecular mechanisms of
their biological action on the structure and stability of biological
macromolecules is needed, especially concerning DNA. In this work exploiting
the differential UV-visible spectroscopy, the effect of the heating (from 20
till 90 $^0$C) and concentration of TiO$_{2}$ NPs ((1-3)$\times$10$^-$$^4$ M)
on a conformation of native DNA adsorbed on TiO$_{2}$ NPs in a buffer solution
(pH 5) is studied. Analysis of dynamic light scattering (DLS) data for the
DNA:TiO$_{2}$ NPs suspension revealed that when the temperature increases the
separated DNA:TiO$_{2}$ NP nanoassemblies form nanoaggregates. Correlation
between the thermal dependency of the DLS data and thermal DNA denaturation
measurements indicated that the appearance of the single-stranded unwound
regions in double-stranded DNA in the suspension with temperature rise promotes
the effective formation of the DNA:TiO$_{2}$ NPs nanoaggregates.
