DNA-TiO$_{2}$ nanoparticle nanoassembies: effect of temperature and nanoparticles concentration on aggregation

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.