The interaction of TiO2 NPs with human genomic DNA has been
studied with UV–visible spectroscopy in order to investigate the possible
binding of nanoparticle to DNA. Interaction of DNA with TiO2 NPs
is studied by recording the absorption spectra for a constant DNA concentration
in various TiO2 NPs mixing ratios at 37 °C, the results of
which are shown in Fig. 7.. Absorption Spectroscopy helps to determine
the binding characteristics of metal complexes with DNA. The spectral
changes observed in the form of ‘hyperchromism’ and ‘hypochromism’
during the process, reflect the change in conformation of DNA and
structure of DNA [19]. Metal complex can bind to the DNA via covalent
and or/non-covalent interactions [20]. DNA base pairs have strong optical
absorption at approximately 260 nm. The absorption spectra of DNA
in absence and presence of TiO2 NPs is shown in Fig. 7a. With addition of
increasing amounts of TiO2 NPs to DNA, there is an increase in absorbance
observed, up to 15.3%, without any shift in the maxima wavelength
of 256 nm. Hyperchromism is reported to suggest breakage of
the secondary structure of DNA, and therefore this hyper chromic effect
suggests there exists a strong interaction between nanoparticles and the
human genomic DNA [21]. The binding results of which are shown in
the Fig. 7b. The metal complex can bind to DNA via covalent and or/
non-covalent interactions. Covalent interactions include via alkylation
or inter and intra strand crosslinking [22]. Non-covalent interactions include
the following