Naked eye detection of mutagenic DNA photodimers using gold nanoparticles

We developed a method to detect mutagenic DNA photodimers by the naked eye using gold nanoparticles. The stability of gold nanoparticles in a high ionic strength solution is maintained by straight ssDNA adsorbed physically on the AuNPs. However, we found that UV-irradiated DNA was less adsorptive onto gold nanoparticles because of a conformational change of UV-irradiated DNA. The accumulated deformation of the DNA structure by multiple-dimer formation triggered aggregation of the gold nanoparticles mixed with the UV-irradiated DNA and thus red to purple color changes of the mixture, which allowed colorimetric detection of the DNA photodimers by the naked eye. No fragmented mass and reactive oxygen species production under the UVB irradiation confirmed that the aggregation of gold nanoparticles was solely attributed to the accumulated deformation of the UV irradiated DNA. The degree of gold nanoparticles-aggregation was dependent on the UVB irradiated time and base compositions of the UV-irradiated oligonucleotides. In addition, we successfully demonstrated how to visually qualify the photosensitizing effect of chemical compounds in parallel within only 10 min by applying this new method. Since our method does not require any chemical or biochemical treatments or special instruments for purifying and qualifying the DNA photolesions, it should provide a feasible tool for the studies of the UV-induced mutagenic or carcinogenic DNA dimers and accelerate screening of a large number of drug candidates.