Spectroscopic evidence of platinum–DNA interactions in DNA-functionalized gold nanoparticles

Introduction: Gold nanoparticles (AuNPs) were sequentially functionalized with a thiolated oligonucleotide sequence (S-C-4GAAAAG) and subsequently exposed to a platinum complex to investigate metal–DNA interactions at the nanoparticle interface. Materials and methods: The system was characterized by dynamic light scattering, zeta-potential measurements, UV–visible spectroscopy, and FTIR spectroscopy supported by second-derivative analysis. Results: Dynamic light scattering revealed an increase in hydrodynamic diameter from 25.71 ± 0.04 nm for bare AuNPs to 32.27 ± 0.41 nm after DNA functionalization, while a negative zeta potential (−40.5 ± 2.9 mV) was observed after DNA functionalization, indicating maintained electrostatic stabilization. UV–visible spectroscopy showed only a minimal variation in the localized surface plasmon resonance maximum after DNA functionalization, which was interpreted as complementary rather than independent evidence of surface modification. FTIR spectroscopy revealed distinct vibrational changes in nucleobase and phosphate regions, consistent with an interaction between hexachloroplatinic acid (HexPt) and the DNA-functionalized nanoparticles. Conclusions: The results provide physicochemical and spectroscopic evidence consistent with sequential surface modification of AuNPs by the thiolated oligonucleotide and subsequent association with HexPt.