Distinct structural interactions of polyadenine and polythymine on gold nanoparticles: from single strands to duplexes

Motivated by potential applications in fields such as medicine or materials science, various methodologies have been developed for the preparation of so-called spherical nucleic acids, based on oligonucleotides and metal nanoparticles. Despite optimization through various parameters such as loading efficiency or nanoconjugate stability, much remains to be known regarding the actual conformations of oligonucleotides and their interactions with the nanoparticle surface. We employed a combination of spectroscopic techniques and liquid transmission electron microscopy to analyze the interactions and conformations adopted by polyAdenine (polyA) and polyThymine (polyT) chains in contact with gold nanoparticles (AuNPs). These studies revealed the presence of AuNP@polyA dimers, with polyA strands forming duplexes, whereas polyT forms isolated strands on the AuNPs. The presence or absence of polyA duplexes on AuNPs can be modulated by external stimuli such as temperature or NaCl. This study contributes to understanding the interactions and secondary structure of oligonucleotides on AuNPs.