INTERACTION OF DNA MOLECULES WITH POLYMERIC NANOPARTICLES FUNCTIONALIZED WITH RARE EARTH OXIDES: A SINGLE-MOLECULE STUDY

This study investigated the interactions involving the physicochemical and structural effects induced in the DNA double helix by supramolecular complexes formed by conjugated polymer nanoparticles (CPNs) of MEH-PPPV (Poly[2-methoxy-5-(2-ethylhexyloxy)-1,4- phenylenevinylene]) and PFD (Poly(9,9- di-n-dodecyl fluorenyl-2,7-diyl)) coated with rare earth oxides (OTRs):  Yb₂O₃- ytterbium, Nd₂O₃ - neodymium and Eu₂O₃ - europium. CPNs and OTRs have wide-ranging applications in the field of biomedicine due to their luminescent optical properties and their affinity for biomolecules. Using the optical tweezers technique, binding parameters were quantified in a near-physiological medium (PBS, pH 7.4). The quenched-disorder statistical model combined with the Hill isotherm converted the mechanical properties obtained by single-molecule spectroscopy into physicochemical parameters, such as the affinity constant and the Hill exponent. The data demonstrated that functionalizing the nanoparticles with OTRs increased their affinity constant for the DNA molecule compared to the separate components. The force-extension curves show that the contour length (L) remained unchanged as the concentrations of the analyzed complexes increased, while the persistence length (A) exhibited changes that depended on the complex being analyzed, confirming interactions with the DNA molecule. Therefore, the functionalization of CPNs with rare-earth oxides modulates the interaction mechanism and the rigidity of the DNA double helix, showing promise for the engineering of drug carriers and applications in DNA nanotechnology.

This work was supported by Conselho Nac. Des. Cient. Tecnologico (CNPq #305185/2022-5), Fundação de Amparo à Pesquisa do Estado de Minas Gerais(FAPEMIG APQ-04822-23) and by Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES Code 001).