influence of the aptamer grafting on its conformation and its interaction with targeted protein

Aptamers are functional small single-strand oligonucleotides (dna) that show high affinity to their target molecules such as proteins or small analytes through the formation of specific secondary structures. in the present paper, we study the interaction of one aptamer with its target protein, the manganese superoxide dismutase (mnsod), under specific conditions of surface chemical grafting. for this purpose, we exploit two different chemical strategies to graft the aptamers onto pegylated gold nanoparticles: the carbodiimide chemistry (edc/nhs method) and the thiol covalent bond (s–au bond). we also study the influence of the presence of a spacer of 15 thymine bases at the aptamer extremity. the aptamer interactions with the mnsod were characterized by uv-vis absorption on a large range of mnsod concentrations (from 10−12 up to 10−5 m). we observe that the interaction is strongly dependent on the mnsod concentration and also on the aptamer structure at the surface of the gold nanoparticles. we demonstrate that the highest affinity is obtained for the aptamer with the 15 thymine bases spacer and grafted with the carbodiimide method. we assume that the grafting method has a strong influence on the accessibility and the conformation of the aptamer at the nanoparticle surface and thus on its possibility to interact with the mnsod.