Desorption of Noncovalently Adsorbed Oligonucleotides from Gold Nanoparticle Surfaces: Specific Features and Efficiency in the Context of DNA/DNA Detection Systems

Abstract Gold nanoparticles (GNPs) are widely used as carriers for nucleic acids (NAs), which can be attached either covalently or noncovalently, for the detection of various biological targets. When developing GNP-based diagnostic systems, it is important to consider the interactions between the nanoparticle surface, DNA probes, and target sequences, since the phenomenon of coadsorption of DNA probes and targets onto GNPsrather than the expected release (desorption) of specific DNA probe−target complexeshas been reported. In this study, we thoroughly investigated the efficiency of desorption of native single-stranded DNA probes from noncovalent DNA probe/GNP associates (i.e., from the GNP surface) under various conditions. It was shown that DNA probes cannot be quantitatively displaced from the GNP surface by either single-component aqueous solutions such as ammonia, urea, dithiothreitol, glutathione, mercaptoethanol, mercaptoacetamide, or complementary and noncomplementary DNA targets, nor by complex multicomponent mixtures of different compositions. It was found that up to 20% of noncovalently adsorbed native single-stranded DNA oligonucleotides cannot be removed from the surface of freshly prepared citrate-stabilized GNPs, even in the presence of agents with high affinity for gold (thiols) or under conditions that completely suppress certain types of noncovalent DNA−GNP interactions. The relative affinity of DNA for GNPs and the order of DNA addition to the nanoparticles determine both the mechanism and the efficiency of adsorption and desorption processes. The results obtained may contribute to the development of diagnostic systems based on noncovalent DNA probe−GNP assemblies, especially in cases where it is important either to preserve or, conversely, to enable controlled release of DNA probes or their complexes with targets from the nanoparticle surface.