Gold Nanoparticles Adsorb DNA and Aptamer Probes Too Strongly and a Comparison with Graphene Oxide for Biosensing

Using fluorescently labeled DNA oligonucleotides and nanomaterials for developing biosensors has been extensively reported for gold nanoparticles (AuNPs) and graphene oxide (GO) among others. These materials have vastly different affinities and mechanisms for interacting with DNA, and their analytical performance is likely to be different. In this work, we used several DNA sequences and, respectively, adsorbed them on AuNPs and GO to quench fluorescence. Different from previous work, we used KCN to fully dissolve the AuNPs to calculate the percentage of the desorbed DNA due to the complementary DNA (cDNA) and aptamer target. The desorbed probe DNA from the AuNPs was less than 5% for all of the targets including DNA, adenosine, Hg²⁺, and lysozyme, indicating a very strong DNA adsorption affinity. Desorption of DNA was achieved by adding HEPES buffer, NaCl, and As(III), but such desorption was attributed to the adsorption of these molecules or ions by the AuNPs instead of their interaction with the adsorbed DNA. For GO, more probes desorbed with addition of target analytes but so did nonspecific desorption by random DNA and proteins. In summary, AuNPs are unlikely to be a good surface for developing biosensors relying solely on the desorption of probe DNA, while for GO the main problem is nonspecific desorption.