A colorimetric method for assessing the adsorption strength of oligonucleotides on noble metal nanoparticles

Oligonucleotide-functionalizing noble metal nanoparticles (NMNPs) have resulted in many interesting applications in engineering, as well as in medicine. Typically, NMNPs are functionalized via thiol-metal interaction using thiol-labeled oligonucleotides. Previous studies have revealed that strong interactions exist between oligonucleotide bases and noble metal surface and these interactions are sequence-dependent. This has provided an alternative way to functionalize NMNPs with unlabeled oligonucleotides. In order to fully utilize the spontaneous interactions between oligonucleotides and NMNPs, quantitative assessment of the interaction strength between different oligonucleotides and NMNPs will be necessary. Existing methods that have been used to determine the interaction strength usually rely on direct quantification of the amount of oligonucleotides adsorbed on NMNPs, and tend to be labor- and time-consuming. Herein we develop a salt titration based colorimetric method as a simple and high-throughput alternative to the existing methods. First, this new method was demonstrated by applying to determine the dissociation constant between gold nanoparticles and DNA oligonucleotides. Then the new method was used to study the sequence and length dependence of NMNP-oligonucleotide interactions.