Comparison of MoS₂, WS₂, and Graphene Oxide for DNA Adsorption and Sensing

Interfacing DNA with two-dimensional (2D) materials has been intensely researched for various analytical and biomedical applications. Most of these studies have been performed on graphene oxide (GO) and two metal dichalcogenides, molybdenum disulfide (MoS₂) and tungsten disulfide (WS₂); all of them can all adsorb single-stranded DNA. However, they use different surface forces for adsorption based on their chemical structures. In this work, fluorescently labeled DNA oligonucleotides were used and their adsorption capacities and kinetics were studied as a function of ionic strength, DNA length, and sequence. Desorption of DNA from these surfaces was also measured. DNA is more easily desorbed from GO by various denaturing agents, whereas surfactants yield more desorption from MoS₂ and WS₂. Our results are consistent with the fact that DNA can be adsorbed by GO via π-π stacking and hydrogen bonding, and MoS₂ and WS₂ mainly use van der Waals force for adsorption. Finally, fluorescent DNA probes were adsorbed by these 2D materials for detecting complementary DNA. For this assay, GO gave the highest sensitivity, whereas they all showed a similar detection limit. This study has enhanced our fundamental understanding of DNA adsorption by two important types of 2D materials and is useful for further rational optimization of their analytical and biomedical applications.