Dissociation and Degradation of Thiol-Modified DNA on Gold Nanoparticles in Aqueous and Organic Solvents

Abstract

Gold nanoparticles functionalized with thiol-modified DNA have been widely used in making various nanostructures, colorimetric biosensors, and drug delivery vehicles. Over the past 15 years, significant progress has been made to improve the stability of such functionalized nanoparticles. The stability of the gold-thiol bond in this system, however, has not been studied in a systematic manner. Most information on the gold-thiol bond was obtained from the study of self-assembled monolayers (SAMs). In this study, we employed two fluorophore-labeled and thiol-modified DNAs. The long-term stability of the thiol-gold bond as a function of time, salt, temperature, pH, and organic solvent has been studied. We found that the bond spontaneously dissociated under all tested conditions. The dissociation was favored at high salt, high pH, high temperature and little DNA degradation was observed in our system. Most organic solvents showed a moderate protection effect on the gold-thiol bond. The stability of the gold-thiol bond in the DNA system was also compared with that in SAMs. While there are many similarities, we also observed opposite trends for the salt and ethanol effect. This study suggests that the purified DNA-functionalized gold nanoparticles should be freshly prepared and used in a day or two. Long term storage should be carried out at relatively low temperature in low salt and slight acidic buffers.

Instantaneous and Quantitative Functionalization of Gold Nanoparticles with Thiolated DNA Using a pH-Assisted and Surfactant-Free Route

“…This iterative process ( Figure 1A) takes 1-2 days to form a stable conjugate, 9,15,16 and the stability of this gold-thiol bond has also been systematically studied. 17,18 This procedure works less well for larger AuNPs (e.g. 50 nm) and it requires even more steps of salt addition.…”

“…Most previous work on tuning the AuNP/DNA interaction employs only salt, 19,[23][24][25] while the effect of pH remains largely unexplored. 18,26 Our discovery reveals a new way to control DNA adsorption, which is quite different from using salt and is likely to find applications in many areas involving AuNPs and DNA. The samples were prepared the same way as in (A) but the free DNAs were removed and AuNPs were re-dispersed in buffers containing 0.3 M NaCl, pH 7.6 or in 1.0 M NaCl, pH 7.6.…”

Optically active histidin-2-ylidene stabilised gold nanoparticles

“…[3][4][5][6][7][8][9] However, a drawback of the Brust method is that the S-Au bond may be strong but is not completely inert, limiting the long term stability of such AuNPs, which is essential for safe and reliable applications. [10][11][12] As such, expanding the toolbox of functional surface anchors will provide unique opportunities for the construction of novel gold nanoparticle interfaces with greater stability. N-heterocyclic carbenes (NHCs) have emerged as attractive alternatives to thiol ligands, as the strong s-donating property of NHC ligands affords stable metal-NHC complexes.…”

Tandem Phosphorothioate Modifications for DNA Adsorption Strength and Polarity Control on Gold Nanoparticles

“…The conjugate stability was assayed in two aspects. First, to study DNA adsorption stability, 39,40 we used glutathione (GSH) as a probe, which is a thiol containing tripeptide found in cells. Since AuNPs are fluorescence quenchers, 8 addition of GSH might displace the adsorbed FAM-labeled DNAs and thus increase fluorescence.…”