Stability of a gold nanoparticle-DNA system in seawater.

We investigated the stability of gold nanoparticles (AuNPs) in seawater. The large amount of Na+, Mg2+, K+, and Ca2+ in seawater makes AuNPs unstable resulting in immediate aggregation. We found that AuNPs become much more stable when they were treated with polyethylene glycol (PEG, MW = 20, 000) before exposure to seawater. The AuNPs maintained stability up to 10 days when they were treated with 16.6% PEG 20000. The AuNP-DNA complex formed in the presence of 3.3% PEG 20000 maintained stability when exposed to seawater. We also demonstrated that the AuNP-DNA complexes can be redispersed after centrifugation and show sequence-specific aggregation in seawater. The results show that the both AuNPs and an AuNP-DNA system can be used in seawater and have the potential to be used to study marine systems.