Regulating self-assembly of oligonucleotide on gold nanoparticles by ligand-exchange

Agarose gel electrophoresis was used to characterize the results of ligand -exchange. The ligand-exchange strategy was used to regulate the self-assembly of oligonucleotide on 10 nm gold nanoparticles with 4-mercaptobenzoic acid ( MBA) and 6-mercapto-1 -hexanol ( MCH), as the regulating molecule. The results show that the naked gold nanoparticles modified with MCH lead to irreversible aggregation but the gold nanoparticles modified with DNA and MBA are stable in solution, which impliedes that the negative charge of DNA and MBA molecules is critical in stabilizing gold nanoparticles. Both MBA and MCH can replace DNA on the surface of gold nanoparticles. The difference is that MCH can thoroughly replace the DNA on the surface of gold nanoparticles but MBA could not. At the molar ratio of MCH/gold nanoparticles = 2400/1, the aggregation of gold nanoparticles is found. It is also found that the ligand-exchange reaction of using MBA as in-coming ligands and DNA as out-coming ligands is much difficult than using DNA as in-coming ligands and MBA as out-coming ligands.