Thioctic acid, also known as α-lipoic acid, is a fatty acid containing two sulfur atoms. In their oxidized state, these atoms form a disulfide bond. In its protonated form, thioctic acid contains two thiol groups. These thiol groups can be used to conjugate oligos and other biomolecules to the surfaces of gold nanoparticles (AuNP). Immobilized as such, oligos can be used in biosensors and similar technologies. The presence of two sulfur atoms per molecule significantly strengthens the bond to gold compared to a simple thiol group. Even immobilization on silver nanoparticles (AgNP), which is highly unstable with simple thiols, becomes possible with thioctic acid.

Literature:

1. Enhanced oligonucleotide–nanoparticle conjugate stability using thioctic acid modified oligonucleotides. Dougan JA, Karlsson C, Smith EW, Graham D; Nucl. Acids Res. (2007), Vol. 35, No.11 3668-75. doi: 10.1093/nar/gkm237.