Novel bio-friendly and non-toxic thiocarbohydrate stabilizers of gold nanoparticles

Several bio-friendly carbohydrate disulfides and thiocarbohydrates have been synthesized via the reaction of d-(+)-gluconic acid δ-lactone with aminoalkylthiols, leading to n-gluconamidoalkyldisulfides {di-(2-gluconamidoethyl)disulfide (L1), di(3-gluconamidopropyl)-disulfide (L2), di(4-gluconamidobutyl) disulfide (L3) and (2-gluconamidoethyl)thiol (L4)}. Acetylation of hydroxy groups in L1-L3 and subsequent reduction produced the following disulfides and thiols: acetylated di(2-gluconamidoethyl)disulfide (L5), acetylated di(3-gluconamidopropyl)disulfide (L6), acetylated di(4-gluconamidobutyl)disulfide (L7), acetylated di(2-gluconamidoethyl)thiol (L8), acetylated di(3-gluconamidopropyl)thiol (L9) and acetylated di(4-gluconamidobutyl)thiol (L10). Compounds L1-L10 were characterized by combination of NMR and infrared spectroscopy, microanalysis, mass spectrometry and in a selected case X-ray crystallographic data. These thiocarbohydrate compounds were used to stabilize gold nanoparticles to gold glyconanoparticles (AuNPs) of sizes in the range of ca. 2-9 nm. The thiocrabohydrates are non-toxic toward both cancer and normal cell lines and have IC₅₀ values generally ≥200 μM.