Molybdenum trioxide nanoparticles with intrinsic sulfite oxidase activity

Sulfite oxidase is a mitochondria-located molybdenum-containing enzyme catalyzing the oxidation of sulfite to sulfate in the amino acid and lipid metabolism. Therefore, it plays a major role in detoxification processes, where defects in the enzyme cause a severe infant disease leading to early death with no efficient or cost-effective therapy in sight. Here we report that molybdenum trioxide (MoO3) nanoparticles display an intrinsic biomimetic sulfite oxidase activity under physiological conditions, and, functionalized with a customized bifunctional ligand containing dopamine as anchor group and triphenylphosphonium ion as targeting agent, they selectively target the mitochondria while being highly dispersible in aqueous solutions. Chemically induced sulfite oxidase knockdown cells treated with MoO3 nanoparticles recovered their sulfite oxidase activity in vitro, which makes MoO3 nanoparticles a potential therapeutic for sulfite oxidase deficiency and opens new avenues for cost-effective therapies for gene-induced deficiencies.