Bovine serum albumin gold nanoclusters as a potential therapeutic platform against Alzheimer disease

Neurodegenerative diseases are the seventh death cause worldwide, being Alzheimer’s disease the most common. Serum albumin is the main multifunction protein in the blood stream, taking care of the clearance of products from cell metabolism or abnormal machinery. One of them is A beta peptide, involved in the formation of amyloid fibrils, one of the main hallmarks of Alzheimer’s disease. Hence, serum-albumin based therapies may offer an important potential to fight against this disease. Also, small metal nanoparticles with negative surface charge showed an efficient dissembling of preformed amyloid fibrils, so the combination of both components shows a great potential for a possible therapeutic nanoplatform. In the present work we synthesized and characterized small gold nanoclusters embedded in bovine serum albumin by an in-situ synthesis process. Gold metal nanoclusters have unique optical properties due to their small size. They have molecular-like electronic states that produce a large Stokes shift fluorescence phenomenon. Fluorescence Spectroscopy and HRTEM measurements assessed the correct formation of the metal nanoclusters inside the protein. The colloidal stability of the metal cluster-protein complexes was evaluated under different solution conditions (ionic strength and pH for 7 days). The biocompatibility of the nanoclusters-protein complexes was assessed in vitro in different cell lines by means of the CCK-8 viability assay. Finally, the effect of the nanoclusters in the fibrillation process of serum albumin taken as a model fibrillating protein was evaluated to decipher the therapeutical potential of such complexes for intended Alzheimer’s treatment in the future.