Amyloid fibrils enhance transport of metal nanoparticles in living cells and induced cytotoxicity.

Amyloid protein fibrils occur in vivo as pathological agents, in the case of neurodegenerative diseases, or as functional amyloids, when playing biologically vital roles. Here we show how amyloid fibrils generated from a food protein, β-lactoglobulin, can be used as nanoreactors for the synthesis of metal nanoparticles and demonstrate that the resulting hybrids can play a central role in the internalization of nanoparticles into living cells, with up to 3-fold-enhanced transport properties over pristine nanoparticles. We conjugate gold, silver, and palladium nanoparticles onto amyloid fibrils by chemical reduction, and we study their effect on dendritic and MCF7 breast cancer cells. Transmission electron microscopy indicates localization of nanoparticles inside vesicles of the cells. Flow cytometry reveals that silver nanoparticle-amyloid hybrids are cytotoxic, while gold and palladium nanoparticle-amyloid hybrids produce no notable effect on cell viability and activation status.