Anchoring effects of surface chemistry on gold nanorods: modulating autophagy.

Gold nanorods (Au NRs) have been receiving extensive attention owing to their extremely attractive properties which make them suitable for various biomedical applications. Au NRs could induce nano-toxicity, but this problem could be turned into therapeutic potential through tuning autophagy. However, the autophagy-inducing activity and mechanism of Au NRs is still unclear. Here we showed that surface chemical modification can tune the autophagy-inducing activity of Au NRs in human lung adenocarcinoma A549 cells. CTAB-coated Au NRs induce remarkable levels of autophagy activity as evidenced by LC3-II conversion and p62 degradation, while PSS- and PDDAC-coated Au NRs barely induce autophagy. More importantly, we also demonstrated that the AKT-mTOR signaling pathway was responsible for CTAB-coated Au NRs-induced autophagy. We further showed that CTAB-coated Au NRs also induce autophagy in human fetal lung fibroblast MRC-5 cells in a time-dependent manner. This study unveils a previously unknown function for Au NRs in autophagy induction, and provides a new insight for designing surface modifications of Au NRs for biomedical applications. [ABSTRACT FROM AUTHOR]