title: Tailoring Enzyme-Like Activities of Gold Nanoclusters by Polymeric Tertiary Amines for Protecting Neurons Against Oxidative Stress.
abstract: The cytotoxicity of nanozymes has drawn much attention recently because their peroxidase-like activity can decompose hydrogen peroxide (H2 O2 ) to produce highly toxic hydroxyl radicals (•OH) under acidic conditions. Although catalytic activities of nanozymes are highly associated with their surface properties, little is known about the mechanism underlying the surface coating-mediated enzyme-like activities. Herein, it is reported for the first time that amine-terminated PAMAM dendrimer-entrapped gold nanoclusters (AuNCs-NH2 ) unexpectedly lose their peroxidase-like activity while still retaining their catalase-like activity in physiological conditions. Surprisingly, the methylated form of AuNCs-NH2 (i.e., MAuNCs-N(+) R3 , where R = H or CH3 ) results in a dramatic recovery of the intrinsic peroxidase-like activity while blocking most primary and tertiary amines (1°- and 3°-amines) of dendrimers to form quaternary ammonium ions (4°-amines). However, the hidden peroxidase-like activity is also found in hydroxyl-terminated dendrimer-encapsulated AuNCs (AuNCs-OH, inside backbone with 3°-amines), indicating that 3°-amines are dominant in mediating the peroxidase-like activity. The possible mechanism is further confirmed that the enrichment of polymeric 3°-amines on the surface of dendrimer-encapsulated AuNCs provides sufficient suppression of the critical mediator •OH for the peroxidase-like activity. Finally, it is demonstrated that AuNCs-NH2 with diminished cytotoxicity have great potential for use in primary neuronal protection against oxidative damage.
authors.affiliation: Institute of Biomedical Engineering and Nanomedicine, National Health Research Institutes, 35 Keyan Road, Zhunan, 350, Taiwan.|Department of Chemistry, Fu Jen Catholic University, 510 Zhongzheng Road, Xinzhuang District, New Taipei City, 242, Taiwan.
authors.forename: Ching-Ping
authors.initials: CP
authors.lastname: Liu
authors.affiliation: Institute of Biomedical Engineering and Nanomedicine, National Health Research Institutes, 35 Keyan Road, Zhunan, 350, Taiwan.
authors.forename: Te-Haw
authors.initials: TH
authors.lastname: Wu
authors.affiliation: Institute of Biomedical Engineering and Nanomedicine, National Health Research Institutes, 35 Keyan Road, Zhunan, 350, Taiwan.
authors.forename: Yu-Lung
authors.initials: YL
authors.lastname: Lin
authors.affiliation: Institute of Biomedical Engineering and Nanomedicine, National Health Research Institutes, 35 Keyan Road, Zhunan, 350, Taiwan.
authors.forename: Chia-Yeh
authors.initials: CY
authors.lastname: Liu
authors.affiliation: Institute of Anatomy and Cell Biology, School of Medicine, National Yang-Ming University, 155, Sec. 2, Linong Street, Taipei, 112, Taiwan.
authors.forename: Sabrina
authors.initials: S
authors.lastname: Wang
authors.affiliation: Institute of Biomedical Engineering and Nanomedicine, National Health Research Institutes, 35 Keyan Road, Zhunan, 350, Taiwan.
authors.forename: Shu-Yi
authors.initials: SY
authors.lastname: Lin
mesh_terms: D000588:Amines / Q000737:chemistry* / Q000494:pharmacology*; D000818:Animals; D050091:Dendrimers / Q000737:chemistry; D006046:Gold / Q000737:chemistry*; D006801:Humans; D006861:Hydrogen Peroxide / Q000494:pharmacology; D053768:Metal Nanoparticles / Q000737:chemistry*; D009474:Neurons / Q000187:drug effects* / Q000378:metabolism*; D010084:Oxidation-Reduction / Q000187:drug effects; D018384:Oxidative Stress / Q000187:drug effects; D011108:Polymers / Q000737:chemistry*; D017382:Reactive Oxygen Species / Q000378:metabolism
chemical_list: D000588:Amines; D050091:Dendrimers; C104700:PAMAM Starburst; D011108:Polymers; D017382:Reactive Oxygen Species; D006046:Gold; D006861:Hydrogen Peroxide
keywords: catalase; dendrimer; gold nanoclusters; peroxidase; surface properties