title: Gold Nanoparticles Inhibit Matrix Metalloproteases without Cytotoxicity.
abstract: Nanoparticles (NPs) are currently the focus of considerable attention for dental applications; however, their biological effects have not been fully elucidated. The long-term, slow release of matrix metalloproteases (MMPs) digests collagen fibrils within resin-dentin bonds. Therefore, MMP inhibitors can prolong the durability of resin-dentin bonds. However, there have been few reports evaluating the combined effect of MMP inhibition and the cytotoxic effects of NPs for dentin bonding. The aim of this study was to evaluate MMP inhibition and cytotoxic responses to gold (AuNPs) and platinum nanoparticles (PtNPs) stabilized by polyvinylpyrrolidone (PVP) in cultured murine macrophages (RAW264) by using MMP inhibition assays, measuring cell viability and inflammatory responses (quantitative reverse transcription polymerase chain reaction [RT-qPCR]), and conducting a micromorphological analysis by fluorescence and transmission electron microscopy. Cultured RAW264 cells were exposed to metal NPs at various concentrations (1, 10, 100, and 400 µg/mL). AuNPs and PtNPs markedly inhibited MMP-8 and MMP-9 activity. Although PtNPs were cytotoxic at high concentrations (100 and 400 µg/mL), no cytotoxic effects were observed for AuNPs at any concentration. Transmission electron microscopy images showed a significant nonrandom intercellular distribution for AuNPs and PtNPs, which were mostly observed to be localized in lysosomes but not in the nucleus. RT-qPCR analysis demonstrated inflammatory responses were not induced in RAW264 cells by AuNPs or PtNPs. The cytotoxicity of nanoparticles might depend on the core metal composition and arise from a "Trojan horse" effect; thus, MMP inhibition could be attributed to the surface charge of PVP, which forms the outer coating of NPs. The negative charge of the surface coating of PVP binds to Zn(2+) from the active center of MMPs by chelate binding and results in MMP inhibition. In summary, AuNPs are attractive NPs that effectively inhibit MMP activity without cytotoxicity or inflammatory responses.
authors.affiliation: Department of Biomaterials Science, Osaka University, Graduate School of Dentistry, Osaka, Japan masanori-h@mue.biglobe.ne.jp.
authors.forename: M
authors.initials: M
authors.lastname: Hashimoto
authors.affiliation: Department of Biomaterials Science, Osaka University, Graduate School of Dentistry, Osaka, Japan.
authors.forename: J I
authors.initials: JI
authors.lastname: Sasaki
authors.affiliation: Department of Biomaterials Science, Osaka University, Graduate School of Dentistry, Osaka, Japan.
authors.forename: S
authors.initials: S
authors.lastname: Yamaguchi
authors.affiliation: Miyoshi Oil & Fat Co., Ltd., Tokyo, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Kawai
authors.affiliation: Miyoshi Oil & Fat Co., Ltd., Tokyo, Japan.
authors.forename: H
authors.initials: H
authors.lastname: Kawakami
authors.affiliation: Division of Chemistry and Materials Engineering, Faculty of Chemistry, Materials and Bioengineering, Kansai University, Osaka, Japan.
authors.forename: Y
authors.initials: Y
authors.lastname: Iwasaki
authors.affiliation: Department of Biomaterials Science, Osaka University, Graduate School of Dentistry, Osaka, Japan.
authors.forename: S
authors.initials: S
authors.lastname: Imazato
mesh_terms: D000818:Animals; D002470:Cell Survival / Q000187:drug effects; D006046:Gold / Q000737:chemistry* / Q000633:toxicity*; D006801:Humans; D007150:Immunohistochemistry; D008264:Macrophages / Q000187:drug effects*; D061965:Matrix Metalloproteinase Inhibitors / Q000737:chemistry* / Q000633:toxicity*; D051379:Mice; D046529:Microscopy, Electron, Transmission; D008856:Microscopy, Fluorescence; D053758:Nanoparticles / Q000737:chemistry* / Q000633:toxicity*; D010984:Platinum / Q000737:chemistry / Q000633:toxicity; D011205:Povidone / Q000737:chemistry / Q000633:toxicity; D020133:Reverse Transcriptase Polymerase Chain Reaction
chemical_list: D061965:Matrix Metalloproteinase Inhibitors; D010984:Platinum; D006046:Gold; D011205:Povidone
keywords: adhesives; biocompatibility; dental; electron microscopy; nanotechnology; restorative dentistry