title: A microscopy method for scanning transmission electron microscopy imaging of the antibacterial activity of polymeric nanoparticles on a biofilm with an ionic liquid.
abstract: In this study, we developed a scanning transmission electron microscopy (STEM) method for imaging the antibacterial activity of organic polymeric nanoparticles (NPs) toward biofilms formed by Staphylococcus epidermidis bacterial cells, for optimizing NPs to treat biofilm infections. The combination of sample preparation method using a hydrophilic ionic liquid (IL) and STEM observation using the cooling holder eliminates the need for specialized equipment and techniques for biological sample preparation. The annular dark-field STEM results indicated that the two types of biodegradable poly-(DL-lactide-co-glycolide) (PLGA) NPs: PLGA modified with chitosan (CS), and clarithromycin (CAM)-loaded + CS-modified PLGA, prepared by emulsion solvent diffusion exhibited different antibacterial activities in nanoscale. To confirm damage to the sample during STEM observation, we observed the PLGA NPs and the biofilm treated with PLGA NPs by both the conventional method and the newly developed method. The optimized method allows microstructure of the biofilm treated with PLGA NPs to be maintained for 25 min at a current flow of 40 pA. The developed simple sample preparation method would be helpful to understand the interaction of drugs with target materials. In addition, this technique could contribute to the visualization of other deformable composite materials at the nanoscale level. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 1432-1437, 2017.
authors.affiliation: Pharmaceutical Engineering, School of Pharmacy, Aichi Gakuin University, Nagoya, Aichi, Japan.
authors.forename: Chisato
authors.initials: C
authors.lastname: Takahashi
authors.affiliation: Institute of Materials and Systems for Sustainability, Nagoya University, Nagoya, Aichi, Japan.
authors.forename: Shunsuke
authors.initials: S
authors.lastname: Muto
authors.affiliation: Pharmaceutical Engineering, School of Pharmacy, Aichi Gakuin University, Nagoya, Aichi, Japan.
authors.forename: Hiromitsu
authors.initials: H
authors.lastname: Yamamoto
mesh_terms: D000900:Anti-Bacterial Agents / Q000737:chemistry / Q000494:pharmacology; D018441:Biofilms / Q000187:drug effects*; D048271:Chitosan / Q000737:chemistry / Q000494:pharmacology; D052578:Ionic Liquids / Q000737:chemistry / Q000494:pharmacology; D019344:Lactic Acid / Q000737:chemistry / Q000494:pharmacology; D017348:Microscopy, Electron, Scanning Transmission; D053758:Nanoparticles / Q000737:chemistry* / Q000648:ultrastructure; D011100:Polyglycolic Acid / Q000737:chemistry / Q000494:pharmacology; D000077182:Polylactic Acid-Polyglycolic Acid Copolymer; D013212:Staphylococcus epidermidis / Q000502:physiology / Q000648:ultrastructure
chemical_list: D000900:Anti-Bacterial Agents; D052578:Ionic Liquids; D000077182:Polylactic Acid-Polyglycolic Acid Copolymer; D011100:Polyglycolic Acid; D019344:Lactic Acid; D048271:Chitosan
keywords: antimicrobial; biodegradation; drug delivery/release; electron microscopy; measurement/assessment