title: Surprises of electron microscopic imaging of proteins and polymers covering gold nanoparticles layer by layer.
abstract: Gold nanoparticles (GNPs) are used in complicated nanoconstructions, and their preparation implies careful analysis of the intermediate and resulting products, including visualisation of the NPs. Visualisation of protein and/or organic polymer covers on GNPs using electron microscopy (EM) was a goal of this study. We covered GNPs with human serum albumin or PEG, and then added a second layer of branched or linear polyethyleneimine. EM studies were supplemented with dynamic light scattering, spectrophotometry and gel electrophoresis, which confirmed the presence and integrity of a cover on GNPs in mixtures with uranylacetate (UA) or phosphotungstic acid (PTA). Covered GNPs were contrasted 'on a drop' or in suspension with UA (pH 4.5) or PTA (pH 0.5, 3.0, 5.0 and 7.0), and studied by transmission EM. A cover on GNPs becomes visible as the result of direct interaction of UA or PTA with the components of a layer. The same NPs could look 'naked' or demonstrate a distinct cover of average electron density. The most distinct images of the layers were obtained using PTA at pH 0.5. Thus, visualisation of protein and/or polymeric layers covering the GNPs by EM depends on the type of contrasting reagent and contrasting conditions, but does not depend on surface charge of the NPs and the chemical nature of a cover.
authors.affiliation: Institute of Chemical Biology and Fundamental Medicine, Siberian Branch of the Russian Academy of Sciences, 8 Lavrent'ev Av., Novosibirsk 630090, Russia. Electronic address: pyshnaya@niboch.nsc.ru.
authors.forename: Inna A
authors.initials: IA
authors.lastname: Pyshnaya
authors.affiliation: Institute of Chemical Biology and Fundamental Medicine, Siberian Branch of the Russian Academy of Sciences, 8 Lavrent'ev Av., Novosibirsk 630090, Russia. Electronic address: kk-kristina@mail.ru.
authors.forename: Kristina V
authors.initials: KV
authors.lastname: Razum
authors.affiliation: Institute of Chemical Biology and Fundamental Medicine, Siberian Branch of the Russian Academy of Sciences, 8 Lavrent'ev Av., Novosibirsk 630090, Russia. Electronic address: dolodoev@mail.ru.
authors.forename: Anton S
authors.initials: AS
authors.lastname: Dolodoev
authors.affiliation: Institute of Chemical Biology and Fundamental Medicine, Siberian Branch of the Russian Academy of Sciences, 8 Lavrent'ev Av., Novosibirsk 630090, Russia. Electronic address: valeriya_ershkova@mail.ru.
authors.forename: Valeriya V
authors.initials: VV
authors.lastname: Shashkova
authors.affiliation: Institute of Chemical Biology and Fundamental Medicine, Siberian Branch of the Russian Academy of Sciences, 8 Lavrent'ev Av., Novosibirsk 630090, Russia. Electronic address: lenryab@yandex.ru.
authors.forename: Elena I
authors.initials: EI
authors.lastname: Ryabchikova
mesh_terms: D004337:Drug Carriers / Q000737:chemistry; D004583:Electrons; D006046:Gold / Q000737:chemistry*; D006801:Humans; D006863:Hydrogen-Ion Concentration; D008027:Light; D053768:Metal Nanoparticles / Q000737:chemistry*; D008854:Microscopy, Electron; D053758:Nanoparticles / Q000737:chemistry; D009942:Organometallic Compounds / Q000737:chemistry; D010772:Phosphotungstic Acid / Q000737:chemistry; D011094:Polyethyleneimine / Q000737:chemistry; D011108:Polymers / Q000737:chemistry*; D011506:Proteins / Q000737:chemistry*; D012542:Scattering, Radiation; D012709:Serum Albumin / Q000737:chemistry; D013056:Spectrophotometry, Ultraviolet
chemical_list: D004337:Drug Carriers; D009942:Organometallic Compounds; D011108:Polymers; D011506:Proteins; D012709:Serum Albumin; D010772:Phosphotungstic Acid; C005460:uranyl acetate; D006046:Gold; D011094:Polyethyleneimine
keywords: Cover visualisation; Electron microscopy; Gold nanoparticles; Phosphotungstic acid and uranylacetate; Protein and organic polymer cover