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Biosensors & Bioelectronics Oct 2023Viruses have unique coat proteins that are genetically modifiable. Their surface can serve as a nano-template on which electroactive molecules are immobilized. In this...
Viruses have unique coat proteins that are genetically modifiable. Their surface can serve as a nano-template on which electroactive molecules are immobilized. In this study, we report filamentous bacteriophage as a backbone to which redox mediators are covalently and densely tethered, constructing redox nanowire, i.e. an electron conducting biomaterial. The highly ordered coat proteins of a filamentous bacteriophage provide flexible and biocompatible platform to constitute a biohybrid redox nanowire. Incorporating bacteriophage and redox molecules form an entangled assembly of nanowires enabling facile electron transfer. Electron transfer among the molecular mediators in the entangled assembly originates apparent electron diffusion of which the electron transfer rate is comparable to that observed in conventional redox polymers. Programming peptide terminals suggests further enhancement in electron mediation by increasing redox species mobility. In addition, the redox nanowire film functions as a favorable matrix for enzyme encapsulation. The stability of the enzymes entrapped in this unique matrix is substantially improved.
Topics: Nanowires; Biosensing Techniques; Oxidation-Reduction; Electron Transport; Bacteriophages; Electrodes
PubMed: 37442029
DOI: 10.1016/j.bios.2023.115518 -
Microscopy Research and Technique Apr 2021Lobomycosis is a skin infection produced by the fungus Lacazia loboi, which mainly affects some indigenous and afro-descendant populations in Tropical America. We...
Lobomycosis is a skin infection produced by the fungus Lacazia loboi, which mainly affects some indigenous and afro-descendant populations in Tropical America. We previously reported the comparative effect of osmium tetroxide (OsO ) and ruthenium tetroxide (RuO ) in the electron microscopy (EM) of other related microorganisms. The objective of this study is to compare the effect of postfixation with OsO and RuO in the ultrastructure of L. loboi yeasts. Skin biopsies on patients diagnosed with lobomycosis were fixed in glutaraldehyde at 3% and postfixed in the following solutions: (a) 1% OsO , (b) 0.2% RuO , and (c) OsO at 1% followed by RuO at 0.2%. They were then processed using the conventional method for EM. Unlike OsO the treatment with RuO revealed different shades of gray and electron dense bands in the cell wall and other cell components of L. loboi. The most notable finding was the presence of radial filamentous structures around the yeast, which made the image look like the sun. Postfixation with RuO revealed ultrastructural details that had not been previously reported for L loboi. The combined use of OsO and RuO in EM of microorganisms with cell walls can be useful to evaluate the effect of microbicide substances.
Topics: Humans; Lacazia; Microscopy, Electron; Osmium Tetroxide; Ruthenium Compounds
PubMed: 33176034
DOI: 10.1002/jemt.23638 -
Inorganic Chemistry Aug 2021Metal-coordination-driven C-C bond functionalization without involvement of the traditional route of oxidative addition, insertion, and reductive elimination has gained...
Metal-coordination-driven C-C bond functionalization without involvement of the traditional route of oxidative addition, insertion, and reductive elimination has gained immense importance. In this context, the present Communication highlights the facile ring contraction process of the deprotonated bis-lawsone (L) to functionalized L1 upon coordination to {Os(bpy)} or isomeric {Os(pap)} (bpy = 2,2'-bipyridine and pap = 2-phenylazopyridine) in -. Further, recognition of fractional redox noninnocence of L1 in - via experimental and theoretical events facilitated its inclusion in the redox noninnocent family.
PubMed: 34310111
DOI: 10.1021/acs.inorgchem.1c01680 -
Scientific Reports Oct 2022Characterization of brain infarct lesions in rodent models of stroke is crucial to assess stroke pathophysiology and therapy outcome. Until recently, the analysis of...
Characterization of brain infarct lesions in rodent models of stroke is crucial to assess stroke pathophysiology and therapy outcome. Until recently, the analysis of brain lesions was performed using two techniques: (1) histological methods, such as TTC (Triphenyltetrazolium chloride), a time-consuming and inaccurate process; or (2) MRI imaging, a faster, 3D imaging method, that comes at a high cost. In the last decade, high-resolution micro-CT for 3D sample analysis turned into a simple, fast, and cheaper solution. Here, we successfully describe the application of brain contrasting agents (Osmium tetroxide and inorganic iodine) for high-resolution micro-CT imaging for fine location and quantification of ischemic lesion and edema in mouse preclinical stroke models. We used the intraluminal transient MCAO (Middle Cerebral Artery Occlusion) mouse stroke model to identify and quantify ischemic lesion and edema, and segment core and penumbra regions at different time points after ischemia, by manual and automatic methods. In the transient-ischemic-attack (TIA) mouse model, we can quantify striatal myelinated fibers degeneration. Of note, whole brain 3D reconstructions allow brain atlas co-registration, to identify the affected brain areas, and correlate them with functional impairment. This methodology proves to be a breakthrough in the field, by providing a precise and detailed assessment of stroke outcomes in preclinical animal studies.
Topics: Animals; Mice; Osmium Tetroxide; X-Ray Microtomography; Stroke; Infarction, Middle Cerebral Artery; Disease Models, Animal; Iodine
PubMed: 36261475
DOI: 10.1038/s41598-022-21494-9 -
Histochemistry and Cell Biology Apr 2022High-pressure freezing followed by freeze-substitution is a valuable method for ultrastructural analyses of resin-embedded biological samples. The visualization of lipid...
High-pressure freezing followed by freeze-substitution is a valuable method for ultrastructural analyses of resin-embedded biological samples. The visualization of lipid membranes is one of the most critical aspects of any ultrastructural study and can be especially challenging in high-pressure frozen specimens. Historically, osmium tetroxide has been the preferred fixative and staining agent for lipid-containing structures in freeze-substitution solutions. However, osmium tetroxide is not only a rare and expensive material, but also volatile and toxic. Here, we introduce the use of a combination of potassium permanganate, uranyl acetate, and water in acetone as complementing reagents during the freeze-substitution process. This mix imparts an intense en bloc stain to cellular ultrastructure and membranes, which makes poststaining superfluous and is well suited for block-face imaging. Thus, potassium permanganate can effectively replace osmium tetroxide in the freeze-substitution solution without sacrificing the quality of ultrastructural preservation.
Topics: Freeze Substitution; Freezing; Lipids; Osmium Tetroxide; Potassium Permanganate
PubMed: 34984524
DOI: 10.1007/s00418-021-02070-0 -
Dalton Transactions (Cambridge, England... Aug 2019The biological activities of aminoguanidine (GNH) and its derivatives have been extensively studied due to their properties as radical scavengers and antioxidants. Some...
The biological activities of aminoguanidine (GNH) and its derivatives have been extensively studied due to their properties as radical scavengers and antioxidants. Some of their biological activities may result from their binding to various metals present in biological systems. However, the reactivity of coordinated aminoguanidines has not been investigated. We report herein the synthesis, structure and reactivity of a novel osmium(iii) complex bearing the parent aminoguanidine, mer-[Os{NHC(NH)(NHNH)}(L)(CN)] (OsGNH, HL = 2-(2-hydroxyphenyl)benzoxazole). The antioxidant properties of OsGNH have been investigated by reactions with various oxidants, including O, HO, m-chloroperbenzoic acid (m-CPBA) and Ce(iv). Various osmium products are produced, which depend on the type of oxidant used. OsGNH is readily oxidized by O or HO under ambient conditions to afford an osmium(iii) formamidine complex, [Os(NHC[double bond, length as m-dash]NH)(L)(CN)] (OsFA, FA = formamidine). With m-CPBA, the nitrosyl complex, mer-[Os(NO)(L)(CN)] (OsNO), is formed instead. On the other hand, the nitrido complex mer-[Os(N)(L)(CN)] (OsN) is produced when the one-electron oxidant (NH)[Ce(NO)] (Ce(iv)) is employed. The molecular structures of OsGNH and OsFA have been determined by X-ray crystallography. The oxidation of OsGNH to OsFA by O or HO is proposed to go through initial dehydrogenation to give a diazoamidine intermediate. In the oxidation by m-CPBA and Ce(iv), it is proposed that the initially formed OsFA is further oxidized to OsNO and OsN, respectively, via osmium(iii) hydrogen cyanamido and osmium(iv) cyanoimido intermediates.
PubMed: 31282913
DOI: 10.1039/c9dt01711a -
International Journal of Molecular... Oct 2022Interest in the third-row transition metal osmium and its compounds as potential anticancer agents has grown in recent years. Here, we synthesized the osmium(VI) nitrido...
Interest in the third-row transition metal osmium and its compounds as potential anticancer agents has grown in recent years. Here, we synthesized the osmium(VI) nitrido complex (tpm = [5-(Thien-2-yl)-1H-pyrazol-3-yl]methanol), which exhibited a greater inhibitory effect on the cell viabilities of the cervical, ovarian, and breast cancer cell lines compared with cisplatin. Proteomics analysis revealed that modulates the expression of protein-transportation-associated, DNA-metabolism-associated, and oxidative-stress-associated proteins in HepG2 cells. Perturbation of protein expression activity by the complex in cancer cells affects the functions of the mitochondria, resulting in high levels of cellular oxidative stress and low rates of cell survival. Moreover, it caused G2/M phase cell cycle arrest and caspase-mediated apoptosis of HepG2 cells. This study reveals a new high-valent osmium complex as an anticancer agent candidate modulating protein homeostasis.
Topics: Humans; Osmium; Hep G2 Cells; Proteostasis; Antineoplastic Agents; Apoptosis; Cell Line, Tumor
PubMed: 36361570
DOI: 10.3390/ijms232112779 -
Inorganic Chemistry Sep 2022The synthesis and photophysical characterization of two osmium(II) polypyridyl complexes, [Os(TAP)dppz] () and [Os(TAP)dppp2] () containing dppz...
The synthesis and photophysical characterization of two osmium(II) polypyridyl complexes, [Os(TAP)dppz] () and [Os(TAP)dppp2] () containing dppz (dipyrido[3,2-:2',3'-]phenazine) and dppp2 (pyrido[2',3':5,6]pyrazino[2,3-][1,10]phenanthroline) intercalating ligands and TAP (1,4,5,8-tetraazaphenanthrene) ancillary ligands, are reported. The complexes exhibit complex electrochemistry with five distinct reductive redox couples, the first of which is assigned to a TAP-based process. The complexes emit in the near-IR ( at 761 nm and at 740 nm) with lifetimes of >35 ns with a low quantum yield of luminescence in aqueous solution (∼0.25%). The Δ and Λ enantiomers of and are found to bind to natural DNA and with AT and GC oligodeoxynucleotides with high affinities. In the presence of natural DNA, the visible absorption spectra are found to display significant hypochromic shifts, which is strongly evident for the ligand-centered π-π* dppp2 transition at 355 nm, which undergoes 46% hypochromism. The emission of both complexes increases upon DNA binding, which is observed to be sensitive to the Δ or Λ enantiomer and the DNA composition. A striking result is the sensitivity of Λ- to the presence of AT DNA, where a 6-fold enhancement of luminescence is observed and reflects the nature of the binding for the enantiomer and the protection from solution. Thermal denaturation studies show that both complexes are found to stabilize natural DNA. Finally, cellular studies show that the complexes are internalized by cultured mammalian cells and localize in the nucleus.
Topics: Animals; DNA; Intercalating Agents; Ligands; Mammals; Oligodeoxyribonucleotides; Osmium; Phenanthrolines; Phenazines; Ruthenium
PubMed: 36094851
DOI: 10.1021/acs.inorgchem.2c01231 -
Chemical Science Dec 2022By combining the energy input from two red photons, chemical reactions that would normally require blue or ultraviolet irradiation become accessible. Key advantages of...
By combining the energy input from two red photons, chemical reactions that would normally require blue or ultraviolet irradiation become accessible. Key advantages of this biphotonic excitation strategy are that red light usually penetrates deeper into complex reaction mixtures and causes less photo-damage than direct illumination in the blue or ultraviolet. Here, we demonstrate that the primary light-absorber of a dual photocatalytic system comprised of a transition metal-based photosensitizer and an organic co-catalyst can completely alter the reaction outcome. Photochemical reductions are achieved with a copper(i) complex in the presence of a sacrificial electron donor, whereas oxidative substrate activation occurs with an osmium(ii) photosensitizer. Based on time-resolved laser spectroscopy, this changeover in photochemical reactivity is due to different underlying biphotonic mechanisms. Following triplet energy transfer from the osmium(ii) photosensitizer to 9,10-dicyanoanthracene (DCA) and subsequent triplet-triplet annihilation upconversion, the fluorescent singlet excited state of DCA triggers oxidative substrate activation, which initiates the to isomerization of an olefin, a [2 + 2] cycloaddition, an aryl ether to ester rearrangement, and a Newman-Kwart rearrangement. This oxidative substrate activation stands in contrast to the reactivity with a copper(i) photosensitizer, where photoinduced electron transfer generates the DCA radical anion, which upon further excitation triggers reductive dehalogenations and detosylations. Our study provides the proof-of-concept for controlling the outcome of a red-light driven biphotonic reaction by altering the photosensitizer, and this seems relevant in the greater context of tailoring photochemical reactivities.
PubMed: 36605743
DOI: 10.1039/d2sc05229f -
Inorganic Chemistry Frontiers Jun 2022We disclose novel amphiphilic ruthenium and osmium complexes that auto-assemble into nanomedicines with potent antiproliferative activity by inhibition of mitochondrial...
We disclose novel amphiphilic ruthenium and osmium complexes that auto-assemble into nanomedicines with potent antiproliferative activity by inhibition of mitochondrial respiration. The self-assembling units were rationally designed from the [M(-cymene)(1,10-phenanthroline)Cl]PF motif (where M is either Ru or Os) with an appended C fatty chain to achieve high cellular activity, nano-assembling and mitochondrial targeting. These amphiphilic complexes block cell proliferation at the sub-micromolar range and are particularly potent towards glioblastoma neurospheres made from patient-derived cancer stem cells. A subcutaneous mouse model using these glioblastoma stem cells highlights one of our C Os nanomedicines as highly successful . Mechanistically, we show that they act as metabolic poisons, strongly impairing mitochondrial respiration, corroborated by morphological changes and damage to the mitochondria. A genetic strategy based on RNAi gave further insight on the potential involvement of microtubules as part of the induced cell death. In parallel, we examined the structural properties of these new amphiphilic metal-based constructs, their reactivity and mechanism.
PubMed: 36311556
DOI: 10.1039/d2qi00423b