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In the current research, catalytic effectiveness of synchrotron and synchrocyclotron radiations on Osmium Dioxide (OsO2) and Osmium Tetroxide (OsO4) nano capsules delivery in DNA/RNA of cancer cells is investigated. The calculation of thickness and optical constants of Osmium Dioxide (OsO2) and Osmium Tetroxide (OsO4) catalytic effectiveness of synchrotron and synchrocyclotron radiations on Osmium Dioxide (OsO2) and Osmium Tetroxide (OsO4) nano capsules delivery in DNA/RNA of cancer cells produced using sol-gel method over glassy medium through a single reflection spectrum is presented. To obtain an appropriate fit for reflection spectrum, the classic Drudge-Lorentz model for parametric di–electric function is used. The best fitting parameters are determined to simulate the reflection spectrum using Levenberg-Marquardt optimization method. The simulated reflectivity from the derived optical constants and thickness are in good agreement with experimental results. Keywords:Catalytic Effectiveness; Synchrotron and Synchrocyclotron Radiations; Osmium Dioxide (OsO2) and Osmium Tetroxide (OsO4) Nano Capsules; Delivery; DNA/RNA; Cancer Cells https://www.raftpubs.com/ijho-hematology-and-oncology/articles/ijho_raft1014.php

Currently, an ultrastructural analysis of cardiovascular tissues is significantly complicated. Routine histopathological examinations and immunohistochemical staining suffer from a relatively low resolution of light microscopy, whereas the fluorescence imaging of plaques and bioprosthetic heart valves yields considerable background noise from the convoluted extracellular matrix that often results in a low signal-to-noise ratio. Besides, the sectioning of calcified or stent-expanded blood vessels or mineralised heart valves leads to a critical loss of their integrity, demanding other methods to be developed. Here, we designed a conceptually novel approach that combines conventional formalin fixation, sequential incubation in heavy metal solutions (osmium tetroxide, uranyl acetate or lanthanides, and lead citrate), and the embedding of the whole specimen into epoxy resin to retain its integrity while accessing the region of interest by grinding and polishing. Upon carbon sputtering, the sample is visualised by means of backscattered scanning electron microscopy. The technique fully preserves calcified and stent-expanded tissues, permits a detailed analysis of vascular and valvular composition and architecture, enables discrimination between multiple cell types (including endothelial cells, vascular smooth muscle cells, fibroblasts, adipocytes, mast cells, foam cells, foreign-body giant cells, canonical macrophages, neutrophils, and lymphocytes) and microvascular identities (arterioles, venules, and capillaries), and gives a technical possibility for quantitating the number, area, and density of the blood vessels. Hence, we suggest that our approach is capable of providing a pathophysiological insight into cardiovascular disease development. The protocol does not require specific expertise and can be employed in virtually any laboratory that has a scanning electron microscope.

Electron microscopy of biological tissue has recently seen an unprecedented increase in imaging throughput moving the ultrastructural analysis of large tissue blocks such as whole brains into the realm of the feasible. However, homogeneous, high quality electron microscopy staining of large biological samples is still a major challenge. To date, assessing the staining quality in electron microscopy requires running a sample through the entire staining protocol end-to-end, which can take weeks or even months for large samples, rendering protocol optimization for such samples to be inefficient.Here we present an in situ time-lapsed X-ray assisted staining procedure that opens the “black box” of electron microscopy staining and allows observation of individual staining steps in real time. Using this novel method we measured the accumulation of heavy metals in large tissue samples immersed in different staining solutions. We show that the measured accumulation of osmium in fixed tissue obeys empirically a quadratic dependence between the incubation time and sample size. We found that potassium ferrocyanide, a classic reducing agent for osmium tetroxide, clears the tissue after osmium staining and that the tissue expands in osmium tetroxide solution, but shrinks in reduced osmium solution.X-ray assisted staining gave access to the in situ staining kinetics and allowed us to develop a diffusion-reaction-advection model that accurately simulates the measured accumulation of osmium in tissue. These are first steps towards in silico staining experiments and simulation-guided optimization of staining protocols for large samples. Hence, X-ray assisted staining will be a useful tool for the development of reliable staining procedures for large samples such as entire brains of mice, monkeys or humans.

We examined the functional morphology of loach Misgurnus anguillicaudatus skin by using synchrotron X-ray micro-computed tomography (SR-μCT) and high-contrast staining using osmium tetroxide or phosphotungstic acid (PTA), which enhances the image contrast of soft tissues. The captured high-spatial resolution images revealed that the surface ornamentations were stuck in the basement membrane of the loach scales. The ornamentations consisting of grooves (radii) and ridges (circuli) that can move freely and bend flexibly. The cross-sectional lateral microstructures of flat, concave and convex loach skins were observed from a live image of loach skin obtained through dark-field optical coherence tomography (OCT) imaging. The thickness of loach skin was changed with varying empty space between the mucous-cell layer and the scales by bending motion of loach. In addition, through direct measurement of drag reduction of loach skin, the mucous layer was found to have a strong influence on the reduction of skin friction. The present results enhance the understanding of the functional morphologies of mucous layer of loach to secrete mucus for skin friction reduction.

Super-resolution correlative light and electron microscopy (SR-CLEM) is a powerful approach for imaging specific molecules at the nanoscale in the context of the cellular ultrastructure. Epon epoxy resin embedding offers advantages for SR-CLEM, including ultrastructural preservation and high quality sectioning. However, Epon embedding eliminates fluorescence from most fluorescent proteins. We describe a photocontrollable fluorescent protein, mEosEM, that can survive Epon embedding after osmium tetroxide (OsO4) treatment for improved SR-CLEM.

Protein and solid-state nanopores are used for DNA/RNA sequencing as well as for single molecule analysis. We proposed that selective labeling/tagging may improve base-to-base resolution of nucleic acids via nanopores. We have explored one specific tag, the Osmium tetroxide 2,2′-bipyridine (OsBp), which conjugates to pyrimidines and leaves purines intact. Earlier reports using OsBp-tagged oligodeoxyribonucleotides demonstrated proof-of-principle during unassisted voltage-driven translocation via either alpha-Hemolysin or a solid-state nanopore. Here we extend this work to RNA oligos and a third nanopore by employing the MinION, a commercially available device from Oxford Nanopore Technologies (ONT). Conductance measurements demonstrate that the MinION visibly discriminates oligoriboadenylates with sequence A15PyA15, where Py is an OsBp-tagged pyrimidine. Such resolution rivals traditional chromatography, suggesting that nanopore devices could be exploited for the characterization of RNA oligos and microRNAs enhanced by selective labeling. The data also reveal marked discrimination between a single pyrimidine and two consecutive pyrimidines in OsBp-tagged AnPyAn and AnPyPyAn. This observation leads to the conjecture that the MinION/OsBp platform senses a 2-nucleotide sequence, in contrast to the reported 5-nucleotide sequence with native nucleic acids. Such improvement in sensing, enabled by the presence of OsBp, may enhance base-calling accuracy in enzyme-assisted DNA/RNA sequencing.

Background: The ability of women to reproduce is well known to decline with age. Advanced maternal age is related to reduce fertility and adverse pregnancy outcomes. There is evident decline in human fertility with age due to several histological changes occur with progressive age. Objective: The research was intended to know that some cellular modifications happen during the reproductive and post-menopause phases in human endometrial cells. Materials and methods: 30 womb samples each from reproductive and postmenopausal women were collected from unembalmed human cadavers. Before being taken to electron microscopy, samples were resolved in glutaraldehyde solution and osmium tetroxide as fixative. Small sizes of endometrial specimens were drawn into a unique fixative (i.e., 5% glutaraldehyde in a buffer of 0.1μphosphate (PH 7.4), then washed three times in a buffer solution. The moved to prepare thin sections for electron microscopy. Samples were integrated at 60co for two days in Arledit –Rezen capsule. Thin parts for E.M. were then ready study Ultra-structural cell of endometrium Results: Many differences were clear and evident when comparison was made between reproductive and postmenopause stages of endometrial cell ultrastructurally. The structural changes involved shape, density, cell organelles aggregation in general, and were assigned to age, as well as degeneration, deposition, and irregularity. Conclusion: Present work results indicated that, increase the amount of cell organelles in uterine cells of young women, while the old ages characterize by less number of organelles and degenerated.

Organic matter (OM) in surface soil is largely present within porous mineral-dominant clusters called aggregates. Recent studies have shown the localization of OM within large macroaggregate structure based on synchrotron X-ray micro-computed tomography (μCT) coupled with a vapor-phase, osmium (Os)-staining pretreatment. Here we developed a new approach to identify OM locations within submillimeter-sized aggregates at higher spatial resolution and assessed its applicability using a well-characterized surface volcanic soil, an allophanic Andisol, under no-tillage with leaf compost addition. Water-stable aggregates (500–800 μm in diameter) were embedded in agarose, chemically fixed, and repeatedly stained by osmium tetroxide and thiocarbohydrazide, followed by gradual dehydration with ethanol and resin fixation. Scanning electron microscopy and μCT observation showed no signs of physical alteration during sample preparation. Energy-dispersive X-ray spectroscopy analysis of the microtome-cut surface of the aggregate identified plant detritus highly enriched in Os and much smaller amorphous OM (

Leafy liverwort is one of the most abundant and diverse plants in Indonesia. Their high variation and beneficial secondary metabolites contained in the oil bodies have attracted researchers' attention. The ultrastructural analysis of leafy liverworts is important as a means of species identification and also for further exploration of their oil bodies. However, the optimization of the preparation steps for observing leafy liverworts by SEM is necessary to avoid sample destruction. Fixation and drying play important roles in maintaining a sample's structure as close to its natural state as possible. Thus, in this study, we evaluated the effect of 4% Osmium tetroxide (OsO4 ) and drying on leafy liverworts ultrastructure. Microlejeunea, Acrolejeunea, and Frullania were fixed with 2.5% glutaraldehyde. Some samples were then post-fixed with 4% OsO4 , while the rest were directly dehydrated with an ethanol series and then subjected to different drying methods, i.e. air drying, freeze drying, and drying with hexamethyldisilazane (HMDS). According to the data obtained, post-fixation with 4% OsO4 could better maintain the integrity of the samples and enhance the contrast of leafy liverwort SEM images. In addition, samples dried with HMDS showed more detailed structures compared to those that were air dried. Different ultrastructure were found among the different leafy liverworts observed by SEM. Our data suggested the advantages of SEM in providing ultrastructure information on leafy liverworts as well as the optimum conditions to observe them with less deformation. OsO4 post-fixation could enhance the contrast of leafy liverwort SEM images and maintain the structure of the samples. Drying with HMDS provided a convenient way for rapid SEM preparation with less structural distortion.

Staining compounds containing heavy elements (electron dyes) can facilitate the visualization of DNA and related biomolecules by using TEM. However, research into the synthesis and utilization of alternative electron dyes has been limited. Here, we report the synthesis of a novel DNA intercalator molecule, bis‐acridine uranyl (BAU). NMR spectroscopy and MS confirmed the validity of the synthetic strategy and gel electrophoresis verified the binding of BAU to DNA. For TEM imaging of DNA, two‐dimensional DNA origami nanostructures were used as a robust microscopy test object. By using scanning transmission electron microscopy (STEM) imaging, which is favored over conventional wide‐field TEM for improved contrast, and therefore, quantitative image analysis, it is found that the synthesized BAU intercalator can render DNA visible, even at the single‐molecule scale. For comparison, other staining compounds with a purported affinity towards DNA, such as dichloroplatinum, cisplatin, osmium tetroxide, and uranyl acetate, have been evaluated. The STEM contrast is discussed in terms of the DNA–dye association constants, number of dye molecules bound per base pair, and the electron‐scattering capacity of the metal‐containing ligands. These findings pave the way for the future development of electron dyes with specific DNA‐binding motifs for high‐resolution TEM imaging.

Receptor occupancy, the ratio between amount of drug bound and amount of total receptor on single cells, is a biomarker for treatment response to therapeutic monoclonal antibodies. Receptor occupancy is traditionally measured by flow cytometry. However, spectral overlap in flow cytometry limits the number of markers that can be measured simultaneously. This restricts receptor occupancy assays to the analysis of major cell types, although rare cell populations are of potential therapeutic relevance. We therefore developed a receptor occupancy assay suitable for mass cytometry. Measuring more markers than currently available in flow cytometry allows simultaneous receptor occupancy assessment and high‐parameter immune phenotyping in whole blood, which should yield new insights into disease activity and therapeutic effects. However, varying sensitivity across the mass cytometer detection range may lead to misinterpretation of the receptor occupancy when drug and receptor are detected in different channels. In this report, we describe a method for optimization of mass cytometry receptor occupancy measurements by using antibody‐binding quantum simply cellular (QSC) beads for standardization across channels with different sensitivities. We evaluated the method in a mass cytometry‐based receptor occupancy assay for natalizumab, a therapeutic antibody used in multiple sclerosis treatment that binds to α4‐integrin, which is expressed on leukocyte cell surfaces. Peripheral blood leukocytes from a treated patient were stained with a panel containing metal‐conjugated antibodies for detection of natalizumab and α4‐integrin. QSC beads with known antibody binding capacity were stained with the same metal‐conjugated antibodies and were used to standardize the signal intensity in the leukocyte sample before calculating receptor occupancy. We found that QSC bead standardization across channels corrected for sensitivity differences for detection of drug and receptor and generated more accurate results than observed without standardization. © 2019 The Authors. Cytometry Part A published by Wiley Periodicals, Inc. on behalf of International Society for Advancement of Cytometry.

O emprego do microscópio eletrônico de transmissão (MET) é bastante difundido no estudo de materiais biológicos, pois ele permite definição de imagens intracelulares, permitindo estudos de morfologia celular e de aspectos gerais das organelas. As imagens são produzidas por meio da interação inicial de um feixe de elétrons com a amostra, que é mantida sob condições de alto vácuo. Tanto o ambiente de vácuo como a própria irradiação dos elétrons durante a observação, representam condições adversar para a amostra, especialmente no caso de materiais orgânicos ou biológicos, que são por natureza hidratados, frágeis e elétricamente isolantes. Considerando que existem várias técnicas de preparo para MET, mas pouca descrição detalhada destas técnicas na literatura, principalmente para o preparo de raízes de plântulas, assim, esse trabalho teve como objetivo aplicar e adaptar essas técnicas para o estudo de boa qualidade de raízes de plântulas. As amostras primeiramente foram lavadas em tampão fosfato salina, passando pela fixação primária com glutaraldeído, depois pós-fixação com tetróxido de Ósmio, onde posteriormente foram desidratadas com acetona e infiltradas com resina Epon, finalizando com a polimerização, ultramicrotomia e contrastação da amostra. Contudo, essa descrição detalhada da metodologia aplicada para raiz de plântulas, pode ser utilizada com segurança e eficácia por outras pessoas, pois quase não existem descrições adaptadas de metodologia de MET na literatura, principalmente para raiz de plântulas.

Background: Glioblastoma (GB) is the most commonly diagnosed brain tumor. Its management involves adjuvant therapies, such as radiation. The cause of high probability of GB local relapse is its radioresistance related to hypoxia arising from abnormal blood-brain barrier permeability in GB vessels and in the peritumoral zone (PZ). Aim: To study pathophysiology of hypoxia in the residual GB based on the abnormalities of the morphological elements of the capillary walls building up the blood-brain barrier in GB and PZ capillaries. Materials and methods: Samples for morphological evaluation were taken during surgery for GB in 5 patients. The samples were prepared for transmission electron microscopy according to the standard technique with fixation in 2% glutaraldehyde in phosphate buffer, post-fixation with osmium tetroxide, embedding in the epon-araldite mixture, and contrast staining of ultrathin sections with uranylacetate and lead citrate. Abnormalities of the capillary cells (mitochondrial vacuolization and vacuolization of endoplasmic reticulum in endothelial cells, pericytes and astrocytes), as well as of the acellular element of the capillary wall, i.e. basement membrane, were assessed in two groups of capillaries – those of GB (n = 38) and those of PZ (n = 32). Results: Abnormalities characteristic for apoptosis and oncosis were found in the cells of the GB and PZ capillaries of the blood-brain barrier, such as endothelial cells and pericytes. However, in the GB capillaries these abnormalities were signifcantly more frequent (р < 0.001). Only half (52.6%) of the GB capillaries had an edematous pericapillary astrocyte layer. In all other capillaries, astrocyte sprouts either were visualized as separate morphological elements (13.2%) or were not visualized at all (34.2%). All PZ capillaries had the astrocyte layer, being edematous in 68.8% of the capillaries and totally edematous only in 25%. Thickened basement membrane was found in the vast majority (89.5%) of the GB capillaries and only in 25% of the PZ capillaries (р < 0.001). Conclusion: Findings of abnormal cell elements in the GB capillaries leading to peritumoral edema and consequent hypoxia are highly likely to be the cause of the remnant GB radioresistance.

SUMMARY Leaves of Lolium multiflorum Lam. and Zea mays L. of different ages were prepared for TEM by a number of cytochemical methods. After post-fixation in potassium ferricyanide with osmium tetroxide the peripheral reticulum in both mesophyll and bundle sheath chloroplasts of maize stain very clearly. Post-fixation with uranyl acetate, copper and lead salts also stains the chloroplast envelope rather than the internal thylakoid system. Differences between the mesophyll and bundle sheath chloroplasts of maize and between those of ryegrass are revealed after post-fixation in zinc iodide with osmium tetroxide. After post-fixation in potassium iodide with osmium tetroxide the loculi stain less intensely than in zinc iodide. Malachite green added to glutaraldehyde at pH 7 0 enhances membrane staining in general and reveals large lipid drops in the stroma. At pH below 6 0 only the 'A' space is stained. The 'A' space and the loculus are stained when ethidium bromide is added to glutaraldehyde. The different reactions of the chloroplast membranes probably reflect differences in chemical composition.

Immunogold labeling allows localization of proteins at the electron microscopy (EM) level of resolution, and quantification of signals. The present paper summarizes methodological issues and experiences gained from studies on the distribution of synaptic and other neuron-specific proteins in cell cultures and brain tissues via a pre-embedding method. An optimal protocol includes careful determination of a fixation condition for any particular antibody, a well-planned tissue processing procedure, and a strict evaluation of the credibility of the labeling. Here, tips and caveats on different steps of the sample preparation protocol are illustrated with examples. A good starting condition for EM-compatible fixation and permeabilization is 4% paraformaldehyde in PBS for 30 min at room temperature, followed by 30 min incubation with 0.1% saponin. An optimal condition can then be readjusted for each particular antibody. Each lot of the secondary antibody (conjugated with a 1.4 nm small gold particle) needs to be evaluated against known standards for labeling efficiency. Silver enhancement is required to make the small gold visible, and quality of the silver-enhanced signals can be affected by subsequent steps of osmium tetroxide treatment, uranyl acetate en bloc staining, and by detergent or ethanol used to clean the diamond knife for cutting thin sections. Most importantly, verification of signals requires understanding of the protein of interest in order to validate for correct localization of antibodies at expected epitopes on particular organelles, and quantification of signals needs to take into consideration the penetration gradient of reagents and clumping of secondary antibodies. Supplementary Information The online version contains supplementary material available at 10.1186/s13041-021-00799-2.

Parasitic infections can be challenging to study, because light and electron microscopy are often limited in visualising complex and inaccessible attachment sites. Exemplifying this, Trichuris spp. inhabits a tunnel of epithelial cells within the host caecum and colon. A significant global burden of this infection persists partly because available anthelminthics lack efficacy, although the mechanisms underlying this remain unknown. Consequently, there is a need to pioneer new approaches to better characterize the parasite niche within the host and investigate how variation in its morphology and integrity may contribute to resistance to therapeutic intervention. To address these aims, we exploited 3D X-ray micro-computed tomography (microCT) to image the mouse whipworm T. muris in caeca of wild-type C57BL/6 and SCID mice ex vivo. Using osmium tetroxide staining to effectively enhance contrast of worms, we found that a subset exhibited preferential positioning towards the bases of the intestinal crypts. Moreover, in one rare event, we demonstrate whipworm traversal of the lamina propria. This morphological variability contradicts widely accepted conclusions from conventional microscopy of the parasite niche, showing Trichuris in close contact with the host proliferative and immune compartments that may facilitate immunomodulation. Furthermore, by using a skeletonization-based approach we demonstrate considerable variation in tunnel length and integrity which may represent an indicator of tunnel “health”. The qualitative and quantitative observations provide a new morphological point of reference for future in vitro study of Trichuris-host interactions and highlight the potential of microCT to more accurately characterise enigmatic host-parasite interactions.Author SummaryParasites are often difficult to observe once established within host tissues, presenting a barrier to biological understanding and therapeutic innovation. Whipworms (Trichuris spp.) affect 500 million people worldwide, causing significant disability, and appear partially resistant to widely used “deworming” drugs. However, the inaccessibility of worms within the cells of the host intestine makes them highly challenging to image and study. By investigating Trichuris attachment sites in 3D, using X-ray micro-computed tomography, we found that the niche is highly variable in size and, contrary to reports in all previous studies, can also penetrate different layers of intestinal tissue. By showing that worms are positioned much closer to host immune cells that previously appreciated, we provide a morphological reference point for future studies on how Trichuris effectively avoids clearance by the host. The non-invasive imaging approach used represents an excellent opportunity to clarify the lifecycles of other difficult-to-study parasites.

Simple Summary Bacterial biofilms cause infections that are often resistant to antibiotic treatments. Research about the formation and elimination of biofilms cannot be undertaken without detailed imaging techniques. In this review, traditional and cutting-edge microscopy methods to study biofilm structure, ultrastructure, and 3-D architecture, with particular emphasis on conventional scanning electron microscopy and variable pressure scanning electron microscopy, are addressed, with the respective advantages and disadvantages. When ultrastructural characterization of biofilm matrix and its embedded bacterial cells is needed, as in studies on the effects of drug treatments on biofilm, scanning electron microscopy with customized protocols such as the osmium tetroxide (OsO4), ruthenium red (RR), tannic acid (TA), and ionic liquid (IL) must be preferred over other methods for the following: unparalleled image quality, magnification and resolution, minimal sample loss, and actual sample structure preservation. The first step to make a morphological assessment of the effect of the various pharmacological treatments on clinical biofilms is the production of images that faithfully reflect the structure of the sample. The extraction of quantitative parameters from images, possible using specific software, will allow for the scanning electron microscopy morphological evaluation to no longer be considered as an accessory technique, but a quantitative method to all effects. Abstract Several imaging methodologies have been used in biofilm studies, contributing to deepening the knowledge on their structure. This review illustrates the most widely used microscopy techniques in biofilm investigations, focusing on traditional and innovative scanning electron microscopy techniques such as scanning electron microscopy (SEM), variable pressure SEM (VP-SEM), environmental SEM (ESEM), and the more recent ambiental SEM (ASEM), ending with the cutting edge Cryo-SEM and focused ion beam SEM (FIB SEM), highlighting the pros and cons of several methods with particular emphasis on conventional SEM and VP-SEM. As each technique has its own advantages and disadvantages, the choice of the most appropriate method must be done carefully, based on the specific aim of the study. The evaluation of the drug effects on biofilm requires imaging methods that show the most detailed ultrastructural features of the biofilm. In this kind of research, the use of scanning electron microscopy with customized protocols such as osmium tetroxide (OsO4), ruthenium red (RR), tannic acid (TA) staining, and ionic liquid (IL) treatment is unrivalled for its image quality, magnification, resolution, minimal sample loss, and actual sample structure preservation. The combined use of innovative SEM protocols and 3-D image analysis software will allow for quantitative data from SEM images to be extracted; in this way, data from images of samples that have undergone different antibiofilm treatments can be compared.

Imaging the visual systems of bumblebees and other pollinating insects may increase understanding of their dependence on specific habitats and how they will be affected by climate change. Current high-resolution imaging methods are either limited to two dimensions (light- and electron microscopy) or have limited access (synchrotron radiation x-ray tomography). For x-ray imaging, heavy metal stains are often used to increase contrast. Here, we present micron-resolution imaging of compound eyes of buff-tailed bumblebees (Bombus terrestris) using a table-top x-ray nanotomography (nano-CT) system. By propagation-based phase-contrast imaging, the use of stains was avoided and the microanatomy could more accurately be reconstructed than in samples stained with phosphotungstic acid or osmium tetroxide. The findings in the nano-CT images of the compound eye were confirmed by comparisons with light- and transmission electron microscopy of the same sample and finally, comparisons to synchrotron radiation tomography as well as to a commercial micro-CT system were done. peerReviewed

Nanopores can serve as single molecule sensors. We exploited the MinION, a portable nanopore device from Oxford Nanopore Technologies (ONT), and repurposed it to detect any DNA/RNA oligo (target) in a complex mixture by conducting voltage-driven ion-channel measurements. The detection and quantitation of the target is enabled by the use of a unique complementary probe. Using a validated labeling technology, probes are tagged with a bulky Osmium tag (Osmium tetroxide 2,2’-bipyridine), in a way that preserves strong hybridization between probe and target. Intact oligos traverse the MinION’s nanopore relatively quickly compared to the device’s acquisition rate, and exhibit count of events comparable to the baseline. Counts are reported by a publicly available software,OsBp_detect. Due to the presence of the bulky Osmium tag, probes traverse more slowly, produce multiple counts over the baseline, and are even detected at single digit attomole (amole) range. In the presence of the target the probe is “silenced”. Silencing is attributed to a 1:1 double stranded (ds) complex that doesn’t fit and can’t traverse this nanopore. This ready-to-use platform can be tailored as a diagnostic test to meet the requirements for point-of-care cell-free tumor DNA (ctDNA) and microRNA (miRNA) detection and quantitation in body fluids.