Standard Microscopy Techniques Research Articles

High prevalence of intestinal parasite infestations among stunted and control children aged 2 to 5 years old in two neighborhoods of Antananarivo, Madagascar.

This study aimed to compare the prevalence of intestinal parasite infestations (IPIs) in stunted children, compared to control children, in Ankasina and Andranomanalina Isotry (two disadvantaged neighborhoods of Antananarivo, Madagascar), to characterize associated risk factors and to compare IPI detection by real-time PCR and standard microscopy techniques. Fecal samples were collected from a total of 410 children (171 stunted and 239 control) aged 2-5 years. A single stool sample per subject was examined by simple merthiolate-iodine-formaldehyde (MIF), Kato-Katz smear and real-time PCR techniques. A total of 96.3% of the children were infested with at least one intestinal parasite. The most prevalent parasites were Giardia intestinalis (79.5%), Ascaris lumbricoides (68.3%) and Trichuris trichiura (68.0%). For all parasites studied, real-time PCR showed higher detection rates compared to microscopy (G. intestinalis [77.6% (n = 318) versus 20.9% (n = 86)], Entamoeba histolytica [15.8% (n = 65) versus 1.9% (n = 8)] and A. lumbricoides [64.1% (n = 263) versus 50.7% (n = 208)]). Among the different variables assessed in the study, age of 4 to 5 years (AOR = 4.61; 95% CI, (1.35-15.77)) and primary and secondary educational level of the mother (AOR = 12.59; 95% CI, (2.76-57.47); AOR = 9.17; 95% CI, (2.12-39.71), respectively) were significantly associated with IPIs. Children drinking untreated water was associated with infestation with G. intestinalis (AOR = 1.85; 95% CI, (1.1-3.09)) and E. histolytica (AOR = 1.9; 95% CI, (1.07-3.38)). E. histolytica was also associated with moderately stunted children (AOR = 0.37; 95% CI, 0.2-0.71). Similarly, children aged between 4 and 5 years (AOR = 3.2; 95% CI (2.04-5.01)) and living on noncemented soil types (AOR = 1.85; 95% CI, (1.18-2.09)) were associated with T. trichiura infestation. The prevalence of IPIs is substantial in the studied areas in both stunted and control children, despite the large-scale drug administration of antiparasitic drugs in the country. This high prevalence of IPIs warrants further investigation. Improved health education, environmental sanitation and quality of water sources should be provided.

Analysing errors in single-molecule localisation microscopy.

In single molecule localisation microscopy (SMLM) a super-resolution image of the distribution of fluorophores in the sample is built up from the localised positions of many individual molecules. It has become widely used due to its experimental simplicity and the high resolution that can be achieved. However, the factors which limit resolution in a reconstructed image, and the artefacts which can be present, are completely different to those present in standard fluorescent microscopy techniques. Artefacts may be difficult for users to identify, particularly as they can cause images to appear falsely sharp, an effect called artificial sharpening. Here we discuss the different sources of error and bias in SMLM, and the methods available for avoiding or detecting them.

Significant lipid and neutrophil accumulation and active inflammasome in high BMI tumor regions of human pancreatic ductal adenocarcinoma.

438 Background: Obesity is an established risk factor for cancer and cancer-related mortality. Adipocytes may act as a “damage” signal resulting in the accumulation of innate immune cells, fueling an inflammatory micro-environment. Among the innate immune cells, tumor-associated neutrophils (TANs) are confirmed to accumulate inside the tumor. As obesity is a significant risk factor for a poorer prognosis in pancreatic ductal adenocarcinoma (PDAC), we hypothesize that obesity-driven adipose fuels the progression of PDAC in a TAN and inflammasome-facilitated manner. This may happen through several mechanisms, including genomic instability of aggressive PDAC clonal populations. Methods: Tissue from resected tumors of PDAC patients (n = 44) with a body-mass index (BMI) > 27 (obese [n = 21]) and BMI < 22 (normal [n = 23]) were incubated with anti-human CD66b antibodies and detected using standard immunofluorescent microscopy techniques. Images were acquired in a Zeiss Axioplan microscope workstation and analyzed by ZEN and Metamorph software. Results: We identified the presence of adipocytes in all tissue sections and CD66b+ neutrophils in all tissue sections of normal BMI patients and in 81% of high BMI patients. There is a significantly greater density of adipocytes in the tumor environment when compared to adjacent normal areas, suggesting that these cells are acting as a damage signal. Our novel data also shows that high BMI results in a significantly higher neutrophil count in tumor specific tissue when compared to patients with a low BMI. These data suggest an association between BMI and inflammasome accumulation in the tumor environment. Conclusions: Our data uniquely shows that CD66b+ neutrophils tend to accumulate inside PDAC in high BMI patients and this is associated with intra-tumoral active inflammasomes. The higher concentrations of these inflammasomes in higher BMI patients may be of mechanistic relevance in understanding how inflammation induces progression of PDAC. A larger cohort of tissues from PDAC obtained from low and high BMI individuals will be needed to test our hypothesis and to begin to decipher the role of obesity on inflammation and PDAC progression.

Porphyrin-Loaded Lignin Nanoparticles Against Bacteria: A Photodynamic Antimicrobial Chemotherapy Application.

The need for alternative strategies to fight bacteria is evident from the emergence of antimicrobial resistance. To that respect, photodynamic antimicrobial chemotherapy steadily rises in bacterial eradication by using light, a photosensitizer and oxygen, which generates reactive oxygen species that may kill bacteria. Herein, we report the encapsulation of 5,10,15,20-tetrakis(4-hydroxyphenyl)-21H,23H-porphyrin into acetylated lignin water-dispersible nanoparticles (THPP@AcLi), with characterization of those systems by standard spectroscopic and microscopic techniques. We observed that THPP@AcLi retained porphyrin’s photophysical/photochemical properties, including singlet oxygen generation and fluorescence. Besides, the nanoparticles demonstrated enhanced stability on storage and light bleaching. THPP@AcLi were evaluated as photosensitizers against two Gram-negative bacteria, Escherichia coli and Pseudomonas aeruginosa, and against three Gram-positive bacteria, Staphylococcus aureus, Staphylococcus epidermidis, and Enterococcus faecalis. THPP@AcLi were able to diminish Gram-positive bacterial survival to 0.1% when exposed to low white LED light doses (4.16 J/cm2), requiring concentrations below 5 μM. Nevertheless, the obtained nanoparticles were unable to diminish the survival of Gram-negative bacteria. Through transmission electron microscopy observations, we could demonstrate that nanoparticles did not penetrate inside the bacterial cell, exerting their destructive effect on the bacterial wall; also, a high affinity between acetylated lignin nanoparticles and bacteria was observed, leading to bacterial flocculation. Altogether, these findings allow to establish a photodynamic antimicrobial chemotherapy alternative that can be used effectively against Gram-positive topic infections using the widely available natural polymeric lignin as a drug carrier. Further research, aimed to inhibit the growth and survival of Gram-negative bacteria, is likely to enhance the wideness of acetylated lignin nanoparticle applications.

Characterization of Microstructure of Crept Samples of Dissimilar Weld Joint Using Standard and Advanced Electron Microscopy Techniques

Conventional long-term creep test (CCT) to the rupture and so called accelerated creep test (ACT) of the dissimilar weld joint made of FB2 and F martensitic steels and of the base materials were carried out at temperatures ranging from 550 °C to 650 °C in the stress range from 70 to 220 MPa. Assessment of microstructure development and changes of hardness was correlated with the creep strength. During creep at temperatures above 575 °C Laves phase precipitated in all parts of the weld joint and especially in the heat affected zones. Coarse Laves phase particles and their clusters with chromium carbides served as nucleation centers for cavities. As the fine grained heat affected zone of F steel was the softest part of the weld joint, many cavities originated and cause failure of samples. The aim of this paper is to compare results and possibilities of the “standard” methods and advanced scanning electron microscopy performed by instrument equipped with a concentric backscatter electron detector (CBS). Filtering of the signal enables improving and/or diminishing of selected type of contrast caused by various types of particles of secondary phases. The images were used as an input data for image analysis and developments of microstructures during CCT and ACT were compared. Results have shown that specimens after ACT contains significantly lower content of the Laves phase.

Antisickling potential of compounds derived from Detarium microcarpum (Fabaceae): in vitro and in silico studies

Detarium microcarpum is a legume tree of tropical Africa, widely known for its ethno-medicinal potentials. Previous studies have reported its rich contents of phytochemicals which could be linked to the bioactive principle of the plant. The in vitro antisickling properties of D. microcarpum stem bark was evaluated using blood samples obtained from thirty-five confirmed sickle cell disease patients using standard microscopic techniques. The research outcome showed that D. microcarpum extract inhibited sickling of red blood cells with a laudable mean difference compared to p-hydrozybenzoic acid (reference antisickling drug) which is a pure compound. To further expounds it’s mechanism of action, six compounds previously isolated from D. microcarpum stem bark and fruits was docked into the active sites of deoxy-hemoglobin (PDB ID: IGZX) and 2, 3-bisphosphoglycerate mutase (PDB ID: 1T8P) using Autodock Vina algorithm. Results from the in silico studies showed that oxokolavenic acid, 5α, 8α -2-oxokalavenic acid and Copalic acid exhibited the most favorable ligand–protein molecular interaction with deoxy-hemoglobin and 2,3-bisphosphoglycerate mutase when compared with the reference antisickling drug, hydroxyurea. The interaction of these compounds with deoxy-hemoglobin could alter hemoglobin conformation, favoring the relaxed state, thereby delaying/inhibiting hemoglobin polymerization and sickling. Their interactions with 2, 3-bisphosphoglycerate mutase could inhibit 2, 3-bisphosphoglycerate synthesis, thus delaying enhanced delivery of oxygen to tissues which is twice the case seen in sickle cell anemia. This clearly shows the possible mechanism of action of D. microcarpum and further substantiates the antisickling potential of these compounds derived from D. microcarpum leaves and fruits.

Root cause analysis of failure of bolts in the low pressure section of a gas turbine in an oil and gas production plant

This research establishes the cause of a severe failure in bolts in the low pressure (LP) section of a gas turbine in an oil and gas production plant. The failure in bolts was reported together with massive failures of turbine blades in the second stage in the hot section of the turbine. The failure was categorized as an unexpected premature failure, given that it was reported to take place after 20 k of service and that the expected service life for this turbine is beyond 100 k. This research had a two-fold purpose; i) to analyse the cause of failure in both components (failed bolts and blades) and ii) to come up with a scenario for the chain of events. Standard microscopic examination techniques (optical metallography and electron microscopy) were used to correlate microstructure of failed components with possible failure mechanisms. Results showed a clear corrosion-fatigue-induced failure in blades. Hardly is there any evidence of fatigue failure in bolts. Bolts appeared to have experienced an excessive load and have consequently been heavily deformed and broken. The failure scenario was proposed, based on the service history, observations, and microstructural examinations.

Graphene derivative coated QCM-based gas sensor for volatile organic compound (VOC) detection at room temperature

<span>Volatile organic compounds (VOCs) affect our daily life through their emission from very common sources such as plants, building materials, paints, pesticides, and fossil fuel burning. The detection of VOCs at room temperature is a prime requirement. The graphene-based gas sensor has the potential to detect these VOC gases due to its attractive features such as high mobility and large surface area. In this work, a graphene-derivative is prepared as a sensing material in order to detect acetone. The thin film of graphene-derivative is prepared by a drop-cast method on a quartz crystal microbalance (QCM) sensor followed by drying in the room environment conditions. The prepared graphene-derivative and thin films are characterized structurally and morphologically by standard microscopic techniques such as FESEM, EDX, and Raman spectroscopy. The electrical parameters such as mobility and resistivity are measured using Hall-effect measurements at room temperature. The response and recovery time of the graphene-derivative based 10 MHz QCM sensor are found to be 23 s and 20 s, respectively. This highly sensitive graphene-based gas sensor with good reversibility can be employed for human health and environment safety applications. </span>

Structural and Functional Characterization of the Tongue and Digestive Tract of Psammophis sibilans (Squamata, Lamprophiidae): Adaptive Strategies for Foraging and Feeding Behaviors.

We describe the morphological adaptations of the tongue and gastrointestinal tract of the striped sand snake Psammophis sibilans and discuss their functional importance. Using standard histological, histochemical, and scanning electron microscopy techniques, we analyzed 11 adult snakes of both sexes. Our findings showed that the bifurcated non-papillate tongue exhibited chemoreceptive adaptions to squamate foraging behavior. The lingual apex tapered terminally with sensory spines, and the body of the tongue possesses a characteristic central odor-receptor chamber that might serve to trap and retain scent molecules. Furthermore, the intrinsic musculature showed interwoven and well-developed transverse, vertical and longitudinal muscle fibers that control contraction and retraction during probing and flicking. The esophagus displayed highly folded mucosa lined with columnar epithelium with goblet cells. In contrast, the stomach mucosa formed finger-like gastric rugae, encompassing tubular glands with dorsal gastric pits. The intestine is distinct from other vertebrates in lacking the crypts of Lieberkühn in the tunica mucosa and submucosa. The intestine mucosa is mostly arranged in interdigitating villi oriented perpendicular to the luminal surface. We extrapolated subtle variations for both acid and neutral mucopolysaccharides and glycoproteins localization as well as collagen fibers using histochemical analyses. The elaborate histo-morphological and functional adaptation of the tongue and digestive tract plays a pivotal role in foraging and feeding behavior.

Stabilization of phase-pure rhombohedral HfZrO4 in pulsed laser deposited thin films

Controlling the crystalline structure of Hafnium Zirconate and its epitaxial relationship to a semiconducting electrode has a high technological interest, as ferroelectric materials are key ingredients for emerging electronic devices. Using Pulsed Laser Deposition, a phase pure, ultra-thin film of HfZrO4 is grown epitaxially on a GaN (0001) / Si (111) template. Since standard microscopy techniques do not allow to determine with certitude the crystalline structure of the film due to the weak scattering of oxygen, differentiated differential phase contrast (DPC) Scanning Transmission Electron Microscopy is used to allow the direct imaging of oxygen columns in the film. Combined with X-Rays diffraction analysis, the polar nature and rhombohedral R3 symmetry of the film are demonstrated.

Toward a High-Resolution Reconstruction of 3D Nerve Fiber Architectures and Crossings in the Brain Using Light Scattering Measurements and Finite-Difference Time-Domain Simulations

In many laboratories, conventional bright-field transmission microscopes are available to study the structure and organization principles of fibrous tissue samples, but they usually provide only 2D information. To access the third (out-of-plane) dimension, more advanced techniques are employed. An example is 3D Polarized Light Imaging (3D-PLI), which measures the birefringence of histological brain sections to derive the spatial nerve fiber orientations. Here, we show how light scattering in transmission microscopy measurements can be leveraged to gain 3D structural information about fibrous tissue samples like brain tissue. For this purpose, we developed a simulation framework using finite-difference time-domain (FDTD) simulations and high performance computing, which can easily be adapted to other microscopy techniques and tissue types with comparable fibrous structures (e.g., muscle fibers, collagen, or artificial fibers). As conventional bright-field transmission microscopy provides usually only 2D information about tissue structures, a three-dimensional reconstruction of fibers across several sections is difficult. By combining our simulations with experimental studies, we show that the polarization-independent transmitted light intensity (transmittance) contains 3D information: We demonstrate in several experimental studies on brain sections from different species (rodent, monkey, human) that the transmittance decreases significantly (by more than 50%) with the increasing out-of-plane angle of the nerve fibers. Our FDTD simulations show that this decrease is mainly caused by polarization-independent light scattering in combination with the finite numerical aperture of the imaging system. This allows to use standard transmission microscopy techniques to obtain 3D information about the fiber inclination and to detect steep fibers, without need for additional measurements.

Detection of low-level humic acid in water using room temperature-synthesized copper (I) oxide colloids

Abstract

Pneumatic unidirectional cell stretching device for mechanobiological studies of cardiomyocytes

In this paper, we present a transparent mechanical stimulation device capable of uniaxial stimulation, which is compatible with standard bioanalytical methods used in cellular mechanobiology. We validate the functionality of the uniaxial stimulation system using human-induced pluripotent stem cells-derived cardiomyocytes (hiPSC-CMs). The pneumatically controlled device is fabricated from polydimethylsiloxane (PDMS) and provides uniaxial strain and superior optical performance compatible with standard inverted microscopy techniques used for bioanalytics (e.g., fluorescence microscopy and calcium imaging). Therefore, it allows for a continuous investigation of the cell state during stretching experiments. The paper introduces design and fabrication of the device, characterizes the mechanical performance of the device and demonstrates the compatibility with standard bioanalytical analysis tools. Imaging modalities, such as high-resolution live cell phase contrast imaging and video recordings, fluorescent imaging and calcium imaging are possible to perform in the device. Utilizing the different imaging modalities and proposed stretching device, we demonstrate the capability of the device for extensive further studies of hiPSC-CMs. We also demonstrate that sarcomere structures of hiPSC-CMs organize and orient perpendicular to uniaxial strain axis and thus express more maturated nature of cardiomyocytes.

Anisotropy of thermal conductivity in In2Se3 nanostructures

In this report, α-In2Se3 single-crystal nanobelts and nanowires were grown in the thermal chemical vapor deposition furnace. The growth direction of the nanobelts was identified by standard microscopy techniques and was along the in-plane direction, while that of the nanowire was along the c-axis. The temperature-dependent thermal conductivity of the nanostructures was measured by a suspended-pattern technique, and it was found to fall into two ranges of values between 300 and 400 K owing to the difference in growth orientation. The experimental evidence presented herein is the anisotropy of phonon transport of the layered α-In2Se3, and the effect of bonding strength on the thermal conductivity at the nanoscale. This study would be helpful to the physical understanding and future design of In2Se3–based thermoelectric materials.

Formation of the diverticular lumen that enables oocyte fertilization in katoikogenic scorpions, Heterometrus spinifer and Opistophthalmus boehmi (Scorpionidae).

The structure of diverticula of the female gonads was analyzed in two scorpions from the family Scorpionidae by means of standard microscopic techniques (light microscopy, histochemistry, transmission electron microscopy). In scorpions, the female gonad, termed the ovariuterus, participates in two consecutive processes: oogenesis and embryogenesis. In sexually reproducing scorpions, the ovariuterus is also involved in fertilization. Both scorpions under study reproduce sexually. They also represent the katoikogenic type of development, which means that oogenesis, fertilization, and embryogenesis take place in the diverticula, which are sac-like outpocketings of the ovariuterine tubules. Formation of a lumen in the diverticulum is indispensable for sperm entry to enable fertilization and subsequent embryogenesis. The aim of the study was to test our hypothesis that the diverticulum lumen forms due to the engagement of the centrally located stalk cells. In this report, we show that in two species of katoikogenic scorpions, at the final stages of oogenesis, the cytoplasm of the stalk cells contains secretory organelles. In the stages preceding fertilization, secretory activity of the stalk cells and fragmentation of their apical parts lead to formation of the diverticulum lumen by a process similar to "cord hollowing" that commonly occurs for lumen formation in other morphogenesis model systems.

Egg autofluorescence and options for detecting peanut agglutinin binding for the identification of Haemonchus contortus eggs in fecal samples

Quantifying eggs from Haemonchus and other trichostrongyle genera in sheep and goat fecal samples is important for evaluating control and treatment strategies for this family of nematodes with divergent pathologies, capabilities for anthelmintic resistance and environmental susceptibilities. Unfortunately, egg morphology among most of the genera do not differ enough to support the accurate identification of these genera with standard microscopic techniques. Several studies have identified specific lectins which bind selectively to sugars located on the egg surfaces for individual genera among the trichostrongyles. To detect lectins binding to these eggs, they must be directly or indirectly bound to fluorophores, and observed with an epi-fluorescence microscope. The binding of multiple lectins to isolated eggs from a fecal sample can be simultaneously detected if fluorophores are used whose excitation and emission spectra do not overlap, and this would enable the development of a fluorescence-based diagnostic test that identifies multiple trichostrongyle genera within each sample. The present study compared the usefulness of different, commercially available detection systems for use in detecting lectin binding to trichostrongyle eggs. Comparisons were made using the detection of PNA binding to H. contortus eggs with the goal of finding three systems with color spectra that do not overlap. These evaluations included both fluorophores directly conjugated to PNA in a one-step incubation protocol and a two-step incubation protocol involving biotinylated PNA and streptavidin conjugated to different fluorophores. Autofluorescence can affect the efficiency of any fluorescence-based detection system, and significant autofluorescence was observed among the unstained H. contortus eggs with the DAPI-type fluorescence filter, but it was significantly lower with the FITC-type filter and was virtually absent with the rhodamine-type filter. This study demonstrated that all the PNA detection methods tested with H. contortus eggs generated fluorescence intensities (FIs) that were significantly above the autofluorescence generated by the eggs among the three different fluorescence filters. Fluorescence intensities from PNA directly conjugated to either the FITC or rhodamine fluorophores were not different, but the lower autofluoresence in the rhodamine-type filter will enable this fluorophore to be detected more efficiently. Use of biotinylated PNA combined with streptavidin-conjugated to synthetic fluorophores (Alexa Fluor 405, 488 and 546) significantly increased FIs over that of the directly conjugated PNA, but there were no significant differences in FIs among these three biotin-avidin conjugation fluorophores. This biotin-avidin system required two incubation steps. Doubling the concentration of PNA also provided increased FI, at least for the biotin-avidin system. Adding an additional amplification step to the biotin-avidin system involving biotinylated anti-streptavidin followed by the streptavidin-Alexa Fluor complex also provided additional fluorescence.

Morpho-anatomy of the inflorescence of Musa × paradisiaca

Bananas and plantains are herbaceous monocotyledonous plants belonging to the genus Musa, Musaceae, which has a widespread distribution around the world. Various parts of banana plant are commonly used in traditional medicines. Several species of Musa are reported to possess anti-inflammatory, anti-hyperglycemic and antidiabetic properties. This work is aimed at studying the morphological and anatomical characteristics of the inflorescences of Musa×paradisiaca L., that could contribute to the characterization of these species cultivated in Brazil. Plant materials were collected and prepared in accordance with standard optical microscopy techniques. Morphological characterizations were conducted using morphological descriptors for inflorescences, including some descriptors from International Plant Genetic Resources Institute for Musa spp. Microscope slides were prepared using glycol-methacrylate and were stained in toluidine blue. Main features observed for M.×paradisiaca inflorescence were amphistomatic bracts with tetracytic stomata, fiber caps next to the phloem, adaxial and abaxial uniseriate epidermis, and papillose on the abaxial face. Outer tepals have multilayer epidermis and vascular bundles aligned next to the abaxial face. Free tepal has unilayeredepidermis. Anthers are tetrasporangiate and the locules are separated by the septum. Ovary is inferior and trilocular with external unilayered and internal epidermis. The main morpho-anatomical characteristics of inflorescence of Musa×paradisiaca are highlighted in this study, contributing to provide more information about the characterization of this species cultivated in Brazil.

The 3D imaging of mesenchymal stem cells on porous scaffolds using high-contrasted x-ray computed nanotomography.

This study presents an X-ray computed nanotomography (nano-CT) based, high-resolution imaging technique. Thanks to a voxel resolution of 540nm, this novel technique is suitable for observing the 3D morphology of soft biopolymeric scaffolds seeded with stem cells. A sample of highly porous collagen scaffold seeded with contrasted mesenchymal stem cells (MSC) was investigated by using lab-based nano-CT. The whole volume of the sample was analysed without its destruction. To evaluate the potential of nano-CT, a comparison measurement was done using a standard microscopy technique. Scanning electron microscopy (SEM) combined with energy dispersive X-ray analysis (EDX) established an extension and local accumulation of the contrasting agent - heavy metallic osmium tetroxide. The presented imaging technique is novel as it will help to understand better the behaviour of cells while interacting with three-dimensional biomaterials. This is crucial for both experimental and clinical tissue engineering applications in order to limit the risk of uncontrolled cell growth, and potentially tumour formation. LAY DESCRIPTION: Biomaterials play a crucial role in tissue engineering by serving as 3D scaffolds for cellular attachment, proliferation, and in growth ultimately leading to new tissue formation. Cell morphology and proliferation inside the 3D scaffold are necessary to know for assessing cell viability. However, these studies are usually negatively affected by the limitations of imaging techniques. We demonstrate that X-ray computed nanotomography (nano-CT), based on high-resolution imaging technique providing voxel resolution of 540nm, is asuitable method for observing the 3D morphology of soft biopolymeric scaffolds seeded with stem cells. A sample of highly porous collagen scaffold seeded with contrasted mesenchymal stem cells (MSC) was investigated by using a lab-based nano-CT. The whole volume of the sample was analysed without its destruction. To evaluate the potential of nano-CT, a comparison measurement was done using a standard microscopy technique. Scanning electron microscopy in acombination with energy dispersive X-ray analysis established an extension and local accumulation of the contrasting agent - heavy metallic osmium tetroxide. The presented imaging technique is novel as it will help to understand better the behaviour of cells while interacting with three-dimensional biomaterials. This is crucial for both experimental and clinical tissue engineering applications in order to limit the risk of uncontrolled cell growth, and potentially tumour formation.

Green synthesis of pH-responsive Al2O3 nanoparticles: Application to rapid removal of nitrate ions with enhanced antibacterial activity

In this study, the green treated aluminium oxide nanoparticles (Al2O3 NPs) were synthesized through simple biological reduction method and studied the effect of pH disparity on particle size variation. Green synthesis of Al2O3 NPs from Prunus × yedoensis leaf extract (PYLE) used for removal of nitrate and antibacterial activities for the first time. The synthesized Al2O3 NPs were characterized by different standard analytical and microscopy techniques. The Al2O3 NPs formation occurred through reduction of metal ions followed by nucleation. The size of the pH = 7 Al2O3 NPs are spherical and hexagonal shape and the size ranges between 50–100 nm, although some nanoparticles are agglomerated. The band gap energy values of the pH = 7 Al2O3 NPs were 3.1 eV, which corresponds to the reflectance edge of 420 nm. The surface area of pH = 7 Al2O3 NPs determined from BET measurement was found to be 54.5014 m2/g. The green synthesized Al2O3 NPs were found to be highly efficient in removing nitrates upto 94% from aqueous solutions at pH = 7 under the influence of sunlight irradiation. This removal efficiency of the synthesized NPS is appreciable when compared with previously reported materials of same kind and hence proves its potential for its use in various ion removal from contaminant systems. The detailed in vitro antibacterial activities of the green treated Al2O3 NPs also investigated. The synthesized Al2O3 NPs at pH = 7 was found to have effective antibacterial activity against gram-positive Staphylococcus aureus (S. aureus) and gram-negative Escherichia coli (E. coli). The experimental results of the study reveals that on tuning the size of synthesized Al2O3 NPs and optimizing its pH exhibited higher catalytic activity and antibacterial activity. Hence, these green synthesized Al2O3 NPs is found to have promising applications in pollutant ion removal in aquatic systems.

Photophysical properties of Na+ -indicator dyes suitable for quantitative two-photon fluorescence-lifetime measurements.

Dynamic changes of ion concentrations, which play crucial roles in cellular physiology, can be monitored with appropriate fluorescent indicator dyes. For intracellular sodium ions (Na+ ), certain dyes even allow quantitative measurements with standard microscopic techniques. However, for two-photon microscopy, which allows resolving cells deep in intact tissue, imaging solutions that are fully quantitative are lacking. For the four commercially available Na+ dyes 'SBFI', 'CoroNa Green', 'Sodium Green', and 'Asante NaTRIUM Green-2' (ANG2) we analyzed whether their fluorescent lifetime (LT), i.e., the nanosecond decay of emission of photons after a pulsed excitation, could serve as a quantitative measure of intracellular Na+ . Pulsed excitation in the femtosecond range is an inherent feature of two-photon microscopy and, in combination with fast, single-photon counting microscopes, allows for easy-to-implement LT microscopy. We found that Sodium Green and ANG2 showed strong Na+ -dependent changes in the fluorescence LT, while SBFI showed no, and CoroNa Green only small changes. ANG2, as the brightest dye, was further characterized regarding effects of protons and potassium ions (K+ ), both also present in cells at significant concentrations, on the fluorescence LT. We found that the LT of ANG2 is affected in a predictable manner by Na+ , K+ , and protons. However, our data reveal that the commercial dye must also contain impurities with unexpected Na+ - and K+ -binding characteristics, rendering a quantitative description of the individual lifetime components impractical. We, therefore, adapted a simplified calibration procedure, based on a published approach for Ca2+ imaging, that allows relating the average lifetime to Na+ concentration. With this simplified calibration procedure, ANG2 is well suited for quantitative two-photon Na+ imaging with millimolar sensitivity.