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Darkfield microscopy is an effective technique and well suited for use involving live and unstained biological samples, where a bulky condenser should be precisely aligned in the optical path to produce a cone of illumination light. Here, a compact darkfield illuminator is invented that has a planar shape and can work at broadband wavelengths. It can be easily incorporated into a conventional microscope as a substrate to produce hollow cones of light for large‐area darkfield illumination, resulting in a high‐contrast high‐sensitivity widefield microscopy images. Taking advantages of its planar and compact structure, this darkfield illuminator is successfully integrated with a microfluidic chip; thus, the actions and reactions of biological and chemical specimens flowing inside micrometer‐sized channels, can be real‐time imaged with high contrast and sensitivity in a large field‐of‐view (FoV). For the first time, the work integrates a compact darkfield illuminator with microfluidic chips, which produces a new platform for applications in biology, chemistry, and biomedical engineering. [ABSTRACT FROM AUTHOR]

X‐rays can penetrate deeply into biological cells and thus allow for examination of their internal structures with high spatial resolution. In this study, X‐ray phase‐contrast imaging and tomography is combined with an X‐ray‐compatible optical stretcher and microfluidic sample delivery. Using this setup, individual cells can be kept in suspension while they are examined with the X‐ray beam at a synchrotron. From the recorded holograms, 2D phase shift images that are proportional to the projected local electron density of the investigated cell can be calculated. From the tomographic reconstruction of multiple such projections the 3D electron density can be obtained. The cells can thus be studied in a hydrated or even living state, thus avoiding artifacts from freezing, drying or embedding, and can in principle also be subjected to different sample environments or mechanical strains. This combination of techniques is applied to living as well as fixed and stained NIH3T3 mouse fibroblasts and the effect of the beam energy on the phase shifts is investigated. Furthermore, a 3D algebraic reconstruction scheme and a dedicated mathematical description is used to follow the motion of the trapped cells in the optical stretcher for multiple rotations. [ABSTRACT FROM AUTHOR]

Controlled transport of biological cells in biomedical applications such as sorting, cell sequencing, and assembly of multicellular structures is a technological challenge. Research areas such as drug delivery or tissue engineering can benefit from precise cell location resulting in faster response rates or more complex tissue structures. Using computational methods, different soft magnetic elements with curved edges are designed to form a transport network, enabling transport and all functionalities for the manipulation of microbeads and cells on surfaces by rotational magnetic fields. Building blocks with bimodal functionalities due to segments of differently curved edges permit breakpoints as well as switchable transport via splitting and combining elements. Connecting the elements, networked paths are realized which allow variable movement patterns of magnetic carriers and cells. The direction of magnetic field rotation is altered to direct the beads and cells into different transport lines, and the exact timing is not critical. The networks are used to achieve deterministic movement of microbeads and cells with minimal intervention. Programmed transport over one millimeter with cell transport velocities of several micrometers per s is demonstrated. Based on scalable microchip technology, the networks can be integrated with CMOS‐compatible materials and straightforwardly combined with sensing and diagnostic structures. [ABSTRACT FROM AUTHOR]

The variability in the size of red blood cells (RBCs) is an important additional diagnostic parameter for diseases, which has been established as a part of the complete blood count (CBC). The CBC can be performed using an automated flow cytometer, but it is too bulky and expensive for point‐of‐care testing. A miniaturized lensless imaging system is a competitive modality for a CBC, that is small and inexpensive. There are two challenges in developing a lensless imaging system for taking the CBC, which make the measurement of the RBC size very difficult: the diffraction effect and the low resolution. In this paper, the RBC radius measurement is replaced with a diffraction ring radius measurement. The diffraction ring radius is much larger than the RBC radius. This feature can improve the imaging resolution. Based on Fresnel diffraction, the relationship between the radius of RBCs and the diffraction fringes is analyzed. Finally, a complete measurement algorithm for determining the RBC size based on the lensless imaging system is given, which can be used to measure the variability in the size of RBCs. In our experiment, the maximum error is less than 6.74%. [ABSTRACT FROM AUTHOR]

X‐ray imaging is a complementary method to electron and fluorescence microscopy for studying biological cells. In particular, scanning small‐angle X‐ray scattering provides overview images of whole cells in real space as well as local, high‐resolution reciprocal space information, rendering it suitable to investigate subcellular nanostructures in unsliced cells. One persisting challenge in cell studies is achieving high throughput in reasonable times. To this end, a fast scanning mode is used to image hundreds of cells in a single scan. A way of dealing with the vast amount of data thus collected is suggested, including a segmentation procedure and three complementary kinds of analysis, i.e. characterization of the cell population as a whole, of single cells and of different parts of the same cell. The results show that short exposure times, which enable faster scans and reduce radiation damage, still yield information in agreement with longer exposure times. [ABSTRACT FROM AUTHOR]

X‐ray diffraction imaging is a technique for visualizing the structure of biological cells. In X‐ray diffraction imaging experiments using synchrotron radiation, cryogenic conditions are necessary in order to reduce radiation damage in the biological cells. Frozen‐hydrated biological specimens kept at cryogenic temperatures are also free from drying and bubbling, which occurs in wet specimens under vacuum conditions. In a previous study, the diffraction apparatus KOTOBUKI‐1 [Nakasako et al. (2013), Rev. Sci. Instrum. 84, 093705] was constructed for X‐ray diffraction imaging at cryogenic temperatures by utilizing a cryogenic pot, which is a cooling device developed in low‐temperature physics. In this study a new cryogenic pot, suitable for tomography experiments, has been developed. The pot can rotate a biological cell over an angular range of ±170° against the direction of the incident X‐ray beam. Herein, the details and the performance of the pot and miscellaneous devices are reported, along with established experimental procedures including specimen preparation. The apparatus has been used in tomography experiments for visualizing the three‐dimensional structure of a Cyanidioschyzon merolae cell with an approximate size of 5 µm at a resolution of 136 nm. Based on the experimental results, the necessary improvements for future experiments and the resolution limit achievable under experimental conditions within a maximum tolerable dose are discussed. Diffraction apparatus and experimental procedures for tomography X‐ray diffraction imaging of frozen‐hydrated biological cells have been established. [ABSTRACT FROM AUTHOR]

X‐ray imaging allows biological cells to be examined at a higher resolution than possible with visible light and without some of the preparation difficulties associated with electron microscopy of thick samples. The most used and developed technique is absorption contrast imaging in the water window which exploits the contrast between carbon and oxygen at an energy of around 500 eV. A variety of phase contrast techniques are also being developed. In general these operate at a higher energy, enabling thicker cells to be examined and, in some cases, can be combined with X‐ray fluorescence imaging to locate specific metals. The various methods are based on the differences between the complex refractive indices of the cellular components and the surrounding cytosol or nucleosol, the fluids present in the cellular cytoplasm and nucleus. The refractive indices can be calculated from the atomic composition and density of the components. These in turn can be obtained from published measurements using techniques such as chemical analysis, scanning electron microscopy and X‐ray imaging at selected energies. As examples, the refractive indices of heterochromatin, inner mitochondrial membranes, the neutral core of lipid droplets, starch granules, cytosol and nucleosol are calculated. The refractive index calculations enable the required doses and fluences to be obtained to provide images with sufficient statistical significance, for X‐ray energies between 200 and 4000 eV. The statistical significance (e.g. the Rose criterion) for various requirements is discussed. The calculations reveal why some cellular components are more visible by absorption contrast and why much greater exposure times are required to see some cellular components. A comparison of phase contrast as a function of photon energy with absorption contrast in the water window is provided and it is shown that much higher doses are generally required for the phase contrast measurements. This particularly applies to those components with a high carbon content but with a mass density similar to the surrounding cytosol or nucleosol. The results provide guidance for the most appropriate conditions for X‐ray imaging of individual cellular components within cells of various thicknesses. [ABSTRACT FROM AUTHOR]

For almost half a century, optical tweezers have successfully been used to micromanipulate micrometre and sub‐micrometre‐sized particles. However, in recent years it has been shown experimentally that, compared with single‐beam traps, the use of two opposing and divergent laser beams can be more suitable in studying the elastic properties of biological cells and vesicles. Such a configuration is termed an optical stretcher due to its capability of applying high deforming forces on biological objects such as cells. In this article the experimental capabilities of an optical stretcher as a potential sample delivery system for X‐ray diffraction and imaging studies at synchrotrons and X‐ray free‐electron laser (FEL) facilites are demonstrated. To highlight the potential of the optical stretcher its micromanipulation capabilities have been used to image polymer beads and label biological cells. Even in a non‐optimized configuration based on a commercially available optical stretcher system, X‐ray holograms could be recorded from different views on a biological cell and the three‐dimensional phase of the cell could be reconstructed. The capability of the setup to deform cells at higher laser intensities in combination with, for example, X‐ray diffraction studies could furthermore lead to interesting studies that couple structural parameters to elastic properties. By means of high‐throughput screening, the optical stretcher could become a useful tool in X‐ray studies employing synchrotron radiation, and, at a later stage, femtosecond X‐ray pulses delivered by X‐ray free‐electron lasers. [ABSTRACT FROM AUTHOR]

Abstract: This review highlights the current research on the interactions between biological cells and Layered Double Hydroxides (LDH). The as‐prepared biohybrid materials appear extremely attractive in diverse fields of application relating to health care, environment and energy production. We describe how thanks to the main features of biological cells and LDH layers, various strategies of assemblies can be carried out for constructing smart biofunctional materials. The interactions between the two components are described with a peculiar attention to the adsorption, biocompatibilization, LDH layer internalization, antifouling and antimicrobial properties. The most significant achievements including authors′ results, involving biological cells and LDH assemblies in waste water treatment, bioremediation and bioenergy generation are specifically addressed. [ABSTRACT FROM AUTHOR]

Dielectric spectroscopy (DS) is a non‐invasive, label‐free, and promising technique for measuring dielectric properties of biological cells. Recent developments in microfabrication techniques made it possible to perform DS measurements with minute volume of cell suspensions. However, when the cell size approaches the size of the measurement chamber, especially, for single cell measurements, the analytical models [Maxwell–Wagner and Bruggeman–Hanai (BH) mixture models] to extract cell parameters lose their accuracy. Moreover, variations in the cell position relative to the measurement electrodes decrease the accuracy of the analytical solutions. Impedance spectrum of a typical eukaryotic mammalian cell is generated for different geometrical configurations using finite element. The generated data are fitted to the analytical models and extracted cell parameters are compared with the original values. The results show that BH model works more effectively when chamber to cell radius ratio is <3.5 and chamber height to cell radius ratio is <3. Moreover, it is observed that analytical models estimate cell parameters with major errors when the cells are in the vicinity of the electrodes. However, for high‐volume fraction simulations, the BH model was able to predict cell parameters better even in the vicinity of the electrodes. [ABSTRACT FROM AUTHOR]

Research on nanometer-sized luminescent semiconductors and their biological applications in detectors and contrasting agents is an emergent field in nanotechnology. When new nanosize technologies are developed for human health applications, their interaction with biological systems should be studied in depth. Rare-earth elements are used in medical and industrial applications, but their toxic effects are not known. In this work, the biological interaction between terbium-doped gadolinium oxysulfide nanoparticles (GOSNPs) with human peripheral blood mononuclear cells (PBMC), human-derived macrophages (THP-1), and human cervical carcinoma cell (HeLa) were evaluated. The GOSNPs were synthetized using a hydrothermal method to obtain monodisperse nanoparticles with an average size of 91 ± 9 nm. Characterization techniques showed the hexagonal phase of the Gd2O2S:Tb3+ free of impurities, and a strong green emission at λemi = 544 nm produced by Tb3+ was observed. Toxic effects of GOSNPs were evaluated using cell viability, apoptosis, cell-cycle progression, and immunological response techniques. In addition, an Artemia model was used to assess the toxicity in vivo. Results indicated cell apoptosis in both types of cells with less sensitivity for PBMC cells compared to HeLa cells. In addition, no toxic effects were observed in the in vivo model of Artemia. Moreover, GOSNPs significantly reduced the activation and cell-cycle progression of PBMC and HeLa cells, respectively. Interestingly, an increase in proinflammatory cytokines was not observed. Our data suggest that fluorescence applications of GOSNPs for biolabeling are not toxic in primary immune cells and they may have an immunomodulatory effect. © 2015 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 605-615, 2017. [ABSTRACT FROM AUTHOR]

A design of experiment (DOE) strategy applied to multi‐objective optimisation is proposed in order to evaluate the influence of design variables variations to optimised quantities. A secondary objective function is the sensitivity of a primary objective function to design variable variations evaluated by means of DOE strategy. The optimisation problem includes also a third objective function that considers device constraint because of technological limitations on power generator. The proposed case study deals with the design of an electromagnetic device that will be used to carry out laboratory experiments on magneto‐fluid hyperthermia, that is, a clinic treatment for cancer cure. The induction system is designed to apply a controlled time‐varying magnetic field to biological cells, cultured in Petri dish and mixed with magnetic nanoparticles. This study presents an original cost‐effective method of multi‐objective design optimisation taking into account design uncertainties. [ABSTRACT FROM AUTHOR]

Contactless method for manipulation of polar or polarisable micro and nanoscale particles based on the dielectrophoresis force exerted by the induced electric field in high pulsed magnetic field is presented in this study. Finite element method analysis of the magnetic and resulting induced electric fields is carried out. The structure of the magnetic field generator that was based on a controlled frequency spark gap, and the structure of the coil that was used as a load are described. Experimental data showing positive dielectrophoresis on the Jurkat T‐lymphoblasts is presented. The study discusses further developments of the technique, its limitations and possible applications. [ABSTRACT FROM AUTHOR]

An error in the calculation for X‐ray absorption imaging has been identified in the paper by Nave (2018) [J. Synchrotron Rad.25, 1490–1504]. The required fluence and dose in the paper are a factor of ten too low for this mode of imaging. Corrections are given for the calculations of fluence and dose for X‐ray imaging of biological cells by absorption in the paper by Nave (2018) [J. Synchrotron Rad.25, 1490–1504]. [ABSTRACT FROM AUTHOR]

Abstract: In this work, a numerical study of the interaction of an electromagnetic field with a biological cell in the different phases of mitosis is presented. In particular, the validity of the single‐shell model during mitosis from a geometrical viewpoint has been considered. We consider the Jurkat cell for our analysis and model the content of the cell, composed by the nucleus and different organelles immersed in cytoplasm and delimited by the cell membrane, as a single material with appropriate electromagnetic properties derived by making use of effective medium approximation methods, i.e., we used a quasistatic approach to deal with the cell. To validate the model, a comparison between the original and 2 approximated geometry models is made and the results are in very good accordance. Subsequently, an analysis of the scattered field indicates that the most sensitive component to the mitosis phase is the one parallel to the segment joining the centers of the cells. [ABSTRACT FROM AUTHOR]