Two-dimensional (2D) nanomaterials, such as graphene-based materials and transition metal dichalcogenide (TMD) nanosheets, are promising materials for biomedical applications owing to their remarkable cytocompatibility and physicochemical properties. On the basis of their potent antibacterial properties, 2D materials have potential as antibacterial films, wherein the 2D nanosheets are immobilized on the surface and the bacteria may contact with the basal planes of 2D nanosheets dominantly rather than contact with the sharp edges of nanosheets. To address these points, in this study, we prepared an effective antibacterial surface consisting of representative 2D materials, i.e., graphene oxide (GO) and molybdenum disulfide (MoS2), formed into nanosheets on a transparent substrate for real device applications. The antimicrobial properties of the GO–MoS2 nanocomposite surface toward the Gram-negative bacteria Escherichia coli were investigated, and the GO–MoS2 nanocomposite exhibited enhanced antimicrobial ef...

Antibacterial Activities of Graphene Oxide–Molybdenum Disulfide Nanocomposite Films

Three-dimensional imaging of biological cells is crucial for the investigation of cell biology, providing valuable information to reveal the mechanisms behind pathophysiology of cells and tissues. Recent advances in optical diffraction tomography (ODT) have demonstrated the potential for the study of various cells with its unique advantages of quantitative and label-free imaging capability. To provide insight on this rapidly growing field of research and to discuss its applications in biology and medicine, we present the summary of the ODT principle and highlight recent studies utilizing ODT with the emphasis on the applications to the pathophysiology of cells.

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Optical diffraction tomography techniques for the study of cell pathophysiology

Lipid droplets (LDs) are subcellular organelles with important roles in lipid storage and metabolism and involved in various diseases including cancer, obesity, and diabetes. Conventional methods, however, have limited ability to provide quantitative information on individual LDs and have limited capability for three-dimensional (3-D) imaging of LDs in live cells especially for fast acquisition of 3-D dynamics. Here, we present an optical method based on 3-D quantitative phase imaging to measure the 3-D structural distribution and biochemical parameters (concentration and dry mass) of individual LDs in live cells without using exogenous labelling agents. The biochemical change of LDs under oleic acid treatment was quantitatively investigated, and 4-D tracking of the fast dynamics of LDs revealed the intracellular transport of LDs in live cells.

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Three-dimensional label-free imaging and quantification of lipid droplets in live hepatocytes.

We present a time-multiplexing structured illumination control technique for optical diffraction tomography (ODT). Instead of tilting the angle of illumination, time-multiplexed sinusoidal illumination is exploited using a digital micromirror device (DMD). The present method effectively eliminates unwanted diffracted beams from binary DMD patterns, which deteriorates the image quality of the ODT in the previous binary Lee hologram method. We experimentally show the feasibility and advantage of the present method by reconstructing three-dimensional refractive index distributions of various samples and comparing with a conventional Lee hologram method.

Time-multiplexed structured illumination using a DMD for optical diffraction tomography.

Identification of lymphocyte cell types are crucial for understanding their pathophysiological roles in human diseases. Current methods for discriminating lymphocyte cell types primarily rely on labelling techniques with magnetic beads or fluorescence agents, which take time and have costs for sample preparation and may also have a potential risk of altering cellular functions. Here, we present the identification of non-activated lymphocyte cell types at the single-cell level using refractive index (RI) tomography and machine learning. From the measurements of three-dimensional RI maps of individual lymphocytes, the morphological and biochemical properties of the cells are quantitatively retrieved. To construct cell type classification models, various statistical classification algorithms are compared, and the k-NN (k = 4) algorithm was selected. The algorithm combines multiple quantitative characteristics of the lymphocyte to construct the cell type classifiers. After optimizing the feature sets via cross-validation, the trained classifiers enable identification of three lymphocyte cell types (B, CD4+ T, and CD8+ T cells) with high sensitivity and specificity. The present method, which combines RI tomography and machine learning for the first time to our knowledge, could be a versatile tool for investigating the pathophysiological roles of lymphocytes in various diseases including cancers, autoimmune diseases, and virus infections.

/pdf/identification-of-non-activated-lymphocytes-using-three-5auhwmua0v.pdf

Identification of non-activated lymphocytes using three-dimensional refractive index tomography and machine learning.

Optical diffraction tomography (ODT) is an interferometric microscopy technique capable of measuring 3-D refractive index (RI) distribution of transparent samples. Multiple 2-D holograms of a sample illuminated with various angles are measured, from which 3-D RI map of the sample is reconstructed via the diffraction theory. ODT has been proved as a powerful tool for the study of biological cells, due to its non-invasiveness, label-free and quantitative imaging capability. Recently, our group has demonstrated that a digital micromirror device (DMD) can be exploited for fast and precise control of illumination beams for ODT. In this work, we systematically study the precision and stability of the ODT system equipped with a DMD and present measurements of 3-D and 4-D RI maps of various types of live cells including human red blood cells, white blood cells, hepatocytes, and HeLa cells. Furthermore, we also demonstrate the effective visualization of 3-D RI maps of live cells utilizing the measured information about the values and gradient of RI tomograms.

Optical diffraction tomography using a digital micromirror device for stable measurements of 4D refractive index tomography of cells

Optical diffraction tomography using a digital micromirror device for stable measurements of 4-D refractive index tomography of cells

This technique lets users manipulate 3D objects as if they had actually grabbed them. It employs a grabbing metaphor to provide the mapping protocol for finding the desired reference frame for the object. The technique projects the user's hand into the virtual environment; a virtual-handle avatar provides feedback.

3D Object Manipulation Using Virtual Handles with a Grabbing Metaphor

Clinical, Radiographic, and Morphometric Risk Factors for Adjacent and Remote Vertebral Compression Fractures Over a Minimum Follow-up of 4 Years After Percutaneous Vertebroplasty for Osteoporotic Vertebral Compression Fractures: Novel Three-dimensional Voxel-Based Morphometric Analysis

Optical diffraction tomography (ODT) constitutes a novel approach for acquiring cell images since it is capable of capturing morphology of a living cell without chemical treatment. ODT is an interferometric technique that measures the 3D refractive index (RI) distribution of optically transparent samples such as biological cells. Unlike other cell imaging modalities, naive ODT data do not contain encoded information about the cellular properties such as labeled protein in fluorescent microscopic data or the fixed border of a cell wall in scanning electron microscopic data. Therefore, specifying the region of interest in the raw image is an important and challenging task for a quantitative analysis of ODT cell data. We propose an interactive interface for reconstructing 3D shape of cells from ODT image data based on intervening visualization results of the cell data to guide the investigator observing the overall blueprint of cell morphology. The cell organelles are segmented based on the lookup table referring corresponding transfer function items adopted from volume rendering technique. The final shape of the cell is then constructed as mesh models from the segmentation results for further quantitative analyses. In this paper, we also demonstrate the various modeling options accounting characteristics of target cell.

Taeho Kim

Papers

Optical diffraction tomography using a digital micromirror device for stable measurements of 4D refractive index tomography of cells

Optical diffraction tomography using a digital micromirror device for stable measurements of 4-D refractive index tomography of cells

3D Object Manipulation Using Virtual Handles with a Grabbing Metaphor

Clinical, Radiographic, and Morphometric Risk Factors for Adjacent and Remote Vertebral Compression Fractures Over a Minimum Follow-up of 4 Years After Percutaneous Vertebroplasty for Osteoporotic Vertebral Compression Fractures: Novel Three-dimensional Voxel-Based Morphometric Analysis

Analyzing 3D cell data of optical diffraction tomography through volume rendering