Chemistry News

Condenser Aperture Diaphragm Control Of Specimen Contrast

posted May 13, 2019, 10:04 AM by ­김형민‎(응용화학부)‎

Super-resolution retinal imaging using optically reassigned scanning laser ophthalmoscopy

posted May 13, 2019, 6:46 AM by ­김형민‎(응용화학부)‎

Super-resolution optical microscopy techniques have enabled the discovery and visualization of numerous phenomena in physics, chemistry and biology. However, the highest resolution super-resolution techniques depend on nonlinear fluorescence phenomena and are thus inaccessible to the myriad applications that require reflective imaging. One promising super-resolution technique is optical reassignment, which so
far has only shown potential for fluorescence imaging at low speeds. Here, we present novel advances in optical reassignment to adapt it for any scanning microscopy, including reflective imaging, and enable an order of magnitude faster image acquisition than previous optical reassignment techniques. We utilized these advances to implement optically reassigned scanning laser ophthalmoscopy, an in vivo super-resolution human retinal imaging device not reliant on confocal gating. Using this instrument, we achieved high-resolution imaging of living human retinal cone photoreceptor cells (determined by minimum foveal eccentricity) without adaptive optics or
chemical dilation of the eye.

Articles in J. Biophoton.

posted May 3, 2019, 6:36 AM by ­김형민‎(응용화학부)‎

Raman spectroscopy investigation of biochemical changes in tumor spheroids with aging and after treatment with staurosporine

There has been increasing use of in vitro cell culture models that more realistically replicate the three‐dimensional (3D) environment found in vivo. Multicellular tumor spheroids (MTS) using cell lines or patient‐derived organoids have become an important in vitro drug development tool, where cells are grown in a 3D “sphere” that exhibits many of the characteristics found in vivo. Significantly, MTS develop gradients in nutrients and oxygen, commonly found in tumors that contribute to therapy resistance. While MTS show promise as a more realistic in vitro culture model, there is a massive need to improve imaging technologies for assessing biochemical characteristics and drug response in such models to maximize their translation into useful applications such as high throughput screening (HTS). In this study, we investigate the potential for Raman spectroscopy to unveil biochemical information in MTS and have investigated how spheroid age influences drug response, shedding light on increased therapy resistance in developing tumors. The wealth of molecular level information delivered by Raman spectroscopy in a noninvasive manner, could aid translation of these 3D models into HTS applications.

Simultaneous photoreduction and Raman spectroscopy of red blood cells to investigate the effects of organophosphate exposure

Simultaneous photoreduction and Raman spectroscopy with 532 nm laser has been used to study the effects of organophosphate (chlorpyrifos [CPF]) exposure on human red blood cells (RBCs). Since in RBCs, auto‐oxidation causes oxidative stress, which, in turn, is balanced by the cellular detoxicants, any possible negative effect of CPF on this balance should results in an increased level of damaged (permanently oxygenated) hemoglobin. Therefore, when 532 nm laser, at a suitable power, was applied to photoreduce the cells, only common oxygenated form of hemoglobin got photoreduced leaving the permanently oxygenated hemoglobin detectable in the Raman spectra simultaneously excited by the same laser. Using the technique effects of CPF to build up oxidative stress on RBCs could be detected at concentrations as low as 10 ppb from a comparison of relative strengths of different Raman bands. Experiments performed using simultaneously exposing the cells, along with CPF, to H2O2 (oxidative agent) and/or 3‐Aminotriazole (inhibitor of anti‐oxidant catalase), suggested role of CPF to suppress the cellular anti‐oxidant mechanism. Since the high level of damaged hemoglobin produced by the action of CPF (at concentrations >100 ppm) is expected to cause membrane damage, atomic force microscopy (AFM) was used to identify such damages.Upper panel: Raman spectra of normal, photoreduced CPF exposed and unexposed RBCs. Lower panel: The weak Fe‐O2 Raman band for CPF exposed cells shown on the left. The AFM images of unexposed and exposed cells are shown on the right. Scale bar, 2.5 μm.

Bioinspired Amyloid Nanodots with Visible Fluorescence

posted May 1, 2019, 6:24 AM by ­김형민‎(응용화학부)‎

Nanoscale bioimaging is a highly important scientific and technological tool, where fluorescent (FL) proteins, organic molecular dyes, inorganic quantum dots, and lately carbon dots are widely used as light emitting biolabels. In this work, a new class of visible FL bioorganic nanodots, self‐assembled from short peptides of different composition and origin, is introduced. It is shown that the electronic energy spectrum of native nonfluorescent peptide nanodots (PNDs) is deeply modified upon thermally mediated refolding of their biological secondary structure from native metastable to stable β‐sheet rich structure. This refolding leads to the appearance of a broadband optical absorption across visible region and tunable, excitation‐dependent visible FL of the nanodots with a high quantum yield of ≈30%. It is shown that this intriguing biophotonic effect appears in several peptides/proteins and does not require the presence of aromatic residues. It is assumed that the origin of the phenomenon is related to proton transfer along network of reconstructed intermolecular hydrogen bonds, stabilizing the thermally induced supramolecular β‐sheet structure. The biocompatible FL PNDs can be potentially applied as high‐resolution bioimaging labels toward advanced biotechnology and biomedical theranostics.

Deep‐Ultraviolet Biomolecular Imaging and Analysis

posted May 1, 2019, 6:18 AM by ­김형민‎(응용화학부)‎

Deep‐ultraviolet light, 200–300 nm in wavelength, interacts with nucleic acids and proteins strongly compared to visible and infrared light. In this article, the interaction between deep‐ultraviolet photons and biomolecules is discussed. Especially, the absorption and autofluorescence of biomolecules by the deep‐ultraviolet excitation are examined. Applications of deep‐ultraviolet absorption and autofluorescence to label‐free biomolecular imaging and analysis of cells and tissues are shown. Resonant Raman scattering at nucleotide bases and aromatic amino acids as another important topic of deep‐ultraviolet photonics is reviewed in biomolecular imaging and analysis. The discussion extends to the recent progress in the development of deep‐ultraviolet microscopes as well as a variety of deep‐ultraviolet optical devices such as light sources, detectors, and objectives. The issue of photodamage due to deep‐ultraviolet irradiation on cells and tissues is also discussed. It has been recently suppressed with use of lanthanide ions. The experimental results of the photodamage suppression are shown. For surface‐enhanced resonant Raman scattering, autofluorescence enhancement, and tip‐enhanced resonant Raman scattering microscopy, plasmonic materials applicable in the deep‐ultraviolet range are discussed.

Charting a course for chemistry

posted Apr 24, 2019, 6:38 AM by ­김형민‎(응용화학부)‎

To mark the occasion of Nature Chemistry turning 10 years old, we asked scientists working in different areas of chemistry to tell us what they thought the most exciting, interesting or challenging aspects related to the development of their main field of research will be — here is what they said.

Autofluorescence lifetime augmented reality as a means for real-time robotic surgery guidance in human patients

posted Apr 21, 2019, 12:22 PM by ­김형민‎(응용화학부)‎

Due to loss of tactile feedback the assessment of tumor margins during robotic surgery is based only on visual inspection, which is neither significantly sensitive nor specific. Here we demonstrate time-resolved fluorescence spectroscopy (TRFS) as a novel technique to complement the visual inspection of oral cancers during transoral robotic surgery (TORS) in real-time and without the need for exogenous contrast agents. TRFS enables identification of cancerous tissue by its distinct autofluorescence signature that is associated with the alteration of tissue structure and biochemical profile. A prototype TRFS instrument was integrated synergistically with the da Vinci Surgical robot and the combined system was validated in swine and human patients. Label-free and real-time assessment and visualization of tissue biochemical features during robotic surgery procedure, as demonstrated here, not only has the potential to improve the intraoperative decision making during TORS but also other robotic procedures without modification of conventional clinical protocols.

CMOS vs CCD sensor

posted Apr 21, 2019, 12:10 PM by ­김형민‎(응용화학부)‎

Modern CMOS Sensors and Their Use in Fluorescence-Based Applications 

This White Paper outlines the possibilities and application areas of modern CMOS sensor technology in medicine and science. System manufacturers whose devices are equipped with CCD sensors and who are therefore increasingly looking for a suitable camera replacement will find valuable explanations and examples for uses in fluorescence applications here. Many medical, scientific or clinical diagnostic applications work with fluorescence-based methods. Due to their resolution and sensitivity particularly under low-light conditions, CCD sensors have so far been the established standard in these applications, but modern CMOS sensors have also caught on in these areas in recent years. In this White Paper, Dr. Felix Asche, Product Manager at Basler, outlines relevant technical correlations and offers various examples to show the diverse opportunities and advantages of modern CMOS technology in high-performance, non-cooled cameras.

Video-rate large-scale imaging with Multi-Z confocal microscopy

posted Mar 25, 2019, 6:23 AM by ­김형민‎(응용화학부)‎

Fast, volumetric imaging over large scales has been a long-standing challenge in biological microscopy. To address this challenge, we report an augmented variant of confocal microscopy that uses a series of reflecting pinholes axially distributed in the detection space, such that each pinhole probes a different depth within the sample. We thus obtain simultaneous multiplane imaging without the need for axial scanning. Our microscope technique is versatile and configured here to provide two-color fluorescence imaging with a field of view larger than a millimeter at video rate. Its general applicability is demonstrated with neuronal imaging of both Caenorhabditis elegans and mouse brains in vivo.

1-10 of 55