Full‐field functional optical hemocytometer (FFOH), based on the absorption intensity fluctuation modulation (AIFM) effect, is in vivo label‐free image method for capillaries of near‐transparent live biological specimens. FFOH can provide a flow video, flow velocity measurement and RBC count, simultaneously. The zebrafish experimental result shows the potential to study the physiological mechanisms of the blood circulation systems. Further details can be found in the article by Fuli Zhang et al. ( e201700039 )
Raman images were used to study the effect of the contaminant chlorpyriphos‐oxon on zebrafish eye samples. Multivariate Curve Resolution‐Alternating Least Squares (MCR‐ALS) was used to obtain the distribution maps and spectral signatures of biological components present in the images analyzed. The use of MCRALS spectral signatures as starting information for Partial Least Squares‐Discriminant Analysis allowed statistical assessment of the effect of the contaminant at a specific tissue level. Further details can be found in the article by Víctor Olmos et al. ( e201700089 ).
We disclose a theranostic device for performing image‐guided riboflavin/UV‐A corneal cross‐linking. The device determines treatment efficacy by real time monitoring of riboflavin concentration in the corneal stroma. The study shows efficacy of the device in eye bank human donor tissues. Further details can be found in the article by Giuseppe Lombardo et al. ( e201800028 )
A label‐free interferometric transducer showing a theoretical detection limit for homogeneous sensing of 5 × 10–8 RIU, being equivalent to a protein mass coverage resolution of 2.8 fg mm–2, is used to develop a high sensitive biosensor for protein detection. The extreme sensitivity of this transducer combined with a selective bioreceptor layer enables the direct evaluation of the human growth hormone (hGH) in undiluted urine matrix in the 10 pg mL–1 range.
Germanium vs Silicon: All‐dielectric nanoparticles provides the heat resistance for proteins under light‐induced heating. Further details can be found in the article by Andrei A. Krasilin et al. ( e201700322 )
Photoconversion, an irreversible shift in a fluorophore emission spectrum after light exposure, is a powerful tool for marking cellular and subcellular compartments and tracking their dynamics in vivo. This paper reports on the photoconversion properties of Di‐8‐ANEPPS, a commercially available membrane dye. When illuminated with near‐infrared femtosecond laser pulses, Di‐8‐ANEPPS undergoes multiphoton photoconversion as indicated by the supralinear dependence of the conversion rate ρpc on the incident power (), and by the ability to photoconvert a thin optical section in a three‐dimensional matrix. The characteristic emission spectrum changed from red to blue, and ratiometric analysis on single cells in vitro revealed a 65‐fold increase in the blue to red wavelength ratio after photoconversion. The spectral shift is preserved in vivo for hours, making Di‐8‐ANEPPS a useful dye for intravital cell marking and tracking applications.
We use terahertz imaging to measure four human skin scars in vivo. Clear contrast between the refractive index of the scar and surrounding tissue was observed for all of the scars, despite some being difficult to see with the naked eye. Additionally, we monitored the healing process of a hypertrophic scar. We found that the contrast in the absorption coefficient became less prominent after a few months post‐injury, but that the contrast in the refractive index was still significant even months post‐injury. Our results demonstrate the capability of terahertz imaging to quantitatively measure subtle changes in skin properties and this may be useful for improving scar treatment and management.
One of the main challenges for laser‐scanning microscopy of biological tissues with refractive heterogeneities is the degradation in spatial resolution that occurs as a result of beam steering and distortion. This challenge is particularly significant for dual‐axis confocal (DAC) microscopy, which achieves improved spatial‐filtering and optical‐sectioning performance over traditional confocal microscopy through off‐axis illumination and collection of light with low‐numerical aperture (NA) beams that must intersect precisely at their foci within tissues. DAC microscope image quality is sensitive to positional changes and distortions of these illumination‐ and collection‐beam foci. Previous studies have shown that Bessel beams display improved positional stability and beam quality than Gaussian beams when propagating through tissues with refractive heterogeneities, which suggests that Bessel‐beam illumination may enhance DAC microscopy of such tissues. Here, we utilize both Gaussian and Bessel illumination in a point‐scanned DAC microscope and quantify the resultant degradation in resolution when imaging within heterogeneous optical phantoms and fresh tissues. Results indicate that DAC microscopy with Bessel illumination exhibits reduced resolution degradation from microscopic tissue heterogeneities compared to DAC microscopy with conventional Gaussian illumination.
Optical Breast Spectroscopy (OBS) has been shown to predict mammographic breast density, a strong breast cancer risk factor. OBS is a low‐cost technique applicable at any age. OBS information may be useful for personalizing breast cancer screening programs based on risk to improve consensus on and adherence to screening guidelines. To facilitate the use of OBS in population‐wide studies, a research prototype OBS device was modified to make it portable and cheaper and to require less operator interaction. Two major changes were made: (1) the broadband light source was replaced with a laser module with 13 individual wavelengths turned on sequentially, enabling the use of photodiode detectors instead of a spectrometer, and (2) the light sources and detectors were placed in fixed positions within 4 sizes of cup, eliminating the need for placement by the operator. Wavelengths were selected using data from two previous studies. The reduction in spectral content did not significantly reduce the ability to distinguish between different risk groups. Positions for the light sources and detectors were chosen based on Monte Carlo simulations to match the optically interrogated volumes of the original device. Two light sources and six detectors per cup were used in the final design.
TIRF and STORM microscopy are super‐resolving fluorescence imaging modalities for which current implementations on standard microscopes can present significant complexity and cost. We present a straightforward and low‐cost approach to implement STORM and TIRF taking advantage of multimode optical fibres and multimode diode lasers to provide the required excitation light. Combined with open source software and relatively simple protocols to prepare samples for STORM, including the use of Vectashield for non‐TIRF imaging, this approach enables TIRF and STORM imaging of cells labelled with appropriate dyes or expressing suitable fluorescent proteins to become widely accessible at low cost.
Tissue autofluorescence provides fluorescence lifetime contrast between acellular tissue and that containing newly seeded cells. Fiber‐based fluorescence lifetime imaging (FLIm) can be used for tracking recellularization of engineered vascular grafts and potential matrix remodeling at large scale, without compromising sample integrity. FLIm cellular contrast was verified in a subset of samples seeded with eGFP‐labelled cells. Results suggests fiberbased FLIm is a suitable tool for monitoring recellularization of engineered tissue nondestructively. Further details can be found in the article by Alba Alfonso‐Garcia, Jeny Shklover, Benjamin E. Sherlock, et al. ( e201700391 ).
Bladder cancer is among the most common cancers in the UK and conventional detection techniques suffer from low sensitivity, low specificity, or both. Recent attempts to address the disparity have led to progress in the field of autofluorescence as a means to diagnose the disease with high efficiency, however there is still a lot not known about autofluorescence profiles in the disease. The multi‐functional diagnostic system “LAKK‐M” was used to assess autofluorescence profiles of healthy and cancerous bladder tissue to identify novel biomarkers of the disease. Statistically significant differences were observed in the optical redox ratio (a measure of tissue metabolic activity), the amplitude of endogenous porphyrins and the NADH/porphyrin ratio between tissue types. These findings could advance understanding of bladder cancer and aid in the development of new techniques for detection and surveillance.
A new type of high‐throughput imaging flow cytometer (>20 000 cells s‐1) based upon an all‐optical ultrafast laser‐scanning imaging technique, called free‐space angular‐chirp‐enhanced delay (FACED) is reported. FACED imaging flow cytometers enables high‐throughput visualization of functional morphology of individual cells with subcellular resolution. It critically empowers largescale and deep characterization of single cells and their heterogeneity with high statistical power— an ability to become increasingly critical in single‐cell analysis adopted in a wide range of biomedical and life‐science applications. Further details can be found in the article by Wenwei Yan et al. ( e201700178 )
Third Harmonic Generation (THG) microscopy as a non‐invasive, label free imaging methodology, allows linkage of lipid profiles with various breast cancer cells. The collected THG signal arise mostly from the lipid droplets and the membrane lipid bilayer. Quantification of THG signal can accurately distinguish HER2‐positive cells. Further analysis using Fourier transform infrared (FTIR) spectra reveals cancer‐specific profiles, correlating lipid raft‐corresponding spectra to THG signal, associating thus THG to chemical information.
Protein secondary structural alteration in the serum sample as induced by colitis has been demonstrated via the spectral fitting. Using DSS mouse models of acute colitis and IL10‐/‐ for chronic colitis, a significant difference in the integral ratio of Gaussian energy bands representing α‐helix and β‐pleated sheet structures were obtained. Further details can be found in the article by Jitto Titus et al. ( e201700057 ).
The biomaterial distribution and its molecular mechanism of embryonic development in Japanese medaka fish were visualized without staining using high‐speed near‐infrared imaging. It was a remarkable achievement to visualize the structures of eyes, lipid bilayer membranes, micelles, and water structural variations at the interface of different substances. Furthermore, insights on lipid metabolism and membrane functions were obtained from the biased distribution of lipoproteins and the presence of unsaturated fatty acids in the egg membrane. Further details can be found in the article by Mika Ishigaki ( e201700115 )
Based on multicolor quantum dots (QDs) labeling, the joint tagging assisted super‐resolution radial fluctuation (JT‐SRRF) nanoscopy achieves high‐fidelity super‐resolution imaging of subcellular microtubules and fast live‐cell parallel tracking of cholera toxin subunit B (CTB) induced lipid clusters spatially distributed below the optical diffraction limit. This method paves the way for fast high‐density parallel tracking, which is especially beneficial for the investigation of the intensive dynamics in live‐cell applications. Further details can be found in the article by Zhiping Zeng, Jing Ma, Peng Xi, and Canhua Xu ( e201800020 ).
SECTR is a novel multimodal imaging platform for combined volumetric optical coherence tomography (OCT) and en face spectrally encoded reflectometry (SER). The authors demonstrate three‐dimensional motion‐tracking with millisecond temporal and micron spatial resolution using complementary data from OCT and SER, and preliminary algorithms and results showing real‐time image aiming and multi‐volumetric mosaicking for reconstruction of wide‐field composites. The image shows a noninvasively imaged nine‐field mosaic of in vivo human retina and depth‐resolved visualization of tissue microstructures. Further details can be found in the article by Mohamed T. El‐Haddad, Ivan Bozic, and Yuankai K. Tao ( e201700268 )
Gold nanoparticles serve as imaging contrast agents useful for two‐photon nonlinear microscopy of biological cells and tissues. In this study, 100‐nm‐sized gold particles with a multitude of nanopores embedded inside have been physically synthesized and investigated for the plasmonic enhancement in two‐photon luminescence. Exhibiting remarkable potential for two‐photon imaging, the porous gold nanoparticles boost near‐infrared light absorption substantially and allow emission signals 20 times brighter than gold nanorods being currently used as typical imaging agents. Further details can be found in the article by Joo H. Park et al. ( e201700174 )
The internalization kinetics and intracellular spatial distribution of functionalized diatomite nanoparticles in human lung epidermoid carcinoma cell line have been investigated by confocal fluorescence and Raman microscopy. In this context, Raman imaging due to its non‐destructive, chemically selective and label‐free working principle provides evidence that the nanovectors are internalized and co‐localize with lipid environments, suggesting an endocytic internalisation route. Nanoparticle uptakes and intracellular persistence are observed up to 72 hours, without damage to cell viability or morphology. Further details can be found in the article by Stefano Managò et al. ( e201700207 )
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