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Application of Quantum Dots in Biological Imaging  [PDF]
Shan Jin,Yanxi Hu,Zhanjun Gu,Lei Liu,Hai-Chen Wu
Journal of Nanomaterials , 2011, DOI: 10.1155/2011/834139
Abstract: Quantum dots (QDs) are a group of semiconducting nanomaterials with unique optical and electronic properties. They have distinct advantages over traditional fluorescent organic dyes in chemical and biological studies in terms of tunable emission spectra, signal brightness, photostability, and so forth. Currently, the major type of QDs is the heavy metal-containing II-IV, IV-VI, or III-V QDs. Silicon QDs and conjugated polymer dots have also been developed in order to lower the potential toxicity of the fluorescent probes for biological applications. Aqueous solubility is the common problem for all types of QDs when they are employed in the biological researches, such as in vitro and in vivo imaging. To circumvent this problem, ligand exchange and polymer coating are proven to be effective, besides synthesizing QDs in aqueous solutions directly. However, toxicity is another big concern especially for in vivo studies. Ligand protection and core/shell structure can partly solve this problem. With the rapid development of QDs research, new elements and new morphologies have been introduced to this area to fabricate more safe and efficient QDs for biological applications. 1. Introduction Semiconductor nanocrystals, or so-called quantum dots (QDs), show unique optical and electronic properties, including size-tunable light emission, simultaneous excitation of multiple fluorescence colors, high signal brightness, long-term photostability, and multiplex capabilities [1–4]. Such QDs have significant advantages in chemical and biological researches in contrast to traditional fluorescent organic dyes and green fluorescent proteins on account of their photobleaching, low signal intensity, and spectral overlapping [5–7]. These properties of QDs have attracted great interest in biology and medicine in recent years. At present QDs are considered to be potential candidates as luminescent probes and labels in biological applications, ranging from molecular histopathology, disease diagnosis, to biological imaging [8–10]. Numerous studies have reported the use of QDs for in vitro or in vivo imaging of sentinel lymph nodes [11–17], tumor-specific receptors [18–20], malignant tumor detectors [21], and tumor immune responses [22]. However, the major concerns about potential toxicity of II-IV QDs (such as CdTe and CdSe) have cast doubts on their practical use in biology and medicine. Indeed, several studies have reported that size, charge, coating ligands, and oxidative, photolytic, and mechanical stability, each can contribute to the cytotoxicity of cadmium-containing QDs.
High-Speed Coherent Raman Fingerprint Imaging of Biological Tissues  [PDF]
Charles H. Camp Jr.,Young Jong Lee,John M. Heddleston,Christopher M. Hartshorn,Angela R. Hight Walker,Jeremy N. Rich,Justin D. Lathia,Marcus T. Cicerone
Physics , 2014, DOI: 10.1038/nphoton.2014.145
Abstract: We have developed a coherent Raman imaging platform using broadband coherent anti-Stokes Raman scattering (BCARS) that provides an unprecedented combination of speed, sensitivity, and spectral breadth. The system utilizes a unique configuration of laser sources that probes the Raman spectrum over 3,000 cm$^{-1}$ and generates an especially strong response in the typically weak Raman "fingerprint" region through heterodyne amplification of the anti-Stokes photons with a large nonresonant background (NRB) while maintaining high spectral resolution of $<$ 13 cm$^{-1}$. For histology and pathology, this system shows promise in highlighting major tissue components in a non-destructive, label-free manner. We demonstrate high-speed chemical imaging in two- and three-dimensional views of healthy murine liver and pancreas tissues and interfaces between xenograft brain tumors and the surrounding healthy brain matter.
Direct imaging of molecular symmetry by coherent anti-Stokes Raman scattering  [PDF]
Carsten Cleff,Alicja Gasecka,Patrick Ferrand,Hervé Rigneault,Sophie Brasselet,Julien Duboisset
Physics , 2015,
Abstract: Nonlinear optical methods, such as coherent anti-Stokes Raman scattering (CARS) and stimulated Raman scattering (SRS), are able to perform label free imaging, with chemical bonds specificity. Here, we demonstrate that the use of circularly polarized light allows to retrieve not only the chemical nature but also the symmetry of the probed sample, in a single shot measurement. Our symmetry-resolved scheme offers simple access to the local organization of vibrational bonds and as a result provides enhanced image contrast for anisotropic samples as well as an improved chemical selectivity. We quantify the local organization of vibrational bonds on crystalline and biological samples, thus providing new information not accessible by spontaneous Raman and SRS techniques. This work stands for a novel symmetry-resolved contrast in vibrational microscopy, with potential application in biological diagnostic.
Raman spectroscopy and imaging of graphene  [PDF]
Zhen hua Ni,Ying ying Wang,Ting Yu,Ze xiang Shen
Physics , 2008,
Abstract: Graphene has many unique properties that make it an ideal material for fundamental studies as well as for potential applications. Here we review the recent results on the Raman spectroscopy and imaging of graphene. Raman spectroscopy and imaging can be used as a quick and unambiguous method to determine the number of graphene layers. Following, the strong Raman signal of single layer graphene compared to graphite is explained by an interference enhancement model. We have also studied the effect of substrates, the top layer deposition, the annealing process, as well as folding (stacking order) on the physical and electronic properties of graphene. Finally, Raman spectroscopy of epitaxial graphene grown on SiC substrate is presented and strong compressive strain on epitaxial graphene is observed. The results presented here are closely related to the application of graphene on nano-electronic device and help on the better understanding of physical and electronic properties of graphene.
Multiplexed Multi-Color Raman Imaging of Live Cells with Isotopically Modified Single Walled Carbon Nanotubes  [PDF]
Zhuang Liu,Xiaolin Li,Scott M. Tabakman,Kaili Jiang,Shoushan Fan,Hongjie Dai
Physics , 2008,
Abstract: We show that single walled carbon nanotubes with different isotope compositions exhibit distinct Raman Gband peaks and can be used for multiplexed multi-color Raman imaging of biological systems. Cancer cells with specific receptors are selectively labeled with 3 differently colored SWNTs conjugated with various targeting ligands including Herceptin, anti-Her2, Erbitux, anti-Her1, and RGD peptide, allowing for multi-color Raman imaging of cells in a multiplexed manner. SWNT Raman signals are highly robust against photo-bleaching, allowing long term imaging and tracking. With narrow peak features, SWNT Raman signals are easily differentiated from the auto-fluorescence background. The SWNT Raman excitation and scattering photons are in the near-infrared region, which is the most transparent optical window for biological systems in vitro and in vivo. Thus, SWNTs are novel Raman tags promising for multiplexed biological detection and imaging.
Raman Spectroscopic Imaging of the Whole Ciona intestinalis Embryo during Development  [PDF]
Mitsuru J. Nakamura, Kohji Hotta, Kotaro Oka
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0071739
Abstract: Intracellular composition and the distribution of bio-molecules play central roles in the specification of cell fates and morphogenesis during embryogenesis. Consequently, investigation of changes in the expression and distribution of bio-molecules, especially mRNAs and proteins, is an important challenge in developmental biology. Raman spectroscopic imaging, a non-invasive and label-free technique, allows simultaneous imaging of the intracellular composition and distribution of multiple bio-molecules. In this study, we explored the application of Raman spectroscopic imaging in the whole Ciona intestinalis embryo during development. Analysis of Raman spectra scattered from C. intestinalis embryos revealed a number of localized patterns of high Raman intensity within the embryo. Based on the observed distribution of bio-molecules, we succeeded in identifying the location and structure of differentiated muscle and endoderm within the whole embryo, up to the tailbud stage, in a label-free manner. Furthermore, during cell differentiation, we detected significant differences in cell state between muscle/endoderm daughter cells and daughter cells with other fates that had divided from the same mother cells; this was achieved by focusing on the Raman intensity of single Raman bands at 1002 or 1526 cm?1, respectively. This study reports the first application of Raman spectroscopic imaging to the study of identifying and characterizing differentiating tissues in a whole chordate embryo. Our results suggest that Raman spectroscopic imaging is a feasible label-free technique for investigating the developmental process of the whole embryo of C. intestinalis.
The potential of Raman microscopy and Raman imaging in plant research  [PDF]
Notburga Gierlinger,Manfred Schwanninger
Spectroscopy: An International Journal , 2007, DOI: 10.1155/2007/498206
Abstract: To gain a better understanding on structure, chemical composition and properties of plant cells, tissues and organs several microscopic, chemical and physical methods have been applied during the last years. However, a knowledge gap exists about the location, quantity and structural arrangement of molecules in the native sample or what happens on the molecular level when samples are chemically or mechanically treated or how they respond to mechanical stress. These questions need to be answered to optimise utilization of plants in food industry and pharmacy and to understand structure-function relationships of plant cells to learn from natures unique. Advances in combining microscopy with Raman spectroscopy have tackled this problem in a non-invasive way and provide chemical and structural information in situ without any staining or complicated sample preparation. In this review the different Raman techniques (e.g. near infrared Fourier Transform Raman spectroscopy (NIR-FT), resonance Raman spectroscopy, surface-enhanced Raman spectroscopy) are briefly described before approaches in plant science are summarised. Investigations on structural cell wall components, valuable plant substances, metabolites and inorganic substances are included with emphasis on Raman imaging. The introduction of the NIR-FT-Raman technique led to many applications on green plant material by eliminating the problem of sample fluorescence. For mapping and imaging of whole plant organs (seeds, fruits, leaves) the lateral resolution (~10 μm) of the NIR-FT technique is adequate, whereas for investigations on the lower hierarchical level of cells and cell walls the high resolution gained with a visible laser based system is needed. Examples on high resolution Raman imaging are given on wood cells, showing that changes in chemistry and orientation can be followed within and between different cell wall layers having dimensions smaller than 1 μm. In addition imaging the distribution of amorphous silica is shown on horsetail tissue, including an area scan from a cross section as well as a depth profiling within a silica rich knob of the outer stem wall.
Self-imaging silicon Raman amplifier  [PDF]
Varun Raghunathan,Hagen Renner,Robert R. Rice,Bahram Jalali
Physics , 2006, DOI: 10.1364/OE.15.003396
Abstract: We propose a new type of waveguide optical amplifier. The device consists of collinearly propagating pump and amplified Stokes beams with periodic imaging of the Stokes beam due to the Talbot effect. The application of this device as an Image preamplifier for Mid Wave Infrared (MWIR) remote sensing is discussed and its performance is described. Silicon is the preferred material for this application in MWIR due to its excellent transmission properties, high thermal conductivity, high damage threshold and the mature fabrication technology. In these devices, the Raman amplification process also includes four-wave-mixing between various spatial modes of pump and Stokes signals. This phenomenon is unique to nonlinear interactions in multimode waveguides and places a limit on the maximum achievable gain, beyond which the image begins to distort. Another source of image distortion is the preferential amplification of Stokes modes that have the highest overlap with the pump. These effects introduce a tradeoff between the gain and image quality. We show that a possible solution to this trade-off is to restrict the pump into a single higher order waveguide mode.
Quantitative Imaging of Single Upconversion Nanoparticles in Biological Tissue  [PDF]
Annemarie Nadort, Varun K. A. Sreenivasan, Zhen Song, Ekaterina A. Grebenik, Andrei V. Nechaev, Vladimir A. Semchishen, Vladislav Y. Panchenko, Andrei V. Zvyagin
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0063292
Abstract: The unique luminescent properties of new-generation synthetic nanomaterials, upconversion nanoparticles (UCNPs), enabled high-contrast optical biomedical imaging by suppressing the crowded background of biological tissue autofluorescence and evading high tissue absorption. This raised high expectations on the UCNP utilities for intracellular and deep tissue imaging, such as whole animal imaging. At the same time, the critical nonlinear dependence of the UCNP luminescence on the excitation intensity results in dramatic signal reduction at (~1 cm) depth in biological tissue. Here, we report on the experimental and theoretical investigation of this trade-off aiming at the identification of optimal application niches of UCNPs e.g. biological liquids and subsurface tissue layers. As an example of such applications, we report on single UCNP imaging through a layer of hemolyzed blood. To extend this result towards in vivo applications, we quantified the optical properties of single UCNPs and theoretically analyzed the prospects of single-particle detectability in live scattering and absorbing bio-tissue using a human skin model. The model predicts that a single 70-nm UCNP would be detectable at skin depths up to 400 μm, unlike a hardly detectable single fluorescent (fluorescein) dye molecule. UCNP-assisted imaging in the ballistic regime thus allows for excellent applications niches, where high sensitivity is the key requirement.
Coherent Raman spectro-imaging with laser frequency combs  [PDF]
Takuro Ideguchi,Simon Holzner,Birgitta Bernhardt,Guy Guelachvili,Nathalie Picqué,Theodor W. H?nsch
Physics , 2013, DOI: 10.1038/nature12607
Abstract: Optical spectroscopy and imaging of microscopic samples have opened up a wide range of applications throughout the physical, chemical, and biological sciences. High chemical specificity may be achieved by directly interrogating the fundamental or low-lying vibrational energy levels of the compound molecules. Amongst the available prevailing label-free techniques, coherent Raman scattering has the distinguishing features of high spatial resolution down to 200 nm and three-dimensional sectioning. However, combining fast imaging speed and identification of multiple - and possibly unexpected- compounds remains challenging: existing high spectral resolution schemes require long measurement times to achieve broad spectral spans. Here we overcome this difficulty and introduce a novel concept of coherent anti-Stokes Raman scattering (CARS) spectro-imaging with two laser frequency combs. We illustrate the power of our technique with high resolution (4 cm-1) Raman spectra spanning more than 1200 cm-1 recorded within less than 15 microseconds. Furthermore, hyperspectral images combining high spectral (10 cm-1) and spatial (2 micrometers) resolutions are acquired at a rate of 50 pixels per second. Real-time multiplex accessing of hyperspectral images may dramatically expand the range of applications of nonlinear microscopy.

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