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Use of Microcomputed Tomography and Image Processing Tools in Medicinal and Aromatic Plants
Published in Amit Baran Sharangi, K. V. Peter, Medicinal Plants, 2023
Yogini S. Jaiswal, Yanling Xue, Tiqiao Xiao, Leonard L. Williams
There are several types of Synchrotron techniques available for imaging which include: (1) synchrotron radiation-Fourier transforms infrared (SR-FTIR) spectroscopy; (2) X-ray absorption spectroscopy (XAS); (3) X-ray micro fluorescence (μ-XRF) and X-ray computed tomography and phase-contrast imaging. With use of Synchrotron Radiation-Fourier Trans-form Infrared (SR-FTIR) Spectroscopy, research can identify and quantitate plant constituents within tissues and cells (Goff et al., 2013). The transmission or fluorescence of samples can be recorded by XAS. In an extended fine structure absorption spectrum, the generated spectrum can be used for quantification of absorption by atoms of various species and distances. Thus, this technique finds its application in studying uptake and distribution of nutrients in plants (Kopittke et al., 2012, 2014; Sarret et al., 2013). μ-XRF is used to study the uptake of metals within different plant tissues. X-ray computed tomography and Phase Contrast Imaging techniques scan samples and generate images of virtual slices of the samples with millisecond intervals (Moore et al., 2010). Integration of these SR techniques with other analysis techniques helps in the exploration of biological systems.
Enzymes
Published in Stephen W. Carmichael, Susan L. Stoddard, The Adrenal Medulla 1986 - 1988, 2017
Stephen W. Carmichael, Susan L. Stoddard
Scott, Sullivan, DeWolf et al. (1988) reported the results of x-ray absorption spectroscopy experiments on highly concentrated samples of the cupric and cuprous oxidation states of bovine DβH with a 2:1 coppenunit stoichiometry. A significant change in the structure of the copper sites was occurred upon ascorbate-mediated reduction of cupric DβH to the cuprous form. Because the cupric form of the enzyme is inactive and may not be physiologically important, the data of Scott et al. (1988) indicate that a major structural rearrangement of the copper-containing active sites may be responsible for the reductive activation of DβH.
Structural Studies of Copper Proteins Using X-Ray Absorption Spectroscopy
Published in René Lontie, Copper Proteins and Copper Enzymes, 1984
X-ray absorption spectroscopy (XAS) is a technique that reveals local atomic structure of materials of all types, from heterogeneous catalysts to biological macromolecules.1–5 As early as the 1930s, Kronig6 had observed that the absorption cross-section in the X-ray region had complex oscillations as a function of energy which extended several hundred electron volts above the absorption threshold. Many attempts were subsequently made to present an adequate theory to explain such structure. In 1970, Sayers et al.7 presented a derivation using a short-range single-electron single-scattering theory that successfully interpreted experimental data collected on a copper foil with a conventional X-ray source. However, the intensity of the X-ray source (Bremsstrahlung radiation produced by a conventional X-ray tube) was not sufficient to accumulate data within a reasonable time for systems with low metal concentrations. The application of the technique to studies on metalloproteins and metalloenzymes was not possible until 1974, when synchrotron radiation became available at the Stanford Positron Electron Accelerating Ring (SPEAR)8 and provided a stable, highly collimated, high flux X-ray source. Since then, several more synchrotron storage rings have been built.9 The increase in flux from a storage ring of approximately 104 to 106 compared to a rotating anode X-ray tube allows systems of low metal content in metalloproteins and metalloenzymes to be studied using the technique.
X-ray spectrometry imaging and chemical speciation assisting to understand the toxic effects of copper oxide nanoparticles on zebrafish (Danio rerio)
Published in Nanotoxicology, 2022
Joyce Ribeiro Santos-Rasera, Rafael Giovanini de Lima, Dejane Santos Alves, Regina Teresa Rosim Monteiro, Hudson Wallace Pereira de Carvalho
Spectroscopic techniques, such as X-ray fluorescence spectroscopy (XRF) is able to identify, locate and quantify chemical elements, while X-ray absorption spectroscopy (XAS) can reveal their chemical environment, oxidation state, and symmetry. Although powerful, these techniques are not as spread in ecotoxicology as in materials science. Some of the challenges regard strategies for mapping whole organisms and detecting trace elements, this latter task has been mostly accomplished by acid digestion and the destruction of biological tissues, without actually taking a picture of the organisms (Wang 2022). Sample preparation is also challenging because it has to preserve the elements in the proper cell compartment, otherwise one may obtain misleading results. (Jin et al., 2017). The literature reports applications of isolated XRF (Mages et al. 2008) and XAS in aquatic organisms (Beauchemin et al. 2004; Misra et al. 2012; Saibu et al. 2018; Kuwabara et al. 2007). Fewer studies have combined both tools such as reported by Adams et al. (2016) and Santos-Rasera et al. (2019).
Emerging theranostics to combat cancer: a perspective on metal-based nanomaterials
Published in Drug Development and Industrial Pharmacy, 2022
Tejas Girish Agnihotri, Shyam Sudhakar Gomte, Aakanchha Jain
Metal-organic frameworks (MOFs) are porous coordination polymers, which have been self-assembled from ligand molecules. They have been the subject of attraction due to their high porosity, large surface area, thermostability, and ability to functionalize with different drugs or moieties. They are quite useful in the treatment of cancer because of their remarkable properties including the high binding ability to cancer cells eliciting targeted therapy, drug delivery in terms of pH stimuli, and photosensitization. There have been several methods of synthesis of MOFs such as microwave-based synthesis, solvothermal synthesis, vapor deposition synthesis, solvent-free synthesis, and electrosynthesis. The characterization methods comprise of morphological evaluation by scanning electron microscopy and atomic force microscopy, X-ray diffraction technique, and X-ray absorption spectroscopy to characterize the crystalline structure of MOFs [120]. MOFs have been widely employed in detecting biomarkers for cancer because of their distinctive features. Lanthanides are suitable candidates for functionalization with MOFs by virtue of their luminescence emission in the visible region [121]. Photodynamic therapy (PDT), one of the treatment modalities in cancer makes use of photosensitizers that are dependent on oxygen, however; on the contrary, the tumor microenvironment is in hypoxic condition making PDT ineffective. To overcome this challenge, scientists have come up with hypoxia-activated prodrugs in combination with PDT. Liu et al. [122] formulated Hf-TCPP nanoscale MOFs by solvothermal method with porphyrin being a photosensitizer agent. Tirapazamine, a prodrug was attached to Hf-TCPP MOF and further functionalized with polymer, DOPA-PIMA-PEG to make stable and controlled release delivery. Due to the higher content of porphyrin in NPs, the formulated system was able to produce a higher level of ROS, which enabled it to cytotoxic to tumor cells upon administration. MOFs have also been utilized in PTT. Indocyanine green, a photoactive dye that has been approved by US-FDA suffers from some limitations like low solubility profile, low responsiveness to theranostics, and low targeting ability to cancerous cells. To overcome these problems, Cai et al. [123] designed MOF based on hyaluronic acid–iron NPs with the incorporation of indocyanine green. The research findings showed that more than 40% of dye was loaded in MOF with high uptake into MCF-7 cells. The targeting ability of developed MOF-based NPs was also proved based on tumor xenograft models establishing a good platform for cancer imaging and therapeutic applications in cancer.