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Optical Nanoprobes for Diagnosis
Published in D. Sakthi Kumar, Aswathy Ravindran Girija, Bionanotechnology in Cancer, 2023
R. G. Aswathy, D. Sakthi Kumar
Wide applications of the optical imaging are limited due to autofluorescence, scattering of light, absorption by tissues, water, and lipids, and reduced penetration (normally 1 cm), etc. These limitations are circumvented by some of the advanced techniques in fluorescence, bioluminescence, diffused optical, and optical coherence tomography (OCT). Specifically, near-infrared fluorescent (NIRF) imaging is currently extensively used for in vivo imaging.
Cutaneous Photosensitization
Published in David W. Hobson, Dermal and Ocular Toxicology, 2020
Another in vitro cell culture technique involves the induction of SV40 tumor virus by photoreactive chemicals of SV40-transformed cells with photosensitizer and light.32,33 Monolayers of clone E cells are treated with different concentrations of photosensitizer, irradiated with glass-filtered light from fluorescent lamps, and incubated 3 days for virus expression. The amount of SV40 induced is determined by measurement of the SV40 infectivity of cell extracts in permissive CV-1 monkey kidney cells. Both cell-culture testing systems have the disadvantage of requiring virology laboratory experience and facilities. In addition, differences between responses of virus-infected cells and normal cells to PS may exist and limited validation of the tests have been made with known phototoxic compounds. Neither is it known whether the systems would react to treatments causing primarily cell membrane damage. For screening purposes, it is important to use several different concentrations of chemical, light exposure times, and wavelengths. The light absorption spectrum for each compound is useful in selection of the appropriate wavelengths of light for irradiation.
Signs of Pressure Sores
Published in J G Webster, Prevention of Pressure Sores, 2019
The basic principle of photoplethysmography is the modulation of reflection, transmission, and absorption properties of light as a result of volume changes. A light source and a photosensitive detector are arranged so that the detector can measure the intensity of light reflected from or transmitted through a capillary bed (figure 3.11). Blood has a light absorption coefficient that is higher than that of surrounding tissue, thus an increase in the amount of blood causes a corresponding decrease in the intensity of light detected. Photoplethysmography does not provide accurate volume measurements because the signal detected is very small. Furthermore, it is very sensitive to motion.
Comparison and convergence of compartment syndrome techniques: a narrative review
Published in Expert Review of Medical Devices, 2023
Naveen Sharma, Nitin Mohan Sharma, Apurva Sharma, Sarfaraj Mirza
NIRS is a noninvasive optical technique used to measure the oxygen saturation level (StO2) of the tissues by making use of near-infrared radiation (ranging from 700–1200 nm) [42]. It is capable of measuring the oxygen level of tissues, approximately 2–3 cm below the deep skin surface in a noninvasive and continuous manner [43]. Nevertheless, the distance between the light source and the tissue determines the depth of penetration [44]. The basic principle of this technology is the light absorption and transmission properties of molecules present under the skin and subcutaneous tissue, for instance, hemoglobin. As the proportion of light absorbed by these molecules varies with degree of hemoglobin binding with oxygen, NIRS can detect subtle changes in oxygenated and deoxygenated hemoglobin concentrations in tissues.
Structural and haemodynamic properties of ocular vasculature in axial myopia
Published in Clinical and Experimental Optometry, 2022
Mei Zhao, Andrew KC Lam, Allen MY Cheong
Oxygen saturation of retinal vessels can be estimated by comparing the light absorption of oxygenised and deoxygenated haemoglobin. A decreased arterial saturation and an unchanged venous saturation with increasing axial length have been commonly reported in previous studies,88,94,95 while the alteration of oxygen consumption (i.e. difference between arterial and venous saturation) remains uncertain. Zheng et al.88 found lower oxygen consumption in highly myopic eyes, while Heitmar94 and Lim et al.95 reported that it was not affected by axial elongation. Decrease oxygen saturation does not necessarily mean reduced blood supply. It may be caused by increased oxygen transportation between central retinal vessels or be just an uncorrected measurement error.88
Molecular Diagnostic Tools for the Detection of SARS-CoV-2
Published in International Reviews of Immunology, 2021
Manali Datta, Desh Deepak Singh, Afsar R. Naqvi
Optical biosensors utilize light to monitor interaction (binding or a reaction) between a probe and an analyte by determining changes in light absorption post-interaction. Label-free optical sensor may percept the change in refractive index and thus confirm binding of the analyte–probe molecule. Alternatively, optical sensors can utilize fluorescent tags that have the capability to produce or quench a signal upon interaction between analyte and probe. Gravimetric biosensors use the basic principle of a response to detect change in mass due to binding between probe and analyte. Acoustic-based gravimetric sensors perceive the alteration in resonating frequency corresponding to the binding of the analyte and probe and thus the increase in mass of the bimolecular complex. Electrochemical sensors detect the change in electron flow between interacting molecules and represent it as resultant change in electric current [41]. An interaction between two biological macromolecules often results in the flux of electrons. Leveraging electron level changes may reveal molecular interactions, which thereafter may be assessed quantitatively or semi-quantitatively. Various interacting partners like DNA–DNA, DNA–RNA, DNA–protein, and protein–ligand have been envisaged for designing electrochemical biosensors as in vitro diagnostics.