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Raman profile alterations of irradiated human nasopharyngeal cancer cells detected with laser tweezer Raman spectroscopy
摘要： Radiotherapy has been widely used for nasopharyngeal carcinoma (NPC) treatment, which causes DNA damage and alterations of macromolecules of cancer cells. However, the Raman profile alterations of irradiated NPC cells remain unclear. In the present study, we used laser tweezers Raman spectroscopy (LTRS) to monitor internal structural changes and chemical modifications in NPC cells after exposure at a clinical dose (2.3 Gy) to X-ray irradiation (IR) at a single-cell level. Two types of NPC cell lines, CNE2 (EBV-negative cell line) and C666-1 (EBV-positive cell line), were used. The Raman spectra of cells before and after radiation treatment were recorded by LTRS. The analysis of spectral differences indicated that the IR caused Raman profile alterations of intracellular proteins, DNA base and lipids. Moreover, by using the multivariate statistical analysis including principal component analysis (PCA) and linear discriminant analysis (LDA) algorithm, an accuracy of 90.0% for classification between CNE2 cells before and after IR could be achieved, which was 10% better than that of C666-1 cells. The results demonstrated that CNE2 cells were more sensitive to IR in comparison to C666-1 cells, providing useful information for creating a treatment strategy in clinical practice. This exploratory study suggested that LTRS combined with multivariate statistical analysis would be a novel and effective tool for evaluating the radiotherapeutic effect on tumor cells, and for detection of the corresponding alterations at the molecular level.
关键词： laser tweezers,multivariate statistical analysis,nasopharyngeal carcinoma,radiotherapy,Raman spectroscopy
更新于2025-09-19 17:13:59
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Direct measurement of electrostatic interactions between poly(methyl methacrylate) microspheres with optical laser tweezers
摘要： In this study, we measured the force of electrostatic interactions between poly(methyl methacrylate) (PMMA) particles dispersed in organic solvent mixtures of cyclohexyl bromide (CHB) and n-decane. Optical laser tweezers were employed to directly measure interactive forces between paired PMMA particles in a CHB medium that contained n-decane in various volume ratios. CHB, having a moderate dielectric constant, provided an environment with a high charge storage capacity. The addition of n-decane lowered the effective refractive index of the medium, which increased the optical trapping efficiency. We also fabricated microscope flow cells with a commonly used UV-curable adhesive and quantified the effects of dissolved adhesive compounds through interactive force measurements and nuclear magnetic resonance analysis. In addition, we studied the impact of CHB dissociation into H+ and Br? ions, which could screen electrostatic interactions.
关键词： UV-curable adhesive,NMR analysis,electrostatic interactions,optical laser tweezers,CHB,PMMA particles,n-decane
更新于2025-09-16 10:30:52
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Light Pressure on an Inhomogeneous Spherical Particle in the Field of Laser Tweezers
摘要： The light pressure on an inhomogeneous spherical dielectric particle consisting of a shell and a core with different refractive indices is considered. The forces acting on this particle in a laser beam with a Gaussian intensity profile have been found in the geometrical optics approximation. The radiation propagation is analyzed by taking into account the different refractive indices of the core, the shell, and the medium surrounding the particle. The light pressure is shown to depend significantly on the core radius, which allows the core size to be estimated from the spatial dynamics of the particle in the field of optical tweezers.
关键词： laser tweezers,refractive indices,inhomogeneous spherical particle,geometrical optics approximation,light pressure
更新于2025-09-16 10:30:52
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Enhancing Double-Beam Laser Tweezers Raman Spectroscopy (LTRS) for the Photochemical Study of Individual Airborne Microdroplets
摘要： A new device and methodology for vertically coupling confocal Raman microscopy with optical tweezers for the in situ physico- and photochemical studies of individual microdroplets (? ≤ 10 μm) levitated in air is presented. The coupling expands the spectrum of studies performed with individual particles using laser tweezers Raman spectroscopy (LTRS) to photochemical processes and spatially resolved Raman microspectroscopy on airborne aerosols. This is the first study to demonstrate photochemical studies and Raman mapping on optically levitated droplets. By using this configuration, photochemical reactions in aerosols of atmospheric interest can be studied on a laboratory scale under realistic conditions of gas-phase composition and relative humidity. Likewise, the distribution of photoproducts within the drop can also be observed with this setup. The applicability of the coupling system was tested by studying the photochemical behavior of microdroplets (5 μm < ? < 8 μm) containing an aqueous solution of sodium nitrate levitated in air and exposed to narrowed UV radiation (254 ± 25 nm). Photolysis of the levitated NaNO3 microdroplets presented photochemical kinetic differences in comparison with larger NaNO3 droplets (40 μm < ? < 80 μm), previously photolyzed using acoustic traps, and heterogeneity in the distribution of the photoproducts within the drop.
关键词： optical levitation,optical traps,photochemical reactions in Earth’s atmosphere,atmospheric aerosols,laser tweezers Raman spectroscopy (LTRS)
更新于2025-09-12 10:27:22