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19 pages, 6209 KB

Open AccessArticle

Nonlinear Optical Materials: Predicting the First-Order Molecular Hyperpolarizability of Organic Molecular Structures

by Francisco A. Santos, Carlos E. R. Cardoso, José J. Rodrigues, Leonardo De Boni and Luis M. G. Abegão

Photonics 2023, 10(5), 545; https://doi.org/10.3390/photonics10050545 - 8 May 2023

Cited by 28 | Viewed by 4725

Abstract

Experimental nonlinear optics (NLO) is usually expensive due to the high-end photonics and electronic devices needed to perform experiments such as incoherent second harmonic generation in liquid phase, multi-photon absorption, and excitation. Nevertheless, exploring NLO responses of organic and inorganic compounds has already opened a world of new possibilities. For example, NLO switches, NLO frequency converters, and a new way to obtain biological images through the incoherent second harmonic generation (SHG) originate from first-order molecular hyperpolarizability (β). The microscopic effect of the coherent or incoherent SHG is, in fact, the β. Therefore, estimating β without using expensive photonic facilities will optimize time- and cost-efficiency to predict if a specific molecular structure can generate light with double its incident frequency. In this work, we have simulated the β values of 27 organic compounds applying density functional theory (PBE0, TPSSh, wB97XD, B3LYP, CAM-B3LYP, and M06-2X) and Hartree–Fock methods using the Gaussian software package. The predicted β was compared with the experimental analogs obtained by the well-known Hyper–Rayleigh Scattering (HRS) technique. The most reliable functionals were CAM-B3LYP and M06-2X, with an unsigned average error of around 25%. Moreover, we have developed post-processing software—Hyper-QCC, providing an effortless, fast, and reliable way to analyze the Gaussian output files. Full article

(This article belongs to the Special Issue Novel Photonic Devices and Techniques)

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9 pages, 1969 KB

Open AccessCommunication

High-Resolution Phosphorescence Lifetime Imaging (PLIM) of Bones

by Hans Georg Breunig and Karsten König

Appl. Sci. 2022, 12(3), 1066; https://doi.org/10.3390/app12031066 - 20 Jan 2022

Cited by 5 | Viewed by 2502

Abstract

For the first time, the time-resolved two-photon excited autophosphorescence of non-labeled biological specimens was investigated by phosphoresce lifetime imaging with microscopic spatial resolution. A modified multiphoton tomograph was employed to record both photoluminescence contributions, autofluorescence and autophosphorescence, simultaneously, induced by two-photon excitation using an 80 MHz near infrared femtosecond-pulse-laser scanning beam, an acousto-optic modulator, and a time-correlated single-photon counting module for lifetime measurements from the picosecond to the microsecond range. In particular, the two-photon-excited luminescence of thermally altered bones was imaged. A strong dependence of the phosphorescence intensity on exposure temperature, with a maximum emission for an exposure temperature of approximately 600 °C was observed. Furthermore, the phosphorescence lifetime data indicated a bi-exponential signal decay with both a faster few µs decay time in the range of 3–10 µs and a slower one in the range of 30–60 µs. The recording of fluorescence and phosphorescence allowed deriving the relative signal proportion as an unbiased measure of the temperature dependence. The measurements on thermally altered bones are of particular interest for application to forensic and archeological investigations. Full article

(This article belongs to the Special Issue Finite Element Modeling of Joint)

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14 pages, 5554 KB

Open AccessArticle

Hyperdimensional Imaging Contrast Using an Optical Fiber

by Jenu V. Chacko, Han Nim Lee, Wenxin Wu, Marisa S. Otegui and Kevin W. Eliceiri

Sensors 2021, 21(4), 1201; https://doi.org/10.3390/s21041201 - 9 Feb 2021

Cited by 3 | Viewed by 3414

Abstract

Fluorescence properties of a molecule can be used to study the structural and functional nature of biological processes. Physical properties, including fluorescence lifetime, emission spectrum, emission polarization, and others, help researchers probe a molecule, produce desired effects, and infer causes and consequences. Correlative imaging techniques such as hyperdimensional imaging microscopy (HDIM) combine the physical properties and biochemical states of a fluorophore. Here we present a fiber-based imaging system that can generate hyper-dimensional contrast by combining multiple fluorescence properties into a single fluorescence lifetime decay curve. Fluorescence lifetime imaging microscopy (FLIM) with controlled excitation polarization and temporally dispersed emission can generate a spectrally coded, polarization-filtered lifetime distribution for a pixel. This HDIM scheme generates a better contrast between different molecules than that from individual techniques. This setup uses only a single detector and is simpler to implement, modular, cost-efficient, and adaptable to any existing FLIM microscope. We present higher contrast data from Arabidopsis thaliana epidermal cells based on intrinsic anthocyanin emission properties under multiphoton excitation. This work lays the foundation for an alternative hyperdimensional imaging system and demonstrates that contrast-based imaging is useful to study cellular heterogeneity in biological samples. Full article

(This article belongs to the Special Issue Sensors in Fluorescence Imaging)

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15 pages, 5464 KB

Open AccessArticle

Evaluation of Injured Axons Using Two-Photon Excited Fluorescence Microscopy after Spinal Cord Contusion Injury in YFP-H Line Mice

by Hideki Horiuchi, Yusuke Oshima, Tadanori Ogata, Tadao Morino, Seiji Matsuda, Hiromasa Miura and Takeshi Imamura

Int. J. Mol. Sci. 2015, 16(7), 15785-15799; https://doi.org/10.3390/ijms160715785 - 13 Jul 2015

Cited by 15 | Viewed by 7779

Abstract

Elucidation of the process of degeneration of injured axons is important for the development of therapeutic modules for the treatment of spinal cord injuries. The aim of this study was to establish a method for time-lapse observation of injured axons in living animals after spinal cord contusion injury. YFP (yellow fluorescent protein)-H transgenic mice, which we used in this study, express fluorescence in their nerve fibers. Contusion damage to the spinal cord at the 11th vertebra was performed by IH (Infinite Horizon) impactor, which applied a pressure of 50 kdyn. The damaged spinal cords were re-exposed during the observation period under anesthesia, and then observed by two-photon excited fluorescence microscopy, which can observe deep regions of tissues including spinal cord axons. No significant morphological change of injured axons was observed immediately after injury. Three days after injury, the number of axons decreased, and residual axons were fragmented. Seven days after injury, only fragments were present in the damaged tissue. No hind-limb movement was observed during the observation period after injury. Despite the immediate paresis of hind-limbs following the contusion injury, the morphological degeneration of injured axons was delayed. This method may help clarification of pathophysiology of axon degeneration and development of therapeutic modules for the treatment of spinal cord injury. Full article

(This article belongs to the Special Issue Neurological Injuries’ Monitoring, Tracking and Treatment)

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16 pages, 489 KB

Open AccessArticle

Development and Experimental Testing of an Optical Micro-Spectroscopic Technique Incorporating True Line-Scan Excitation

by Gabriel Biener, Michael R. Stoneman, Gheorghe Acbas, Jessica D. Holz, Marianna Orlova, Liudmila Komarova, Sergei Kuchin and Valerică Raicu

Int. J. Mol. Sci. 2014, 15(1), 261-276; https://doi.org/10.3390/ijms15010261 - 27 Dec 2013

Cited by 54 | Viewed by 8509

Abstract

Multiphoton micro-spectroscopy, employing diffraction optics and electron-multiplying CCD (EMCCD) cameras, is a suitable method for determining protein complex stoichiometry, quaternary structure, and spatial distribution in living cells using Förster resonance energy transfer (FRET) imaging. The method provides highly resolved spectra of molecules or molecular complexes at each image pixel, and it does so on a timescale shorter than that of molecular diffusion, which scrambles the spectral information. Acquisition of an entire spectrally resolved image, however, is slower than that of broad-bandwidth microscopes because it takes longer times to collect the same number of photons at each emission wavelength as in a broad bandwidth. Here, we demonstrate an optical micro-spectroscopic scheme that employs a laser beam shaped into a line to excite in parallel multiple sample voxels. The method presents dramatically increased sensitivity and/or acquisition speed and, at the same time, has excellent spatial and spectral resolution, similar to point-scan configurations. When applied to FRET imaging using an oligomeric FRET construct expressed in living cells and consisting of a FRET acceptor linked to three donors, the technique based on line-shaped excitation provides higher accuracy compared to the point-scan approach, and it reduces artifacts caused by photobleaching and other undesired photophysical effects. Full article

(This article belongs to the Special Issue Frontiers of Micro-Spectroscopy in Biological Applications)

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11 pages, 754 KB

Open AccessArticle

Simultaneous Measurement of Neural Spike Recordings and Multi-Photon Calcium Imaging in Neuroblastoma Cells

by Suhwan Kim, Unsang Jung, Juyeong Baek, Shinwon Kang and Jeehyun Kim

Sensors 2012, 12(11), 15281-15291; https://doi.org/10.3390/s121115281 - 8 Nov 2012

Cited by 4 | Viewed by 6855

Abstract

This paper proposes the design and implementation of a micro-electrode array (MEA) for neuroblastoma cell culturing. It also explains the implementation of a multi-photon microscope (MPM) customized for neuroblastoma cell excitation and imaging under ambient light. Electrical signal and fluorescence images were simultaneously acquired from the neuroblastoma cells on the MEA. MPM calcium images of the cultured neuroblastoma cell on the MEA are presented and also the neural activity was acquired through the MEA recording. A calcium green-1 (CG-1) dextran conjugate of 10,000 D molecular weight was used in this experiment for calcium imaging. This study also evaluated the calcium oscillations and neural spike recording of neuroblastoma cells in an epileptic condition. Based on our observation of neural spikes in neuroblastoma cells with our proposed imaging modality, we report that neuroblastoma cells can be an important model for epileptic activity studies. Full article

(This article belongs to the Special Issue Medical & Biological Imaging)

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