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Design and Formation of Composite Particles
Published in Ko Higashitani, Hisao Makino, Shuji Matsusaka, Powder Technology Handbook, 2019
Hideki Ichikawa, Tooru Andoh, Fumihiko Fujii
Two-photon microscopy is one fluorescence imaging technique that can visualize fluorescent-labeled biomolecules and cells several hundred microns deep in various organs.27 In contrast to conventional microscopy, namely one-photon microscopy, the two-photon microscopy equipped pulse laser excites fluorophores by two NIR photons and then detects visible photons from the fluorophores (Figure 4.4.9). The efficiency of two-photon absorption depends on the two-photon absorption cross-section of the fluorophores. The experimental value of the two-photon action cross-section measured for CdSe is several orders of magnitude larger than those of organic dyes and fluorescent proteins.28 Thus, SNCs are useful for not only conventional microscopy but also the two-photon microscopy.
Two-Photon Microscopy of Tissues
Published in Mary-Ann Mycek, Brian W. Pogue, Handbook of Biomedical Fluorescence, 2003
Peter T. C. So, Ki H. Kim, Lily Hsu, Peter Kaplan, Tom Hacewicz, Chen Y. Dong, Urs Greuter, Nick Schlumpf, Christof Buehler
Two-photon microscopy provides an unprecedented opportunity for in vivo study of neuronal interactions. Two-photon microscopy provide 3-D mapping of neuron organization and assays neuron communications by monitoring action potentials, calcium waves, and neural transmitters. Many two-photon neural biology studies have focused on the remodeling of neuronal dendritic spines and the subsequent effects these changes have on memory and learning, or on the dynamics of calcium signal propagation [51–53]. Other studies focus on system level interactions of neurons [54–56]. Two-photon imaging also contributes to the study of neuronal hemodynamics. Denk et al. used a two-photon microscope to probe red blood cell motion in rat cortical capillaries through 600-μm-thick tissue. In some cases, they were able to detect flow changes in response to externally applied stimuli, such as vibrassa, direct touch, or moderate shock [57]. Another emerging application of two-photon microscopy is for in vivo study of neural pathology. Hyman and coworkers applied this technology to study the formation of β-amyloid plaques associated with Alzheimer’s disease [58,59].
Functional Imaging with Light-Sheet Microscopy
Published in Francesco S. Pavone, Shy Shoham, Handbook of Neurophotonics, 2020
Raghav K. Chhetri, Philipp J. Keller
Recording the activity from a population of neurons demands much higher acquisition speeds than the majority of dynamical processes encountered in developmental imaging. Various high-speed optical imaging modalities, such as two-photon point-scanning microscopy, two-photon random access microscopy, and light-field microscopy among others, aim to meet the demands of high spatiotemporal resolution in neuronal imaging, and each offer distinct advantages and utility. Two-photon microscopy, which confines fluorescence excitation to the illumination focus, excels at imaging inside scattering tissues and captures images with high spatial resolution at depths inaccessible to conventional single-photon techniques. However, two-photon point scanning microscopy requires the excitation spot to be sampled sequentially across the entire imaging volume, which limits the overall volumetric acquisition speed. In sparsely labeled samples, the speed bottleneck of two-photon imaging is overcome by two-photon random access microscopy, which samples a limited number of spots distributed across a large sample volume, thereby increasing the temporal rate at which the regions of interest are sampled (Grewe et al., 2010; Sofroniew et al., 2016). Light field microscopy, in which the spatial and angular distributions of the emitted fluorescent light are captured simultaneously using a microlens array positioned conjugate to the image plane, acquires volumetric information from the entire sample volume onto a single camera chip and thus offers exceptionally high volumetric acquisition speed (Levoy et al., 2006; Prevedel et al., 2014). However, the compression of the entire light-field onto a single two-dimensional sensor reduces the spatial resolution across the acquired volume, which often constrains the interrogation of neuronal activities to a local group of neurons instead of single neurons. Compared to these complementary high-speed neuroimaging techniques, light-sheet microscopy offers a unique approach for large-scale in vivo recording of neural activity in transparent and small non-transparent samples at high spatiotemporal resolution and over an extended period of time.
Aptamerized silica/gold nanocapsules for stimulated release of doxorubicin through remote two-photon excitation
Published in International Journal of Smart and Nano Materials, 2022
Lih Shin Tew, Tsung-Hsi Lee, Leu-Wei Lo, Yit Lung Khung, Nai-Tzu Chen
To evaluate the photostability of the GNS nanoconstruct, a custom built NIR laser scanning two-photon microscopy was utilized (Integrated Stem Cell Center, China Medical University Hospital). First, 50 µL of GNS was carefully aliquoted and sealed between two glass slides, and the sample was then exposed to two-photon irradiation (TPE at 800 nm) for few seconds. After that, the sample was collected and analyzed with ultraviolet-visible (UV-Vis) spectroscopy.