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Near-Infrared Phosphors with Persistent Luminescence over 1000 nm for Optical Imaging
Published in Ru-Shi Liu, Xiao-Jun Wang, Phosphor Handbook, 2022
Jian Xu, Michele Back, Setsuhisa Tanabe
Optical imagings through pork tissues with 1-cm thickness by the in situ 660 nm photostimulation under the similar experimental condition as presented in Figure 11.15(b) and (c) are also given in Figure 11.15(f) and (g) monitored by commercial Si and InGaAs cameras, respectively. The ceramic sample is firstly charged by 254 nm light for 10 min before covering by the raw-pork tissue, then after natural decay for 20 min (first cycle), it is in situ photostimulated by 660 nm LED for 1 min followed by another 20-min natural decay (second cycle), etc. Because of the enhanced PersL by photostimulation, both Cr3+ and Er3+ emission can be monitored over 104 min and the SNR of Cr3+ PersL at 104 min after ceasing the initial UV excitation can reach ∼31 thanks to this unique autofluorescence-free imaging technology. Moreover, compared with the Cr3+ emission, the Er3+ emission can achieve higher spatial resolution and more accurate signal localizations owing to the reduced light scattering at longer wavelengths, as expected from the light-matter interaction theory. This proof-of-concept using the “photostimulation-induced trap redistribution” approach gives a vivid example of PersL recovery via post-charging of low-energy photostimulation light, which is particularly important to acquire long-term PersL for in vivo optical imaging.
Biomedical Applications of Pullulan
Published in Shakeel Ahmed, Aisverya Soundararajan, Pullulan, 2020
J. Hemapriya, Ashwini Ravi, Aisverya Soundararajan, P.N. Sudha, S. Vijayanand
Nanogels have been extensively used in drug- and gene-delivery systems since they can trap biomolecules, respond to external stimulus, and form macrogels in nanogel network[39, 60, 100]. These nanogels are usually prepared by synthetic methods of microemulsion, precipitation, polymerization, and intramolecular crosslinking of single-chain macromolecules[5, 31, 43, 47]. Nanogels, when conjugated with short-chain fatty acids, can bind with proteins as a host and are used as drug carriers. In addition, they can also be utilized as molecular chaperones. Since pullulan is a compatible biomolecule and forms hydrogels, it is often conjugated with nanogels to be used as molecular chaperones. Cholesterol-bearing pullulan has been extensively used as molecular chaperones for the refolding of citrate synthase[50, 85]. A study on pullulan in the thermal stabilization of horseradish peroxidase proved that pullulan can be utilized to thermally stabilize some unstable proteins[86]. In a study by Hirakura et al., spiropyrane-induced pullulan nanogels were found to have the ability to control protein folding on photostimulation[37]. Along with 2-methacryloyloxyethyl phosphorylcholine and crosslinked haluronan, pullulan is used as molecular chaperone insulin, carbonic anhydrase B and Peptide 1, erythropoietin, insulin, respectively[38, 65, 66]. Cholesterol-bearing pullulan nanogels were also found efficient in the refolding of heat-denatured enzyme carbonic anhydrase along with β cyclodextrin[2].
Optogenetic Modulation of Neural Circuits
Published in Francesco S. Pavone, Shy Shoham, Handbook of Neurophotonics, 2020
Mathias Mahn, Oded Klavir, Ofer Yizhar
The development of red-shifted rhodopsins was motivated by several potential applications. These include improved tissue penetration (see Section 11.4.2 Optical Properties of Brain Tissue) and multiplexed photostimulation of two or more neuronal populations (Yizhar et al., 2011c; Prigge et al., 2012; Klapoetke et al., 2014). VChR1, a red-shifted cation channel from the alga Volvox carteri (Zhang et al., 2008) was first used as a basis for engineering of the high-efficiency red-shifted channelrhodopsin variants C1V1 and ReaChR (Yizhar et al., 2011c; Lin et al., 2013) that allow excitation of neurons with red-shifted light. ChRimson (Klapoetke et al., 2014), a naturally occurring ChR variant isolated from Chlamydomonas noctigama, shows the most red-shifted action spectrum, with peak absorption at ~590 nm, while the chimeric opsins C1V1 and ReaChR both maximally absorb at ~540 nm. Another important application of red-shifted channelrhodopsins is the combination of optogenetic modulation with activity reporter imaging. Using single photon whole field excitation, this can be achieved by using a green fluorescent indicator in combination with a red light sensitive opsin (Akerboom et al., 2013; Chen et al., 2013), or vice versa (Hochbaum et al., 2014; Dana et al., 2016).
Near-infrared light for on-demand drug delivery
Published in Journal of Biomaterials Science, Polymer Edition, 2018
Photodynamic therapy (PDT) is another promising non-invasive strategy involving the use of photosensitizer (PS) drugs capable to being stimulated with external light sources of specific wavelengths for the treatment of specific diseases [30]. The general mechanism for PDT involves the photostimulation of PS drugs, creating a subsequent energy transfer to oxygen molecules or other substances in the surrounding environment, creating cytotoxic reactive oxygen species capable of inducing necrotic or apoptotic cell death. Photosensitizers used for PDT generate ROS through one of two different types of reactions, known as Type I, and Type II, respectively [31,32]. Type I reactions involve the transfer of an electron or hydrogen atom to a substrate to generate ROS while Type II reactions involve the excitation of ground state 3O2 in order to form the reactive state of oxygen known as singlet oxygen 1O2. In both of these cases, the generation of ROS causes permanent damage to the local tissue/cells. PS drugs, and their carriers, have been developed using a wide array of materials and configurations both organic and inorganic in structure. For example, a commonly used PS drug, known as 5-Aminolevulinic acid (ALA), a precursor of phototoxic photoporphyrin IX (pPIX), was encapsulated within a dipalmitoyl-phosphaidyl choline based lipsome, subsequently increasing their uptake efficiency within a human cholangiocarcinoma HuCC-T1 cell line relative to ALA alone, thus increasing its cytotoxic effect [33]. Other potential carriers for PS drugs include polymeric materials such as PLGA [34,35], and polyethylene glycol (PEG) [36,37] which can either encapsulate, or be conjugated to PS drugs such as PpIX or Ce6 [38–40]. Carbon nanomaterials including single-walled carbon nanotubes (SWNTs) and graphene oxide (GO) have been used either as carriers for other PS drugs or occasionally used as PS drugs themselves [41–43]. Notable inorganic materials used for the purpose of PDT include gold nanoparticles [44–46], organically modified silica [47–50], and quantum dots [51–53].
Effect of physicochemical factors on extracellular fungal pigment-mediated biofabrication of silver nanoparticles
Published in Green Chemistry Letters and Reviews, 2022
Sharad Bhatnagar, Christiana N. Ogbonna, James C. Ogbonna, Hideki Aoyagi
Earlier studies have shown that the presence of light affects the final NP product. Popov et al. (52) reported that photostimulation during NP synthesis changed the size and shape of the final product, and this effect was dependent on the light source used and the method employed for initial reduction and stabilization prior to irradiation. More recently, Shabnam et al. (53) demonstrated that chloroplasts/thylakoids isolated from the leaves of Spinacea oleracea could produce AgNPs in the presence of light but with limited synthesis in dark conditions. Moreover, they showed that this generation was also dependent on light intensity as well as on the duration of exposure. Bao et al. (54) used the cell extract of the Neochloris oleoabundans microalga with 5,000 lux of fluorescent light for AgNP synthesis, showing the possibility of AgNPs biosynthesis under white, blue, or purple light illumination, whereas there was no product formation under orange or red light, as well as in the dark. Another study demonstrated a change in the toxicity of AgNPs against Tetrahymena pyriformis in the presence of light; illumination at 12,000 lux for 24 h decreased the toxicity of small AgNPs by almost 32%, whereas the corresponding decrease for large AgNPs was found to be around 10.6% (55). Mittelman et al. (56) demonstrated that a three-day exposure to UVA and UVB radiation led to increases in the mean diameter, zeta potential, bathochromic shift in SPR, and Ag+ release. The results available in the literature and the data obtained in this study collectively indicate that the presence of light along with the reduction method employed for production of AgNPs indubitably affect the properties of the final product. The characterization of our produced AgNPs indicate that these NPs might be useful in biological applications, since biological functional groups are involved in reduction and capping. In practice, the AgNP synthesis process was found to have higher yield under high pH conditions, but production can also be achieved using a relatively low pH in conjunction with light. The combination of data obtained from this study and the related literature implies that pigment is the major reducing and stabilizing agent in this process, with NaOH and light playing the role of accelerator and mediator, respectively.