China
Africa
Explore chapters and articles related to this topic
Influence of Light on Essential Oil Constituents
Published in K. Hüsnü Can Başer, Gerhard Buchbauer, Handbook of Essential Oils, 2020
Marie-Christine Cudlik, Gerhard Buchbauer
And not only does irradiation affect the living plant, but also the finished product, the EO, once it is situated outside the plant. When photosensitive EO constituents are submitted to electromagnetic radiation, the molecules may experience photoexcitation, which means they reach an excited state by absorbing the ultraviolet, visible or infrared light (IUPAC, 1997). Usually, they are initially transferred to an excited singlet state with a short lifespan, followed by fast radiationless relaxation, which leads via intersystem crossing to an energetically lower excited triplet state (Van den Bergh, 1986). As a consequence of the molecule's excitation, its oxidative and reductive properties are enhanced, increasing the possibility of electron transfer processes (Ochsner, 1997). Many different photoreactions are possible due to the chemical heterogeneity of EOs. They consist of 20 to 200 or even more single substances (Hänsel and Sticher, 2010), although mostly of two to three main constituents (20%–95%) and others only in trace amounts (
Scintillating quantum dots
Published in Sam Beddar, Luc Beaulieu, Scintillation Dosimetry, 2018
Claudine Nì. Allen, Marie-Ève Lecavalier, Sébastien Lamarre, Dominic Larivière
Even if the ligands stabilize the cQD surface, they are labile: a ligand is not irreversibly bonded to the surface and is able to diffuse in the solvent as well as bond to another cQD. The degree of stability of a ligand on the surface is dictated by the bonding strength between ligands and cQD surface as well as the stability of the ligands in the solvent. The weaker is the bond on the semiconductor surface, the more labile is the ligand. Such labile ligands are therefore in thermodynamic equilibrium between the bonded state on the surface and the free state in the solvent. As a result, the surface is still in interaction with its environment and can always undergo chemical reactions, especially under photoexcitation.
Determination
Published in David Woolley, Adam Woolley, Practical Toxicology, 2017
Phototoxicity is also a potential problem; for instance, the presence in celery of psoralens has been associated in celery pickers with extensive skin reactions brought about by sunlight-induced reaction of the psoralens with DNA, inhibiting DNA repair. Treatment of psoriasis with so-called psoralen and UVA (PUVA) therapy–8-methoxypsoralen and UV light–was associated with the induction of cancer. Certain cosmetic ingredients have also been associated with phototoxicity and with more mundane forms of dermatitis. It is worth pointing out that there is a distinction to be drawn between phototoxicity and photoallergy and vice versa. Phototoxicity is likely to occur on first exposure; it is dose related and may be seen after systemic or topical exposure. The mechanism is usually one of photoexcitation, leading to the generation of oxygen or other free radicals. Psoralens intercalate with DNA-producing adducts and inhibition of DNA synthesis. Photoallergy is a delayed type IV hypersensitivity reaction, which–as with other routes of sensitization–requires prior sensitization. Following induction, small amounts of exposure can lead to a reaction. Photoallergy induced by topical exposure is known as photocontact dermatitis and by systemic exposure as systemic photoallergy.
Photothermal therapies to improve immune checkpoint blockade for cancer
Published in International Journal of Hyperthermia, 2020
Preethi B. Balakrishnan, Elizabeth E. Sweeney, Anvitha S. Ramanujam, Rohan Fernandes
Many organic dyes undergo photoexcitation followed by non-radioactive relaxation of the excited species. This non-radioactive relaxation can generate heat that is utilized for killing cancer cells during PTT. Various organic dyes such as cyanine-based dyes (e.g., indocyanine green (ICG)) including heptamethine cyanines (e.g., IR825, IR780, IR808, IR2) and phthalocyanines (e.g., metallo-naphthalocyanines), diketopyrrolopyrrole-based agents, croconaine-based dyes, porphyrin-based dyes, polymer-based dyes (e.g., polypyrrole) have been used for PTT either as free agents or within nanoparticles. These formulations have been used alone and in combination with chemotherapy, radiation therapy, immunotherapies or therapies targeting epigenetic modulation [50,125,126]. Here, we review the latest studies using the organic dyes ICG, polydopamine and IR820 as PTT agents in combination with ICB.
Graphene nano-ribbon based high potential and efficiency for DNA, cancer therapy and drug delivery applications
Published in Drug Metabolism Reviews, 2019
Seyyed Mojtaba Mousavi, Sadaf Soroshnia, Seyyed Alireza Hashemi, Aziz Babapoor, Younes Ghasemi, Amir Savardashtaki, Ali Mohammad Amani
Photo thermal therapy with nano materials and strong absorption of near-infrared (NIR) light has gained more attention during the past few years compared to any other cancer treatment of advanced-stage cancers such as surgery, chemotherapy, radiotherapy, and sometimes a combination of them (Coates et al. 1983; Sun et al. 2008; Agarwal et al. 2010; Li et al. 2011; Markovic et al. 2011; Akhavan et al. 2012; Ma et al. 2012; Lu et al. 2014; Gholami et al. 2016; Emadi et al. 2017). Other treatments are known to offer significant disadvantages including severe adverse reactions (Szakács et al. 2006; Splinter 2007) and low competence against resistant cancer cells (Hu et al. 2010; Shao et al. 2010). But, photo thermal treatment depends on photoexcitation of attaching photosensitizing agents to cancer cells for overheating and consequently wrecking the cells (Heo et al. 2011).
Gene therapy for Leber congenital amaurosis
Published in Expert Review of Ophthalmology, 2018
Neruban Kumaran, Alexander J. Smith, Michel Michaelides, Robin Ali, James Bainbridge
Retinal guanylate cyclase-1 (GUCY2D) is essential in photoreceptor cells for timely recovery from photoexcitation. Mutations in the GUCY2D gene account for 10–20% of LCA. Photoreceptor architecture in GUCY2D-LCA is relatively well preserved [44] and preclinical studies of gene augmentation therapy in animal models have demonstrated benefit. HIV1-based lentiviral vector in ovo improves optokinetic reflexes and volitional visual behavior in a chicken model [45]. In the GC1 knockout mouse, both AAV serotype 5 (AAV5) and AAV8 vectors can protect retinal function and preserve of cone photoreceptor cells [46–48]. In the GC1/GC2 double knockout mouse, the tyrosine capsid mutant AAV8(Y733F) restores both cone- and rod-mediated vision [49]. Proof of principle in experimental models and relative preservation of photoreceptor cells in affected humans suggest that affected individuals stand to benefit from gene augmentation therapy.