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Microscope Designs
Published in Raimund J. Ober, E. Sally Ward, Jerry Chao, Quantitative Bioimaging, 2020
Raimund J. Ober, E. Sally Ward, Jerry Chao
Use of long-wavelength excitation light in two-photon excitation microscopy provides the further advantage of reducing phototoxicity to the cell sample. Phototoxicity refers to cell damage caused by irradiation with light, and is primarily attributed to the production of reactive oxygen species which cause damage to the cell through the oxidation of biological macromolecules such as DNA and proteins. Reactive oxygen species are produced by the reaction of excited molecules with oxygen, and can therefore result from the absorption of excitation light by the fluorophores of interest and by light-absorbing molecules that are endogenous to the cell. Since in a typical cell most endogenous molecules are excited by light in the ultraviolet, violet, and blue regions of the electromagnetic spectrum, the long-wavelength excitation light used in two-photon excitation microscopy produces significantly lower levels of phototoxicity.
Obtainment of an enriched fraction of Inga edulis: identification using UPLC-DAD-MS/MS and photochemopreventive screening
Published in Preparative Biochemistry & Biotechnology, 2020
Georgia de Assis Dias Alves, Daniele Fernandes da Silva, Thainá Venteu Teixeira, Rebeca Oliveira de Souza, Hervé Rogez, Maria José Vieira Fonseca
Phototoxicity tests are based on possible toxic reactions shown by cells after direct contact with the substances tested, followed by exposure to UV sources. Many factors influence the levels of toxicity, such as the concentration of the substance tested, contact time with the cell and dose of UV exposure.[53] Sunscreens have been reported to cause skin irritation, photosensitivity, and contact dermatitis by interaction with cutaneous molecules upon chronic use. As a result, natural compounds like polyphenols are being investigated for their photochemoprotective properties, better skin compatibility, and lower impact on the environment.[54] Therefore, it is important to assess the photostability of plant extracts to guarantee that under UV exposure the extract components will not degrade, which could decrease its biological activity and cause damage to the skin.
Monitoring polycyclic aromatic compounds exposure in fish using biliary metabolites
Published in Critical Reviews in Environmental Science and Technology, 2022
Jamie M. Dearnley, Charles Killeen, Rebecca L. Davis, Vince P. Palace, Gregg T. Tomy
No discourse on PAC toxicity to embryonic fish is complete without addressing photo-enhanced toxicity, which was recently reviewed by Barron (2017). Arising from interactions of certain PACs with UV light in vivo, embryonic and larval fish are particularly susceptible as their small size and translucent bodies expose a relatively large amount of tissue to potential phototoxic effects. Phototoxicity is believed to act primarily through photosensitization in which incident (chiefly UVA) light first promotes a bioaccumulated PAC into an excited electronic state. Then, in the process of relaxing to its ground state, interactions of the PAC with oxygen or other biomolecules ultimately create reactive oxygen species and free radicals which are able to damage surrounding tissues by oxidizing cell structures. Again, this process occurs entirely in vivo with little or no enhanced toxicity occurring as a result of PAC transformations in the environment prior to assimilation by fish. With sufficient duration and intensity of UV exposure, death can result and the intensity of UV light required for photosensitization is found in natural waters (Barron, 2017; Willis & Oris, 2014). Photomodification is a second mechanism of phototoxicity in which parent PACs are photooxidized to toxic products, such as alcohols, ketones, and quinones. Products of PAC photooxidation can exhibit greater toxicity than the parent compound, though photooxidation can also lower phototoxicity through degradation of phototoxic PACs (Choi & Oris, 2003; Ge et al., 2016; Kang et al., 2019). While photomodification is an important aspect of phototoxicity, its importance is generally considered secondary to photosensitization (Barron, 2017). Overall, the toxicity of petroleum is increased two to 100+ fold by photoenhanced toxicity. Specific three to five ring PACs are believed to be responsible for phototoxicity; single PAC exposures have identified anthracene and pyrene as being phototoxic, with phenanthrene much less so (Willis & Oris, 2014). With toxicity arising from water column exposures well-established, recent work has provided the first demonstration of the photoenhanced toxicity of oiled sediment. In this study, zebrafish larvae exposed to weathered oil-contaminated sediment and 3.5 hr of unattenuated natural sunlight incurred a 100% mortality rate, compared to a 0% mortality rate among fish receiving no sunlight or 10% sunlight (Barron et al., 2018).