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Fluorescence in Photodynamic Therapy Dosimetry
| Content Provider | Scilit |
|---|---|
| Author | Wilson, Brian C. Weersink, Robert A. Lilge, Lothar |
| Copyright Year | 2003 |
| Description | Book Name: Handbook of Biomedical Fluorescence |
| Abstract | Photodynamic therapy (PDT) is a technique for treating a variety of malignant and nonmalignant conditions based on the use of light-activated drugs (photosensitizers). Typically, the photosensitizer is administered either systemically (intravenously or orally) or topically to the tissue to be treated. After allowing time for uptake of the photosensitizer to the target tissues or tissue structures, light of an appropriate wavelength to activate the drug is applied. This results in the photoproduction of one or more cytotoxic agents, leading to the intended cellular and tissue effects. For most photosensitizers used or under investigation clinically, it is likely that the main photophysical pathway is production of singlet oxygen,$ $^{1}$O_{2}$. Singlet oxygen is an excited form of oxygen that is highly reactive with biomolecules, leading typically 530to oxidative damage. The Jablonski energy diagram for this so-called type II process is shown in Fig. 1. The absorption of a photon by the ground-state photosensitizer activates the molecule to the excited singlet state. This short-lived state (typically nanoseconds) may de-excite to the ground state either nonradiatively or by fluorescence emission, or may undergo a change of spin to the triplet state. This is relatively long lived, since decay to the ground state is a quantum mechanically forbidden transition. Energy exchange with ground-state oxygen is, however, an allowed transition, since$ $^{3}$O_{2}$ is also a triplet state, and this excites the oxygen to$ $^{1}$O_{2}$. (Note that type I processes are those in which the reactive species are generated directly from the photosensitizer-excited singlet or triplet state and may or may not be oxygen dependent. They also lead to photosensitizer fluorescence from the singlet state.) Figure 1 Jablonski diagram for type II photodynamic reactions. The vertical axis indicates the energy for the distinct electronic states of the photosensitizer and oxygen molecules. |
| Related Links | https://content.taylorfrancis.com/books/download?dac=C2006-0-01587-7&isbn=9780203912096&doi=10.1201/9780203912096-15&format=pdf |
| Ending Page | 562 |
| Page Count | 34 |
| Starting Page | 529 |
| DOI | 10.1201/9780203912096-15 |
| Language | English |
| Publisher | Informa UK Limited |
| Publisher Date | 2003-04-16 |
| Access Restriction | Open |
| Subject Keyword | Book Name: Handbook of Biomedical Fluorescence Physical Chemistry Atomic, Molecular and Chemical Physics Fluorescence Singlet State Indicates the Energy Excited Singlet State Photosensitizer |
| Content Type | Text |
| Resource Type | Chapter |
