Current Search: Singlet oxygen (x)
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- Title
- METHOD FOR DETERMINATION OF SINGLET OXYGEN QUANTUM YIELDS FOR NEW FLUORENE-BASED PHOTOSENSITIZERS IN AQUEOUS MEDIA FOR THE ADVANCEMENT OF PHOTODYNAMIC THERAPY.
- Creator
-
Grabow, Wade William, Belfield, Kevin, University of Central Florida
- Abstract / Description
-
Photodynamic therapy (PDT) has been investigated over the past three decades and is currently an approved therapeutic modality for skin cancer, the treatment of superficial bladder, early lung and advanced esophageal cancers, and age-related macular degeneration in a number of countries. In PDT, the absorption of light by a chromophore generates cytotoxic species such as reactive singlet oxygen, leading to irreversible destruction of the treated tissue. The measurement of the singlet oxygen...
Show morePhotodynamic therapy (PDT) has been investigated over the past three decades and is currently an approved therapeutic modality for skin cancer, the treatment of superficial bladder, early lung and advanced esophageal cancers, and age-related macular degeneration in a number of countries. In PDT, the absorption of light by a chromophore generates cytotoxic species such as reactive singlet oxygen, leading to irreversible destruction of the treated tissue. The measurement of the singlet oxygen quantum yield is an important determinant used to evaluate the efficiency of new photodynamic therapy agents developed in the laboratory, to screen potential photosensitizers in aqueous media.The singlet oxygen quantum yield is a quantitative measurement of the efficiency in which photosensitizers are able to use energy, in the form of light, to convert oxygen in the ground state to the reactive species singlet oxygen useful in photodynamic therapy. Singlet oxygen quantum yields of photosensitizers differ when measured in different solvents. The majority of the existing quantum yield values found in literature for various photosensitizers are documented with the sensitizers in organic solvents though values in aqueous media are more valuable for actual applications. Determination of accurate and precise quantum yield values in aqueous solution is a much more difficult problem than in organic media. Problems in aqueous solution arise primarily from the physicochemical properties of singlet oxygen in water. Singlet oxygen has a much shorter lifetime in water than it does in organic solvents, causing challenges with respect to quantitative detection of singlet oxygen.The ensuing pages are an attempt to explore the theory and document the procedures developed to provide the accurate measurement of singlet oxygen in aqueous media. Details of this experimental method and singlet oxygen quantum yield results of new compounds relative to established photosensitizers will be presented.
Show less - Date Issued
- 2004
- Identifier
- CFE0000029, ucf:46138
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0000029
- Title
- SINGLET OXYGEN GENERATION USING NEW FLUORENE-BASED PHOTOSENSITIZERS UNDER ONE- AND TWO-PHOTON EXCITATION.
- Creator
-
Andrasik, Stephen, Belfield, Kevin, University of Central Florida
- Abstract / Description
-
Molecular oxygen in its lowest electronically excited state plays an important roll in the field of chemistry. This excited state is often referred to as singlet oxygen and can be generated in a photosensitized process under one- or two-photon excitation of a photosensitizer. It is particularly useful in the field of photodynamic cancer therapy (PDT) where singlet oxygen formation can be used to destroy cancerous tumors. The use of two-photon activated photosensitizers possesses great...
Show moreMolecular oxygen in its lowest electronically excited state plays an important roll in the field of chemistry. This excited state is often referred to as singlet oxygen and can be generated in a photosensitized process under one- or two-photon excitation of a photosensitizer. It is particularly useful in the field of photodynamic cancer therapy (PDT) where singlet oxygen formation can be used to destroy cancerous tumors. The use of two-photon activated photosensitizers possesses great potential in the field of PDT since near-IR light is used to activate the sensitizer, resulting in deeper penetration of light into biological tissue, less photo-bleaching of the sensitizer, and greatly improved resolution of excitation. The synthesis and photophysical characterization of new fluorene-based photosensitizers for efficient singlet oxygen production were investigated. The spectral properties for singlet oxygen production were measured at room temperature and 77 K. Two-photon absorption (2PA) cross-sections of the fluorene derivatives were measured by the open aperture Z-scan method. The quantum yields of singlet oxygen generation under one- and two-photon excitation (ΦΔ and 2PAΦΔ, respectively) were determined by the direct measurement of singlet oxygen luminescence at ≈ 1270 nm. The values of ΦΔ were independent of excitation wavelength, ranging from 0.6 - 0.9. The singlet oxygen quantum yields under two-photon excitation were 2PAΦΔ ≈ ½ΦΔ, indicating that the two processes exhibited the same mechanism of singlet oxygen production, independent of the mechanism of photon absorption.
Show less - Date Issued
- 2007
- Identifier
- CFE0001860, ucf:47411
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0001860