Photodynamic therapy , selective

Kramer M, Miller JW, Michaud N, et al. Liposomal benzoporphyrin derivative verte-porfin photodynamic therapy. Selective treatment of choroidal neovascularization in monkeys. Ophthalmology 1996 103 427-438. 

Investigations of the kinetics of hole transfer in DNA by means of pulse radiolysis of synthetic ODNs have provided details about the hole transfer process, especially over 1 /is, including the multi-step hole transfer process. Based on the investigation of the kinetics of hole transfer in DNA, development of the DNA nanoelectronic devices is now expected. An active application of the hole transfer process is also desirable from a therapeutical point of view, since hole transfer may play a role in improvement of quantum yield and selectivity of DNA scission during photodynamic therapy. The kinetics of the hole transfer process is now being revealed, although there is still much research to be performed in this area. The kinetics of adenine hopping is another area of interest that should be explored in the future. 

Photodynamic therapy for the treatment of tumours involves the selective uptake and retention of a highly-coloured porphyrin sensitiser (Figure 6.17) in the tumour. Irradiation by a laser with a wavelength corresponding to the absorption maximum of the porphyrin (D) causes excitation of the porphyrin to the excited singlet state. 

Presently photodynamic therapy (PDT) is considered as a perspective way for therapy of different diseases, including cancer. PDT is a method based on the local light-induced activation of photosensitizers able to accumulate selectively in energy-deficient cells (malignant or dysplastic ones) not influencing the remaining normal cells of the body (Pass, 1993). Upon the action of irradiation of certain wavelength characteristic for individual photosensitizer, photochemical reaction occurs... 

Functional dyes of many types are important photochemical sensitizers for chemical reactions involving oxidation, polymerization, (polymer) degradation. isomerization, and photodynamic therapy. Often, dye structures from several classes or materials can fulfill a similar technological need, particularly for laboratory or small-scale reactions where production efficiency may be of secondary importance. Commercial photochemical technology, however, is more selective and requires photochemical efficiency, ease of product separation, and lack of unwanted side reactions to an extent similar to that required by imaging processes. In addition, reusability of the spectral sensitizer is also preferred in commercial photochemical reactions. 

Photodiagnosis is a method based on selective excitation of luminescence emitted by a compound (e.g. Zn(PPIX)) accumulated in blood (e.g. in a treatment of iron-deficiency anemia) or cells (e.g. in a treatment of malignant neoplasms, when the photodiagnosis can precede photodynamic therapy). 

Fundamentals of heterogeneous photocatalysis have been described in Chapter 7. The photodynamic activity of Ti02 (based on its photocatalytic activity and high efficiency in ROS generation) can find applications in photodynamic therapy (PDT) and photodynamic inactivation of microorganisms (PDI), described in Chapters 17 and 18, respectively. Selected environmental aspects of heterogeneous photocatalysis are described below. 

In work that also involves the use of a Mn(III) porphyrin, Huang et al. published a report on the manganese chelate of the tetrakiscarborane carboxylate ester of 2,4-(a, P-dihydroxylethyl)deuteroporphyrin IX (MnBOPP, 9, Figure 2) [19]. The free-base form of this derivative, BOPP, has demonstrated potential as an agent for boron neutron capture therapy (BNCT) [75,76] and photodynamic therapy (PDT) [77] and is known to localize selectively in cerebral glioma tumors at ratios as high as 400 1 relative to normal brain tissue [19,78]. Like the free-base, MnBOPP also selectively localizes in tumor tissue. Specifically, it has been shown to enhance preferentially the... 

Choroidal neovascularization associated with age-related macular degeneration is difficult to treat with conventional laser procedures because normal retinal tissues can be destroyed, which results in loss of central vision. Photodynamic therapy offers the opportimity to selectively eradicate neovascular membranes while producing minimal damage to normal retinal and choroidal tissues. 

Third, since a chemical reaction induced by multibeam irradiation only proceeds at the position where both beams overlap, a chemical process induced by multibeam irradiation is a site-selective process. This third advantage is important in photodynamic therapy, in which damage to healthy cells must be avoided. One of the most advanced techniques is to perform selective damage of cancer tissues deep beneath the skin surface (Fig. 2.4). Molecular memory is also possible when taking this feature into account. Because various reactive... 

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