Photooxidation Products of Merocyanine 540 Formed Under Preactivation Conditions for Tumor Therapy

Franck, Burchard; Schneider, Udo

doi:10.1111/j.1751-1097.1992.tb02157.x

Cited by 24 publications

(19 citation statements)

References 16 publications

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“…This hypothesis is in line with the studies demonstrating light-induced bleaching or photo-oxidation of MC540 and the subsequent generation of the photoproducts (51,53).…”

Section: The Concept Of Preactivation-oxidative Degradation Of the Phsupporting

confidence: 75%

Reactive oxygen‐dependent production of novel photochemotherapeutic agents

Pervaiz

2001

FASEB j.

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The reactive nature of species derived from oxygen, such as singlet oxygen and hydrogen peroxide, has been exploited in the clinical setting for targeting bacteria, viruses, and tumor cells by photodynamic excitation of a variety of chromophores. This modality, termed photodynamic therapy (PDT), is currently being used to treat some forms of cancer. However, the applicability of conventional PDT is limited due to the absolute dependence on simultaneous exposure of the target to the photoactive compound and light. In 1990, we demonstrated that the need for simultaneous exposure of the biological target to light and photosensitizer could be circumvented by prior exposure (activation) of the sensitizer molecule to light and its subsequent use as any other anti-cancer or anti-viral drug. By dint of the nature of the protocol, this process was termed preactivation. Since then, the generation of biologically active molecules in vitro by preactivation has been validated using a variety of chromophores, such as merocyanine 540, Photofrin II, and naphthalimide. Here we briefly review the role of reactive oxygen species in the photodynamic effect, and provide an explanation for the mechanism of preactivation. We propose that photo-oxidation not only provides a novel means for the generation of biologically active molecules, but could also explain, at least in part the mechanism of conventional PDT. It is likely that the light-dependent breakdown of the chromophore to generate novel active compounds, in addition to reactive oxygen species, also contributes to the photodynamic damage observed on simultaneous exposure of the chromophore and target tissue to light during PDT.-Pervaiz, S. Reactive oxygen-dependent production of novel photochemotherapeutic agents.

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“…This hypothesis is in line with the studies demonstrating light-induced bleaching or photo-oxidation of MC540 and the subsequent generation of the photoproducts (51,53).…”

Section: The Concept Of Preactivation-oxidative Degradation Of the Phsupporting

confidence: 75%

Reactive oxygen‐dependent production of novel photochemotherapeutic agents

Pervaiz

2001

FASEB j.

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“…Because of the availability of experimental data of Franck and Schneider 28, which reveals the UV absorption spectra of merocil and merodantoin molecules, an initial study included calculations of these model molecules (molecules 2 and 3 in Scheme ) where n ‐butyl substituents are replaced by hydrogens. These substituents do not change substantially the spectra.…”

Section: Resultsmentioning

confidence: 99%

Ab initio study of electronic spectra of merocyanine 540 and its photoproducts

Mach¹,

Urban²,

Leszczyński³

2002

Int J of Quantum Chemistry

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Molecular structures of three derivatives of merocyanine 540 (MC 540) were studied using the density functional method in conjunction with the 6-31G*, 6-31G**, and 6-311G** basis sets. The excited states were calculated using the configuration interaction method involving singly excited configurations (CIS). The predicted transition energies and oscillator strength agree well with the experimental UV adsorption spectra of the studied systems. The existence of two stable conformers of merocyanine explain the experimentally observed dependence of the UV spectra upon the change of concentration of added salts.

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“…This process simply involved exposure of the chromophore to light prior to its use in biological systems and subsequent validation of the biological activity (independent of light) of the photo‐activated material or the photoproducts thereof. The basic premise behind this idea was that 1 O 2 generated upon exposure of a fluorescent compound to light in the presence of molecular O 2 could back‐attack the chromophore itself, 52 thereby resulting in photo‐oxidation of the compound or its breakdown into smaller biologically active entities 53 . Indeed, this was successfully demonstrated using the polymethine cationic dye merocyanine 540 (MC540), which has been used in photodynamic reactions.…”

Section: Photo‐activation: Modality For Generating Novel Small Moleculesmentioning

confidence: 99%

“…The basic premise behind this idea was that 1 O 2 generated upon exposure of a fluorescent compound to light in the presence of molecular O 2 could back-attack the chromophore itself, 52 thereby resulting in photo-oxidation of the compound or its breakdown into smaller biologically active entities. 53 Indeed, this was successfully demonstrated using the polymethine cationic dye merocyanine 540 (MC540), which has been used in photodynamic reactions. Photo-oxidized MC540 (pMC540) elicited potent biological activity against a variety of tumour cells and viruses in the absence of light.…”

Section: Photo-activation: Modality For Generating Novel Small Moleculesmentioning

confidence: 99%

Art and Science of Photodynamic Therapy

Pervaiz

Olivo

2006

Clin Exp Pharma Physio

129

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4. Light sources have moved from the use of white light with specific filters in the old days to the more recent use of monochromatic light sources, such as lasers, to more sophisticated light-emitting diodes. However, dosimetry remains a big issue mainly because of difficulties in establishing the optimum treatment conditions for an approach that requires the finetuning of several variables, such as sensitizer and light doses and drug-to-light interval, as well as the issues of skin photosensitivity and low selectivity. A newer development to circumvent these and provide a broader application for this concept has been the phenomenon of photo-activation, whereby photo-exposure of chromophores to generate novel, small biologically active compounds has been demonstrated successfully.5. The aim of the present review was to provide a general overview of the art and science of photodynamic therapy and to highlight some of the issues and recent developments in further advancing this modality of treatment.

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Photooxidation Products of Merocyanine 540 Formed Under Preactivation Conditions for Tumor Therapy

Cited by 24 publications

References 16 publications

Reactive oxygen‐dependent production of novel photochemotherapeutic agents

Reactive oxygen‐dependent production of novel photochemotherapeutic agents

Ab initio study of electronic spectra of merocyanine 540 and its photoproducts

Art and Science of Photodynamic Therapy

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