Type II photooxidation mechanism of biomolecules using chloro (5,10,15,20-Tetraphenylporphyrinato) indium (III) as a photosensitizer

Silva, André Romero da; Ribeiro, Joselito Nardy; Rettori, Daniel; Jorge, Renato Atílio

doi:10.1590/s0103-50532008000700013

Cited by 5 publications

(2 citation statements)

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“…The formed ROS initiate a cascade of events that result in reduction or oxidation of vital components (e.g., proteins and lipids) in the cellular compartment of the cancerous tissue and thereby cause cell death and tumor eradication. Numerous studies have suggested that the PDT toxicity in the cells is mainly mediated by singlet oxygen which dominates the ROS profile (type II mechanism). − In the type II mechanism, the photosensitizer in the excited triplet state can interact with ground state oxygen molecules, generating singlet oxygen through an energy transfer process. , An alternative route is the type I mechanism in which the photosensitizer in the excited triplet state can interact directly with the substrate and/or solvent through electron or proton transfer processes. This leads to generation of charged or neutral radicals, which quickly react with oxygen molecules to produce ROS such as superoxide (O 2 −• ) and hydroxyl (OH • ) radicals and hydrogen peroxide (H 2 O 2 ).…”

Section: Introductionmentioning

confidence: 99%

“…Numerous studies have suggested that the PDT toxicity in the cells is mainly mediated by singlet oxygen which dominates the ROS profile (type II mechanism). [6][7][8][9] In the type II mechanism, the photosensitizer in the excited triplet state can interact with ground state oxygen molecules, generating singlet oxygen through an energy transfer process. 10,11 An alternative route is the type I mechanism in which the photosensitizer in the excited triplet state can interact directly with the substrate and/or solvent through electron or proton transfer processes.…”

Section: Introductionmentioning

confidence: 99%

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Photocatalytic Generation of Oxygen Radicals by the Water-Soluble Bacteriochlorophyll Derivative WST11, Noncovalently Bound to Serum Albumin

et al. 2009

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Light-induced radical generation is the hallmark of fundamental processes and many applications including photosynthesis and photodynamic therapy (PDT). In this manuscript, we present two novel observations made upon monitoring light-induced generation of reactive oxygen species (ROS) in aqueous solutions by WST11, a water-soluble derivative of the photosynthetic pigment Bacteriochlorophyll a (Bchl). Using a host of complementary experimental techniques including time-resolved spectroscopy at the subpicosecond to the millisecond range, ESR spectroscopy, electrochemistry, spectroelectrochemistry, oximetry, and protein mass spectroscopy, we first show that in aqueous solutions WST11 generates only superoxide (O 2 -•) and hydroxyl (OH • ) radicals with no detectable traces of singlet oxygen. Second, we show that WST11 makes a noncovalent complex with human serum albumin (HSA) and that this complex functions as a photocatalytic oxidoreductase at biologically relevant concentrations enabling approximately 15 cycles of electron transfer from the associated HSA protein to molecular oxygen in the solution. These findings rule out the paradigm that porphyrin and chlorophyll based PDT is mainly mediated by formation of singlet oxygen, particularly in vascular targeted photodynamic therapy (VTP) with sensitizers that undergo photoactivation during circulation in the plasma, like [Pd]-Bacteriopheophorbide (WST09, Tookad). At the same time, our findings open the way for new design paradigms of novel sensitizers, since O 2 -• and OH • radicals are well-recognized precursors of important pathophysiological processes that can be activated for achieving tumor eradication. Moreover, the finding that promiscuous protein scaffolds become sinks for holes and electrons when holding light-activated pigments provides a new insight to the evolution and action mechanism of natural light activated oxidoreductases (such as photosynthetic reaction centers) and new guidelines for the preparation of synthetic-light converting machineries.

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