Protoporphyrin IX Nanoparticle Carrier: Preparation, Optical Properties, and Singlet Oxygen Generation

The present study is focused on developing a nanoparticle carrier for the photosensitizer protoporphyrin IX for use in photodynamic therapy. The entrapment of protoporphyrin IX (Pp IX) in silica spheres was achieved by modification of Pp IX molecules with an organosilane reagent. The immobilized drug preserved its optical properties and the capacity to generate singlet oxygen, which was detected by a direct method from its characteristic phosphorescence decay curve at near-infrared and by a chemical method using 1,3-diphenylisobenzofuran to trap singlet oxygen. The lifetime of singlet oxygen when a suspension of Pp IX-loaded particles in acetonitrile was excited at 532 nm was determined as 52 mu s, which is in good agreement with the value determined for methylene blue in acetonitrile solution under the same conditions. The Pp IX-loaded silica particles have an efficiency of singlet oxygen generation (eta Delta) higher than the quantum yield of free porphyrins. This high efficiency of singlet oxygen generation was attributed to changes on the monomer-dimer equilibrium after photosentisizer immobilization.

Chlorella vulgaris up-modulation of myelossupression induced by lead: The role of stromal cells

In this study, Chlorella vulgaris (CV) was examined for its chelating effects on the ability of bone marrow stromal cell layer to display myeloid progenitor cells in vitro in lead-exposed mice, using the long-term bone marrow culture (LTBMC). In addition, the levels of interleukin (IL)-6, an important hematopoietic stimulator, as well as the numbers of adherent and non-adherent cells were also investigated. Mice were gavage treated daily with a single 50 mg/kg dose of CV for 10 days, concomitant to continuous offering of 1300 ppm lead acetate in drinking water. We found that CV up-modulates the reduced ability of stromal cell layer to display myeloid progenitor cells in vitro in lead-exposed mice and restores both the reduced number of non-adherent cells and the ability of stromal cells from these mice to produce IL-6. Monitoring of lead poisoning demonstrated that CV treatment significantly reduced lead levels in blood and tissues, completely restored the normal hepatic ALA levels, decreased the abnormally high plasma ALA and partly recovered the liver capacity to produce porphyrins. These findings provide evidence for a beneficial use of CV for combination or alternative chelating therapy to protect the host from the damage induced by lead poisoning. (C) 2008 Elsevier Ltd. All rights reserved.

A new micro/nanoencapsulated porphyrin formulation for PDT treatment

The highly hydrophobic 5,10,15-triphenyl-20-(3-N-methylpyridinium-yl)porphyrin(3MMe)cationic species was synthesized, characterized and encapsulated in marine atelocollagen/xanthane gum microcapsules by the coacervation method. Further reduction in the capsule size, from several microns down to about 300-400 nm, was carried out successfully by ultrasonic processing in the presence of up to 1.6% Tween 20 surfactant, without affecting the distribution of 3MMe in the oily core. The resulting creamlike product exhibited enhanced photodynamic activity but negligible cytotoxicity towards HeLa cells. The polymeric micro/nanocapsule formulation was found to be about 4 times more phototoxic than the respective phosphatidylcholine lipidic emulsion, demonstrating high potentiality for photodynamic therapy applications. (C) 2009 Elsevier B.V. All rights reserved.

Can mass dissociation patterns of transition-metal complexes be predicted from electrochemical data?

The Cooks kinetic method has been very convenient to correlate the relative dissociation rates obtained by collision-induced fragmentation experiments with the energies of two related bonds in molecules and complexes in the gas phase. Reliable bond energy data are, however, not always available, particularly for polynuclear transition-metal complexes, such as the triruthenium acetate clusters of the general formula [Ru(3) (mu(3)-O)(mu-CH(3)COO)(6)(py)(2)(L)](+), where L = ring substituted N-heterocyclic ligands. Accordingly, their gas-phase collision-induced tandem mass spectrometry (CID MS/MS) dissociation patterns have been analyzed pursuing a relationship with the more easily accessible redox potentials (E(1/2)) and Lever`s E(L) parameters. In fact, excellent linear correlations of In(1/2A(L)/A(py)), where A(py) and A(L) are the abundance of the fragments retaining the pyridine (py) and L ligand, respectively, with E(1/2) and E(L) were found. This result shows that those electrochemical parameters are correlated with bond energies and can be used in the analysis of the dissociation data. Such modified Cooks method can be used, for example, to determine the electronic effects of substituents on the metal-ligand bonds for a series of transition-metal complexes. Copyright (C) 2008 John Wiley & Sons, Ltd.

Catalytic oxidation of hydrocarbons by trinuclear mu-oxo-bridged ruthenium-acetate clusters: Radical versus non-radical mechanisms

The [Ru(3)O(H(3)CCO(2))(6)(py)(2)(L)]PF(6) clusters, where L=methanol or dimethyl sulfoxide, can be activated by peroxide or oxygen donor species, such as tert-butyl hydroperoxide (TBHP) or iodosylbenzene (PhIO), respectively, generating reactive intermediates of the type [Ru(3)(IV,IV,III)=0](+). In this way, they catalyse the oxidation of cyclohexane or cyclohexene by TBHP and PhIO, via oxygen atom transfer, rather than by the alternative oxygen radical mechanism characteristic of this type of complexes. In addition to their ability to perform efficient olefin epoxydation catalysis, these clusters also promote the cleavage of the C-H bond in hydrocarbons, resembling the oxidation catalysis by metal porphyrins. (C) 2008 Elsevier Inc. All rights reserved.

Quenching of excited states of red-pigment zinc protoporphyrin IX by hemin and natural reductors in dry-cured hams

Zinc protoporphyrin IX (ZnPP), the major red pigment in hams dry-cured without nitrates/nitrites, is an efficient photosensitizer, which upon absorption of visible light forms short-lived excited singlet state ((1)ZnPP*) and by intersystem crossing yields the very reactive triplet-excited state ((3)ZnPP*). Using nano-second laser flash photolysis and transient absorption spectroscopy NADH, ascorbic acid, hemin and dehydroascorbic acid were each found to be efficient quenchers of (3)ZnPP*. The deactivation followed, in homogeneous dimethyl sulfoxide (DMSO) or DMSO:water (1:1) solutions, second-order kinetics. The rate constant for ascorbic acid and NADH for reductive quenching of (3)ZnPP* was at 25 A degrees C found to be 7.5 +/- A 0.1 x 10(4) L mol(-1) s(-1) and 6.3 +/- A 0.1 x 10(5) L mol(-1) s(-1), respectively. The polyphenols catechin and quercetin had no effect on (3)ZnPP*. The quenching rate constant for oxidative deactivation of (3)ZnPP* by dehydroascorbic acid and hemin was at 25 A degrees C: 1.6 +/- A 0.1 x 10(5) L mol(-1) s(-1) and 1.47 +/- A 0.1 x 10(9) L mol(-1) s(-1), respectively. Oxidized glutathione did not act as an oxidative quencher for (3)ZnPP*. After photoexcitation of ZnPP to (1)ZnPP*, fluorescence was only found to be quenched by the presence of hemin in a diffusion-controlled reaction. The efficient deactivation of (3)ZnPP* and (1)ZnPP* by the metalloporphyrin (hemin) naturally present in meat may accordingly inherently protect meat proteins and lipids against ZnPP photosensitized oxidation.