Transdermal delivery of probenecid: the effects of vehicles and enhancers on permeation through pig skin

Vehicles and enhancers effect on in vitro probenecid permeation through dermatomed abdominal pig skin was investigated. The permeability of different probenecid percentages dispersed in vehicles as vaseline, carbopol/ethanol/water and carbopol/propylene glycol was tested. The 1.3% L-menthol addition, as permeation enhancer, over probenecid/vaseline formulations showed the highest values for both, flux and permeation coefficient. Permeation experiments of the probenecid formulations in carbopol/ propylene glycol showed that the carbopol/probenecid concentration relation is the most important issue to be considered. Comparatively to lipophilic vehicle (vaseline), carbopol dispersions seen to be more convenient as vehicle for topical administration of probenecid. The results obtained from this study may be helpful in the development of a probenecid transdermal drug delivery system.Colegio de Farmacéuticos de la Provincia de Buenos Aire

Synthesis and Characterization of a Heteroleptic Ru(II) Complex of Phenanthroline Containing Oligo-Anthracenyl Carboxylic Acid Moieties

In an effort to develop new ruthenium(II) complexes, this work describes the design, synthesis and characterization of a ruthenium(II) functionalized phenanthroline complex with extended π-conjugation. The ligand were L1 (4,7-bis(2,3-dimethylacrylic acid)-1,10-phenanthroline), synthesized by a direct aromatic substitution reaction, and L2 (4,7-bis(trianthracenyl-2,3-dimethylacrylic acid)-1,10-phenanthroline), which was synthesized by the dehalogenation of halogenated aromatic compounds using a zero-valent palladium cross-catalyzed reaction in the absence of magnesium-diene complexes and/or cyclooctadienyl nickel (0) catalysts to generate a new carbon-carbon bond (C-C bond) polymerized hydrocarbon units. The ruthenium complex [RuL1L2(NCS)2] showed improved photophysical properties (red-shifted metal-to-ligand charge-transfer transition absorptions and enhanced molar extinction coefficients), luminescence and interesting electrochemical properties. Cyclic and square wave voltammetry revealed five major redox processes. The number of electron(s) transferred by the ruthenium complex was determined by chronocoulometry in each case. The results show that processes I, II and III are multi-electron transfer reactions while processes IV and V involved one-electron transfer reaction. The photophysical property of the complex makes it a promising candidate in the design of chemosensors and photosensitizers, while its redox-active nature makes the complex a potential mediator of electron transfer in photochemical processes

Photo-activated thin films of porphyrins for reactive oxygen species generation

The use of a single component porphyrin thin-film for photodynamic antimicrobial chemotherapy is unexplored. Herein, a porphyrin with good film formation properties is used to make thin layers, by physical vapor phase deposition, that are stable in aqueous media and can generate singlet oxygen upon 650 nm excitation. The synthesis and photophysical studies, in solution and as thin film, of free base 5,10,15,20-tetra-(4-hexyloxyphenyl)porphyrin are described. The porphyrin was synthesized via modified Adler-Longo conditions. Thin films of this porphyrin were made on quartz glass via spin coating and via vapour-phase deposition. The porphyrin was studied, in solution and as thin film (without a polymer component or matrix), with UV-Vis spectroscopy and with steady-state and time-resolved photoluminescence spectroscopy. The spin coated films display sharp J-band emission at 741 nm, indicating J-aggregate formation, but are not stable in aqueous media. The thin films obtained via vapour-phase deposition do not show the J-band emission, but are stable. The detection of singlet oxygen generated by the porphyrin thin film using a chemiluminescent water-soluble singlet oxygen probe is reported

Making triplets from photo-generated charges: observations, mechanisms and theory

Triplet formation by charge recombination is a phenomenon that is encountered in many fields of the photo-sciences and can be a detrimental unwanted side effect, but can also be exploited as a useful triplet generation method, for instance in photodynamic therapy. In this Perspective we describe the various aspects that play a role in the decay of charge separated states into local triplet states. The observations and structures of a selection of (pre-2015) molecular electron donor-acceptor systems in which triplet formation by charge recombination occurs are reported. An overview is given of some more recent systems consisting of BODIPY dimers, and BODIPYs attached to various electron-donor units displaying this same triplet formation process. A selection of polymer-fullerene blends in which triplet formation by (non-geminate) charge recombination has been observed, is presented. Furthermore, in-depth information regarding the mechanistic aspects of triplet formation by charge recombination is given on spin dephasing, through hyperfine interactions, as well as on spin-orbit coupling occurring simultaneously with charge recombination. The limits and constraints of these factors and their role in intersystem crossing are discussed. A pictorial view of the two mechanisms is given and this is correlated to aspects of the selection rules for triplet formation, the so-called El-Sayed rules. It is shown that the timescale of triplet formation by charge recombination is indicative for the mechanism that is responsible for the process. The relatively slow rates (CRkT ~ 1 x 108 s-1 or slower) can be correlated to proton hyperfine interactions (also called the radical pair mechanism), but substantially faster rates (CRkT ~ 1 x 109 up to 2.5 x 1010 s-1 or faster) have to be correlated to spin-orbit coupling effects. Several examples of molecular systems showing such fast rates are available and their electron donor and acceptor orbitals display an orthogonal relationship with respect to each other. This orientation of (the nodal planes of) the pi-orbitals of the donor and acceptor units is correlated to the mechanisms in photodynamic agents and photovoltaic blends

Photo-activated thin films of porphyrins for reactive oxygen species generation

The use of a single component porphyrin thin-film for photodynamic antimicrobial chemotherapy is unexplored. Herein, a porphyrin with good film formation properties is used to make thin layers, by physical vapor phase deposition, that are stable in aqueous media and can generate singlet oxygen upon 650 nm excitation. The synthesis and photophysical studies, in solution and as thin film, of free base 5,10,15,20-tetra-(4-hexyloxyphenyl)porphyrin are described. The porphyrin was synthesized via modified Adler-Longo conditions. Thin films of this porphyrin were made on quartz glass via spin coating and via vapour-phase deposition. The porphyrin was studied, in solution and as thin film (without a polymer component or matrix), with UV-Vis spectroscopy and with steady-state and time-resolved photoluminescence spectroscopy. The spin coated films display sharp J-band emission at 741 nm, indicating J-aggregate formation, but are not stable in aqueous media. The thin films obtained via vapour-phase deposition do not show the J-band emission, but are stable. The detection of singlet oxygen generated by the porphyrin thin film using a chemiluminescent water-soluble singlet oxygen probe is reported

Extending excited-state lifetimes by interchromophoric triplet-state equilibration in a pyrene-Ru(II)diimine dyad system

The synthesis and the spectroscopic properties of a bichromophoric ruthenium trisbipyridyl-1,4-diethynylenebenzene-pyrene system (Ru-b-Py) and the corresponding pyrene ligand (b-Py) are reported. The ruthenium model systems Ru-b-OH, Ru-b-Ph are also presented. UV-Vis absorption and emission at room and low temperature and time-resolved spectroscopy are discussed. For the Ru-b-Py dyad, a mixing of the (MLCT)-M-3 state of the ruthenium-based component and the triplet state of pyrene, Py-3, is observed. Time-resolved transient absorption studies performed on the Ru-b-Py and on the b-Py ligand show that the lowest energy absorption is due to the population of the triplet state localized on the pyrene-component. Time-resolved studies also evidenced a relatively slow forward triplet equilibration rate, in the order of 2 x 10(5) s(-1) (5 mus), and an even slower back energy transfer rate, 3.3 x 10(4) s(-1), still faster than the intrinsic decay time of the pyrene (200 mus)

Tunable fluorescence emission in pyrene-(2,2 '-bipyridine) dyads containing phenylene-ethynylene bridges

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