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Over the years, the performance of the liposomal formulations of temoporfin, Foslip® and Fospeg®, was investigated in a broad array of cell-based assays and preclinical animal models. So far, little attention has been paid to the influence of drug release and liposomal stability on the plasma concentration–time profile. The drug release is a key attribute which impacts product quality and the in vivo efficacy of nanocarrier formulations. In the present approach, the in vitro drug release and the drug-protein transfer of Foslip® and Fospeg® was determined using the dispersion releaser technology. To analyze the stability of both formulations in physiological fluids, nanoparticle tracking analysis was applied. A comparable drug release behavior and a high physical stability with a vesicle size of approximately 92 ± 2 nm for Foslip® and at 111 ± 5 nm for Fospeg® were measured. The development of a novel hybrid in silico model resulted in an optimal representation of the in vivo data. Based on the information available for previous formulations, the model enabled a prediction of the performance of Foslip® in humans. To verify the simulations, plasma concentration–time profiles of a phase I clinical trial were used. An absolute average fold error of 1.4 was achieved. Moreover, a deconvolution of the pharmacokinetic profile into different fractions relevant for the in vivo efficacy and safety was achieved. While the total plasma concentration reached a cmax of 2298 ng/mL after 0.72 h, the monomolecular drug accounted for a small fraction of the photosensitizer with a cmax of 321 ng/mL only.

Mosquitoes are carriers of dangerous infectious disease pathogens all over the world. Owing to travelling and global warming, tropical disease-carrying species such as Aedes, Anopheles and Culex spread beyond tropical and subtropical zones, even to Europe. The aim of this study is to investigate the potential of photodynamic agents to combat mosquito larvae. Three different photosensitizers were tested on Chaoborus sp. larvae: TMPyP and TPPS as antimicrobial photosensitizers, and mTHPC as a PDT drug against eukaryotic animal and human cells. Chaoborus sp. is a commercially available harmless species developing translucent larvae similar to the larvae of Aedes, Anopheles and Culex. The uptake of photosensitizers by the larvae was tested by fluorescence microscopy. All tested photosensitizers were observed in the intestinal tract of the living larvae, and none of the photosensitizers was found in the larval tissues. In phototoxicity tests, mTHPC and TPPS did not have any effect on the larvae, while TMPyP killed the larvae efficiently. TPPS is an antimicrobial photosensitizer, mainly phototoxic to Gram-positive bacteria. TMPyP is well known as an efficient photosensitizer against Gram-negative bacteria like most species of the intestinal flora. From this result, we conclude that the photodynamic inactivation of the intestinal flora leads to the death of mosquito larvae. The feasibility of mosquito larvae control by photodynamic inactivation of their intestinal flora instead of the direct killing of the larvae is a promising alternative to other highly toxic insecticides. Compared to insecticides and other biochemical toxins, photosensitizers are not dark toxic. No resistance against photosensitizers is known so far. Thus, the dilution of the active substances by being distributed in the environment, which promotes the development of resistance in biocides of all kinds, does not pose danger. Thus, it reduces the potential side effects on environment and human health.

PPARγ is a pharmacological target in inflammatory and metabolic diseases. Upon agonistic treatment or following antagonism, binding of co-factors is altered, which consequently affects PPARγ-dependent transactivation as well as its DNA-independent properties. Therefore, establishing techniques to characterize these interactions is an important issue in living cells. Methods: Using the FRET pair Clover/mRuby2, we set up a flow cytometry-based FRET assay by analyzing PPARγ1 binding to its heterodimerization partner RXRα. Analyses of PPARγ-reporter and co-localization studies by laser-scanning microscopy validated this system. Refining the system, we created a new readout to distinguish strong from weak interactions, focusing on PPARγ-binding to the co-repressor N-CoR2. Results: We observed high FRET in cells expressing Clover-PPARγ1 and mRuby2-RXRα, but no FRET when cells express a mRuby2-RXRα deletion mutant, lacking the PPARγ interaction domain. Focusing on the co-repressor N-CoR2, we identified in HEK293T cells the new splice variant N-CoR2-ΔID1-exon. Overexpressing this isoform tagged with mRuby2, revealed no binding to Clover-PPARγ1, nor in murine J774A.1 macrophages. In HEK293T cells, binding was even lower in comparison to N-CoR2 constructs in which domains established to mediate interaction with PPARγ binding are deleted. These data suggest a possible role of N-CoR2-ΔID1-exon as a dominant negative variant. Because binding to N-CoR2-mRuby2 was not altered following activation or antagonism of Clover-PPARγ1, we determined the effect of pharmacological treatment on FRET intensity. Therefore, we calculated flow cytometry-based FRET efficiencies based on our flow cytometry data. As with PPARγ antagonism, PPARγ agonist treatment did not prevent binding of N-CoR2. Conclusion: Our system allows the close determination of protein-protein interactions with a special focus on binding intensity, allowing this system to characterize the role of protein domains as well as the effect of pharmacological agents on protein-protein interactions.

Polymer membranes are powerful filtration tools in medicine and water treatment. Their efficiency and operational lifetime is limited by biofouling caused by microorganisms. This study describes the development of photodynamical active antimicrobial polymer membranes in a one-pot functionalization step using a well-known photosensitizer (PS). Commercially available polyethersulfone (PES) membranes for microfiltration were doped with the polycationic PS TMPyP using electron beam irradiation. These membranes were characterized in terms of binding stability and quantification of the PS and membrane morphology. Furthermore, the photodynamic ability was verified by time resolved singlet oxygen luminescence scans and successfully tested against the Gram-negative bacterium E. coli under low dose white light illumination resulting in the reduction in cell survival of 6 log10 units. Finally, in preliminarily experiments the photodynamic action against the Gram-positive bacteria M. luteus and the Gram-negative P. fluorescence and the mold C. cladosporioides was demonstrated. These promising results show the high photodynamic potential of electron beam functionalization of PES membranes with TMPyP. It preserves the photodynamic abilities of the immobilized PS resulting in efficient photodynamic inactivation of bacteria and mold on the membrane surface. The uprising worldwide spread of antibiotic resistant bacteria makes the development of new antibacterial strategies an inevitable challenge. The photodynamic inactivation of bacteria and its adaptation for antimicrobial surfaces, e.g. filtration membranes for water treatment, displays many advantages in terms of a wide application range, low mutagenic potential and environmental compatibility.

A treatment of onychomycosis using the photodynamic effect would be a favorable alternative to currently used antimycotic drugs. This study should be considered as a first step towards development and control of an efficient photodynamic inactivation of onychomycosis causative pathogens. Here, we evaluate the usage of time-resolved 2D singlet oxygen luminescence detection in combination with 2D fluorescence scanning as a tool to understand the behavior of the photosensitizer when applied to fungi on Petri dishes. To investigate the interaction of photosensitizer with fungi in various concentrations and in different stages of live, a photodynamic inactivation was avoided by keeping the samples in darkness. Scans of singlet oxygen luminescence and photosensitizer fluorescence were performed over a period of 24days. Two different photosensitizer, a cationic porphyrin and cationic corrole and two fungi strains, the dermatophyte Trichophyton rubrum and the mold Scopulariopsis brevicaulis, were investigated in this study. The two-dimensional correlation of photosensitizer fluorescence and singlet oxygen luminescence revealed differences in the diffusion of both photosensitizer. Even though the singlet oxygen luminescence was quenched with increasing growth of fungi, it was found that the kinetics of singlet oxygen luminescence could be detected on Petri dishes for both photosensitizers and both fungi strains for up to seven days.

Photodynamic inactivation (PDI) of bacteria may play a major role in facing the challenge of the ever expanding antibiotic resistances. Here we report about the direct correlation of singlet oxygen luminescence kinetics and phototoxicity in E. coli cell suspension under PDI using the widely applied cationic photosensitizer TMPyP. Through direct access to the microenvironment, the time resolved investigation of singlet oxygen luminescence plays a key role in understanding the photosensitization mechanism and inactivation pathway. Using the homemade set-up for highly sensitive time resolved singlet oxygen luminescence detection, we show that the cationic TMPyP is localized predominantly outside the bacterial cells but in their immediate vicinity prior to photodynamic inactivation. Throughout following light exposure, a clear change in singlet oxygen kinetics indicates a redistribution of photosensitizer molecules to at least one additional microenvironment. We found the signal kinetics mirrored in cell viability measurements of equally treated samples from same overnight cultures conducted in parallel: A significant drop in cell viability of the illuminated samples and stationary viability of dark controls. Thus, for the system investigated in this work - a Gram-negative model bacteria and a well-known PS for its PDI - singlet oxygen kinetics correlates with phototoxicity. This finding suggests that it is well possible to evaluate PDI efficiency directly via time resolved singlet oxygen detection.

The thermally induced changes of the steady-state photoluminescence of a polyphenylene sulfide/elastomer blend under dry heat exposure are investigated. Two signals, a phenylene fluorescence signal and a degradation-induced luminescence signal are identified and found to exhibit different spectral and kinetic properties. A detailed kinetic analysis of the thermally induced changes reveals, that the phenylene fluorescence signal can consistently be interpreted in terms of a cold crystallization process limited by the viscous flow of the polymeric material with an apparent activation energy of 33 ± 12 kJ/mol. On the other hand, the changes of the degradation-induced steady-state luminescence signal can be described by a power law kinetics with an apparent activation energy of 113 ± 25 kJ/mol. The obtained apparent activation energies of the thermally induced material changes and the underlying molecular mechanisms are discussed and related to data available from the literature. In addition to the kinetic analysis of the changes of the degradation-induced steady-state photoluminescence, an equivalent exposure time and temperature can be derived that describe the exposure history of the sample. Furthermore, a relationship between exposure at room temperature and exposure above the glass transition temperature is suggested that, in combination with the density of states model as proposed before, can be used to predict the development of the steady-state luminescence changes over many years of exposure at room temperature.

We have synthesized novel phthalocyanine with four pyridyl substituents connected to α-phthalo-positions via direct C-C bond. The Zn complex and tetracationic derivatives of phthalocyanine were also synthesized and the dyes were impregnated into filter paper to prepare photoactive antimicrobial surface. The photodynamic antimicrobial efficacy of the dyed paper samples was evaluated by a simple and fast setup using bioluminescent microbes. Escherichia coli and Acinetobacter baylyi ADP1 strains carrying bacterial luciferase genes were used in the screening experiment. The most efficient compound, tetracationic zinc derivative 8, was investigated further. The compound was highly water soluble, had high molar absorptivity and exhibited good adhesion to the filter paper without leaching into the solution. The singlet oxygen quantum yield of tetracationic zinc derivative 8 in water was found out to be 30 ± 20%. According to the cell viability assay test performed on E. coli wild type in solution, the molecule had similar or better photo toxicity as the reference photosensitizer, tetrakis (1-methyl-pyridinium-4-yl)porphyrin (TMPyP). Antimicrobial efficacy of the dye 8 on photoactive surface was studied by live cell assessment through colony forming unit (CFU) counting. The colored surface demonstrated 3 log reduction in CFU against E. coli and A. baylyi ADP1 just after 1 h of illumination with the white light of low intensity.

Pointsource photodynamic therapy (PSPDT) is a newly developed fiber optic method aimed at the delivery of photosensitizer, light and oxygen to a diseased site. Because of a need for developing photosensitizers with desirable properties for PSPDT, we have carried out a synthetic, photophysical and phototoxicity study on a series of PEGylated sensitizers. Chlorin and pheophorbide sensitizers were readily amenable to our synthetic PEGylation strategy to reach triPEG and hexaPEG galloyl pheophorbides and mono-, di-, triPEG chlorins. On screening these PEG sensitizers, we found that increasing the number of PEG groups, except for hexaPEGylation, increases phototoxicity. We found that three PEG groups but not less or more were optimal. Of the series tested, a triPEG gallyol pheophorbide and a triPEG chlorin were the most efficient at generating singlet oxygen, and produced the highest phototoxicity and lowest dark toxicity to Jurkat cells. A detailed kinetic analysis of the PEGylated sensitizers in solution and cell culture and media is also presented. The data provide us with steps in the development of PSPDT to add to the PDT tools we have in general.

The complex spectral and temporal changes of degradation-induced polymer photoluminescence of glass fiber reinforced polyamide under thermal degradation are evaluated with the aim to obtain apparent activation energies that could be used for polymer lifetime prediction. Two luminescence bands with different spectral and temporal behavior are identified. The kinetics are analyzed by the model-free approach of time-temperature superposition and by linearization based on non-linear variable transformations to gain information on their physico-chemical properties. In combination with the density of states model of degradation-induced polymer luminescence, for the first time, an empirical model function is developed that takes physically meaningful parameters to describe the luminescence kinetics and provides quantitative information on kinetic parameters. This empirical model function could then be used to create a linearized, temperature-independent master plot of degradation-induced polymer photoluminescence. The model-free approach of time-temperature superposition and the empirical model function both result in identical apparent activation energies that are also consistent with values reported in the literature.

Knowledge about the aging behavior of the polymeric encapsulation material in photovoltaic (PV) modules is a very important factor for lifetime prediction. The inability to apply conventional characterization methods without destruction of the module creates the need for new, sensitive and non-invasive characterization methods. Luminescence has recently been introduced as a non-destructive method to follow the degradation of the most common encapsulation material, ethylene-vinyl acetate copolymer (EVA). In aged PV modules inhomogeneous luminescence patterns were found, which are specific for different aging factors such as accelerated thermal aging, UV aging or outdoor weathering. Spatially resolved dynamic scanning calorimetry (DSC) measurements of the encapsulating EVA of two sets of differently aged PV mini modules reveals a correlation of the recrystallization peak temperature and the luminescence patterns. The spatial distribution of additives in the EVA and the onset temperature of oxidation were found to show no convincing correlation to the luminescence patterns. The results substantiate that a spatial inhomogeneity of crosslinking properties is a manifestation of aging effects, which is attributed to diffusion limited oxidation (DLO) conditions in the EVA between cell and front glass. The characterization of the EVA luminescence behavior taken over the module surface appears as a valuable tool to assess DLO effects.

The synthesis and photophysical properties of a tetra-PEG-modified and freely water-soluble quinoline-annulated porphyrin are described. We previously demonstrated the ability of quinoline-annulated porphyrins to act as an in vitro NIR photoacoustic imaging (PAI) contrast agent. The solubility of the quinoline-annulated porphyrin derivative in serum now allowed the assessment of the efficacy of the PEGylated derivative as an in vivo NIR contrast agent for the PAI of an implanted tumor in a mouse model. A multi-fold contrast enhancement when compared to the benchmark dye ICG could be shown, a finding that could be traced to its photophysical properties (short triplet lifetimes, low fluorescence and singlet oxygen sensitization quantum yields). A NIR excitation wavelength of 790 nm could be used, fully taking advantage of the optical window of tissue. Rapid renal clearance of the dye was observed. Its straight-forward synthesis, optical properties with the possibility for further optical fine-tuning, nontoxicity, favorable elimination rates, and contrast enhancement make this a promising PAI contrast agent. The ability to conjugate the PAI chromophore with a fluorescent tag using a facile and general conjugation strategy was also demonstrated.

Background Singlet oxygen is known to be the main mediator of the photodynamic effect. The kinetics of its generation and deactivation allows for insights in the microenvironment and efficacy of the photodynamic effect. Therefore, it is highly desirable to perform direct and time resolved measurements of singlet molecular oxygen (1O2) as well as data analysis during the therapy. Methods In this work, tumors grown on the CAM of chicken embryos as well as blood vessels were scanned after injection of the photosensitizer Foslip®, yielding time resolved singlet molecular oxygen luminescence. Using a custom-made trifurcated fiber, it is possible to simultaneously detect time resolved NIR luminescence as well as spectrally resolved UV/VIS fluorescence. Results After photosensitizer application the singlet oxygen luminescence kinetics for tumors grown on the CAM of chicken embryos as well as for mixed venous and arterialized blood were recorded. Data was analyzed by traditional fitting as well as a novel and robust approach, reducing the time resolved data to a a meaningful minimum. Both approaches show the differences between blood of different oxygen saturation as well as tumor tissue. Conclusions This work shows for the first time the possibility of deducing the oxygen content during photodynamic therapy by measuring singlet oxygen kinetics in tissue. If more oxygen is consumed – due to chemical quenching during PDT – than is subsequently diffused, oxygen depletion occurs, resulting in inefficiency of the photodynamic effect. These results represent a major step towards live monitoring of therapy success and thus towards the possibility of direct control of PDT efficiency in real time.

Real-time surveillance of photodynamic therapy (PDT) has been desired by the research community for a long time. The impact of the treatment is encoded in the phosphorescence kinetics of its main mediator: singlet oxygen. We report successful in vivo measurements of these weak kinetics through the skin of living mice after systemic drug application. Using special high transmission optics centered around 1200, 1270 and 1340 nm, singlet oxygen phosphorescence can be clearly discriminated from other signals. N-(2-Hydroxypropyl)methacrylamide copolymers conjugated with pyropheophorbide-a exhibit highly selective accumulation in tumors. Signals of this drug in tumors were compared to those in normal tissue. In both places, the major part of the signal could be identified as arising from drug still circulating in the bloodstream. Despite high concentrations of extravasated drug in the tumors due to the EPR effect, nearly no signal could be detected from these photosensitizers in vivo, contradicting in vitro experiments. We propose that the reason for this discrepancy is oxygen depletion in tumor tissue in vivo, even at moderate (at PDT scale) illumination intensities, soon after the start of the illumination. These results underline the importance of singlet oxygen surveillance during PDT treatment.

Foscan®, a formulation comprising temoporfin dissolved in a mixture of ethanol and propylene glycol, has been approved in Europe for palliative photodynamic therapy of squamous cell carcinoma of the head and neck. During clinical and preclinical studies it was observed that considering the administration route, the drug presents a rather atypical plasma profile as plasma concentration peaks delayed. Possible explanations, as for example the formation of a drug depot or aggregation after intravenous administration, are discussed in current literature. In the present study an advanced in silico model was developed and evaluated for the detailed description of Foscan® pharmacokinetics. Therefore, in vitro release data obtained from experiments with the dispersion releaser technology investigating dissolution pressures of various release media on the drug as well as in vivo data obtained from a clinical study were included into the in silico models. Furthermore, precipitation experiments were performed in presence of biorelevant media and precipitates were analyzed by nanoparticle tracking analysis. Size analysis and particle fraction were also incorporated in this model and a sensitivity analysis was performed. An optimal description of the in vivo situation based on in vitro release and particle characterization data was achieved, as demonstrated by an absolute average fold error of 1.21. This in vitro-in vivo correlation provides an explanation for the pharmacokinetics of Foscan® in humans.

Degradation-related polymer luminescence is investigated by means of polarization-sensitive luminescence spectroscopy and anisotropy measurements for different polymers under dry heat ageing conditions. It is found that the spectral development of polymer luminescence with progressive degradation of the polymer is largely independent of the chemical structure and formulation of the polymer. The degradation of the polymer can be categorized into an initial phase with luminescence excited below 300 nm, an intermediate phase with luminescence excited between 300 and 400 nm and a final phase with luminescence excited throughout the full UV/VIS-region. Whereas the properties of the first two phases are consistent with the interpretation as fluorescence originating from individual non-interacting species, the last phase of degradation exhibits luminescence properties, most prominently a high degree of depolarization, consistent with luminescence originating from a density of interacting states that is developed in the process of polymer degradation. A general, polymer independent, model is developed to describe the development of degradation-related polymer luminescence under progressive degradation.

Triphenylamines (TPAs), boron dipyrromethenes (BODIPYs) and fullerenes C60 are excellent building blocks for the design of artificial photosynthetic systems. In the present work, we report the synthesis, characterization and detailed photophysical studies of a novel (TPA)2–BODIPY–C60 tetrad in polar and nonpolar solvents. The absorption spectrum of this compound covered virtually the entire visible region (350–700 nm) and could be interpreted as a superposition of the spectra of individual components. Upon TPA-part excitation, a fast and very efficient excitation energy transfer (EET) delivers the excitation to the BODIPY moiety resulting in complete quenching of the TPA first excited singlet state as well as the appearance of the BODIPY fluorescence. The efficiency of EET process was estimated to be 1. Direct or indirect (via EET) excitation of the BODIPY-part of the tetrad is followed by photoinduced charge transfer to the charge-separated state BODIPY˙+–C60˙− irrespective of the solvent used. In polar N,N-dimethylformamide (DMF) charge recombination occurs directly to the ground state with the charge recombination rate, kCR, slower than 108 s−1, whereas in nonpolar toluene (TOL) a small energy gap between the charge-separated state and first excited singlet state of the BODIPY moiety facilitates the back charge transfer process. The latter results in the appearance of thermally activated delayed fluorescence. The rate of charge separation was found to be ca. 2 times faster in TOL than in DMF.

The degradation-induced polymer photoluminescence and absorbance spectra of two differently stabilized commercial EVA grades are investigated under conditions of exposure to dry heat at 85 °C, 115 °C and 135 °C and moisture of 85% relative humidity at 85 °C. In addition to the photoluminescence signal as described before, new features are identified for both, absorbance and photoluminescence spectra. Most prominently, the formerly suggested initial luminescence signal of the model of degradation-induced polymer photoluminescence is identified at an emission wavelength of about 310 nm. It is shown to exhibit a sequential reaction kinetics and to be related to the absorbance of carbonyl sates at 285 nm. The kinetic parameters of these signals are quantitatively evaluated and discussed in the scope chemical degradation and physical relaxation processes. We demonstrate that additive formulations can be distinguished by means of degradation-induced polymer photoluminescence, enabling its application for the characterization and optimization of polymeric materials.

The interactions between oxygen and lipid membranes play fundamental roles in basic biological processes (e.g., cellular respiration). Obviously, membrane oxidation is expected to be critically dependent on the distribution and concentration of oxygen in the membrane. Here, we combined theoretical and experimental methods to investigate oxygen partition and distribution in lipid membranes of 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) and 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) in a temperature range between 298 and 323 K, specifically focusing on the changes caused by the lipid phase and phase transition. Even though oxygen is known to be more concentrated in the center of fluid phase membranes than on the headgroup regions, the distribution profile of oxygen inside gel-phase bilayers remained to be determined. Molecular dynamics simulations now show that the distribution of oxygen inside DPPC bilayers dramatically changes upon crossing the main transition temperature, with oxygen being nearly depleted halfway from the headgroups to the membrane center below the transition temperature. In a parallel approach, singlet oxygen luminescence emission measurements employing the photosensitizer Pheophorbide-a (Pheo) confirmed the differences in oxygen distribution and concentration profiles between gel- and fluid-phase membranes, revealing changes in the microenvironment of the embedded photosensitizer. Our results also reveal that excited triplet state lifetime, as it can be determined from the singlet oxygen luminescence kinetics, is a useful probe to assess oxygen distribution in lipid membranes with distinct lipid compositions.

Onychomycosis is a fungal nail infection caused primarily by the dermatophytes Trichophyton rubrum and Trichophyton interdigitale or, less frequently, by molds like Aspergillus spp. and Scopulariopsis brevicaulis. Photodynamic treatment of onychomycosis is considered a promising future therapy to overcome the frequent failure of currently used antifungals. In this study, we tested the potential of three photosensitizers for photodynamic inactivation of the onychomycosis causing pathogens T. rubrum, T. interdigitale and S. brevicaulis. Photosensitizers used are 10,15,20-Tetrakis(1-methylpyridinium-4-yl) porphyrintetra(p-toluenesulfonate) (TMPyP), 5,10,15-tris-(1-methylpyridinium-2-yl)corrolato-(trans-dihydroxo)phosphorus(V) (PCor+) and 2',4',5',7'-tetrabromo-3',6'-dihydroxyspiro[2-benzofuran-3,9'-xanthene]-1-one (Eosin Y). The phototoxic effects caused by the cationic photosensitizers (PCor+ and TMPyP) were tested on suspension cultures of spores as well as on fungi during growth on surfaces where both photosensitizers cause high phototoxicity. The anionic Eosin Y was tested on surface-growing fungi only and induces remarkable phototoxic effects on dermatophytes and molds. In all cases, no spore regrowth was detected after PDI. This study is considered a first step towards successful and cost efficient treatment of onychomycosis.

Background Direct singlet molecular oxygen detection is known to be a valuable tool for understanding photodynamic action. It could become useful for optimizing illumination schedules in photodynamic therapy. The method of time resolved singlet molecular oxygen luminescence detection can give insights into generation of singlet oxygen and its interaction with the environment and therefore possibly allows monitoring the treatments efficacy. Due to high requirements for sensitivity as well as time resolution it has not yet been used in situ. The latest improvements in the detection system make in vivo time resolved singlet molecular oxygen luminescence detection possible. Methods In this work, blood vessels in the chicken embryo CAM-model were scanned after injection of the photosensitizer Foslip®, yielding time resolved singlet molecular oxygen luminescence. A custom-made trifurcated fiber in combination with a dye laser, a photomultiplier tube and a fiber spectrometer was utilized for simultaneous excitation, singlet molecular oxygen luminescence and photosensitizer fluorescence detection. Results Singlet oxygen luminescence kinetics for mixed venous and arterialized blood in chicken embryos using the CAM-model were recorded. The data analysis resulted in two distinct and distinguishable photosensitizer triplet lifetimes corresponding to the high and low oxygen partial pressures in the oxygen-rich arterialized blood and oxygen-poor mixed venous blood. Conclusions The sensitivity of direct singlet molecular oxygen luminescence detection to different oxygen partial pressures could be shown in vivo. Therefore, this study is a first step towards optimizing the illumination conditions of photodynamic treatment in situ by real time monitoring of the oxygen partial pressure within the target tissue.

For a reliable lifetime prediction of photovoltaic (PV) modules, the investigation of degradation processes of materials in the product is a fundamental prerequisite. Especially for nondestructive characterization of the encapsulating material, suitable characterization methods are needed. We show that luminescence is a sensitive, noninvasive method for the characterization of the aging of the embedding polymer in PV modules. Luminescence exhibits a good correlation of the aging duration and different aging parameters. A very important feature in aged PV modules is complex 2-dimensional luminescence patterns, which correlate to inhomogeneous aging detected by conventional, destructive methods. The results imply that photoluminescence can be used to follow material degradation and detect inhomogeneous material aging due to diffusion-limited oxidation. Prospective applications for aging investigations of complex products arise as this method improves upon drawing a connection between accelerated aging and outdoor weathering.

In vivo measurement of singlet oxygen luminescence kinetics is affected by the heterogeneity of biological samples. Even though singlet oxygen luminescence detection is technically getting easier, the analysis of signals from biological samples is still far from quantitative real time surveillance as it is aspired by the community. In this paper small unilamellar vesicles (SUVs) are used for modelling the general behaviour of heterogeneous samples. The geometry of the SUVs can be determined independently using dynamic light scattering. Therefore an accurate theoretical description of the generation, deactivation and diffusion of the singlet oxygen is possible. The theoretical model developed here perfectly fits the experimental results. Thus the location of the singlet oxygen generating a photosensitizer molecule can be exactly determined from the kinetics of the singlet oxygen luminescence. The application of the used theoretical approach thus allows for accurate quantitative measurements in SUVs.

Borron dipyrromethenes (BDPs) and perylenediimides (PDIs) are excellent building blocks for the design of artificial light-harvesting systems. In the present work, we report the results of photophysical studies of a novel dyad, in which BDP and PDI chromophores are covalently linked to each other via a 4-(ethoxymethyl)-1-(phenoxyethyl)-1,2,3-triazole unit. It was found that efficient excitation energy transfer (EET) from the initially photoexcited BDP moiety to the PDI chromophore in its ground state resulted in strong quenching of the BDP first excited singlet state as well as in the appearance of the PDI fluorescence. The efficiency of EET was calculated to be 0.99 and the rate of this process was found to be 1.85 × 1010 s−1.

This work reports on the prospects of using luminescence spectroscopy as a non-destructive method for the characterization of ethylene vinyl acetate copolymer (EVA) crosslinking in photovoltaic (PV) modules. Luminescence has the potential to be easily applied in-line for monitoring purposes, e.g. during manufacturing. We investigate the correlation of luminescence, Raman spectroscopy and differential scanning calorimetry with the EVA crosslinking. We show that all these methods, including the luminescence method, show a good correlation with the hold time during the lamination process. Furthermore, time-dependent luminescence measurements are introduced. These make use of the fact that the luminescence decreases upon the ultraviolet irradiation during the measurement. In contrast to steady-state luminescence, this facilitates measurements that are inherently less dependent on possible interfering signal artifacts, as these may occur in industrial PV modules due to other components of the PV module.

Two commercial polyethylene grades were exposed to water at elevated temperatures and enhanced oxygen pressure. To characterize their aging behavior laser-induced photoluminescence spectroscopy was applied. Additionally, aging characterization was performed by established methods such as tensile testing, infrared (IR) spectroscopy, high performance liquid chromatography (HPLC), differential scanning calorimetry (DSC) and UV–VIS spectroscopy. During the initial stages of aging, the overall concentration of phenolic antioxidants as well as oxidation onset temperatures decreased exponentially. Simultaneously, significant discoloration due to the formation of conjugated degradation products from phenolic antioxidants (e.g., quinone methides) was detected. After the consumption of antioxidants, photoluminescence started to grow continuously presumably due to the formation of photoluminescent unsaturated carbonyls. In the final stages of aging, embrittlement of the materials as characterized by the degradation of mechanical properties (i.e., loss in ductility) coincided with rising carbonyl index values as well as an increase in crystallinity due to chemicrystallization. Between integrated photoluminescence intensity and carbonyl index, a linear correlation was established. In the induction period, the photoluminescence method exhibited a significantly higher sensitivity to reflect aging induced material changes.

Two commercial polyethylene grades were oven-aged at 95 °C and 115 °C for more than 1000 h. Aging characterization was performed by laser-induced photoluminescence spectroscopy ( λ Ex = 375 nm), laser confocal microscopy, infrared (IR) spectroscopy, high performance liquid chromatography, differential scanning calorimetry and tensile testing. Photoluminescence increased significantly upon oven-aging, especially at 115 °C. The maximum of emission was around 450 nm. Decreasing oxidation onset temperatures (DSC) and stabilizer concentrations (HPLC) indicate oxidation-induced changes in the materials that are in agreement with increasing photoluminescence. IR spectroscopy and tensile testing results showed no global oxidative degradation and no premature failure. Hence, the materials were still in the induction period of oxidative degradation. The evolution of photoluminescence is presumably related to the formation of oxygenated groups like α,β-unsaturated carbonyl groups. The investigations clearly indicated that photoluminescence spectroscopy is a sensitive method to monitor aging-induced changes within the induction period.

In view of increasing demands for efficient photosensitizers for photodynamic therapy (PDT), we herein report the synthesis and photophysical characterizations of new chlorin e6 trimethyl ester and protoporphyrin IX dimethyl ester dyads as free bases and Zn(II) complexes. The synthesis of these molecules linked at the β-pyrrolic positions to pyrano[3,2-c]coumarin, pyrano[3,2-c]quinolinone, and pyrano[3,2-c]naphthoquinone moieties was performed by using the domino Knoevenagel hetero Diels-Alder reaction. The α-methylenechromanes, α-methylenequinoline, and ortho-quinone methides were generated in situ from a Knoevenagel reaction of 4-hydroxycoumarin, 4-hydroxy-6-methylcoumarin, 4-hydroxy-N-methylquinolinone, and 2-hydroxy-1,4-naphthoquinone, respectively, with paraformaldehyde in dioxane. All the dyads as free bases and as Zn(II) complexes were obtained in high yields. All new compounds were fully characterized by 1D and 2D NMR techniques, UV/Vis spectroscopy, and HRMS. Their photophysical properties were evaluated by measuring the fluorescence quantum yield, the singlet oxygen quantum yield by luminescence detection, and also the triplet lifetimes were correlated by flash photolysis and intersystem crossing (ISC) rates. The fluorescence lifetimes were measured by a time-correlated single photon count (TCSPC) method, fluorescence decay associated spectra (FDAS), and anisotropy measurements. Magnetic circular dichroism (MCD) and circular dichroism (CD) spectra were recorded for one Zn(II) complex in order to obtain information, respectively, on the electronic and conformational states, and interpretation of these spectra was enhanced by molecular orbital (MO) calculations. Electrochemical studies of the Zn(II) complexes were also carried out to gain insights into their behavior for such applications.

The photodynamic effect, originally used in photodynamic therapy (PDT) for the treatment of different diseases, e.g. of cancer, has recently been introduced for the inactivation of bacteria. Mold fungi, which provoke health problems like allergies and diseases of the respiratory tract, are even more resistant and their biology is also very different. This study presents the development of four new photosensitizers, which, in combination with low doses of white light, inhibit the germination of mold fungi spores. Two of them even cause lethal damage to the conidia (spores) which are responsible for the spreading of mold fungi. The photoactivity of the newly synthesized corroles was obtained by their application on three different mold fungi: Aspergillus niger, Cladosporium cladosporoides, and Penicillium purpurgenum. To distinguish between inactivation of germination and permanent damage, the fungi were first incubated under illumination for examination of photosensitizer-induced growth inhibition and then left in darkness to test the survival of the conidia. None of the compounds displayed dark toxicity, but all of them attenuated or prevented germination when exposed to light, and the positively charged complexes induced a complete damage of the conidia.

New flavonoid–porphyrin conjugates were synthesized using the cross-coupling Buchwald–Hartwig amination for the coupling of flavonoid and porphyrin moieties. A unique di-substituted flavone–porphyrin conjugate was also synthesized under similar reaction conditions for the first time. All the conjugates were fully characterized by NMR spectroscopy. The photophysical properties namely fluorescence and singlet oxygen production were evaluated considering their use for photodynamic therapy applications.

Click chemistry has been successfully applied to prepare a conjugate of zinc(II) porphyrin with four boron dipyrromethene moieties. Upon excitation at the latter, an efficient excitation energy transfer to the porphyrin core occurs with an energy transfer quantum yield of 0.98, making this conjugate a promising light-harvesting system.

Facile, one-pot conversion of free base 5,10,15-tris(pentafluorophenyl)corrole, (H3)tpfc, into the coinage metal complexes of 2,3,17,18-tetraiodo-5,10,15-tris(pentafluorophenyl)corrole, (I4-tpfc)M (M = Cu, Ag, Au), is reported. The iodination/metalation procedures provide much higher yields and larger selectivity than both conceivable stepwise syntheses. Photophysical analysis shows that the gold(III) complex (I4-tpfc)Au displays phosphorescence at room temperature and a substantial quantum yield for singlet oxygen formation.