The effect of glucose and temperature on the in vivo efficiency of photochemotherapy with meso-tetra-hydroxyphenyl-chlorin

Balb/c athymic nude mice bearing WiDr human colon adenocarcinoma have been employed to investigate the effect of glucose administration, cooling or slight heating on the anti-tumor activity of photochemotherapy (PCT) with meso-tetra-hydroxyphenyl-chlorin (mTHPC). An apparent delay in the tumor growth is found by combining PCT with either single or multiple injections of glucose. The anti-tumor effect of PCT is slightly enhanced by cooling the tumor to 5°C. Cooling also enhances the efficiency of PCT and glucose injection combined. Heating the tumor to 37°C has no significant effect on either PCT alone or on the combination of PCT and glucose injection. Furthermore, the kinetics of the accumulation of mTHPC in tissue have been studied. Single or multiple injections of glucose have an enhancing effect on the accumulation of mTHPC in the tumor.     

Polymorphic crystalline forms of 8OCB

For most alkoxycyanobiphenyls (3OCB, 5OCB, 6OCB, 7OCB and 9OCB) it has been observed that slow or delayed cooling gave rise to a lower melting crystalline polymorphic form which then slowly converted into the higher melting stable crystalline structure. Although under slow evaporation from a solvent, polymorphic crystalline structures were observed also for 8OCB, a polymorphism on cooling like that in other nOCBs has not previously been reported. We have now observed that 8OCB also shows polymorphism, which brings it into line with the other homologues. On keeping the material between 35 and 38 °C after it was cooled from above the melting point of the stable crystal form (55 °C), regular platelets grow usually from one point and fill the whole sample. The texture is stable for weeks at room temperature. Upon heating it shows a melting point at 50 °C, i.e. 5 degrees below the stable crystalline melting point. It is interesting that all platelets are non-symmetric and have the same handedness.     

Outcome of mTHPC mediated photodynamic therapy is primarily determined by the vascular response

We have previously shown that the efficacy of photodynamic therapy (PDT) using the photosensitizer meso-tetra-hydroxyphenyl-chlorin (mTHPC) correlated with plasma drug levels at the time of illumination rather than drug levels in human tumor xenografts or mouse skin. These results suggested that vascular-mediated effects could be important determinants of PDT response in vivo. In the present study we further investigated the relationship between PDT response, mTHPC pharmacokinetics and the localization and extent of vascular damage induced in human squamous cell carcinoma xenografts (HNXOE). Plasma levels of mTHPC decreased exponentially with time after injection, whereas tumor drug levels remained maximal for at least 48 h. At 3 h after administration mTHPC was localized in the blood vessels, whereas at later times it was distributed throughout the whole tumor. Illumination at 3 h after mTHPC, which resulted in 100% long-term tumor cure, led to a marked reduction of vascular perfusion and increased tumor hypoxia at 1 h after treatment. Illumination at 48 h resulted in rapid regrowth of most tumors and only 10% cure. This protocol did not affect a significant decrease in vascular perfusion or increase in tumor hypoxia. These data show that optimal responses to mTHPC-mediated PDT were primarily dependent on the early vascular response, and that plasma drug levels at the time of illumination could predict this relationship.     

TIME-DEPENDENT PHOTODYNAMIC DAMAGE TO BLOOD VESSELS: CORRELATION WITH SERUM PHOTOSENSITIZER LEVELS

Abstract— We have used the technique of dynamic capillaroscopy to study the time-course of photo-dynamic vascular occlusion in mice injected intraperitoneally with either of two photosensitizers; hematoporphyrin esters (HPE) or meso -tetrahydroxyphenyl chlorin (mTHPC). The peak of vascular occlusion induced by HPE coincided in time with peak serum levels of this photosensitizer (about 3 h after injection). However, there was also a second peak of occlusive activity at about 12 h after injection, at which time serum HPE was falling monotonically. In the case of mTHPC, no peak of occlusive activity was seen at 3 h after injection, even though the serum levels of this photosensitizer, like those of HPE, were highest around this time. Instead, a steady rise in photosensitizing activity was observed, peaking at 11 h. This decoupling between serum drug levels and vascular photosensitization—partial for HPE and complete for mTHPC—suggests that direct photosensitization of endothelial cells is unlikely wholly to explain the vascular collapse. Instead, there must be either another compartment that accumulates photosensitizer more slowly and in which photodynamic activity has an indirect effect on the blood capillaries or a slow metabolic transformation of mTHPC into a more active sensitizer.     

Sunna 535-nm photo-fluorescent film dosimeter response to different environmental conditions

Evaluations on the influence of environmental variabilities on the red fluorescence component of the Sunna Model γ photo-fluorescent dosimeter^TM have previously been reported. This present paper describes the environmental effects on the response of the green fluorescence component of the same dosimeter, which is manufactured using the injection molding technique. The results presented include temperature, relative humidity, and light influences both during and after irradiation. The green fluorescence signal shows a significant dependence on irradiation temperature below room temperature at 1%/°C. Above room temperature (approximately 24–60°C), the irradiation temperature effect varies from −0.1%/°C to 1.0%/°C, depending on the absorbed dose level. For facilities with irradiation temperatures between 30°C and 60°C and absorbed dose levels above 10 kGy, irradiation temperature effects are minimal. Light-effects results indicate that the dosimeter is influenced by ultraviolet and blue wavelengths during irradiation as well as during the post-irradiation stabilization period (approximately 22 h), requiring the use of light-tight packaging. Results also show that the dosimeter exhibits negligible effects from ambient moisture during and after irradiation when in the range of 33–95% relative humidity.     

Preparation and liquid-crystalline properties of toluene-4-sulphonyl urethane of hydroxypropylcellulose

A novel liquid-crystalline polymer, the toluene-4-sulphonyl urethane of hydroxypropylcellulose (TSUHPC), was prepared through chemical modification of hydroxypropylcellulose (HPC) of M_w = 60000 g mol^-1. The resulting polymer was characterized by infrared spectroscopy, differential scanning calorimetry (DSC) and polarizing microscopy. It was found that thermotropic liquid crystal phases are formed between about 60°C and 110°C. Concentrated solutions of TSUHPC in acetone and N,N-dimethylacetamide exhibit cholesteric behaviour, at room temperature. When approaching the lyotropic mesophase to solid transition, either by cooling or by solvent evaporation, very interesting arborescent structures of a seemingly fractal nature may be observed, depending on the kinetics of the transition. A banded texture can be observed when the polymer is sheared near the transition to the isotropic phase.     

Unusual Photoinduced Response of mTHPC Liposomal Formulation (Foslip)

Liposomal formulations of meso-tetra(hydroxyphenyl)chlorin (mTHPC) have already been proposed with the aim to optimize photodynamic therapy. Spectral modifications of these compounds upon irradiation have not yet been investigated. The objective of this study was to evaluate photobleaching properties of mTHPC encapsulated into dipalmitoylphosphatidylcholine (DPPC) liposomes, Foslip. Fluorescence measurements in DPPC liposomes with different DPPC:mTHPC ratios demonstrated a dramatic decrease in fluorescence anisotropy with increasing local mTHPC concentration, thus suggesting strong interactions between mTHPC molecules in lipid bulk medium. Exposure of Foslip suspensions to small light doses (<50 mJ/cm²) resulted in a substantial drop in fluorescence, which, however, was restored after addition to the sample of a non-ionic surfactant Triton X-100. We attributed this behavior to photoinduced fluorescence quenching. This effect depended strongly on the molar DPPC:mTHPC ratio and was revealed only for high local mTHPC concentrations. The results were interpreted supposing energy migration between closely located mTHPC molecules with its subsequent dissipation by the molecules of photoproduct acting as excitation energy traps. We further assessed the effect of photoinduced quenching in plasma protein solution. Relatively slow kinetics of photoinduced Foslip response during incubation in the presence of proteins was attributed to mTHPC redistribution from liposomal formulations to proteins. Therefore, changes in mTHPC distribution pattern in biological systems would be consistent with changes in photoinduced quenching and would provide valuable information on mTHPC interactions with a biological environment.     

Biodistribution and bioactivity of tetra-pegylated meta-tetra(hydroxyphenyl)chlorin compared to native meta-tetra(hydroxyphenyl)chlorin in a rat liver tumor model

It has been proposed that the construction of a photosensitizer-polymer conjugate would lead to an increased selective retention of the drug in tumor tissue resulting in an enhancement of selective tumor destruction by light in photodynamic therapy. In this study the kinetics of a tetra-pegylated derivative of meta-tetra(hydroxyphenyl)chlorin (mTHPC-PEG) were compared with those of native meta-tetra(hydroxyphenyl)chlorin (mTHPC) in a rat liver tumor model. In addition, the time course of bioactivity of both drugs was studied in normal liver tissue. Pegylation of mTHPC resulted in a two-fold increase in the plasma half-life time, a five-fold decrease in liver uptake and an increase in the tumor selectivity at early time intervals after drug administration. However, although mTHPC concentrations in liver decrease rapidly with time, mTHPC-PEG liver concentrations increased as a function of time. This led to a loss of tumor selectivity at all but the earliest time points, whereas with mTHPC tumor selectivity increased with time. For both drugs the time course of bioactivity in the liver parallels drug concentration levels with extensive necrosis after irradiation of mTHPC-PEG-sensitized liver tissue up to drug-light intervals of 120 h. It is concluded that on balance mTHPC-PEG does not appear to show any benefits over native mTHPC for the treatment of liver tumors, as normal liver tissue accumulates the compound. However, pegylation is a potentially promising strategy with an increase in tumor selectivity and reduced liver uptake if accumulation in the liver can be prevented.     

Thermokinetic studies for reactions of lanthanum(III) and nickel(III) oxides with barium perchlorate trihydrate

TG, DTG and DTA have been used in non-isothermal investigations of binary systems of Ni₂O₃ and La₂O₃ with barium perchlorate trihydrate, BP·3 H₂O, in various molar ratios, carried out under an air (static) atmosphere from ambient to 1000°C. Ni₂O₃ catalysed the dehydration process of BP·3 H₂O and lowered its T_f by 20°C. The discontinuity on the TG curve due to an incomplete perchlorate—chlorate reaction vanished in the presence of either of the oxides: a mechanism is proposed. La₂O₃ lowered T_f by 50°C; T_i for the decomposition of BP was lowered by 150 and 100°C in the presence of La₂O₃ and Ni₂O₃, respectively. X-Ray diffractometry did not reveal any reaction between BP and the two oxides. Kinetic parameters for the decomposition steps in the presence of either of the oxides have been determined.     

Temporally and spatially heterogeneous distribution of mTHPC in a murine tumor observed by two-color confocal fluorescence imaging and spectroscopy in a whole-mount model

Efficient intratumor delivery of anticancer drugs and photosensitizers is an important factor in the success of chemotherapy and photodynamic therapy, respectively. Unfortunately, their adequate and uniform intratumor distribution is impeded by several physiological barriers and by binding to tissue components. Measurement of gross tumor drug accumulation is a routine method of investigating the uptake and clearance of chemotherapy agents and photosensitizers but tells little about their extravascular spatial distribution. We use whole-mount two-color confocal fluorescence imaging and imaging spectroscopy of unprocessed excised murine tumor fragments to investigate the intratumor distribution of the photosensitizer meso-tetrahydroxyphenyl chlorin (mTHPC) as a function of distance from blood vessels perfused with 0.2 mum diameter fluorescent microspheres. Significant mismatches between drug and perfused vasculature are caused by heterogeneities in tumor blood supply. We describe complex microscopic mTHPC gradients that reverse dramatically relative to the perfused vasculature with time after injection. This imaging technique can be applied to screen the dynamic intratumor distribution of other fluorescent photosensitizers and anticancer drugs.     

Localization of tetra(m-hydroxyphenyl)chlorin (Foscan) in human healthy tissues and squamous cell carcinomas of the upper aero-digestive tract, the esophagus and the bronchi: a fluorescence microscopy study

To date, little is known about precise time-dependent distribution and histological localization of tetra(m-hydroxyphenyl)chlorin (mTHPC) in human healthy tissues and squamous cell malignancies in the upper aero-digestive tract. A fluorescence microscopy study was performed on 50 healthy tissue biopsies and on 13 tumors (graded from Tis to T1 SCC) from 30 patients. Tissue samples were taken between 4 h and 11 days following injection of 0.15 mg/kg mTHPC. A fairly comparable distribution pattern in various tissues was observed over time in different patients. Vascular localization of mTHPC fluorescence predominates at a short delay, whereas the dye is essentially located in the tumoral and healthy mucosa after longer delays. A much lower uptake and retention of mTHPC fluorescence was noted in striated muscle and cartilage as compared to neoplastic lesions. No significant selectivity was found between healthy and tumoral mucosa. The obtained data are important to confirm drug-light interval that have been selected for effective PDT for early SCC malignancies while minimizing the risks of over- or under-treatment. The low fluorescence level in striated muscle provides the opportunity to develop interstitial PDT as a treatment modality for invasive SCC of unfavorable locations in the oral cavity or pharynx, such as the base of the tongue.     

The synthesis and liquid crystal transition temperatures of some weakly polar nematic trans-4-substituted-cyclohexyl (E)-alk-2-enoates

The effect on the liquid crystal transition temperatures of introducing various groups (for example incorporating C=C, O, CO₂ and CO) into the terminal alkyl chain of a weakly polar model compound 1-[trans-4-(trans-4-propylcyclohexyl)cyclohexyl]pentane has been investigated systematically. Only the compound containing both an ester function and a trans-carbon-carbon double bond exhibited a wide-range nematic mesophase at elevated temperatures. Therefore, a wide variety of trans-4-substituted-cyclohexyl (E)-alk-2-enoates incorporating a carbon double bond with a trans-configuration (E) in the terminal alkyl chain has been synthesized. Nearly all the two-ring esters prepared exhibit a nematic phase over a wide temperature range (≤ 100°C) at elevated temperatures (≤ 200°C). The tendency to form smectic mesophases is often low. Comparisons with the corresponding derivatives incorporating either just a carboxy group (COO) or just a carbon-carbon double bond (C=C) in the same positions indicate that synergetic effects lead to broader nematic phases than would otherwise have been expected. The new compounds are easily prepared from known starting materials.     

Synthesis and mesogenic properties of diaromatic cyanates and isocyanates-monomers for liquid crystalline thermosets

Five pairs of mesogens with identical cores having either a cyanate or an isocyanate reactive terminal group have been synthesized. The monofunctional mesogens have a n-butoxy or a methoxy substituent as the second terminal group. The influence of the two isomeric OCN moieties on the formation of a mesophase and on the thermal transitions has been investigated. The mesophases observed were identified as nematic. A tremendous difference in the mesogenic power (stabilizing effect on a mesophase) has been found for the two reactive terminal groups. The isocyanates have lower melting points than the isostructural cyanates and clearing points which are approximately 30°C higher per isocyanate group, as compared to a cyanate moiety.     

Optical activity in CE6 A new metastable blue phase?

The optical rotation of a mixture of 60 per cent of chiral and 40 per cent of racemic CE6 as an 18 μm thick sample placed between glass plates treated with PI has been measured. This mixture exhibits one blue phase (BP1) on heating over a temperature range of about 0·1°C. On cooling the sample on the other hand, the BP region is expanded to 0·6°C and is divided into two regions. One region (BP1) (of range about 0·38°C below the isotropic-blue phase transition) shows two Bragg wavelengths which increase with decreasing temperature. For the second region (BPS) (of range about 0·22°C above the cholesteric-blue phase transition), one Bragg wavelength decreases with decreasing temperature, and a third Bragg wavelength appears. At constant temperature both phases remained stable for a period of several days.     

Effect of the TAT-RasGAP(317-326) peptide on apoptosis of human malignant mesothelioma cells and fibroblasts exposed to meso-tetra-hydroxyphenyl-chlorin and light

BACKGROUND: 5,10,15,20-Tetrakis(m-hydroxyphenyl)chlorin (mTHPC)-mediated photodynamic therapy (PDT) has shown insufficient tumor selectivity for the treatment of pleural mesothelioma. Tumor selectivity of mTHPC-PDT may be enhanced in the presence of the TAT-RasGAP(317-326) peptide which has the potential to specifically sensitize tumor cells to cytostatic agents. MATERIALS AND METHODS: H-meso-1 and human fibroblast cell cultures, respectively, were exposed to two different mTHPC doses followed by light delivery with and without TAT-RasGAP(317-326) administration. mTHPC was added to the cultures at a concentration of 0.04microg/ml and 0.10microg/ml, respectively, 24h before laser light illumination at 652nm (3J/cm(2), 40mW/cm(2)). TAT-RasGAP(317-326) was added to the cultures immediately after light delivery at a concentration of 20microM. The apoptosis rate was determined by scoring the cells displaying pycnotic nuclei. Cell viability was measured by using a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay. RESULTS: Light delivery associated with 0.04microg/ml mTHPC resulted in a significantly higher apoptosis rate in the presence of TAT-RasGAP(317-326) than without in H-meso-1 cells (p<0.05) but not in fibroblasts. In contrast, 1.0microg/ml mTHPC and light resulted in a significantly higher apoptosis rate in both H-meso-1 cells and fibroblasts as compared to controls (p<0.05) but the addition of TAT-RasGAP(317-326) did not lead to a further significant increase of the apoptosis rate of both H-meso-1 cells and fibroblasts as compared to mTHPC and light delivery alone. CONCLUSION: TAT-RasGAP(317-326) selectively enhanced the effect of mTHPC and light delivery on H-meso-1 cells but not on fibroblasts. However, this effect was mTHPC dose-dependent and occurred only at a low sensitizer dose.     

Development of liposomes containing ethanol for skin delivery of temoporfin: Characterization and in vitro penetration studies

The aim of this study was to develop ethanol-containing (3.3–20%, w/v) liposomes loaded with temoporfin (mTHPC), which presents a highly hydrophobic photosensitizer with low percutaneous penetration, and to investigate their skin penetration enhancing effect. Characterization parameters of liposomes were measured by photon correlation spectroscopy, lamellarity was analyzed by cryo-electron microscopy and mTHPC-content in formulations was determined spectrofotometrically. In order to assess the stability of mTHPC–liposomes at 4 and 23 °C, at predetermined time intervals characterization parameters and mTHPC-content were measured. The in vitro skin penetration of mTHPC was investigated using human abdominal skin mounted in Franz cells. The results indicated that mTHPC–liposomes were of a small particle size, small polydispersity index, negative surface charge, unilamellar or oligolamellar, and of a spherical or oval shape. All liposomes were stable during 12 months’ storage at 4 °C. Increasing the amount of ethanol in mTHPC–liposomes the skin deposition of mTHPC increased also. Liposomes without ethanol delivered the lowest amount of mTHPC into the skin, while liposomes containing 20% ethanol showed the highest penetration enhancement. In conclusion, mTHPC–liposomes containing 20% ethanol could be a promising tool for delivering temoporfin to the skin, which would be beneficial for the photodynamic therapy of cutaneous malignant or non-malignant diseases.     

Effect of radiation damage on luminescence of erbium-implanted SiO2/Si studied by slow positron beam

The effect of damage on 1.54 μm luminescence for 30 keV-Er-implanted SiO₂ films has been studied by positron annihilation and cathodoluminescence. It was found that S-parameter in the films decreased after implantation, indicating the suppression of positronium formation. The luminescence appeared with the recovery of the S-parameter after 600°C annealing. The intensity reached a maximum at 900°C annealing whereas the S-parameter did not change significantly. It seems that most damages recover at 600°C and thereafter Er ions transform to an optically active state at 900°C.     

The effect of humidity on dehydration behavior of nitrofurantoin monohydrate studied by humidity controlled simultaneous instrument for X-ray Diffractometry and Differential Scanning Calorimetry (XRD–DSC)

The dependence of thermal dehydration behavior of nitrofurantoin monohydrate on humidity was studied. Difference in observed crystallinity of resulting anhydrates under three humidity conditions is discussed in relation to the effect of water vapor molecules. Thermal dehydration of nitrofurantoin monohydrate was measured using a humidity controlled simultaneous measurement instrument for X-ray Diffractometry (XRD) and Differential Scanning Calorimetry (DSC) in dry, 27 °C 91% RH and 60 °C 90% RH nitrogen. Dehydration of nitrofurantoin in dry nitrogen gave a mixture of crystalline and amorphous anhydrates in the temperature range of 124–180 °C followed by crystallization around 185–190 °C. Whereas, dehydration in high humidity atmosphere (60 °C 90% RH or 17.7% H₂O–82.3% N₂) gave well crystallized anhydrate at 140 °C soon after dehydration. Dehydration in low humidity nitrogen (27 °C 91% RH or 3.2% H₂O–96.8% N₂) gave not totally crystalline anhydrate, which became pure crystalline at around 190 °C. The effect of high humidity on dehydration and crystallinity of the resulting anhydrate can be attributed to the role of water vapor molecules in two ways such as the acceleration of molecular mobility and high molecular diffusion rate of nitrofurantoin anhydrate, and the formation of hydrogen bonding bridges quickly connecting dehydrated molecules to one another.     

The effect of heat ageing on fracture toughness in uPVC pressure pipe

This paper reports a study of the effect of accelerated heat ageing in air on the fracture toughness of two uPVC pipes. The pipes were extruded at 179°C and 195°C respectively and curved fracture toughness specimens were aged at temperatures between 100 and 140°C. After testing at a crosshead rate of 1 mm/min, a similar activation energy of between 104 and 115 kJ/mol was calculated, for both pipes, from the variation of fracture toughness with ageing time and temperature. Extrapolation of the elevated-temperature data down to 20°C showed thermo-oxidative degradation to have a small effect on the fracture toughness during the expected service lifetime of 50–100 years.