Wavelength-dependent properties of photodynamic therapy using hypericin in vitro and in an animal model

Wavelength effects in photodynamic therapy (PDT) with hypericin (HY) were examined in a C26 colon carcinoma model both in vitro and in vivo. Irradiation of HY-sensitized cells in vitro with either 550 or 590 nm caused the loss of cell viability in a drug- and light-dose-dependent manner. The calculated ratio of HY-based PDT (HY-PDT) efficiencies at these two wavelengths was found to correlate with the numerical ratio of absorbed photons at each wavelength. In vivo irradiation of C26-derived tumors, 6 h after intraperitoneal administration of HY (5 mg/kg), caused extensive vascular damage and tumor necrosis. The depth of tumor necrosis (d) was more pronounced at 590 than at 550 nm and increased when the light dose was raised from 60 to 120 J/cm2. The maximal depths of tumor necrosis (at 120 J/cm2) were 7.5+/-1.5 mm at 550 nm and 9.9+/-0.8 mm at 590 nm. Both values are rather high in view of the limited penetration of green-yellow light into the tissue. Moreover, the depth ratio, d590/d550 = 1.3 (P < 0.001), is smaller than expected considering the 2.2-fold lower HY absorbance and the 1.7-fold lower tissue penetration of radiation at 550 than at 590 nm. This finding indicates that in vivo the depth at which HY-PDT elicits tumor necrosis is not only determined by photophysical considerations (light penetration, number of absorbed photons) but is also influenced significantly by other mechanisms such as vascular effects. Therefore, despite the relatively short-wavelength peaks of absorption, our observations suggest that HY is an effective photodynamic agent that can be useful in the treatment of tumors with depths in the range of 1 cm.     

Variable Mott-Schottky plots acquisition by potentiodynamic electrochemical impedance spectroscopy

Potentiodynamic electrochemical impedance spectroscopy provides extraction of potential-dependent space charge layer capacitance from potentiodynamic impedance spectra of non-stationary semiconductor–electrolyte interface. The new technique has been applied for acquisition of Mott-Schottky plots of cathodically treated TiO₂ anodic films. Cathodic treatment in 1 M H₂SO₄ increases donor density and flat band potential of TiO₂. Freshly doped films show hysteresis in the space charge layer capacitance in cyclic potential scans. The subsequent cycling eliminates the hysteresis but preserves the greater part of the doping effect. Presented at the 4th Baltic Conference on Electrochemistry, Greifswald, 13–16 March 2005     

Non-covalent assemblies of negatively charged boronated porphyrins with different cationic moieties

A unique approach to non-covalent electron and energy transfer is described that is based on the formation of salt bridges between oppositely charged porphyrin units. A new class of electrostatically linked dimeric and pentameric porphyrins was synthesized by interaction of novel anionic boron containing porphyrins such as 5-(benzamidodecahydro-closo-dodecaborate)-10,15,20-triphenylporphyrin (N1) and meso-tetrakis-benzamidodecahydro-closo-dodecaborate)porphyrin (N2) and a variety of cationic meso-tetraarylporphyrin units. A bipyridine linked dimer (N1 · bpy · N1) was also prepared by employing N,N′-dimethyl-4,4′-bipyridinium (bpy) as a spacer between two mono-anionic species. A quinone-porphyrin dyad was also prepared for electron or energy transfer demonstration. All the synthesized assemblies were characterized by NMR, IR, UV-Vis, and mass spectroscopy. Significant spectral changes occurred in the absorption spectra of these non-covalent porphyrin assemblies compared to those of the reference monomers, indicating the presence of electronic interaction between the adjacent porphyrin units. Resonance light scattering was also used to study the formation of these assemblies in solution.     

Synthesis and characterization of a novel functionalized azanonaborane cluster for boron neutron capture therapy

The reactivity of an azanonaborane cluster containing free amino groups {H2N(CH2)4H2NB8H11NH(CH2)4NH2} towards ketones and aldehydes is investigated. In a one step reaction, the reductive amination of some ketones and aldehydes (namely acetone, benzaldehyde, 3-hydroxybenzaldehyde, 4-hydroxybenzaldehyde, 4-nitrobenzaldehyde, 4-acetoxybenzaldehyde, and 4-acetamidobenzaldehyde) with an azanonaborane cluster in the presence of H3BNH2(CH2)4NH2 gives monoalkylamino derivatives of the azanonaborane cluster {RHN(CH2)4H2NB8H11NH(CH2)4NHR} where (R =(Me)2CH-, C6H5CH2-, 3-OHC6H4CH2-, 4-OHC6H4CH2-, 4-NO2C6H4CH2-, 4-MeOCOC6H4CH2-, or 4-NH2COC6H4CH2-). The functionalized derivatives of the {B8N} cluster can be used in boron neutron capture therapy for tumors (BNCT). Similarly, the reductive amination of 5-(4"-formylphenyl)-10,15,20-triphenylporphyrin with the {B8N} cluster gave a porphyrin bearing azanonaborane cluster, while a porphyrin dimer linked by an azanonaborane moiety was obtained following the same method, starting with a 2:1 molar ratio of porphyrin:{B8N} cluster. 5,10,15,20-Tetraformylphenylporphyrin gave the chance to increase the percentage of boron in the resulting boronated porphyrin, which is considered an important factor for a BNCT delivery agent. With these compounds, the cell toxicity using V79 cells was carried out to determine whether these compounds would have favorable biological properties.     

The chemistry of the azanonaborane cluster RNH2---B8H11NHR

The preparation and properties of the R¹R²NH---B₈H₁₁NHR cluster are described. The cluster is stable to aqueous solutions and can be made water-soluble by the introduction of a few hydrophilic groups. This makes the cluster a good candidate as the boron moiety in compounds for boron neutron capture therapy. The chemistry of the cluster preparation, the stability of the cluster, and conditions for reactions of the organic moieties are reviewed. Pyridine derivatives of the cluster show electronic interaction between the cluster and the pyridine.     

Influence of Co amount on the efficiency of energy absorption of Fe-Co ferrite nanoparticles

We present the chemical synthesis, structural characterization and efficiency of AC field energy absorption of Fe-Co ferrite particles sized between 35 and 100 nm and containing different cobalt amounts up to 3 wt%. Dynamic magnetic measurements in an AC field with frequency of 430 Hz and amplitude of up to 1200 Oe were performed for both solid and liquid dispersions of obtained particles. The energy absorption per one field cycle in function of the field amplitude and Co content was always bigger in liquid systems, under the same conditions, than in solid systems. The obtained results are of significance for the technology of low-frequency ferromagnetic hyperthermia of tumors.     

The impact of the natural sciences on archaeology

This article reviews some of the applications of physics to the solution of archaeological problems. The use of magnetic, resistivity and electromagnetic surveying techniques for the location of buried features is described. Various methods of age determination are outlined while the problems associated with radiocarbon dating of organic material and thermoluminescent dating of pottery are discussed in detail. The techniques, including petrological examination, chemical analysis and isotopic analysis, employed in the physical examination of archaeological artefacts are described. Examples of the application of these techniques in establishing the source of the raw materials used in pottery, metal and stone implements and in elucidating the techniques of manufacture of pottery and metal objects are also given.     

Azanonaboranes containing imidazole derivatives for boron neutron capture therapy: synthesis, characterization, and in vitro toxicity evaluation

A number of azanonaboranes containing imidazole derivatives have been synthesized by a ligand-exchange reaction. The exo-NH(2)R group of the azanonaborane of the type [(RH(2)N)B(8)H(11)NHR] can be exchanged by one hetero-nitrogen atom of the imidazole ring. In the case of histamine, the exchange takes place on the aliphatic amino group, the hetero-nitrogen atom of the imidazole ring or both of them. The products were confirmed by NMR, IR spectroscopy, elemental analysis, and mass spectrometry. The electron-withdrawing effect of the nitro group in 2-nitroimidazole is the main hindrance to achieve the exchange reaction. In vitro experiments were performed with B16 melanoma cells. A comparison of the biological properties of the products in which the B(8)N cluster is connected to the hetero-nitrogen atom of imidazole ring or the aliphatic NH(2) group showed that incorporation of B(8)N cluster unit into primary amino group increases the compound's toxicity. In contrast, this specificity for cytotoxicity effect was not observed in the case of histamine containing two B(8)N clusters which was relatively nontoxic and did not inhibit colony formation up to concentrations of 2 mM.     

Phenolic compounds,essential oil composition,and antioxidant activity of Angelica purpurascens (Avé-Lall.) Gill

In this study, methanol extracts (MEs) and essential oil (EO) of Angelica purpurascens (Avé-Lall.) Gill obtained from different parts (root, stem, leaf, and seed) were evaluated in terms of antioxidant activity, total phenolics, compositions of phenolic compound, and essential oil with the methods of 2,2-azino-bis(3ethylbenzo-thiazoline-6-sulfonic acid (ABTS•⁺), 2,2-diphenyl-1-picrylhydrazil (DPPH•) radical scavenging activities, and ferric reducing/antioxidant power (FRAP), the Folin–Ciocalteu, liquid chromatography−tandem mass spectrometry (LC−MS/MS), and gas chromatography-mass spectrometry (GC−MS), respectively. The root extract of A. purpurascens exhibited the highest ABTS•⁺, DPPH•, and FRAP activities (IC₅₀: 0.05 ± 0.0001 mg/mL, IC₅₀: 0.06 ± 0.002 mg/mL, 821.04 ± 15.96 µM TEAC (Trolox equivalent antioxidant capacity), respectively). Moreover, EO of A. purpurascens root displayed DPPH• scavenging activity (IC₅₀: 2.95 ± 0.084 mg/mL). The root extract had the highest total phenolic content (438.75 ± 16.39 GAE (gallic acid equivalent), µg/mL)). Twenty compounds were identified by LC−MS/MS. The most abundant phenolics were ferulic acid (244.39 ± 15.64 μg/g extract), benzoic acid (138.18 ± 8.84 μg/g extract), oleuropein (78.04 ± 4.99 μg/g extract), and rutin (31.21 ± 2.00 μg/g extract) in seed, stem, root, and leaf extracts, respectively. According to the GC−MS analysis, the major components were determined as α-bisabolol (22.93%), cubebol (14.39%), α-pinene (11.63%), and α-limonene (9.41%) among 29 compounds. Consequently, the MEs and EO of A. purpurascens can be used as a natural antioxidant source.