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.     

Mono- and multimolecular Langmuir-Blodgett films as protective coatings for friction surfaces

Tribological properties of monomolecular Langmuir-Blodgett films formed from behenic acid, dimethyl octadecylmalonate, 2,4-heneicosanedione, and its copper complex were studied and compared with those of a self-arranged monolayer of octadecyltrichlorosilane. In the micrometer contact range, in friction of a modified silicon surface with a steel ball (indentor), the monomolecular Langmuir-Blodgett films under consideration surpass in the wear resistance the chemisorbed monomolecular octadecyltrichlorosilane film by a factor of 40. The stability of Lamgmuir-Blodgett films in friction correlates with the density of molecular packing on the surface. The friction and wear of Langmuir-Blodgett films are accounted for by the difference in the density of molecular packing of the films under consideration, and also by the transfer of the film substance between the friction surfaces.     

<Emphasis Type="Italic">N</Emphasis>-benzyl derivatives of valine esters

The reactions of methyl and ethyl esters of valine with m-bromobenzaldehyde and p-chlorobenzaldehyde in absolute methanol in the presence of magnesium sulfate yielded the corresponding azomethines (CH₃)₂CHCH(COOR¹)N=CHR² (R¹ = CH₃, C₂H₅; R² = 3-BrC₆H₄, 4-ClC₆H₄); their reduction with sodium borohydride gave N-benzyl derivatives of valine esters, (CH₃)₂CHCH(COOR¹)NHCH₂R².Translated from Zhurnal Obshchei Khimii, Vol. 74, No. 11, 2004, pp. 1855–1857.Original Russian Text Copyright © 2004 by Yakubovich, Zhavnerko, Shirokii, Knizhnikov.This revised version was published online in April 2005 with a corrected cover date.     

Functionalization of (CdSe)ZnS nanoparticles in reverse micelles of Aerosol OT

A method is optimized for in situ functionalization and activation of (CdSe)ZnS nanoparticles in reverse micelles of Aerosol OT, as well as their conjugation with antibodies. The efficiency of particle functionalization depends on the method of micellar solution formation. Fluorescence remains practically unchanged, provided that NH₂ groups of polymers bonded to the nanoparticles are activated by glutaric aldehyde. All operations of antibody conjugation should be carried out in reverse micelles for the maximum preservation of the fluorescence properties of the particles. Nanoparticles are isolated from reverse micelles using a mixture of acetone with a solution composed of 50 mM NaHCO₃ and 200 mM NaCl. The optimum medium for dissolving the precipitate of the particles consists of NaHCO₃ (50 mM), bovine serum albumin (0.1%), and Twin 85 (0.05%). The modified particles were subjected to photoactivation in an aqueous medium at room temperature and daylight.     

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.     

Features of the local immobilization of NADPH-cytochrome P450 reductase and cytochrome b<Subscript>5</Subscript> on a solid surface

Using the methods of microcontact printing and atomic force microscopy, we studied a possibility of specific “protein-protein” interactions in the processes of local immobilization of cytochrome b₅ and NADPH-cytochrome P450 reductase on the surface of hydrophilic silicone. It is shown that the formation of protein complexes is possible only at a certain orientation of the molecules defined by the sequence of adsorption of biopolymers.