Fully Protected Glycosylated Zinc (II) Phthalocyanine Shows High Uptake and Photodynamic Cytotoxicity in MCF‐7 Cancer Cells

Phthalocyanine photosensitizers are effective in anticancer photodynamic therapy (PDT) but suffer from limited solubility, limited cellular uptake and limited selectivity for cancer cells. To improve these characteristics, we synthesized isopropylidene‐protected and partially deprotected tetra β‐glycosylated zinc (II) phthalocyanines and compared their uptake and accumulation kinetics, subcellular localization, in vitro photocytotoxicity and reactive oxygen species generation with those of disulfonated aluminum phthalocyanine. In MCF‐7 cancer cells, one of the compounds, zinc phthalocyanine {4}, demonstrated 10‐fold higher uptake, 5‐fold greater PDT‐induced cellular reactive oxygen species concentration and 2‐fold greater phototoxicity than equimolar (9 μm ) disulfonated aluminum phthalocyanine. Thus, isopropylidene‐protected β‐glycosylation of phthalocyanines provides a simple method of improving the efficacy of PDT.     

About the plausible contribution of field ionization in the mechanism of the formation of dyes of ions under conditions of laser desorption/ionization from a nanostructurized graphite surface

An approach is proposed for the estimation of the contribution of field ionization (FI) to the mechanism of dye ion formation under the conditions of laser desorption/ionization (LDI) from a nanostructurized graphite surface. As test systems, rough graphite layers with dyes, e.g., imidazophenazine derivatives applied to them were chosen; these ensure FI in a strong electric field. The dyes form three neutral precursors upon reduction and various types of ions in different ionization methods. It was found that the mass distribution within the group of peaks formed by the initial dye molecule and the products of its reduction in the positive ion mode upon LDI from a rough graphite surface is shifted to lower masses by one atomic mass unit in comparison to the distribution recorded for LDI from a smooth metal support. The analysis of plausible pathways of ion formation has shown that such a shift may be due to the superposition of ions formed by the FI mechanism on a graphite substrate with a number of ions formed by protonation in LDI with no dependence on the support type. In the negative ion mode, the registration of LDI dye spectra succeeded only if the graphite substrates used favored negative FI and electron emission enhanced by the field.     

Sensitivity of redox reactions of dyes to variations of conditions created in mass spectrometric experiments

Redox behaviour of four imidazophenazine dye derivatives under mass spectrometric conditions of matrix-assisted laser desorption/ionization (MALDI), laser desorption/ionization (LDI) from metal and graphite surface, electrospray, low temperature secondary ion mass spectrometry (LT SIMS) and fast atom bombardment (FAB) was studied and distinctions in the reduction-dependent spectral patterns were analyzed from the point of view of different quantities of protons and electrons available for reduction in different techniques. The reduction products [M + 2H](+*), [M + 3H](+) and M(-*), [M + H](-) were observed in the positive and negative ion modes, respectively, which permitted to suggest independent occurrence of reduction and protonation/deprotonation processes. LDI from graphite substrate was the only technique that allowed us to obtain abundant negative ions of all dye derivatives. The yield of field ionization (FI) or field desorption (FD) mechanism to ion formation under LDI from rough graphite surface has been addressed. The sensitivity of reduction of the dyes to variation of reduction-initiating agents confirms high redox activity of the dyes essential for their functioning in natural and artificial systems.     

Synthesis and structure of the first representative of pentacoordinate C,O-chelates with a dipeptide fragment,the fluorosilane Ts—Gly—(S)-Pro—N(Me)CH2SiMe2F

A reaction of bicyclic 2-sila-5-piperazinone, 2,2,4-trimethyl-1,4-diaza-2-silabicyclo-[4.3.0]nonan-5-one containing a proline moiety, and N-tosylglycine acyl chloride with subsequent hydrolysis of the primary unstable product to the intermediate disiloxane and its treatment with BF₃?OEt₂ furnished a first representative of pentacoordinate C,O-chelate halosilanes with a dipeptide fragment, namely, Ts—Gly—(S)-Pro—N(Me)CH₂SiMe₂F.

     

Chemically modified porous silicon for laser desorption/ionization mass spectrometry of ionic dyes

Desorption/ionization on silicon (DIOS) mass spectra of model ionic dyes methylene blue (MB⁺Cl^?) and methyl orange (Na⁺MO^?) were studied using p⁺ type‐derived porous silicon (PS) free layers. As‐prepared PS (PS‐H), the PS thermally oxidized at 300 °C (PS‐OX), PS with chemically grafted cation‐exchanging alkylsulfonic acid (PS‐SO₃H) and anion‐exchanging propyl‐octadecyldimethylammonium chloride (PS‐ODMA⁺Cl^?) groups was tested as ionization platforms. Two mechanisms of the methylene blue desorption/ionization were found: (1) the formation of [MB + H]^+? ion due to the reduction/protonation of MB⁺, which is predominant for PS‐H and PS‐OX platforms and (2) direct thermal desorption of the MB⁺ cation, prevailing for PS‐SO₃H. The fragmentation of the cation is significantly suppressed in the latter case. The samples of PS‐SO₃H and PS‐ODMA⁺ Cl^? efficiently adsorb the dyes of the opposite charge from their solutions via the ion‐exchange. Consequent DIOS MS studies allow to detect only low fragmented ions (MB⁺ and MO^?, respectively), demonstrating the potential of the ion‐exchange adsorption combined with DIOS MS for the analysis of ionic organic compounds in solutions. Copyright © 2009 John Wiley & Sons, Ltd.