Synthetic pathways to water-soluble phthalocyanines and close analogs

Generation of reactive oxygen species (ROS) is the hallmark of important biological processes and photodynamic therapy (PDT), where ROS production results from in situ illumination of certain dyes. Here we test the hypothesis that the yield, fate, and efficacy of the species evolved highly depend on the dye's environment. We show that Pd−bacteriopheophorbide (Pd−Bpheid), a useful reagent for vascular targeted PDT (VTP) of solid tumors, which has recently entered into phase II clinical trials under the code name WST09 (trade name TOOKAD), forms appreciable amounts of hydroxyl radicals, superoxide radicals, and probably hydrogen peroxide in aqueous medium but not in organic solvents where singlet oxygen almost exclusively forms. Evidence is provided by pico- and nanosecond time-resolved spectroscopies, ESR spectroscopy with spin-traps, time-resolved singlet oxygen phosphorescence, and chemical product analysis. The quantum yield for singlet oxygen formation falls from 1 in organic solvents to 0.5 in membrane-like systems (micelles or liposomes), where superoxide and hydroxyl radicals form at a minimal quantum yield of 0.1%. Analysis of photochemical products suggests that the formation of oxygen radicals involves both electron and proton transfer from 3Pd−Bpheid at the membrane/water interface to a colliding oxygen molecule, consequently forming superoxide, then hydrogen peroxide, and finally hydroxyl radicals, with no need for metal catalysis. The ability of bacteriochlorophyll (Bchl) derivatives to form such radicals upon excitation at the near infrared (NIR) domain opens new avenues in PDT and research of redox regulation in animals and plants.

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The microenvironment effect on the generation of reactive oxygen species by Pd-bacteriopheophorbide.

Optical sensor development has been pursued over past 25 years, which has also seen development of novel chemistries, materials, sensor designs and optical instrumentation. In addition, novel signal and data processing techniques have been adopted in the sensor development. New techniques and materials in chemical and biological sensing have set further stages of advanced research. One of the most recent technological advances in this area has been the development of optical nanosensors, which are sensors with dimensions on the nanometer scale. Nanosensors of various types (e.g. optical, electrochemical) have been published in the literature over the past decade. Optical nanosensors, like the larger and macro scale sensors, can be either chemical or biological, depending on the type of probe used. Both types of sensors have been studied to provide a reliable method of monitoring various chemicals in microscopic environments and have been used to detect molecules within single cells. The field of nanosensing is relatively new and reports in the literature presenting any problems associated with such a scale of analysis are sparse. This paper will briefly review some of the current developments in the field of optical nanosensors.

Optical sensors

The synthesis, photophysical and photochemical properties of the 4-({3,4,5-tris-[2-(2-ethoxyethoxy)ethyloxy]benzyl}oxy) and 4-({3,4,5-tris-[2-(2-ethoxyethoxy)ethyloxy]benzyl}thio) zinc(II) phthalocyanines are reported for the first time. The new compounds have been characterized by elemental analysis, IR, 1H and 13C NMR spectroscopy, electronic spectroscopy and mass spectra. General trends are described for photodegradation, singlet oxygen, fluorescence and triplet excited state quantum yields, and triplet state and fluorescence lifetimes of these compounds in dimethylsulfoxide (DMSO). The fluorescence of the complexes was quenched by benzoquinone (BQ). The effects of the substitution on the photophysical and photochemical parameters of the zinc(II) phthalocyanines (6, 7 and 8) are also reported. Photophysical and photochemical properties of phthalocyanine complexes are very useful for PDT applications. The substituted Zn(II) phthalocyanines showed high triplet and singlet oxygen quantum yields. High singlet oxygen quantum yields are very important for Type II mechanism. Thus, these complexes show potential as Type II photosensitizers.

Synthesis, photophysical and photochemical properties of substituted zinc phthalocyanines

Effects of substituents and solvents on the photochemical properties of zinc phthalocyanine complexes and their protonated derivatives

Triplet state formation (Φisc) and properties (eT-T, τT) of phthalocyanine (HPC) and zinc phthalocyanine (ZnPC) have been characterized in homogeneous solutions (1-chloronaphthalene, 1-propanol) and in microemulsion by investigating the variation of the transient optical density as a function of the intensity of the exciting laser. Experimental results follow the theoretically predicted dependence only for very low intensities of the exciting pulse. At higher intensities, a more complicated scheme of primary reactions has to be taken into account, implicating qualitative restrictions in the application of saturation experiments. The observed transients at high-intensity excitation are interpreted as being perturbed by aggregational phenomena.

Patrice Jacques

Papers

Laser Flash Photolysis of Phthalocyanines in Solution and Microemulsion

Laser flash photolysis of phthalocyanines in solution and microemulsion