Evaluation of the antineoplastic properties of the photosensitizer biscyanine in 2D and 3D tumor cell models and artificial skin models.

Background: Photodynamic Therapy (PDT) is a therapeutic modality that combines the application of a photoactive compound (photosensitizer, PS) with low-power light to generate reactive oxygen species in the target tissue, resulting in cytotoxic damage and cell death, while sparing adjacent tissues. The objective of this study was to evaluate the phototoxicity of a cyanine dye with two chromophores (biscyanines, BCD) in systems with varying levels of cellular organization, and we used the Photogem® (a photosensitizer approved by the Brazilian ANVISA agency for clinical use in Photodynamic Therapy) as a positive control.

Materials And Methods: The cytotoxicity of the compounds was assessed in vitro in 2D monolayers, 3D spheroid cultures, and artificial skin models.

Nonlinear van't Hoff Behavior in the Interaction of Two Water-Soluble Porphyrins with Bovine Serum Albumin (BSA).

Thermodynamic analysis of the binding process of water-soluble negatively charged -tetrakis(-sulfonatophenyl) (TPPS) and positively charged -tetrakis(4-methylpyridyl) (TMPyP) porphyrins with bovine serum albumin (BSA) at different temperatures was carried out based on the data of BSA quenching fluorescence by porphyrins. The comparison of binding constants ( ) shows that negatively charged TPPS possesses higher affinity to BSA than positively charged TMPyP. Thermodynamic characteristics of the binding process were obtained in accordance with the van't Hoff theory by processing nonlinear dependences of ln on inverse absolute temperature within the framework of two models: taking into account the dependence or independence of the change in the standard heat capacity (Δ ) on temperature.

Effect of Serum Albumin on Porphyrin-Quantum Dot Complex Formation, Characteristics and Spectroscopic Analysis.

The effect of bovine serum albumin (BSA) upon interaction between CdTe QD functionalized by 3-Mercaptopropionic Acid (CdTe-3-MPA QD) and two water soluble porphyrins: positively charged -tetra methyl pyridyl porphyrin (TMPyP) and negatively charged -tetrakis(p-sulfonato-phenyl) porphyrin (TPPS), was studied in function of pH using the steady-state and time resolved optical absorption and fluorescence spectroscopies. It was shown that, depending on the charge state of the components, interaction with albumin could either prevent the formation of the QD…PPh complex, form a mixed QD…PPh…BSA complex or not affect PPh complexation with QD at all. The obtained results may be of interest for application in photomedicine.

Effects of meso-tetrakis (4-sulfonatophenyl) porphyrin (TPPS) aggregation on its spectral and kinetic characteristics and singlet oxygen production.

The present work reports the effects of meso-tetrakis (4-sulfonatophenyl) porphyrin (TPPS) aggregation on its excited states absorption spectra, triplet states quenching by molecular oxygen and singlet oxygen production. Experimental techniques such as optical absorption, Z-scan with a white light continuum source and the Laser Flash Photolysis were used to fulfil the study. J-aggregates possess reverse saturable absorption in the 505-660 nm spectral range with a peak centered close to 540 nm.

Effects of bovine serum albumin (BSA) on the excited-state properties of meso-tetrakis(sulfonatophenyl) porphyrin (TPPS).

To infer changes in the photophysical properties of porphyrins due to complexation with albumin, a combination of Z-scan and conventional spectroscopic techniques was employed. We measured the characteristics of excited states of meso-tetrakis(sulfonatophenyl) porphyrin bound to bovine serum albumin and observed that the binding reduces the intersystem crossing quantum yield and increases the internal conversion one. A reverse saturable absorption process was observed in the nanosecond timescale.

Photoactivated biscarbocyanine dye with two conjugated chromophores: complexes with albumin, photochemical and phototoxic properties.

Complexes of photosensitizers with blood proteins play an essential role in their delivery to the cell, as well as in the efficacy of photodynamic therapy. Biscarbocyanine dye non-covalently binds human serum albumin (HSA), the dissociation constant of the dye with albumin being Kd = (1.7 ± 0.

Photodynamic inactivation of Bovine herpesvirus type 1 (BoHV-1) by porphyrins.

In this work, the photodynamic efficiency of anionic meso-tetrakis sulfonophenyl (TPPS4), cationic meso-tetrakis methylpyridiniumyl (TMPyP) and their zinc complexes (ZnTPPS4 and ZnTMPyP) in the inactivation of Bovine herpesvirus type 1 (BoHV-1) was evaluated. At a non-cytotoxic concentration, all porphyrins showed significant antiviral activity after irradiation using a halogen lamp. The efficiency of the cationic porphyrins was higher than that of the anionic ones.

Stimulation of Cysteine-Coated CdSe/ZnS Quantum Dot Luminescence by meso-Tetrakis (p-sulfonato-phenyl) Porphyrin.

Interaction between porphyrins and quantum dots (QD) via energy and/or charge transfer is usually accompanied by reduction of the QD luminescence intensity and lifetime. However, for CdSe/ZnS-Cys QD water solutions, kept at 276 K during 3 months (aged QD), the significant increase in the luminescence intensity at the addition of meso-tetrakis (p-sulfonato-phenyl) porphyrin (TPPS) has been observed in this study. Aggregation of QD during the storage provokes reduction in the quantum yield and lifetime of their luminescence.

Acridine orange interaction with DNA: Effect of ionic strength.

Background: The study of acridine orange (AO) spectral characteristics and the quenching of its singlet and triplet excited states by TEMPO radical at its binding to DNA in the function of the DNA concentration and in the absence and presence of NaCl is reported.

Methods: The study was performed using steady-state and time resolved optical absorption and florescence, fluorescence correlation spectroscopy and resonant light scattering techniques.

Results: The presence of different species in equilibrium: AO monomers and aggregates bound to DNA, has been demonstrated, their relative content depending on the DNA and the AO concentrations.

Quantum dot effects upon the interaction between porphyrins and phospholipids in cell membrane models.

This study employed surface pressure isotherms and spectroscopic techniques to investigate the effect of quantum dots on the interaction between porphyrins and phospholipids using Langmuir monolayers and Langmuir-Blodgett films formed from negatively charged DMPA (the sodium salt of dimyristoyl-sn-glycero-phosphatidyl acid) and zwitterionic DPPC (1,2-dipalmitoyl-sn-glycero-3-phosphocholine) as cell membrane models in the presence of 5,10,15,20-tetrakis(4-N-tetradecyl-pyridyl) porphyrin (TMPyP), 5,10,15,20-tetrakis(p-sulfonato-phenyl) porphyrin (TPPS4) and PEG-coated CdSe/ZnS quantum dots (QD). The porphyrins present at the monolayer subphase affected the organization of the lipids at the air/liquid interface, as shown by the changes in the surface pressure-surface area isotherms. QDs enhanced the interaction of TMPyP with DMPA, improving their transference from the liquid monolayers to solid supports.

Cell survival and altered gene expression following photodynamic inactivation of Paracoccidioides brasiliensis.

Paracoccidioidomycosis (PCM) is a systemic mycosis caused by Paracoccidioides brasiliensis. Currently, the treatment approach involves the use of antifungal drugs and requires years of medical therapy, which can induce nephrotoxicity and lead to resistance in yeast strains. Photodynamic inactivation (PDI) is a new therapy capable of killing microorganisms via the combination of a nontoxic dye with visible light to generate toxic reactive oxygen species (ROS).

Pulse train fluorescence technique for measuring triplet state dynamics.

We report on a method to study the dynamics of triplet formation based on the fluorescence signal produced by a pulse train. Basically, the pulse train acts as sequential pump-probe pulses that precisely map the excited-state dynamics in the long time scale. This allows characterizing those processes that affect the population evolution of the first excited singlet state, whose decay gives rise to the fluorescence.

Computational study of steric and spectroscopic characteristics of bi-chromophoric cyanine dyes: comparison with experimental data.

The spectral and energetic characteristics of four bi-chromophoric cyanine dyes (BCDs) which possess angles between chromophores 180 degrees , 150 degrees , 120 degrees and 90 degrees , were studied using quantum chemical calculations in comparison with experimental data. It was demonstrated that for BCD with 180 degrees , 150 degrees and 90 degrees trans-trans isomers possess the lowest energy, while for BCD with 120 degrees the trans-trans and cis-trans isomers have comparable energies and in the temperature range from 273K up to 373K both isomers of this dye are present. It was also demonstrated that the splitting of the spectra of cyanine dyes with two chromophores (BCD) was determined by two effects: the dipole-dipole chromophore interaction and the electron tunneling through the central heterocycle.

On the dynamics of the TPPS4 aggregation in aqueous solutions: successive formation of H and J aggregates.

The dynamics of aggregation of meso-tetrakis (p-sulfonatofenyl) porphyrin (TPPS4) in function of its concentration, pH and ionic strength was studied by optical absorption, fluorescence and resonance light scattering (RLS) techniques. In the region of pH, where TPPS4 exists in biprotonated form, the addition of NaCl induces the TPPS4 aggregation due to the formation of the "cloud" of counter ions around the TPPS4 molecule thus reducing electrostatic repulsion between the porphyrin molecules. The formation of this "cloud" shifts the pKa value to acid region (from 5.

Cytotoxicity of nitroheterocyclic compounds, quinifuryl and nitracrine, towards leukaemic and normal cells on the dark and under illumination with visible light.

The cytotoxicity of two nitroheterocyclic compounds (NHCD), Nitracrine, 1-nitro-9(3-3-dimethylaminopropylamino) acridine and Quinifuryl, 2-(5'-nitro-2'-furanyl) ethenyl-4-[N-[4-(N,N-diethylamino)-1'-methylbutyl] carbamoyl] quinoline, towards two lines of leukaemic cells and a line of non-transformed cells, was measured in comparison, on the dark and under illumination with visible light (350-450 nm). Both drugs showed highly elevated cytotoxicity when illuminated with LC(50) values 7-35 times lower after 1 h illumination compared to 1 h incubation of cells incubation with drug on the dark. Cytotoxicity of Nitracrine toward all cell lines studied exceeded that of Quinifuryl, both on the dark and under illumination, so that approximately 10 times lower concentration of former drug was needed to reach the same toxicity as the latter.

Spectroscopic studies of the interaction of bichromophoric cyanine dyes with DNA. Effect of ionic strength.

Spectroscopic characteristics of a cyanine dye with two chromophores (biscyanine dye, BCD) in aqueous solutions and effects of NaCl and DNA upon these characteristics have been studied by optical absorption, circular dichroism (CD) and fluorescence spectroscopies. In homogeneous solutions, BCD is characterized by intense optical absorption (epsilon =1.33 x 10(5) M(-1) x cm(-1)) and weak fluorescence (phi(fl)=0.