Effects of Spherical and Rod-like Gold Nanoparticles on the Reactivity of Human Peripheral Blood Leukocytes.

Gold nanoparticles (GNPs) are widely used in the technological and biomedical industries, which is a major driver of research on these nanoparticles. The main goal of this study was to determine the influence of GNPs (at 20, 100, and 200 µg/mL concentrations) on the reactivity of human peripheral blood leukocytes. Flow cytometry was used to evaluate the respiratory burst activity and pyroptosis in monocytes and granulocytes following incubation with GNPs for 30 and 60 min. Furthermore, the concentration of interleukin-1ß (IL-1ß) in human blood samples was assessed using enzyme-linked immunosorbent assay (ELISA) after their incubation with GNPs for 24 h. Under the conditions tested in the study, the GNPs did not significantly affect the production of reactive oxygen species in the granulocytes and monocytes that were not stimulated using phorbol 12-myristate 13-acetate (PMA) in comparison to the samples exposed to PMA (p < 0.05). Compared to the control sample, the greatest significant increase in the mean fluorescence intensity of the granulocytes occurred in the samples incubated with CGNPs = 100 and 200 µg/mL for tinc = 30 and 60 min (p < 0.05). From our results, we conclude that the physicochemical properties of the nanoparticles, chemical composition, and the type of nanoparticles used in the unit, along with the unit and incubation time, influence the induced toxicity.

The origin of the dark S1 state in carotenoids: a comprehensive model.

In carotenoids, by analogy to polyenes, the symmetry of the π-electron system is often invoked to explain their peculiar electronic features, in particular the inactivity of the S0 → S1 transition in one-photon excitation. In this review, we verify whether the molecular symmetry of carotenoids and symmetry of their π-electron system are supported in experimental and computational studies. We focus on spectroscopic techniques which are sensitive to the electron density distribution, including the X-ray crystallography, electronic absorption, two-photon techniques, circular dichroism, nuclear magnetic resonance, Stark and vibrational spectroscopies, and on this basis we seek for the origin of inactivity of the S1 state. We come across no experimental and computational evidence for the symmetry effects and the existence of symmetry restrictions on the electronic states of carotenoids. They do not possess an inversion centre and the C2h symmetry approximation of carotenoid structure is by no means justified. In effect, the application of symmetry rules (and notification) to the electronic states of carotenoids in this symmetry group may lead to a wrong interpretation of experimental data. This conclusion together with the results summarized in the review allows us to advance a consistent model that explains the inactivity of the S0 → S1 transition. Within this model, S1 is never accessible from S0 due to the negative synergy of (i) the contributions of double excitations of very low probability, which elevate S1 energy, and (ii) a non-verticality of the S0 → S1 transition, due to the breaking of Born-Oppenheimer approximation. Certainly, our simple model requires a further experimental and theoretical verification.

Quality evaluation of monoenergetic images generated by dual-energy computed tomography for radiotherapy: A phantom study.

PURPOSE: Quantification analysis for monoenergetic computed tomography (CT) images obtained from dual-energy CT scanning was performed in the light of their potential use for structures delineation during radiotherapy. METHODS: Parameters that describe the quality of the images are: linearity, low and high contrast resolution, uniformity, noise and signal to noise ratio (SNR). To evaluate these parameters, a Catphan phantom was scanned using a dual-energy mode at Somatom Definition AS. Based on the polyenergetic CT images, sixteen monoenergetic series (ranged from 40 keV to 190 keV) were created by CT scanner software and automatically analyzed using Artiscan software. RESULTS: Analysis of linearity shows that a potential use of any monoenergetic images in radiotherapy planning requires that individual calibration curves are implemented for each of them. While the results of the high contrast resolution analysis were comparable for each energy (5 lp/cm), the results of the analyses for uniformity, low contrast resolution, noise and SNR allowed us to select the best imaging energies. The highest relative uniformity was detected for images reconstructed for energies of 60 keV and 70 keV (98.54% and 98.61%). Similar results were observed for low contrast resolution, where the largest number of disks was detected for these energies, and the noise values (0.42% for 60 keV, 0.44% for 70 keV). The best SNR was observed for images reconstructed for energy of 60 keV. CONCLUSIONS: Taking into account these results, the energy of 70 keV was selected as potentially the best for reconstruction of monoenergetic images used for structures delineation during radiotherapy.

Intrinsic Photoprotective Mechanisms in Chlorophylls.

Photosynthetic energy conversion competes with the formation of chlorophyll triplet states and the generation of reactive oxygen species. These may, especially under high light stress, damage the photosynthetic apparatus. Many sophisticated photoprotective mechanisms have evolved to secure a harmless flow of excitation energy through the photosynthetic complexes. Time-resolved laser-induced optoacoustic spectroscopy was used to compare the properties of the T1 states of pheophytin a and its metallocomplexes. The lowest quantum yield of the T1 state is always observed in the Mg complex, which also shows the least efficient energy transfer to O2 . Axial coordination to the central Mg further lowers the yield of both T1 and singlet oxygen. These results reveal the existence of intrinsic photoprotective mechanisms in chlorophylls, embedded in their molecular design, which substantially suppress the formation of triplet states and the efficiency of energy transfer to O2 , each by 20-25 %. Such intrinsic photoprotective effects must have created a large evolutionary advantage for the Mg complexes during their evolution as the principal photoactive cofactors of photosynthetic proteins.

Multiwavelength excitation of photosensitizers interacting with gold nanoparticles and its impact on optical properties of their hybrid mixtures.

In a hybrid mixture of organic (dye) and inorganic (metallic nanoparticles) components, the optical properties of a dye can be easily controlled by tailoring the shape or the concentration of the noble metal nanoparticles (NPs). The influences of multiexcitation (multiwavelength excitation) of photosensitizers (pheophorbide a and hematoporphyrin) on the interactions with pegylated Au-NPs and on the photophysical parameters of the dyes are studied. Detailed, systematic fluorescence quenching studies were performed in the mixtures of different contents of Au-NPs, and interpreted together with the results of quantum singlet oxygen yield examinations. According to the results, the fluorescence of the two dyes studied was effectively quenched in the presence of Au-NPs, mainly because of the resonance energy transfer between the donor (dye) and the acceptor (Au-NPs). Stern-Volmer quenching constants were determined by a few orders of magnitude higher than those describing the photochemical quenching process. In hybrid mixtures analyzed, the mechanism of energy transfer between the donor and the acceptor was nanometal surface energy transfer. Furthermore, different behavior of the mixtures on excitation with the wavelengths from the Soret and Q bands of the dyes and with those corresponding to the surface plasmon resonance band of Au-NPs was analyzed. Moreover, for certain concentrations of Au-NPs and for certain excitation wavelengths, an increase in singlet oxygen generation was observed. The results obtained indicate the significance of further studies of photosensitizers in hybrid mixtures with NPs.

Adsorption properties of biologically active derivatives of quaternary ammonium surfactants and their mixtures at aqueous/air interface. I. Equilibrium surface tension, surfactant aggregation and wettability.

The adsorption properties of surfactant mixtures containing two types of quaternary derivatives of lysosomotropic substances: alkyl N,N-dimethylalaninates methobromides and alkyl N,N-dimethylglycinates methobromides were studied. Quantitative and qualitative description of the adsorption process was carried out on the basis of experimentally obtained equilibrium surface tension isotherms. The results indicated that most of the systems studied revealed synergistic effect both in adsorption and wetting properties. In vitro studies on human cancer cells were undertaken and the data obtained showed that the mixtures suppressed the cancer cells' proliferation more effectively than individual components. Results of preliminary research on the interaction of catanionic mixtures with phospholipids suggested a possibility of a strong penetration of cell membranes by the mixtures investigated.

Molecular symmetry determines the mechanism of a very efficient ultrafast excitation-to-heat conversion in Ni-substituted chlorophylls.

In the Ni-substituted chlorophylls, an ultrafast (<60 fs) deactivation channel is created, which is not present in Ni-porphyrins. This observation prompted us to investigate in detail the mechanism of excitation-to-heat conversion in Ni-substituted chlorophylls, experimentally, using time-resolved laser-induced optoacoustic spectroscopy, and theoretically, using group theory approach. The Ni-substituted chlorophylls show exceptional photostability and the optoacoustic measurements confirm the prompt and very efficient (100%) excitation-into-heat conversion in these complexes. Considering their excellent spectral properties and the loss-free excitation-into-heat conversion they are likely to become a new class of versatile photocalorimetric references. The curious features of the Ni-substituted chlorophylls originate from the symmetry of a ligand field created in the central cavity. The central N-Ni(2+) bonds, formed via the donation of two electrons from each of the sp(2) orbitals of two central nitrogens to an empty [Formula: see text] hybrid centered on Ni(2+), have a considerable covalent character. The extreme rate of excited state relaxation is then not due to a ladder of the metal centered d-states, often invoked in metalloporphyrins, but seems to result from a peculiar topology of the potential energy surface (a saddle-shaped crossing) due to the covalent character of the N-Ni(2+) bonds. This is confirmed by a strong 0→0 character of electronic transitions in these complexes indicating a similarity of their equilibrium geometries in the ground (S(0)) and the excited states (both Q(X) and Q(Y)). The excitation energy is very efficiently converted into molecular vibrations and dissipated as heat, involving the central Ni(2+). These Ni-substituted pigments pose a fine exemplification of symmetry control over properties of excited states of transition metal complexes.

Orientation and spectral properties of two stilbazolium merocyanine dyes in stretched and unstretched polyvinyl alcohol films.

Spectral properties (anisotropy coefficients calculated for absorption, emission and fluorescence decay time) of two stilbazolium merocyanine dyes have been determined to evaluate the applicability of these dyes as sensitizers in photodynamic therapy. The dyes were embedded in an anisotropic polymer matrix. Analysis of the emission decay components measured in polarized light provides information on the interactions of the dye molecules with the polymer matrix being a model of an anisotropic biological system. Different values of the emission anisotropies obtained from various polarized components of fluorescence decays have shown that the orientations of the dye molecules influence their interactions with the polymer. This means that differently oriented dye molecules located in biological systems should exhibit different interactions with membranes. The chain length and type of side groups attached as well as the salt form of the dye molecule were shown to influence the dye-polymer interactions and should be taken into account before the application of merocyanine dyes in medicine. These dyes seem to be promising optical sensors with spectral properties, including the calculated anisotropy coefficients, sensitive to the molecular environment, useful to study orientation and interaction with neighbouring molecules in biological membranes.

Photostability and the yield of triplet state generation of bacteriochlorophyll c and bacteriopheophytin c in solution.

The paper deals with some fast and slow processes of excitation energy deactivation in bacteriochlorophyll c and bacteriopheophytin c. The experiments were carried out in the air, and in oxygen or nitrogen atmosphere at different temperatures. The parameters such as fluorescence yield, the yield of triplet state generation and photostability were estimated. On the basis of these parameters an attempt was made to preliminary select the pigments best suited for medical applications. It seems that the photosensitive and highly fluorescent bacteriochlorophyll c could be used as a fluorescence probe for diagnosis, whereas its derivative without the magnesium ion is better suited for the photochemical reactions occurring during therapeutic treatment.

Preliminary studies of phthalocyanine sensitizers incorporated into human leukemia cells from two cell-lines.

Three phthalocyanine dyes-sensitizers were incorporated into two types of human T leukemia cells from two cell-lines: CCRF and MOLT 4. The efficiency of the dye incorporation into cells and photochemical properties of stained cells were investigated using fluorescence spectroscopy. The dyes exhibited different properties in each of the two cell-lines. Small differences in cell membrane properties have a strong influence on the efficiency of dye incorporation and on the course of photodynamic reaction. It is suggested that, for a given patient, an optimal dye-sensitizer should be established before photodynamic treatment.

Dipole strengths of the Qy(0,0) bacteriochlorophyll c transition.

The absorption spectra of bacteriochlorophyll (BChl) c solutions in two mixtures of two solvents (acetonitrile with pyridine and dimethylsulfoxide with methanol) exhibiting different refractive indices were measured and deconvoluted into Gaussian components. The refractive index of mixed solvents was changed by the change in the ratio of the volumes of the liquids used in the mixture. Using the Qy(0,0) band half widths and absorption coefficient, based on the simplified formula proposed by Knox, the dipole strengths of the Qy(0,0) BChl c transition for various values of solvent refractive index were calculated and compared with values given by Knox and Spring. For both investigated combinations of two liquids, the dependence of Qy(0,0) transition dipole strength of the BChl c on solvent refractive index was almost linear. The slopes of the lines obtained from the experimental absorption bands were different for two investigated solvent mixtures. More accurate linear dependence and similar slopes of lines for both solvent mixtures were obtained using half widths and absorption coefficients of the Gaussian components of Qy(0,0) transition. It is explained by the superposition of the contributions from other electronic and vibronic transitions of BChl c monomers or possibly also from transitions of the pigments involved in some complexes with solvent molecules in the absorption region investigated. The results show that the formula proposed by Knox can be successfully applied also for BChl c, after elimination of the overlapped contributions from the other transitions, by applying Gaussian analysis to select only contribution from Qy(0,0) pigment transition.