Interactions of hypericin with a model mutagen – Acridine orange analyzed by light absorption and fluorescence spectroscopy

Silver Nanoparticles Improve Fluorophore Photostability: Application to a Hypericin Study

Protection against the negative effects of solar radiation involves using cosmetics with a UV filter, but visible radiation can also have negative effects. We use dietary supplements and take medications; unfortunately, many of them contain substances that degrade under the influence of visible light, which transform into chemical compounds harmful to health. Manufacturers often include information on the prohibition of exposure to sunlight on the packaging, but consumers often do not read the product leaflet. The solution to this problem may be the addition of silver particles to preparations. In the presented article, we proposed the use of silver nanoparticles to reduce the photobleaching and photoreaction of fluorophore, while increasing the fluorescence intensity. For our research, we used a compound that is particularly sensitive to radiation: hypericin.

Spectroscopy studies of interaction hypericin with an anti-cancer therapy drug doxorubicin

The presented study was designed to estimate the ability of hypericin to interact with the anticancer drug doxorubicin. The hetero-association of hypericin and doxorubicin was investigated with absorption and fluorescence spectroscopy methods in aqueous solution of DMSO in two-component mixtures: doxorubicin-hypericin and three component mixtures: DNA-doxorubicin-hypericin. The data indicate that hypericin forms complexes with doxorubicin and that the association constants are on the order of 300,000 M^-1 in a buffer with 30% DMSO content. The absorption spectra of the hypericin - doxorubicin complexes were examined as well. Owing to its ability to interact with flat aromatic compounds, hypericin may potentially be used as an interceptor molecule to detoxification of patients after chemotherapy.

The vibronic absorption spectra and electronic states of acridine orange in aqueous solution

The time-dependent density functional theory (TD-DFT) was used to obtain vibronic absorption spectra of acridine orange dye (AO) in an aqueous solution that were in good agreement with the experiment. The protonated and neutral forms of the dye have been investigated. The results of calculations using various functionals and basis sets have been analyzed. The best agreement with experiment was given by the level of theory X3LYP/6-31G(d,p). AO molecular orbitals involved in electronic transitions due light absorption in the visible region of the spectrum have been obtained. The dipole moments and atomic charges of the ground and excited states of the AO molecule have been calculated. Maps of the electrostatic potential have been drawn. An insignificant photoinduced electron transfer was found in the central ring of the chromophore of the dye molecule. According to our calculations, the vibronic coupling and the Boltzmann distribution play a significant role in the absorption spectra of the AO.

New Poly(Propylene Imine) Dendrimer Modified with Acridine and Its Cu(II) Complex: Synthesis, Characterization and Antimicrobial Activity

A second-generation poly(propylene imine) dendrimer modified with acridine and its Cu(II) complex have been synthesized for the first time. It has been found that two copper ions form complexes with the nitrogen atoms of the dendrimeric core by coordinate bonds. The new compounds have been characterized by nuclear magnetic resonance (NMR), electron paramagnetic resonance (EPR), fourier-transform infrared spectroscopy (FTIR) and fluorescence spectroscopy. The spectral characteristics of the modified dendrimer have been measured in different organic solvents, and a negative fluorescence solvatochromism has been observed. The antimicrobial activity of the dendrimers has been tested against model pathogenic microorganisms in agar and by broth dilution method. The cotton fabric treated with both dendrimers has been evaluated towards pathogenic microorganisms. The obtained modified cotton fabrics have been shown to hamper bacterial growth and to prevent biofilm formation. Dendrimer cytotoxicity has been investigated in vitro in the model HEp-2 cell line.

Photophysical properties of methylene blue in water and in aqueous solutions of dimethylsulfoxide

A detailed study of the effect of aprotic polar solvents such as dimethylsulfoxide on methylene blue (MB) was carried out through a combination of UV-vis absorption and steady-state fluorescence spectroscopy techniques at 293.15 K. In aqueous solutions MB tends to exhibit strong tendency to aggregate. The dimerization behavior of MB in water was analyzed in terms of monomer-dimer equilibrium. The addition of dimethylsulfoxide prevents dimerization of dye molecules. From absorption spectra the dimerization constants and changes of standard Gibbs energy were calculated. From the steady-state fluorescence spectra the quantum yields and Stokes shifts were determined. To explain the effect of dimethylsulfoxide properly the other polar aprotic solvents such as N, N-dimethylformamide, acetonitrile and acetone were used. It is suggested that water structural effect is the major factor in aggregation phenomenon. Moreover the quantum yield increases drastically in dimethylsulfoxide compared with water assuming that MB may be characterized as viscosity probe.

Hetero-association models of non-covalent molecular complexation

The present review discusses the current state-of-the-art in building models enabling the description of non-covalent equilibrium complexation of different types of molecules in solution, which results in the formation of supramolecular structures different in length and composition (hetero-association or supramolecular multicomponent co-polymerisation). The description is focused on standard physical and chemical quantities such as experimental observables and equilibrium parameters of interaction (equilibrium constants and concentrations). The major partial cases of the hetero-association models, such as finite and indefinite isodesmic and cooperative complexations, and Benesi-Hildebrand and Langmuir adsorption models are considered. Future challenges in the development of the hetero-association models are provided.