Effect of amphiphilic polymers and sodium alginate on the activity of methylene blue in photogeneration of singlet oxygen ¹О₂

Abstract

The influence of amphiphilic polymers (APs): poly-N-vinylpyrrolidone, polyethylene glycol and pluronics F127, F108, as well as sodium alginate (SA) on the activity of methylene blue (MB) in the photogeneration of singlet oxygen 1О2, specifically, in a model photooxidation reaction of tryptophan in water was studied. It was shown that in the presence of all the above-mentioned AP, an increase in the effective rate constant (k eff) of tryptophan photooxidation is observed. It was suggested that the observed effect is associated with the interaction of MB with APs, which leads to disaggregation of dye associates. Such disaggregation leads to an increase in the optical density and intensity of MB luminescence. It was also shown that the photocatalytic activity of MB decreases by a factor of 1.5–3.5 in the presence of SA, which is due to the ionic interaction of the cationic MB with polyanionic SA. The interaction of MB with polysaccharide is confirmed by changes in the absorption and fluorescence spectra of the dye. The introduction of APs into a solution containing MB and SA prevents the interaction between MB and polysaccharide, which leads to an increase in the k eff values of tryptophan photooxidation in the presence of MB-AP-SA system, as well as to an increase in the optical density and fluorescence intensity of MB when AP and SA are added. The existence of weak interactions between the hydrophobic groups of MB molecules and the AP (polyvinylpyrrolidone) is also evidenced by the data obtained through 1H-NMR spectroscopy and the degree of MB fluorescence anisotropy. The AFM method shows the change in the surface structure of a thin film obtained by evaporating an aqueous solution of MB-F108-SA compared to the corresponding structure of a film obtained by evaporating an aqueous solution of MB-SA. MB-AP and MB-AP-SA systems may be promising for practical application in the aPDT treatment of chronic microbial superficial infections.

Effect of diphenylalanine on the functional activity of porphyrin and non-porphyrin photosensitizers solubilized by Pluronic F127

“…Furthermore, it was previously shown for MB that this non-porphyrin PS is localized near Pluronic micelles, i.e. near the polyethylene oxide part [32]. In this case, since the PS are localized together with the substrate in the hydrophilic edge of the micelles (or near the edge), the generated singlet oxygen can be quenched by the dipeptide, which is obviously in the aqueous phase.…”