Ion-induced stacking of photosensitizer molecules can remarkably affect the luminescence detection of singlet oxygen inCandida albicanscells

Abstract

Singlet oxygen (¹O₂) is an important reactive intermediate in photodynamic reactions, particularly in antimicrobial PDT (aPDT). The detection of ¹O₂ luminescence is frequently used to elucidate the role of ¹O₂ in various environments, particularly in microorganisms and human cells. When incubating the fungus, Candida albicans, with porphyrins XF73 (5,15-bis-[4-(3-Trimethylammonio-propyloxy)-phenyl]-porphyrin) or TMPyP (5,10,15,20-Tetrakis(1-methyl-4-pyridinio)-porphyrin tetra(p-toluenesulfonate)), the ¹O₂ luminescence signals were excellent for TMPyP. In case of XF73, the signals showed strange rise and decay times. Thus, ¹O₂ generation of XF73 was investigated and compared with TMPyP. Absorption spectroscopy of XF73 showed a change in absorption cross section when there was a change in the concentration from 1×10⁻⁶M to 1×10⁻³ M indicating an aggregation process. The addition of phosphate buffered saline (PBS) substantially changed ¹O₂ luminescence in XF73 solution. Detailed experiments provided evidence that the PBS constituents NaCl and KCl caused the change of ¹O₂ luminescence. The results also indicate that Cl- ions may cause aggregation of XF73 molecules, which in turn enhances self-quenching of ¹O₂ via photosensitizer molecules. These results show that some ions, e.g., those present in cells in vitro or added by PBS, can considerably affect the detection and the interpretation of time-resolved luminescence signals of ¹O₂, particularly in in vitro and in vivo. These effects should be considered for any other photosensitizer used in photodynamic processes.

Singlet oxygen generation in porphyrin-doped polymeric surface coating enables antimicrobial effects on Staphylococcus aureus

“…Light absorption measurements of TPP-OH immobilized on PU should elucidate a possible porphyrin aggregation after polymerisation, which is known to reduce the ability to generate 1 O 2 . 26 The photostability of the porphyrin in the surface was tested under the same conditions as those applied for the phototoxicity experiments. A possible leaking effect of the immobilized PS out of the coating was tested because such PS molecules could reach the bacteria on the surface leading to cell killing.…”

Cerenkov radiation: a multi-functional approach for biological sciences

“…CLI thus can be improved through excitation fluorophores to produce NIR light, which is more suitable for in vivo OI, or it could be combined with PDT to increase the efficacy of treatments. As reported by several studies, some photosensitizers for PDT need to be excited by UV or blue light, which almost match the CL spectrum [84,85]. Therefore, CL could be used to excite such molecules for PDT, especially when combined with therapeutic radionuclides.…”

TMPyP binding evokes a complex, tunable nanomechanical response in DNA

“…Finally, it is worth pointing out that the employed TMPyP concentrations fall below or well within those used in in vitro photodynamic therapy (52,55,89). Therefore, the structural and nanomechanical changes documented here are highly relevant during the therapeutic applications of TMPyP.…”