Photodynamic modification of disulfonated aluminium phthalocyanine fluorescence in a macrophage cell line

Abstract

Disulfonated aluminium phthalocyanine (AlS(2)Pc) is used experimentally as a photosensitiser for both photodynamic therapy (PDT) and photochemical internalisation (PCI). In this study we have focused on modifications in intracellular photosensitiser localisation and fluorescence intensity in macrophages during and after photoirradiation. Since macrophages are highly abundant in tumour tissue and readily accumulate AlS(2)Pc both in vivo and in vitro, we investigated PDT-induced changes of AlS(2)Pc fluorescence in the murine macrophage cell line J774A.1 using CCD fluorescence imaging microscopy. The distinct intracellular localization disappeared upon red laser irradiation and was replaced by a uniform distribution accompanied by a transient fluorescence intensity increase using higher AlS(2)Pc concentrations, followed by photobleaching after further irradiation. A short period of irradiation was sufficient to induce the intracellular redistribution and intensity increase, which then continued in the dark without further laser irradiation. However in the absence of oxygen no fluorescence intensity increase or redistribution was observed. This finding favours the general assumption of photodynamic destruction of organelle membranes resulting in the observed redistribution of the phthalocyanine. No other long-lived fluorescent photoproducts were observed during irradiation. Under deoxygenated conditions slower photobleaching was observed, and photobleaching quantum yields were estimated under aerated and deoxygenated conditions. The participation of reactive oxygen intermediates (ROS) generated during irradiation was indicated by intracellular oxidation of 2',7'-dichlorodihydrofluorescein to the fluorescent 2',7'-dichlorofluorescein in macrophages. The oxygen dependence of these photomodification processes is relevant to the application of AlS(2)Pc to photochemical internalisation which relies on photosensitiser redistribution in cells upon light exposure.

Relationship between structure and photoactivity of porphyrins derived from protoporphyrin IX

“…Because these molecules already have the amphiphilic arrangements that permit better membrane incorporation, it is likely that liposomes compete with cells for these sens compounds, leading to lower cellular incorporation and photo-induced cell death. Among the compounds obtained by functionalization at positions 13 3 and 17 3 (6, 7, 8, 9 and 10), 8 presents similar behavior to that of Hp IX (10), whereas the amines and quaternary ammonium derivatives are around four times more photocytotoxic than Hp IX. The higher photocytotoxic activity of these compounds was attributed to their amphiphilic structure, with favorable logP o/w , and to the positive charges that may favor their interactions with mitochondria.…”

“…Three different routes were used to obtain seven new photosensitizers derived from Hp IX: modification at positions 3 1 and 8 1 , 13 3 and 17 3 , or of all four positions simultaneously. Analysis of the photophysical, biophysical and photocytotoxic properties showed that it is possible to correlate structural changes with compound behavior in vitro and in vivo.…”

“…The Pp IX derivatives 2 and 3 were prepared according to Kunz et al [3]. Briefly: 100 mg (0.169 mmol) of Pp IX was stirred for 6 h in 10 mL 40% HBr-acetic acid at room temperature.…”

Monitoring ALA‐induced PpIX Photodynamic Therapy in the Rat Esophagus Using Fluorescence and Reflectance Spectroscopy

“…The acquisition and interpretation of PpIX photobleaching measurements in vivo is a complex task and studies in the literature addressing these issues are somewhat conflicting (6)(7)(8)10,11,(20)(21)(22). The intrinsic mechanism of photobleaching has been shown to be photosensitizer specific (23)(24)(25)(26)(27). This has important consequences for the general interpretation of photobleaching as a dose metric for PDT (28).…”

Enhancing the efficacy of cytotoxic agents for cancer therapy using photochemical internalisation

“…Excitation of the PS results in the production of reactive oxygen species (ROS), particularly singlet oxygen which can oxidise important subcellular substrates including membrane components such as unsaturated lipids and cholesterol. Like PDT, PCI also relies on the presence of molecular oxygen for generation of ROS, although since oxygen solubility in organelle membranes is relatively high only strongly hypoxic cells should be unaffected by PCI . However these two treatments differ in key aspects (Fig.…”