Cytotoxicity of octal-bromide zinc phthalocyanine after photodynamic therapy with different light sources

OBJECTIVE

The objective of this study was to investigate the cytotoxicity of octal-bromide zinc phthalocyanine (ZnPcBr8) at different concentrations (0.25, 0.5, and 1 microM) after irradiating HEp-2 cell cultures with two different light sources: a diode semiconductor laser (660 nm, 30 mW) or an LED (640 nm, 70 mW). In order to obtain comparative results, the irradiation parameters of both light sources were adjusted so that the amount of energy density delivered would be the same (4.5 J/cm2).

BACKGROUND DATA

Numerous photosensitizers and light sources used in the treatment of human disease have been studied. Based on these studies, a comparative evaluation of two light sources used in photodynamic therapy (PDT) with ZnPcBr8 was proposed.

MATERIALS AND METHODS

HEp-2 cells were incubated with ZnPcBr8 at different concentrations (0.25, 0.5, or 1 microM) for 1 h, irradiated with the diode semiconductor laser (660 nm at 30 mW for 300 sec; 4.5 J/cm2) or the LED laser (640 nm at 70 mW for 128 sec; 4.5 J/cm2), and then incubated in MEM medium for 1 or 24 h. The cells were analyzed using the MTT and trypan blue dye exclusion tests.

RESULTS

The results demonstrated that the concentration of 1 microM of ZnPcBr8 was the most effective after PDT administered by both light sources. According to the MTT results, HEp-2-cell viability decreased by 97.96% 1 h after, and by 99.87% 24 h after irradiation with the diode semiconductor laser, and decreased by 94.03% 1 h after, and by 99.21% 24 h after irradiation with the LED. The results obtained using the trypan blue dye exclusion test confirmed the photodynamic efficacy of ZnPcBr8 employed with both light sources. With regard to HEp-2-cell viability, the following results were observed: a decrease of 98.73% 1 h after, and of 99.49% 24 h after irradiation with the diode semiconductor laser; and a decrease of 98.76% 1 h after, and of 99.23% 24 h after irradiation with the LED.

CONCLUSIONS

According to our results with the irradiation parameters studied here, both the LED and diode semiconductor laser can be used for PDT in vitro, since both light sources had excellent photodynamic efficacy.

Photodynamic therapy with a new photosensitizing agent

OBJECTIVE

The aim of this study was to investigate the cytotoxicity of octal-bromide zinc phthalocyanine (ZnPcBr(8)) before and after irradiation with a low-power laser (AsGaAl) and analyze the effects of photodynamic therapy (PDT) on the nucleus of L929 cells.

BACKGROUND DATA

One of the most recent and promising applications of phthalocyanine in medicine is in the detection and cure of tumors. We studied the ZnPcBr(8) in agreement with the development of new photosensitizing agents for curing tumors.

METHODS

L929 cells were cultivated at standard conditions, incubated with ZnPcBr(8) for 1 h at different concentrations, irradiated with a semiconductor laser, and incubated in MEM medium for 1, 12, or 24 h. Cells were analyzed using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-tetrazolium bromide (MTT) technique and fluorescence microscopy.

RESULTS

The results demonstrated that ZnPcBr(8) at 1 microM was the most effective concentration for PDT, with a decrease of 63% after 1 h, 99% after 12 h, and 100% after 24 h in relation to the control group. The fluorescence microscopy results showed that ZnPcBr(8) was localized in the perinuclear region when analyzed 1 h after incubation. Nucleus staining with DAPI made it possible to observe that nuclear fragmentation occurred 24 h after PDT, cytoplasm retraction at 1, 12, and 24 h after PDT, and vacuoles along the cytoplasm at 12 and 24 h after PDT.

CONCLUSION

According to the results obtained in this study, L929 cell death caused by PDT with ZnPcBr(8) possesses characteristics of apoptosis mediated by the mitochondria, due to the decrease in cells viability, the subcellular localization, and the photodamage found.

Analysis of Mitochondrial Activity Related to Cell Death after PDT with AlPCS4

OBJECTIVE

The aim of this study was to report that photodynamic therapy (PDT) with mitochondria-associated chloroaluminum phthalocyanine tetrasulfonate (AlPcS(4)) leads to significant alterations in this organelle.

BACKGROUND DATA

PDT is a viable treatment modality for a variety of tumors, as well as for some non-oncologic diseases. The procedure submits cells or tissue to a photosensitizing drug followed by light irradiation of appropriate wavelength, usually in the red area or close to infrared, and compatible with the drug absorption spectrum, inducing the apoptotic process. However, the precise mechanism of PDT-induced apoptosis is not well characterized. Several cellular organelles can be postulated as the target for PDT with different photosensitizers such as plasmatic membrane, nucleus, mitochondria, endoplasmic reticulum, Golgi complex, and others. The mitochondrion is the main target in PDT because it is the main organelle involved in apoptosis. One of the main agents is cytochrome c, a proapoptotic factor that preferentially links itself to the mitochondrial cardiolipin.

METHODS

The photosensitizing effects of AlPcS(4) were studied in the mitochondria. Cells were irradiated with a diode laser (670 nm, energy density of 4.5 J/cm(2), and power density of 45 mW/cm(2)).

RESULTS

The fluorescent analyses of the mitochondria were performed with MitoTracker and nonyl acridine orange (NAO), and electron microscopy demonstrated that PDT with AlPcS(4) leads to significant alterations in mitochondria, causing membrane potential loss, alteration in cardiolipin distribution and cell death.

CONCLUSION

The labels with Mitotracker and NAO demonstrated mitochondrial migration to the perinuclear region, confirmed through electron microscopy, suggesting that intact mitochondria were solicited for possible DNA fragmentation.

Ultrastructural changes in Tritrichomonas foetus after treatments with AlPcS4 and photodynamic therapy

The Tritrichomonas foetus is an amitochondrial parasitic protist which causes bovine trichomoniasis, a major sexually transmitted disease in cattle. No effective drugs for this disease have been approved to this date. Photodynamic therapy (PDT) is an experimental treatment that shows great potential for treating bacteria, fungi, yeasts, and viruses. However, the cytotoxic effect of PDT on protozoan has been poorly studied. In this study, PDT with aluminum phthalocyanine tetrasulfonated (AlPcS4) photosensitizer was efficient in killing T. foetus. The mode of cell death in T. foetus after PDT was investigated by transmission electron microscopy. Morphological changes, such as membrane projections, nucleus fragmentation with peripheral masses of heterochromatin, endoplasmic reticulum proliferation, intense cytoplasmic vacuolization, fragmented axostyle-pelta complex, and internalized flagella could be observed. This is the first report to demonstrate cell death in T. foetus after PDT, and thus will open up new lines of investigation to develop new treatments for bovine trichomoniasis.