Wavelength-dependent Properties of Photodynamic Therapy Using Hypericin in vitro and in an Animal Model¶

Abstract

Wavelength effects in photodynamic therapy (PDT) with hypericin (HY) were examined in a C26 colon carcinoma model both in vitro and in vivo. Irradiation of HY‐sensitized cells in vitro with either 550 or 590 nm caused the loss of cell viability in a drug‐ and light‐dose–dependent manner. The calculated ratio of HY‐based PDT (HY‐PDT) efficiencies at these two wavelengths was found to correlate with the numerical ratio of absorbed photons at each wavelength. In vivo irradiation of C26‐derived tumors, 6 h after intraperitoneal administration of HY (5 mg/kg), caused extensive vascular damage and tumor necrosis. The depth of tumor necrosis (d) was more pronounced at 590 than at 550 nm and increased when the light dose was raised from 60 to 120 J/cm2. The maximal depths of tumor necrosis (at 120 J/cm2) were 7.5 ± 1.5 mm at 550 nm and 9.9 ± 0.8 mm at 590 nm. Both values are rather high in view of the limited penetration of green‐yellow light into the tissue. Moreover, the depth ratio, d590/d550= 1.3 (P < 0.001), is smaller than expected considering the 2.2‐fold lower HY absorbance and the 1.7‐fold lower tissue penetration of radiation at 550 than at 590 nm. This finding indicates that in vivo the depth at which HY‐PDT elicits tumor necrosis is not only determined by photophysical considerations (light penetration, number of absorbed photons) but is also influenced significantly by other mechanisms such as vascular effects. Therefore, despite the relatively short‐wavelength peaks of absorption, our observations suggest that HY is an effective photodynamic agent that can be useful in the treatment of tumors with depths in the range of 1 cm.

Photodynamic therapy of malignant glioma with hypericin: Comprehensive in vitro study in human glioblastoma cell lines

“…Illumination of HYtreated glioblastoma cells (2 h/2.5 μM) at 595 nm with light doses as low as 0.15-0.20 J/cm 2 resulted in a decrease in cell survival to 50% (ID 50 -values); after exposure to 0.4 J/cm 2 cell survival was reduced to about 10% as compared to nonilluminated controls. These results are basically in line with results obtained for other cell lines (11,13,16). In the case of AY-27 cells (transitional cell carcinoma), incubated with HY (0.05-10 μM/2 h) and illuminated (595 nm) of under quite similar experimental conditions as used in the present study, an incubation concentration of about 2.5 μM was required to reduced cell survival to 50% (IC 50 -value) when cells were illuminated with 0.45 J/cm 2 (12).…”

“…In addition, it has been demonstrated in vivo (C26 colon carcinoma cells inoculated subcutaneously) that HY-PDT was more effective at 590 nm as compared to that at 550 nm. This was deduced from an increase in the depth of tumour necrosis, which was not solely due to the increased penetration depth of yellow light as compared to green light (13).…”

Hypericin-bearing magnetic iron oxide nanoparticles for selective drug delivery in photodynamic therapy

“…With this assay, the hypericin concentration of SPION CMD-Hyp was determined as 6.9±0.8 µg/mL and in relation to the iron concentration it is 6.7±0.5 µg hypericin/mg iron, which is high enough for further biological tests. 31,32 Washing of the particles 12 weeks after fabrication and remeasuring the hypericin concentration resulted in similar contents, proving that the particles do not show drug leakage over the examined time period.…”

Cellular and Molecular Mechanisms of Photodynamic Hypericin Therapy for Nasopharyngeal Carcinoma Cells

“…Which pathway is induced depends on the different properties of the photosensitizer, the type of cells, the density of population, and the experimental method. Furthermore, the method itself varies by photosensitizing agent concentration, light dose, and incubation time (Blank et al, 2002;Alvarez et al, 2003). Which pathway the cell takes to PDT-induced death is organelle-dependent as well.…”