Glycoside Esters of 5-Aminolevulinic Acid for Photodynamic Therapy of Cancer

Abstract

Aliphatic and ethylene glycol esters of 5-aminolevulinic acid (ALA) are very efficient precursors of the photosensitizer protoporphyrin IX (PpIX) for photodynamic therapy; however, they diffuse passively across the cell membrane and thus lack cell selectivity. We evaluated whether alpha-glucose, alpha-mannose, or beta-galactose esters of ALA would present improved properties as precursors of PpIX. Esterification was performed either at the position O-1 or O-6 of the sugars with or without an ethylene glycol linker, and these glycoside esters of ALA were evaluated in human cells. The results demonstrated that glycoside esters of ALA are efficient precursors of PpIX in human cancer and angiogenic endothelial cells, comparable to free ALA, but not in normal human fibroblasts. PpIX production was confirmed by fluorescence microscopy and photodynamic treatment of cells. The O-1 or O-6 positions of functionalization and the nature of the sugar moiety did not influence PpIX production. The presence of the ethylene glycol linker generally resulted in decreased PpIX production. The uptake of these glycoside esters of ALA by cells was not decreased in the presence of high concentrations of the related sugars. Inhibitors of alpha-glucosidases or alpha-mannosidases did not decrease PpIX production. These results suggest the involvement of active non-glycoside-specific membrane transporter(s) for uptake and of esterases rather than glycosidases in the release of ALA from the glycoside esters of ALA.

Combined arene ruthenium porphyrins as chemotherapeutics and photosensitizers for cancer therapy

“…The culture medium was replaced with complete medium containing the ruthenium complexes for concentrations from 0 to 100 lM and the cells were exposed to the complexes for 72 h. Thereafter, cell survival was measured using the alamarBlue test as previously described [23,24]. In accordance with the manufacturer's instructions, alamarBlue solution (AbD Serotec, Oxon, UK) was added at 10% v/v and incubation was continued for 2 h. Fluorescence intensities of the cell culture supernatants were assessed using a fluorescence microplate reader (Cytofluor, PerSeptive BioSystems, Switzerland) at excitation and emission wavelengths of 530 and 580 nm, respectively.…”

Sawhorse-type diruthenium tetracarbonyl complexes containing porphyrin-derived ligands as highly selective photosensitizers for female reproductive cancer cells

“…The singlet oxygen quantum yield was determined using the singlet oxygen specific fluorescence at 1,270 nm monitored by a liquid-nitrogen-cooled germanium detector (model EO-817L, North Coast Scientific) from the DCPR facility, ENSIC, Nancy, France. Evaluation of uptake and toxicity of the complexes Cells in 48-well plates (Costar) were exposed at 37°C to increasing concentrations of complexes in complete culture medium for 48 h. After they had been washed with phosphate-buffered saline (PBS), the supernatants were replaced with fresh medium and the cell-associated content was evaluated by its porphyrin characteristic fluorescence in a thermostated fluorescence microplate reader (Cytofluor, PerSeptive BioSystems), with excitation and emission filters set at 409 ± 5 and 645 ± 10 nm, respectively, essentially as previously described [25,26]. Cell survival was measured using the 3-(4,5-dimethyl-2-thiazoyl)-2,5-diphenyltetrazolium bromide (MTT) test.…”

“…Slides were washed and incubated with the nuclear stain 4 0 ,6 0 -diamidino-2-phenylindolyl hydrochloride (DAPI; Roche Diagnostics, Mannheim, Germany, 1 lg/mL in PBS) for 10 min at 37°C, and examined in PBS under a fluorescence microscope (Axioplan2, Carl Zeiss, Feldbach, Switzerland) and filters were set at 365-nm excitation light (BP 365/12, FT 395, LP 397) for DAPI and 535-nm excitation light (BP 510-560, FT 580, LP 590) for porphyrins as previously described [19,20,25].…”

“…Cells were irradiated with a laser at 652 nm (Ceralas 652 laser diode, Biolitec, Jena, Germany) coupled to with a frontal diffuser (Medlight, Ecublens, Switzerland), at an irradiance of 30 mW/cm 2 and with light doses ranging from 2.5 to 20 J/ cm 2 as previously described [19,20,24,25]. Cell survival was assessed with the MTT assay 24 h after the end of the irradiation and compared with values for cells irradiated without the complexes as previously described [19].…”

The Use of Dipeptide Derivatives of 5-Aminolaevulinic Acid Promotes Their Entry to Tumor Cells and Improves Tumor Selectivity of Photodynamic Therapy

“…To address these issues, a variety of ALA prodrugs have been investigated, incorporating specific chemical modifications that may provide enhanced uptake and hence higher PpIX production and thus photosensitization (16). The conversion of ALA to ester prodrugs with enhanced lipophilicity has been extensively investigated, and various studies have demonstrated that esterification of ALA with both aliphatic linear and cyclic alcohols reduces the amount of ALA required for photosensitization (17)(18)(19)(20)(21). Prodrugs of this kind, in particular methyl (Me-ALA) and hexyl ester (He-ALA) derivatives of ALA, have now been validated in a clinical setting, with regulatory approval being granted for the use of Me-ALA for the treatment of actinic keratosis in Europe and the United States (22,23), and basal cell carcinoma in Europe (23).…”