Evaluation of photodynamic activity of octaethylporphyrin and vanadyl octaethylporphyrin

Objective: in this work we have investigated the photodynamic efficiency of octaethylporphyrin (OEP) and vanadyl octaethylporphyrin(VOOEP). Methods: this study was performed by the evaluation of photophysical parameters of these porphyrins, the photooxidationrate constants (kf) of the biomolecules (tryptophan -Trp and bovine serum albumin - BSA) and the erythrocytes photodestructionpercentage. Results: photophysical parameters value such as singlet oxygen quantum yield (Õ∆) and triplet state lifetime (ôT)indicated that OEP (Õ∆= 0.64 ±0.02, tT= 0.91 ± 0.02 ms) is more efficient than VOOEP (Õ∆= 0.26 ±0.02, tT= 0.22 ± 0.03ms). The values of kf/10-4 s-1for Trp and BSA photoxidation demonstrated that OEP (Trp= 2.80 ± 0.05 and BSA= 2.50 ± 0.1)is more efficient than VOOEP (Trp= 0.81 ± 0.08 and BSA= 0.62 ± 0.04). The photodestruction percentage of erythrocytesrevealed that the photodynamic activity of OEP is more pronounced than photoactivity of VOOEP. These results indicated thatdifferences observed in the photodynamic activity between the porphyrins could be associated with differences in their molecularstructures. Conclusion: photophysical parameters, photooxidation of biomolecules, and photodestruction of erythrocytes clearlyindicate that the vanadyl group (V=O) interferes in the photoactivity of OEP, causing a considerable reduction in its efficiency.

Photophysical properties of crowned porphyrins.

In this study, we evaluated the photophysical properties of 5,10,15,20-tetrakis[4-(1,4,7,10,13-pentaoxacyclopentadecane-2-aminomethyl)2,3,5,6-(tetrafluoro)-phenyl]-porphyrin (H2C4P) and Zn(II)5,10,15,20-tetrakis[4-(1,4,7,10,13-pentaoxacyclopenta-decane-2-aminomethyl)2,3,5,6-(tetrafluoro)-phenyl]-porphyrinate (ZnC4P). We observed that these porphyrins have unique properties when compared with classical porphyrins. The porphyrins H2C4P and ZnC4P showed efficient transfer energy S1 to T1 by intersystem crossing with high and reasonable yields of triplet excited state and singlet oxygen production. These amphiphilic structures of these porphyrins could improve its localization in the tumor cells due to the presence of the crown ether in its framework. We also believed that the crown ether could modulate the change in ion homeostase (Ca(+2), K+, Na+) as already described by some new phthalocyanine dye. This fact makes us believe that it could be reasonably used as a photosensitizer for PDT purposes.