Photosensitization Ability of a Water Soluble Zinc(II)tetramethyltetrapyridinoporphyrazinium Salt in Aqueous Solution and Biomimetic Reverse Micelles Medium

Abstract

The spectroscopic properties and the photodynamic activity of a highly water soluble zinc(II)tetramethyltetrapyridino[2,3-b:2',3'-g:2",3"-l:2"',3'''-q]porphyrazinium salt (ZnTM2,3PyPz) were investigated in aqueous homogeneous solution and in biomimetic reverse micelles medium bearing photooxidizable biological substrates. Absorption and fluorescence spectroscopic studies indicate that ZnTM2,3PyPz is dissolved as monomer in water and in n-heptane/sodium bis(2-ethylhexyl)sulfosuccinate (AOT, 0.1 M)/water (W0 = 30) micellar system. Fluorescence quantum yields (phi F) of 0.29 and 0.27 were calculated for ZnTM2,3PyPz in water and in AOT micelles, respectively. Spectroscopic analysis at different AOT concentrations showed interaction between ZnTM2,3PyPz and AOT reverse micelles with a binding constant (Kb) of 1.7 x 10(3) M(-1). The photosensitization ability of ZnTM2,3PyPz was evaluated using 9,10-dimethylanthracene (DMA). Singlet molecular oxygen, O2(1 delta g), production yielded values of phi(delta) = 0.65 for ZnTM2,3PyPz in AOT micelles. Also, ZnTM2,3PyPz induced efficiently the decomposition of the amino acid L-tryptophan (Trp) and the nucleotide guanosine 5'-monophosphate (GMP) in both media. A value of approximately 3.6 x 10(7) s(-1) M(-1) was found for the second order rate constant of Trp (k(r)(Trp)) decomposition in the AOT system, which is near to that found in pure water. Moreover, ZnTM2,3PyPz formed stable complexes with GMP with a binding constant of K(GMP) = 1.0 x 10(3) M(-1). 1H NMR studies indicated that ZnTM2,3PyPz interacts mainly with the guanine moiety more than the sugar part of GMP. On the other hand, the photodynamic activity of ZnTM2,3PyPz produced decomposition of GMP. Quantification of GMP by HPLC indicates that the nucleotide is photooxidized with a k(obs)(GMP) = 2.6 x 10(-4) s(-1) in water. Photooxidation of GMP considerably increases in deuteriated water indicating that ZnTM2,3PyPz appears to perform its photosensitizing action via the intermediacy of O2(1delta g). Also, efficient sensitized decomposition was observed in micellar media resembling that in pure water. These results provide a better understanding of the effective photodynamic action produced by ZnTM2,3PyPz like a potential phototherapeutic agent for the treatment of neoplastic diseases by photodynamic therapy.

Synthesis and photodynamic properties of amphiphilic A3B-phthalocyanine derivatives bearing N-heterocycles as potential cationic phototherapeutic agents

“…In all cases, the shape of Q-bands was very similar to that found for ZnPc with only a small hypsochromic shift by w2 nm [16]. In contrast, the Q-bands of ZnTM2,3PyPz is blue shifted by w30 nm with respect to that of the ZnPc [18]. This indicates that the presence of one annulated 6-membered N-heterocycle, pyridine or pyrazine, has only a small perturbation effect on the electronic structure and symmetry of the main porphyrazine p-chromophore, which substantially retains its effective fourfold symmetry [26].…”

“…In this way, efficient photosensitization ability was found for a highly water soluble zinc(II) tetramethyltetrapyridino[2,3-b:2 0 ,3 0 -g:2 00 ,3 00 -l:2 000 ,3 000 -q]porphyrazinium salt (ZnTM2,3PyPz, Scheme 1), investigated in aqueous homogeneous solution and in biomimetic reverse micelle systems bearing photooxidizable biological substrates [18].…”

Porphyrin–Schiff Base Conjugates Bearing Basic Amino Groups as Antimicrobial Phototherapeutic Agents

“…The efficacy of porphyrins as photosensitizing agents can be studied using compounds of biological origin, such as amino acids and nucleotides [27,39]. These substrates are potential targets for porphyrin-mediated PDI in microbial cells.…”

Evolution of Phthalocyanine Structures as Photodynamic Agents for Bacteria Inactivation

“…A tetracationic Zn(II) porphyrazinium salt (ZnPc 40 ) was obtained, which was highly soluble in water and in a biomimetic medium of AOT reverse micelles (Figure 13). [47] There is a substantial difference in the solubility of compounds 7 and 40 in polar media due to the position of the positive charges. In ZnPc 40 , the methyl groups distort the planarity of the macrocycle, avoiding aggregation in water.…”