Photodynamic activity of liposome‐delivered Cd‐texaphyrin using tumor‐bearing nude mice

Abstract

Photodynamic effects in bladder-tumor bearing nude mice induced by a krypton ion laser (752.5 nm) after i.v. application of liposome-delivered cadmium texaphyrin were investigated. Cd-texaphyrin possesses strong absorption transitions in the far red spectral region (around 760 nm) and a high quantum efficiency of singlet oxygen production. No therapeutic effects were obtained using irradiation 24 hours after administration of the sensitizer, whereas phototreatment 2 hours after application led to significant tumor reduction. This corresponds well with studies on fluorophore-labeled liposomes indicating highest tumor accumulation 1-2 hours after administration. However, the induced cytotoxic effects were lower than those of HpD.

Photodynamic activity of lutetium-texaphyrin in a mouse tumor system

“…It also could be the result of more efficient production of singlet oxygen by PCI-0123 [7,29], which would lead to greater cytotoxicity at the drug localization site. Our finding of greater efficacy with PCI-0123 than with Photofrin is opposite to that found by Konig et al [13] when comparing Cd-texaphyrin with hematoporphyrin derivative. The most likely explanation of this difference is that the metal species in the center of the texaphyrin moiety affects the usefulness of that particular texaphyrin compound as a photosensitizer.…”

“…This study, like those of Young et al [8], Konig et al [13], and Woodburn et al [14,16], found that early light application times, 5-6 hr after drug injection, were most effective. The diminished PDT response at 24 hr after drug administration and the observation that the urine color had returned to normal by that time indicates that most of the unbound photosensitizer had cleared from the animals by that time.…”

“…Initial work has been done in cellular [9,10], bacterial [11], and viral systems [12]. More recently, studies have begun to appear in which the photodynamic activity of texaphyrins in mammalian tumor models has been examined [8,[13][14][15][16], and limited clinical trials have been done on metastatic cancers [17]. These studies, however, have not fully examined the effects of the different treatment parameters on the efficacy of PCI-0123, and only one [13] directly compared a texaphyrin compound with another photosensitizer.…”

“…More recently, studies have begun to appear in which the photodynamic activity of texaphyrins in mammalian tumor models has been examined [8,[13][14][15][16], and limited clinical trials have been done on metastatic cancers [17]. These studies, however, have not fully examined the effects of the different treatment parameters on the efficacy of PCI-0123, and only one [13] directly compared a texaphyrin compound with another photosensitizer. The present study explores the PDT response of the SMT-F tumor model to treatment with PCI-0123 as a function of laser energy dose, drug dose, and timing of laser irradiation after drug administration.…”

A Computational Way To Achieve More Effective Candidates for Photodynamic Therapy

“…The strong SOC effect of heavy metal atoms makes the transition metal complexes possess great advantages over organic compounds in ISC between the spin-forbidden states. In fact, some diamagnetic metals, such as Lu, Hg, Cd, and Zn, are known to enhance ISC and to elongate triplet lifetime of the PS. ,− Instead, the paramagnetic ones are found to deactivate the excited state, reduce the excited-state lifetime, and prevent the occurrence of photochemical reactions . Among these diamagnetic metal complexes, the Zn-containing complexes remain widely used as PDT candidates due to their richly populated triplet excited states and efficient photodynamic production of singlet oxygen. ,, The electron configurations of Zn ion are elucidated in detail to find the reason why Zn complexes are so popularly applied in PDT.…”