The Effect of Biological Substrates on the Ultrafast Excited-state Dynamics of Zinc Phthalocyanine Tetrasulfonate in Solution

Abstract

Zinc phthalocyanine tetrasulfonate (ZnPcS4), a potential photosensitizer for photodynamic therapy (PDT), has been studied using femtosecond laser spectroscopy. The excited-state dynamics in water have been found to be fast (< 80 ps) and dominated by intermolecular aggregation. Since the proposed mechanism for PDT is energy transfer from the triplet excited state of the photosensitizer to triplet O2 creating singlet O2, the short lifetime is expected to be unfavorable for producing singlet O2. This leads to the suggestion that the presence of biological substrates may have an effect on the excited-state dynamics. To test this hypothesis, the lifetimes of the excited states of ZnPcS4 have been directly measured in the presence of a model membrane, n-hexadecyltrimethylammonium bromide (CTAB). The excited-state dynamics of ZnPcS4 in buffer solutions and with human serum albumin (HSA) have also been measured. The presence of HSA and CTAB increases the excited-state lifetime significantly relative to that observed in water. The longer lifetime of ZnPcS4 in CTAB (> 1 ns) indicates that the micellar surface favors monomer formation. By increasing the excited-state lifetime, the surface substantially increases the photosensitizing potential of ZnPcS4.

Basic principles of photodynamic therapy

“…It has been shown that aggregation changes the photophysical properties of porphyrin, chlorin, and phthalocyanine photosensitizers [85][86][87][88][89][90][91][92][93][94][95][96]. Aggregation shortens the triplet-state lifetime and decreases the singlet-oxygen quantum yield by dissipating the energy through internal conversion [92][93][94][95][96][97]. Therefore highly aggregated photosensitizers in vivo are generally considered to be less effective photosensitizers [87,98].…”

Effects of continuous wave and fractionated diode laser on human fibroblast cancer and dermal normal cells by zinc phthalocyanine in photodynamic therapy: A comparative study

“…Photodynamic therapy is a promising treatment of cancer and nonmalignant diseases such as skin [3], lung, head and neck [4], liver [5], bladder [6], esophageal [7] and breast cancer [8], brain tumors [9] and sterilization of blood to eliminate viruses such as HIV and hepatitis for transfusion [6]. This medical treatment modality is based on the localization of a chemical photosensitizer in the target cells followed by light irradiation at certain wavelength that corresponds to the peak absorption of the photosensitizer into the target tissue.…”

Determinação eletroquímica de fenóis após processo de degradação de benzeno usando sensor à base de nanotubos de carbono-ftalocianina de cobalto

“…[53] . citocromo e várias enzimas do tipo oxidases [54] . Assim, as ftalocianinas podem ser reconhecidas como moléculas biomiméticas, onde podem substituir convenientemente proteínas naturais, atuando como o centro ativo de moléculas enzimáticas, com a mesma seletividade e sensibilidade [55] .…”