Howe L, Zhang J Z
Department of Chemistry and Biochemistry, University of California, Santa Cruz 95064, USA.
Photochem Photobiol. 1998 Jan;67(1):90-6.
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.
四磺酸酞菁锌（ZnPcS4）是一种用于光动力疗法（PDT）的潜在光敏剂，已通过飞秒激光光谱进行了研究。发现其在水中的激发态动力学很快（<80皮秒），且以分子间聚集为主导。由于PDT的 proposed机制是从光敏剂的三重激发态到三重态O2的能量转移从而产生单线态O2，因此预计短寿命不利于产生单线态O2。这就引发了一种观点，即生物底物的存在可能会对激发态动力学产生影响。为了验证这一假设，已在存在模型膜正十六烷基三甲基溴化铵（CTAB）的情况下直接测量了ZnPcS4激发态的寿命。还测量了ZnPcS4在缓冲溶液中和与人血清白蛋白（HSA）一起时的激发态动力学。相对于在水中观察到的情况，HSA和CTAB的存在显著增加了激发态寿命。ZnPcS4在CTAB中的较长寿命（>1纳秒）表明胶束表面有利于单体形成。通过增加激发态寿命，表面大大提高了ZnPcS4的光敏潜力。
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