Photostability of biological systems-Femtosecond dynamics of zinc tetrasulfonated phthalocyanine at cancerous and noncancerous human Breast tissues

Zinc tetrasulfonated phthalocyanine (ZnPcS4), was studied in aqueous solutions, films and at the biological interfaces of noncancerous and cancerous human breast tissues by using steady-state and time-resolved spectroscopy methods, including IR, Raman, UV-vis, fluorescence and transient absorption femtosecond pump-probe spectroscopy. The pump-probe transient absorption spectra were recorded on time scales from femtoseconds to nanoseconds providing insight into the molecular mechanisms of energy dissipation and primary events occurring in solution, film, and at the interface of the biological tissues. The nature of the rapid processes and competing relaxation pathways resulting from the initially excited electronic states of ZnPcS4 in aqueous solutions, films and at the biological interfaces of cancerous and noncancerous human breast tissues was studied. The results provide evidence that the sulfonated zinc phthalocyanine dissipates energy through different pathways in the environment of the noncancerous tissue and of the cancerous tissue. A detailed understanding of the paths of energy dissipation will reveal the mechanisms underlying light-induced signal transduction and the role of photoreceptors in photostability of living cells. Here, we showed that both the dynamics of the ground state So recovery and the dynamics of the first excited state Si decay at the interfacial regions of the noncancerous tissue is markedly faster than that in the cancerous tissue, suggesting that the molecular mechanisms responsible for harvesting the light energy in photosensitizers can be used for practical applications in cancer diagnostics. The paper bridges the fundamentals of cancer research with the femtosecond technologies of high temporal resolution for studying dynamics of photosensitizers in noncancerous and cancerous human breast tissues. (C) 2016 Elsevier B.V. All rights reserved.