Aplicações dos sistemas de transferência de energia eletrônica baseados em nanoestruturas de peptídeos
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2019-09-20
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Universidade Federal de Goiás
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In this work, we prepared a system comprised of self-assembled nanostructures of diphenylalanine (Phe-Phe) combined with the fluorophore coumarin 6 (C6) for encapsulation of perillyl alcohol (PA), a drug administered in glioma treatment. The photophysical characteristics of this system were determined through steady-state and time resolved fluorescence spectroscopies and epifluorescence microscopy. The formation of an exciplex between the Phe-Phe and C6 was identified, characterized by a stabilization of electronic excited states in the system. This finding encouraged the investigation of different applications for this system, such as sensing, drug delivery and photodynamic therapy (PDT). In this context, different fluorescence lifetimes obtained for this system in the presence and absence of oxygen (O2(g)) demonstrated the applicability of the system as a dynamic sensor for dissolved O2. Nano and microvesicles obtained from the self-assembly of this dipeptide, in the presence of C6, were used for encapsulation and release of perillyl alcohol. The drug release was triggered by induced interconversion of the vesicles to nanotubes by modification of the chemical environment and was monitored by time-resolved fluorescence spectroscopy combined to epifluorescence microscopy. The spectroscopy techniques also revealed a role of the drug in the charge transfer exciplex of Phe-Phe combined to C6, which resulted in a further stabilization of electronic excited state. Also, the singlet oxygen quantum yield was determined through indirect measurements, seeking PDT application of the new drug delivery system. Quantum yields of 0.7 and 0.8% were obtained for the C6 fluorophore and the Phe-Phe/C6 combined system, respectively. However, the quantum yield of the complete system (nano/microvesicles of Phe-Phe/C6 bearing the PA in its interior) was 3%, which represents a significant increase as a result of the unique photophysical properties found in this system. These findings show that this system has applicability derived from the combination of the therapies with perillyl alcohol and PDT as a synergistic effect between the properties of the encapsulated drug and photodynamic activity.
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SOUZA, Geovany Albino de. Aplicações dos sistemas de transferência de energia eletrônica baseados em nanoestruturas de peptídeos. 2019. 125 f. Tese (Doutorado em Química) - Universidade Federal de Goiás, Goiânia, 2019.