Browsing by Subject "Singlet Oxygen"

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Open Access
A bifunctional photosensitizer for enhanced fractional photodynamic therapy: singlet oxygen generation in the presence and absence of light
(Wiley-VCH Verlag, 2016) Turan, I. S.; Yildiz, D.; Turksoy, A.; Gunaydin, G.; Akkaya, E. U.
The photosensitized generation of singlet oxygen within tumor tissues during photodynamic therapy (PDT) is self-limiting, as the already low oxygen concentrations within tumors is further diminished during the process. In certain applications, to minimize photoinduced hypoxia the light is introduced intermittently (fractional PDT) to allow time for the replenishment of cellular oxygen. This condition extends the time required for effective therapy. Herein, we demonstrated that a photosensitizer with an additional 2-pyridone module for trapping singlet oxygen would be useful in fractional PDT. Thus, in the light cycle, the endoperoxide of 2-pyridone is generated along with singlet oxygen. In the dark cycle, the endoperoxide undergoes thermal cycloreversion to produce singlet oxygen, regenerating the 2-pyridone module. As a result, the photodynamic process can continue in the dark as well as in the light cycles. Cell-culture studies validated this working principle in vitro.
Open Access
Chemical modulation of singlet oxygen generation rates in thermal endoperoxide decomposition & novel fluorescent sensors for hyperphosporylated tau proteins
(2016-05) Kaya, Cansu
Chemical control over singlet oxygen generation is an open to improvement because of the importance of this reactive species in biological systems. In the first project, we aimed to synthesize a silylated 1,4-dimethylnaphthalene endoperoxide derivative which is expected to release singlet oxygen on thermolysis at a relatively slow rate at room temperature. Upon the deprotection of the silyl units with fluorine ions, it is expected it to release singlet oxygen at a much higher rate, giving rise to a control over the release of the product. The absorption and the fluorescence measurement with a trap molecule which consumes the generated singlet oxygen reveals promising results for the future work for the control of singlet oxygen generation rates. In the second part of this thesis, we focused on the synthesis of a novel fluorescent sensor of a BODIPY derivative which is capable of sensing Zinc cations. The zinc complex is also expected to have a further usage for the sensing of hyperphosphorylated tau proteins, which are commonly produced in the brains of people with Alzheimer’s disease. With this, it has a potential usage in the field of early detection of Alzheimer’s disease.
Open Access
Towards mechanochemical generation of singlet oxygen
(2018-12) Aydonat, Simay
Singlet oxygen is a short-lived reactive species which is involved a number of biochemical processes and implicated as the primary photo-generated cytotoxic agent in photodynamic therapy (PDT) of cancer. Precise chemical control of singlet oxygen generation and or storage is therefore of immense interest. In this particular study, the possibility of mechanochemical release of singlet oxygen in cross-linked polymers carrying anthracene 9,10-endoperoxides was explored. 9,10-Diphenylanthracenes are stable at room temperature but undergo thermal cycloreversion when heated to produce singlet oxygen. Thus, a cross-linked polyacrylate was synthesized, incorporating anthracene-endoperoxide modules with chain extensions at the 9,10-positions. Previously in our lab, thermal lability of the anthracene endoperoxides were shown when attached to gold nanorods. In this work, it was demonstrated that on mechanical agitation in a cryogenic ball mill, fluorescence emission due to anthracene units in the polymer is enhanced, with a concomitant generation of singlet oxygen as proved by detection with a selective probe, SOSG. Also, a cross-linked polyacrylate and a PDMS elastomer incorporating anthracene-endoperoxide modules with chain extensions at the 9,10-positions were synthesized as the polymeric matrix for a better manifestation of mechanochemical process.