Browsing by Subject "Photochemical reactions"

Now showing 1 - 6 of 6

Open Access
Activatable photosensitizers: agents for selective photodynamic therapy
(Wiley-VCH Verlag, 2017) Li, X.; Kolemen, S.; Yoon, J.; Akkaya, E. U.
Recent developments in the design of bifunctional and activatable photosensitizers rejuvenate the aging field of photodynamic sensitization and photodynamic therapy. While systematic studies have uncovered new dyes that can serve as potential photosensitizers, the most promising results have come from studies aimed at gaining precise control over the location and rate of cytotoxic singlet oxygen generation. As a consequence, higher selectivities and efficiencies in photodynamic treatment protocols are now within reach. This feature article highlights the variety of approaches that have been pursued to improve photodynamic therapy and to transform simple photosensitizers into smarter theranostic agents.
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
Near-IR absorbing BODIPY derivatives as glutathione-activated photosensitizers for selective photodynamic action
(Wiley-VCH Verlag, 2014) Turan, I. S.; Cakmak, F. P.; Yildirim, D. C.; Cetin Atalay, R.; Akkaya, E. U.
Enhanced spatiotemporal selectivity in photonic sensitization of dissolved molecular oxygen is an important target for improving the potential and the practical applications of photodynamic therapy. Considering the high intracellular glutathione concentrations within cancer cells, a series of BODIPY-based sensitizers that can generate cytotoxic singlet oxygen only after glutathione-mediated cleavage of the electron-sink module were designed and synthesized. Cell culture studies not only validate our design, but also suggest an additional role for the relatively hydrophobic quencher module in the internalization of the photosensitizer.
Open Access
Near-IR-triggered, remote-controlled release of metal ions: A novel strategy for caged ions
(Wiley-VCH Verlag, 2014) Atilgan, A.; Eçik, E. T.; Guliyev, R.; Uyar, T. B.; Erbas-Cakmak, S.; Akkaya, E. U.
A ligand incorporating a dithioethenyl moiety is cleaved into fragments which have a lower metal-ion affinity upon irradiation with low-energy red/near-IR light. The cleavage is a result of singlet oxygen generation which occurs on excitation of the photosensitizer modules. The method has many tunable factors that could make it a satisfactory caging strategy for metal ions.
Open Access
Template-directed photochemical homodimerization and heterodimerization reactions of cinnamic acids
(American Chemical Society, 2021-09-01) Yağcı, Bilge Banu; Zorlu, Y.; Türkmen, Yunus Emre
We developed a general method for the selective photochemical homo- and heterodimerization of cinnamic acid derivatives with the use of commercially available 1,8-dihydroxynaphthalene as a covalent template. A variety of symmetrical and unsymmetrical β-truxinic acids were obtained in high yields and as single diastereomers. The use of a template not only provides the alignment of the two olefins with suitable proximity (<4.2 Å) but also allows the heterodimerization of two different cinnamic acids, leading to unsymmetrical β-truxinic acid products.
Open Access
UV-induced acid-base chemistry within the PVC matrix: Wavelength selectivity
(ACS, Washington, DC, United States, 2000) Süzer, Şefik; Birer O.
The dehydrochlorination of polyvinyl chlorides (PVC) is investigated by using it as an in-situ Bronsted acid source, in blends with pH indicators for optical changes, and with basic forms of conducting polymers to determine the electrical conductivity changes. The in-situ created HCl was responsible for the optical and electrical conductivity changes in pH indicator+PVC and nonconducting electroactive polymer (PANI) or PANI+PVC systems. It was possible to sensitized PVC and trigger polyene formation at higher wavelengths. The nature of polyene formation was strongly dependent on the wavelength of irradiation as well as the amount of energy transferred to the matrix from the sensitizer.