Browsing by Subject "Photosensitizers"

Now showing 1 - 10 of 10

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
Bodipy-based photosensitizers with long alkyl tails at the meso position: efficient singlet oxygen generation in Cremophor-EL micelles
(Elsevier Ltd, 2016) Kilic, B.; Yesilgul, N.; Polat, V.; Gercek, Z.; Akkaya, E. U.
Bodipy dyes with n-decyloxyphenyl-(4, 5) and pentadecyl-(8) meso substituents can easily embed themselves into micellar structures formed from Cremophor-EL. In micelles of approximately 20 nm median size, heavy-atom substituted dyes show remarkable photosensitization properties as evidenced by the rate of reaction with an anthracene-based selective singlet oxygen trap in buffered aqueous solutions. Considering the ease of Bodipy derivatization and the advantages of Cremophor-EL carried therapeutic agents, these photosensitizing agents may offer novel targeting opportunities and enhanced chemical and photophysical stability.
Open Access
“Clicked” Porphyrin-cucurbituril conjugate: a new multifunctional supramolecular assembly based on triglycosylated porphyrin and Monopropargyloxycucurbit[7]uril
(Wiley-VCH Verlag, 2018) Koç, Ahmet; Khan, Rehan; Tuncel, Dönüş
The design, synthesis, and characterization of a new multifunctional supramolecular assembly based on a photoactive glycosylated porphyrin and covalently attached monofunctionalized cucurbit[7]uril (CB7) are reported. To obtain the target supramolecular assembly, azido-functionalized tetraphenylporphyrin (TPP) was used as a building block. TPP was first glycosylated by copper-catalyzed azide-alkyne cycloaddition (CuAAC) reaction, then a monopropargyloxy-functionalized-CB7 unit was conjugated to glycosylated TPP with a second CuAAC reaction. The host-guest chemistry of the assembly was investigated by 1H NMR experiments to establish the availability of the CB7 as a host. The imidazole-based guest, which is known to have high affinity toward CB7, was observed to form inclusion complex with CB7. It was also demonstrated that this supramolecular assembly can serve as an efficient photosensitizer for the generation of singlet oxygen.
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
Optimization of distyryl-Bodipy chromophores for efficient panchromatic sensitization in dye sensitized solar cells
(2011) Kolemen, S.; Cakmak, Y.; Ertem, E.; Bozdemir, O. A.; Erten-Ela, S.; Marszalek, M.; Yum, Jun-Ho; Zakeeruddin, S.; Nazeeruddin, M.; Gratzel, M.; Akkaya, E. U.
Versatility of Bodipy (4,4-difluoro-4-bora-3a,4a-diaza-s-indacene) dyes was further expanded in recent dye-sensitized solar cell applications. Here we report a series of derivatives designed to address earlier problems in Bodipy sensitized solar cells. In the best case example, an overall efficiency of a modest 2.46% was achieved, but panchromatic nature of the dyes is quite impressive. This is the best reported efficiency in liquid electrolyte solar cells with Bodipy dyes as photosensitizers.
Open Access
PEGylated calix[4]arene as a carrier for a Bodipy-based photosensitizer
(Elsevier, 2014) Cakmak, Y.; Nalbantoglu, T.; Durgut, T.; Akkaya, E. U.
Heavy atom substituted Bodipy compounds, unlike the parent chromophore, undergo rapid intersystem crossing to generate singlet oxygen, which is the primary cytotoxic agent exploited in PDT. In this work, we show that an organic soluble calix[4]arene can be functionalized by Knoevenagel reaction and then converted into an amphiphilic photosensitizer in a few steps. In addition to generating a potentially useful photosensitizer, the sequence of reactions is the first use of a Bodipy dye as a chromophoric/fluorogenic label without the typical reactive functional groups.
Open Access
Remote-controlled release of singlet oxygen by the plasmonic heating of endoperoxide-modified gold nanorods: towards a paradigm change in photodynamic therapy
(Wiley-VCH Verlag, 2016) Kolemen, S.; Ozdemir, T.; Lee, D.; Kim, G. M.; Karatas, T.; Yoon, J.; Akkaya, E. U.
The photodynamic therapy of cancer is contingent upon the sustained generation of singlet oxygen in the tumor region. However, tumors of the most metastatic cancer types develop a region of severe hypoxia, which puts them beyond the reach of most therapeutic protocols. More troublesome, photodynamic action generates acute hypoxia as the process itself diminishes cellular oxygen reserves, which makes it a self-limiting method. Herein, we describe a new concept that could eventually lead to a change in the 100 year old paradigm of photodynamic therapy and potentially offer solutions to some of the lingering problems. When gold nanorods with tethered endoperoxides are irradiated at 808 nm, the endoperoxides undergo thermal cycloreversion, resulting in the generation of singlet oxygen. We demonstrate that the amount of singlet oxygen produced in this way is sufficient for triggering apoptosis in cell cultures. EPT sees the light: When gold nanorods with tethered endoperoxides are irradiated with near-infrared light, the endoperoxides undergo thermal cycloreversion, resulting in the generation of singlet oxygen. The amount of singlet oxygen generated by these nanocomposites is sufficient for triggering apoptosis in cell cultures.
Open Access
Synthesis and investigation of singlet oxygen production efficiency of photosensitizers based on meso-phenyl-2,5-thienylene linked porphyrin oligomers and polymers
(Royal Society of Chemistry, 2015) Khan, R.; Idris, M.; Tuncel, D.
Three new Zn(ii)-, oligo- and poly(2,5-thienylene)-linked porphyrins, bearing multiple triethylene glycol (TEG) groups, on all meso aryl positions were synthesized via Stille and Suzuki coupling reactions and their photophysical properties as well as singlet oxygen generation efficiencies have been investigated to elucidate the possibility of their use as a photosensitizer for photodynamic therapy (PDT) and photodynamic inactivation of bacteria. © The Royal Society of Chemistry 2015.