Browsing by Subject "Porphyrin"
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Item Open Access A [5]Rotaxane-Based photosensitizer for photodynamic therapy(WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim, 2019) Özkan, Melis; Keser, Yağmur; Hadi, Seyed Ehsan; Tuncel, DönüşA [5]rotaxane was synthesized through a catalytically self‐threading reaction in which CB6 serves as a macrocycle and acts as a catalyst for the 1,3‐dipolar cycloaddition reaction between the alkyne substituted porphyrin core and azide functionalized stopper groups by forming triazole. Application of this rotaxane as a photosensitizer in photodynamic therapy against cancer cells and in bacteria inactivation have also been demonstrated. This photosensitizer has an excellent water solubility and remains stable in biological media at physiological pH (7.4) for prolonged times. It has the ability to generate singlet oxygen efficiently; while it shows no dark cytotoxicity up to 300 µm to the MCF7 cancer cell line, it is photocytotoxic even at 2 µm and reduces the cell viability to around 70 % when exposed to white light. It also displays light‐triggered biocidal activity both against gram‐negative bacteria (Escherichia coli, E. coli) and gram‐positive bacteria (Bacillus subtilis). Upon white light irradiation for 1 min with a flux of 22 mW/cm2 of E. coli suspension incubated with [5]rotaxane (3.5 µm), a killing efficiency of 96 % is achieved, whereas in the dark the effect is recorded as only around 9 %.Item Open Access Application of conjugated cucurbit[8]uril porphyrin supramolecular assembly in electrochemical hydrogen generation(Bilkent University, 2020-08) Aoudi, BouthainaThe ever-increasing demands for energy have encouraged an enormous consumption of fossil fuels worldwide. This has presented major concerns due to their limited resources and serious environmental issues. Therefore, the search for an alternative clean energy fuel has been intensively under study. In the past decade, hydrogen has attracted great attention as a promising fuel for the future. Hydrogen is an eco-friendly fuel that is readily abundant, highly efficient and clean since water is its only combustion product. Herein, this thesis highlights the synthesis and characterization of a novel supramolecular assembly based on cucurbit [8] uril -porphyrin functionalized on electrochemically reduced graphene oxide sheets for application in electrochemical hydrogen evolution. The study conveys optimization procedures for choosing the best catalytic system. Electrochemical analysis including potentiometry, cyclic voltammetry, chronoamperometry and electrochemical impedance spectroscopy were used to evaluate activity and stability. Characterization techniques were also performed to analyze the morphology and chemical structures of composites. Electrochemical studies demonstrated that ERGO: Ni-P composite (which comprises of a layer of graphene oxide drop-casted on FTO followed by a layer of nickel CB[8]-porphyrin) can serve as an excellent electrocatalyst for hydrogen evolution in alkaline medium. The composite exhibited high activity (onset potentialv -20 mV, 56.9 mmol h−1g −1 hydrogen, faradaic efficiency of 93% ), remarkable rate of charge transfer (Rct v 210 Ω), large electrochemical surface area (Cdl v1.67 mFcm−2 ) and significant stability without requiring additional noble metals.Item Open Access Application of covalent organic framework based on porphyrin and cucurbit[6]uril as a bifunctional electrocatalyst for hydrogen and oxygen evolution(Bilkent University, 2021-01) Sheidaei, YasamanThere is great apprehension about consumption of fossil fuels as well as the corresponding environmental issues which has evoked supreme efforts worldwide to develop clean and sustainable energy sources. Electrocatalytic water splitting producing both hydrogen and oxygen gas has shown considerable potential for energy conversion as hydrogen can meet the requirements for future energy demands. Hence it is of utmost importance to introduce novel electrocatalysts to overcome energy barriers for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). Here this thesis highlights the synthesis and characterization of a novel supramolecular assembly of cucurbit[6]uril and porphyrin and also examines its electrocatalytic activity toward both HER and OER. Electrochemical studies such as linear sweep voltammetry, chronoamperometry, chronopotentiometry, electrochemical impedance spectroscopy were performed to investigate the activity of the catalyst. The structural and morphological properties of sample were also studied using scanning electron microscopy (SEM), X-ray diffraction analysis (XRD), X-ray photoelectron spectroscopy (XPS) and Fourier-transform infrared spectroscopy (FT-IR). It was observed that the catalyst was able to show excellent electrocatalytic activity with onset potentials of -0.25 V (for HER) and 1.6 V (for OER) while producing 18.7 and 14.92 mmol.gr-1.hr-1 hydrogen and oxygen gas with faradaic efficiencies of 85% and 99%, respectively.Item Open Access Covalent organic framework constructed by clicking azido porphyrin with perpropargyloxy-cucurbit[6]uril for electrocatalytic hydrogen generation from water splitting(American Chemical Society, 2021-04-26) Khaligh, Aisan; Sheidaei, Yasaman; Tuncel, DönüşIn the present study, we describe the synthesis and characterization of a new covalent organic framework (COF-TPP-CB[6]) which was assembled together by clicking perpropargyloxy cucurbit[6]uril (CB[6]) to the azido-functionalized tetraphenylporphyrin (TPP-4N3) through a copper-catalyzed azide–alkyne cycloaddition reaction (CuAAC). Perpropargyloxy CB[6] was synthesized through the direct oxidation of CB[6] to afford perhydroxy CB[6] followed by subsequent O-propargylation using NaH. We also demonstrated that the resulting framework (COF-TPP-CB[6]) can be employed as an efficient and stable electrocatalyst for hydrogen evolution reaction (HER) in alkaline medium upon loading it with a nickel cocatalyst. The effect of TiO2 and different loadings of Ni on the HER performance of TPP-CB[6] was also studied. Herein, 12%Ni@TPP-CB[6] as the optimum catalyst showed an impressive H2 production rate of 18.7 mmol h–1 g–1 with a low onset potential of −250 mV.Item Open Access Cucurbit[7]uril-anchored porphyrin-based multifunctional molecular platform for photodynamic antimicrobial and cancer therapy(American Chemical Society, 2019) Özkan, Melis; Kumar, Yogesh; Keser, Yağmur; Hadi, Seyed E.; Tuncel, DönüşHere we report a photoactive supramolecular assembly that is multifunctional and constructed by covalently linking four receptor molecules (cucurbit[7]uril) to a porphyrin derivative with suitable linkers. While this molecular platform serves very efficiently as a light-triggered broad-spectrum antibacterial agent, owing to its negligible dark cytotoxicity and the presence of host molecules (CB7), it can also be utilized as a vehicle to carry drug molecules for a combined chemo and photodynamic cancer therapy.Item Open Access Cucurbituril-based supramolecular constructs for the diverse applications of nanomedicine(Bilkent University, 2020-08) Özkan, MelisThe supramolecular chemistry of cucurbiturils (CBs) has been rapidly advancing to span wide range of nanomedicine applications including but not limited to pharmaceutical drug formulation and delivery, bio/medical imaging and sensing, cancer therapy, tissue engineering, development of antibacterial/antiviral agents and protein modification. Owing to unique recognition properties and low cytotoxicity, the supramolecular assemblies of CBs are particular promises for biomedicine tasks. Inspired by these developments, three multifunctional supramolecular constructs of CBs containing photoactive conjugated compounds were prepared to be utilized in nanomedicine applications covering antimicrobial and anticancer photodynamic therapy (PDT), combined PDT and photothermal therapy (PTT) for the inactivation of bacteria, drug delivery and cellular imaging. A stable rotaxane, namely [5]-rotaxane, based on photoactive alkynesubstituted porphyrin and azide-substituted stopper group was synthesized through 1,3-dipolar cycloaddition reaction. Herein, cucurbit[6]uril (CB6) acts as both macrocycle and catalysis for the reaction and encapsulates formed triazole ring inside its cavity. [5]-rotaxane was further investigated and results revealed that it has ability to generate reactive oxygen species (ROS) including singlet oxygens in high yield even under quite low fluence of light and short exposure time and this, in turn, renders it ideal photosensitizer which remains stable at physiological pH (7.4) for prolonged times. By taking the advantages of aforementioned properties, [5]-rotaxane was employed as a broad-spectrum antibacterial agent against Gram-negative and Gram-positive bacteria as well as anticancer agent against human breast cancer cell line (MCF-7) via visible-light-induced generation of ROS. [5]-rotaxane possess negligible dark cytotoxicity upon complexation with CB6 and it can afford efficacious PDT of cancer and infectious diseases caused by bacteria. Another multifunctional photoactive supramolecular assembly was built through covalently binding of four cucurbit[7]uril (CB7) molecules, functioning as receptor, to a tetraphenyl porphyrin core using suitable linkers. In addition to its light-promoted antibacterial property, here, main objective was to combine chemo- and photodynamic cancer therapy which makes this study novel. Presence of CB7, enables host-guest interactions with anticancer drug, doxorubicin hydrochloride (DOX), and therefore this system was used to carry drug molecules achieving synergistic PDT and chemotherapy. Finally, CB7-capped hybrid nanoparticles (NPs) made up of red-emitting conjugated oligomer (COL) and gold nanoparticles (Au-NPs) were obtained through one-pot synthetic method. These hybrid NPs were found to own high photostability, thermal reversibility and high ROS generation capacity. Benefitting from these properties, combined photodynamic and photothermal killing efficiency of NPs towards Gram-positive and Gram-negative bacteria was verified. Additionally, cellular imaging capability of them was shown owing to their inherently fluorescent characteristics and this feature could be utilized for image-guided PDT applications.Item Open Access Glycosylated porphyrin-cucurbituril conjugate for photodynamic inactivation of bacteria and doxorubicin carriage for anticancer drug delivery(World Scientific Publishing, 2019-10) Özkan, Melis; Keser, Yağmur; Koç, Ahmet; Tuncel, DönüşPorphyrin derivatives are highly attractive in the construction of multifunctional molecular platforms with interesting properties and applications. In this regard, we report here the use of a multifunctional porphyrin-based molecular platform as a photosensitizer for photodynamic therapy and as a drug carrier. This molecular platform was constructed by conjugating a host molecule, cucurbit[7]uril to a triglycosylated tetraphenyl porphyrin and serves very efficiently as a photosensitizer in the inactivation of both gram-negative (Escherichia coli, E. coli) and gram-positive bacteria (Bacillus subtilis, B. subtilis) and growth inhibition of cancer cells as well as a doxorubicin (DOX) carrier for chemo-photodynamic dual cancer therapy. Another remarkable feature of this photosensitizer is that it shows negligible cytotoxicity in the dark.Item Open Access Rotaxanes and polyrotaxanes based on cucurbit[6]uril and porphyrin(Bilkent University, 2005) Cındır, NesibeItem Open Access Synthesis and characterization of cucurbituril based photoactive multifunctional assemblies(Bilkent University, 2019-01) Koç, AhmetPreparation of cucurbituril based functional materials and their use in various applications ranging from biomedicine to optoelectronics have been studied intensely over the last decade. Supramolecular assemblies, networks and nanostructures constructed through noncovalent interactions of cucurbiturils with -conjugated, photoactive compounds have also been investigated and potential applications in the areas of theranostics, imaging, sensing and catalysis have been shown. In these cucurbituril based architectures, however, cucurbituril is disabled to act as a molecular receptor since they do not involve the covalent conjugation of cucurbituril directly to chromophore. The main motivation of this study is to synthesize multifunctional assemblies and nanostructures in which cucurbituril is covalently attached to various conjugated compounds including porphyrin, conjugated oligomers and polymers. A new multifunctional porphyrin-cucurbituril conjugate based on a photoactive mannosylated porphyrin and monoporpargyloxycucurbit[7]uril was synthesized. Azido-functionalized tetraphenylporphyrin (TPP) was used as a building block. TPP was first mannosylated by copper-catalyzed azide-alkyne cycloaddition (CuAAC), then a monoporpargyloxycucurbit[7]uril was covalently attached to the mannosylated TPP with a second CuAAC reaction. Singlet oxygen generation efficiency of the supramolecular assembly was measured and found to be significantly higher than that of unfunctionalized TPP. ¹H NMR experiments were performed using a suitable guest, bisimidazolium, to prove the availability of CB7 in the assembly as a host. Bisimidazolium guest was observed to form inclusion complex with CB7, which is a promising result for the potential use of this supramolecular assembly as a drug carrier in conjunction with photodynamic therapy. Conjugated oligomers and polymers were synthesized from suitably- functionalized monomers via Pd-catalyzed cross-coupling reactions and their characterizations were performed. Their assemblies and nanostructures with covalently attached functionalized cucurbiturils were investigated. Redox sensitive crosslinked conjugated oligomer nanoparticles (CONs) were synthesized from a conjugated oligomer, OFVBt-N3 and a disulfide bond- containing crosslinker via ultrasound-assisted copper-free click reaction in THF. These spherical and approximately 50 nm-sized CONs preserved their stability and size («60 nm) after dispersing them in water. The behavior of the CONs in the presence of glutathione (GSH) was studied in aqueous medium. It was observed that the CONs are rapidly disrupted by GSH, which is an effective SS bond cleaving biomolecule that is overexpressed in cancer cells. These results imply that when nanoparticles are loaded with an anticancer drug, targeted delivery of the drug to cancer cells can be achieved by cooperative action of enhanced permeability and retention (EPR) effect and S-S bond cleavage by GSH.Item Open Access Synthesis of novel photoactive nanoparticles towards phototherapy(Bilkent University, 2021-09) Duah, Ishmeal KwakuNanomaterial-based compounds are attracting a lot of interest because many functionalities such as photoactive units, drugs and targeting groups can be combined on one platform to fight against infectious diseases and cancer. Recently, conjugated polymer-based nanomaterials have proven to be effective photosensitizers for antibacterial and photodynamic cancer therapies owing to their unique electronic and optical properties, including high singlet oxygen generation capacity, strong light-harvesting ability and its tunable optical spectrum. In this study, novel cross-linked conjugated polymer nanoparticles-based photosensitizers namely conjugated polymer-porphyrin nanoparticles (CPPN) and cross-linked conjugated polymer nanoparticles (PCP) were synthesized. The nanoparticles were prepared via nanoprecipitation using cucurbit[6]uril-(CB6)-catalyzed azide-alkyne cycloaddition (CB6-AAC) reaction. Conjugated polymer-porphyrin nanoparticles (CPPN) are advantageous than micelles incorporating porphyrin systems. For micelles containing porphyrin systems, the phototherapy effect of the porphyrin can only be seen after the porphyrin is released by conditions such as a change in pH, which is not the case for conjugated polymer-porphyrin nanoparticles (CPPN). The nanoparticles demonstrated high reactive oxygen species (ROS) generation efficiency which is evident in the antibacterial and anticancer photodynamic therapy (PDT) experiments. From the antibacterial photodynamic therapy experiment, when Gram-negative (Escherichia coli, E. coli) and Gram-positive (Bacillus subtilis, B. Subtilis and Staphylococcus aureus, S. aureus) bacteria were incubated with CPPN (20 µg/mL) and irradiated with white light (22 mW/cm2) for 10 min, more than 3.5-log reduction in colony-forming units (CFUs) was recorded for CPPN. Furthermore, when E. coli and B. subtilis were treated with PCP (24 µg/mL) and illuminated with light, about 3-log killing efficiency was recorded. However, in the dark, the nanoparticles demonstrated minimal dark cytotoxicity against the model bacteria. In addition, the anticancer photodynamic effect of CPPN and PCP on MCF-7 breast cancer cells was investigated. When MCF-7 breast cancer cells were treated with PCP in the dark and under light irradiation, almost all cells were alive for both cases. It may be that PCP could not generate enough reactive oxygen species to kill the cells. When MCF-7 breast cancer cells were treated with CPPN in the dark, the cell viability was 96% and upon irradiation with light for 20 minutes, the cell viability decreased to about 4%. Moreover, conjugated polymer-porphyrin-gold nanoparticles (CPPN-Au) and cross-linked conjugated polymer-gold nanoparticles (PCP-Au) nanoparticles were prepared, but due to the instability of the nanoparticles, they could not be used in phototherapy.