Browsing by Subject "Conjugated oligomer"
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Item Open Access Cucurbit[7]uril-capped hybrid conjugated oligomer-gold nanoparticles for combined photodynamic-photothermal therapy and cellular imaging(ACS, 2020) Özkan, Melis; Tunç, İ.; Midilli, Y.; Ortaç, Bülend; Tuncel, DönüşHerein, hybrid nanoparticles composed of a redemitting conjugated oligomer (COL) and gold nanoparticles (Au-NPs) were prepared through a one-pot synthetic method in which the oligomer acts as a reducing agent as well as a matrix to wrap the newly formed Au nanoparticles. These hybrid nanoparticles(COL-Au-NPs) exhibited photodynamic and photothermal activity against both Gram-positive and Gram-negative bacterial strains. They were also proven to possess high photostability and thermal reversibility. Dark cytotoxicity of COL-Au-NPs toward pathogens and mammalian breast cancer cells (MCF-7) reduced significantly upon complexation with cucurbit[7]uril while preserving their light-induced cytotoxic activity when irradiated with a 915 nm laser for photothermal therapy and white light for photodynamic therapy, respectively. Furthermore, these nanoparticles have cellular imaging capability because of their intrinsic fluorescence characteristics and can be used in image-guided therapy.Item Open Access Modeling photoelectron spectra of conjugated oligomers with time-dependent density functional theory(American Chemical Society, 2010) Salzner, U.With the aim of producing accurate band structures of conjugated systems by employing the states of cations, TDDFT calculations on conjugated oligomer radical cations of thiophene, furan, and pyrrole with one to eight rings were carried out. Benchmarking of density functional theory and ab initio methods on the thiophene monomer shows that the ΔSCF ionization potential (IP) is most accurate at the B3LYP/6-311G* level. Improvement of the basis set beyond 6-311G* leads to no further changes. The IP is closer to experiment at B3LYP/6-311G* than at CCSD(T)/CCPVQZ. For longer oligomers the ΔSCF IPs decrease too fast with increasing chain length with all density functionals. CCSD/6-311G* performs well if the geometries are optimized at the CCSD level. With MP2 geometries IPs decrease too fast. Peak positions in photoelectron spectra were determined by adding appropriate TDDFT excitation energies of radical cations to the ΔSCF IPs. The agreement with experiment and with Green function calculations shows that TDDFT excited states of radical cations at the B3LYP/6-311G* level are very accurate and that absorption energies can be employed to predict photoelectron spectra.Item Open Access One-pot synthesis of hybrid core-shell nanoparticles for antibacterial photodynamic therapy(Bilkent University, 2019-07) Hadi, Seyed EhsanMultidrug resistance (MDR) in Escherichia coli (E. coli) has become a worrying issue that is not only increasingly observed in humans but also is widespread in veterinary medicine worldwide. Therefore, developing new and e ective alternatives to conventional antibiotics has become an imperative need. The idea of using photodynamic therapy (PDT) for bacterial eradication is a solution for the cases that the bacteria are resisting to conventional antibiotics. Although in these cases, PDT can be an option, PDT-killing efficiency might still not be sufficient, and some enhancements are necessary. Metal-enhanced singlet oxygen generation (ME1O2) is one of the ways to enhance the PDT-killing efficiency of the E. coli. Hybrid core-shell structures can serve conveniently for this purpose. These structures can combine the exible and tailorable features of polymers (shell) with the photophysical properties of plasmonic metals (core). In this work, using gold as a core and conjugated oligomer as a shell produced a novel hybrid core-shell nanoparticles which can enhance the singlet oxygen generation capacity and subsequently, improve the PDT-killing efficiency of the E. coli. In this structure, the shell is responsible for the spontaneous reduction of gold ions, forming gold nanoparticles and protecting them from the aggregation. With further investigation and optimization, the hybrid core-shell nanoparticles with the help of ME1O2 successfully improved the killing efficiency of E. coli bacteria by 40%.Item 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.