Ramazan Ozturk

Synthesis, Characterization and EPR Studies of Supramolecular Porphyrazines

Supramolecular porphyrazines with eight pyridine donor groups bound through ethylthio ester bridges on the periphery have been prepared. The pyridine donors were quaternized with iodomethane to octacationic porphyrazine. The nonanuclear supramolecular porphyrazine was prepared by the coordination of peripheral pyridine donors with VO(acac)2. The paramagnetic nonanuclear structure was studied in powder and in solution form by EPR. EPR studies together with the other spectral data confirmed the presence of identical pyridine-coordinated VO(acac)2 paramagnetic centers attached to the peripheral positions of the porphyrazine core.

SYNTHESIS AND ESR STUDIES OF A SOLUBLE VANADYL PORPHYRAZINE

Octakis(hexylthio)vanadyl porphyrazinate, (VOPz), was prepared from vanadyl(IV) sulfate and metal-free porphyrazine (H2Pz), which was synthesized by the cyclotetramerization of the corresponding dinitrile derivative and further treatment with trifluoroacetic acid. Intense absorption peaks at 699 and 352 nm in the electronic spectrum indicated the C4v symmetry of VOPz. ESR studies, both in solution and in powder form, confirmed the proposed structure.

Delivery of lipophilic porphyrin by liposome vehicles: Preparation and photodynamic therapy activity against cancer cell lines

Porphyrin photosensitizers are mostly used components in photodynamic therapy (PDT). The poor solubility of porphyrins in aqueous medium is the problem to be solved for the in vivo applications. The delivery of photosensitizers to the tumor cells using liposome vehicles can help to overcome this problem. In this work, we have first functionalized the protoporphyrin IX with lipophilic oleylamine arms and encapsulated it into 1,2 dioleyl-sn-glycero-phosphatidylcholine (DOPC) liposomes. The appropriate sizes of liposomes are about 140 nm and have the characteristic Soret and Q band absorptions at 405 nm (Soret), 507 nm, 541 nm, 577 nm and 631 nm (Q bands), respectively. In the photodynamic activity studies, the liposomal porphyrins were irradiated with light (375 nm, 10 mW) in the presence of cancer cell lines, HeLa and AGS. We have found that both liposomal porphyrins and oleylamine conjugated porphyrins are much more effective than PpIX. This result can be attributed to the drug delivery characteristic of the liposomes which plays effective role in endocytosis. We also found that, in AGS cells, liposomal PpIX-Ole induced apoptosis more than HeLa cells under light conditions.

Influence of gold nanoparticle architecture on in vitro bioimaging and cellular uptake

Gold nanoparticles (GNPs) are favorable nanostructures for several biological applications due to their easy synthesis and biocompatible properties. Commonly studied GNP shapes are nanosphere (AuNS), nanorod (AuNR), and nanocage (AuNC). In addition to distinct geometries and structural symmetries, these shapes have different photophysical properties detected by surface plasmon resonances. Therefore, choosing the best shaped GNP for a specific purpose is crucial to the success of the application. In this study, all three shapes of GNP were investigated for their potency to interact with cell surface receptors. Anti-HER2 antibody was conjugated to the surface of nanoparticles. MCF-7 breast adenocarcinoma and hMSC human mesenchymal cell lines were treated with GNPs and analyzed for cellular uptake and bioimaging efficiencies using the UV–vis spectroscopy and dark-field microscopy.

Highly sensitive shape dependent electro-catalysis of TNT molecules using Pd and Pd–Pt alloy based nanostructures

This study demonstrates the fabrication of a highly sensitive electrochemical sensor designed for the quantification of 2,4,6-trinitrotoluene (TNT). The devised sensor system relies on the electro-catalytic reduction of TNT molecules achieved at the surface of palladium (Pd) and palladium-platinum (Pd–Pt) alloy nanostructure modified glassy carbon electrodes (GCEs). The electrode based reduction was studied in a competitive manner with Pd nanocubes (Pd NCs) in comparison to Pd hollow nanospheres (Pd HNS) and Pd–Pt alloy nanostructures (Pd–Pt NA). The experiments revealed Pd NCs to possess high catalytic capability in comparison to their other competitors where relatively greater signal sensitivity suggested the importance of shape-dependence electro-catalysis. The Pd NCs based sensor was found to be highly sensitive towards TNT molecules with detection limits up to 0.01 ppm and a working window of 0.1–7.0 ppm. Moreover, the Pd NCs based sensor demonstrated excellent selectivity in the presence of other common nitro-aromatic compounds. In addition, the excellent recoveries obtained in the real matrix environment (tap water) further promise the real-time application of the developed sensor for trace level detection of TNT.