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Öğe Aptasensors for Small Molecule Detection(Verlag Z Naturforsch, 2012) Walter, Johanna-Gabriela; Heilkenbrinker, Alexandra; Austerjost, Jonas; Timur, Suna; Stahl, Frank; Scheper, ThomasAptamers are single-stranded oligonucleotides composed of RNA or DNA that are able to bind their corresponding targets via molecular recognition. Thus, aptamers can be thought of as nucleic acid-based alternatives to antibodies and have attracted attention as receptors in biosensors. Aptamers seem to be ideal biological recognition elements, since they enable the design of intelligent sensors based on their specific properties. Especially the fact that most aptamers undergo conformational changes during the binding of the target and their oligonucleotide nature can be used to rationally design novel sensing strategies. This review focuses on aptasensors for the detection of small molecules. In the first part, aptamers, their generation and their properties are briefly described. In the second part, different design strategies for aptasensors are reviewed, and examples for the detection of small molecules are given.Öğe Biofunctional quantum dots as fluorescence probe for cell-specific targeting(Elsevier Science Bv, 2014) Ag, Didem; Bongartz, Rebecca; Dogan, Leyla Eral; Seleci, Muharrem; Walter, Johanna-G.; Demirkol, Dilek Odaci; Stahl, Frank; Ozcelik, Serdar; Timur, Suna; Scheper, ThomasWe describe here the synthesis, characterization, bioconjugation, and application of water-soluble thioglycolic acid TGA-capped CdTe/CdS quantum dots (TGA-QDs) for targeted cellular imaging. Antihuman epidermal growth factor receptor 2 (HER2) antibodies were conjugated to TGA-QDs to target HER2-overexpressing cancer cells. TGA-QDs and TGA-QDs/anti-HER2 bioconjugates were characterized by fluorescence and UV-Vis spectroscopy, X-ray diffraction (XRD), hydrodynamic sizing, electron microscopy, and gel electrophoresis. TGA-QDs and TGA-QDs/anti-HER2 were incubated with cells to examine cytotoxicity, targeting efficiency, and cellular localization. The cytotoxicity of particles was measured using an MIT assay and the no observable adverse effect concentration (NOAEC), 50% inhibitory concentration (IC50), and total lethal concentration (TLC) were calculated. To evaluate localization and targeting efficiency of TGA-QDs with or without antibodies, fluorescence microscopy and flow cytometry were performed. Our results indicate that antibody-conjugated TGA-QDs are well-suited for targeted cellular imaging studies. (C) 2013 The Authors. Published by Elsevier B.V. All rights reserved.Öğe A case study on in vitro investigations of the potent biological activities of wheat germ and black cumin seed oil(Scientific Technical Research Council Turkey-Tubitak, 2015) Ag Seleci, Didem; Gumus, Zinar Pinar; Yavuz, Murat; Seleci, Muharrem; Bongartz, Rebecca; Stahl, Frank; Coskunol, Hakan; Timur, Suna; Scheper, ThomasThe objectives of this study were to investigate the potential biological activities of black cumin seed oil (BCSO) and wheat germ oil (WGO) on different cell lines. Initially, commercially available BCSO and WGO obtained by supercritical carbon dioxide extraction were analyzed in terms of tocopherol, aliphatic alcohols, and thymoquinone content via HPLC and GC analysis. Cell free antioxidant activities and total phenolic content of both oils were detected by DPPH assay and Folin-Ciocalteu method, respectively. As well as the DPPH assay, the protective effect against reactive oxygen species (ROS) was determined by microscopic observation of ROS generation in NIH-3T3 cells with or without oil samples by using an oxidation-sensitive fluorescent dye, H2DCFDA. Cytotoxicity was assessed using an MTT assay. In the case of BCSO, after exposing cells to 0.025-1.0 mg/mL and 1.0-100 mu g/mL concentrations for 24 h, the IC50 values of BCSO were 0.58, 0.51, 0.47, and 0.36 mg/mL for NIH-3T3, A549, U87, and HeLa cells, respectively. On the other hand, concentrations of WGO lower than 0.1 mg/mL did not cause a decrease in cell viability for all cell lines. Apoptotic and necrotic rates of these cell lines were investigated via flow cytometry. BCSO also exhibited proliferative efficacy for NIH-3T3 cells.Öğe Development of living cell microarrays using non-contact micropipette printing(Elsevier Science Bv, 2016) Jonczyk, Rebecca; Timur, Suna; Scheper, Thomas; Stahl, FrankDuring the last 30 years cellular screening systems were unidirectional developed towards high throughput applications on single cell level. We developed living cell microarrays, which provide an in vivo-like microenvironment for an advanced method to measure cellular response to external stimuli. To print living cells on glass slides, the classic microarray equipment, which involves printer and scanner, was fully transferred to suspensions of living cells. The microarray production was optimized using a contactfree spotting procedure in order to enhanced cell adhesion and growth rates. The printed model cells, A-549 (lung cancer cell line), were analyzed with conventional cell staining assays like DAPI (cell nuclei staining), calcein acetoxymethyl ester (viable cell staining), and CellTiter-Blue (R) Cell Viability Assay. After optimization, a reproducible (spot-to-spot variation: +/- 8.6 cells) printing method for small living cell amounts (1200 cells and fewer) was established that achieved cell viabilities of up to 88% for >0.6 mu L and good proliferation characteristics. Hence, this method could be advantageous for use in biomedical and diagnostic applications. (C) 2015 Elsevier B.V. All rights reserved.Öğe Folic acid-modified clay: targeted surface design for cell culture applications(Royal Soc Chemistry, 2013) Bongartz, Rebecca; Ag, Didem; Seleci, Muharrem; Walter, Johanna-G.; Yalcinkaya, Esra E.; Demirkol, Dilek Odaci; Stahl, Frank; Timur, Suna; Scheper, ThomasHere we report the preparation, characterization and application of folic acid modified Montmorillonite clay (FA-Mont) as a cell culture material. Clays exhibit unique properties such as good mechanical and chemical stabilities, high surface area, low toxicity and easy combination with functional organic groups. FA was used as a modifier to facilitate adhesion of folate positive cells on the clay surface. FA-Mont was characterized using FT-IR, XRD, zeta potential measurements as well as thermogravimetric analyses. Finally, the usage potential of FA-Mont as a receptor mediated cell adhesion material was successfully proved by using folate receptor (FR) rich HeLa and FR poor A-549 cells. The cell adhesion studies were monitored and imaged by fluorescence and scanning electron microscopy techniques.Öğe Folic acid-modified clay: targeted surface design for cell culture applications(Royal Soc Chemistry, 2013) Bongartz, Rebecca; Ag, Didem; Seleci, Muharrem; Walter, Johanna-G.; Yalcinkaya, Esra E.; Demirkol, Dilek Odaci; Stahl, Frank; Timur, Suna; Scheper, ThomasHere we report the preparation, characterization and application of folic acid modified Montmorillonite clay (FA-Mont) as a cell culture material. Clays exhibit unique properties such as good mechanical and chemical stabilities, high surface area, low toxicity and easy combination with functional organic groups. FA was used as a modifier to facilitate adhesion of folate positive cells on the clay surface. FA-Mont was characterized using FT-IR, XRD, zeta potential measurements as well as thermogravimetric analyses. Finally, the usage potential of FA-Mont as a receptor mediated cell adhesion material was successfully proved by using folate receptor (FR) rich HeLa and FR poor A-549 cells. The cell adhesion studies were monitored and imaged by fluorescence and scanning electron microscopy techniques.Öğe From Invisible Structures of SWCNTs toward Fluorescent and Targeting Architectures for Cell Imaging(Amer Chemical Soc, 2013) Ag, Didem; Seleci, Muharrem; Bongartz, Rebecca; Can, Mustafa; Yurteri, Seda; Cianga, Ioan; Stahl, Frank; Timur, Suna; Scheper, Thomas; Yagci, YusufSingle-walled carbon nanotubes (SWNTs) are unique nanostructures used as cargo systems for variety of diagnostic and therapeutic agents. For taking advantage of these structures in biological processes, they should be visible. Therefore, fluorescence labeling of SWCNTs with various probes is a significant issue. Herein, we demonstrate a simple approach for cell specific imaging and diagnosis by combining SWCNTs with a copolymer poly(para-epsilon-caprolactone) (PCL) side chains (PPP-g-PSt-PCL). In this approach PPP-g-PSt-PCL is noncovalently attached on carboxyl functional SWCNTs. The obtained fluorescent probe is bound to folic acid (FA) for targeted imaging of folate receptor (FR) positive HeLa cells. In vitro studies demonstrate that this conjugate can specifically bind to HeLa cells and indicate great potential for targeting and imaging studies.Öğe Nanostructured Amphiphilic Star-Hyperbranched Block Copolymers for Drug Delivery(Amer Chemical Soc, 2015) Seleci, Muharrem; Seleci, Didem Ag; Ciftci, Mustafa; Demirkol, Dilek Odaci; Stahl, Frank; Timur, Suna; Scheper, Thomas; Yagci, YusufA robust drug delivery system based on nanosized amphiphilic star-hyperbranched block copolymer, namely, poly(methyl methacrylate-block-poly(hydroxylethyl methacrylate) (PMMA-b-PHEMA) is described. PMMA-b-PHEMA was prepared by sequential visible light induced self-condensing vinyl polymerization (SCVP) and conventional vinyl polymerization. All of the synthesis and characterization details of the conjugates are reported. To accomplish tumor cell targeting property, initially cell-targeting (arginylglycylaspactic acid; RGD) and penetrating peptides (Cys-TAT) were binding to each other via the well-known EDC/NHS chemistry. Then, the resulting peptide was further incorporated to the surface of the amphiphilic hyperbranched copolymer via a coupling reaction between the thiol (-SH) group of the peptide and the hydroxyl group of copolymer by using N-(p-maleinimidophenyl) isocyanate as a heterolinker. The drug release property and targeting effect of the anticancer drug (doxorobucin; DOX) loaded nanostructures to two different cell lines were evaluated in vitro. U87 and MCF-7 were chosen as integrin alpha(v)beta(3) receptor positive and negative cells for the comparison of the targeting efficiency, respectively. The data showed that drug-loaded copolymers exhibited enhanced cell inhibition toward U87 cells in compared to MCF-7 cells because targeting increased the cytotoxicity of drug-loaded copolymers against integrin alpha(v)beta(3) receptor expressing tumor cells.Öğe Nanostructured Amphiphilic Star-Hyperbranched Block Copolymers for Drug Delivery(Amer Chemical Soc, 2015) Seleci, Muharrem; Seleci, Didem Ag; Ciftci, Mustafa; Demirkol, Dilek Odaci; Stahl, Frank; Timur, Suna; Scheper, Thomas; Yagci, YusufA robust drug delivery system based on nanosized amphiphilic star-hyperbranched block copolymer, namely, poly(methyl methacrylate-block-poly(hydroxylethyl methacrylate) (PMMA-b-PHEMA) is described. PMMA-b-PHEMA was prepared by sequential visible light induced self-condensing vinyl polymerization (SCVP) and conventional vinyl polymerization. All of the synthesis and characterization details of the conjugates are reported. To accomplish tumor cell targeting property, initially cell-targeting (arginylglycylaspactic acid; RGD) and penetrating peptides (Cys-TAT) were binding to each other via the well-known EDC/NHS chemistry. Then, the resulting peptide was further incorporated to the surface of the amphiphilic hyperbranched copolymer via a coupling reaction between the thiol (-SH) group of the peptide and the hydroxyl group of copolymer by using N-(p-maleinimidophenyl) isocyanate as a heterolinker. The drug release property and targeting effect of the anticancer drug (doxorobucin; DOX) loaded nanostructures to two different cell lines were evaluated in vitro. U87 and MCF-7 were chosen as integrin alpha(v)beta(3) receptor positive and negative cells for the comparison of the targeting efficiency, respectively. The data showed that drug-loaded copolymers exhibited enhanced cell inhibition toward U87 cells in compared to MCF-7 cells because targeting increased the cytotoxicity of drug-loaded copolymers against integrin alpha(v)beta(3) receptor expressing tumor cells.Öğe Nanostructured Amphiphilic Star-Hyperbranched Block Copolymers for Drug Delivery(Amer Chemical Soc, 2015) Seleci, Muharrem; Seleci, Didem Ag; Ciftci, Mustafa; Demirkol, Dilek Odaci; Stahl, Frank; Timur, Suna; Scheper, Thomas; Yagci, YusufA robust drug delivery system based on nanosized amphiphilic star-hyperbranched block copolymer, namely, poly(methyl methacrylate-block-poly(hydroxylethyl methacrylate) (PMMA-b-PHEMA) is described. PMMA-b-PHEMA was prepared by sequential visible light induced self-condensing vinyl polymerization (SCVP) and conventional vinyl polymerization. All of the synthesis and characterization details of the conjugates are reported. To accomplish tumor cell targeting property, initially cell-targeting (arginylglycylaspactic acid; RGD) and penetrating peptides (Cys-TAT) were binding to each other via the well-known EDC/NHS chemistry. Then, the resulting peptide was further incorporated to the surface of the amphiphilic hyperbranched copolymer via a coupling reaction between the thiol (-SH) group of the peptide and the hydroxyl group of copolymer by using N-(p-maleinimidophenyl) isocyanate as a heterolinker. The drug release property and targeting effect of the anticancer drug (doxorobucin; DOX) loaded nanostructures to two different cell lines were evaluated in vitro. U87 and MCF-7 were chosen as integrin alpha(v)beta(3) receptor positive and negative cells for the comparison of the targeting efficiency, respectively. The data showed that drug-loaded copolymers exhibited enhanced cell inhibition toward U87 cells in compared to MCF-7 cells because targeting increased the cytotoxicity of drug-loaded copolymers against integrin alpha(v)beta(3) receptor expressing tumor cells.Öğe PAMAM-functionalized water soluble quantum dots for cancer cell targeting(Royal Soc Chemistry, 2012) Akin, Mehriban; Bongartz, Rebecca; Walter, Johanna G.; Demirkol, Dilek Odaci; Stahl, Frank; Timur, Suna; Scheper, ThomasHerein, the phase-transfer reaction of quantum dots (QDs) with amine-terminated polyamidoamine (PAMAM) dendrimers with controllable ligand molar ratios was achieved. The unique properties of PAMAM allowed us to build up structurally and electrostatically stabilized water soluble QD complexes. Synthesized conjugates were characterized in terms of fluorescence and UV-Vis profiles, hydrodynamic size, number of surface dendrimer groups, and stability. Cytotoxic effects of conjugates for MCF-7, A-549 and HEP-G2 cancer cells were assessed based on cell viability using MTT assay. Cytotoxicity results were expressed as no observable adverse effect concentration (NOAEC), 50% inhibitory concentration (IC50) and total lethal concentration (TLC) values (mu M). Furthermore, HER2 receptor-mediated targeting efficiency of antibody labelled P/QDs conjugates was evaluated by successful staining of MCF-7 cells with bioconjugates. Uniquely, effective cell internalization was achieved with well-characterized antibody coupled P/QDs in contrast to antibody free P/QDs conjugates. Fluorescence microscopy images demonstrated that the designed PAMAM-derivatized QDs nanoparticles show great potential in the areas of cellular imaging and targeted therapy.
