Mehmet Senel

Synthesis, characterization and antimicrobial activity of water soluble dendritic macromolecules.

Several families of water soluble dendrimers were synthesized based on poly(propyleneoxide) amines (Jeffamines) (P(1)). P(1)-core and branched units were constructed from both methylacrylate and ethylenediamine (P(2)-P(9), and generations 0-3 with -NH(2), -COOH functionalities). They were characterized by elemental analysis (EA), gel permeation chromatography (GPC), FT-IR, (1)H, and (13)C NMR. The antimicrobial activities of only water soluble compounds (P(1), P(3), P(4), P(6), P(7) and P(9)) were evaluated using disk diffusion method in water as well as the minimal inhibitory concentration (MIC) dilution method against 9 bacteria. The obtained results from disk diffusion method are assessed in side-by-side comparison with those of Penicillin-g, Ampicillin, Cefotaxime, Vancomycin, Oflaxacin, and Tetracycline, well-known antibacterial agents. The results from dilution procedure are compared with Gentamycin as antibacterial and Nystatin as antifungal. The antifungal activities are reported on five yeast cultures namely, Candida albicans, Kluyveromyces fragilis, Rhodotorula rubra, Debaryomyces hansenii, and Hanseniaspora guilliermondii, and the results are referenced with Nystatin, Ketaconazole, and Clotrimazole, commercial antifungal agents. In most cases, the compounds show broad-spectrum (gram-positive and gram-negative bacteria) activities that are comparatively higher or equipotent to the antibiotic and antifungal agents in the comparison tests.

Highly sensitive detection of cancer cells with an electrochemical cytosensor based on boronic acid functional polythiophene

The detection of cancer cells through important molecular recognition target such as sialic acid is significant for the clinical diagnosis and treatment. There are many electrochemical cytosensors developed for cancer cells detection but most of them have complicated fabrication processes which results in poor reproducibility and reliability. In this study, a simple, low-cost, and highly sensitive electrochemical cytosensor was designed based on boronic acid-functionalized polythiophene. In cytosensors fabrication simple single-step procedure was used which includes coating pencil graphite electrode (PGE) by means of electro-polymerization of 3-Thienyl boronic acid and Thiophen. Electrochemical impedance spectroscopy and cyclic voltammetry were used as an analytical methods to optimize and measure analytical performances of PGE/P(TBA0.5Th0.5) based electrode. Cytosensor showed extremely good analytical performances in detection of cancer cells with linear rage of 1×101 to 1×106 cellsmL-1 exhibiting low detection limit of 10 cellsmL-1 and incubation time of 10min. Next to excellent analytical performances, it showed high selectivity towards AGS cancer cells when compared to HEK 293 normal cells and bone marrow mesenchymal stem cells (BM-hMSCs). This method is promising for future applications in early stage cancer diagnosis.

Preparation and characterization of amine functional nano-hydroxyapatite/chitosan bionanocomposite for bone tissue engineering applications

In this study, three different types of scaffolds including a uniquely modified composite scaffold - namely chitosan (CTS), nano-hydroxyapatite/chitosan composite (CTS+nHAP), and amine group (NH2) modified nano-hydroxyapatite/chitosan composite (CTS+nHAP-NH2) scaffolds - were synthesized for bone tissue engineering (BTE) purposes. As results of the study, it was found that all scaffold types were biodegradable with CTS and CTS+nHAP scaffolds losing up to 15% of their initial weight, while the CTS+nHAP-NH2 scaffold showing 10% of weight loss after six weeks of lysozyme treatment. In addition, all three types of scaffolds were shown to be biocompatible, and amongst them CTS+nHAP-NH2 scaffolds supported the most cell proliferation in WST-1 assay and expressed the least and acceptable level of cytotoxicity in lactate dehydrogenase (LDH) test for human bone mesenchymal stem cells (hBM-MSCs). Finally, during osteoinductivity assessment, CTS+nHAP-NH2 nearly tripled initial alkaline phosphatase (ALP) activity when whereas both CTS and CTS+nHAP scaffolds only doubled. These results indicate that all synthesized scaffold types under investigation have certain potential to be used in bone tissue engineering approaches with CTS+nHAP-NH2 scaffold being the most promising and applicable one. In the future, we plan to intensify our studies on osteogenic differentiation on our scaffolds on a detailed molecular level and to include in vivo studies for pre-clinical purposes.

Preparation and in vitro evaluation of 5-flourouracil loaded magnetite–zeolite nanocomposite (5-FU-MZNC) for cancer drug delivery applications

In this work, super paramagnetic magnetite nanoparticles were synthesized onto/into zeolite, then loaded with anti-cancer drug 5-fluorouracil (5-FU). The physical properties of the prepared nanocomposite and drug loaded nanocomposite were characterized using different techniques. The drug loading and releasing behavior of the magnetic nanocarrier was investigated and the drug-loaded nanoparticles exhibited a sustained release of drug without any burst release phenomenon. Furthermore, 5-FU loaded MZNC were evaluated for its biological characteristics. The functional 5-FU-MZNC has been triggered intra-cellular release of the cancer therapeutic agent 5-fluorouracil (5-FU). Cytotoxic effects of 5-FU loaded MZNC on human gastric carcinoma (AGS) cells were determined by real time cell analysis and colorimetric WST-1 cell viability assay. Apoptosis of cells was further investigated by Annexin-V staining which indicates the loss of cell membrane integrity. According to our results, 5-FU-MZNC showed a concentration-dependent cell proliferation inhibitory function against AGS cells. Morphologic and apoptotic images were consistent with the cytotoxicity results. In conclusion, 5-FU loaded MZNC efficiently inhibit the proliferation of AGS cells in vitro through apoptotic mechanisms, and may be a beneficial agent against cancer, however further animal study is still required.

Novel impedimetric dopamine biosensor based on boronic acid functional polythiophene modified electrodes

In this study we report a new, simple and first impedimetric biosensor based on 3-Thienyl boronic acid for dopamine detection. Biosensor electrode preparation is 1min long by simple electro-polymerization of 3-Thienyl boronic acid and copolymer Thiophene P(TBA0.50Th0.50). Strong interaction between dopamine and thin layer of boronic acid has provided bio-sensing electrode high selectivity and stability, linear range of 7.8 to 125μM, and detection limit of 0.3μM. Characterization and optimization studies were conducted using electrochemical impedance spectroscopy (EIS) and cyclic voltammogram (CV). In order to test reliability of proposed biosensor real sample application study has been conducted using non-diluted human urine and it has been found that biosensor selectivity and recovery is excellent. As well P(TBA0.50Th0.50) based electrode and dopamine interaction has been proven by single frequency impedance measurements. Biosensors acquired good reproducibility, stability, selectivity and very low interference.

Evaluation of Jeffamine®-cored PAMAM dendrimers as an efficient in vitro gene delivery system†

In this study, we investigated gene delivery properties of Jeffamine-cored polyamidoamine (PAMAM) dendrimers (JCPDs). The effects of dendrimer concentration, generation, and core size on the gene delivery have been analyzed. The experimental results showed that the JCPD effectively delivered plasmid DNA inside the HeLa cells, and the transfection efficiency improved considerably as the number of generation increased. The cytotoxicity of JCPD in different concentration was tested for HeLa cell line. JCPD was complexed with a lacZ gene carrying plasmid and tested for transfection efficiency using quantitative β-galactosidase expression assay. Additionally, confocal microscopy results revealed that JCPD effectively delivered green fluorescent protein-expressing plasmid into HeLa cells and produced fluorescent signal with satisfactory efficiency. The highest transfection efficiency was obtained from JCPDs G4 and G5, which mixed with expression plasmid vectors at a 10/1 weight ratio. These results indicated that under optimized conditions, JCPD can be considered as an efficient transfection reagent and can be effectively used for gene delivery applications.

Construction of ferrocene modified conducting polymer based amperometric urea biosensor

Herein, an electrochemical urea sensing bio-electrode is reported that has been constructed by firstly electropolymerizing 4-(2,5-Di(thiophen-2-yl)-1H-pyrrol-1-yl)aniline monomer (SNS-Aniline) on Pencil Graphite Electrode (PGE), then modifying the polymer coated electrode surface with di-amino-Ferrocene (DAFc) as the mediator, and lastly Urease enzyme through glutaraldehyde crosslinking. The effect of pH, temperature, polymer thickness, and applied potential on the electrode current response was investigated besides performing storage and operational stability experiments with the interference studies. The resulting urea biosensors amperometric response was linear in the range of 0.1-8.5mM with the sensitivity of 0.54μA/mM, detection limit of 12μM, and short response time of 2s. The designed bio-electrode was tested with real human blood and urine samples where it showed excellent analytical performance with insignificant interference.

Preparation and characterization of novel chitosan/zeolite scaffolds for bone tissue engineering applications

ABSTRACT In this study, chitosan-based novel scaffolds containing zeolite A were fabricated by freeze-drying technique. The nanocomposite scaffolds were prepared from chitosan and zeolite A nanocrystals with different amounts (0.5, 1.0, and 2.0%) in aqueous media. The zeolite A nanocrystals and nanocomposite scaffolds were characterized by using FTIR, X-ray powder diffraction, scanning electron microscope, and thermogravimetric analysis. The scaffolds were seeded with bone marrow-derived human mesenchymal stem cell line (UE7T-13), and cell attachment, viability, and cytotoxicity assays were performed. In vitro cytotoxicity of scaffolds toward human mesenchymal stem cell line was evaluated through the evaluation of cell viability and cell attachment assays. GRAPHICAL ABSTRACT

Photodynamic therapy application of PAMAM-porphyrin molecule on stomach cancer cells

In this study, effect of a novel LED-based light source developed for 96-well-plates cell culture applications, was tried on AGS stomach cancer cell line, in combination with Poly(amido amine) (PAMAM) modified – porhyrin molecule. For each 4 generation of modified PpIX molecule 5 different concentrations tried. According to results PAMAM molecule doesnt have any photosensitizer property also didn’t show any toxic effect even if higher concentrations. Morphology and real time monitoring analysis results hold up each other and confirmed that, PpIX molecules with and without modificated high concentrations (>100μM) caused cell death via toxicicity this reason optimal concentration for PAMAM modified PpIX should be between 25 - 50 μm concentration .

Preparation and conductivities of polyacrylic acid/polyvinylimidazole grafted and ungrafted iron oxide nanocomposite polymer electrolytes

AbstractNanocomposites of Polyacrylic acid/polyvinylimidazole (PAA/PVI) with grafted and ungrafted iron oxide nanoparticles were prepared by a Reflux method. The Fe3O4 nanoparticles with 10 nm average diameter were synthesized by controlled co-precipitation and silanization of Si-PVI on Fe3O4 was used to obtain the grafted ones. Grafting becomes important at composites of less PVI that cause drastic decreases in AC conductivity. The content of PVI has important effects on the conductivity mechanism of these composites. The effect of grafting and Polyacrylic acid/polyvinylimidazole molar ratio on the conduction mechanism were studied. The conduction mechanism of iron oxide nanocomposites can be adjusted by changing molar ratio of Polyacrylic acid/polyvinylimidazole and grafting of Fe3O4 NPs.