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Featured researches published by Sevil Dinçer.


Gene Therapy | 2005

Intelligent polymers as nonviral vectors

Sevil Dinçer; Mustafa Türk; Erhan Pişkin

The successful gene therapy largely depends on the vector type that allows a selective and efficient gene delivery to target cells with minimal toxicity. Nonviral vectors are much safer and cheaper, can be produced easily in large quantities, and have higher genetic material carrying capacity. However, they are generally less efficient in delivering DNA and initiating gene expression as compared to viral vectors, particularly when used in vivo. As nonviral vectors, polycations may work well for efficient cell uptake and endosomal escape, because they do form compact and smaller complexes with plasmid DNA and carry amine groups, which give positive charge and buffering ability that allows safe escape from endosome/lysosome. However, this is a disadvantage in the following step, which is releasing the plasmid DNA within the cytosol. In order to initiate transcription and enhance gene expression, the polymer/plasmid complex should dissociate after releasing from endosome safely and effectively. There are also other limitations with some of the polycationic carriers, for example, aggregation, toxicity, etc. Intelligent polymers, also called as ‘stimuli responsive polymers’, have a great potential as nonviral vectors to obtain site-, timing-, and duration period-specific gene expression, which is already exhibited in recent studies that are briefly summarized here.


European Polymer Journal | 2002

Radical copolymerization of N-isopropylacrylamide with anhydrides of maleic and citraconic acids

Sevil Dinçer; Volkan Köseli; Hande Kesim; Zakir M. O. Rzaev; Erhan Pişkin

Abstract Radical-initiated copolymerization of N -isopropylacrylamide (NIPA) with maleic (MA) and citraconic (CA) anhydrides was carried out in the presence of 2,2 ′ -azobisisobutyronitrile (AIBN) as an initiator in 1,4-dioxane at 65 °C under nitrogen atmosphere. Structure and monomer unit compositon of the copolymers obtained from a wide range of monomer feed were determined by elemental analysis (content of N for NIPA units), Fourier transform infrared and 1 H NMR spectroscopy. Monomer reactivity ratios for NIPA ( M 1 )–MA ( M 2 ) and NIPA ( M 1 )–CA ( M 2 ) pairs were determined by Kelen–Tudos (KT) and non-linear regression (NLR) methods using elemental and 1 H NMR spectroscopy analyses data. They are r 1 =0.45 and r 2 =0.08 (KT, N analysis), r 1 =0.44 and r 2 =0.10 (KT, 1 H NMR), r 1 =0.45 and r 2 =0.078 (NLR) for NIPA–MA monomer pair and r 1 =0.52 and r 2 =0.02, r 1 =0.44 and r 2 =0.04, r 1 =0.51 and r 2 =0.014 for NIPA–CA monomer pair, respectively. Observed tendency towards alternating copolymerization at ⩽50 mol% NIPA concentration in monomer feed and relatively high activity of NIPA growing radical was explained by H-bond formation between CO (anhydride) and NH (amide) fragments during chain growth reactions. Intrinsic viscosity, molecular weight and thermal behaviour of the synthesized copolymers were found to depend on the type of comonomer and the amount of NIPA units in the copolymers. These functional amphiphilic copolymers containing anion- and cation-active groups show both temperature and pH sensitivity and can be used for biological purposes as physiologically active macromolecular systems.


Journal of Biomaterials Science-polymer Edition | 2004

Gene delivery: intelligent but just at the beginning.

Erhan Pişkin; Sevil Dinçer; Mustafa Türk

Gene therapy is used to treat genetic disorders, which may be achieved both ex vivo and in vivo. Gene-delivery systems usually include a carrier system which both protects the gene expression plasmid and allows its extracellular and intracellular trafficking. Viruses are used in most of the clinical trials today; however, they do have important drawbacks. Non-viral vectors based on lipids, water-soluble polycations, other non-condensing polymers and nano- or microparticles/capsules have been proposed. Cationic polymers. especially carrying novel targeting ligands. are receiving increasing attention. Intelligent polymers with temperature, pH, and light sensitivities for a controllable and effective non-viral transfection have recently been introduced but are just at the beginning. Our preliminary studies showed that block copolymers of N-isopropylacrylamide-acrylic acid with poly(ethylene imine) could be one example of these novel non-viral vectors.


European Polymer Journal | 2003

Poly(N-isopropylacrylamide)/poly[(N-acetylimino)ethylene] thermosensitive block and graft copolymers

Geta David; Valentina Alupei; Bogdan C. Simionescu; Sevil Dinçer; Erhan Pişkin

Abstract Block and graft copolymers with poly(N-isopropylacrylamide) and poly[(N-acetylimino)ethylene] (PNAI) sequences were synthesized via PNAI derivatives (macroinitiators or macromers). The polymerization yields for block copolymers synthesized in ethanol, using the PNAI macroinitiator, were low (


Artificial Cells, Blood Substitutes, and Biotechnology | 2011

Potential c-myc Antisense Oligonucleotide Carriers: PCl/PEG/PEI and PLL/PEG/PEI

Sevil Dinçer; Mustafa Türk; Ayşe Karagöz; Gürhan Uzunalan

Abstract: In this work, positively charged, micelle-forming polymers were synthesized and used as a model vector to deliver antisense oligodeoxynucleotide (ASODN) into melanoma cells. Polymers and polymer/ASODN complexes were characterized by DLS according to size, charge, and critical micelle concentration. Nanosize and spherical complexes were observed by AFM. Complexes did not reveal significant toxicity to melanoma cells. Antiproliferative effect of the complexes was observed by immunocytochemical staining and estimated as 56.8% with N/P:9. High amount of apoptosis and very small amount of necrosis were estimated. According to the results, these positively charged polymers forming micelle-like structures seem promising as ASODN carriers.


Journal of Composites and Biodegradable Polymers | 2013

A Newly Designed Collagen-Based Bilayered Scaffold for Skin Tissue Regeneration

Gürhan Uzunalan; Merve Tuzlakoglu Ozturk; Sevil Dinçer; Kadriye Tuzlakoglu

In this study, a bilayered collagen-based membrane was prepared to mimic skin structure as a potential candidate for wound dressing application. To achieve the desired bilayered structure similar to skin, freeze-drying and electrospinning methods were used consecutively. The macroporous sublayer was prepared by freeze-drying of collagen intended for the absorption of exudates, while the upper layer was electrospun onto the freeze-dried part as an impermeable part to microorganisms. Nanofiber layer was loaded with silver nanoparticles for antibacterial activity. In order to improve biostability, double-layered materials were crosslinked by glutaraldehyde vapor. The morphology of the developed structures was assessed by SEM and the integrity of two layers was confirmed. The water uptake capacity of the scaffolds in physiological conditions was found to be around 738%. Afterwards, silver nanoparticles were sprayed to the upper part in order to obtain an antibacterial layer, and fibrinogen was immobilized to the sublayer for the stimulation of healing process. Agar zone inhibition test showed the antibacterial characteristics of the scaffolds. By providing structural and chemical similarity to natural skin tissue, the designed material can be a potential scaffold for skin tissue regeneration.


Journal of Tissue Engineering and Regenerative Medicine | 2009

Growth inhibition of SK‐MEL‐30 human melanoma cells by antisense c‐myc oligonucleotides delivered by poly(N‐isopropylacrylamide)/ poly(ethyleneimine) copolymer

Sevil Dinçer; E. K. Oskay; A. K. Piskin; N. D. Zeybek; Erhan Pişkin

The c‐myc oncogene has been shown to be overexpressed in a number of malignancies and plays a key role in the abnormal growth regulation of melanoma cells. This study aimed to provide an efficient system for the in vitro manipulation of c‐myc expression by antisense oligonucleotides. Therefore, we used poly(NIPA)/PEI2B copolymer as vector in order to improve the intracellular availability and stability of AS ODNs. We targeted oligonucleotide sequences within the human c‐myc mRNA as free AS ODNs or conjugated with a thermosensitive copolymer, in an effort to inhibit the growth of human melanoma cells. The conjugates adopted more positive charge and smaller size at 37 °C and they had no toxic effects on human fibroblast cells. The conjugated AS ODNs showed increased antiproliferative effect on melanoma cells as compared to free AS ODNs. At a concentration of 100 ng, AS ODNs inhibited SK‐MEL 30 human melanoma cell line proliferation maximally by 18.6%, whereas the same amount of conjugated AS ODN provided 52% inhibition. The greatest inhibition was obtained by conjugates having a polymer:AS ODN ratio of 9. Greatest inhibition was detected at 48 h and decreased after 96 h, which may be due to the depletion of AS ODNs. The results confirm the enhanced antiproliferative effects of poly(NIPA)/PEI2B‐conjugated AS ODNs, which may provide improved intracellular availability for c‐myc‐directed antisense strategies. Copyright


Progress in Polymer Science | 2007

Functional copolymers of N-isopropylacrylamide for bioengineering applications

Zakir M. O. Rzaev; Sevil Dinçer; Erhan Pişkin


Langmuir | 2007

Adsorption behavior of linear and cyclic genetically engineered platinum binding peptides

Urartu Ozgur Safak Seker; Brandon Wilson; Sevil Dinçer; Il Won Kim; Ersin Emre Oren; John Spencer Evans; Candan Tamerler; Mehmet Sarikaya


Journal of Controlled Release | 2004

In vitro transfection of HeLa cells with temperature sensitive polycationic copolymers.

Mustafa Türk; Sevil Dinçer; Isik G. Yulug; Erhan Pişkin

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Murat Topuzogullari

Yıldız Technical University

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Nevin Gül Karagüler

Istanbul Technical University

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Ayşe Karagöz

Yıldız Technical University

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Gürhan Uzunalan

Yıldız Technical University

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