Browsing by Author "Caykara, Tuncer"

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A Novel Route To Prepare a Multilayer System Via the Combination of Interface-Mediated Catalytic Chain Transfer Polymerization and Thiol-Ene Click Chemistry
(Elsevier, 2017) Zengin, Adem; Caykara, Tuncer
Herein, we have designed a novel multilayer system composed of poly(methyl methacrylate) [poly(MMA)] brush, biotin, streptavidin and protein-A on a silicon substrate to attach on anti-immunoglobulin G (anti-IgG). poly(MMA) brush with vinyl end-group was first synthesized by the interface-mediated catalytic chain transfer polymerization. The brush was then modified with cysteamine molecules to generate the polymer chains with amine end-group via a thiol-ene click chemistry. The amine end-groups of poly(MMA) chains were also modified with biotin units to ensure selective connection points for streptavidin molecules. Finally, a multilayer system on the silicon substrate was formed by using streptavidin and protein-A molecules, respectively. This multilayer system was employed to attach anti-IgG molecules in a highly oriented manner and provide anti-IgG molecular functional configuration on the multilayer. High reproducibility of the amount of anti-IgG adsorption and homogeneous anti-IgG adsorption layer on the silicon surface could be provided by this multilayer system. The multi layer system with protein A may be opened the door for designing an efficient immunoassay protein chip. (C) 2017 Published by Elsevier B.V.
Sers Detection of Hepatitis B Virus Dna in a Temperature-Responsive Sandwich-Hybridization Assay
(Wiley, 2017) Zengin, Adem; Tamer, Ugur; Caykara, Tuncer
In this study, we report the design of a DNA sensor for the detection of a DNA sequence representative of the hepatitis B virus (HBV) based on a sandwich assay and surface-enhanced Raman scattering (SERS) measurement. The temperature-responsive hybrid silicon substrate was first prepared via immobilization of capture DNA strand at the surface of gold nanoparticles on the hybrid silicon substrate. A sandwich strategy was then applied for the detection of target DNA that brings a reporter DNA labeled with indocyanine green to the proximity of the surface, leading to high SERS signals. The temperature-responsive hybrid silicon substrate-based SERS platform can detect the remarkably lowest HBV DNA concentrations at similar to 0.44fm at 25 degrees C and similar to 0.14fm at 37 degrees C, respectively, which are comparable with the lowest HBV DNA concentration ever via other techniques. We expect this highly sensitive and robust hybrid silicon substrate-based SERS platform can be extended to detect other biomolecules and chemical species such as viruses, proteins, and small molecules without any labeling. Copyright (c) 2017 John Wiley & Sons, Ltd.
Sers Detection of Polyaromatic Hydrocarbons on a -Cyclodextrin Containing Polymer Brush
(Wiley, 2018) Zengin, Adem; Tamer, Ugur; Caykara, Tuncer
We have designed a new surface-enhanced Raman scattering (SERS) sensor composed of -cyclodextrin (-CD) containing poly(glycidyl methacrylate) (PGMA) brush coated silicon substrate and per-6-deoxy-(6-thio)--cyclodextrin (-CD-SH) modified gold nanoparticles for detection of polyaromatic hydrocarbons (PAHs; pyrene and anthracene). The -CD containing PGMA brushes were synthesized by the interface-mediated Reversible addition-fragmentation chain transfer (RAFT) polymerization of glycidyl methacrylate and followed an epoxide ring-opening reaction to attach -CD molecules. Some PAHs, such as pyrene and anthracene, can be introduced into the hydrophobic space of -CD, which allows them to detect the SERS of PAHs. After separating pyrene or anthracene from the solution by the -CD containing PGMA brush coated silicon substrate, they were sandwiched with the SERS substrate consisting of per-6-deoxy-(6-thio)--cyclodextrin and rhodamine 6G (Raman reporter) on gold nanoparticles. The correlation between PAH concentrations and SERS signal was found to be linear in the range of 2.5 to 10nM for anthracene and 10 and 25nM for anthracene. The limit of detection values for pyrene and anthracene are 0.8 and 2.4nM, respectively. Furthermore, the SERS sensor was also evaluated for the investigation of pyrene or anthracene specificity on different organic molecules and polyaromatic hydrocarbons.
Synthesis of Poly(n-(2 Methacrylamide) Brushes by Interface-Mediated Raft Polymerization
(Royal Soc Chemistry, 2016) Yildirim, Ertan; Cimen, Dilek; Zengin, Adem; Caykara, Tuncer
The synthesis of poly(N-(2-hydroxypropyl) methacrylamide) [poly(HPMA)] brushes is reported using an interface-mediated reversible addition-fragmentation chain transfer (RAFT) polymerization on a silicon substrate. To produce a RAFT agent immobilized surface, 4-cyano-4-(propylsulfanylthiocarbonyl)sulfanyl pentanoic acid was reacted with 9-decen-1-ol to form a self-assembled monolayer. Poly(HPMA) brushes and free polymers of varied molecular weights between 10 100 and 48 500 g mol(-1) were then synthesized by RAFT polymerization. The chemical characterization of the modified surfaces was examined using atomic force microscopy, grazing angle-Fourier transform infrared and X-ray photoelectron spectroscopy, ellipsometry and water contact angle measurements. The average distance between grafting sites (D, nm) and grafting density (sigma, chains per nm(2)) of poly(HPMA) brushes calculated from the dry film thickness (h, nm) and the number-average molecular weight ((M) over bar (n)) of the free polymers were 1.3 nm and 0.52 chains per nm(2), respectively, indicating moderate density polymer brush formation.