Yazar "Özalp, V. Cengiz" seçeneğine göre listele

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    A facile and efficient method of enzyme immobilization on silica particles via Michael acceptor film coatings: immobilized catalase in a plug flow reactor
    (Springer, 2016) Bayramoğlu, Gülay; Arıca, M. Yakup; Genç, Ayşenur; Özalp, V. Cengiz; İnce, Ahmet; Bıçak, Niyazi
    A novel method was developed for facile immobilization of enzymes on silica surfaces. Herein, we describe a single-step strategy for generating of reactive double bonds capable of Michael addition on the surfaces of silica particles. This method was based on reactive thin film generation on the surfaces by heating of impregnated self-curable polymer, alpha-morpholine substituted poly(vinyl methyl ketone) p(VMK). The generated double bonds were demonstrated to be an efficient way for rapid incorporation of enzymes via Michael addition. Catalase was used as model enzyme in order to test the effect of immobilization methodology by the reactive film surface through Michael addition reaction. Finally, a plug flow type immobilized enzyme reactor was employed to estimate decomposition rate of hydrogen peroxide. The highly stable enzyme reactor could operate continuously for 120 h at 30 degrees C with only a loss of about 36 % of its initial activity.
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    Adsorption and separation of immunoglobulins by novel affinity core-shell beads decorated with protein L and L-histidine
    (Elsevier Science Bv, 2013) Bayramoğlu, Gülay; Özalp, V. Cengiz; Arıca, M. Yakup
    A novel core shell beaded chromatographic materials was prepared by grafting of glycidyl methacrylate (GMA) on to the surface of poly(hydoxypropyl methacrylate/ethyleneglycol dimethacrylate), p(HPMA/EGDMA) beads via surface-initiated atom transfer radical polymerization (SI-ATRP). For grafting GMA, p(HPMA/EGDMA) beads were first modified with an ATRP initiator. A reaction with 2-bromo-2-methylpropionyl bromide of the hydroxyl groups of the beads led to ATRP initiator-covered surfaces. The grafted p(GMA) fibrous chains on the beads were decorated with two different ligands (i.e., Protein L and L-histidine) for separation of Immunoglobulin's (Igs) from aqueous solution in batch system. The maximum Igs adsorptions on the p(HPMA/EGDMA)-g-p(GMA)-Protein L and p(HPMA/EGDMA)-g-p(GMA)-L-histidine affinity beads were found to be 81.8 and 112.3 mg/g at pH 7.5 and 5.5, respectively. The purity of Igs from human serum was analyzed by HPLC. The Protein L immobilized affinity beads provided purity about 98%. The novel core shell polymeric beads decorated with Protein L showed a good selectivity for Igs molecules from diluted human serum. Adsorption studies of Igs onto Protein L and L-histidine immobilized affinity beads were also carried out in a continuous system. (C) 2013 Elsevier B.V. All rights reserved.
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    Antioxidant activity and hemocompatibility study of quercetin loaded plga nanoparticles
    (Shaheed Beheshti Univ, Sch Pharmacy, 2020) Derman, Serap; Uzunoğlu, Deniz; Acar, Tayfun; Arasoğlu, Tulin; Uçak, Samet; Özalp, V. Cengiz; Mansuroğlu, Banu
    Quercetin (QU) is an important flavonoid compound presenting lots of biological activities, but its application has been limited due to its low aqueous solubility and instability. In this study, conducted to improve these properties of the quercetin, quercetin-encapsulated PLGA nanoparticles were prepared, characterized, and evaluated for antioxidant and hemolytic activity. Nanoparticles were produced by single emulsion solvent evaporation method. Four different process parameters initial QU amount, PVA concentration, PVA volume, and initial PLGA amount were investigated to obtain the nanoparticles which have minimum particle size and maximum entrapment efficiency. Synthesized nanoparticles were evaluated for particle size, entrapment efficiency, and reaction yield. Additionally, antioxidant properties and in-vitro hemolytic activity of quercetin loaded nanoparticles with different particle size were also evaluated for the first time in the literature. The antioxidant activity results showed that nanoparticles have different antioxidant activity, depending on the amount of quercetin release from nanoparticles at different particle sizes. The hemolytic activity results show that all nanoparticles exhibited favorable compatibility to red blood cells and no significant hemolytic effect was observed.
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    Design of a core-shell type immuno-magnetic separation system and multiplex PCR for rapid detection of pathogens from food samples
    (Springer, 2013) Özalp, V. Cengiz; Bayramoğlu, Gülay; Arica, M. Yakup; Oktem, H. Avni
    We report an immuno-magnetic separation system developed by the immobilization of pathogen-specific antibodies on the core-shell magnetic beads. The magnetic beads were grafted with glycidylmethacrylate (GMA) using surface-initiated atom transfer radical polymerization (SI-ATRP). For immuno-magnetic separation (IMS) of target bacterial cells from others, antibodies for Escherichia coli and Salmonella enterica serovar Typhimurium cells were immobilized on the magnetic beads via glutaraldehyde coupling reaction. Our IMS system successfully separated Salmonella cells when the concentrations of target (i.e., Salmonella) and interfering (i.e., E. coli) cells were at the same level. Polymerase chain reaction (PCR) assays amplifying the rfb/rfbE region of the E. coli genome and a 647-bp fragment of the invA region of Salmonella were performed as the specific selection to accurately confirm the presence of E. coli and Salmonella, respectively. IMS and multiplex PCR methods can be used for specific and quantitative detection of pathogens from food samples. Thus, this study developed a reliable and direct system for rapid detection of Salmonella and E. coli in food samples. In addition, IMS method could be easily adapted to detect other pathogens by selecting the pertinent antibody.
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    Development of a paper-type tyrosinase biosensor for detection of phenolic compounds
    (Wiley-Blackwell, 2015) Şenyurt, Özge; Eyidoğan, Füsun; Yılmaz, Remziye; Öz, M. Tufan; Özalp, V. Cengiz; Arıca, Yakup; Öktem, Huseyin A.
    A low-cost, portable, and disposable paper-type tyrosinase biosensor was developed for determination of phenolic compounds, using a paper-strip absorption method. Tyrosinase and a chromophore (3-methyl-2-benzothiazolinone hydrazone) were immobilized on paper strips to manufacture the biosensor, which was tested on a nontoxic substrate (l-dopamine). The biosensor was responsive to phenolic compounds such as 4-chlorophenol, catechol, m-cresol, and p-cresol. The sensor showed stability for 70days. The developed biosensor can be used for remote on-site qualitative monitoring of phenolic compounds in wastewater samples.
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    Lysozyme specific aptamer immobilized MCM-41 silicate for single-step purification and quartz crystal microbalance (QCM)-based determination of lysozyme from chicken egg white
    (Elsevier, 2015) Bayramoğlu, Gülay; Özalp, V. Cengiz; Yılmaz, Meltem; Güler, Ulku; Salih, Bekir; Arıca, M. Yakup
    In the present study, MCM-41 silica particles were functionalized with 3-aminopropyltriethoxysilane (APTES) and characterized by FTIR, SEM, TEM and, Brunauer Emmett Teller (BET) analysis. A lysozyme specific aptamer was then immobilized onto amine functionalized MCM-41 particles via glutaraldehyde coupling, which were used for adsorption and purification of lysozyme. The effect of various parameters including pH, adsorbent dosage and lysozyme concentration on the lysozyme specific aptamer immobilized silica particles was evaluated. Efficiency of aptamer-silica particles in the purification of lysozyme from diluted chicken egg white was also realized. The optimal adsorption condition was in phosphate buffer (50 mmol L-1, pH 7.0) and the lysozyme adsorption capacity was 36.8 mg g(-1) polymer. Increasing the initial lysozyme concentration and temperature had a positive effect on the binding capacity, whereas increasing the ionic strength resulted in the opposite effect. The recovery of adsorbed lysozyme by elution with glycine buffer (0.2 mol L-1, pH 2.0) was about 93%. Additionally, proteins with different isoelectric points (e.g. lysozyme, albumin, cytochrome c and hemoglobin) were used as model proteins to investigate the selectivity of the lysozyme binding aptamer. The lysozyme aptamer was used in the purification of lysozyme from diluted chicken egg white, which was verified by a single SDS-PAGE band. The reusability studies showed that, about 87% of the initial adsorption capacity of the aptamer immobilized particles could be maintained after 20 cycles of purification. Finally, the specific interaction between lysozyme specific aptamer sequences and lysozyme was investigated by quartz crystal microbalance (QCM) biosensor for determination of lysozyme in the egg samples. (C) 2015 Elsevier Inc. All rights reserved.
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    Magnetic silica nanoparticle-Taq polymerase hybrids for multiple uses in polymerase chain reaction
    (Royal Soc Chemistry, 2015) Özalp, V. Cengiz; Bayramoğlu, Gülay; Arıca, M. Yakup
    Enzyme-magnetic nanoparticle hybrids have been employed as a strategy to improve the biocatalytic usability of biological molecules. For this purpose, we synthesized magnetic core-silica shell nanoparticles for direct one-step easy immobilization of Taq polymerase from a crude extract preparation. The hybrid magnetic particles were synthesized by a magnetic co-precipitation method. The magnetic particles were then coated with a 3-(triethoxysilyl)-propylamine (APTES)/tetraethoxysilane (TEOS) mixture, and the pendant -NH2 groups subsequently functionalized with glutaraldehyde for simultaneous immobilization of Taq-polymerase. The magnetic properties of the particles contributed to fast purification to eliminate inhibitory elements present in the crude extract during Taq polymerase isolation. The Taq-silica hybrid material performed with a similar efficiency to the solution-phase enzyme. Additionally, the new hybrid material allowed reuse of the enzyme multiple times. The silica-Taq polymerase hybrid lost 16% of its activity after 6 cycles. Most importantly, the silica microparticle immobilization extended the functional life of Taq polymerase at room temperature by facilitating a fast cleaning procedure.
  • Küçük Resim
    Öğe
    Removal of disperse red 60 dye from aqueous solution using free and composite fungal biomass of lentinus concinnus
    (Iwa Publishing, 2017) Bayramoğlu, Gülay; Özalp, V. Cengiz; Arıca, M. Yakup
    Lentinus concinnus biomass was immobilized to carboxyl derivative of cellulose, carboxymethyl cellulose (CMC), in the presence of FeCl3 (0.1 mol L-1) via ionic cross-linking. The beads containing immobilized fungal biomass were incubated at 30 degrees C for three days to permit growth of the fungus. The free and immobilized fungal biomass were tested for adsorption of Disperse Red 60 (DR-60) from aqueous solution using bare CMC beads as a control system. The maximum adsorption of DR-60 on the free and immobilized fungal biomass was observed at pH 6.0. The adsorption of DR-60 by the free, and immobilized fungal biomass increased as the initial concentration of DR-60 in the medium increased up to 100 mg/L. The maximum adsorption capacity of the CMC beads, the free and immobilized fungal biomass (i.e. composite beads) were found to be 43.4, 65.7, and 92.6 mg g(-1) dry sorbents, respectively. The equilibrium of the adsorption system was well described by Langmuir and Temkin isotherm models. Adsorption equilibrium was established in about 1.0 h. The adsorption of DR-60 on the fungal preparations followed pseudo-second-order kinetic model. It was observed that the immobilized fungal biomass has a high potential for the removal of DR-60 as a model dye from aqueous solution.
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    Small molecule detection by lateral flow strips via aptamer-gated silica nanoprobes
    (Royal Soc Chemistry, 2016) Özalp, V. Cengiz; Cam, Dilek; Hernandez, Frank J.; Hernandez, Luiza I.; Schafer, Thomas; Öktem, Hüseyin A.
    A fast, sensitive and ratiometric biosensor strategy for small molecule detection was developed through nanopore actuation. The new platform engineers together, a highly selective molecular recognition element, aptamers, and a novel signal amplification mechanism, gated nanopores. As a proof of concept, aptamer gated silica nanoparticles have been successfully used as a sensing platform for the detection of ATP concentrations at a wide linear range from 100 mu M up to 2 mM.