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Öğe Activation of the Mas receptors by AVE0991 and MrgD receptor using alamandine to limit the deleterious effects of Ang II-induced hypertension(Wiley, 2023) Tanriverdi, Lokman Hekim; Ozhan, Onural; Ulu, Ahmet; Yildiz, Azibe; Ates, Burhan; Vardi, Nigar; Acet, Haci AhmetThe MrgD receptor agonist, alamandine (ALA) and Mas receptor agonist, AVE0991 have recently been identified as protective components of the renin-angiotensin system. We evaluated the effects of ALA and AVE0991 on cardiovascular function and remodeling in angiotensin (Ang) II-induced hypertension in rats. Sprague Dawley rats were subject to 4-week subcutaneous infusions of Ang II (80 ng/kg/min) or saline after which they were treated with ALA (50 mu g/kg), AVE0991 (576 mu g/kg), or ALA+AVE0991 during the last 2 weeks. Systolic blood pressure (SBP) and heart rate (HR) values were recorded with tail-cuff plethysmography at 1, 15, and 29 days post-treatment. After euthanization, the heart and thoracic aorta were removed for further analysis and vascular responses. SBP significantly increased in the Ang II group when compared to the control group. Furthermore, Ang II also caused an increase in cardiac and aortic cyclophilin-A (CYP-A), monocyte chemoattractant protein-1 (MCP-1), and cardiomyocyte degeneration but produced a decrease in vascular relaxation. HR, matrix metalloproteinase-2 and -9, NADPH oxidase-4, and lysyl oxidase levels were comparable among groups. ALA, AVE0991, and the drug combination produced antihypertensive effects and alleviated vascular responses. The inflammatory and oxidative stress related to cardiac MCP-1 and CYP-A levels decreased in the Ang II+ALA+AVE0991 group. Vascular but not cardiac angiotensin-converting enzyme-2 levels decreased with Ang II administration but were similar to the Ang II+ALA+AVE0991 group. Our experimental data showed the combination of ALA and AVE0991 was found beneficial in Ang II-induced hypertension in rats by reducing SBP, oxidative stress, inflammation, and improving vascular responses.Öğe ?-Amylase Immobilization on P(HEMA-co-PEGMA) Hydrogels: Preparation, Characterization, and Catalytic Investigation(Wiley-V C H Verlag Gmbh, 2021) Dogan, Demet; Ulu, Ahmet; Sel, Evren; Koytepe, Suleyman; Ates, BurhanThe aims of this study are to synthesize and characterize poly (2-hydroxyethyl methacrylate-co-poly (ethylene glycol) methacrylate) (P(HEMA-co-PEG500MA)) structures containing polyethylene glycol (PEG) side groups and to investigate their possible use in alpha-amylase immobilization. For this purpose, P(HEMA-co-PEG500MA) copolymer structures are synthesized by using different monomer ratios. P(HEMA-co-PEG500MA) copolymer structures are confirmed by Fourier transform infrared spectroscopy (FTIR), and elemental analysis techniques. In addition, thermal, and morphological properties of the copolymers are investigated by thermal gravimetric analysis/differential scanning calorimetry, and scanning electron microscopy (SEM). Afterward, alpha-amylase from Aspergillus oryzae is immobilized on synthesized copolymer support by using physical interactions. The success of immobilization is elucidated via FTIR, SEM, and energy dispersive X-ray spectroscopy (EDX) methods. In addition, the influences of temperature, pH, storage time, and repeated uses on the activity of free and immobilized alpha-amylase are investigated. According to the outcomes, the immobilized alpha-amylase possesses a better pH and thermal resistance than the free one. Additionally, the immobilized alpha-amylase maintains about 53% of its original activity after eight reuses and it exhibits about 50% relative activity after 28 days of storage. In conclusion, the immobilized alpha-amylase can be utilized as a potential efficient catalyst to produce maltose from the hydrolysis of starch.Öğe Biomedical applications of hybrid polymer composite materials(Woodhead Publ Ltd, 2017) Ates, Burhan; Koytepe, Suleyman; Balcioglu, Sevgi; Ulu, Ahmet; Gurses, Canbolat[Abstract Not Available]Öğe The Carboxylated Multi-walled Carbon Nanotubes/l-Asparaginase Doped Calcium-Alginate Beads: Structural and Biocatalytic Characterization(Springer, 2020) Ulu, Ahmet; Karaman, Muhammet; Yapici, Fatma; Naz, Mehmet; Sayin, Selin; Saygili, Eyup Ilker; Ates, BurhanThe calcium-alginate/multi-walled carbon nanotube hybrid beads (Ca-ALG/MWCNT-COOH) as a novel kind of matrix were fabricated and characterized in detailed. l-Asparaginase (l-ASNase), which is important chemotherapeutic enzyme-drug in leukemia, was immobilized on the Ca-ALG/MWCNT-COOH hybrid beads. To the best of our knowledge, this is the first study using Ca-ALG/MWCNT-COOH hybrid beads for l-ASNase immobilization. Our characterization investigations displayed that the hybridization between ALG and MWCNT-COOH caused significant changes on the surface morphology and structure. ALG of 0.5% (w/v), CaCl2 of 0.2 M concentration, enzyme of 187.5 U and bead size of 2 mm was found to be best with respect to enzyme loading efficiency. The enzyme was loaded a high yield (97.0%) on these hybrid beads. Remarkably, the tolerance of immobilized enzyme developed towards temperature and pH changes. The maximum activity for the free enzyme was observed at 35 degrees C, pH 7.5, whereas the immobilized enzyme showed maximum activity at 45 degrees C pH 8.5. After immobilization, storage stability of enzyme improved and retained more than 70% of its initial activity after 4 weeks at ~ 30 degrees C as compared with free enzyme which showed only 20% of residual activity. After immobilization, Km value decreased 1.27-fold compared to free counterpart, indicating increased the affinity between the substrate and enzyme. Moreover, immobilized enzyme maintained more than 36% of its original activity even after consecutive 14 reuse. As result, it is worthy of noting that this kind of hybrid materials may become a promising support material for the immobilization of commercial enzymes in areas such as industrial and medical. GraphicÖğe Carboxymethyl chitosan/inulin composite films incorporated with different phenolic compounds as a potential new material for food packaging applications(Elsevier, 2026) Ulu, Oznur Dogan; Ulu, Ahmet; Birhanli, Emre; Pekdemir, Mustafa Ersin; Ates, BurhanIn this study, three types of biodegradable packaging composite films were developed using a solution casting method for the packaging of food products: Composite films based on carboxymethyl chitosan (CMCS) linked with inulin (INU) and then combined with gallic acid (GA), tannic acid (TA), and naringenin (NAR). The swelling capacity and water vapor permeability of the composite films increased by 3.5-fold compared to the CMCS/INU film, while the moisture content remained almost unchanged. Additionally, the results showed that the incorporation of phenolic compounds significantly improved the UV resistance of composite films, and the UV shielding rate of all composite films reached to 95-99 %. Crucially, the incorporation of phenolic compounds imparted excellent antimicrobial properties as well as remarkable antioxidant activity with over 90 % free radical scavenging rate. While the CMCS/INU film did not show inhibition zone diameter against P. aeruginosa, S. aureus, and C. albicans, the inhibitory zone diameters of the CMCS/INU/TA composite film were found to be 19.75, 22, and 18 mm, respectively. Most importantly, shelf life of green grapes and chicken meat packaged in composite films was effectively extended from 3 days to 12 and 7 days without any decay, respectively. Considering this fact, this study not only provides valuable insights into the development of films with antioxidant and antimicrobial properties but also provides a promising framework for advancing active food packaging technologies.Öğe Chemistry, Structures, and Advanced Applications of Nanocomposites from Biorenewable Resources(Amer Chemical Soc, 2020) Ates, Burhan; Koytepe, Suleyman; Ulu, Ahmet; Gurses, Canbolat; Thakur, Vijay KumarResearchers have recently focused on the advancement of new materials from biorenewable and sustainable sources because of great concerns about the environment, waste accumulation and destruction, and the inevitable depletion of fossil resources. Biorenewable materials have been extensively used as a matrix or reinforcement in many applications. In the development of innovative methods and materials, composites offer important advantages because of their excellent properties such as ease of fabrication, higher mechanical properties, high thermal stability, and many more. Especially, nanocomposites (obtained by using biorenewable sources) have significant advantages when compared to conventional composites. Nanocomposites have been utilized in many applications including food, biomedical, electroanalysis, energy storage, wastewater treatment, automotive, etc. This comprehensive review provides chemistry, structures, advanced applications, and recent developments about nanocomposites obtained from biorenewable sources.Öğe Chitosan/polypropylene glycol hydrogel composite film designed with TiO2 nanoparticles: A promising scaffold of biomedical applications(Elsevier, 2020) Ulu, Ahmet; Birhanli, Emre; Koytepe, Suleyman; Ates, BurhanThe present study explores the preparation and characterization of chitosan/poly (propylene glycol)/titanium dioxide (CH/PPG/TiO2) composite hydrogels in view of their developing applications such as antimicrobial packaging, wound dressing and antibacterial materials. The prepared CH/PPG/TiO2 films were comprehensively characterized by several methods. The size distribution showed the average size of the TiO2 nanoparticles (NPs) was about 40 nm. Additionally, other properties including swelling ratio, water retention, water contact angle, porosity, water uptake, in vitro enzymatic degradation, water vapor transmission rate, in vitro biomineralization studies, and mechanical tests were evaluated in detailed. Besides these characterizations, the antimicrobial activity of CH/PPG/TiO2 composite film against Staphylococcus aureus, Escherichia coli, and Candida lipolytica was evaluated by using disc diffusion method. Based on the obtained results, the CH/PPG/TiO2 composite hydrogels showed enhanced water vapor permeability, porosity, water retention, and swelling ratio. An improvement was observed in the examined mechanical and thermal properties with the addition of TiO2 NPs. The tensile strength and elongation at break values of CH/PPG/TiO2 were 3.0 MPa and 31%, respectively. Most importantly, the CH/PPG/TiO2 composite hydrogels showed strong antimicrobial properties. Finally, the developed composite scaffold prepared in this study may possess potentially useful in biomedical applications. (C) 2020 Elsevier B.V. All rights reserved.Öğe Chitosan/Polyvinylpyrrolidone/MCM-41 Composite Hydrogel Films: Structural, Thermal, Surface, and Antibacterial Properties(Wiley-V C H Verlag Gmbh, 2018) Ulu, Ahmet; Noma, Samir A. A.; Gurses, Canbolat; Koytepe, Suleyman; Ates, BurhanThe aim of this study is to characterize and investigate the effects of the Mobil Composition of Matter No. 41 (MCM-41) concentrations (0.5, 1, 3, 5, and 10 wt%) on structural, thermal, wettability, water content, oxygen (O-2) permeability, and swelling properties as well as morphological characteristics of chitosan/polyvinylpyrrolidone/MCM-41 (CH/PVP/MCM-41) composite hydrogel films. In addition, hydrolytic degradability, optic transmittance, and antibacterial properties of composite hydrogels films are determined as in vitro. With increasing of MCM-41 content, the composite hydrogels showed higher thermal stability, as expected. The morphologic properties of the composite hydrogel films are studied using scanning electron microscope (SEM) technique that provide evidence for good miscibility of CH, PVP, and MCM-41. The swelling and water-absorbing properties of the composite hydrogel films are significantly improved because of enhanced hydrophilic profile. Furthermore, the antimicrobial properties of the prepared composite hydrogel films are studied against Bacillus subtilis, Escherichia coli, and Candida albicans yeast. The results showed excellent antibacterial behavior of the composite hydrogel films. The study clearly demonstrates that the prepared CH/PVP/MCM-41 composite hydrogel films may be used as a promising candidate material in various fields such as drug delivery, wound healing material, and adsorbent materials.Öğe Chloro-Modified Magnetic Fe3O4@MCM-41 Core-Shell Nanoparticles for L-Asparaginase Immobilization with Improved Catalytic Activity, Reusability, and Storage Stability(Springer, 2019) Ulu, Ahmet; Noma, Samir Abbas Ali; Koytepe, Suleyman; Ates, BurhanThis paper describes a new support that permits to efficient immobilization of L-asparaginase (L-ASNase). For this purpose, Fe3O4 magnetic nanoparticles were synthesized and coated by MCM-41. 3-chloropropyltrimethoxysilane (CPTMS) was used as a surface modifying agent for covalent immobilization of L-ASNase on the magnetic nanoparticles. The chemical structure; thermal, morphological, and magnetic properties; chemical composition; and zeta potential value of Fe3O4@MCM-41-Cl were characterized by Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), differential thermal analysis (DTA), differential scanning calorimetry (DSC), vibrating sample magnetometer (VSM), scanning electron microscope (SEM), energy dispersive X-ray (EDX), X-ray diffraction patterns (XRD), and zeta-potential measurement. The immobilization efficiency onto Fe3O4@MCM-41-Cl was detected as 63%. The reusability, storage, pH, and thermal stabilities of the immobilized L-ASNase were investigated and compared to that of soluble one. The immobilized enzyme maintained 42.2% of its original activity after 18cycles of reuse. Furthermore, it was more stable towards pH and temperature compared with soluble enzyme. The Michaelis-Menten kinetic properties of immobilized L-ASNase showed a lower V-max and a similar K-m compared to soluble L-ASNase. Immobilized enzyme had around 47 and 32.5% residual activity upon storage a period of 28days at 4 and 25 degrees C, respectively. In conclusion, the Fe3O4@MCM-41-Cl@L-ASNase core-shell nanoparticles could successfully be used in industrial and medical applications.Öğe Comparative study of ASNase immobilization on tannic acid-modified magnetic Fe3O4/SBA-15 nanoparticles to enhance stability and reusability(Royal Soc Chemistry, 2020) Noma, Samir Abbas Ali; Ulu, Ahmet; Acet, Omur; Sanz, Raul; Sanz-Perez, Eloy S.; Odabasi, Mehmet; Ates, BurhanIn this work, l-asparaginase was immobilized on tannic acid-modified magnetic mesoporous particles. In brief, Fe3O4/SBA-15/tannic acid magnetic particles were synthesized, and their structures and morphologies were fully characterized using various methods. The properties of the free and immobilized enzyme were examined in terms of pH, temperature, thermal stability, storage stability, and reusability. Moreover, the effects of metal ions, inhibitors and organic solvents on the activity of the immobilized enzyme were investigated. Compared to the free enzyme, the immobilized enzyme possessed better tolerance to changes in ambient temperature and pH. Additionally, thermal incubation results showed that the free enzyme lost its activity, while the immobilized enzyme exhibited the opposite behavior. Most strikingly, the immobilized l-asparaginase exhibited a high degree of activity (70%) after being reused 16 times while also demonstrating 71% and 63% storage stability of the initial activity even after 28 days at 4 degrees C and room temperature, respectively. Together with these results, l-asparaginase was successfully immobilized upon Fe3O4/SBA-15/tannic acid magnetic nanoparticles with improved stability properties. This support holds great potential and opens up a novel perspective for growing applications.Öğe Comparative study of catalase immobilization via adsorption on P(MMA-co-PEG500MA) structures as an effective polymer support(Springer, 2021) Sel, Evren; Ulu, Ahmet; Ates, Burhan; Koytepe, SuleymanIn this study, poly[methyl methacrylate-co-poly(ethylene glycol) methacrylate] (P(MMA-co-PEG500MA)) copolymers were used for catalase (CAT) immobilization. Firstly, P(MMA-co-PEG500MA) copolymers were synthesized by using different amount of methyl methacrylate (MMA) and poly(ethylene glycol) methacrylate (PEG500MA) monomers. The synthesized copolymers were characterized by different analysis techniques. Afterward, CAT enzyme was immobilized via physical adsorption method onto the P(MMA-co-PEG500MA) copolymers. P3 sample containing 1:1 (PEG500MA:MMA) monomer molar ratio was selected as model support because of exhibiting optimum surface porosity and thermal stability. A high immobilization yield (76%) was achieved under optimized conditions. The immobilized enzyme displayed improved tolerance towards pH and temperature changes. After immobilization, the optimum pH shifted from 7.5 to 7.0, whereas the optimum temperature remained unchanged at 35 degrees C. Immobilized enzyme showed good reuse potential and excellent storage stability. After 10 consecutive uses, immobilized enzyme maintained about 51.0% of its initial activity. Furthermore, free enzyme completely lost its initial activity after 4 weeks, while immobilized enzyme maintained approximately 65% of the initial activity at 25 degrees C. Approximately twofold decrease in Km was obtained which means that the affinity of enzyme to the substrate improved after immobilization. Finally, it can be concluded that the prepared P(MMA-co-PEG500MA) copolymer structure can be an ideal matrix for CAT immobilization.Öğe Comparison of cilomilast, tadalafil, and both drug combinations in the treatment of monocrotaline-induced pulmonary arterial hypertension in rats(Bmc, 2025) Ermis, Necip; Ozhan, Onural; Yildiz, Azibe; Ulutas, Zeynep; Parlakpinar, Hakan; Ulu, Ahmet; Ates, BurhanBackground Pulmonary arterial hypertension (PAH) is a progressive disease characterized by endothelial dysfunction and inflammation. This study aimed to evaluate the effects of cilomilast (CIL), a phosphodiesterase-4 inhibitor, and tadalafil (TAD), a phosphodiesterase-5 inhibitor, on PAH induced by monocrotaline (MCT) in rats. Methods Forty Wistar albino rats were divided into five groups: control, MCT, MCT + CIL, MCT + TAD, and MCT + CIL + TAD. PAH was induced via MCT, and treatments were administered orally from days 21 to 35. Hemodynamic parameters, right ventricular pressure (RVP), echocardiographic findings, and histopathological lung and heart tissue changes were assessed. Nitric oxide (NO) levels in lung tissue were also measured. Results Tissue NO levels were significantly greater in the MCT + CIL + TAD group than in the MCT group (p = 0.01). The RVP was lower in the MCT + TAD and MCT + CIL + TAD groups than in the MCT group (p < 0.05) but not in the MCT + CIL group. Histopathologically, lung perivascular infiltration and pulmonary artery wall thickness were significantly reduced in the MCT + CIL + TAD group, indicating an anti-inflammatory effect. However, CIL alone did not significantly impact pulmonary artery thickening or RVP. Conclusion CIL alone had no significant effect on PAH progression, but its combination with TAD improved inflammation scores and NO levels. These findings suggest that targeting inflammation alongside vasodilation may offer therapeutic benefits in PAH. Further studies with different doses and PAH models are recommended.Öğe The Cytotoxicity, DNA Fragmentation, and Decreasing Velocity Induced By Chromium(III) Oxide on Rainbow Trout Spermatozoa(Springernature, 2023) Ozgur, Mustafa Erkan; Ulu, Ahmet; Gurses, Canbolat; Ozcan, Imren; Noma, Samir Abbas Ali; Koytepe, Suleyman; Ates, BurhanThe present study aimed to determine the cytotoxicity of chromium(III) oxide micro particles (Cr2O3-Ps) in rainbow trout (Oncorhynchus mykiss) spermatozoa. Firstly, Cr2O3-Ps were synthesized and structurally characterized the surface, morphological for particle size and thermal properties. In addition, its structural and elemental purity was determined using energy-dispersive X-ray (EDX) spectrum and elemental maps. Structural purity, thermal properties, and stability of Cr2O3 -Ps were also examined in detail by performing thermal analysis techniques. The cytotoxicity of Cr2O3-Ps was measured by the observation of velocities, antioxidant activities, and DNA damages in rainbow trout spermatozoa after exposure during 3 h in vitro incubation. The straight line velocity (VSL), the curvilinear velocity (VCL), and the angular path velocity (VAP) of spermatozoa decreased after exposure to Cr2O3-Ps. While the superoxide dismutase (SOD) and the catalase (CAT) decreased, the lipid peroxidation increased in a dose-dependent manner. However, the total glutathione (tGSH) was not affected in this period. DNA damages were also determined in spermatozoa using Comet assay. According to DNA in tail (%) data, DNA damages have been detected with gradually increasing concentrations of Cr2O3-Ps. Furthermore, all of class types which are categorized as the intensity of DNA fragmentation has been observed between 50 and 500 mu g/L concentrations of Cr2O3-Ps exposed to rainbow trout spermatozoa. At the end of this study, we determined that the effective concentrations (EC50) were 76.67 mu g/L for VSL and 87.77 mu g/L for VCL. Finally, these results about Cr2O3-Ps may say to be major risk concentrations over 70 mu g/L for fish reproduction in aquatic environments.Öğe Design of epoxy-functionalized Fe3O4@MCM-41 core-shell nanoparticles for enzyme immobilization(Elsevier, 2018) Ulu, Ahmet; Ozcan, Imren; Koytepe, Suleyman; Ates, BurhanThe scope of our research was to prepare the organosilane-modified Fe3O4@MCM-41 core-shell magnetic nano particles, used for L-ASNase immobilization and explored screening of immobilization conditions such as pH, temperature, thermal stability, kinetic parameters, reusability and storage stability. In this content, Fe3O4 core shell magnetic nanoparticles were prepared via co-precipitation method and coated with MCM-41. Then, Fe3O4@MCM-41 magnetic nanoparticles were functionalized by (3-glycidyloxypropyl) trimethoxysilane (GPTMS) as an organosilane compound. Subsequently, L-ASNase was covalently immobilized on epoxyfunctionalized Fe3O4@MCM-41 magnetic nanoparticles. The immobilized L-ASNase had greater activity at high pH and temperature values. It also maintained >92% of the initial activity after incubation at 55 degrees C for 3 h. Regarding kinetic values, immobilized L-ASNase showed a higher Vmax and lower Km compared to native L-ASNase. In addition, it displayed excellent reusability for 12 successive cycles. After 30 days of storage at 4 degrees C and 25 degrees C, immobilized L-ASNase retained 54% and 26% of its initial activities while native L-ASNase lost about 68% and 84% of its initial activity, respectively. As a result, the immobilization of L-ASNase onto magnetic nanoparticles may provide an advantage in terms of removal of L-ASNase from reaction media. (C) 2018 Elsevier B.V. All rights reserved.Öğe Design of highly selective, and sensitive screen-printed electrochemical sensor for detection of uric acid with uricase immobilized polycaprolactone/polyethylene imine electrospun nanofiber(Pergamon-Elsevier Science Ltd, 2023) Muhammad, Fakhriy; Dik, Gamze; Kolak, Seda; Gedik, Kubra Karadas; Bakar, Busra; Ulu, Ahmet; Ates, BurhanUric acid (UA) plays a significant role in nerve center, human metabolism, and kidney system. Therefore, it is necessary to establish a simple, rapid, and sensitive detection method for UA. In recent years, researchers have been highly attracted by nanomaterials with satisfactory functions in electrochemical applications. In this study, polycaprolactone (PCL)/polyethylene imine (PEI) nanofiber membranes were prepared and used for the immobilization of uricase (UOx). The prepared membranes were characterized in terms of structure, composi-tion, and morphology. Afterward, the quantum dot screen printed electrode (QD SPCE) was modified with PCL/ PEI nanofiber membranes with and without methylene blue (MB) as an electron mediator. The electrochemical performance of the developed sensors was investigated by cyclic voltammetry (CV), differential pulse voltam-metry (DPV), and electrochemical impedance spectroscopy (EIS). Under the optimal conditions, the modified sensors provided a broad linear range (5.0-52.0 mu M) for the electrochemical detection of UA. Limit of detection (LoD) values were determined as 3.96 mu M and 1.85 mu M for the PCL/PEI/UOx/QD SPCE and PCL/PEI/UOx/MB/ QD SPCE, respectively. The four-week stability results showed the change in current for the PCL/PEI/UOx/QD SPCE and PCL/PEI/UOx/MB/QD SPCE to be 92% and 87%, respectively. Additionally, in the mixed interference test remaining current ratios for UA were 95% and 82% for the PCL/PEI/UOx/QD SPCE and PCL/PEI/UOx/MB/ QD SPCE, respectively. Most importantly, the effectiveness of the electrodes was also verified in real sample detection with satisfactory recovery (similar to 98-112%). Overall, the results showed that the PCL/PEI/UOx/QD SPCE and PCL/PEI/UOx/MB/QD SPCE have the advantages of simplicity, high sensitivity, and good selectivity for UA determination.Öğe Design of laccase-metal-organic framework hybrid constructs for biocatalytic removal of textile dyes(Pergamon-Elsevier Science Ltd, 2022) Birhanli, Emre; Noma, Samir Abbas Ali; Boran, Filiz; Ulu, Ahmet; Yesilada, Ozfer; Ates, BurhanThis study aims to present a simple and effective carrier matrix to immobilize laccase as opposed to complex and tedious immobilization processes and also to use it in the removal of textile dyes. For this purpose, Cobalt (Co) and Copper (Cu) based metal-organic frameworks (MOFs) were prepared and laccase was immobilized on two different MOFs via encapsulation. The characterization outcomes showed that laccase was well immobilized into MOF supports. Optimum pH and temperature were found for Lac/Co-MOF (pH 4.5 at 50 degrees C) and Lac/Cu-MOF (pH 5.0 at 50 degrees C). The Km (0.03 mM) and Vmax (97.4 mu mol/min) values of Lac/Cu-MOF were lower than those of Lac/Co-MOF (Km = 0.13 mM, Vmax = 230.7 mu mol/min). The immobilized laccases showed good reusability as well as improved resistance to temperature denaturation and high storage stability. For instance, the Lac/Co-MOF and Lac/Cu-MOF retained more than 58% activity after 4 weeks of storage at room temperature. Meanwhile, Lac/Co-MOF and Lac/Cu-MOF maintained 56.5% and 55.8% of their initial activity, respectively, after 12 reuse cycles. Moreover, thermal deactivation kinetic studies of immobilized laccases displayed lower k value, higher t1/2, and enhancement of thermodynamic parameters, which means better thermostability. Finally, the decolorization activities for the Lac/Co-MOF were 78% and 61% at the 5th cycle for Reactive Blue 171 andÖğe Design of near-infrared light induced functionalized upconverting nanoparticles as support in enzyme immobilization: Enhanced biocatalyst activity and stability(Elsevier, 2025) Ulu, Ahmet; Noma, Samir Abbas Ali; Kurucay, Ali; Topel, Seda Demirel; Asilturk, Meltem; Ates, BurhanIn this study, we hypothesized that the emission of upconverted nanoparticles (UCNP) can trigger PEG-L-ASNase (P-Lase) activity through Forster Resonance Energy Transfer under near-infrared (NIR) irradiation. To enhance stability and activity of P-Lase, it was immobilized on functionalized NaYF4:Yb3+, Er3+, Nd3+. Upon immobilization, the obtained NaYF4:Yb3+, Er3+, Nd3+/GPTMS-P-Lase exhibited excellent pH stability, thermal stability, metal ions or organic solvent tolerance, and storage stability. The relative activity of NaYF4:Yb3+, Er3+, Nd3+/ GPTMS-P-Lase had about 65 % after 20 cycles and maintained 68 % and 59 % at +4 and 25 degrees C, respectively, after 4 weeks. Furthermore, in vitro cytotoxicity and hemolysis tests confirmed that the synthesized UCNPs were biocompatible. Most importantly, the activity of P-Lase was enhanced >= 4-fold under suitable NIR irradiation. It is reasonable to believe that this investigation may supply a novel technique to trigger the catalytic efficiency of P-Lase and may have promising application in leukemia treatment.Öğe Design of starch functionalized biodegradable P(MAA-co-MMA) as carrier matrix for L-asparaginase immobilization(Elsevier Sci Ltd, 2016) Ulu, Ahmet; Koytepe, Suleyman; Ates, BurhanWe prepared biodegradable P(MAA-co-MMA)-starch composite as carrier matrix for the immobilization of L-asparaginase (L-ASNase), an important chemotherapeutic agent in acute lymphoblastic leukemia. Chemical characteristics and thermal stability of the prepared composites were determined by FT-IR, TGA, DTA and, DSC, respectively. Also, biodegradability measurements of P(MAA-co-MMA)-starch composites were carried out to examine the effects of degradation of the starch. Then, L-ASNase was immobilized on the P(MAA-co-MMA)-starch composites. The surface morphology of the composite before and after immobilization was characterized by SEM, EDX, and AFM. The properties of the immobilized L-ASNase were investigated and compared with the free enzyme. The immobilized L-ASNase had better showed thermal and pH stability, and remained stable after 30 days of storage at 25 degrees C. Thus, based on the findings of the present work, the P(MAA-co-MMA)-starch composite can be exploited as the biocompatible matrix used for L-ASNase immobilization for medical applications due to biocompatibility and biodegradability. (C) 2016 Elsevier Ltd. All rights reserved.Öğe Development of L-asparaginase@hybrid Nanoflowers (ASNase@HNFs) Reactor System with Enhanced Enzymatic Reusability and Stability(Springer, 2021) Noma, Samir Abbas Ali; Yilmaz, Burcu Somturk; Ulu, Ahmet; Ozdemir, Nalan; Ates, BurhanHybrid nanoflowers materials have recently received great attention in enzyme immobilization applications because of the advantages such as their large surface area, excellent stability, simple, eco-friendly, and cost-effective synthesis. In this study, l-asparaginase which is an important commercial enzyme in the medicine and food industry was selected as a model enzyme. To the best of our knowledge, this study is the first report of designing L-asparaginase@hybrid nanoflowers to enhance its enzymatic performance. L-asparaginase@hybrid nanoflowers were synthesized using ASNase as an organic component and Cu(II) ion as inorganic component. They were characterized by their morphology and chemical point of view by using different techniques. The synthesized L-asparaginase@hybrid nanoflowers exhibited high residual activity at broad pH and high temperature ranges in comparison to free form. Moreover, L-asparaginase@hybrid nanoflowers possessed good reusability and excellent long-time storage stability. Especially, L-asparaginase@hybrid nanoflowers-3 maintained nearly 51 and 75% of its original activity, respectively, after nine consecutive catalytic cycles and storage at 30 degrees C for 4 weeks. The results indicated that these hybrid nanoflowers will be promising carrier matrix for the immobilization of ASNase in biotechnological applications with improved catalytic properties. [GRAPHICS] .Öğe Eco-friendly chitosan/?-carrageenan membranes reinforced with activated bentonite for adsorption of methylene blue(Elsevier Science Sa, 2022) Ulu, Ahmet; Alpaslan, Musa; Gultek, Ahmet; Ates, BurhanIn this work, the chitosan/kappa-carrageenan/acid-activated bentonite composite membranes were prepared through blending method and used to adsorb methylene blue dye. The prepared composite membranes were characterized with several spectroscopic and microscopic techniques. The results revealed that the bentonite was homogeneously distributed in the membrane matrix, which means extensive porous structure was formed on the surface. The effects of initial concentration of methylene blue, adsorbent dosage, pH value, contact time, ionic strength, and temperature on methylene blue removal percentage the prepared membrane was investigated in detail. Adsorption kinetics and equilibrium adsorption isotherm fitted pseudo-second-order kinetic model and Freundlich isotherm model well, respectively. The thermodynamics analysis suggested that the adsorption process of methylene blue onto the chitosan/kappa-carrageenan/acid-activated bentonite composite membrane was spontaneous and endothermic. The highest removal rate (98%) was achieved under the following conditions: adsorbent dose, 0.05 g; solution pH, 4; temperature, 50 degrees C; and time, 200 min. The maximum adsorption capacity for methylene blue was 18.80 mg/g at 50 degrees C. Moreover, the prepared composite membrane demonstrated the high reusability and adsorption rate (similar to 77%) without significant loss after sixth adsorption-desorption cycles. Considering of the above results, the prepared composite membrane can be a promising adsorbent candidate having low cost and high recyclability to remove methylene blue.
