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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 Enhancement of enzyme activity by laser-induced energy propulsion of upconverting nanoparticles under near-infrared light: A comprehensive methodology for in vitro and in vivo applications(Elsevier, 2024) Ates, Burhan; Ulu, Ahmet; Asilturk, Meltem; Noma, Samir Abbas Ali; Topel, Seda Demirel; Dik, Gamze; Ozhan, OnuralIf the appropriate immobilization method and carrier support are not selected, partial decreases in the activity of enzymes may occur after immobilization. Herein, to overcome this challenge, an excitation mechanism that enables energy transfer was proposed. Modified upconverting nanoparticles (UCNPs) were constructed and the important role of near-infrared (NIR) excitation in enhancing the catalytic activity of the enzyme was demonstrated. For this purpose, UCNPs were first synthesized via the hydrothermal method, functionalized with isocyanate groups, and then, PEG-L-ASNase was immobilized via covalent binding. UCNPs with and without PEG-LASNase were extensively characterized by different methods. These supports had immobilization yield and activity efficiency of >96 % and 78 %, respectively. Moreover, immobilized enzymes exhibited improved pH, thermal, and storage stability. In addition, they retained >65 % of their initial activity even after 20 catalytic cycles. Biochemical and histological findings did not indicate a trend of toxicity in rats due to UCNPs. Most importantly, PEG-L-ASNase activity was triggered approximately 5- and 2-fold under in vitro and in vivo conditions, respectively. Overall, it is anticipated that this pioneering work will shed new light on the realistic and promising usage of NIR-excited UCNPs for the immobilization of enzymes in expensive and extensive applications.Öğe Immobilization of ?-Amylase onto Quantum Dots Prepared from Hypericum perforatum L. Flowers and Hypericum capitatum Seeds: Its Physicochemical and Biochemical Characterization(Springer/Plenum Publishers, 2023) Acari, Idil Karaca; Dik, Gamze; Bakar, Busra; Ulu, Ahmet; Onal, Yunus; Ates, BurhanEnzyme immobilization is an effective way to increase the catalytic activity and stability of the alpha-amylase (Amy) enzyme for industrial uses. For this purpose, carbon and graphene quantum dot (QDs) structures were prepared from Hypericum perforatum L. flowers (QD-1), and Hypericum capitatum seeds (QD-2) obtained from an herbalist in Hatay province of Turkey. Structural and morphological characterization of the prepared QDs and QDs/Amy were carried out by Fourier transform infrared spectrophotometer (FTIR), X-ray diffraction (XRD), scanning electron microscope (SEM), and energy dispersive X-ray (EDX). Meanwhile, biochemical characterizations such as optimum pH and temperature, kinetic parameters, effects of metal ions, organic solvents, and trypsin digestion on enzyme activity were performed and compared with free Amy. The Amy enzyme was immobilized with an activity efficiency of 71.15% for QD-1/Amy, and 81.51% for QD-2/Amy under optimal conditions. The difference in activity efficiency between QD-1/Amy and QD-2/Amy was likely due to a change in the surface porosity of QDs structures. While the optimal pH value of all three forms of Amy was recorded as 6.0, their optimal temperature was found to be 40 degrees C. The activation energy (E-a) of the free Amy was found to be 4.81 kJ/mol, while it was 9.61 kJ/mol, and 3.20 kJ/mol for QD-1/Amy, and QD-2/Amy, respectively. K-m values were calculated as 1.18, 1.57, and 1.35 mg/mL for free Amy, QD-1/Amy, and QD-2/Amy, respectively, and V-max values were calculated as 37.52, 37.60, and 39.93 mu mol/min, respectively. Kinetic data revealed that the immobilized enzymes had lower substrate affinity compared to the free Amy. Besides, the QD-1/Amy and QD-2/Amy exhibited more stability than free Amy against metal ions, organic solvents as well as trypsin digestion due to the increment in conformational rigidity caused by changes in the secondary structures of the immobilized enzyme. For instance, after incubation with trypsin for 120 min, free Amy, QD-1/Amy, and QD-2/Amy retained approximately 20%, 35%, and 26% of initial activities, respectively. Finally, it can be proposed that the prepared carriers in this work may a useful to produce stable and active immobilized Amy to be used in industrial applications.Öğe Immobilization of Xylanase into Zeolitic Imidazolate Framework-67 (ZIF-67) and Manganese-Doped ZIF-67 (Mn/ZIF-67): A Comparison Study(Springer/Plenum Publishers, 2024) Bakar, Busra; Dik, Gamze; Ulu, Ahmet; Ates, BurhanIt has been discovered that metal-organic frameworks (MOFs) have desirable qualities for the immobilization of enzymes, including a high surface area, significant interior pore volumes, and easily changeable pore size. Herein, the xylanase (Xyl) enzyme was immobilized for the first time to two different carrier supports, zeolitic imidazolate framework-67 (ZIF-67) and manganese-doped ZIF-67 (Mn/ZIF-67) by in situ method. The physicochemical characterizations of MOFs with and without Xyl were performed by FT-IR, XRD, SEM, and EDAX techniques. Xyl@ZIF-67 and Xyl@Mn/ZIF-67 were evaluated in terms of optimum temperature, optimum pH, kinetic parameters, thermal stability, reusability as well as juice clarification and compared with free Xyl. Optimum temperature values were 50 degrees C for Xyl@ZIF-67 and 70 degrees C for free Xyl and Xyl@Mn/ZIF-67. Optimum pH values for free Xyl, Xyl@ZIF-67, and Xyl@Mn/ZIF-67 were recorded as 6.0, 8.0, and 7.0, respectively. Km values for free Xyl, Xyl@ZIF-67, and Xyl@Mn/ZIF-67 were calculated as 3.139, 5.430, and 0.799 mg/mL, respectively, while Vmax values were calculated as 0.167, 0.226, and 0.062 mu mol/min/mL, respectively. The results revealed that in comparison to the free Xyl, Xyl@ZIF-67, and Xyl@Mn/ZIF-67 exhibited more thermal resistance. After incubation at 70 degrees C for 120 min, the free Xyl remained at 28.7% of the activity, while the Xyl@ZIF-67 and Xyl@Mn/ZIF-67 remained at 85.7% and 40.0%, respectively. Moreover, after eight cycles, the Xyl@ZIF-67 and Xyl@Mn/ZIF-67 retained more than 70% of their initial activity. Further, the transmittance of apple juice was increased from 65.61 to 94.73% and from 77.80 to 84.13%, respectively, when Xyl@ZIF-67 and Xyl@Mn/ZIF-67 were used as biocatalysts. Overall, these findings indicated that the suggested Xyl@ZIF-67 and Xyl@Mn/ZIF-67 have a high potential for juice clarification as an efficient heterogeneous biocatalyst.Öğe Immobilization of Xylanase onto Starch Nanoparticles: A Reusable and Robust Nanobiocatalyst for Juice Clarification(Wiley-V C H Verlag Gmbh, 2023) Dik, Gamze; Bakar, Busra; Ulu, Ahmet; Koytepe, Sueleyman; Ates, BurhanNanoparticles (NPs) have attracted interest recently as a promising support for the immobilization of enzymes.Xylanase (Xyl) has been utilized in the food industry for several purposes. To improve its stability and reusability,starch NPs (SNPs)are synthesized and assessed for Xyl immobilization for the first time. . The characterization results reveal that SNPs are successfully synthesized and Xyl@SNPs are effective as the immobilization carrier. The Xyl is immobilized on SNPs under optimized conditions leading to 91% immobilization efficiency. A shift in optimum pH (from 6.0 to 8.0) and temperature (from 70 to 60 degrees C) of Xyl is observed after immobilization. The Xyl@SNPs possess improve pH stability and thermal stability as well as operational stability. The Xyl@SNPs are easily reutilized and the residual activity is still higher than 62% after seven times. More importantly, the Xyl@SNPs have a lower Km value and enhance affinity for the substrate compared to the free Xyl. Additionally, the clarity of orange juice is increased by 76.0% by using Xyl@SNPs after 2 h incubation at 60 degrees C, pH 8.0. These positive results show promising support for the Xyl immobilization of SNPs, confirming that this immobilized enzyme-based strategy is an effective technique for rapid clarification of targeted juices.Öğe Manyetik Kantilever ile IgG Antikorlarının Tespiti(2023) İnan, Orhan Orçin; Dik, Gamze; Ulu, Ahmet; Ateş, Burhan; Atalay, SelçukBu çalışmada, IgG antikorlarını algılamak için kantilever olarak $Fe_{40}Ni_{38}Mo_{4}B_{18}$ amorf ferromanyetik şerit kullanılmıştır. Sensör yüzeyi IgG algılaması için fonksiyonel hale getirilmiş ve daha sonra yapılan ölçümlerde ppm ya da ng mertebesinde IgG algılaması yapılmıştır.Öğe Near-infrared inducible supports in bio-catalysts design: A useful and versatile tool in enhancement of enzyme activity(Elsevier, 2024) Noma, Samir Abbas Ali; Dik, Gamze; Gurses, Canbolat; Kurucay, Ali; Topel, Seda Demirel; Ulu, Ahmet; Asiltuerk, MeltemImmobilized enzymes have encountered two main challenges: Reduced enzyme activity compared to free enzymes and exhausted immobilized enzymes due to reusability. Herein, we suggested a promising activity enhancement strategy to overcome these challenges. The emission from upconversion nanoparticles (UCNPs) under near-infrared (NIR) excitation can increase the activity of PEG-L-ASNase due to Forster Resonance Energy Transfer. For this purpose, UCNPs were initially synthesized using the hydrothermal method. Subsequently, these UCNPs were functionalized with a polycationic polymer, branched polyethyleneimine (PEI), and the immobilization of PEG-L-ASNase was achieved through adsorption. We preliminarily explored the parameters such as enzyme concentration, incubation time, pH, temperature, reusability, storage stability, and kinetic study, etc. Further, the in vitro biocompatibility, hemolytic behavior, and anticancer activity of the produced UCNPs were also analyzed as crucial parameters. The results showed the pH durance, thermal and storage stability of the immobilized PEG-L-ASNases were enhanced. The immobilized PEG-L-ASNases maintained their activity to >= 55 % after 20 cycles. Enzyme immobilization led to a decrease in Km and Vmax compared to PEG-L-ASNase. In vitro assays revealed that immobilized enzyme further reduced the proliferation of human leukemia cell line (HL-60) upon NIR irradiation exposure but did not cause toxicity. This research may provide a new strategy to promote the catalytic activity of L-ASNase and demonstrates its potential application on human leukemia cells. Finally, these outcomes are valuable for the use of NIR induction in enzymatic reactions.Öğe Newly Synthesized Multifunctional Biopolymer Coated Magnetic Core/Shell Fe3O4@Au Nanoparticles for Evaluation of L-asparaginase Immobilization(Springer/Plenum Publishers, 2023) Tarhan, Tuba; Dik, Gamze; Ulu, Ahmet; Tural, Bilsen; Tural, Servet; Ates, BurhanThe immobilization strategy can promote greater enzyme utilization in applications by improving the overall stability and reusability of the enzyme. In this work, the L-asparaginase (L-ASNase) obtained from Escherichia coli was chosen as a model enzyme and immobilized onto the Fe3O4@Au-carboxymethyl chitosan (CMC) magnetic nanoparticles (MNPs) through adsorption. TEM, SEM, FT-IR, XRD, EDS, and TGA analyses were performed to examine the structure with and without L-ASNase. The yield of immobilized L-ASNase on Fe3O4@Au-CMC was found to be 68%. The biochemical properties such as optimum pH, optimum temperature, reusability, and thermal stability of the Fe3O4@Au-CMC/L-ASNase were comprehensively investigated. For instance, Fe3O4@Au-CMC/L-ASNase reached maximum activity at pH 7.0 and the optimum temperature was found to be 50 degrees C. The noticeably lower Ea value of the Fe3O4@Au-CMC/L-ASNase revealed the enhanced catalytic activity of this enzyme after immobilization. The Km and Vmax values were 3.27 +/- 0.48 mM, and 51.54 +/- 0.51 mu mol min(-1) for Fe3O4@Au-CMC/L-ASNase, respectively, which means good substrate affinity. The Fe3O4@Au-CMC/L-ASNase retained 65% of its initial activity even after 90 min at 60 degrees C. Moreover, it maintained more than 75% of its original activity after 10 cycles, indicating its excellent reusability. The results obtained suggested that this investigation highlights the use of MNPs as a support for the development of more economical and sustainable immobilized enzyme systems.Öğe A Positive Effect of Magnetic Field on the Catalytic Activity of Immobilized L-Asparaginase: Evaluation of its Feasibility(Springer, 2023) Dik, Gamze; Ulu, Ahmet; Inan, Orhan Orcun; Atalay, Selcuk; Ates, BurhanEnzyme immobilization is an attractive strategy to improve enzyme stability, however, the activity significantly reduces after immobilization. To solve this issue, we designed a novel magnetic carrier that both enhanced enzyme activity and improved its stability. For this purpose, the magnetic nanoparticles were synthesized and L-asparaginase was immobilized physically. All materials were structurally and morphologically characterized. Besides, the biochemical properties of the immobilized enzyme were investigated and compared with the free one. Moreover, the activity of the immobilized enzyme was investigated under a weak magnetic field. The optimum pH and optimum temperature of the free and immobilized enzyme were found to be 8.5 and 45 degrees C, 7.5 and 40 degrees C, respectively. Moreover, even after 10 cycles of use, the immobilized enzyme retained 54% of its initial activity. K-m for free and the immobilized enzyme was found to be 10.37 +/- 0.5, and 7.06 +/- 2.99 mM, respectively, and V-max was found to be 138.88 +/- 2.64, and 121.95 +/- 1.07 molimin, respectively. Most importantly, the activity increased approximately 3.2-fold and 4.3-fold at 10 Hz and 20 mT, respectively. Overall, the results suggested that, if the activity of the immobilized enzyme is very low, applying a weak magnetic field may be necessary to enhance the enzyme reaction. [GRAPHICS] .Öğe Preparation, characterization of upconverting nanoparticles for uricase immobilization and controlled manipulation of uricase activity by near-infrared light(Elsevier, 2024) Dik, Gamze; Noma, Samir Abbas Ali; Ulu, Ahmet; Topel, Seda Demirel; Asiltuerk, Meltem; Ates, BurhanIn recent years, studies on the external stimulation of biotechnological enzyme drugs and their use in the treatment of diseases have gradually increased. Herein, for the first time, the near-infrared (NIR) was used as an external stimulant to manipulate the catalytic activity of the uricase (UOx) enzyme, which is used in the treatment of hyperuricemia, in a controlled manner. For this purpose, NaYF4: Yb3+, Er3+ upconverting nanoparticles (UCNPs) were synthesized by hydrothermal synthesis method and functionalized with diethylaminoethyldextran (DEAE-D) to facilitate UOx immobilization. The obtained materials were characterized in detail by various methods to confirm the preparation of UCNPs and immobilization of UOx. In addition, the biochemical parameters such as optimum pH, optimum temperature, thermal stability, and reusability were preliminarily investigated for free UOx and NaYF4: Yb3+, Er3+/DEAE-D/UOx. Moreover, a sequential experimental method was monitored to assess the effects of NIR excitation intensity, induction distance, and exposure time on the UOx activity. While the optimum pH value was found to be 6.0 for both enzyme forms, the optimum temperature value was recorded as 45 and 50 degrees C for free UOx and NaYF4: Yb3+, Er3+/DEAE-D/UOx, respectively. The activation energy (Ea) values of free UOx and NaYF4: Yb3+, Er3+/DEAE-D/UOx were calculated to be 7.59 and 2.98 kJ/mol, respectively, implying that the NaYF4: Yb3+, Er3+/DEAE-D/UOx was less temperature sensitive. After thermal incubation for 3 h at 55 degrees C, the NaYF4: Yb3+, Er3+/DEAE-D/UOx retained 54.68 % of its initial activity, while the free UOx retained 32.94 % of its initial activity at 50 degrees C. In addition, the findings from the reusability experiments revealed that NaYF4:Yb3+, Er3+/DEAE-D/UOx retained 57.94 % of its initial activity even after 10 reuse cycles. The most striking point in this study was the positive manipulation of UOx activity by NIR. Accordingly, it was observed that when the NIR power was 1500 mW, the UOx activity increased about 2 times compared to the control. Additionally, the UOx activity increased in parallel with the increase in NIR application time and the ideal application distance was 3 cm. In conclusion, this pioneering study provides valuable insights into the controlled manipulation of enzyme activity, showcasing the effectiveness of NIR in enhancing enzyme activity. The outcomes suggest that NIR holds great promise as an efficient, sustainable, and versatile approach applicable to various enzymatic catalysis scenarios.Öğe Propelling of Enzyme Activity by Using Different Triggering Strategies: Applications and Perspectives(Amer Chemical Soc, 2023) Dik, Gamze; Bakar, Busra; Ulu, Ahmet; Ates, BurhanEnzymes have been widely used as biocatalysts to meet the increasing demand for industrial approaches. Even if the method of immobilization used to stabilize enzymes seems easy and effective for scientists, the maintenance of activity remains currently an open challenge in various applications. Activity enhancement has recently gained a huge interest since this is a significant point in terms of industrial applications. In this context, external stimulants such as ultrasound, magnetic field, electric field, and light irradiation affect the activity of an enzyme in different aspects. Among these, ultrasound induction exhibits a prominent role in the enhancement of the activity of the immobilized enzyme. On the other hand, although a large number of articles have reported improvements in the catalytic activities of enzymes by induction methods, to the best of our knowledge, a review describing these improvements in the catalytic activities of enzymes has not yet been reported. Therefore, this novel review focused on the effects of the different induction methods, and it will provide novel perspectives and recent information for the development and application of related research areas. In addition, it will give an insight into the mechanisms at the molecular level in response to the question of how the induction methods enhance enzyme activity.Öğe Synthesis and Biomedical Applications of Polymer-Functionalized Magnetic Nanoparticles(Eurasia Acad Publ Group (Eapg), 2023) Dik, Gamze; Ulu, Ahmet; Ates, BurhanMagnetic nanoparticles (MNPs) are receiving increasing attention from individual scientists and research companies as promising materials for biomedical applications. MNPs can be synthesized by many different methods. Before proceeding to the synthesis process, the cost of using it and the practicality of the synthesis conditions are well investigated. Especially in their use in the biomedical field, features such as not containing toxic substances, high biocompatibility, and low particle size are desired. However, the use of magnetic nanoparticles in biomedical applications is limited due to various difficulties such as particle agglomeration and oxidation of magnetic cores of MNPs. To overcome these challenges, MNPs can be coated with various natural and synthetic polymers to alter their morphological structure, magnetic character, biocompatibility, and especially surface functional groups. Therefore, this chapter focuses on the synthesis of MNPs by different methods, the effects of these synthesis methods on magnetic properties and size, their modifications with natural and synthetic polymers, and the use of these polymer-coated MNPs in biomedical fields such as targeted drug release, enzyme immobilization, biosensors, tissue engineering, magnetic imaging, and hyperthermia. The review article also provides examples of advanced biomedical applications of polymer-coated MNPs and perspectives for future research to promote polymer-coated MNPs. To this end, we aim to highlight knowledge gaps that can guide future research to improve the performance of MNPs for different applications.
