Browsing by Author "Ocsoy, Ismail"

Now showing 1 - 7 of 7

Horseradish peroxidase (HRP) nanoflowers-mediated polymerization of vinyl monomers
(SPRINGER NATURE LINK, 2024) Ozaydin, Gulbahar; Mirioglu, Muge; Kaplan, Naime; Dadi, Seyma; Ocsoy, Ismail; Gokturk, Ersen; 0000-0001-6280-3966; AGÜ, Mühendislik Fakültesi, Malzeme Bilimi ve Nanoteknoloji Mühendisliği Bölümü; Dadi, Seyma
The effects of flower-shaped hybrid nano biocatalyst (hFe-NFs) from coordination between horseradish peroxidase (HRP) enzyme and Fe2+ ions on the free-radical polymerization reactions of three different vinyl monomers (styrene, methylmethacrylate and acrylamide) were investigated. Polymerizations of styrene and methylmethacrylate (MMA) were performed under emulsion conditions using three different surfactants in the presence of acetylacetone (AcAc) and hydrogen peroxide (H2O2) initiator. Polymerization of water soluble acrylamide was accomplished under surfactant-free media. According to the obtained outcomes, hFe-NFs exhibited higher catalytic activity towards polymerization of vinyl monomers compared to the free-HRP enzyme in terms of yields and the number average molecular weights (Mn) of the synthesized polymers. hFe-NFs also demonstrated very high thermal stability. While optimum polymerization of styrene was achieved at room temperature (RT), the highest polymerization yields for acrylamide and MMA were respectively accomplished at 70 and 60 degrees C in which free-HRP enzyme loses its catalytic activity. Preparation of the flower-shaped hFe-NFs, therefore, enables inexpensive and stable catalyst system for free-radical polymerization of vinyl monomers compared to free-HRP enzyme. Increasing catalytic activity and stability of hFe-NFs at higher reaction temperatures are very crucial for utilization of these types of catalysts in both scientific and industrial purposes.
In Situ Synthesis of Horseradish Peroxidase Nanoflower@Carbon Nanotube Hybrid Nanobiocatalysts with Greatly Enhanced Catalytic Activity
(AMER CHEMICAL SOC, 2023) Dadi, Seyma; Temur, Nimet; Gul, O. Tolga; Yilmaz, Vedat; Ocsoy, Ismail; AGÜ, Mühendislik Fakültesi, Malzeme Bilimi ve Nanoteknoloji Mühendisliği Bölümü; Dadi, Seyma
Organic-inorganic hybrid nanoflowers (NFs) consisting of horseradish peroxidase (HRP) and copper II (Cu2+) are successfully synthesized with the involvement of carbon nanotubes (CNTs) by in situ and post-modification methods. Catalytic activities of in situ synthesized HRP-NF@CNT (HRP-NF@CNT-Is) and post-modification-synthesized HRP-NF@CNTs (HRP-NF@CNT-Pm) are systematically examined. The 30 mg CNTs incorporated HRP-NF@CNT-Is (HRP-NF@ CNT-30Is) exhibits greatly increased catalytic activity and stability toward 3,3 ',5,5 '-tetramethylbenzidine (TMB), thanks to the synergistic effect between HRP-NF and CNTs and the peroxidase-like activity of CNTs in the presence of hydrogen peroxide (H2O2). While HRP-NF@CNT-30Is retains almost 85% of its initial activity even after 10 cycles, HRP-NF (without CNTs) loses half of its initial activity at the same experimental conditions. We study how two experimental parameters, the pH values and temperatures, influence the catalytic activity of HRP-NF@CNT-30Is, in addition to the fact that HRP-NF@CNT-30Is is employed to detect the presence of H2O2 and glutathione (GSH) with colorimetric and spectrophotometric readouts. For instance, HRP-NF@CNT-30Is is used to sensitively detect H2O2 in the range of 20 to 300 mu M with an LOD of 2.26 mu M. The catalytic activity of HRP-NF@CNT-30Is is suppressed in the presence of GSH, and then an obvious color change from blue to nearly colorless is observed. Using this strategy, GSH is also sensitively determined in the range of 20-200 mu M with an LOD of 11.2 mu M. We expect that HRP-NF@CNTs can be used as a promising and novel nanobiocatalyst for various biomedical and industrial applications in the near future.
Investigation of Peroxidase-Like Activity of Flower-Shaped Nanobiocatalyst from Viburnum Opulus L. Extract on the Polymerization Reactions
(Turkish Chemical Society, 2024) Kalayci, Berkant; Kaplan, Naime; Mirioglu, Muge; Dadi, Seyma; Ocsoy, Ismail; Gokturk, Ersen; 0000-0001-6280-3966; AGÜ, Mühendislik Fakültesi, Malzeme Bilimi ve Nanoteknoloji Mühendisliği Bölümü; Dadi, Seyma
Here, we report the effects of peroxidase-mimicking activity of flower shaped hybrid nanobiocatalyst obtained from Viburnum-Opulus L. (Gilaburu) extract and Cu2+ ions on the polymerization of phenol and its derivatives (guaiacol and salicylic acid). The obtained nanoflowers exhibited quite high catalytic activity upon the polymerization of phenol and guaiacol. The yields and the number average molecular weights of the obtained polymers were significantly high. Due to solubility issue of salicylic acid in aqueous media, polymerization of salicylic acid resulted in very low yields. Free-horseradish peroxidase (HRP) enzyme is known to be losing its catalytic activity at 60 °C and above temperatures. However, the synthesized nanoflowers exhibited quite high catalytic activity even at 60 °C and above reaction temperatures. This provides notable benefits for reactions needed at high temperatures, and it is very important to use these kinds of nanobiocatalysts for both scientific studies and industrial applications.
Natural Molecule-Incorporated Magnetic Organic-Inorganic Nanoflower: Investigation of Its Dual Fenton Reaction-Dependent Enzyme-Like Catalytic Activities with Cyclic Use
(WILEY-V C H VERLAG GMBH, 2023) Dadi, Seyma; Cardoso, Marlon Henrique; Mandal, Amit Kumar; Franco, Octavio Luiz; Ildiz, Nilay; Ocsoy, Ismail; AGÜ, Mühendislik Fakültesi, Malzeme Bilimi ve Nanoteknoloji Mühendisliği Bölümü; Dadi, Seyma
The functional organic-inorganic hybrid nanoflowers (hNFs) have recently attracted considerable attention due to enhanced catalytic activity and stability. The main purpose of this study is to synthesize new Fenton reagents and investigate their catalytic activity, dye degradation performance and antimicrobial activity. This magnetic gallic acid nanoflowers (FeGANF) were self-assembled via incorporating magnetic nanoparticles (Fe3O4 NPs) into gallic acid (GA) as organic part and copper(II) phosphate (Cu-3(PO4)(2)) as inorganic parts. The FeGANF were characterized by SEM, EDX, FT-IR and XRD. The peroxidase-like activity and dye degradation performance of FeGANF and GANF based on Fenton reaction in the presence of H2O2 was studied toward guaiacol as substrate, using methylene blue (MB) and congo red (CR) as a cationic and anionic dyes, respectively. FeGANF shows much high catalytic activity and decoloration efficiency (97 % for MB and 99 % for CR) because of dual active center in Fenton reaction on the surface of FeGANF. FeGANF exhibited more antimicrobial activity against Escherichia coli ATCC 25922, Staphylococcus aureus ATCC 25923, and Candida albicans ATCC 10231 than that of the GA and GANF. The results of these studies suggest that magnetic hNFs has proved to be promising Fenton reagents for biological and environmental applications including treatment of wastewater.
Production of flower-shaped nanobiocatalysts from green tea and investigation of their peroxidase mimicking activity on the polymerization of phenol derivatives
(WILEY Online Library, 2024) Kalayci, Berkant; Kaplan, Naime; Dadi, Seyma; Ocsoy, Ismail; Gokturk, Ersen; 0000-0001-6280-3966; AGÜ, Mühendislik Fakültesi, Malzeme Bilimi ve Nanoteknoloji Mühendisliği Bölümü; Dadi, Seyma
Enzyme catalyzed reactions are known to be environmental friendly and easy method for many applications. However, utilization of enzymes in a variety of reactions is strictly limited due to their high cost, instability in aqueous solutions, denaturation in organic solvents and high temperatures. For this reason, it is important to discover new generation catalyst systems indicating enzyme-like catalytic activity. Here, we report hybrid organic-inorganic flower-shaped green tea-Cu2+ nanobiocatalyst synthesized from green tea extract as an organic component and copper (II) ions (Cu2+) as inorganic component. The effect of the peroxidase-mimicking activity of green tea-Cu2+ nanobiocatalyst was investigated on the polymerization of phenol and derivatives (guaiacol and salicylic acid) through Fenton-like reaction mechanism. Obtained successful outcomes showed that the synthesized nanobiocatalyst showed very high catalytic activity upon polymerization of phenol and guaiacol. The slight solubility of salicylic acid in water limited to achieve its polymerization under-performed reaction conditions. The yields and molecular weights of the obtained polymers were found to be quite high. While free peroxidase enzymes like horseradish peroxidase (HRP) enzyme loses its catalytic activity at 60 degrees C and above temperatures, green tea-Cu2+ nanobiocatalyst exhibited very high catalytic activity upon polymerization reactions even at 60 degrees C reaction temperature. This outcome provides significant advantages in some reactions requiring high temperatures. In order to understand the origin of the catalytic activity of the green tea-Cu2+ nanoflowers, similar biocatalysts were also synthesized from caffeine and catechin alkaloids which are the active components of green tea. Caffeine-Cu2+ and catechine-Cu2+ nanobiocatalysts also exhibited quite high catalytic activity toward polymerization of phenol and derivatives. We suggest that green tea-Cu2+ and similar types of nanobiocatalysts may expand their utilization in polymer chemistry as promising catalytic agents for radicalic polymerizations.
Rational design of EDTA-incorporated nanoflowers as novel and effective endodontic disinfection against biofilms
(SPRINGER, 2024) Aslan, Tugrul; Dadi, Şeyma; Kafdag, Ozgur; Temur, Nimet; Ildiz, Nilay; Ocsoy, Ismail; Ustun, Yakup; 0000-0001-6280-3966; AGÜ, Mühendislik Fakültesi, Malzeme Bilimi ve Nanoteknoloji Mühendisliği Bölümü; Dadi, Şeyma
The ethylenediaminetetradiacetic acid (EDTA) is one of the most commonly used irrigation solutions. Although EDTA has a very low antimicrobial property, it is used to remove inorganic part of smear layer in areas of root canal system. Herein, we developed EDTA-incorporated nanofowers (EDTA NFs), for the frst time, as novel and efective irrigation solution with quite high antimicrobial property to provide complete disinfection in root canal system. We both systematically elucidated the formation of the EDTA NFs with various techniques, and their catalytic and antimicrobial activities in the presence of hydrogen peroxide (H2O2) were documented through intrinsic EDTA property and peroxidase-like activities.
UV light promoted dihydrolipoic acid and its alanine derivative directed rapid synthesis of stable gold nanoparticles and their catalytic activity
(Nature Research, 2024) Temur, Nimet; Dadi, Seyma; Nisari, Mustafa; Ucuncuoglu, Neslihan; Avan, Ilker; Ocsoy, Ismail; AGÜ, Mühendislik Fakültesi, Malzeme Bilimi ve Nanoteknoloji Mühendisliği Bölümü; Dadi, Seyma
In general, colloidal gold nanoparticles (AuNPs) have been synthesized in heated or boiling water containing HAuCl4 precursor with sodium citrate as reducing stabilizing reagent. Although temperature plays a driving for synthesis of AuNPs, elevated temperature in thermal reduction method causes aggregation of the AuNPs. The preferential, rapid and strong binding of dihydro-lipoic acid and its derivatives on surface of AuNPs via thiol − Au chemistry promote the production of very stable AuNPs. In this study, we have developed citric acid (CA), dihydrolipoic acid (DHLA) and DHLA-Alanine (DHLA-Ala) directed rapid synthesis of ultra-stable AuNPs, DHLA@AuNPs and DHLA-Ala@AuNPs, under the UV (311 nm) irradiation at room temperature (RT: 25 °C) in around 10 min (min). CA is used as a potential reducing agent to expedite both reduction of Au3+ ion and AuNP formation, DHLA and DHLA-Ala act as stabilizing agents by replacing CA molecules on surface of AuNPs in order to produce quite stable AuNP. It is worthy to mention that reduction of Au3+ ion, formation and surface stabilization of AuNPs are consequently occurred in one step. We also investigated how experimental parameters including reaction time and temperature, pH of reaction solution, affect formation of the AuNPs. The effects of salt concentration and storage temperature were studied to show stability of the AuNPs. The synthesized DHLA@AuNPs and DHLA-Alanine@AuNPs were characterized via UV-Vis spectrophotometer (UV-Vis), scanning transmission electron microscope (STEM), dynamic light scattering (DLS) and Zeta potential (ZT) devices. The reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) was efficiently catalyzed by the AuNPs in the presence of sodium borohydride in aqueous solution.