Nahit AKTAŞ

Article | 2023 | Materials Chemistry and Physics298

Ovarian cancer is a gynecological disease causing many deaths among women around the world. Carbohydrate antigen 125 (CA-125) is a single biomarker known to be a tumor marker of ovarian cancer. CA-125 is widely used to monitor the treatment process, recurrences, and for the detection of ovarian cancer. Herein, organo-hydrogels were prepared in order to detect CA-125 sensitively in serum medium with electrochemical methods. Organo-hydrogels were obtained by the free radical polymerization reaction using agar and glycerol with varying proportions of sweet almond oil using methylene bisacrylamide (MBA) or glutaraldehyde (GA) crosslinke . . .rs. Electrochemical measurements were performed with cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and differential pulse voltammetry (DPV) on organo-hydrogel sweet almond oil (OHSAO) prepared in the presence and absence of CA-125. As a result of these measurements, two distinct linear ranges of 1–50 ng/mL and 100–1000 ng/mL were obtained. In addition, LOD and LOQ values for the sensor were calculated as 0.41 μU/mL and 1.24 μU/mL, respectively. In conclusion, the OHSAO-based electrochemical sensor is a promising electrode for CA-125 detection.Keywords: Organo-hydrogel, Sweet almond, CA-125, Ovarian cancer, Senso More less

Nahit AKTAŞ

Article | 2023 | Vietnam Journal of Chemistry61 ( 6 )

As oak bark extract includes pharmaceutically meaningful precious biochemicals such as vanillic acid, quercetin, catechin, caffeic acid, gallic acid, ferulic acid, syringic acid, chlorogenic acid, q-coumaric and protocatechuic acid, the present study focuses on synthesizing polymeric particles from that extract while keeping their targeted natural bioactivity. In this study, due to the bioavailability of oak bark extracts, poly(Oak bark)water extract (p(OB)w), poly(Oak bark)ethanol extract (p(OB)e) and poly(Oak bark)water-ethanol extract (p(OB)we) particles were synthesized using redox polymerization method. Additionally, the biocom . . .patibility, hydrogen peroxide scavenging (H2O2), antioxidant and antimicrobial activities of these substances were investigated. The characterization of the synthesized particles was conducted by FTIR and SEM methods. It was determined that even low amounts of particles (1 mg) had high antioxidant and H2O2 activity. It was found that the particles (0.1 mg/mL) showed antimicrobial activity against Staphylococcus aureus, Bacillus cereus, Enterococcus faecalis, Escherichia coli, Pseudomonas aeruginosa, Candida albicans within the parameters tested for antimicrobial activity. Paracetamol, which is widely used as a model drug and especially recommended for use in the Covid-19 outbreak, was chosen to test the release potential of the p(OB)w, p(OB)e and p(OB)w-e particles. Paracetamol release studies were measured with a UV-VIS spectrophotometer at pH 7.4 and 37°C. Keyword: antioxidant; biocompatible; H2O2 scavenging; Oak bark extract; particl More less

Nahit AKTAŞ

Article | 2019 | Applied Surface Science471 ( 31 )

Herein, it is reported an effective method to prepare novel molecularly imprinted polymers (MIP) on poly(dimethylsiloxane) (PDMS) elastomer via a combination of non-covalent imprinting approach and surface initiated reversible addition fragmentation chain transfer (SI-RAFT) polymerization for sensitive and selective detection of folic acid (FA). For this purpose, 2-(2-Methoxyethoxy) ethyl methacrylate (MEOMA), ethylene glycol dimethacrylate (EGDMA), azobisisobutyronitrile (AIBN), FA and dimethylsulfoxide (DMSO) were used as functional monomer, cross-linker, initiator, template molecule, and porogen, respectively. The adsorption beha . . .vior followed the Scatchard equation between FA and PDMS-MIP with a saturation adsorption capacity of 4.51 mg/g and pseudo-second-order kinetics with 60 min equilibrium adsorption time. Furthermore, PDMS-MIP elastomer was successfully applied for selective extraction and detection of FA from orange juice with sufficient recovery (95.5–100.5?and relative standard deviation less than 7.0?The limit of detection (LOD) for FA was found to be 0.0031 µg/mL with a linear range between 0.01 and 100 µg/mL and a correlation coefficient of 0.9997. Results showed the proposed method could easily, efficiently and selectively extracted FA from complex media. Note that this novel proposed method will open a new way to detect any selected molecules such as pesticide, protein, drug, etc. using molecularly imprinted PDMS elastomer materials More less

Nahit AKTAŞ

Article | 2021 | Inorganic Chemistry Communications126

The catalytic effects of metal nanoparticles (MNPs) synthesized in sodium bis(2-ethylhexyl) sulfosuccinate (AOT) microemulsion system by using M(II) salts (M = Fe, Co, Ni) and NaBH4 reducing agent on methylene blue (MB) degradation reaction were investigated. It was determined that Co-MNPs gave the best catalytic activity among them. Influence of the reaction parameters e.g., reaction time, temperature, the size of catalyst and the MNP types on the catalytic performance were studied. It was found that 37 /- 6 nm Co-MNPs revealed the best catalytic activity in all studies. The best activation parameters were calculated as 13.6 /- 1.1 . . . kJ mol(-1) and Delta H = 10.7 /- 1.0 kJ mol(-1) and Delta S = -87.9 /- 5.4 J mol(-1) K-1. The activity ?f Co-MNPs was calculated as 85.4 after 30 days on the shelf life study. The reusability studies were carried out and the activity of Co-MNPs at the 5th reuse was calculated as 70 /- 5?Finally, the catalytic activity of Co-MNPs was investigated inside equal volumes of single and multiple solution mixtures containing MB, 4-Nitrophenol (4-NP) and Eosin Y (EY). In the examinations, it was observed that the nanocatalyst was effective as a reducing agent in all equal amount solutions (MB/4-NP, MB/EY, 4-NP/EY, and MB/4-NP/EY). And also, TOF (mole of MB/4-NP/EY) (mol catalyst.min)(-1) values of catalytic activities were also calculated More less

Nahit AKTAŞ

Article | 2020 | Journal of Drug Delivery Science and Technology60

In this study, it was aimed to investigate the synthesis, characterization and drug release behaviors of organohydrogels containing pH-sensitive Agar (A), Glycerol (G), Thyme Oil (TO). The novel organo-hydrogels containing TO were prepared in an emulsion media by the free-radical polymerization and crosslinking reactions among Agar (A), Glycerol (G), TO, N, N, methylenebisacrylamide (MBA) or glutaraldehyde (GA) reagent. Swelling ability (ethanol, acetone, ethanol/ID water (1:1), acetone/ID water (1:1) and gasoline environments and different pH), Fourier Transform Infrared Spectroscopy (FTIR) analysis and 5-Fluorouracil (5-Flu) drug . . .release of the organo-hydrogels were profoundly determined and some structural parameters for organohydrogels such as blood clotting, hemolysis analysis, antioxidant analysis were also evaluated in this study. The FTIR spectra confirmed that the TO was bonded onto the organo-hydrogel structure, and the A, G and TO macromolecular chains interpenetrated through the MBA or GA reagent. When swelling analyzes were examined, it was determined that organo-hydrogels, which added thyme oil to the structure, swelled not only in pure water and tap water but also in organic solvents such as ethanol, acetone, ethanol/ID water (1:1), acetone/ID water (1:1) and gasoline. All of the organo-hydrogels synthesized in the light of blood clotting, hemolysis analysis, antioxidant analysis were hemocompatible and could be used within the body. The release results indicated that the organo-hydrogel p(AG-m-TO)(3) and p(AG-g-TO)(3) had the highest 84.3?nd 73.3?elease capacity. In addition, it was reported that the release capacities of organo-hydrogels were inversely proportional to the increased amount of TO. When 5-Flu drug release was examined in terms of kinetic models, it was observed that the release adapted to the Korsmeyer-Peppas (KPKM) model. And it was also determined that organo-hydrogels based on p(AG-m-TO) comply with the non-Fick law and organo-hydrogels based on p(AG-g-TO) comply with the Case II transport. In the light of the results obtained, their easy formability, their appropriate mechanical and physical properties make Organo-hydrogels suitable candidates for drug delivery systems More less

Nahit AKTAŞ

Article | 2021 | Materials Chemistry and Physics267

At present, a voltammetric L-Cystein (Cys) sensor is developed based on carbon nanotube (MWCNT) supported Ru, Pd, and Pt monometallic catalyst modified glassy carbon electrodes (GCE). Ru/MWCNT, Pd/MWCNT, and Pt/MWCNT catalysts are prepared via sodium borohydride reduction method and characterized with advanced surface analytical techniques as inductively coupled plasma mass spectrometry (ICP-MS), N2 adsorption-desorption, X-ray diffraction (XRD), and transission electron microscopy (TEM). Characterization results reveal that these catalysts are succesfully sythesized at desired metal loadings. For electrochemical studies, GCE is mod . . .ified with Ru/MWCNT, Pd/MWCNT, and Pt/MWCNT catalysts to obtain a disposable, inexpensive, and sensitive sensor for Cys. The electrochemical behavior of the modified GCE is investigated by cyclic voltammetry (CV), differential pulse voltammetry (DPV), and electrochemical impedance spectroscopy (EIS). Ru/MWCNT modified GCE electrode exhibits best Cys electro-oxidation activity and thus, further electrochemical studies as sensitivity and limit of detection determination, intereference study, and real sample analysis are performed on Ru/MWCNT modified GCE electrode. The Cys sensor has a linear response within the range of 0–200 μM with current sensitivity 0.3058 μA/μM (4307.05 μA/mMcm2), and 0.353 lowest detection limit at (S/N = 3) signal to noise ratio. Interference studies reveal that Ru/MWCNT modified GCE electrode is not affected by d-glucose, uric acid, l-Tyrosine, l-Trytophane, H2O2, homocysteine, and glutathione as common interfering species. The developed sensor based on Ru/MWCNT modified GCE electrode is also employed to quantify Cys in acetylcysteine drug sample. This novel study reports a strategy to sense Cys on Ru/MWCNT modified GCE electrode More less

Nahit AKTAŞ

Article | 2022 | Journal of Polymer Research29 ( 12 )

Over or under the application of fertilizers raises concerns about soil and environmental degradation, and the recently developed controlled application of fertilizers is the focus of addressing these concerns. In this study, we aimed to synthesize a new N,N-Dimethylacrylamide (DMAAm)-Maleic Acid (MA) - Starch (St)-based superabsorbent (p(DMAAm-co-MA-co-St) (DMSt(1))) and to evaluate the suitability of controlled release fertilizers in lettuce cultivation. HCl/NaOH were used to create negative and positive surface modifications of DMSt(1) and respectively, were named to be p(DMAAm-co-MA-co-Starch)/HCl (DMSt(2)) and p(DMAAm-co-MA-co- . . .Starch)/NaOH (DMSt(3)). The finished product had a high-water absorbency and improved the soil's water retention capacity. Moreover, after the urea sorption and release studies of the synthesized superabsorbent were carried out in vitro, their effects on the development of the lettuce plant were also examined. During the application, the length, root diameter, number of leaves, chlorophyll amount and color characteristics of the lettuce were measured. It was also observed and photographed how the morphological and structural properties of lettuce were affected by applying drought stress. At the end of the drought stress, the color of the lettuce growing in pots with hydrogel was found to be greener and the chlorophyll content was higher compared to the control group. In addition, according to the results of the membrane damage index obtained from lettuce leaves, it was determined that water deficiency did not occur in the lettuce thanks to the hydrogels, and thus, no deterioration in the structure of the membranes occurred. In summary, it can be said that the newly synthesized superabsorbent has an alternative application potential in agricultural production More less

Urmat Coldoşbek Uulu | Nahit AKTAŞ

Article | 2023 | MANAS Journal of Engineering (MJEN)11 ( 1 )

In this study, poly(2-hydroxyethyl-sodium methacrylate) (p(HEMA-SMA)) hydrogels were synthesized as a novel adsorbent to remove antibiotic residues from environmental samples. [p(HEMA-SMA)] co-polymers were synthesized by the free radical photopolymerization method. Synthesized hydrogels were characterized by different methods such as Fourier-transform infrared spectroscopy (FTIR), elemental and scanning electron microscope (SEM), and surface area calculations. The average size surface area of the synthesized hydrogels were 1.515 µm. Penicillin G (Pen. G) was used as the sample antibiotic for the adsorption process. The absorption o . . .f the drugs was studied under different environmental conditions. Medium pH, temperature, and hydrogel concentration were varied to achieve the highest absorption. The specific adsorption value (Qmax) of p(HEMA-SMA) copolymers was found 303.03mg/g for Penicillin G at the 0,35 mg/mL of initial Pen. G concentration. In conclusion, we suggest a novel microstructure, selective, low-cost adsorption polymeric material for the removal of Pen. G as the template antibiotic. Keyword: removal of penicillin G; copolymer; sorption isother More less

Nahit AKTAŞ

Article | 2023 | Canadian Journal of Chemical Engineering102 ( 1 )

The synthesis of p(ClO) and p(TO) organo-particles from clove oil and thyme oil is the first in the literature. The particles were tested against the L-929 cell line for cell viability/cytotoxicity. The anticancer activity was studied against the Capan-1 pancreatic cancer cell line. p(ClO) and p(TO) organo-particles were featured by thermogravimetry (TGA), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), particle size (DLS), and particle charge (zeta potential, Zeta) analyses. Antioxidant, biocompatible, antimicrobial, and in vitro cytotoxicity specialties were investigated. p(ClO) and p(TO) organ . . .o-particles were found to be effective on the L-929 fibroblast cell line and Capan-1 pancreatic cancer cell line in research on Capan-1 and L-929 cell lines. Additionally, it was shown that large dosages of p(ClO) organo-particles were not hazardous to L-929 cell lines. A difference was found between the rates of cell viability and apoptosis and necrosis when the MTT study findings of p(ClO) and p(TO) organo-particles were studied in Capan-1 cell line. The p(TO) organo-particle had the highest apoptosis rate. At the 100 g mL(-1) concentration, the fibroblast cell viability of p(ClO) and p(TO) organo-particles was 176.46 and 107.78, respectively. The IC50 value derived for the decrease in viability was determined as (2.22 mg mL(-1)) and it was calculated that it would kill the pancreatic cancer cells by 50 when doxorubicin and p(ClO) were administered combined. Keyword: cell; clove oil; organo-particle; thymol oi More less

Nahit AKTAŞ

Article | 2021 | ACS Applied Energy Materials4 ( 11 )

In this study, titanium dioxide (TiO2)-supported Cd catalysts were prepared at 0.05-3 of Cd loading by employing the incipient wetness impregnation method. These catalysts were characterized via X-ray diffraction (XRD), scanning electron microscopy-energy-dispersive X-ray (SEM-EDX), high-angle annular dark-field scanning transmission electron microscopy and TEM-EDS mapping, inductively coupled plasma-mass spectrometry ( ICP-MS), X-ray photoelectron spectroscopy (XPS), temperature-programmed reduction (TPR), temperature-programmed oxidation (TPO), and temperature-programmed desorption (TPD). XRD and TEM analysis showed that TiO2 exhi . . .bited an anatase structure. SEM-EDX and mapping, XPS, TPR, TPO, and TPD analysis revealed that the Cd addition to TiO2 altered the electronic structure and surface properties of TiO2. Photocatalytic electro-oxidation measurements were conducted to define the glucose electro-oxidation activity, stability, and resistance of catalysts with cyclic voltammetry, chronoamperometry (CA), and electrochemical impedance spectroscopy (EIS) in 1 M KOH 0.5 M glucose solution at 100 mV/s in the dark and under UV illumination. 0.1 Cd/TiO2 catalyst showed the best photocatalytic glucose electro-oxidation activity with a 6 mA/cm(2) specific activity compared to the dark (0.89 mA/cm(2)). CA and EIS measurements indicated that 0.1 Cd/TiO2 catalyst exhibited the highest stability and the lowest resistance. In conclusion, Cd-doped TiO2 is a promising catalyst for photocatalytic fuel cells More less

Hilal DEMİR KIVRAK | Nahit AKTAŞ

Article | 2022 | International Journal of Hydrogen Energy47 ( 83 )

Herein, carbon nanotube (CNT)-supported Ga@PdAgCo catalysts were synthesized by sodium borohydride (SBH) sequential reduction method. These catalysts were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and inductively coupled plasma-mass spectrometry (ICP-MS). Characterization results revealed that these catalysts were succesfully preared at desired loading and atomic ratios. From the XRD pattern, the crystallite size of 0.5 Ga@PdAgCo(80:10:10)/CNT catalysts was found as 6.95 nm by utilizing the Scherrer equation. From TEM measurements, the average particle s . . .izes of Pd/CNT, PdAgCo(80:10:10)/CNT, and 0.5 Ga@PdAgCo(80:10:10)/CNT catalysts were found to be 54 nm, 25 nm, and 7 nm, respectively. It is clear that particle sizes obtained from TEM and XRD were close to eachother. Electrochemical impedance spectroscopy (EIS), chronoamperometry (CA), and cyclic voltammetry (CV) measurements were realized to examine the formic acid and ethylene glycol electrooxidation performances of catalysts. 0.5 Ga@PdAgCo(80:10:10/CNT) and 7 Ga@PdAgCo(80:10:10/CNT) catalysts had the best specific activity and mass activity as 3.37 mA/cm(2) (297.61 mA/mg Pd) and 4.95 mA/cm(2) (462.59 mA/mg Pd) for ethylene glycol and formic acid electrooxidation, respectively. In addition, EIS results showed that Ga@PdAgCo(80:10:10/CNT) catalyst had a faster electron transfer rate via low charge transfer resistance. As a result, 0.5 Ga@PdAgCo(80:10:10/CNT) catalyst is a promising new anode catalyst for direct ethylene glycol fuel cells. (c) 2022 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved More less

Nahit AKTAŞ | Ali Osman SOLAK

Article | 2021 | Journal of Electronic Materials50 ( 4 )

In the present work, TiO2 nanotubes (TNT) and carbon-doped TiO2 nanotubes (C-TNT) were produced via the anodization method. Carbon doping was performed on TNT in a tubular oven employing two different 15 cm3/min total flow rates with varying compositions of acetylene (C2H2) and argon (Ar) as VC2H2/Ar = 7/93 (1 cm3/min C2H2   14 cm3/min Ar) for C-TNT (7:93) and VC2H2/Ar = 33/67 (5 cm3/min C2H2   10 cm3/min Ar) for C-TNT (33:67). The synthesized C-doped TNT was characterized by x-ray diffraction (XRD), Raman spectroscopy, and scanning electron microscopy (SEM). XRD, Raman spectra, and SEM results reveal that a carbon film structure wa . . .s formed on the TNT surface. In addition, the electronic structure of TNT changed with doping of carbon on the TNT surface. These carbon-doped TNTs were employed as catalysts for the photocatalytic oxidation of glucose (GA). Cyclic voltammetry (CV), chronoamperometry (CA), and electrochemical impedance spectroscopy (EIS) measurements were carried out to investigate the glucose electro-oxidation activity of the carbon-doped TNTs in the dark and under UV illumination (λ = 354 nm). C-TNT (7:93) exhibited the highest glucose electro-oxidation activity under the dark and UV illumination compared to C-TNT (33:67) and TNT. The glucose electro-oxidation (GAEO) current density on C-TNT (7:93) improved significantly under UV illumination compared to glucose electro-oxidation activity obtained in the dark. C-TNT (7:93) enhanced glucose electro-oxidation activity and stability under UV illumination. This electrode production method is promising for the design of photocatalytic glucose fuel cells More less