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3D Bioprinting Strategies for Melatonin-Loaded Polymers in Bone Tissue Engineering
(Wiley-V C H Verlag Gmbh, 2025) Aykora, Damla; Oral, Ayhan; Aydeger, Cemre; Uzun, Metehan
Bone pathologies are still among the most challenging issues for orthopedics. Over the past decade, different methods are developed for bone repair. In addition to advanced surgical and graft techniques, polymer-based biomaterials, bioactive glass, chitosan, hydrogels, nanoparticles, and cell-derived exosomes are used for bone healing strategies. Owing to their variation and promising advantages, most of these methods are not translated into clinical practice. Three dimensonal (3D) bioprinting is an additive manufacturing technique that has become a next-generation biomaterial technique adapted for anatomic modeling, artificial tissue or organs, grafting, and bridging tissues. Polymer-based biomaterials are mostly used for the controlled release of various drugs, therapeutic agents, mesenchymal stem cells, ions, and growth factors. Polymers are now among the most preferable materials for 3D bioprinting. Melatonin is a well-known antioxidant with many osteoinductive properties and is one of the key hormones in the brain-bone axis. 3D bioprinted melatonin-loaded polymers with unique lipophilic, anti-inflammatory, antioxidant, and osteoinductive properties for filling large bone gaps following fractures or congenital bone deformities may be developed in the future. This study summarized the benefits of 3D bioprinted and polymeric materials integrated with melatonin for sustained release in bone regeneration approaches.
Antibacterial and antibiofilm activities of sodium ibuprofen- and paracetamol-loaded nanofibers
(Society of Chemists and Technologists of Macedonia, 2023) Alkan, Gürkan; Ulusoy, Seyhan; Akgün, Mert; Oral, Ayhan
Nanofibers loaded with pharmaceutical agents for various medical purposes have become more important in recent years because of their advantages, such as control on release, gas permeability, high surface area, and lightweight matrices. In the present study, polylactic acid (PLA)-gelatin (Gel) nano-fibers were successfully loaded with Ibuprofen-Na/Paracetamol (henceforth Ibu-Na and Par, respectively) by electrospinning. The nanofibers were characterized by scanning electron microscopy (SEM) and Fou-rier transform infrared (FTIR) spectroscopy. The Ibu-Na/Par content of the nanofibers was determined by using high-performance liquid chromatography (HPLC). Their antibacterial activities were tested against Enterococcus faecalis ATCC 29212, Staphylococcus aureus ATCC 25923, Escherichia coli ATCC 25922, and Pseudomonas aeruginosa PA01, opportunistic pathogenic bacteria which are frequently asso-ciated with infections. Moreover, their antibiofilm activities against P. aeruginosa and E. faecalis were also investigated. The Ibu-Na-containing nanofibers exhibited antibacterial activity against S. aureus, E. coli, and E. faecalis. The inhibition zone diameters of PLA-Gel-Ibu-Na 300 against E. faecalis, S. aureus, and E. coli were calculated to be 23.0 ± 2.1 mm, 18.0 ± 1.5 mm, and 12.0 ± 1.2 mm, respectively. It was found that PLA-Gel-Ibu-Na 300 and PLA-Gel-Par 300 nanofibers’ capacity to show biofilm formation inhibition originated remarkable effects on P. aeruginosa, which were found to be 48 % and 50.4 %, respectively. This study indicated that Ibu-Na/Par-loaded nanofibers are promising materials for wound healing applications.
Antibiotic loaded electrospun poly (lactic acid) nanofiber mats for drug delivery system
(Elsevier, 2022) Suner, Salih Can; Yildirim, Yeliz; Yurt, Fatma; Ozel, Derya; Oral, Ayhan; Ozturk, Ismail
Active material-loaded nanofibers becoming more important, because of their applications in many areas such as wound healing, skin engineering, and drug release. This study was conducted to compare the release kinetics of three different antibiotics loaded on nanofibers in Phosphate-buffered saline (PBS) solution and their inhibition properties against bacteria. The three different commercial antibiotics; vancomycin (VAN), ceftriaxone (CFT), and cefpodoxime (CFD) were loaded into Polylactic acid (PLA) nanofibers via electrospinning process with different percentages; 5%, 7.5%, and 10% weight ratios of PLA. The SEM images of PLA/Antibiotic nanofibers and pure PLA nanofiber revealed an increase in diameters with the presence of antibiotics embedded in PLA nanofiber. The TGA analysis showed that the thermal degradation of CFD and VAN-loaded nanofibers were higher than neat PLA, while the thermal stability of CFT loaded nanofibers was the lowest. In the Tan Delta curves, the Tg temperatures of CFD, VAN, CFT loaded nanofibers and pure PLA nanofiber were determined as 54.56 degrees C, 54.57 degrees C, 53.86 degrees C, and 53.55 degrees C, respectively. As can be seen from the results, the variation of the glass transition temperatures supports the DSC data. Drug releasing behaviors of PLA/Antibiotic nanofibers were investigated by Ultraviolet-Visible Spectroscopy at 280, 242 and 230 nm wavelength for VAN, CFT, and CFD antibiotics, respectively. Drug-releasing amounts were gradually increased by increasing the drug loading amounts from 5% to 10%. PLA-VAN, PLA-CFT, and PLA-CFD nanofibers which contain 10% of drugs were delivered about 79%, 75%, and 29% of drugs linearly within nearly 380 h, 500 h, and 360 h, respectively. The formulations including CFT at different concentrations were found to be effective against Staphylococcus aureus and Escherichia coli in a dose-dependent manner. The formulations including CFD and VAN at different concentrations have also inhibited the growth of S. aureus.
Anticancer activity of Turkish marine extracts: a purple sponge extract induces apoptosis with multitarget kinase inhibition activity
(Springer, 2020) Ciftci, Halil, I; Can, Mustafa; Ellakwa, Doha E.; Suner, Salih C.; Ibrahim, Mohamed A.; Oral, Ayhan; Sekeroglu, Nazim
Marine natural products have drawn a great deal of attention as a vital source of new drugs for the last five decades. However, marine organisms in the seas surrounding Turkey (the Black Sea, the Aegean Sea and the Mediterranean Sea) haven't been yet extensively explored. In the present study, three marine organisms (Dysidea avara, Microcosmus sabatieri and Echinaster sepositus) were sampled from the Dardanelles (Turkish Straits System, Western Turkey) by scientific divers, transferred to the laboratory and then were extracted with 70% ethanol. The extracts were tested for their cytotoxic effect against K562, KMS-12PE, A549, and A375 cancer cell lines. The sponge extract elicited the most promising cytotoxic activity, thus it was further evaluated against H929, MCF-7, HeLa, and HCT116 cancer cells. Most of the designated cells showed a considerable sensitivity for the sponge extract particularly H929, K562, KMS-12PE and HeLa cells with IC50 less than 10 mu g/mL. On the contrary, the other two extracts exhibited no cytotoxic activity on all cells at 100 mu g/mL concentration. The sponge extract was tested for its capacity to induce apoptosis in cancer cells and to inhibit a panel of tyrosine kinases showing remarkable results. The outcome of this study represents a platform for discovery of new chemotherapeutic agents of marine natural origin.
Cinnamaldehyde-poly (lactic acid)/gelatin nanofibers exhibiting antibacterial and antibiofilm activity
(Taylor & Francis Ltd, 2024) Akpinar, Zeynep; Ulusoy, Seyhan; Akgun, Mert; Oral, Ayhan; Suner, Salih Can
Bacterial infections and biofilms are known to impede the wound-healing process. Naturally derived compounds from plants hold promise in inhibiting or preventing bacterial biofilms, with cinnamaldehyde (CA) being recognized for its antibacterial and antibiofilm properties. In this investigation, three-dimensional, antibacterial, and biodegradable nanofibers were synthesized via electrospinning, employing FDA-approved polylactic acid (PLA), gelatin (Gel), and the phytoactive molecule cinnamaldehyde (CA). The cinnamaldehyde content, morphology, and physical as well as biological characteristics of the electrospun PLA-Gel-CA nanofibers were scrutinized using HPLC, SEM, TGA, and FTIR analysis. The antibacterial activity of the PLA-Gel-CA nanofibers against Staphylococcus aureus and Pseudomonas aeruginosa, along with their antibiofilm activity against P. aeruginosa, were evaluated. The average diameters of PLA-Gel-CA nanofibers, specifically PLA-Gel-CA1, PLA-Gel-CA2, and PLA-Gel-CA3, were determined to be 294.9 +/- 46.8 nm, 254 +/- 58.3 nm, and 728.5 +/- 98.3 nm, respectively. PLA-Gel-CA3 nanofibers demonstrated notable antibacterial efficacy against S. aureus (31.0 +/- 1.20 mm) and P. aeruginosa (16.0 +/- 1.20 mm), along with a significant inhibition of P. aeruginosa biofilm formation by 72.2%. These findings indicate the potential of cinnamaldehyde-loaded nanofibers for wound application owing to their antibacterial and antibiofilm activity, as well as their rapid dissolution characteristics.
Corrosion mitigation performance of disodium EDTA functionalized chitosan biomacromolecule - Experimental and theoretical approach
(Elsevier B.V., 2021) Jessima, S. J. Hepziba Magie; Subhashini, S.; Berisha, Avni; Oral, Ayhan; Srikandan, Subramanian Sathy
Disodium ethylenediaminetetraacetate salt is known for its excellent coordinating properties with the metal ions. The present study deals with the investigation of the prepared Disodium EDTA functionalized chitosan in corrosion inhibition for mild steel in 1 M HCl. The modified chitosan was characterized by spectral studies, thermal analysis, and Zeta potential studies. The corrosion inhibition efficiency (%) was evaluated using the gravimetric method and electrochemical studies. The electrochemical studies included potentiodynamic polarization, linear polarization resistance, and electrochemical impedance methods. The modified chitosan polymer showed an inhibition efficiency of 96.63% for 500 ppm at 303 K. Adsorption process obeyed Langmuir isotherm. Experimental results and theoretical calculations endorsed initial physisorption followed by a chemisorption process. Surface characterization studies supported the formation of a protective film that enabled the inhibition process. Density functional theory, Monte Carlo studies, and molecular dynamics simulation studies show a good agreement with the experimental results. Two-way Analysis of Variance was performed to test the influence of immersion period and inhibitor concentration on the corrosion rate using the statistical software IBM SPSS 20.0. A quartic model was generated as the best fit with the highest R2 value of 0.973. Design Expert software was employed for statistical modeling fit.
Design of Poly(lactic) acid/gelatin core-shell bicomponent systems as a potential wound dressing material
(Elsevier Ltd, 2024) Suner, Salih Can; Oral, Ayhan; Yıldırım, Yeliz
The electrospun core-shell nanofiber has great many advantages such as different types of solvents that can be used for changing flexibility, mechanical properties, or surface chemistry of fiber. Hydrophobic Poly(lactic) acid (PLA) and hydrophilic gelatin (Gel) were electrospun by various preparation conditions to design perfect bicomponent PLA:Gel nanofiber in a core-shell structure. Solvent types, the concentration of polymeric components, flow rate, and voltage of the electrospinning process were changed to optimization of nanofiber. According to the SEM images, the best nanofiber structure without beads was obtained at 0.4 ml/h flow rate of PLA solution and 1.2 ml/h flow rate of Gel solution at 45:55 (w:w %) weight ratio of PLA:Gel in trifluoroethanol solvent with a 10 kV voltage at 10 cm distance to the collector. From the TEM images, the existence of the core-shell structure had been proved which all prepared nanofibers with 2,2,2-Trifluoroethanol solvent. Furthermore, contact angle measurements showed a change in wettability when the Gel amount was increased. Therefore, the mildest synthesis conditions were determined for bicomponent PLA:Gel core-shell nanofibers as a potential wound dressing and dual drug carrier materials.
DETERMINATION OF THE EFFECTS OF HYDROGEL ON IRRIGATION PROGRAM FOR MAIZE CULTIVATED IN THE FIELD CONDITIONS
(Univ Agricultural Sciences & Veterinary Medicine Bucharest, 2016) Tekiner, Murat; Yildirim, Murat; Turkmen, Cafer; Oral, Ayhan; Izci, Bahri
The experiment was carried out at the research center of Canakkale Onsekiz Mart University in Turkey in summer of 2010 and 2011 to determine the effects of hydrogel (organic polymer) on the grain yield and plant development parameters. Maize DKC 5783, a commonly used variety by farmers in Turkey, was used as an indicator plant and the seeds were sowed to different lysimeters having a volume of 1 m(3). The chemical properties of hydrogel and its water holding capacity were determined under laboratory conditions. According to the treatments, certain amounts of hydrogel were mixed to the first 20 cm of the soil from the surface level. Irrigation water was applied in a controlled manner by a scaled container to the root area of maize. Plant development parameters were observed in each development stage. As a result of this study, it was seen that the amount of hydrogel mixed to the soil in different amounts had a significant effect on the plant development parameters, grain yield and also irrigation water use efficiency.
Development of melatonin-embedded PLGA-PEG6000 nanofiber biomaterial, and investigation of the effects on abdominal adhesion formation
(SAGE Publications Ltd, 2024) Gökçe, Oruç Numan; Aykora, Damla; Danışman, Merve; Demir, Ufuk; Aydeğer, Cemre; Süner, Salih Can; Oral, Ayhan; Karaboğa, İhsan; Uzun, Metehan
Abdominal adhesions are still among the most common postsurgical peritoneal inflammation-related complications. Adhesion-related disorders are still highly costly and prevalent due to advances in surgical techniques, treatment methods, and various drugs. The present study aimed to investigate the effects of Poly (D,L-lactide-co-glycolide) (PLGA)- polyethylene glycol (PEG6000) Nanofiber + Melatonin on the abdominal adhesion model in rats. For this purpose, PLGA-PEG6000 Nanofiber + Melatonin matrix was fabricated and implanted in an experimental abdominal adhesion model in rats. Our study consisted of an in vitro and an in vivo part. The degradation and release profile of the matrix and Melatonin (Mel) embedded matrix was performed in vitro. In vivo, the procedure was carried out with 18 Wistar male rats. Rats were divided into three groups as follows: Sham, Matrix, and Mel + Matrix, respectively. Consequent to degradation and release profiling in vitro, an experimental adhesion model was created and fabricated pure matrix (2 × 2 cm2), and matrix (2 × 2 cm2, 0.25 mg melatonin/per matrix embedded) was applied to injury area in related groups. Intra-abdominal adhesion scores were determined on post-op 21st day, under general anesthesia. Following, cecum, peritoneal tissue, and adhesive bands were harvested. Macroscopic analysis (severity of adhesion formation), Hematoxlyn&Eosin and Masson’s Trichrome staining (for the examination of the levels of infiltration of inflammatory cells, fibrosis, and neovascularization) were performed for the evaluation of the effects of Mel embedded and pure matrix Our results indicated that PLGA-PEG6000 Nanofiber + Melatonin matrix was degraded completely in rats abdominal cavity and significantly reduced adhesion formation compared to other groups macroscopically (p < 0.05). On the other hand, the histopathological analysis indicated that the fabricated matrix reduced inflammatory cell infiltration, fibrosis, and neovascularization levels.
Diatomaceous Earth: Characterization, thermal modification, and application
(De Gruyter Open, 2021) Reka, Arianit A.; Pavlovski, Blagoj; Fazlija, Emira; Berisha, Avni; Pacarizi, Musaj; Daghmehchi, Maria; Oral, Ayhan
The diatomaceous earth (DE), collected from the Mariovo region in North Macedonia, was characterized and thermally modified. The material represents a sedimentary rock of biogenic origin, soft solid that can be easily disintegrated, with white to grayish color, with bulk density of 0.51–0.55 g/cm3, total porosity of 61–63%, and specific gravity of 2.25 g/cm3. The chemical composition is as follows: SiO2, 86.03; Al2O3, 3.01; Fe2O3, 2.89; MnO, 0.06; TiO2, 0.20; CaO, 0.76; MgO, 0.28; K2O, 0.69; Na2O, 0.19; P2O5, 0.15; and loss of ignition, 5.66 (wt%). The mineralogy of the raw DE is characterized by the predominant presence of amorphous phase, followed by crystalline quartz, muscovite, kaolinite, and feldspar. Significant changes in the opal phase are observed in the 1,000–1,200°C temperature region. At 1,100°C, the entire opal underwent solid–solid transition to cristobalite. Further ramp of the temperature (1,100–1,200°C) induced formation of mullite. Scanning electron microscopy (SEM) and transmission electron microscopy depict the presence of micro- and nanostructures with pores varying from 260 to 650 nm. SEM analysis further determined morphological changes in terms of the pore diameters shrinkage to 120–250 nm in comparison to the larger pores found in the initial material. The results from this investigation improve the understanding of mechanism of silica phase transition and the relevant phase alterations that took place in DE upon calcination temperatures from 500 to 1,200°C.
Effects of types and concentrations of modified Cloisite Clays on properties of chitosan nanocomposites for food packaging
(John Wiley and Sons Ltd, 2023) Caner, Cengiz; Rahvalı, Fatih; Yüceer, Muhammed; Oral, Ayhan
Biodegradable chitosan has excellent film-forming properties compared to other biodegradables but also some limitations, such as poor water barrier and low mechanical strength. Thus, in this research, the effects of various types (Cloisite Ca, 15A, 20A, and 30B) and concentrations (0.5, 1, 2.5, and 5 wt%) of Cloisite on barrier, mechanical, structural and thermal properties on chitosan films were investigated. Cloisite was revealed to significantly lower the lightness (L*) depending on the type and concentration of Cloisite. The films containing Cloisite significantly improved oxygen barrier properties by 34.5%-73.6% compared to control, particularly Cloisite 30B. Cloisite 20A and Ca were found to significantly improve the water barrier by up to 84.61%, and Cloisite 20A and 30 B the tensile properties by up to 30%. The chitosan with less Cloisite content exhibited better smoothness and elongation. The dispersed Cloisite clays improved the thermal stability and enhanced the barrier and tensile properties of the chitosan with the increased Cloisite loading.
Electrochemical behaviour of 5-(furan-2-yl)-4-(p-tolyl)-2,4-dihydro-1,2,4- triazole-3-thione by using glassy carbon electrode
(Chemical Publishing Co., 2007) Dilgin, Yusuf; Cansiz, Ahmet; Çetin, Ahmet; Kutulay, Pelin; Oral, Ayhan; Yilmaz, Selahattin
The electrochemical study of a thiotriazole compound, 5-(furan-2-yl)-4-(p- tolyl)-2,4-dihydro-1,2,4-triazole-3-thione (TTA) was performed by cyclic voltammetry (CV) and differential pulse voltammetry (DPV) using glassy carbon electrode (GCE) as working electrode and an Ag/AgCl reference electrode. The dependence of the current on pH and scan rate was investigated in the Britton Robinson Buffer. The best results for electrooxidation of TTA were obtained in basic media (pH 11.0 containing 5 % DMSO). This compound display one irreversible oxidation peak, which is attributed to a dimerization process involving the formation disulphide derivative.
Electrochemical behaviour of 5-(Furan-2-yl)-4-(p-tolyl)-2,4-dihydro-1,2,4-triazole-3-thione by using glassy carbon electrode
(Asian Journal Of Chemistry, 2007) Dilgin, Yusuf; Cansiz, Ahmet; Cetin, Ahmet; Kutulay, Pelin; Oral, Ayhan; Yilmaz, Selahattin
The electrochemical study of a thiotriazole compound, 5-(furan-2-yl)-4-(p-tolyl)-2,4-dihydro-1,2,4-triazole-3-thione (TTA) was performed by cyclic voltammetry (CV) and differential pulse voltammetry (DPV) using glassy carbon electrode (GCE) as working electrode and an Ag/AgCl reference electrode. The dependence of the current on pH and scan rate was investigated in the Britton Robinson Buffer. The best results for electrooxidation of TTA were obtained in basic media (pH 11.0 containing 5 % DMSO). This compound display one irreversible oxidation peak, which is attributed to a dimerization process involving the formation disulphide derivative.
Elektropüskürtme Yönteminin Probiyotik Mikroorganizmaların Mikrokapsülasyonunda Kullanımı
(2017) Ergin, Firuze; Küçükçetin, Ahmet; Oral, Ayhan; Gürsoy, Oğuz
Probiyotik bir üründen beklenen faydaların sağlanabilmesi için ürünün raf ömrü sonuna kadar en az 108-109 kob/g düzeyinde canlı probiyotik mikroorganizma bulundurması gerekmektedir. Probiyotik mikroorganizmaları olumsuz koşullara karşı korumak amacıyla çok sayıda yöntem geliştirilmiştir. Konu ile ilgili yapılan çalışmalar, probiyotik mikroorganizmaların canlılığını korumada en etkili yöntemlerden birinin mikrokapsülasyon olduğunu göstermektedir. Bununla birlikte, mikrokapsülasyon işlemi sırasında probiyotik mikroorganizmalar yüksek sıcaklık, dehidrasyon, yüksek osmolarite gibi olumsuz koşullara maruz kalabilmektedir. Elektrohidrodinamik atomizasyon yani elektroeğirme ve elektropüskürtme yöntemleri kullanılarak söz konusu olumsuz koşulların üstesinden gelinebilmektedir. Son zamanlarda yapılan çalışmalarda; yüksek voltaj altında kapsüller (elektropüskürtme) veya lifler (elektroeğirme) üretilmesini sağlayan elektrohidrodinamik atomizasyon tekniğinin, probiyotik mikroorganizmaların canlılıklarının korunması açısından diğer mikrokapsülasyon yöntemlerine alternatif olabileceği belirtilmiştir. Bu derlemede, elektrohidrodinamik atomizasyon tekniğinin temelleri ve elektropüskürtme yönteminin probiyotik mikroorganizmaların mikrokapsülasyonunda kullanım olanakları ile ilgili bilgi verilmesi amaçlanmıştır.
Environmentally-friendly preparation of chitosan microspheres and encapsulation studies of cinnamaldehyde: ?owards convenient sustained release system for cinnamaldehyde
(Macedonian Journal of Chemistry and Chemical Engineering, 2021) Yeldir, Elif Karacan; Oral, Ayhan
Chitosan, a biodegradable and biocompatible polysaccharide, is a biopolymer with high potential for biomedical applications. In the scope of this study, chitosan microcapsules were prepared via a green method, without using any surfactants or crosslinkers. Cinnamaldehyde encapsulated microspheres were obtained by the same method and characterized by FTIR spectroscopy, XRD spectroscopy, and SEM. The release study of encapsulated cinnamaldehyde was carried out in a pH 7.4 phosphate buffered saline (PBS) at 37 °C. The amount of cinnamaldehyde released was analyzed using UV-Vis spectroscopy and GC/MS-MS. Accordingly, it was found that 350 mg of cinnamaldehyde was encapsulated per gram of chitosan, and the maximum amount of cinnamaldehyde released into the PBS medium was about 8 ppm. In addition, the release was seen to continue when the buffer was renewed. It is thought that the obtained cinnamaldehyde encapsulated chitosan microspheres could be used as a sustained release system.
Farklı Sulama Suyu Tuzluluk Düzeylerinin Mısırın Fide Gelişimine Etkileri
(2020) Coşkun, Yalçın; Taş, İsmail; Akçura, Mevlüt; Oral, Ayhan; Tütenocakl, Tülay; Yeter, Tuğba
Sulama suyunun SAR değeri suyun kalite sınıfının belirlenmesinde birincil parametredir. Bu nedenle SARdeğeri dikkate alınmadan sodyum tuzu ile yapılan çalışmalarda elde edilen sonuçlar tuz zararı olmayıp sodyumzararını temsil etmektedir. Mısır bitkisinin sulama suyu tuzluluğunu hangi seviyeye kadar tolere edilebileceğinitespit etmek amacıyla SAR değeri 1’in altında ayarlanarak farklı tuz konsantrasyonuna sahip sulama suları ileçimlendirme ve saksı denemeleri yapılmıştır. Çimlendirme denemesi sonucunda sulama suyu tuzlulukseviyesindeki artışa paralel olarak kök uzunluğu, fide kuru ağırlığı ve çimlenme oranı azalmıştır. Kök uzunluğusulama suyu tuzluluğunun 3 dS m-1 ECi seviyesinde olumsuz etkilenmeye başlarken fide kuru ağırlığı veçimlenme oranı 5 dS m-1 ECi seviyesinde etkilenmeye başlamıştır. Saksı denemesinde sulama suyu tuzlulukseviyesindeki artışa paralel olarak bitki boyu ve bitki kuru ağırlığı değerleri azalmış olup 8 dS m-1 ECi seviyesindeolumsuz etkilenmiştir.
First record of straight-needle pteropod Creseis acicula Rang, 1828 bloom in the Canakkale Strait (NE Aegean Sea, Turkey)
(De Gruyter Open Ltd, 2021) Tuncer, Sezginer; Öǧretmen, Nazik; Çakır, Fikret; Öztekin, Alkan; Oral, Ayhan; Suner, Salih Can
Pteropods are marine pelagic calcifier mollusks sensitive to chemical changes in seawater due to their highly soluble aragonite shells. Increased acidity (reduced pH) of seawater causes difficulties in precipitating their shells and/or results in their dissolution, which is related to increased atmospheric CO2 concentrations and warming of seawater. They are therefore indicators of environmental changes. In this paper, we present the first record of the straight-needle pteropod Creseis acicula Rang, 1828 bloom in the surface waters of the Çanakkale Strait, Turkey (NE Aegean Sea), encountered in July 2020, when the highest sea surface temperatures and pH levels since 2007 were recorded. In coastal zones, such as the Çanakkale Strait, anthropogenic activity contributes significantly to environmental changes. Consequently, the increase in pH at elevated temperatures indicates an auxiliary factor (i.e. anthropogenic activity) that triggered the C. acicula bloom, rather than global atmospheric CO2 levels.
Geraniol and cinnamaldehyde as natural antibacterial additives for poly(lactic acid) and their plasticizing effects
(Walter De Gruyter Gmbh, 2020) Akgun, Mert; Basaran, Ihsan; Suner, Salih C.; Oral, Ayhan
The main goal of this study is to prepare antibacterial poly(lactic acid) (PLA) containing cinnamaldehyde and geraniol and to evaluate the antibacterial activity and assess the changes of physical properties of the PLA films. Cinnamaldehyde- and geraniol-incorporated (10%, 20%, 30%, and 50% v/w) PLA films were prepared via solution-casting. While preparing these films, plasticizers were not added to the matrix. Antibacterial activities of these films against Escherichia coli and Staphylococcus aureus were investigated by the disk diffusion method. Thermal degradation characteristics were analyzed via thermogravimetric analysis (TGA), glass transition, crystallization, and melting temperatures, and enthalpies of the films were determined from differential scanning calorimetry (DSC) scans. Tensile strength and elongationat-break values of neat PLA and antibacterial-compound-containing films were evaluated and compared after the mechanical tests. Moreover, the changes in the polymer morphology were observed by SEM analysis, and opacity of the films was determined by UV-vis spectroscopy. Our results showed that both compounds provided antibacterial effect to the PLA, with cinnamaldehyde being more effective than geraniol. Moreover, plasticization effects of the compounds were confirmed by DSC analysis.
Grafting of poly(?-caprolactone) on electrospun gelatin nanofiber through surface-initiated ring-opening polymerization
(Taylor & Francis As, 2018) Basaran, Ihsan; Oral, Ayhan
Gelatin-polycaprolactone hybrid materials are being used in medicinal applications such as drug delivery, tissue engineering applications nowadays. In this study, gelatin-polycaprolactone graft copolymer was synthesized through ring-opening polymerization process instead of conventional grafting methods using potentially cytotoxic crosslinkers, or applying plasma, aminolysis reactions. Gelatin nanofiber (GNF) was produced by electrospinning process before immobilization of poly(epsilon-caprolactone). Ring-opening polymerization of epsilon-caprolactone was successfully initiated on the surface of GNF using tin(IV) isopropoxide and gelatin (primary amine functional groups) as an initiator and a coinitiator, respectively. The growing of polymer chains on GNF was indicated by both scanning electron microscope and energy-dispersive X-ray spectroscopy. Chemical structure was characterized through infrared spectrum, thermal behaviors and the material composition was analyzed with thermogravimetric analysis, wettability and hydrophilicity were determined by water contact angle measurements. [GRAPHICS] .
Highly sensitive voltammetric determination of the fungicide fenhexamid using a cost-effective and disposable pencil graphite electrode
(Springer Wien, 2024) Ersan, Teslime; Dilgin, Didem Giray; Oral, Ayhan; Skrzypek, Slawomira; Brycht, Mariola; Dilgin, Yusuf
A differential pulse voltammetric (DPV) method is proposed for the highly sensitive determination of fenhexamid (FHX) based on both electrooxidation and electroreduction processes using a disposable and cost-effective pencil graphite electrode (PGE). The electrochemical oxidation and reduction mechanisms of FHX at the PGE were elucidated by recording cyclic voltammograms at various pH values of Britton-Robinson buffer (BRB) solutions at a scan rate of 50 mV s-1 and different scan rate values in the range 10-400 mV s-1 at selected pH of BRB (pH 2.0). Differential pulse voltammograms recorded under optimized conditions revealed an oxidation peak of FHX around + 0.65 V and a reduction peak of FHX around + 0.45 V. The DPV analysis of FHX revealed two linear ranges: 0.001-0.01 mu mol L-1 and 0.01-5.0 mu mol L-1 for the anodic peak, and 0.001-0.1 mu mol L-1 and 0.1-5.0 mu mol L-1 for the cathodic peak. The limits of detection were 0.34 nmol L-1 and 0.32 nmol L-1 for the anodic and cathodic peaks, respectively. The proposed methodology demonstrated satisfactory selectivity, as selected pesticides, certain electroactive compounds, and cationic species tested did not interfere with the voltammetric determination of FHX, particularly during its reduction. The recovery results, showing values close to 100% obtained from the analysis of real samples spiked with FHX, indicated that this methodology can accurately determine FHX in water and soil samples.

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