Akdoğan, Yaşar
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Akdogan, Y.
Akdogan, Y
Akdogan, Yaşar
Akdogan, Yasar
Akdoğan, Y.
Akdoğan, Y
Akdogan, Y
Akdogan, Yaşar
Akdogan, Yasar
Akdoğan, Y.
Akdoğan, Y
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yasarakdogan@iyte.edu.tr
Main Affiliation
03.09. Department of Materials Science and Engineering
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Current Staff
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Sustainable Development Goals
1NO POVERTY
0
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2ZERO HUNGER
0
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3GOOD HEALTH AND WELL-BEING
4
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4QUALITY EDUCATION
0
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5GENDER EQUALITY
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6CLEAN WATER AND SANITATION
1
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7AFFORDABLE AND CLEAN ENERGY
3
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8DECENT WORK AND ECONOMIC GROWTH
1
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9INDUSTRY, INNOVATION AND INFRASTRUCTURE
6
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10REDUCED INEQUALITIES
0
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11SUSTAINABLE CITIES AND COMMUNITIES
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12RESPONSIBLE CONSUMPTION AND PRODUCTION
2
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13CLIMATE ACTION
2
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14LIFE BELOW WATER
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15LIFE ON LAND
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16PEACE, JUSTICE AND STRONG INSTITUTIONS
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Documents
35
Citations
860
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17
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Scholarly Output
40
Articles
20
Views / Downloads
50601/27969
Supervised MSc Theses
15
Supervised PhD Theses
4
WoS Citation Count
355
Scopus Citation Count
415
Patents
0
Projects
8
WoS Citations per Publication
8.88
Scopus Citations per Publication
10.38
Open Access Source
27
Supervised Theses
19
| Journal | Count |
|---|---|
| Materials Chemistry and Physics | 3 |
| ChemistrySelect | 2 |
| International Journal of Biological Macromolecules | 2 |
| Journal of Molecular Liquids | 2 |
| Physical Chemistry Chemical Physics | 2 |
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40 results
Scholarly Output Search Results
Now showing 1 - 10 of 40
Article Citation - WoS: 18Citation - Scopus: 20A Simple Desolvation Method for Production of Cationic Albumin Nanoparticles With Improved Drug Loading and Cell Uptake(Editions de Sante, 2020) Sözer, Sümeyra Çiğdem; Özmen Egesoy, Tuğçe; Başol, Merve; Çakan Akdoğan, Gülçin; Akdoğan, YaşarThe transport protein albumin has been used as a drug nanocarrier for a long time due to its versatility. Albumin is negatively charged at physiological conditions limiting its anionic drug loading capacity. However, loading of anionic drugs in the albumin nanoparticles (NPs), can be facilitated by albumin cationization. Here, we postulate a simple desolvation method for preparation of cationic albumin NPs with improved anionic drug loading. First, bovine serum albumin was cationized with ethylenediamine. Next, salicylic acid (SA) was added to the cationic bovine serum albumin (cBSA) solution prior to the desolvation. Among different desolvating agents tested, acetonitrile allowed the highest nanoparticle formation yield. The SEM analyses showed that the average size of cBSA NPs decreased from ~200 nm to ~100 nm upon SA loading. Moreover, the drug loading capacity of cBSA NPs was found to increase ~2 fold, and drug release was slower compared to BSA NPs. Finally, a significant increase in cellular uptake of cBSA NPs compared to that of native BSA NPs showed the potential for improved drug delivery. © 2020 Elsevier B.V.Article Citation - WoS: 66Citation - Scopus: 71Signature of an Aggregation-Prone Conformation of Tau(Nature Publishing Group, 2017) Eschmann, Neil A.; Georgieva, Elka R.; Ganguly, Pritam; Borbat, Peter P.; Rappaport, Maxime D.; Akdoğan, Yaşar; Freed, Jack H.; Shea, Joan-Emma; Han, SongiThe self-assembly of the microtubule associated tau protein into fibrillar cell inclusions is linked to a number of devastating neurodegenerative disorders collectively known as tauopathies. The mechanism by which tau self-assembles into pathological entities is a matter of much debate, largely due to the lack of direct experimental insights into the earliest stages of aggregation. We present pulsed double electron-electron resonance measurements of two key fibril-forming regions of tau, PHF6 and PHF6∗, in transient as aggregation happens. By monitoring the end-to-end distance distribution of these segments as a function of aggregation time, we show that the PHF6 (∗) regions dramatically extend to distances commensurate with extended β-strand structures within the earliest stages of aggregation, well before fibril formation. Combined with simulations, our experiments show that the extended β-strand conformational state of PHF6 (∗) is readily populated under aggregating conditions, constituting a defining signature of aggregation-prone tau, and as such, a possible target for therapeutic interventions.Doctoral Thesis Organik Çözücü ve Çapraz Bağlayıcı İçermeyen İlaç Taşıyıcı Nanomalzemelerin Sentezi ve Karakterizasyonu(2025) Sözer, Sümeyra Çiğdem; Akdoğan, YaşarSerum albümini, yüksek biyouyumluluğu ve taşıyıcı kapasitesi nedeniyle ilaç taşıyıcı sistemlerinde nanoparçacık (NP) üretmek için tercih edilmektedir. Desolvasyon ve emülsifikasyon gibi geleneksel albümin NP'leri hazırlama yöntemleri, genellikle suda çözünmeyen ilaç yüklemesini ve terapötik potansiyelini sınırlayan toksik organik çözücülere ve glutaraldehit gibi çapraz bağlayıcılara dayanır. Bu tez, yeşil kimyasal bir süreçle albümin-albümin polielektrolit kompleks nanoparçacıkları (PEC NP'leri) üreterek bu sınırlamaların üstesinden gelmeyi amaçlamıştır. İlk bölümde, farklı sulu çözünürlüklere sahip ilaçların (salisilik asit (yüksek), ibuprofen (düşük) ve klorambusil (hiç yok)) çözünürlük davranışları elektron paramanyetik rezonans (EPR) spektroskopisi kullanılarak incelenmiştir. Sonuçlar, albümin NP'lerinin hidrofobik ilaçları suda çözmede albümin proteininden önemli ölçüde daha etkili olduğunu göstermiştir. Ayrıca, ilaç salımı EPR ile NP pelet çözünmesinden doğrudan izlenebilmekte ve bu da geleneksel tekniklere göre bir avantaj sağlamaktadır. İkinci bölümde, albümin PEC NP'leri, çözücüler, çapraz bağlayıcılar veya özel ekipman olmadan katyonik ve anyonik albüminlerin elektrostatik etkileşimi ile sentezlenmiştir. Elde edilen albümin PEC NP'leri (110 nm, +37 mV), büyük ölçüde organik çözücülere ilaç kaybının önlenmesi nedeniyle, desolvasyon yöntemine kıyasla 17 kata kadar daha yüksek klorambusil yüklemesine olanak sağlamıştır. Klorambusil yüklü albümin PEC NP'leri ayrıca Huh-7 hücre canlılığını 24 saat içinde %44'e düşürmüştür. Üçüncü bölümde, albümin PEC hidrojel sistemlerine dönüştürülerek, sürekli salım ve lokal salım uygulamaları için potansiyel olarak uygulanabilirliğini göstermektedir. Genel olarak bu çalışma albümin PEC NP'lerini, yeşil kimya ile basit bir şekilde üreterek yüksek oranda ilaç yüklü nanotaşıyıcılar ve gelişmiş ilaç salım uygulamaları için uygun ve etkili bir strateji olduğu vurgulamaktadır.Master Thesis Investigation of Tribological Performance of B4c Reinforced Aluminium Matrix Composites(Izmir Institute of Technology, 2019) Serkir, Sevgi; Kandemir, Sinan; Akdoğan, YaşarAluminium, on account of its easy accessibility and superior metallic characteristics, has a wide variety of applications. Increasing demand on the use of aluminium in areas such as automobile, aviation and space industries which requires high performance has led to development of aluminium metal matrix composites. For this purpose, the ceramic reinforcing particles are mostly preferred to provide better mechanical and tribological properties than their conventional counterparts. In this study, aluminium metal matrix composite (AMC) reinforced with 5 wt.%, 10 wt.% and 15wt.% of B4C were fabricated using the powder metallurgy method. In order to obtain the optimum processing parameters necessary for efficient fabrication, several trials, at first place, were studied under different conditions by changing milling parameters such as milling time, milling medium, milling speed and process control agent, and sintering process parameters such as sintering time, sintering temperature. The production of composite powders was carried out using a planetary ball mill in a wet medium for 7 hours with 0.05 wt.% of stearic acid process control agent which helps to avoid contamination and cold welding of ductile Al particle. The milled powders were pressed at 314 MPa at RT and composite samples with a diameter of 30 mm and a height of 4 mm were obtained. The samples were sintered at 550, 575, 600 and 625ºC for one hour under argon atmosphere. The micro-structures of samples were analysed by scanning electron microscopy and the X-ray diffraction techniques. The wear behaviour of sintered composite samples with ball-on-disc dry wear tester and the mechanical behaviour of the samples with Vickers hardness test were investigated.Article Citation - WoS: 10Citation - Scopus: 12The Effect of Dopa Hydroxyl Groups on Wet Adhesion To Polystyrene Surface: an Experimental and Theoretical Study(Elsevier, 2020) Yıldız, Remziye; Özen, Sercan; Şahin, Hasan; Akdoğan, YaşarMussels wet adhesive performance has been arousing curiosity for a long time. It is found that 3,4-dihydroxyphenylalanine (DOPA) is responsible for adhesive properties of mussels. Despite a large body of research characterizing the interactions DOPA with hydrophilic surfaces, relatively few works have addressed the mechanism of interactions with hydrophobic surfaces. The benzene ring of DOPA is the main attributor to the adhesion on hydrophobic polystyrene (PS) surface. However, here we showed that two hydroxyl groups of catechol have also effects on wet adhesion. We studied wet adhesive properties of DOPA, tyrosine and phenylalanine functionalized PEG polymers, PEG-(N-Boc-L-DOPA)(4), PEG-(N-Boc-L-Tyrosine)(4), PEG-(N-Boc-L-Phenylalanine)(4), on spin labeled PS nanobeads (SL-PS) by electron paramagnetic resonance (EPR) spectroscopy. Surface coverage ratio of SL-PS upon additions of PEG-(N-Boc-L-DOPA)(4), PEG-(N-Boc-L-Tyrosine)(4) and PEG-(N-Boc-L-Phenylalanine)(4) showed that SL-PS was covered with 70%, 50% and 0%, respectively. This showed that spontaneous wet adhesion on PS increases with the number of amino acids hydroxyl groups. This is also supported with the density functional theory (DFT) energy calculations and ab-initio molecular dynamics (AIMD) simulations. In water, interactions between water molecules and hydroxyl groups on the catechol induce catechol adhesion via 7C-7C stacking between the catechol and double styrene rings which were already tilted out with water.Master Thesis Study of Drug Transportation by Esr Spectroscopy(Izmir Institute of Technology, 2018) Tatlıdil, Duygu; Akdoğan, Yaşar; Emrullahoğlu, MustafaThe ability to track drug binding and release makes electron spin resonance (ESR) spectroscopy well suited for drug delivery studies. Using the continuous wave cw ESR technique to extract information about the dynamics of the spin labeled drugs we can simultaneously determine the bound and unbound drugs. In this study, ESR technique was used to detect the binding and release of spinlabeled salicylic acid (SLSA) to and from bovine serum albumin (BSA), and to detect different binding interactions between them. We have labeled salicylic acid with stable nitroxide-based tempo radicals to monitor the BSA bound and unbound conditions of the drug. Studying with the different concentrations of SLSA-BSA binding showed that the drug-protein stoichiometry increases significantly in the physiological range of BSA concentration. Also, during the release of SLSA from BSA, there is an unchanging balance between the bound and unbound SLSA. In order to study various drug binding interactions, SL-benzoic acid, SL-phenol, SL-benzene, SL-cyclohexane, SL-hexane and SL-methyl were prepared. We showed that the main conjugation in the binding of these drugs to BSA is hydrophobic interaction. In addition, cationic BSA (cBSA) was prepared to investigate the effect of electrostatic interaction on drug binding. The SLSA loading capacity of cBSA is significantly higher than that of BSA, this result indicates the importance of electrostatic interactions for the drug binding. Finally, we examined the competitive binding behaviors of salicylic acid, ibuprofen and aspirin to BSA. Binding sites of SL-salicylic acid and SL-ibuprofen in BSA show 96% of similarities. In addition, our results showed that binding sites of SL-salicylic acid and SL-aspirin in BSA have 73% of similarities.These results demonstrate that cw ESR spectroscopy with the spin labeling technique is an effective technique for the determination of drug-protein interactions and stoichiometric analysis of drug binding.Master Thesis Obtaining Underwater Adhesive Materials and Characterization of Their Adhesive Properties To Different Surfaces by Esr Spectroscopy(Izmir Institute of Technology, 2016) Kırpat, İklima; Akdoğan, YaşarThis study describes the design, synthesis and spectral behavior of underwater adhesive materials which adhere to surfaces without any external force. The materials with wet adhesive properties have a wide application field from biomedical implantation and covering to antifouling materials. Mussel’s stickiness to rocks, ships, etc. inspite of strong waves in the sea inspires us to synthesize adhesives materials. Mussels attach to solid surfaces strongly using their threads and plaques. The complex fluid (mussel foot proteins, Mfps) secreted from mussels is solidified in the sea water and forms threads, each equipped with a distal adhesive plaque. Mfps have large amount of L-3,4-dihydroxyphenylalanine (DOPA) amino acid and this amino acid is responsible for adhesion of mussels to underwater surfaces. The presence of stable hydration layers around both the adhesive materials and surface results in strong hydration repulsive forces that undermine adhesion. So far, applied external forces were used to break through or disrupt the hydration layers which prevent adhesion. In this research branched PEG based polymers were modified with different amounts of DOPA in order to obtain underwater adhesive material. Their adhesive properties to spin labeled (SL) nanoparticles were tested without applying an external force by electron spin resonance (ESR) spectroscopy. As model surfaces we synthesized hydrophobic SL-polystyrene and hydrophilic SL-silica nanoparticles. ESR results showed that four arm DOPA modified PEG is able to adhere to SL-polystyrene but not to SL-silica. Moreover, adhesions of the polymers were tested by making hydrogels using iodate (IO3-) and iron (III) (Fe3+) ions. ESR results showed that hydrogels prepared from four arm DOPA modified PEG/IO3- mixture has better adhesive property to SL-polystyrene compare to hydrogels prepared from four arm DOPA modified PEG/Fe3+ mixture and adhesion of IO3- based gel form is better compared to molecule form.Article Citation - WoS: 33Citation - Scopus: 36Epr Studies of Intermolecular Interactions and Competitive Binding of Drugs in a Drug-Bsa Binding Model(Royal Society of Chemistry, 2016) Akdoğan, Yaşar; Emrullahoğlu, Mustafa; Tatlıdil, Diğdem; Üçüncü, Muhammed; Çakan Akdoğan, GülçinUnderstanding intermolecular interactions between drugs and proteins is very important in drug delivery studies. Here, we studied different binding interactions between salicylic acid and bovine serum albumin (BSA) using electron paramagnetic resonance (EPR) spectroscopy. Salicylic acid was labeled with a stable radical (spin label) in order to monitor its mobilized (free) or immobilized (bound to BSA) states. In addition to spin labeled salicylic acid (SL-salicylic acid), its derivatives including SL-benzoic acid, SL-phenol, SL-benzene, SL-cyclohexane and SL-hexane were synthesized to reveal the effects of various drug binding interactions. EPR results of these SL-molecules showed that hydrophobic interaction is the main driving force. Whereas each of the two functional groups (-COOH and -OH) on the benzene ring has a minute but detectable effect on the drug-protein complex formation. In order to investigate the effect of electrostatic interaction on drug binding, cationic BSA (cBSA) was synthesized, altering the negative net charge of BSA to positive. The salicylic acid loading capacity of cBSA is significantly higher compared to that of BSA, indicating the importance of electrostatic interaction in drug binding. Moreover, the competitive binding properties of salicylic acid, ibuprofen and aspirin to BSA were studied. The combined EPR results of SL-salicylic acid/ibuprofen and SL-ibuprofen/salicylic acid showed that ibuprofen is able to replace up to ∼83% of bound SL-salicylic acid, and salicylic acid can replace only ∼14% of the bound SL-ibuprofen. This indicates that ∼97% of all salicylic acid and ibuprofen binding sites are shared. On the other hand, aspirin replaces only ∼23% of bound SL-salicylic acid, and salicylic acid replaces ∼50% of bound SL-aspirin, indicating that ∼73% of all salicylic acid and aspirin binding sites are shared. These results show that EPR spectroscopy in combination with the spin labeling technique is a very powerful method to investigate drug binding dynamics in detail.Master Thesis Adhesion of Dopa Functionalized Gels To Spin Labeled Surfaces(Izmir Institute of Technology, 2017) Göksel, Yaman; Akdoğan, Yaşar; Emrullahoğlu, MustafaThis study investigates the force free adhesive properties of synthetic polymer in aqueous media using electron paramagnetic resonance (EPR) spectroscopy. Due to poor performance of commercial adhesives in wet environments, scientists are interested in different types of adhesives to overcome this difficulty. On this context, mussels attract attention because of their versatile properties to adhere different types of surfaces from rocks to ship hulls underwater. Adhesion occurs when mussel secretes mussel foot proteins (MFPs) in order to form threads and plaques. Seven types of MFPs are unique in plaque contains high amount of L-3,4-dihydroxyphenylalanine (DOPA) amino acid which is reputed to be responsible for adhesion. In this research, branched polyethylene glycol (PEG) based polymers functionalized with DOPA were synthesized and their force-free adhesive properties to hydrophobic polystyrene and hydrophilic silica nanobeads were investigated in solution. These nanobead surfaces were conjugated with spin label molecules to probe adhesion dynamics using EPR spectroscopy. In addition, gel forms of polymers obtained using NaIO4, FeCl3 and Cr2O7 were used as adhesive materials for EPR measurements. All of these adhesive materials showed adhesion to spin labeled polystyrene (SL-PS) surface. However, non-DOPA containing PEG showed no indication of adhesion thus, demonstrating the importance of DOPA in wet adhesion. In addition, EPR results showed that DOPA based PEG polymers were unable to adhere to spin labeled silica (SL-SiO2) surface. This behavior was attributed to hydration layers around silica nanobeads. These layers formed around hydrophilic SiO2 surface prevent interaction between nanobead surface and polymeric material.Article Citation - WoS: 14Citation - Scopus: 17Spectrophotometric Characterization of Plasticizer Migration in Poly(vinyl Chloride)-Based Artificial Leather(Elsevier Ltd., 2021) Akkuş Altındağ, İffet; Akdoğan, YaşarPlasticized polyvinyl chloride (PVC) is one of the most commonly used material in the manufacture of artificial leather because of its flexibility, high durability and low cost. While hundreds of plasticizers have been produced to obtain PVC films and artificial leathers, it is important to choose the correct plasticizer to produce the desired products. Therefore, here five non-phthalate type plasticizers with three levels (40 phr, 60 phr and 80 phr); trioctyl trimelliate (TOTM), tributyl trimelliate (TBTM), dioctyl terephthalate (DOTP), dioctyl adipate (DOA) and dioctyl succinate (BIO) were used to prepare plasticized PVC films. They were studied in terms of their compabilities with PVC polymer chains, and their effects on mechanical properties of PVC films. Although, linear plasticizers e.g. BIO and DOA have higher compabilities with PVC, a branched plasticizer e.g. TOTM showed higher mechanical properties. Moreover, a new spectrophotometric method for determination of plasticizer migration from PVC polymer matrix to the surface of artifical leather was developed. According to lightness change on the surface of PVC artifical leather before and after heat treatment at 70 °C, the migration rates of used plasticizers increase in this order: TOTM < TBTM < DOTP < BIO < DOA. © 2020 Elsevier B.V.