Nanobilim ve Teknoloji Araştırma ve Uygulama Merkezi Yayın Koleksiyonu

Bu koleksiyon için kalıcı URI

https://hdl.handle.net/20.500.12428/3702

Listeleniyor 1 - 20 / 80

Modification of halloysite clay nanotubes with various alkyl halides, and their characterization, blood compatibility, biocompatibility, and genotoxicity
(Elsevier Ltd, 2021) Can, Mehmet; Demirci, Şahin; Yıldırım, Yıldız; Çakır Çoban, Canan; Türk, Mustafa; Şahiner, Nurettin
Halloysite nanotubes (HNTs) clay were modified with alkyl halides, bromoethane (BrE), bromodecane (BrD), and bromooctadecane (BrOD), respectively. The FT-IR spectra of modified HNTs demonstrated an increase in the intensity of aliphatic –CH2 peaks at 2920 and 2850 cm−1 proportional to the number of C atoms in the modifying agent confirming the success of chemical modification with corresponding alkyl halides. Surface charge of NaOH treated HNTs, −65.7 ± 5.1 mV was increased to −37.1 ± 2.4, −40.6 ± 5.3, and −44.7 ± 1.9 mV, respectively upon chemical modification with BrE, BrD, and BrOD. The Surface area of the HNT clays, 43.2 ± 1.3 m2/g was also increased to 59.8 ± 2.7, 56.9 ± 2.1, and 47.9 ± 1.7 m2/g for BrE, BrD, and BrOD modified HNT clays, respectively. Base-activated HNT clays at 1 mg/mL concentration found to be nonhemolytic with 3.5 ± 1.2% hemolysis ratio, whereas HNT-BrOD clays were slightly exceeded hemolytic safety level with 6.6 ± 0.2% hemolysis induction. Base-activated HNT and HNT-BrOD clays were found to show antithrombogenic character with more than 100% blood clotting indexes,107.6 ± 1.8, and 106.5 ± 1.9%, respectively. Cytotoxicity studies of HNTs on L929 fibroblast cells revealed that HNTs in 12.5–200 μg/mL concentration range were shown dose-dependent cell viability, and above 50% cell viability was maintained at 200 μg/mL in all forms of HNT based clays administered.
Poly(vinyl amine) microparticles derived from N-Vinylformamide and their versatile use
(Springer Science and Business Media Deutschland GmbH, 2022) Demirci, Şahin; Sutekin, S. Duygu; Kurt, Saliha B.; Güven, Olgun; Şahiner, Nurettin
Cationic polymers with primary amine groups that can easily be functionalized or coupled with substrates by complexation or hydrogen bonding are especially advantageous in preparing particles for biomedical applications. Poly(vinyl amine) (PVAm) is a cationic polyelectrolyte containing the highest number of primary amine groups among any other polymers. Here, we introduce a general method in synthesizing PVAm microparticles via a surfactant-free water-in-oil emulsion technique using cyclohexane as the oil phase and aqueous PVAm solution as the dispersed phase. PVAm particles were prepared to employ two different bifunctional chemical crosslinkers, divinyl sulfone (DVS) and poly(ethylene glycol) diglycidyl ether (PEGGE). The prepared particles were further treated with HCl to protonate the amine groups of PVAm within particles. The effect of crosslinker types and pH on the hydrolytic degradation of PVAm particles were also investigated at three different solution pHs, 5.4, 7.4, and 9, to simulate the skin, blood, and intestinal pH environments, respectively. The blood compatibility of the PVAm particles was evaluated by in vitro hemolysis and blood clotting assays. Furthermore, antifungal and antibacterial efficacy of PVAm-based particles and their protonated forms were tested against C. albicans yeast and E. coli, S. aureus, B. subtilis, and P. aeruginosa bacterial strains.
Phosphazene-based covalent organic polymers as metal-free catalysts with improved H2 generation from NaBH4 in methanol with superior catalytic activity and re-generation ability (vol 12, 112066, 2024)
(Elsevier Sci Ltd, 2024) Demirci, Şahin; Yıldız, Mustafa; Şahiner, Nurettin
Effects of size, structure, charge, and porosity of hydrogel-metal composite catalyst systems on hydrogen generation from the hydrolysis of NaBH4
(Amer Chemical Soc, 2013) Şahiner, Nurettin; Seven, Fahriye; Turhan, Tuğce; Karacan, Elif; Cağlar, Aysel
Thiourea-Isocyanate-Based Covalent Organic Frameworks with Tunable Surface Charge and Surface Area for Methylene Blue and Methyl Orange Removal from Aqueous Media
(Mdpi, 2022) Sağbaş Suner, Selin; Demirci, Şahin; Sutekin, Duygu S.; Yılmaz, Selehattin; Şahiner, Nurettin
A thiourea hexamethylene diisocyanate covalent organic framework (TH COF) was synthesized by adjusting the surface charge and surface area. The surface charge value of TH COF, -3.8 +/- 0.5 mV, can be changed to -29.1 +/- 0.4 mV by treatment with NaOH (dp-TH) and 17.1 +/- 1.0 mV by treatment with HCl (p-TH). Additionally, the surface area of TH COF was 39.3 m(2)/g, whereas the surface area of dp-TH COF and p-TH COF structures were measured as 41.4 m(2)/g and 42.5 m(2)/g, respectively. However, the COF structure had a better adsorption capability with acid and base treatments, e.g., dp-TH COF absorbed 5.5 +/- 0.3 mg/g methylene blue (MB) dye, and p-TH COF absorbed 25.9 +/- 1.4 mg/g methyl orange (MO) dye from 100 mL 25 ppm aqueous dye solutions, thereby increasing the MB and MO absorption amounts of the TH COF structure. Furthermore, by calculating the distribution, selectivity, and relative selectivity coefficients, the absorption capacity order was determined as dp-TH > TH > p-TH COFs for the MB dye, whereas it was p-TH > TH > dp-TH COFs for the MO dye. Finally, the reusability of dp-TH COF for MB absorption and p-TH COF for MO absorption were investigated. After five repeated uses, dp-TH COF retained 64.6 +/- 3.7% of its absorption ability, whereas p-TH COF preserved 79.7 +/- 3.2% of its absorption ability relative to the initial absorption amount.
Porous and modified HA particles as potential drug delivery systems
(Elsevier Science Bv, 2012) Şahiner, Nurettin; Sılan, Coşkun; Sağbaş, Selin; Ilgın, Pınar; Bütün, Sultan; Erduğan, Hüseyin; Ayyala, Ramesh S.
Composite silica-hyaluronic acid (Si-HA) micro particles were synthesized, employing tetraethyl orthosilicate (TEOS) in the presence of linear HA and a crosslinker, divinyl sulfone (DVS) via a water-in-oil microemulsion polymerization technique. Porous HA (PHA) hydrogel particles were generated after removal of silica particles upon treatment of HA composites with hydrofluoric acid (FIF). Furthermore, HA particles were quaternized (QHA) by chemical modification using 3-chloro-2-hydroxypropyl trimethyl ammonium chloride as a quarternization agent. The size of HA based particles were ranged between 1.26 and 2.95 mu m. The PHA particles have a surface area of 2.7 m(2)/g confirmed by the surface area measurements. Modified HA particles were used in the absorption and release studies of two model drugs in PBS, trimethoprim (TMP) and sodium diclofenac (SDF) which are acidic and basic in nature, respectively. The ability to control the size, charge and porosity of the HA particles which showed almost linear drug release profiles. (C) 2012 Elsevier Inc. All rights reserved.
Poly(vinyl phosphonic acid) nanogels with tailored properties and their use for biomedical and environmental applications
(Pergamon-Elsevier Science Ltd, 2016) Bütün Şengel, Sultan; Şahiner, Nurettin
Poly vinyl phosphonic acid (p(VPA)) hydrogel nanoparticles (nanogels) were prepared using VPA as monomer via microemulsion polymerization employing cetyl trimethylammonium bromide (CTAB) as a cationic surfactant. The nanogels were rendered magnetic field responsive by inclusion of silica-coated Fe3O4 nanoparticles during micro emulsion polymerization. Moreover, a porous nanogel was prepared by using triethoxyvinylsilane as co-monomer in microemulsion polymerization and removing the silica by HF treatment after polymerization. The synthesized nanogels were demonstrated as drug delivery devices in biomedical applications with targetable ability by using Zuclopenthixol (ZP) and phenazopyridine hydrochloride (PP) as model drugs. The ZP and PP loading and release amounts were evaluated via UV-Vis spectrometer (as a function of time at 324 nm and 426 nm, respectively) at different pHs such as 1.5, 7.4 and 9.0. Moreover, p(VPA) nanogels were shown to be very useful in environmental applications as absorbents for the removal of organic contaminants such as 4-nitrophenol (4 -NP), 1,1'-Dimethyl-4,4'-bipyridinium dichloride (Paraquat, PQ, Methylene Blue (MB) and Rhodamine 6G (R-6G) from aqueous media. (C) 2016 Elsevier Ltd. All rights reserved.
Modified biofunctional p(tannic acid) microgels and their antimicrobial activity
(Elsevier Science Bv, 2015) Sağbaş, Selin; Aktaş, Nahit; Şahiner, Nurettin
Crosslinked poly tannic acid) micro particles, p(TA), were synthesized using trimethylolpropane triglycidyl ether (TMPGDE) as crosslinker in a single step with high yield (73 perpendicular to 6%). The obtained p(TA) microgels possessed negative zeta potential, -27 mV, and the surface charge can be tuned by chemical modification using various modifying agents, such as 3-chloro-2-hydroxypropyl ammonium chloride (CHPACl) and chloro sulfonic acid (CSA) to generate microgels with different zeta potentials, e.g., -18 mV and -36 mV, respectively. Modified p(TA) microgels are found to be thermally less stable than bare p(TA) particles. Additionally, upon chemical modification of p(TA) particles, the antioxidant capacity of the p(TA) microgels decreased confirming the utilization of some of the phenolic groups, the main functional groups responsible for the antioxidant property of TA moieties. Moreover, the antimicrobial properties increased approximately four fold against three common bacterial strains; Escherichia coli ATCC 8739, Staphylococcus aureus ATCC 6538, and Bacillus subtilis ATCC 6633. P(TA) microgels as TA molecules have a natural capability to reduce metal ions, allowing in situ reduction of absorbed Ag and Cu ions to the corresponding metal nanoparticles within the p(TA) microgel network. The composite p(TA)-M (M:Ag or Cu) nanoparticle demonstrated superior antimicrobial activity against the mentioned bacteria compared to the bare p(TA) microgels. Moreover, bare and modified p(TA) microgels are shown to be drug carrier materials by loading three model drugs, phenylephrine HCl (PHE), trimethoprim (TMP), and naproxen (NP), and releasing them in phosphate buffer saline PBS (pH 7.4) at 37.5 degrees C. (C) 2015 Elsevier B.V. All rights reserved.
Metal nanoparticle preparation within modifiable p(4-VP) microgels and their use in hydrogen production from NaBH4 hydrolysis
(Pergamon-Elsevier Science Ltd, 2013) Şahiner, Nurettin; Yaşar, Alper O.
Composite poly(4-vinyl pyridine)-silica (p(4-VP)-Si) nanoparticles were synthesized, employing trimethoxy vinyl silane (TMVS) as silica forming agent using ethylene glycol dimethacrylate (EGDMA) as the cross-linker, and ammonium persulfate (APS) as the initiator in an oil-in-water micro emulsion system. Porous p(4-VP) nanoparticles were generated from p(4-VP)-Si by treatment with hydrofluoric acid (HF). The size of p(4-VP)-based particles ranged between 300 and 500 nm. The porous p(4-VP) particles have a surface area of 42.26 m(2)/g. We also report preparation of various metal nanoparticles, such as Co and Ni, inside bare p(4-VP), p(4-VP)-Si and porous p(4-VP) nanoparticles by absorption from the corresponding metal ions aqueous solution and then reduction with NaBH4. Atomic Absorption Spectroscopy (AAS) was used to determine the metal particle content of the p(4-VP)-based nanoparticles. The hydrogen production rate of Co-containing p(4-VP) was found to be superior to Ni-containing p(4-VP) under the same conditions. Cobalt-containing p(4-VP)-Si and porous p(4-VP) microgel composites can generate hydrogen faster than Co-containing p(4-VP). Moreover, p(4-VP)-based microgels showed seven fold hydrogen production rate, and almost five fold turn over frequency (TOF) than p(AMPS) microgels in terms of catalytic performances reported earlier. Copyright (C) 2013, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.
Various amine functionalized halloysite nanotube as efficient metal free catalysts for H2 generation from sodium borohydride methanolysis
(Elsevier Science Bv, 2017) Şahiner, Nurettin; Bütün Şengel, Sultan
In this work, naturally available clay, halloysite (Hal) nanotube was modified systematically with various types and number of amine groups containing modifying agents and used as catalyst in the methanolysis of sodium borohydride (NaBH4) for hydrogen (H-2) production. The modifying agents such as ethylenediamine (EDA), diethylenetriamine (DETA), triethylenetetramine (TETA), and tris(2-aminoethyl)amine (TAEA), and polyethyleneimine (PEI) were used in Hal nanotube modification followed by protonation with HCl treatments. Various parameters affecting the H-2 production rate such as the types of modification agents and/or catalyst types, NaBH4 amount, and the reaction temperature were investigated. The methanolysis of NaBH4 catalyzed by PEI modified and protonated Hal nanotube (H-PEI(750.000)-Hal nanotube) was found to follow first order reaction kinetic with respect to NaBH4 concentration. Interestingly, superior catalytic performances in comparison to the literature for the similar studies were obtained with 16.44 kJ/mol, 14.05 kJ/mol, and 196.46 J/mol.K of activation energy, enthalpy and entropy, respectively for NaBH4 methanolysis catalyzed by H-PEI(750.000)-Hal nanotubes. The hydrogen generation rate of 2218 mL/min.g that is comparable to the most of metal nanoparticle catalysts for H-PEI(750.000)-Hal nanotube catalyst was obtained.
Macroporous cryogel metal nanoparticle composites for H2 generation from NaBH4 hydrolysis in seawater
(Elsevier Science Bv, 2015) Şahiner, Nurettin; Yıldız, Sema; Şahiner, Mehtap; Issa, Zuheir A.; Al-Lohedan, Hamad
Poly( 2-hydroxy ethyl methacrylate) p(HEMA), poly( acrylic acid) p(AAc), poly(3-sulfopropyl methacrylate) p(SPM), and poly(4-vinylpyridine) p(4-VP) cryogels from various monomers containing functional groups such as COOH, SO3H, and OH, and) N monomer were synthesized under cryogenic conditions via free radical polymerization technique. The synthesized cryogels were used as templates for metal nanoparticle synthesis using Co and Ni, and the prepared composite cryogels were utilized in hydrogen (H-2) generation from the hydrolysis reaction of NaBH4. It was found that the hydrolysis reaction of NaBH4 in seawater is much faster than in DI water when using the p(SPM)-Co catalyst system. Parameters such as water and metal types for different cryogels, concentration of NaBH4, amount of metal catalyst, and temperature were investigated. The hydrogen generation rate (HGR) and turnover frequency (TOF) values were also investigated for temperature dependency. It was found that as the temperature increased from 30 to 70 degrees C, the HGR and TOF increased from 1288.0 +/- 61.2 (ml H-2) (g of metal min)(-1) and 3.1 +/- 0.1 mol H-2 (mol metal min)(-1) to 7707.8 +/- 179.4 (ml H-2) (g of metal min)(-1), and 16.1 +/- 0.4 mol H-2 (mol metal min)(-1), respectively. The activation energy, enthalpy, and entropy were 31.1 kJ (mol K)(-1), 27.7 kJ (mol K)(-1), and 196.4J (molK)(-1), respectively, for NaBH4 hydrolysis catalyzed in seawater by p(SPM)-Co composite system. (C) 2015 Elsevier B.V. All rights reserved.
Metal-free pyridinium-based polymeric ionic liquids as catalyst for H2 generation from NaBH4
(Pergamon-Elsevier Science Ltd, 2017) Şahiner, Nurettin; Yaşar, Alper O.; Aktaş, Nahit
Monodispersed poly(2-vinyl pyridine) (p(2-VP)) polymeric particles were synthesized with a self emulsion polymerization (SEP) technique. Polymeric ionic liquid (PIL) particles such as poly(2-vinyl pyridine)-ethane (p(2-VP)C-++(2)), poly(2-vinyl pyridine)-butane (p(2-VP)C-++(4)), and poly(2-vinyl pyridine)-hexane (p(2-VP) C-++(6)) particles were then prepared from monodispersed p(2-VP) particles by modifying with 1,2-dibromobutane (DBE) 1,4-dibromobutane (DBB) and 1,6-dibromobutane (DBH), respectively. The hydrodynamic diameter of the prepared particles was found be in the range of 350 -400 nm, and the zeta potential of p(2-VP)C-++(n) (n: 2, 4 and 6) particles were found to be in the range of 26-28 my. The prepared PIL particles (p(2-VP)C-++(6) etc.) were shown to be very effective catalysts in H-2 generation by methanolysis of NaBH4. Various parameters, such as the effect of modifying agents on PIL particle, the amount of PIL particles, the amount of NaBH4 and temperature, affecting the H-2 production rate were investigated. Hydrogen generation rate (HGR) was calculated as 5433 +/- 141 mL H-2 g(-1) min(-1) for 50 mg p(2-VP)C-++(6) particles in the methanolysis of 500 mM NaBH4. The activation energy (Ea) of methanolysis of NaBH4 catalyzed by p(2-VP)C-++(6) particles was calculated as 20.84 +/- 0.76 kJ mol(-1), which is much lower than similar studies reported in the literature. (C) 2016 Elsevier Ltd. All rights reserved.
H2 generation from NaBH4 methanolysis via magnetic field sensitive ionic liquid coated silica particles as catalyst
(Elsevier, 2017) Şahiner, Nurettin; Yaşar, Alper O.; Aktaş, Nahit
Upon the preparation of magnetic (Fe3O4) nanoparticles (NPs), they were coated with amino-functionalized silica (SiO2@NH2) via the modified Stber method. Siv coated Fe3O4 (Fe3O4@SiO2) particles and SiO2@NH2 coated Fe3O4 (Fe3O4@SiO2@NH2) particles were turned into ionic liquid (IL) colloids as Fe3O4@SiO2@NH3+Cl-, Fe3O4@SiO2@NH3+NO3- and Fe3O4@SiO2@NH3+HSO4- by the treatment of Fe3O4@SiO2@NH2 with hydrochloric acid (HCl), nitric acid (HNO3) and sulfuric acid (H2SO4), respectively. The size of the prepared silica-based particles was approximately 500 nm by SEM images, and the zeta potential values varying between -59 and +26 mV. The catalytic activity performances of these silica-based particles as catalysts were investigated for H-2 generation from methanolysis of NaBH4 in terms of the types of particles, reusability, recyclability, the concentration of NaBH4, and the reaction temperature. Amongst the prepared IL colloids, Fe3O4@SiO2@NH3+Cl- particles were found to be the most effective catalysts for the methanolysis reaction of NaBH4. The maximum Hydrogen Generation Rate (HGR) value of 13188 +/- 196 mL H-2 g(-1) min(-1) was attained at 500mM NaBH4 by using 50 mg Fe3O4@SiO2@NH3+Cl- as catalyst at 25 degrees C. Additionally, turn over frequency (TOF) value was calculated as 43.1 +/- 3.1 H-2 mol (mol of N.min)(-1) for Fe3O4@SiO2@NH3+Cl- under the same reaction conditions. Moreover, activation energy (Ea) values for the methanolysis of NaBH4 using Fe3O4@SiO2@NH3+Cl- particles as catalyst were found as 32.5 +/- 0.5, 39.9 +/- 0.3 and 24.4 +/- 0.7 kJ mol(-1) in the temperature range of -15-45, -30-0 and 15-45 degrees C, respectively, that are comparable and even better than for most of the metal nanoparticle catalysts used in NaBH4 methanolysis reactions.
Metal ion-imprinted hydrogel with magnetic properties and enhanced catalytic performances in hydrolysis of NaBH4 and NH3BH3
(Pergamon-Elsevier Science Ltd, 2013) Seven, Fahriye; Şahiner, Nurettin
Metal ion-imprinted (IIH) poly(2-acrylamido-2-methyl-1-propansulfonic acid) p(AMPS) hydrogels were prepared by using a free-radical polymerization technique in the presence of metal ions (M = Co (II) or Ni (II)). Using metal ion-imprinted hydrogels (IIHs), and non-metal ion-imprinted (NIH) hydrogels as template for the preparation of Co and Ni catalyst systems, the hydrolysis kinetics of NaBH4 and NH3BH3 were investigated. The catalytic performances of IIHs and NIHs were compared in terms of effect on hydrolysis kinetics of NaBH4 and NH3BH3. To increase the amounts of Co nanoparticles within p(AMPS) hydrogel for better catalytic activity, several reloading and reduction cycles of Co (II) ions were carried out, and the prepared p(AMPS)-Co composite catalyst systems were tested for hydrogen generation from the hydrolysis of NaBH4. As the number of Co (II) loading and reduction cycles increased, the amount of metal catalysts and the catalytic performance of composites increased. Kinetics studies were carried out on three times Co (II) ion loaded and reduced p(AMPS)-Co catalyst systems (containing 36.80 mg/g Co). Three time Co (II)-loaded catalyst systems provided very fast hydrolysis kinetics for NaBH4, and provided magnetic field responsive behavior. The hydrolysis reaction of NaBH4 was completed within 50 s, under the described conditions at 60 degrees C. It was demonstrated that the synthesized catalyst systems can be used ten times repetitively without significant loss of catalytic activity (86.5%). Copyright (C) 2013, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.
Enhanced catalytic performance in hydrogen generation from NaBH4 hydrolysis by super porous cryogel supported Co and Ni catalysts
(Elsevier, 2014) Seven, Fahriye; Şahiner, Nurettin
The neutral 3-D superporous cryogel is prepared from a poly(acrylamide) (p(AAm)) hydrogel network modified with an amidoximation reaction to induce chemical changes to produce superporous amidoximated-p(AAm) (amid-p(AAm)) cryogel. The newly-formed strongly ionizable matrices can readily absorb metal ions such as Co(II) and Ni(II) enabling in situ preparation of corresponding metal nanoparticles by NaBH4 treatments. It is found that the superporous amid-p(AAm)-Co cryogel composite is very effective as a catalyst for H-2 generation from hydrolysis of NaBH4 in alkaline medium. Furthermore, it is demonstrated that the metal ion loading capacity and catalytic activity of superporous amid-p(AAm)-Co cryogel composites increased with 2nd and 3rd Co(II) ion loading and reduction cycles. The hydrogen generation rate of p(AAm)-Co metal composites is increased to 1926.3 +/- 1.1 from 1130.2 +/- 1.5 (mL H-2) (min)(-1) (g of M)(-1). The effect of various parameters such as porosity, metal type, the number of reloading and reduction cycles of the metal ion, and temperature are investigated for the hydrolysis of NaBH4. The kinetic parameters such as energy, enthalpy and entropy are determined as Ea = 39.7 +/- 0.2 kJ mol(-1), Delta H = 37.2 +/- 0.1 kJ mol(-1) and Delta S = -171.9 +/- 0.5 J mol(-1) K-1, respectively. (C) 2014 Elsevier B.V. All rights reserved.
P(4-VP) based nanoparticles and composites with dual action as antimicrobial materials
(Elsevier Science Bv, 2010) Özay, Özgür; Alper Akçalı; Tatman Otkun, Müşerref; Sılan, Coşkun; Aktaş, Nahit; Şahiner, Nurettin
Polymeric 4-VP (p(4-VP)) particles were synthesized in an oil-in-water microemulsion system using various amounts of ethylene glycol dimethacrylate (EGDMA) as crosslinker. The prepared p(4-VP) particles were chemically modified to obtain positively charged particles as polyelectrolytes. Furthermore, these p(4-VP) particles were used for in situ Ag and Cu metal nanoparticle syntheses to provide dual action with an additional advantage as bactericidal particles. The synthesized p(4-VP) particles with positive charges and metal constituents were tested for potential antibacterial action against various bacteria such as Staphylococcus aureus ATCC6538, Pseduomonas aeruginosa ATCC9027, Bacillus subtilis ATCC6633, Escherichia coli ATCC8739. It was found that p(4-VP) particles, especially the positively charged forms had potential as antibacterial materials. The synthesized particle dimensions were characterized with TEM, and DLS measurements. Chemical modification of the particles was confirmed by FT-IR spectroscopy and zeta potential measurements, and the metal nanoparticle contents were determined with thermogravimetric (TGA) studies. (C) 2010 Elsevier B.V. All rights reserved.
Light-Activated Modified Arginine Carbon Dots as Antibacterial Particles
(Mdpi, 2022) Sağbaş Suner, Selin; Şahiner, Mehtap; Yılmaz, Aynur Sanem; Ayyala, Ramesh S.; Şahiner, Nurettin
Nitrogen-doped arginine carbon dots (Arg CDs) as light-sensitive antibacterial agents were prepared by using citric acid as the carbon source and arginine amino acid as the nitrogen source via a microwave-assisted synthesis method. Dynamic light scattering (DLS) measurements and TEM images revealed that the Arg CDs were in the 1-10 nm size range with a graphitic structure. To improve their antibacterial capability, the Arg CDs were modified with ethyleneimine (EDA), pentaethylenehexamine (PEHA), and polyethyleneimine (PEI) as different amine sources, and the zeta potential value of +2.8 +/- 0.6 mV for Arg CDs was increased to +34.4 +/- 4.1 mV for PEI-modified Arg CDs. The fluorescence intensity of the Arg CDs was significantly enhanced after the modification with EDA, and the highest antibacterial effect was observed for the PEI-modified Arg CDs. Furthermore, the photodynamic antibacterial capacity of bare and EDA-modified Arg CDs was determined upon light exposure to show their light-induced antibacterial effects. Photoexcited (315-400 nm, UVA, 300 W), EDA-modified Arg CDs at 5 mg/mL concentration were found to inhibit about 49 +/- 7% of pathogenic bacteria, e.g., Escherichia coli, with 5 min of light exposure. Furthermore, the biocompatibilities of the bare and modified Arg CDs were also investigated with blood compatibility tests via hemolysis and blood clotting assays and cytotoxicity analysis on L929 fibroblast cells.
Degradable and Non-Degradable Chondroitin Sulfate Particles with the Controlled Antibiotic Release for Bacterial Infections
(Mdpi, 2022) Sağbaş Suner, Selin; Şahiner, Mehtap; Ayyala, Ramesh S.; Şahiner, Nurettin
Non-degradable, slightly degradable, and completely degradable micro/nanoparticles derived from chondroitin sulfate (CS) were synthesized through crosslinking reactions at 50%, 40%, and 20% mole ratios, respectively. The CS particles with a 20% crosslinking ratio show total degradation within 48 h, whereas 50% CS particles were highly stable for up to 240 h with only 7.0 +/- 2.8% weight loss in physiological conditions (pH 7.4, 37 degrees C). Tobramycin and amikacin antibiotics were encapsulated into non-degradable CS particles with high loading at 250 g/mg for the treatment of corneal bacterial ulcers. The highest release capacity of 92 +/- 2% was obtained for CS-Amikacin particles with sustainable and long-term release profiles. The antibacterial effects of CS particles loaded with 2.5 mg of antibiotic continued to render a prolonged release time of 240 h with 24 +/- 2 mm inhibition zones against Pseudomonas aeruginosa. Furthermore, as a carrier, CS particles significantly improved the compatibility of the antibiotics even at high particle concentrations of 1000 g/mL with a minimum of 71 +/- 7% fibroblast cell viability. In summary, the sustainable delivery of antibiotics and long-term treatment of bacterial keratitis were shown to be afforded by the design of tunable degradation ability of CS particles with improved biocompatibility for the encapsulated drugs.
P(HMA-co-ATU) hydrogel synthesis via gamma radiation and its use for in situ metal nanoparticle preparation and as catalyst in 4-nitrophenol reduction
(Pergamon-Elsevier Science Ltd, 2022) Güven, Olgun; Demirci, Şahin; Sütekin, S. Duygu; Ari, Betül; Şahiner, Nurettin
Hydrogels with reactive thiourea functional groups were prepared by radiation-induced crosslinking of N-(Hydroxymethyl) acrylamide (HMA) and N-allyl thiourea (ATU) at different ATU content and irradiation doses. P (HMA-co-ATU) hydrogels were then utilized as template for in situ metal nanoparticle (MNP) preparation by the reduction of Ni2+, Co2+, and Cu(2+)ions within the hydrogel matrix using sodium borohydride (NaBH4) as reducing agent. These MNP@p(HMA-co-ATU) hydrogel composites (MNP = Co, Ni, and Cu) were further used as catalysts in the reduction reaction of 4-nitrophenol (4-NP) to 4-aminophenol (AP). Various parameters such as the effect of ATU content, the total dose used in the hydrogel preparation, MNPs type, and temperature on the catalytic activity of hydrogel composites were investigated. The activation energy, enthalpy, and entropy of Ni@p(HMA-co-ATU) hydrogels for the reduction reaction of 4-NP to 4-AP were calculated as 42.5 kJ mol-1, 38.9 kJ mol(-1), and-187.3 J mol(-1) K-1, respectively.
Hydrogel-Biochar composites for effective organic contaminant removal from aqueous media
(Elsevier, 2011) Karakoyun, Necdet; Kubilay, Şenol; Aktaş, Nahit; Turhan, Ömer; Kasımoğlu, Murat; Yılmaz, Selahattin; Şahiner, Nurettin
In this study, p(acrylamide)-chicken biochar (p(AAm)-CB), p(acrylamide)-wood biochar (p(AAm)-WB), and p(acrylamide)-tire biochar (p(AAm)-TB) hydrogel composites were prepared using acrylamide (AAm) as monomer with the corresponding biochars, with N,N'-methylenebisacrylamide (MBA) as crosslinker and ammonium persulfate (APS) as initiator. P(AAm)-CB, p(AAm)-WB, and p(AAm)-TB were used as adsorbents to remove phenol from aqueous environments. The synthesized p(AAm)-CB, p(AAm)-WB, p(AAm)-TB and p(AAm) hydrogel composites had swelling values of 1112, 1045, 847, and 623%, respectively in distilled water. The prepared hydrogel biochar material compositions were examined using an elemental analyzer. Absorption of phenol into p(AAm)-WB was studied at different pHs to determine the optimum pH for maximum removal of phenol. The ionic strength of the medium was varied between 0.01 and 1 mol L-1 to determine the effect of salt (NaCl) on the absorption characteristics and it was found that the absorption of phenol increased with a decrease in the amount of salt. Langmuir and Freundlich isotherms were applied to describe the absorption characteristics and the Langmuir isotherm describes the absorption phenomena in this study much better than the Freundlich isotherm. Pseudo-first-order and pseudo-second-order kinetic studies were also applied to determine absorption characteristic. (C) 2011 Elsevier B.V. All rights reserved.

Güncel Gönderiler