Browsing by Author "Sagbas, Selin"

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0d, 1d, 2d, and 3d Soft and Hard Templates for Catalysis
(Elsevier Science Bv, 2017) Butun, Sultan; Demirci, Sahin; Yasar, Alper O.; Sagbas, Selin; Aktas, Nahit; Sahiner, Nurettin
Biocompatible and Biodegradable Poly(Tannic Acid) Hydrogel With Antimicrobial and Antioxidant Properties
(Elsevier, 2016) Sahiner, Nurettin; Sagbas, Selin; Sahiner, Mehtap; Silan, Coskun; Aktas, Nahit; Turk, Mustafa
A novel resourceful bulk poly(Tannic Acid) (p(TA)) hydrogel was prepared by crosslinking TA molecules with an epoxy crosslinker, trimethylolpropane triglycidyl ether (TMPGDE), in an autoclave at 90 degrees C for 2 h. The obtained p(TA) hydrogels were in disk form and have highly porous morphology. The swelling characteristics of p(TA) hydrogels were investigated in wound healing pH conditions of pH 5.4, 7.4, and 9 at 37.5 degrees C, and the hydrogels showed good swelling and moisture content behavior. Especially, p(TA) hydrogels were found to be sensitive to pH 9 with 1669% maximum swelling. P(TA) hydrogels were completely degraded at pH 9 hydrolytically in 9 days. Total phenol contents and the effects of scavenging ABTS radicals of degraded p(TA) hydrogels at pH 5.4, 7.4, and 9 were evaluated and calculated in terms of gallic acid equivalent and trolox equivalent antioxidant capacity, respectively, and found to be very effective. Moreover, degraded p(TA) hydrogels display strong antimicrobial behavior against gram positive Staphylococcus aureus, Bacillus subtilis, gram negative Pseudomonas aeruginosa bacteria strains and Candida albicans fungus strain. The WST-1 results indicated that bulk p(TA) hydrogels have no cyctotoxicity to the L929 fibroblast cell line in vitro. (C) 2015 Elsevier B.V. All rights reserved.
Gum Arabic Microgels as Template for in Situ Metal-Sulfide Based Quantum Dots Preparation and Their Thermal, Spectroscopic, Optical, and Magnetic Characterization
(Springer, 2017) Farooq, Muhammad; Sagbas, Selin; Yildiz, Mustafa; Meral, Kadem; Siddiq, Mohammad; Aktas, Nahit; Sahiner, Nurettin
Here, gum arabic (GA) microgel in 5-50 mu m size range was used as a template for in situ quantum dot (QD) preparation. The in situ synthesis of metal sulfide quantum dots (QDs) such as CdS, PbS, CuS, ZnS, CoS, and MnS was accomplished by the absorption of the corresponding metal ions from aqueous solutions and then in situ precipitation with S2- treatments within GA microgels. Transmission electron microscopy (TEM) confirmed the existence of the evenly distributed QDs within GA microgel matrices for each of the prepared QDs. All the fabricated GA-QD composites have shown excellent semiconducting behaviors with relatively larger band gap values of 4.87 eV, 4.60 eV, 6.71 eV, 4.81 eV, 3.68 eV, 5.2 eV, and 4.0 eV for CdS, PbS, ZnS, CuS, CoS, MoS, and MnS, respectively. The results revealed that CdS and ZnS are found to be the most efficient florescence materials amongst the all QDs with 630 and 70 cd/cm(2) fluorescence intensities, respectively. Moreover, the magnetic susceptibility study suggests that Mn(IV), Co(III), and Mo(IV), have mononuclear octahedral geometries whereas Zn(II), Cd(II), and Pb(II) show binuclear geometries.
Inherently Antioxidant and Antimicrobial Tannic Acid Release From Poly(Tannic Acid) Nanoparticles With Controllable Degradability
(Elsevier, 2016) Sahiner, Nurettin; Sagbas, Selin; Aktas, Nahit; Silan, Coskun
From a natural polyphenol, Tannic acid (TA), poly(TA) nanoparticles were readily prepared using a single step approach with three different biocompatible crosslinkers; trimethylolpropane triglycidyl ether (TMPGDE), poly(ethylene glycol) diglycidyl ether (PEGGE), and trisodium trimetaphosphate (STMP). P(TA) particles were obtained with controllable diameters between 400 to 800 nm with -25 mV surface charge. The effect of synthesis conditions, such as the emulsion medium, pH values of TA solution, and the type of crosslinker, on the shape, size, dispersity, yield, and degradability of poly(Tannic Acid) (p(TA)) nanoparticles was systematically investigated. The hydrolytic degradation amount in physiological pH conditions of 5.4, 7.4, and 9.0 at 37.5 degrees C were found to be in the order TMPGDE < PEGGE < STMP. Furthermore, the degradation amounts of TA from p(TA) nanoparticles can be controlled by the appropriate choice of crosslinker, and the pH of releasing media. The highest TA release, 600 mg/g, was obtained for TMPGDE-crosslinked p(TA) particles in intestinal pH conditions (pH 9) over 3 days; whereas, a slow and linear TA release profile over almost 30 days was obtained by using PEGGE-crosslinked p(TA) in body fluid pH conditions (pH 7.4). The total phenol content of p(TA) particles was calculated as 70 +/- 1 mu g mL(-1) for 170 mu g mL(-1) p(TA), and the trolox equivalent antioxidant capacity was found to be 2027 +/- 104 mM trolox equivalent g(-1). Moreover, p(TA) nanoparticles demonstrated strong antimicrobial effects against common bacterial strains. More interestingly, with a higher concentration of p(TA) particles, higher blood clotting indices were obtained. (C) 2016 Elsevier B.V. All rights reserved.
Modified Biofunctional P(Tannic Acid) Microgels and Their Antimicrobial Activity
(Elsevier Science Bv, 2015) Sagbas, Selin; Aktas, Nahit; Sahiner, 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.
Natural P(Ta) Hydrogel and Microgel Networks for Diverse Potential Biomedical Uses
(Amer Chemical Soc, 2015) Sahiner, Nurettin; Sagbas, Selin; Sahiner, Mehtap; Aktas, Nahit
Preparation and Characterization of Monodisperse, Mesoporous Natural Poly(Tannic Acid)-Silica Nanoparticle Composites With Antioxidant Properties
(Elsevier Science Bv, 2016) Sahiner, Nurettin; Sagbas, Selin; Aktas, Nahit
Mesoporous poly(Tannic Acid)-Silica nanoparticle composites (p(TA)-Si NPs) were prepared via one pot reaction. At various TA amounts in feed, 50,100, 250, 500, 1000 mg at different reaction times, 2, 4, 8,12, 24 h in the presence of TEOS and epoxy crosslinker, trimethylolpropane triglycidyl ether (TMPGDE), NPs composites were readily prepared. The prepared p(TA)-Si NPs by using 1000 mg TA at 12 h reaction time at room temperature as p(TA)1000-Si NPs provided the highest yield (similar to 48%). The particle size, monodispersity, specific surface area, porosity, and the gravimetric yields are greatly depended on initial TA concentration and reaction time. The particles sizes were found as 237-445 nm depending on TA content and reaction time. The highest surface area was measured as 872 m(2)/g for p(TA)1000-Si NPs for 2 h reaction time. The thermal stability of p(TA)-Si NPs decreased as TA content is increased. Interestingly, p(TA)1000-Si NPs are found effective antioxidant materials. (C) 2016 Elsevier Inc. All rights reserved.
Preparation of Macro-, Micro-, and Nano-Sized Poly(Tannic Acid) Particles With Controllable Degradability and Multiple Biomedical Uses
(Elsevier Sci Ltd, 2016) Sahiner, Nurettin; Sagbas, Selin; Aktas, Nahit
Different size ranges of poly(Tannic acid) (p(TA)) particles, 2000-500 mu m, 500-200 mu m, 200-20 mu m, and 20-0.5 mu m, were successfully synthesized by using lecithin/gasoline microemulsion media. Macro, micro, and nano sized p(TA) particles were crosslinked via poly(ethylene glycol) diglycidyl ether (PEGGE) with 85 +/- 7% gravimetric yield. The hydrolytic degradation of different sizes of p(TA) particles in physiological pH conditions, in pH 5.4, 7.4, and 9.0 buffer solutions at 37.5 degrees C, were investigated. It was found that p(TA) particles with 20-0.5 mu m size distribution are more stable than the other sized particles due to the higher amounts of crosslinker used during synthesis. Furthermore, macro size p(TA) particles (2000-500 mu m) were totally degraded at pH 9 within 12 days, whereas a linear and sustained degradation profile was obtained at pH 7.4 with 75 +/- 4% weight loss for 24 days. The antioxidant capacity of p(TA) particles was also tested and 20-0.5 mu m sized p(TA) particles demonstrated the highest antioxidant capacity with 0.1305 +/- 0.0124 mg gallic acid equivalency and 145 +/- 21 mM trolox equivalent g(-1). It was also further demonstrated that the degraded p(TA) particles showed high antimicrobial activity against a wide spectrum of bacteria and yeast strains such as Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, and Candida albicans. In vitro blood compatibility of p(TA) particles was also examined by hemolysis % and blood clotting index and micrometer sized p(TA) particles are more hemocompatible with enhanced blood clotting capability. In addition, WST-1 cytotoxicity test results showed that 200-20 mu m and 20-0.5 mu m sized p(TA) particles were biocompatible up to 50 mu g/mL concentration with 74 +/- 3 and 68 +/- 2% cell viabilities for L929 fibroblast cells. (C) 2016 Elsevier Ltd. All rights reserved.
Single Step Natural Poly(Tannic Acid) Particle Preparation as Multitalented Biomaterial
(Elsevier Science Bv, 2015) Sahiner, Nurettin; Sagbas, Selin; Aktas, Nahit
In this study, we report the preparation of poly(tannic acid) (p(TA)) particles by crosslinking with glycerol diglycidyl ether (GDE) and trimethylolpropane triglycidyl ether (TMPGDE). The p(TA) particles are negatively charged as obtained by the zeta potential measurements, -27 my.P(TA) particles are found to be an effective antioxidant material as 170 mg L-1 of p(TA) particle demonstrated the antioxidant equivalency of 82.5 +/- 7.2 mg L-1 of gallic acid (GA), used as standard in Folin-Ciocalteau (FC) method. Additionally, TA and p(TA) particles have a strong antimicrobial effect against Escherichia coli ATCC 8739, Staphylococcus aureus ATCC 6538, and Bacillus subtilis ATCC 6633. Furthermore, p(TA) particles were used as drug delivery materials by using model drugs such as TA itself, and GA in the release studies in PBS at pH 7.4 at 37.5 degrees C, and found that p(TA) particles can release 80.8 and 87.4% of the loaded TA and GA, respectively. Interestingly, p(TA) maintained its fluorescent property upon crosslinking of TA units. It is further demonstrated that p(TA) particles are as effective as cisplatin (a cancer drug) against A549 cancerous cells that both showed about 36 and 34% cell viability, respectively whereas linear TA showed 66% cell viability at 37.5 mu g mL(-1) concentration. Above this concentration p(TA) and cisplatin showed almost the same toxicity against A549 cancerous cells. Additionally, p(TA) particles are found to be much more biocompatible against L929 Fibroblast cells, about 84% cell viability in comparison to linear TA with about 53% at 75 mu g mL(-1) concentration. (C) 2015 Elsevier B.V. All rights reserved.
Super Poroushydrogels as Coordinating Templates for in Situ Metal Nanoparticle Preparation and Use as Soft Reactors in Hydrogen Production From the Hydrolysis of Hydrides
(Amer Chemical Soc, 2012) Sahiner, Nurettin; Sagbas, Selin; Turhan, Tugce; Karacan, Elif; Seven, Fahriye; Yasar, Alper; Aktas, Nahit
Synthesis, Characterization and Modification of Gum Arabic Microgels for Hemocompatibility and Antimicrobial Studies
(Elsevier Sci Ltd, 2017) Farooq, Muhammad; Sagbas, Selin; Sahiner, Mehtap; Siddiq, Mohammad; Turk, Mustafa; Aktas, Nahit; Sahiner, Nurettin
Gum Arabic (GA) microgels were successfully prepared via reverse micellization method with high yield (78.5 +/- 5.0%) in 5-100 mu m size range using divinyl sulfone (DVS) as a crosslinker. The GA microgels were degraded hydrolytically 22.8 +/- 3.5% at pH 1 in 20 days, whereas no degradation was observed at pH 7.4 and pH 9 at 37 degrees C. By using diethylenetriamine (DETA), and taurine (TA) as chemical modifying agents, GA microgels were chemically modified as GA-DETA and GA-TA, and the zeta potential values of 5.2 +/- 4.1 and -24.8 +/- 1.3 mV were measured, respectively in comparison to -27.3 +/- 4.2 mV for GA. Moreover, blood compatibility of GA, GA-TA, and GA-DETA microgels was tested via in vitro protein adsorption, % hemolysis ratio, and blood clotting index. All the microgels were hemocompatible with% hemolysis ratio between 0.23 to 2.05, and the GA microgels were found to be highly compatible with a blood clotting index of 81 +/- 40. The biocompatibility of GA, GA-DETA and GA-Taurine microgels against L929 fibroblast cells also revealed 84.4, 89.1, and 67.0% cell viability, respectively, at 25.0 mu g/mL concentration, suggesting great potential in vivo biomedical applications up to this concentration. In addition, 5 and 10 mgImL minimum inhibition concentrations of protonated GA-DETA microgels (GA-DETA-HCl) were determined against E. coli and S. aureus, respectively. (C) 2016 Elsevier Ltd. All rights reserved.
Synthesis, Characterization, and Use of Carbon Microspheres for Removal of Different Dyes From Aqueous Environments
(Springer, 2017) Sahiner, Nurettin; Farooq, Muhammad; Rehman, Saif Ur; Sagbas, Selin; Sahiner, Mehtap; Siddiq, Mohammad; Aktas, Nahit
Herein, we report the synthesis of carbon spheres (CS) using a relatively low-temperature hydrothermal technique using lactose as precursor pre-treated with HCl. The successful synthesis, spherical morphology, porous morphology, and monodispersed nature of CS were confirmed via scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Isoelectric point (IEP) was determined as 3.8, and at neutral conditions the prepared carbon particles are negatively charged at - 43 +/- 2.50 mV. Owing to their spherical morphology, almost uniform distribution and negatively charged surface at neutral conditions, the prepared CS were used as adsorbent for the removal of methylene blue (MB) and Geimsa stain (GS) from aqueous environments at pH 7. It was shown that CS has 97% adsorption capability for GS, whereas for methylene MB, the maximum adsorption capacity was 67% for 0.1-g CS from 50-ppm dye solutions in DI water. The adsorption studies revealed that the Langmuir and modified Fruendlich (MFE) adsorption models resulted in considerably high linear correlation coefficient (r(2)) values and the efficient adsorption of positively charged species on CS can be represented better with the MFE model.
Very Fast Catalytic Reduction of 4-Nitrophenol, Methylene Blue and Eosin Y in Natural Waters Using Green Chemistry: P(Tannic Acid)-Cu Ionic Liquid Composites
(Royal Soc Chemistry, 2015) Sahiner, Nurettin; Sagbas, Selin; Aktas, Nahit
Using tannic acid (TA) as a biopolymer, poly(tannic Acid) (p(TA)) microgels were obtained by cross-linking TA with trimethylolpropane triglycidyl ether (TMPGDE) as cross-linker in a water-in-oil micro emulsion system. Ionic liquid forms of p(TA) micro particles were prepared as Ionic Liquid Colloids (ILC) by post chemical modification of p(TA) particles using quaternization agents such as 3-chloro-2-hydroxypropyl trimethyl ammonium chloride (CHPACl) and ammonia (NH3) in aqueous solution to generate positively-charged ammonium salts on the network. Then the modified p(TA) micro particles were used as template for Co, Ni, and Cu metal nanoparticle preparation in situ after loading of metal salts such as CoCl2, NiCl2, and CuCl2 from ethyl alcohol solution into the p(TA) network, and consequent reduction with sodium borohydride (NaBH4). The prepared metal nanoparticle-containing ILCs of p(TA) microgel composites were used as catalysts in the reduction of toxic organic compounds such as 4-nitrophenol (4-NP), eosin Y (EY), and methylene blue (MB). Various parameters affecting the 4-NP and MB reduction were investigated. The activation energy, enthalpy, and entropy for the reduction of 4-NP to 4-AP catalyzed by ILC p(TA)-co composite catalyst system were calculated as 26.19 kJ mol(-1), 23.12 kJ mol(-1), and -182.35 J mol(-1) K-1, respectively.