Ufuk Yildiz

The removal of heavy metal ions from aqueous solutions by novel pH-sensitive hydrogels

Novel non-ionic hydrogels were synthesized by radical homopolymerization of N-vinyl-2-pyrrolidone (VP) or by radical copolymerization of VP with methylacrylate (MA). A macroinimer (MIM) was used as a crosslinker and initiator, as well. The percentage of mass swelling ratios (S(M)), the molecular weight between crosslinks (M(c)) and Youngs modulus of the hydrogels were investigated. The hydrogels were used as binding materials for different heavy metal ions such as Cu(2+), Cd(2+), Ni(2+) and Zn(2+) under varying conditions. The binding capability of the hydrogels toward the metal ions decreases in the following order: Cu(2+)>Ni(2+)>Zn(2+)>Cd(2+).

Dispersion redox copolymerization of methyl methacrylate with macromonomeric azoinitiator as a macrocrosslinker

The dispersion copolymerization of methyl methacrylate (MMA) with macromonomeric azoinitiator, MIM-400, as a macrocrosslinker initiated by the benzoyl peroxide (BPO)/N,N 0 dimethylaniline (DMA) coupled in water/ethanol (4/1, v/v) at 208C was carried out to yield PEG-b-PMMA networks with labile azo linkages in the main chain. Gel fraction, swelling ratios (qv) and the average molecular weights between junction points (Mc) values of the networks were investigated. Maximum gel fraction was obtained using 0.133 M MIM-400,

Reversible aggregation of responsive polymer-stabilized colloids and the pH-dependent formation of porous scaffolds†

Branched copolymer stabilized emulsion droplets can be used as templates for the production of surface-functionalized colloidal particles. The pre-defined pH-responsive surface functionality can control the solution behavior of these colloids—from highly disperse to aggregated. The colloids can co-encapsulate various hydrophobic molecules and can be assembled into large site-isolated 3D aggregates with internal macroporosities dictated by the method of dehydration employed. The assembled colloids can be rehydrated and remain stable in acidic water but disassemble back into disperse colloids on raising the solution pH. Thus these functional colloids have potential application as building blocks for the preparation of modular scaffold materials

Synthesis, characterization and swelling investigations of novel polyetheramine-based hydrogels

AbstractNovel polyetheramine-based hydrogels have been synthesized by reacting difunctional Jeffamine of varying molecular weights (ED600, ED900 and ED2003) with glutaraldehyde (GA) in the presence of trifunctional Jeffamine (T403) as a crosslinker. The prepared hydrogels were characterized by Fourier Transform Infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) techniques. Network properties of the hydrogels were evaluated via swelling investigations. Higher molecular weight of Jeffamine generated hydrogel networks with lower crosslink densities, consequently higher swelling abilities. The crosslink density of the hydrogels increased with increasing GA amount. The prepared hydrogels demonstrated to be pH and temperature responsive depicting decrease in swelling ratios with increasing pH and temperature. The obtained swelling results indicated that the swelling behavior of the hydrogels agreed with the Flory–Rehner equation.Graphical abstract Novel polyetheramine crosslinked based water-insoluble hydrogels having imine functional groups in their network structures were prepared via polymerization of difunctional Jeffamine monomers. Investigated influence of different Jeffamine molecular weight synthesized hydrogels depicted suitable swelling, pH and temperature responsive properties.

Fabrication and characterization of soft macroporous Jeffamine cryogels as potential materials for tissue applications

Macroporous three-dimensional (3D) scaffolds have been proven to function as structural substrates and as apertures for cell growth and proliferation thereby ensuring tissue regeneration. Such scaffolds demonstrate high pore interconnectivity and functionality and as a result permit cell adherence and growth while maintaining mechanical strength, biodegradability and biocompatibility without causing any immune response. In this study, macroporous cryogels were synthesized from difunctional Jeffamine (600, 900 and 2000 g mol−1) and glutaraldehyde in the presence of a trifunctional Jeffamine (403 g mol−1) as a crosslinker via a freeze-drying technique. The fabricated cryogels were subsequently reduced by reductive amination to create more active functional groups which increase biological interaction. The functional groups, reductive efficacy, pore size/surface topology and thermal stability were analysed using FT-IR and 13C-NMR, SEM and TGA, respectively. Visco-elastic behaviour of the cryogels was investigated by unconfined compression test which depicted good elastic modulus and mechanical strength. Considerable swelling ratios were obtained alongside in vitro degradation analysis performed for 10 days at pH 7.4. In addition, in vitro biocompatibility was evaluated via MTT assay for 24 h at 37 °C using Human Umbilical Vein Endothelial Cells (HUVEC) for cell growth and cytotoxicity evaluation on the non-reduced and reduced Jeffamine cryogels.

A design optimization study on synthesized nanocrystalline cellulose, evaluation and surface modification as a potential biomaterial for prospective biomedical applications

In the present study, nanocrystalline cellulose (NCC) was prepared via acid hydrolysis and synthesis parameters were optimized via response surface modelling with a determined maximum NCC yield of 43.8%. The optimized NCC sample was subsequently surface modified via epichlorohydrin-mediated amination forming aminated nanocrystalline cellulose (A-NCC) with an amine content calculated as 1500μmol/g. The average particle size and zeta potential were determined 100nm and 325nm for NCC and A-NCC, respectively. Structural properties were analyzed by FTIR, TEM and XRD techniques. The obtained A-NCC as final product depicted a pKa value of 10.86±0.07 demonstrating favourable protonation of amine groups at physiological pH allowing the material to be suitable for prospective application in drug delivery and tissue engineering.

A new Schiff base: Synthesis, characterization and optimization of metal ions-binding properties

ABSTRACT In this study, a new Schiff base (H4TSTE) was synthesized and characterized by elemental analysis, FT-IR, NMR and MS spectral data. Liquid–liquid extraction process was performed for removal of Cu(II), Mn(II), Ni(II), Pb(II) and Zn(II) from aqueous solutions by means of H4TSTE. The extractions were investigated depending on the concentration of picric acid, metal ion and H4TSTE ligand. Response surface methodology (RSM) was first applied to optimize metal ion-binding properties of H4TSTE. The extraction efficiency was estimated to be >98% for all metals by models. Under the same conditions, the extraction efficiency was experimentally found to be >97% with a relative standard deviation within ±0.10 (N = 4), indicating the suitability of the models.

Pickering emulsions stabilized nanocellulosic-based nanoparticles for coumarin and curcumin nanoencapsulations: In vitro release, anticancer and antimicrobial activities

Coumarin and curcumin have a wide spectrum of biological and pharmacological activities including antioxidant, anti-inflammatory, antimicrobial and anticancer but hindered therapeutic applications due to low stability and poor solubility in water. The main objective of the current study was to overcome these drawbacks via improved bioavailability by nanoencapsulated emulsions. Pickering emulsion (PE) via oil-in-water approach were stabilized by aminated nanocellulose (ANC) particles through application of a full factorial optimization design for nanoemulsions containing different composition of oil phase with medium chain triglyceride (MCT) and Tween 80. The fabricated nanoemulsions and PEs with average particle sizes (≤150 nm) were obtained. Influencing factors such as ANC concentration, storage time and pH on the stability of emulsions were examined alongside zeta potentials. Encapsulation efficiency (EE) of coumarin and curcumin were determined as >90%. Release kinetic profiles for encapsulated PEs displayed sustained release with supposed increase bioavailability. Higher release percent were detected for curcumin encapsulated PE in contrast to coumarin. In vitro cytotoxicity evaluation for coumarin and curcumin loaded PEs were further investigated for anticancer and antimicrobial activities using human cell lines (L929 and MCF-7) and different microorganisms (Gram (+), Gram (-) and fungi), respectively. The results clearly demonstrated PE coumarin and curcumin as promising candidates to inhibit microbial growth and to prevent preferential killing of cancer cells compared to normal cells.

Treatment of hazardous waste incineration plant effluent by novel hydrogels

Statement of the Problem: Catalytic synthesis of organic sulfenamides and disulfides has great significance and value in synthetic chemistry and bioscience. Despite the prominent applications of sulfenamides, there are only a few reports about their preparation. In this contribution, we reported an oxidative coupling of 2-mercaptobenzothiazole leading to 2,2-disbenzothiazoledisulfide in up to 94 % yield.G acid (GABA) is a precursor to pyrrolidone, a monomer used for the production of a biodegradable polymer known as nylon-4. GABA is also widely used in the medical industry to treat conditions such as high blood pressure, anxiety and depression. Generally, GABA is produced from glutamate by the enzyme glutamate decarboxylase (GadB). In this study, a synthetic scaffold complex was introduced between Pyrococcus horikoshii GadB and the GABA antiporter (GadC) from E. coli. P. horikoshii GadB was attached to the N-terminus, C-terminus and middle of E. coli GadC via scaffolding. Among the three scaffold complexes evaluated, the N-terminus scaffold model produced 5.93 g/L of GABA from 10 g/L monosodium glutamate (MSG). When the gabT mutant E. coli XBT strain was used, the highest GABA concentration of 5.96 g/L was obtained, which is 97.8% of GABA yield. In addition to GABA concentration, GABA productivity was increased 3.5 fold via the synthetic scaffold complex.

A response surface modelling study for sorption of Cu2+, Ni2+, Zn2+ and Cd2+ using chemically modified poly(vinylpyrrolidone) and poly(vinylpyrrolidone-co-methylacrylate) hydrogels

In this present study, response surface methodology was applied for the optimization and evaluation of different heavy-metal sorption processes. Poly(vinylpyrrolidone) and poly(vinylpyrrolidone-co-methylacrylate) hydrogels were used as pH-responsive adsorbents to investigate their efficiency in the uptake of Cu2+, Ni2+, Zn2+ and Cd2+ metal ions from aqueous solution in a batch reactor system. The effect of operational parameters such as initial pH and contact time were studied using central composite design. Analysis of variance depicted the central composite design model was significant for Cu2+, Ni2+, Zn2+ and Cd2+ metal ions removal by the investigated hydrogels. A comparison between the model results and experimental data showed that poly(vinylpyrrolidone-co-methylacrylate) possessed higher metal ions binding affinity than poly(vinylpyrrolidone) hydrogel. The heavy-metal ions sorption kinetic well fitted the pseudo second-order kinetic model. Evaluation of the intraparticle diffusion model suggested the sorption process occurred in two phases: surface sorption and intraparticle diffusion. Isothermic results revealed that Freundlich and Temkin isotherms best described the adsorbate–adsorbent interactions. Maximum sorption capacities were observed for Cu2+ ion and were determined as 86.66 mg/g and 98.53 mg/g for poly(vinylpyrrolidone) and poly(vinylpyrrolidone-co-methylacrylate) hydrogels, respectively.