Novel hydrogel membrane based on copoly(hydroxyethyl methacrylate/p-vinylbenzyl-poly(ethylene oxide)) for biomedical applications: properties and drug release characteristics

The aim of this study was to synthesize and characterize a novel biocompatible polymeric membrane system and demonstrate its potential use in various biomedical applications. Synthetic hydrogels based on poly(hydroxyethyl methacrylate), poly(HEMA), have been widely studied and used in biomedical fields. A novel copolymer hydrogel was prepared in the membrane form using 2-hydroxyethyl methacrylate monomer (HEMA) and a macromonomer p-vinylbenzyl-poly(ethylene oxide) (V-PEO) via photoinitiated polymerization. A series of poly(HEMA/V-PEO) copolymer membranes with different compositions was prepared. The membranes were characterized using infrared, thermal and SEM analysis. The thermal stabilities of the copolymer membranes were found to be lowered by an increase in the ratio of macromonomer (V-PEO) in the membrane structure. Because of the incorporation of PEO segments, the copolymers exhibited significantly higher hydrophilic surface properties than pure poly(HEMA), as demonstrated by contact angle measurements. Equilibrium swelling studies were conducted to investigate the swelling behavior of the membranes. The equilibrium water uptake was reached in about 4 h. Moreover, the blood protein adsorption and platelet adhesion were significantly reduced on the surface of the PEO containing copolymer membranes compared to control pure poly(HEMA). Drug release experiments were performed in a continuous release system using model drug (vancomycin) loaded copoly(HEMA/V-PEO) membranes. A specific poly(HEMA/V-PEO) membrane formulation possessing the highest PEO content (with a HEMA:V-PEO (mmol:mmol) feed ratio of 112:1 and loaded with 40 mg antibiotic/g polymer) released about 81% of the total loaded drug in 24 h at pH 7.4. This membrane composition provided the best results and can be considered as a potential candidate for a transdermal antibiotic carrier and various biomedical and biotechnological applications.     

Biosorption of uranium(VI) by free and entrapped Chlamydomonas reinhardtii: kinetic,equilibrium and thermodynamic studies

Biosorption of uranium from aqueous solution onto the free and entrapped algae, “Chlamydomonas reinhardtii” in carboxymethyl cellulose (CMC) beads was investigated in a batch system using bare CMC beads as a control system. CMC can be a potential natural biosorbent for radionuclide removal as it contains carboxyl groups. However, limited information is available with the biosorption of uranium by CMC, when adsorption isotherm, kinetics and thermodynamics parameters are concerned. The biosorbent preparations were characterized by swelling tests, FTIR, and surface area studies. The effects of pH, temperature, ionic strength, biosorbent dosage, and initial uranium concentrations on uranium biosorption were investigated. Freely suspended algae exhibited the highest uranium uptake capacity with an initial uranium ion concentration of 1,000 mg/L at pH of 4.5 and at 25 °C. The removal of U(VI) ion from the aqueous solution with all the tested biosorbents increased as the initial concentration of U(VI) ion increased in the medium. Maximum biosorption capacities for free algal cells, entrapped algal cells, and bare CMC beads were found to be 337.2, 196.8, and 153.4 mg U(VI)/g, respectively. The kinetic studies indicated that the biosorption of U(VI) ion was well described by the pseudo-second order kinetic model. The variations in enthalpy and entropy for the tested biosorbent were calculated from the experimental data. The algal cells entrapped beads were regenerated using 10 mM HNO₃, with up to 94 % recovery. Algal cells entrapped CMC beads is a low cost and a potential composite biosorbent with high biosorption capacity for the removal of U(VI) from waters.     

Evolution of magnetic and structural properties of TiO2 with Co-doping

This paper presents the phase formations and magnetic properties of Co-doped TiO₂ synthesized by the colloidal and ammonium nitrate melt techniques (ANMT). The phase formations and ferromagnetic properties were studied with XRD and SQUID magnetometry. Crystallization of the TiO₂ rutile lattice was completed at 1000 °C and that was preserved during annealing up to 1300 °C. For the samples annealed at 1200 °C, elemental analysis has shown that the colloidal technique leads to a single-phase rutile with cobalt concentration of almost nothing even in the initially 0.5 mol Co-added samples. Further increase of annealing temperature results in the appearance of other Ti-phases in addition to the rutile. On the other hand, it is quite interesting that these samples show ferromagnetic behavior. The samples synthesized by the ANMT method contain larger amounts of Co compared to the colloidal technique.     

Structural properties of polystyrene oligomers in different environments: a molecular dynamics study

We have performed detailed molecular dynamics simulations to investigate the effects of solvation and confinement on the structure of polystyrene (PS) oligomers in four different environments, melt, concentrated solution, dilute solution and confined concentrated solution at 450 K and 1 bar, respectively. Local packing of the monomers and the solvent (toluene, good solvent) molecules were monitored by means of radial distribution functions (RDFs). We have also investigated bond, angle, and dihedral angle distributions of the monomers. End-to-end distances, radii of gyration and persistence lengths were calculated to characterize the static properties. The chain in the dilute solution was found to exhibit more stretched conformations. Dilution effect of the solvent was observed in the RDFs between the monomer centers. Only slight conformational changes in the polymers were observed by solvation. The effect of confinement was mainly seen in the density profiles, which showed an oscillatory behavior in the confined system.     

Pathogen detection in complex samples by quartz crystal microbalance sensor coupled to aptamer functionalized core–shell type magnetic separation

A quartz crystal microbalance sensor (QCM) was developed for sensitive and specific detection of Salmonella enterica serovar typhimurium cells in food samples by integrating a magnetic bead purification system. Although many sensor formats based on bioaffinity agents have been developed for sensitive and specific detection of bacterial cells, the development of robust sensor applications for food samples remained a challenging issue. A viable strategy would be to integrate QCM to a pre-purification system. Here, we report a novel and sensitive high throughput strategy which combines an aptamer-based magnetic separation system for rapid enrichment of target pathogens and a QCM analysis for specific and real-time monitoring. As a proof-of-concept study, the integration of Salmonella binding aptamer immobilized magnetic beads to the aptamer-based QCM system was reported in order to develop a method for selective detection of Salmonella. Since our magnetic separation system can efficiently capture cells in a relatively short processing time (less than 10 min), feeding captured bacteria to a QCM flow cell system showed specific detection of Salmonella cells at 100 CFU mL⁻¹ from model food sample (i.e., milk). Subsequent treatment of the QCM crystal surface with NaOH solution regenerated the aptamer-sensor allowing each crystal to be used several times.     

Light scattering by DNA structure due to phase transition

Modelling and numerical calculations of light scattering by the deoxyribonucleic acid (DNA) molecule were investigated using the transition matrix method at the phase transition region. In this model for a DNA molecule with helix structure, the electrical field was established and the transition matrix calculated for this field. Numerical computation of a simple cylindrical model, represented by adenine–thymine (A–T) and guanine–cytosine (G–C) formed with a lamellar-like helix, enabled important results to be obtained. These results were generalized for different molecular orientations with dielectric properties at the phase transition, which occurred due to the electric field changing. Finally, these results are associated with improved models for previous geometries.     

Leaching of silver from solid waste using ultrasound assisted thiourea method

Thiourea leaching of precious metals such as gold and silver from ores has several advantages when compared with conventional cyanidation process. In recent years, the use of ultrasound in leaching processes is becoming increasingly popular in hydrometallurgy. This paper deals with combining these two techniques for silver leaching from solid waste of a cyanidation leach plant located in Kutahya, Turkey. The primary aim of this research is to assess the technical performance of the method. To achieve maximum leaching yield, eight process variables have been selected to estimate optimum process conditions by means of statistical factorial design and steepest ascent techniques. Laboratory-scale experiments showed that complete leaching of silver may be achieved by this process.