Hydrogel nanonetworks with functional core-shell structure

Nanohydrogel particles of poly(acrylonitrile-co-N-isopropylacrylamide (p(AN-c-NIPAM)) were synthesized using a microemulsion polymerization technique. Highly monodisperse nanohydrogel particles e.g. 50-150 nm, and various morphology such as core-shell and connected beads were obtained. It was shown that the shell thickness and the size of particles can be tuned by the monomer concentrations and their ratios as well as by the utilization of different crosslinkers. The hydrophobic core monomer, AN was converted to amidoxime groups to increase the hydrophilicity of the nanogels which provide more hydrophilic character and impart new functionality to the nanonetwork. Transmission electron microscopy (TEM), and dynamic light scattering (DLS) techniques were employed for the particle size characterizations. The amidoximation reaction was confirmed by FT-IR spectroscopy.     

In situ metal particle preparation in cross-linked poly(2-acrylamido-2-methyl-1-propansulfonic acid) hydrogel networks

Anionic hydrogels of poly(2-acrylamido-2-methyl-1-propansulfonic acid) (p(AMPS)) were prepared with a different amount of cross-linker extent and used for in situ preparation of magnetic and metal particles. The metal particles with various sizes were obtained inside the three-dimensional polymer matrixes by absorption of the corresponding metal ions from their aqueous solutions followed by the reduction in the presence of strong reducing agent. In addition to iron particles, cobalt, nickel, copper nanoparticles, and CdS, quantum dot has been prepared by utilizing hydrogel matrix as a template for inorganic/organic composite synthesis. It was observed that the amount of cross-linkers (0.5%, 0.75%, and 1% with respect to monomer mole ratio) used in this study for bare p(AMPS) has not significantly influenced the morphology of the hydrogels or the size of the iron particles while having great effect on swelling of p(AMPS) hydrogels in water. Copolymeric hydrogels of AMPS with acrylamide in different composition were also prepared. Thermogravimetric analysis and transmission electron microscopy results showed that the AMPS content of the copolymeric hydrogel has great impact on both the metal ion loading capacity and the size of the resultant metal particles.     

Radiation synthesis of n-vinyl 2-pyrrolidone/acrylonitrile interpenetrating polymer networks and their use in uranium recovery from aqueous systems

Interpenetrating Polymer Networks (IPNs) based on Poly n-vinyl 2-pyrrolidone (PVP) and Acrylonitrile (AN) were prepared by irradiating PVP solutions prepared in AN. PVP/AN mixtures were irradiated by ⁶⁰Co-γ rays at room temperature at a dose rate of 0.5 kGy/hour. IPNs were characterized by using FT-IR and Thermal Analysis techniques. The chelating adsorbents containing amidoxime groups were prepared by the reaction of these IPNs with hydroxylamine in aqueous NaOH solution at 50°C. These amidoxime containing adsorbents were used in adsorption studies for the recovery of uranium from aqueous systems. The adsorption capacity of an IPN with equivolume fraction of PVP and amidoximated PAN was found to be 750mg UO₂²⁺/g dry amidoximated IPN.     

A facile preparation of donut-like supramolecular tannic acid-Fe(III) composite as biomaterials with magnetic,conductive, and antioxidant properties

Tannic acid (TA) complexes with various metal ions are prepared in buffer solutions by readily adjusting the pH, but there is no normalizing method to produce ferric tannate complexes. In this study, TA-Fe(III) complex was prepared in reverse microemulsion medium by reaction of TA as ligand with Fe(III) in 1:3 ligand:metal ion molar ratio. The complex was characterized by SEM, AFM, FT-IR, elemental analysis, AAS measurement, and Brunauer-Emmett-Teller (BET) method. Furthermore, magnetic susceptibility was tested with the Gouy method, and electronic spectral studies of TA-Fe(III) complex were completed with solid UV–vis measurements. The thermal stability was also studied by TGA analysis. These studies show that the ligand molecules have octahedral arrangement around Fe(III) and the complex is paramagnetic. The bandgap energy of the complex was calculated as 3.42 eV with solid UV–vis analysis. To determine antioxidant activity of the complex, Total Phenol Content (TPC) and Trolox Equivalent Antioxidant Concentration (TEAC) methods were used. The complex has great antioxidant properties with TPC = 45 ± 1 mg L^?1 GAE and TEAC = 296 ± 2 mM trolox g^?1 for dry sample.     

Oxidation of Aryl Alkyl Ketones To α-Acyloxy, α-(Camphorsulfonyloxy), or α-Hydroxy Derivatives Using Manganese(III) Acetate in Combination with Carboxylic Acids or (1S)-(+)-10-Camphorsulfonic Acid

The α-oxidation of aryl alkyl ketones using manganese(III) acetate in the presence of various carboxylic acids and (1S)-(+)-10-camphorsulfonic acid provided a convenient synthesis of α-acyloxy, α-(10-camphorsulfonyloxy), and α-hydroxy derivatives in good yield.     

Bi-phasic nanostructures for functional applications

Biphasic solid state composites of the type metal/metal oxide or element/element oxide can be synthesized in one pot chemical reactions using so called molecular "single source precursors". Due to their singular genesis these composites show peculiar hetero-structures based on core-shell hierarchies such as superlattices and composite nanospheres or nanowires. They exhibit superior or new functional properties compared to their individual constituent compounds. In the current work, we review in particular the synthetical and mechanistical approach of bi-phasic (Al/Al(2)O(3)) nanostructures such as nanospheres, nanowires and nanoloops using a single source precursor. Other bi-phasic materials of the general formula M/MO(x) (for example M = Ge, Sn, Pb) are addressed for comparison. The impact of different synthetical conditions as well as of modification of surfaces by laser techniques and their technological relevance are presented briefly. Additionally, functional applications of the prepared surfaces are explained with some outstanding case studies. These case studies are primarily concerned with their use as biomaterials and their application in medicine as well as with their use as thin films for optics and functional surfaces.     

Synthesis and characterization of poly(N‐(2‐mercaptoethyl) acrylamide) microgel for biomedical applications

N‐(2‐mercaptoethyl) acrylamide (MEAM) monomer was synthesized by acrylation of cysteamine and was cross‐linked with ethylene glycol dimethacrylate (EGDMA) via dispersion polymerization forming poly(N‐(2‐mercaptoethyl) acrylamide) (p(MEAM)) microgel. Then, the prepared microgels were tested for potential biomedical use, eg, antioxidant capacity and blood compatibility, cytotoxicity, apoptotic, and necrotic cell death; drug delivery properties were determined. Antioxidant studies of p(MEAM) microgels revealed a super antioxidant capability with total phenol content and trolox equivalent antioxidant capacity as 6.05 ± 1.15 mg/L gallic acid equivalency and 40.96 ± 2.40 mM trolox/g, respectively. Moreover, the blood compatibility of p(MEAM) microgels on fresh blood was resulted in lower than 1.0% hemolysis ratios for all the studied concentration range, and the blood clotting index was determined as 60.66% at 2.0 mg/mL at microgel concentration. The biocompatibility studies employing WST‐1 test on L929 fibroblast cells and DLD‐1 colon cancer cells have shown that p(MEAM) microgel was biocompatible up to 200 μg/mL concentration with the cell viability values of 84.54% and 86.15% on L929 fibroblast and DLD‐1 colon cancer cells, respectively. Using Captopril was used as model drug to test p(MEAM) microgel as drug delivery device for in vitro release studies at different pHs. Release profile of Captopril was found linear up to 5 hours with the released amounts of 9.81, 12.24, and 13.78 mg g^‐1microgel at the pH 1.5, 7.4, and 9.0, respectively.     

Thermal computations of temperature distribution and bulb heat transfer in an automobile headlamp

In this study, experimental and numerical analysis was performed to define thermal deformation inside the head lamp because of usage plastic materials and thermal loads. Buoyancy, radiation and conjugate effects were considered. Velocity and temperature distributions were obtained and possible hot points and condense regions can be determined. Nusselt number distribution on cylindrical bulb were computed and compared with literature. Relatively important heat transfer increase in natural convection was found.     

PHA-L lectin and carbohydrate relationship: conjugation with CdSe/CdS nanoparticles, radiolabeling and in vitro affinities on MCF-7 cells

This research aims to investigate the interaction between phytohemagglutinin-L (PHA-L) and sialic acid, which is abundant on the breast cancer cell (MCF-7) surface and displays monosaccharide characteristics, by experimental and computational methods. Experimentally, CdSe/CdS nanoparticles (QDs) were synthesized; PHA-L was conjugated with QDs and labeled with ¹²⁵I. Radiolabeling yield was found to be 97 ± 1.2 %. Afterwards, in vitro bioaffinities of radiolabeled PHA-L conjugated QDs have been investigated on MCF-7 cells and it has been observed that the cell incorporation increased with time. The results indicated that ¹²⁵I labeled QD-PHA-L conjugates represent significant affinity on MCF-7 cells. In the second step of the study, the crystal structure of carbohydrate interaction surface of PHA-L was extracted from the crystal structure of PHA-L. The interactions between this surface and sialic acid were calculated by computational tools. These calculations revealed specific interactions between PHA-L and sialic acid. Semi-empirical methods, PM3 and AM1, were used in these calculations. Significant outcomes have been obtained from the experimental and computational studies and these results demonstrated that PHA-L may be an effective agent for imagining MCF-7 cells.     

Self-Crosslinked Ellipsoidal Poly(Tannic Acid) Particles for Bio-Medical Applications

Self-crosslinking of Tannic acid (TA) was accomplished to obtain poly(tannic acid) (p(TA)) particles in single step, surfactant free media using sodium periodate (NaIO₄) as an oxidizing agent. Almost monodisperse p(TA) particles with 981 ± 76 nm sizes and −22 ± 4 mV zeta potential value with ellipsoidal shape was obtained. Only slight degradation of p(TA) particles with 6.8 ± 0.2% was observed at pH 7.4 in PBS up to 15 days because of the irreversible covalent formation between TA units, suggesting that hydrolytic degradation is independent from the used amounts of oxidation agents. p(TA) particles were found to be non-hemolytic up to 0.5 mg/mL concentration and found not to affect blood clotting mechanism up to 2 mg/mL concentration. Antioxidant activity of p(TA) particles was investigated by total phenol content (TPC), ferric reducing antioxidant potential (FRAP), trolox equivalent antioxidant capacity (TEAC), total flavanoid content (TFC), and Fe (II) chelating activity. p(TA) particles showed strong antioxidant capability in comparison to TA molecules, except FRAP assay. The antibacterial activity of p(TA) particles was investigated by micro-dilution technique on E. coli as Gram‑negative and S. aureus as Gram-positive bacteria and found that p(TA) particles are more effective on S. aureus with over 50% inhibition at 20 mg/mL concentration attained.