Novel magnetic composites based on water soluble unsaturated polyester resin and iron oxide nanoparticles

Magnetic nanocomposites on the basis of water soluble unsaturated polyester resin filled with different amount of iron oxide nanoparticles have been successfully prepared. The mechanical properties of thus prepared composites as tensile, impact and flexural strength were determined. The specific volume and surface resistance of the magnetic nanocomposites were also determined

Bio-inspired antibacterial polymer coatings with included silver nanoparticles and porphyrin-based photosensitizer

peer reviewedIn this work, we have prepared novel bio-inspired photoactive antibacterial polymer coatings on stainless steel (SS), which possess good mechanical and antibacterial properties. The formation of the photoactive antibacterial polymer coatings consists of the sequential deposition of three components on SS substrate (1) a catechol-based cationic glue P(mDOPA)-co-P(DMAEMA+) used as a universal primer, which facilitates the strong anchoring to SS; (2) a silver loaded (Pox(mDOPA)-Ag0/PAH) nanogel decorated with o-quinones applied to enhance the antibacterial properties of the coating and to permit the covalent grafting of the photosensitizer, and (3) an ethylene diamine derivative of protoporphyrin IX (PPIX-ED). Porphyrins are widely recognized for their antibacterial activity by producing reactive oxygen species when exposed to visible light. To estimate the deposition of the components on the SS substrate, SEM-EDX elemental mapping analysis was applied. Scratch test, nanoindentation, and accelerated property mapping (XPM) analysis were used to assess the mechanical properties of the coatings. The established antibacterial activity of the prepared photoactive polymer coatings on SS against Gram-positive B. subtilis and Gram-negative E. coli strains demonstrates their potential applications in medical and biomedical fields

Development and characterization of active films based on starch-PVA, containing silver nanoparticles

[EN] In order to obtain antimicrobial packaging films, starch-PVA-based films with silver nanoparticles (AgNPs) have been developed and characterized as to their physical and antimicrobial properties and silver release kinetics to polar (A, B, C and D1) and non-polar (D2) food simulants. Antimicrobial activity against two bacteria, Listeria innocua and Escherichia coli, and two fungi, Aspergillus niger and Penicillium expansum, was studied. Silver-loaded starch-PVA films exhibited antimicrobial activity gainst the tested microorganisms, which depended heavily on the concentration of AgNPs. Their addition only led to notable physical changes in the colour and transparency of the films, which underwent significant changes and turned brownish-yellow and opaque, this being more notable when the silver concentration rose. Silver was released into aqueous simulants in its entirety within the first 60 min of contact. In the non-polar simulant (oleic acid), the release capacity of the films drastically decreased, being the only case where the established limit (60 mg/kg simulant) was met. As a consequence, the use of the developed films as food packaging materials should be restricted to fat-rich foodstuffs.The authors acknowledge the financial support from the Spanish Ministerio de Economia y Competitividad through the project AGL2013-42989-R. Amalia Cano also thanks the Spanish Ministerio de Educacion, Cultura y Deporte for the FPU grant.Cano Embuena, AI.; Cháfer Nácher, MT.; Chiralt, A.; González Martínez, MC. (2016). Development and characterization of active films based on starch-PVA, containing silver nanoparticles. Food Packaging and Shelf Life. 10:16-24. doi:10.1016/j.fpsl.2016.07.002S16241

Rapid continuous microwave-assisted synthesis of silver nanoparticles to achieve very high productivity and full yield: from mechanistic study to optimal fabrication strategy

Systematic studies of silver nanoparticle synthesis in a continuous-flow single-mode microwave reactor using polyol process were performed, revealing that the synthesis is exceptionally effective to give very small metal particles at full reaction yield and very high productivity. Inlet concentration of silver nitrate or silver acetate, applied as metal precursors, varied between 10 and 50 mM, and flow rates ranged from 0.635 to 2.5 dm3/h, to give 3–24 s reaction time. Owing to its much higher reactivity, silver acetate was shown to be far superior substrate for the synthesis of small (10–20 nm) spherical silver nanoparticles within a few seconds. Its restricted solubility in ethylene glycol, applied as the solvent and reducing agent, appeared to be vital for effective separation of the stage of particle growth from its nucleation to enable rapid synthesis of small particles in a highly loaded system. This was not possible to obtain using silver nitrate. All the observations could perfectly be explained by a classical LaMer–Dinegar model of NPs’ formation, but taking into account also nonisothermal character of the continuous-flow process and acetate dissolution in the reaction system. The performed studies indicate an optimal strategy for the high-yield fabrication of metal particles using polyol method

Sarcosine Oxidase Encapsulated Polyvinyl Alcohol-Silica-AuNP Hybrid Films for Sarcosine Sensing Electrochemical Bioelectrode

The amperometric response of sarcosine was measured in aqueous media containing ferrocene monocarboxylic acid using the redox enzyme sarcosine oxidase (SOD) immobilized in a composite material based on polyvinyl alcohol (PVA) and partially prehydrolyzed tetraethyl orthosilicate (pphTEOS) at the surface of “in-house” fabricated graphite electrodes. For comparison, separate electrodes consisting of silver and gold nanoparticles (Ag/AuNPs) embedded in the PVA-pphTEOS matrix was prepared employing a novel sol-gel process based on the in situ chemical reduction of Ag or Au ions using PVA both, as a reducing agent and stabilizer. The analytical performance of the enzyme electrodes was studied in terms of linear ranges, sensitivities, response times, limits of detection, reproducibility and stability

Cobalt-mediated radical polymerization (CMRP) of vinyl acetate initiated by redox systems: Toward the scale-up of CMRP

A redox initiating system was developed in order to bypass 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile) (V70) as the initiator of the cobalt-mediated radical polymerization (CMRP) of vinyl acetate (VAc) in the presence of cobalt(II) acetylacetonate (Co(acac)(2)). It is indeed a problem to stock up with V70 because of needed storage at -20 degrees C during transportation. This paper reports on the controlled CMRP of VAc initiated by ascorbic acid combined with either lauroyl peroxide or benzoyl peroxide at 30 degrees C. Substitution of citric acid for ascorbic acid results in faster polymerization whereas the polymerization control is maintained. All these improvements facilitate the implementation of the vinyl acetate CMRP and open the door to the scale-up of the process

Cadmium and copper absorption mediated by a poly(vinyl alcohol)-b-polyacrylonitrile based micelle/Trichosporon cutaneum cell system

The micelles of a recently synthesized copolymer of poly(vinyl alcohol)-b-polyacrylonitrile added to the growth solution of the filamentous yeast Trichosporon cutaneum strain R57 led to the formation of a binary system consisting of micelles and cells. The resulting micelle/cell system was studied as a model for the removal of toxic concentrations of heavy-metal ions (cadmium and copper) from aqueous solutions. The ion-removal efficiency mediated by this system was higher than for free-floating cells. The copper-removal efficiency from the solution reached a level of 65% after 24 h of cultivation, whereas the cadmium-removal efficiency reached 62% after 6 h of growth. For comparison, the free-floating cells removed 42% of copper and only 38% of cadmium from the solutions. The effects of surface interactions between the cells and polymer micelles on the biosorption capacity of the cells are discussed in the article