Controlled release antimicrobial sachet prepared from poly(butylene succinate)/geraniol and ethylene vinyl alcohol coated paper for bread shelf-life extension application.

This research aims to develop white bread shelf-life extension sachet with controlled release of antimicrobial agent prepared from multicomponent bio-based materials. The structure of antimicrobial sachet consists of two major parts i.e., controlled release part and active part. The first part produced from paper coated with ethylene vinyl alcohol (EVOH). The second one was an active part which produced from biodegradable poly(butylene succinate) (PBS) and geraniol essential oil blend. Inhibition clear zone test results showed that a suitable geraniol concentration, encapsulated in PBS, was 10 wt%. Based on the water vapor transmission test, coating paper with EVOH for three times (around 450 µm) was an optimal condition for the use as a controlled release part. Release test indicated that geraniol migration concentration increased with increasing the relative humidity (RH) in the package which correlated to the moisture liberated from bread slice. Shelf-life extension study informed that the spoilage of bread stored with antimicrobial sachet was delayed by more than three weeks. In summary, this antimicrobial sachet could be used in food shelf-life extension purpose which easily placed in any food container. This is an alternative way of food waste minimization.

Synthesis of one-dimensional gold nanostructures and the electrochemical application of the nanohybrid containing functionalized graphene oxide for cholesterol biosensing.

This manuscript reports a new approach for the synthesis of one dimensional gold nanostructure (AuNs) and its application in the development of cholesterol biosensor. Au nanostructures have been synthesized by exploiting ß-diphenylalanine (ß-FF) as an sacrificial template, whereas the Au nanoparticles (AuNPs) were synthesized by ultrasound irradiation. X-ray diffractometer (XRD), scanning electron microscope (SEM) and energy dispersive analysis of X-rays (EDAX) have been employed to characterize the morphology and composition of the prepared samples. With the aim to develop a highly sensitive cholesterol biosensor, cholesterol oxidase (ChOx) was immobilized on AuNs which were appended on the graphite (Gr) electrode via chemisorption onto thiol-functionalized graphene oxide (GO-SH). This Gr/GO-SH/AuNs/ChOx biosensor has been characterized using cyclic voltammetry (CV), electrochemical impedance spectroscopy and chronoamperometry. CV results indicated a direct electron transfer between the enzyme and the electrode surface. A new potentiostat intermitant titration technique (PITT) has been studied to determine the diffusion coefficient and maxima potential value. The proposed biosensor showed rapid response, high sensitivity, wide linear range and low detection limit. Furthermore, our AuNs modified electrode showed excellent selectivity, repeatability, reproducibility and long term stability. The proposed electrode has also been used successfully to determine cholesterol in serum samples.

High pressure pyrolyzed non-precious metal oxygen reduction catalysts for alkaline polymer electrolyte membrane fuel cells.

Non-precious metal catalysts, such as metal-coordinated to nitrogen doped-carbon, have shown reasonable oxygen reduction reaction (ORR) performances in alkaline fuel cells. In this report, we present the development of a highly active, stable and low-cost non-precious metal ORR catalyst by direct synthesis under autogenic-pressure conditions. Transmission electron microscopy studies show highly porous Fe-N-C and Co-N-C structures, which were further confirmed by Brunauer-Emmett-Teller surface area measurements. The surface areas of the Fe-N-C and Co-N-C catalysts were found to be 377.5 and 369.3 m(2) g(-1), respectively. XPS results show the possible existence of N-C and M-Nx structures, which are generally proposed to be the active sites in non-precious metal catalysts. The Fe-N-C electrocatalyst exhibits an ORR half-wave potential 20 mV higher than the reference Pt/C catalyst. The cycling durability test for Fe-N-C over 5000 cycles shows that the half-wave potential lost only 4 mV, whereas the half-wave potential of the Pt/C catalyst lost about 50 mV. The Fe-N-C catalyst exhibited an improved activity and stability compared to the reference Pt/C catalyst and it possesses a direct 4-electron transfer pathway for the ORR process. Further, the Fe-N-C catalyst produces extremely low HO2(-) content, as confirmed by the rotating ring-disk electrode measurements. In the alkaline fuel single cell tests, maximum power densities of 75 and 80 mW cm(-2) were observed for the Fe-N-C and Pt/C cathodes, respectively. Durability studies (100 h) showed that decay of the fuel cell current was more prominent for the Pt/C cathode catalyst compared to the Fe-N-C cathode catalyst. Therefore, the Fe-N-C catalyst appears to be a promising new class of non-precious metal catalysts prepared by an autogenic synthetic method.

Necrotic cell death caused by exposure to graphitic carbon-coated magnetic nanoparticles.

We synthesized graphitic carbon-coated magnetic nanoparticles (Fe@C NPs) and evaluated their physicochemical properties and mechanism of cytotoxicity in vitro. The structure of these nanocomposites consisted of an iron core encapsulated by a graphitic-carbon shell. The diameter of these Fe@C NPs was 81 ± 14 nm, and the thickness of the carbon layer encapsulating the core was 7.0 ± 0.5 nm. Inhibition of cell proliferation was induced by exposure to Fe@C NPs at doses above 50 µg mL(-1) . The exposed cells did not show increased activation of apoptosis biomarkers such as PARP, caspase-3, caspase-7, and caspase-9, and apoptosis-specific responses such as DNA laddering and annexin V binding to the cell membranes. In addition, the expression levels of autophagy-specific biomarkers such as ATG5 and LC3 after exposure were not enhanced, either. Instead, we observed increased release of lactate dehydrogenase in the culture media and red-fluorescent cell cytosol stained with ethidium homodimer I after the exposure. These results indicated enhanced cell membrane permeability after exposure to Fe@C NPs, probably caused by necrosis. The analysis of the regulatory molecules of cell cycling and proliferation, ERK, p53, and AKT, implied that cell cycle arrest was initiated and the cells were sensitized to necrosis. This necrotic cell death was also observed in carbon shells from Fe@C NPs obtained by removing the metal core. In conclusion, the graphitic carbon-encapsulated magnetic nanoparticles synthesized by one-pot synthesis induced necrotic cell death to human HEK293 cells, which was caused by graphitic carbon surface encapsulating the metal core.

Photothermal cancer therapy using graphitic carbon-coated magnetic particles prepared by one-pot synthesis.

We describe here a simple synthetic strategy for the fabrication of carbon-coated Fe3O4 (Fe3O4@C) particles using a single-component precursor, iron (III) diethylenetriaminepentaacetic acid complex. Physicochemical analyses revealed that the core of the synthesized particles consists of ferromagnetic Fe3O4 material ranging several hundred nanometers, embedded in nitrogen-doped graphitic carbon with a thickness of ~120 nm. Because of their photothermal activity (absorption of near-infrared [NIR] light), the Fe3O4@C particles have been investigated for photothermal therapeutic applications. An example of one such application would be the use of Fe3O4@C particles in human adenocarcinoma A549 cells by means of NIR-triggered cell death. In this system, the Fe3O4@C can rapidly generate heat, causing >98% cell death within 10 minutes under 808 nm NIR laser irradiation (2.3 W cm(-2)). These Fe3O4@C particles provided a superior photothermal therapeutic effect by intratumoral delivery and NIR irradiation of tumor xenografts. These results demonstrate that one-pot synthesis of carbon-coated magnetic particles could provide promising materials for future clinical applications and encourage further investigation of this simple method.

Development of a simple bioelectrode for the electrochemical detection of hydrogen peroxide using Pichia pastoris catalase immobilized on gold nanoparticle nanotubes and polythiophene hybrid.

In this paper, a simple and innovative electrochemical hydrogen peroxide biosensor has been proposed using catalase (CATpp) derived from Pichia pastoris as bioelectrocatalyst. The model biocomponent was immobilized on gold nanoparticle nanotubes (AuNPNTs) and polythiophene composite using 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide and N-hydroxysuccinimide (EDC-NHS) coupling reagent. In this present work, we have successfully synthesized gold nanoparticles (AuNPs) by ultrasonic irradiation. The tubular gold nanostructures containing coalesced AuNPs were obtained by sacrificial template synthesis. The assembly of AuNPNTs onto the graphite (Gr) electrode was achieved via S-Au chemisorption. The latter was pre-coated with electropolymerized thiophene (PTh) to enable S groups to bind AuNPNTs. The combination of AuNPNTs-PTh, i.e., an inorganic-organic hybrid, provides a stable enzyme immobilization platform. The physical morphology of the fabricated biosensor Gr/PTh/AuNPNTs/EDC-NHS/CATpp was investigated using scanning electron microscopy and energy-dispersive microscopy. The analytical performance of the bioelectrode was examined using cyclic voltammetry, differential pulse voltammetry and chronoamperometry. Operational parameters such as working potential, pH, and thermal stability of the modified electrode were examined. The beneficial analytical characteristics of the proposed electrode were demonstrated. Our results indicate that the Gr/PTh/AuNPNTs/EDC-NHS/CATpp bioelectrode exhibits a wide linear range from 0.05 mM to 18.5 mM of H2O2, fast response time of 7 s, excellent sensitivity of 26.2 mA mM(-1) cm(-2), good detection limit of 0.12 µM and good Michaelis-Menten constant of 1.4 mM. In addition, the bioelectrode displayed good repeatability, high stability and acceptable reproducibility, which can be attributed to the AuNPNTs-PTh composite that provides a biocompatible micro-environment.

Hollow nitrogen-doped carbon spheres as efficient and durable electrocatalysts for oxygen reduction.

Hollow nitrogen-doped carbon spheres (HNCSs) were prepared by a facile method as non-precious catalysts for the oxygen reduction reaction (ORR). The HNCS catalysts exhibited ORR activity comparable with a commercial Pt/C catalyst and superior stability in alkaline electrolyte medium.