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Herein, we reported a green biosynthesis method of copper nanoparticles (CuNPs) at microwave irradiation condition by using pectin as a stabilizer and ascorbic acid as a reducing agent. Under the optimum conditions, CuNPs1 and 2 were synthesized under microwave times 0 and 3 min, respectively. Transmission electron microscope and scanning electron microscope (SEM) tests showed that CuNPs1 and 2 had irregular polygon particles with average diameters of 61.9 ± 19.4 and 40.9 ± 13.6 nm, respectively. Zeta potentials of CuNPs1 and 2 were -45.2 and -48.7 mV, respectively. X-ray diffraction, Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), and X-ray photoelectron spectroscopy techniques were used to characterize the properties of CuNPs. Furthermore, inhibition zone tests showed that CuNPs2 exhibited higher antimicrobial activities against Escherichia coli, Staphylococcus aureus, and Aspergillus japonicus than CuNPs1. The antibacterial activities were also studied by the bacterial growth kinetics in broth media, and CuNPs2 exhibited lower minimum bactericidal concentrations than CuNPs1.

Surfactant and microwave assisted extraction (S-MAE) was used for pectin extraction from orange peel. First, we optimized the conditions of microwave assisted extraction (MAE), e.g., irradiation time, liquid-to-solid ratio (LSR), and pH on pectin yield (PY), galacturonic acid (GA) content, and degree of esterification (DE) using a Box-Behnken design. Under optimal conditions (pH 1.2, 7.0 min, and 21.5 v/w LSR), we obtained a PY of 28.0 ± 0.5%, which was close to the predicted value (31.1%). Second, we analyzed the effect of surfactant on microwave extraction of pectin. Among the surfactants investigated, Tween-80 (8 g/L, w/v) increased PY by 17.0%. Compared with conventional solvent extraction, S-MAE is a novel and efficient method for pectin extraction, which generated a higher (p < 0.05) PY (32.8%), GA content (78.1%), DE (69.8%), and M w (286.3 kDa)., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

Biodegradable sponges are currently attracting significant attention; however, the development of safe materials with high levels of antimicrobial activity remains a major challenge. Doping with silver nanoparticles (AgNPs) can effectively solve this problem. In this study, pectin sponges (PE-S) and nano-silver pectin sponges (PE-S/Ag) were synthesized in situ by using the freeze-drying method. The prepared sponge samples were then characterized with various tools. UV‒Vis spectroscopy was used to investigate the in situ synthesis of the AgNPs, FT-IR spectroscopy and XPS were used to investigate changes in the functional groups of the sponge samples, and SEM images were used to confirm the homogeneous distribution of AgNPs in the PE-S/Ag sponge. Our results suggested that the physical and chemical properties of the PE-S/Ag sponges were better than those of the PE-S sponges. The water absorption levels of the PE-S/Ag and PE-S sponges were three times and twice as high as that of gauze, respectively. Antibacterial tests showed that the minimum inhibitory concentrations of the PE-S/Ag sponge were 42 and 83 µg/mL against Escherichia coli and Staphylococcus aureus, respectively. Cytotoxicity and coagulation assays showed that the two sponge samples were nontoxic to cells and had good coagulation effects. The silver ion (Ag+) release assay was used to analyse the pattern of Ag+ release from the PE-S/Ag sponges. [ABSTRACT FROM AUTHOR]

Silver nanoparticles (AgNPs) were widely used in the antibacterial field because of their excellent antibacterial properties. In this study, we used hesperidin and pectin as reductants and stabilizers, and prepared uniform and stable Hesperidin-Pectin AgNPs (HP-AgNPs) by a simple microwave-assisted process. Increasing the proportion of hesperidin, P-AgNPs, HP-AgNPs1, HP-AgNPs2 and H-AgNPs were obtained respectively. With the increase of hesperidin ratio, the mean particle size and zeta potential increased gradually. Fourier transform infrared spectroscopy (FTIR) analysis showed that Ag+ was reduced by hesperidin and pectin. Antibacterial tests showed that HP-AgNPs2 showed the MIC values of 66.7 μg/mL against E. coli. In addition, HP-AgNPs2 was selected to clarify its antibacterial mechanism against E. coli. Morphological experiments showed that HP-AgNPs2 stress caused damage to the cell wall of E. coli , as well as leakage of its contents and an increase in reactive oxygen species (ROS). On the other hand, the release of Ag+ during cell co-culture was studied and the results showed that most of the Ag+ released was taken up by E. coli. The synergistic effect of hesperidin and pectin resulted in a significant enhancement of the antibacterial properties of AgNPs. These preliminary data suggest that HP-AgNPs has good antibacterial activity and may be developed as an effective antibacterial nanomaterial. • Synergistic preparation of silver nanoparticles from hesperidin and pectin. • The synergistic effect enhances the antibacterial effect of nanosilver effectively. • The action of nano‑silver on bacteria leads to the destruction of their cell walls and leakage of their contents. • Most of the Ag+ released by nanosilver is absorbed by E. coli. [ABSTRACT FROM AUTHOR]

Highlights • Ag NPs were prepared by the reaction of silver nitrate with alkali hydrolyzed pectin at microwave irradiation. • Small size spherical Ag NPs were produced with average sizes of 2.9 nm and 11.9 nm depending on microwave time. • Obtained Ag NPs colloidal solution were well stable with Zeta potential of near −40 mV. • MICs of Ag NPs against both E. coli and S. aureus were equally at 80–160 µg/ml. Abstract In this work, monodispersed silver nanoparticles (Ag NPs) were prepared by the reaction of silver nitrate with alkali hydrolyzed pectin at microwave irradiation. Two types of Ag NPs were obtained under the following conditions: 400 W of microwave power, 1 g/l NaOH, 2 g/l pectin, 10 mmol/l AgNO 3 , and irradiation time for 1 and 2 min, respectively. The zeta potential values of Ag NPs colloidal solutions were −39.6 and −38.7 mV, indicating that these nanoparticles were stable. Transmission electron microscopy (TEM) analysis revealed these spherical Ag NPs with an average size 2.90 and 11.94 nm, respectively. Ag NPs exhibited potent antibacterial and antifungal activities to against Escherichia coli , Staphylococcus aureus , and Aspergillus japonicus , and the minimum bactericidal concentrations (MIC) to against E. coli and S. aureus were equally at 80–160 µg/ml. In a word, this is a green, efficient, and cost-effective method for Ag NPs synthesis. [ABSTRACT FROM AUTHOR]