Polyvinylpyrrolidone (PVP) is employed in several potential applications, relying of its special chemical and physical properties in addition to its low toxicity and biocompatibility. The aim of this work is to prepare polyvinylpyrrolidone-silver (PVP-Ag) nanocomposite with high inhibiting effect on the microbial growth and low cytotoxicity. In situ prepared small stable spherical silver nanoparticles, with narrow range particle size distribution, were obtained by easy, economical and rapid chemical reduction method. Silver ions were reduced to silver nanoparticles using low amount of sodium borohydride (NaBH4) as a strong reducing agent. PVP-Ag nanocomposite was prepared using PVP as a stabilizing and capping agent. Formation of the spherical silver nanoparticles with mean particle size 5 nm was confirmed by ultraviolet-visible spectroscopy, high resolution transmission electron microscopy, and dynamic light scattering. The inhibiting growth effect of the nanocomposite toward Gram-positive bacteria (Staphylococcus aureus), Gram-negative bacteria (Pseudomonas aeruginosa), and yeast fungus (Candida albicans) were studied. The cytotoxicity of the nanocomposite against BJ1 normal skin fibroblast cell line was tested. Results of this work presented perfect antimicrobial activity of the PVP-Ag nanocomposite towards bacteria and fungi with low cytotoxicity, which may lead to promising applications in skin wound healing.

Several materials such as silver are used to enhance graphene oxide (GO) sheets antimicrobial activity. However, these toxic materials decrease its biocompatibility and hinder its usage in many biological applications. Therefore, there is an urgent need to develop nanocomposites that can preserve both the antimicrobial activity and biocompatibility simultaneously. This work highlights the importance of functionalisation of GO sheets using Polyvinylpyrrolidone (PVP) and decorating them with silver nanoparticles (AgNPs) in order to enhance their antimicrobial activity and biocompatibility at the same time. The structural and morphological characterisations were performed by UV-Visible, Fourier transform infrared (FTIR), and Raman spectroscopic techniques, X-ray diffraction (XRD), and high-resolution transmission electron microscopy (HR-TEM). The antimicrobial activities of the prepared samples against Staphylococcus aureus, Pseudomonas aeruginosa, and Candida albicans were studied. The cytotoxicity of prepared materials was tested against BJ1 normal skin fibroblasts. The results indicated that the decoration with AgNPs showed a significant increase in the antimicrobial activity of GO and FGO sheets, and functionalisation of GO sheets and GO-Ag nanocomposite with PVP improved the cell viability about 40 and 35%, respectively.

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This study provides the optimum preparation parameters of chitosan-silver nanoparticles composite (CSNC) with promising antibacterial activity against the most common bacterial infections found on burn wounds. CSNC was synthesised by simple green chemical reduction method with different preparation factors. Chitosan was used to reduce silver nitrate and stabilise silver nanoparticles in the medium. For this reason, spectroscopic and microscopic techniques as, ultraviolet-visible Fourier transform infrared spectroscopy and transmission electron microscopy were used in the study of the molecular and morphological properties of the resultant composites. Furthermore, the composite was assessed in terms of Ag-ions release by AAS and its efficacy as antibacterial material. As a result, CSNC showed stronger antibacterial effect than its individual components (chitosan and silver nitrate solutions) towards Gram-positive (Staphylococcus aureus) and Gram-negative (Pseudomonas aeruginosa and Escherichia coli) bacteria. CSNC prepared in this study showed highest inhibition percentage of bacterial growth up to 96% at concentration of 220 μg/ml.

The unit of Layer thickness that appears on the table 2 of section 4 must be replaced by (μm) not (μμm). These corrections and clarifications do not change any of the results and conclusions obtained in the paper. ORCID iDsDahi Ghareab Abdelsalam Ibrahim https:/ /orcid.org/0000-0002-4429-5096 H H A Sherif https:/ /orcid.org/0000-0001-9111-7893Abstract Terahertz (THz) rays have higher penetration depth compared to visible rays, and hence can be effectively used to measure a geometric thickness of soft samples with no damage. Measurement of such soft samples with contact methods is a challenge in terms of accuracy and speed. In this paper, a terahertz pulsed imaging(TPI) imaga 3000 system with reflection imaging module has been employed to measure the individual soft thickness of a multilayer structure made of adhesive soft polymer films with temporal method. Automatic scan of the sample has been carried out and the echoes at each interface are sampled and then detected. The complex refractive index (RI) of the sample has been measured with terahertz pulsed spectra (TPS) 3000 with transmission module. To avoid the incorrect thickness from the measured complex RI due to dispersion, propagation constants of the sample for a given mode and polarization have been extracted by solving the Helmholtz equation, numerically. From the detected delay of echoes and the calculated propagation constants, the geometric thickness of each layer is calculated. Further thickness of an onion leaf as a biological sample was measured based on the propagation constant. Results showed good accuracy with uncertainty budget of 7% of the THz wavelength used.