Silver Nanoparticles on Cellulose Surfaces: Quantitative Measurements

Optimized Incorporation of Silver Nanoparticles onto Cotton Fabric Using k-Carrageenan Coatings for Enhanced Antimicrobial Properties

The incorporation of bactericidal properties into textiles is a widely sought-after aspect, and silver nanoparticles (AgNPs) can be used for this. Here, we evaluate a strategy for incorporating AgNPs into a cotton fabric. For this purpose, a bactericidal textile coating based on a composite of AgNPs and kappa-carrageenan (k-CA) was proposed. The composite was obtained by heating the silver precursor (AgNO3) directly in k-CA solution for green synthesis and in situ AgNPs stabilization. Cotton substrates were added to the heated composite solution for surface impregnation and hydrogel film formation after cooling. Direct synthesis of AgNPs on a fabric was also tested. The results showed that the application of a coating based on k-CA/AgNPs composite can achieve more than twice the silver loading on the fabric surface compared to the textile subjected to direct AgNPs incorporation. Furthermore, silver release tests in water showed that higher Ag+ levels were reached for k-CA/AgNPs-coated cotton. Therefore, inoculation tests with the bacteria Staphylococcus aureus (SA) using the agar diffusion method showed that samples covered with the composite resulted in significantly larger inhibition halos. This indicated that the use of the composite as a coating for cotton fabric improved its bactericidal activity against SA.

A new design of colorimetric films using bacterial cellulose nanocrystals derived from nata de coco for sensing volatile organic compounds

In this work, bacterial cellulose (BC) derived from Nata de Coco is a polysaccharide material, and it is further processed into bacterial cellulose nanocrystal (BCNC) via acid hydrolysis. Then BCNC is doped with transition metals to enhance its amine/hydrogen sulfide response. Therefore, the aim of this study is to investigate the use of transition metals as indicators to detect amine and hydrogen sulfide gas for efficiently monitoring food spoilage. BCNCs were treated with various concentrations of silver nitrate (AgNO3) and copper sulfate pentahydrate (CuSO4·5H2O). Then the dropwise addition of ascorbic acid was applied to reduce Ag+ and Cu2+ to Ag0 (silver nanoparticle) and Cu0 (copper nanoparticle), which refer to red brown and red wine colors, respectively. The results indicated that BCNC/Ag nanoparticles were spherical, while BCNC/Cu nanoparticles exhibited a rod-like structure. XRD results also presented the incorporation of Ag and Cu nanoparticles, as confirmed by both crystallography structures. Furthermore, UV-Vis spectra showed the adsorption bands at 422-430 nm and 626-629 nm, belonging to Ag and Cu nanoparticles. After H2S and ammonia gas exposure, BH/Ag and BH/Cu films turned black from brown and red. In conclusion, transition metal-doped BCNCs exhibit potential for innovative food spoilage gas sensors.

Polyurethane and cellulose acetate micro-nanofibers containing rosemary essential oil, and decorated with silver nanoparticles for wound healing application

In this study, polyurethane (PU) and cellulose acetate (CA) electrospun fibers encapsulating rosemary essential oil (REO) and adsorbed silver (Ag) nanoparticles (NPs) were fabricated. The biologically inspired materials were analyzed for physicochemical characteristics using scanning electron microscopy, X-ray diffractometer, Fourier transform infrared, thermal gravimetric analysis, X-ray photoelectron spectroscopy, water contact angle, and water uptake studies. Results confirmed the presence of CA and Ag NPs on the PU micro-nanofibers increased the hydrophilicity from 107.1 ± 0.36^o to 26.35 ± 1.06^o. The water absorption potential increased from 0.07 ± 0.04 for pristine PU fibers to 12.43 ± 0.49 % for fibers with 7 wt% of CA, REO, and Ag NPs. The diffractometer confirmed the 2θ of 38.01°, 44.13^o, and 64.33^o, corresponding to the diffraction planes of Ag on the fibers. The X-ray photoelectron spectroscopy confirmed microfibers interfacial chemical interaction and surface changes due to CA, REO, and Ag presence. The inhibition tests on Staphylococcus aureus and Escherichia coli indicated that composites are antibacterial in activity. Moreover, synergistic interactions of REO and Ag NPs resulted in superior antibacterial activity. The cell viability and attachment assay showed improved hydrophilicity of the fibers, which resulted in better attachment of cells to the micro-nanofibers, similar to the natural extracellular matrix in the human body.

Fluoroplast Doped by Ag2O Nanoparticles as New Repairing Non-Cytotoxic Antibacterial Coating for Meat Industry

Foodborne infections are an important global health problem due to their high prevalence and potential for severe complications. Bacterial contamination of meat during processing at the enterprise can be a source of foodborne infections. Polymeric coatings with antibacterial properties can be applied to prevent bacterial contamination. A composite coating based on fluoroplast and Ag₂O NPs can serve as such a coating. In present study, we, for the first time, created a composite coating based on fluoroplast and Ag₂O NPs. Using laser ablation in water, we obtained spherical Ag₂O NPs with an average size of 45 nm and a ζ-potential of -32 mV. The resulting Ag₂O NPs at concentrations of 0.001-0.1% were transferred into acetone and mixed with a fluoroplast-based varnish. The developed coating made it possible to completely eliminate damage to a Teflon cutting board. The fluoroplast/Ag₂O NP coating was free of defects and inhomogeneities at the nano level. The fluoroplast/Ag₂O NP composite increased the production of ROS (H₂O₂, OH radical), 8-oxogualnine in DNA in vitro, and long-lived active forms of proteins. The effect depended on the mass fraction of the added Ag₂O NPs. The 0.01-0.1% fluoroplast/NP Ag₂O coating exhibited excellent bacteriostatic and bactericidal properties against both Gram-positive and Gram-negative bacteria but did not affect the viability of eukaryotic cells. The developed PTFE/NP Ag₂O 0.01-0.1% coating can be used to protect cutting boards from bacterial contamination in the meat processing industry.

Hybrid nanolayers of star polymers and silver nanoparticles with antibacterial activity

The aim of this study was to obtain stable star polymer layers with incorporated silver nanoparticles (AgNPs) and to study the antimicrobial activity of these hybrid materials. In this work, a novel approach regarding the synthesis of AgNPs directly by the star polymer layer is presented. Nanolayers of poly(N,N'-dimethylaminoethyl methacrylate) and hydroxyl-bearing poly[oligo(ethylene glycol) methacrylate] (P(DMAEMA-co-OEGMA-OH)) stars, covalently bound with solid supports, were obtained through chemical reaction of hydroxyl groups in the star arms with substrate modified with imidazole derivative. Quantitative chemical composition analysis and tracking of the changes in the morphology and wettability after every step of surface modification confirmed the covalent attachment of stars with the support. In the next step, the polymer nanolayers were modified with AgNPs formed in situ using only amine groups of the star arms and followed by the crystal quartz microbalance (QCM). The analysis of the layer thickness and affinity to water, both with the shape, size and amount of silver incorporated into the layer, confirmed the efficacy of AgNPs formation. The amount of silver incorporated into layers was correlated with the molar masses of the grafted stars, and a possible location of AgNPs within layers was shown. The antibacterial activity tests of prepared nanolayers showed that obtained hybrid materials were highly effective against both gram-positive and gram-negative bacteria strains. This study shows that the obtained layers are promising as stable coatings for antibacterial applications.

Antibacterial efficacy of facile cyanobacterial silver nanoparticles inferred by antioxidant mechanism

Nanoparticles (NPs) have gained importance in technological advances owing to their user friendly enhanced and efficient physical, chemical, and biological characteristics compared to their bulk counterparts. Biological synthesis of NPs by using a microorganism, enzymes, or plant extracts offers a greener and eco-friendly approach besides many advantages over physical or chemical approaches. This study reports the biosynthesis of silver nanoparticles (AgNPs) using Nostoc muscorum NCCU 442 aqueous extract as the reducing and capping agent for AgNPs synthesis. The synthesized nanoparticles were characterized by UV-VIS spectrum, SEM, EDS, TEM, AFM, DLS and XRD. Results showed distinguishing polycrystalline nature of synthesized AgNPs with surface plasmon significant band in the size range of 6-45nm with average 30 size nm. FT-IR study revealed the role of secondary metabolites present in aqueous extract for the synthesis of AgNPs. Biological activities of purified AgNPs as antioxidant and antibacterial potential showed the highest antibacterial activity against Staphylococcus aureus MTCC 902.

Functionalization of biopolymer fibers with magnetic nanoparticles

Hybrid fibers consisting of biopolymers and inorganic nanoparticles are receiving increasing attention due to their unique properties. Commonly, the nanoparticles are chosen for their intrinsic properties such as magnetic, thermal, or electrical conductivity. The biopolymer component of the hybrid fiber is chosen for its mechanical properties and ability to act as a scaffold or matrix for the nanoparticles. While there are many fiber-forming synthetic polymers, there has been a recent interest in replacing these systems with biopolymers due to their sustainability, biocompatibility, nontoxicity, and biodegradability. Fibers made from biopolymers have one additional benefit over synthetic polymers as they make good scaffolds for embedding nanoparticles without the need of any additional bonding agents. In particular, naturally occurring biopolymers such as proteins exhibit a myriad of interactions with nanoparticles, including ionic, H-bonding, covalent, Van der Waals, and electrostatic interactions. The diverse range of interactions between magnetic nanoparticles and biopolymers makes resulting hybrid fibers of particular interest as magnetic-responsive materials. Magnetically responsive hybrid biopolymer fibers have many features, including enhanced thermal stabilities, strong mechanical toughness, and perhaps most interestingly multifunctionality, allowing for a wide range of applications. These applications range from biosensing, filtration, UV shielding, antimicrobial, and medical applications, to name a few. Here, we review established hybrid fibers consisting of biopolymers and nanoparticles with a primary focus on biopolymers doped with magnetic nanoparticles and their various putative applications.

Biogenic Ag Nanoparticles from Neem Extract: Their Structural Evaluation and Antimicrobial Effects against Pseudomonas nitroreducens and Aspergillus unguis (NII 08123)

Silver nanocrystals have been successfully fabricated by the bioreduction route using the ethanolic extract of Azadirachta indica (neem) leaves as the reducing and capping agent without solvent interference. The silver nanocrystals were grown in a single-step method, without the influence of external energy or surfactants, and at room temperature. The nanoparticles were prepared from different ratios of silver ions to reducing agent molecules and were characterized by UV-vis spectroscopy and transmission electron microscopy (TEM). The nanoparticles were roughly spherical and polydispersed with diameters of less than 40 nm, as determined with high-resolution transmission electron microscopy (HRTEM). Fast Fourier transform (FFT) analysis and X-ray diffraction (XRD) analysis elucidated the crystalline nature of the nanoparticles. The presence of participating functional groups was determined with Fourier transform infrared (FTIR) spectroscopy. The synthesized silver nanoparticles were analyzed as a potential surface-enhanced Raman spectroscopy (SERS) substrate by incorporating rhodamine B as the Raman reporter molecule. The bioreduction process was monitored through SERS fingerprint, which was evaluated by the change in vibrational energies of metal-ligand bonds. It was possible to detect the SERS spectral pattern of the probe molecules on the Ag nanoparticles without the use of any aggregating agent. Thus, the formation of probable intra- and interparticle hot spots was attributed to evaporation-induced aggregation. Furthermore, stirring and precursor salt concentration influenced the kinetics involved in the fabrication process. The thermal stability of the lyophilized nanoparticles prepared from 0.1 M AgNO₃ was evaluated with thermogravimetric analysis (TGA) and had a residual mass of 60% at 600 °C. X-ray photoelectron spectroscopy (XPS) studies were used to validate the compositional and chemical-state information. The biomass-capped silver nanoparticles provided antimicrobial activity by inhibiting the growth of Pseudomonas nitroreducens, a biofilm-forming bacterium, and the fungus, Aspergillus unguis (NII 08123).