Reuse of used paper egg carton boxes as a source to produce hybrid AgNPs- carboxyl nanocellulose through bio-synthesis and its application in active food packaging

The proper disposal of disposable synthetic plastic food packaging materials presents a significant challenge for both the environment and the solid waste management community. To address this issue, an antibacterial-based high-strength bio-composite serves as the optimal alternative to conventional packaging materials. This study aims to produce a hybrid material of AgNPs-carboxyl cellulose nanocrystals (AgNPs-CCNCs), obtained from used egg carton boxes (UECBs), through bio acid hydrolysis and an in-situ generation process. Furthermore, AgNPs- carboxyl cellulose nanofibers (AgNPs-CCNFs) will be synthesized through a combination of bio acid hydrolysis and ball milling, followed by an additional in-situ generation step. The AgNPs-carboxyl nanocellulose (AgNPs-CCNCs, and AgNPs-CCNFs) exhibited excellent crystallinity index, morphology, thermal, and antibacterial properties. The morphological analysis was performed by electron microscopy, and the results showed the uniform distribution and spherical form of AgNPs appearing over the carboxyl nanocellulose through the in-situ generation process, which was confirmed through XRD analysis. The study further explores the impact of AgNPs-carboxyl nanocellulose on the mechanical, chemical, antibacterial, and thermal properties of the PVA matrix. The results demonstrate that the bio-nanocomposite film offers opportunities for utilization in active packaging applications.

Plasmonic Nano Silver: An Efficient Colorimetric Sensor for the Selective Detection of Hg2+ Ions in Real Samples

Environmental pollution caused by heavy metal ions has become a major health problem across the world. In this study, a selective colorimetric sensor based on starch functionalized silver nanoparticles (St-Ag NPs) for rapid detection of Hg2+ in real samples was developed. The environmentally friendly green approach was utilized to synthesize starch functionalized silver nanoparticles (St-AgNPs). A multi-technique approach involving UV-Vis absorption spectroscopy, Fourier transform infrared (FT-IR), X-ray diffraction (XRD), and scanning electron microscope (SEM) was used for the characterization of St-Ag NPs. These starch functionalized AgNPs were tested for the detection of heavy metals at 25 °C. The screening process revealed clear changes in the AgNPs color and absorption intensity only in the presence of Hg2+ due to the redox reaction between Ag0 and Hg2+. The color and absorption intensity of nanoparticles remain unchanged in the presence of all the other tested metals ion. The proposed method has strong selectivity and sensitivity to Hg2+ ions, with a detection limit of 1 ppm revealed by UV-visible spectrophotometry. The proposed procedure was found to be successful for the detection of Hg2+ in real samples of tap water.

In situ synthesis of Ag NPs in the galactomannan based biodegradable composite for the development of active packaging films

The application of plastics in the food and agriculture industries as packaging materials is immense. However, the damage caused to the environment by accumulating such non-biodegradable plastics has led to the development of better alternatives. This has caused an increase in the use of synthetic polymers and proteins for the production of biodegradable films as an alternative to packaging plastics. In this study, a novel approach for the fabrication of homogenous and biodegradable films using PVA/galactomannan/gelatin (PGG) composite has been developed. The in-situ synthesis of silver nanoparticles (Ag NPs) was attained by hydrothermal reduction. The formation of Ag NPs within the PGG composite imparted substantial antimicrobial properties to the films. The optical properties of Ag NPs-PGG composite and its films were characterized using UV–vis spectrophotometry, Fourier transfer infrared spectroscopy (FTIR), and scanning electron microscope (SEM). The Ag NPs-PGG films were evaluated for their physical and mechanical properties and cytotoxicity and were found to have high tensile strength, flexibility and biocompatibility. The films were also subjected to an in-door soil burial test for 15 days and were observed to decompose rapidly. The developed Ag NPs-PGG composite films with bactericidal properties have potential use in food packaging and various biomedical applications.

Green Synthesis of Gold and Silver Nanoparticles Using Leaf Extract of Capsicum chinense Plant

So far, several studies have focused on the synthesis of metallic nanoparticles making use of extracts from the fruit of the plants from the genus Capsicum. However, as the fruit is the edible, and highly commercial, part of the plant, in this work we focused on the leaves, a part of the plant that is considered agro-industrial waste. The biological synthesis of gold (AuNPs) and silver (AgNPs) nanoparticles using aqueous extracts of root, stem and leaf of Capsicum chinense was evaluated, obtaining the best results with the leaf extract. Gold and silver nanoparticles synthesized using leaf extract (AuNPs-leaf and AgNPs-leaf, respectively) were characterized by UV-visible spectrophotometry (UV-Vis), Fourier Transform Infrared Spectroscopy with Attenuated Total Reflection (FTIR-ATR), X-ray Photoelectron Spectroscopy (XPS), Ultra Hight Resolution Scanning Electron Microscopy coupled to Energy-Dispersive X-ray spectroscopy (UHR-SEM-EDX) and Transmission Electron Microscopy (TEM), and tested for their antioxidant and antimicrobial activities. In addition, different metabolites involved in the synthesis of nanoparticles were analyzed. We found that by the use of extracts derived from the leaf, we could generate stable and easy to synthesize AuNPs and AgNPs. The AuNPs-leaf were synthesized using microwave radiation, while the AgNPs-leaf were synthesized using UV light radiation. The antioxidant activity of the extract, determined by ABTS, showed a decrease of 44.7% and 60.7% after the synthesis of the AuNPs-leaf and AgNPs-leaf, respectively. After the AgNPs-leaf synthesis, the concentration of polyphenols, reducing sugars and amino acids decreased by 15.4%, 38.7% and 46.8% in the leaf extract, respectively, while after the AuNPs-leaf synthesis only reducing sugars decreased by 67.7%. These results suggest that these groups of molecules are implicated in the reduction/stabilization of the nanoparticles. Although the contribution of these compounds in the synthesis of the AuNPs-leaf and the AgNPs-leaf was different. Finally, the AgNPs-leaf inhibited the growth of S. aureus, E. coli, S. marcescens and E. faecalis. All of them are bacterial strains of clinical importance due to their fast antibiotic resistance development.

Valorization of Brewery Wastes for the Synthesis of Silver Nanocomposites Containing Orthophosphate

Brewery wastes from stage 5 (Wort precipitate: BW5) and stage 7 (Brewer's spent yeast: BW7) were valorized for the synthesis of silver phosphate nanocomposites. Nanoparticles were synthesized by converting silver salt in the presence of brewery wastes at different temperatures (25, 50, and 80 °C) and times (10, 30, and 120 min). Unexpectedly, BW7 yielded Ag3PO4 nanoparticles with minor contents of AgCl and Ag metal (Agmet). Contrastingly, BW5 produced AgCl nanoparticles with minor amounts of Ag3PO4 and Agmet. Nanocomposites with different component ratios were obtained by simply varying the synthesis temperature and time. The morphology of the nanocomposites contained ball-like structures representative of Ag3PO4 and stacked layers and fused particles representing AgCl and Agmet. The capping on the nanoparticles contained organic groups from the brewery by-products, and the surface overlayer had a rich chemical composition. The organic overlayers on BW7 nanocomposites were thinner than those on BW5 nanocomposites. Notably, the nanocomposites exhibited high antibacterial activity against Escherichia coli ATCC 25922. The antibacterial activity was higher for BW7 nanocomposites due to a larger silver phosphate content in the composition and a thin organic overlayer. The growth of Agmet in the structure adversely affected the antimicrobial property of the nanocomposites.

Statistically Optimized Production of Saccharides Stabilized Silver Nanoparticles Using Liquid-Plasma Reduction Approach for Antibacterial Treatment of Water

Various conventional approaches have been reported for the synthesis of nanomaterials without optimizing the role of synthesis parameters. The unoptimized studies not only raise the process cost but also complicate the physicochemical characteristics of the nanostructures. The liquid–plasma reduction with optimized synthesis parameters is an environmentally friendly and low-cost technique for the synthesis of a range of nanomaterials. This work is focused on the statistically optimized production of silver nanoparticles (AgNPs) by using a liquid–plasma reduction process sustained with an argon plasma jet. A simplex centroid design (SCD) was made in Minitab statistical package to optimize the combined effect of stabilizers on the structural growth and UV absorbance of AgNPs. Different combinations of glucose, fructose, sucrose and lactose stabilizers were tested at five different levels (−2, −1, 0, 1, 2) in SCD. The effect of individual and mixed stabilizers on AgNPs growth parameters was assumed significant when p-value in SCD is less than 0.05. A surface plasmon resonance band was fixed at 302 nm after SCD optimization of UV results. A bond stretching at 1633 cm⁻¹ in FTIR spectra was assigned to C=O, which slightly shifts towards a larger wavelength in the presence of saccharides in the solution. The presence of FCC structured AgNPs with an average size of 15 nm was confirmed from XRD and EDX spectra under optimized conditions. The antibacterial activity of these nanoparticles was checked against Staphylococcus aureus and Escherichia coli strains by adopting the shake flask method. The antibacterial study revealed the slightly better performance of AgNPs against Staph. aureus strain than Escherichia coli.

Microplasma assisted synthesis of silver nanoparticles capped with PVA, PVP and Sucrose

Silver nanoparticles (Ag NPs) have been synthesized by exposing Ar gas microplasma to liquid solution containing Ag+ ions. Sucrose, Polyvinyl Alcohol (PVA) and Polyvinylpyrrolidone (PVP) were added separately as capping agents in aqueous solution to avoid agglomeration of Ag NPs. There are two main mechanism involved in this experiment (1). interaction of electrons from microplasma with Ag+ ions present in aqueous solution and (2). Control of Ag NPs size by capping agents by surrounding Ag NPs. We have performed a comparison of capping performance of Sucrose and PVA in terms of stability of Ag NPs with the help of Ultraviolet-Visible spectroscopy (UV-vis). X-ray diffraction (XRD) analysis of Ag NPs capped with PVA and Sucrose shows average crystal size of 25 nm and 60 nm respectively. Dynamic Light Scattering (DLS) analysis was employed to measure the size distribution of Ag NPs capped with Sucrose, PVA and PVP capping agents. DLS showed that PVA-capped Ag NPs formed are more uniform in size as compared to Sucrose-capped. Average size of Ag NPs measured from DLS is 65 nm when capped with PVA and 120 nm when capped with Sucrose. Fourier Transform Infrared Spectroscopy (FTIR) spectrum obtained have bands of wavenumbers corresponding to functional groups of Sucrose and PVA which are present around Ag NPs.

A review on the green and sustainable synthesis of silver nanoparticles and one-dimensional silver nanostructures

The significance of silver nanostructures has been growing considerably, thanks to their ubiquitous presence in numerous applications, including but not limited to renewable energy, electronics, biosensors, wastewater treatment, medicine, and clinical equipment. The properties of silver nanostructures, such as size, size distribution, and morphology, are strongly dependent on synthesis process conditions such as the process type, equipment type, reagent type, precursor concentration, temperature, process duration, and pH. Physical and chemical methods have been among the most common methods to synthesize silver nanostructures; however, they possess substantial disadvantages and short-comings, especially compared to green synthesis methods. On the contrary, the number of green synthesis techniques has been increasing during the last decade and they have emerged as alternative routes towards facile and effective synthesis of silver nanostructures with different morphologies. In this review, we have initially outlined the most common and popular chemical and physical methodologies and reviewed their advantages and disadvantages. Green synthesis methodologies are then discussed in detail and their advantages over chemical and physical methods have been noted. Recent studies are then reviewed in detail and the effects of essential reaction parameters, such as temperature, pH, precursor, and reagent concentration, on silver nanostructure size and morphology are discussed. Also, green synthesis techniques used for the synthesis of one-dimensional (1D) silver nanostructures have been reviewed, and the potential of alternative green reagents for their synthesis has been discussed. Furthermore, current challenges regarding the green synthesis of 1D silver nanostructures and future direction are outlined. To sum up, we aim to show the real potential of green nanotechnology towards the synthesis of silver nanostructures with various morphologies (especially 1D ones) and the possibility of altering current techniques towards more environmentally friendly, more energy-efficient, less hazardous, simpler, and cheaper procedures.

Food and Beverage Ingredients Induce the Formation of Silver Nanoparticles in Products Stored within Nanotechnology-Enabled Packaging

Nanotechnology-based packaging may improve food quality and safety, but packages manufactured with polymer nanocomposites (PNCs) could be a source of human dietary exposure to engineered nanomaterials (ENMs). Previous studies showed that PNCs release ENMs to foods predominantly in a dissolved state, but most of this work used food simulants like dilute acetic acid and water, leaving questions about how substances in real foods may influence exposure. Here, we demonstrate that food and beverage ingredients with reducing properties, like sweeteners, may alter exposure by inducing nanoparticle formation in foods contacting silver nanotechnology-enabled packaging. We incorporated 12.8 ± 1.4 nm silver nanoparticles (AgNPs) into polyethylene and stored media containing reducing ingredients in packages manufactured from this material under accelerated room-temperature and refrigerated conditions. Analysis of the leachates revealed that reducing ingredients increased the total silver transferred to foods contacting PNC packaging (by as much as 7-fold) and also induced the (re)formation of AgNPs from this dissolved silver during storage. AgNP formation was also observed when Ag⁺ was introduced to solutions of natural and artificial sweeteners (glucose, sucrose, aspartame), commercial beverages (soft drinks, juices, milk), and liquid foods (yogurt, starch slurry), and the amount and morphology of reformed AgNPs depended on the ingredient formulation, silver concentration, storage conditions, and light exposure. These results imply that food and beverage ingredients may influence dietary exposure to nanoparticles when PNCs are used in packaging applications, and the practice of using food simulants may in certain cases underpredict the amount of ENMs likely to be found in foods stored in these materials.

Green Synthesis, Characterization and Antimicrobial Evaluation of Silver Nanoparticles for an Intracanal Dressing

Green chemistry has been applied in different areas due to the growing demands for renewable processes and one of them is nanotechnology. The aim of this study was to characterize a formulation containing silver nanoparticles (AgNPs) produced by a green synthesis and to evaluate its antimicrobial activity. The formulation will be used as an intracanal dressing exploiting the AgNPs' antimicrobial properties, which are crucial to prevent infections and bacterial reinfections that can compromise endodontic treatments. In the green synthesis, silver nitrate was employed as the precursor salt, maltose as a reducing agent, and gelatin as a stabilizing agent. The formulation was prepared mixing 50 % of a liquid containing the AgNPs and 50 % of hydroxyethylcellulose gel at 1.5 % with proper evaluation of the process inherent parameters. Techniques such as molecular absorption spectrometry and dynamic light scattering were used in characterization step. The antimicrobial activity of the AgNPs against Escherichia coli ATCC 25922, Enterococcus faecalis NCTC 775, Pseudomonas aeruginosa ATCC 27853, Staphylococcus aureus ATCC 25923 and Streptococcus mutans ATCC 25175 was verified according to National Comittee for Clinical Laboratory Standards (NCCLS) by determining minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC). The obtained results indicated the formulation containing AgNPs produced by a green synthesis was properly characterized by the selected techniques. Furthermore, the formulation assessment proved that it is suitable for the proposal as well as it has potential to be used as an intracanal dressing since presented antimicrobial activity against all bacterial strains evaluated.

Silver nanoparticles-based plasmonic assay for the determination of sugar content in food matrices

A simple colorimetric assay for sugars (monosaccharides, polyols and disaccharides) quantification based on silver nanoparticles (AgNPs) formation is proposed. Sugars are able to form AgNPs reducing Ag⁺ and stabilizing the suspension. Since the driving force is not only chemical reduction, the optimized assay allows the determination of both "reducing" and "non-reducing" sugars with similar reactivity. The localized surface plasmon resonance (LSPR) absorption band with maximum wavelength centered at ≈ 430 nm (A₄₃₀) is used for the detection. Monosaccharides, disaccharides and polyols with different functional groups and structure have been investigated: D-(+)-glucose, D-(+)-galactose, D-(-)-fructose, sucrose, D-(+)-raffinose D-(+)-maltose, D-(+)-trehalose, D-mannitol, D-sorbitol, i-inositol, xylitol and D-(+)-xylose. The resulting AgNPs have been characterized by UV-Vis spectroscopy, dynamic light scattering (DLS) and transmission electron microscopy (TEM). The reactivity of monomers and polyols was found higher than the disaccharides. The AgNPs-based method was applied to the determination of the sugars content in soft drinks (n = 6) and apple extracts (n = 5). Sugars content (expressed as glucose equivalents) determined by the proposed assay resulted comparable to results obtained by ion chromatography (R = 0.994). Reproducibility (RSD ≤ 9.4%) and recovery values (from 86.1% to 117.7%) in food matrices were satisfactory. Moreover, the assay is selective vs. potentially interfering compounds found in food. Considering the assay time (10 min), the low cost of reagents, limited volumes of sample (5-100 μL), no use of organic solvents and low waste generation, this assay appears very promising for sugars content determination.

Comparative antibacterial activity of silver nanoparticles synthesised by biological and chemical routes with pluronic F68 as a stabilising agent

The authors report the comparative antibacterial activity of silver nanoparticles synthesised by biological (using Fusarium oxysporum) and chemical routes in the presence and absence of pluronic F68 as a stabilising agent. The production of silver nanoparticles was evidenced by UV-visible spectra, with absorbance at about 420 nm in the case of both biological and chemical synthesis. X-ray diffraction pattern confirmed the presence of face-centred cubic structure (FCC plane). The nanoparticles characterised by transmission and scanning electron microscopy showed spherical silver nanoparticles with size range of 5-40 and 10-70 nm in the case of biologically and chemically synthesised nanoparticles, respectively. Addition of pluronic F68 showed the stabilisation of silver nanoparticles. Antibacterial efficacy of silver nanoparticles demonstrated different inhibitory activity against Escherichia coli, Pseudomonas aeruginosa and Staphylococcus aureus. Overall, biologically synthesised silver nanoparticles showed higher activity as compared with chemically synthesised nanoparticles. Silver nanoparticles synthesised in the presence of pluronic F68 by the chemical route exhibited synergism in antibacterial activity as compared with those synthesised without pluronic F68. On the contrary, biogenic silver nanoparticles without pluronic F68 showed higher antibacterial potential.

Design and evaluation of an apta-nano-sensor to detect Acetamiprid in vitro and in silico

Pesticide detection is a main concern of food safety experts. Therefore, it is urgent to design an accurate, rapid, and cheap test. Biosensors that detect pesticide residues could replace current methods, such as HPLC or GC-MC. This research designs a biosensor based on aptamer (Oligonucleotide ss-DNA) in the receptor role, silver nanoparticles (AgNPs) as optical sensors and salt (NaCl) as the aggregative inducer of AgNPs to detect the presence of Acetamiprid. After optimization, .6 μM aptamer and 100 mM salt were employed. The selectivity and sensitivity of the complex were examined by different pesticides and different Acetamiprid concentrations. To simulate in vitro experimental conditions, bioinformatics software was used as in silico analysis. The results showed the detection of Acetamiprid at the .02 ppm (89.8 nM) level in addition to selectivity. Docking outputs introduced two loops as active sites in aptamer and confirmed aptamer-Acetamiprid bonding. Circular dichroism spectroscopy (CD) confirmed upon Acetamiprid binding, aptamer was folded due to stem-loop formation. Stability of the Apt-Acetamiprid complex in a simulated aqueous media was examined by molecular dynamic studies.

Phoenix dactylifera (date palm) pit aqueous extract mediated novel route for synthesis high stable silver nanoparticles with high antifungal and antibacterial activity

The biological synthesis of silver nanoparticles (AgNPs) was conducted using date palm pit aqueous extract. The first visible sign of the synthesis of AgNPs was the change in colour of reaction mixtures from yellowish to reddish brown. The resulting synthesised AgNPs were characterised using UV-visible spectroscopy, X-ray diffraction (XRD), transmission electron microscopy (TEM) and dynamic light scattering (DLS). The UV-visible spectra gave surface plasmon resonance at 428 nm. XRD confirmed that the silver particles formed in our experiments were in the form of nanocrystals. TEM images revealed the formation of AgNPs with spherical shape and sizes in the range between 1-40 nm. DLS showed nanoparticles with an average size of 27 nm. Fourier transform infrared spectroscopy indicated the role of different possible functional groups (carboxyl, amine, aromatic and hydroxyl) in the formation of AgNPs. AgNPs were stable at 28°C in vitro for over a year without any precipitation or decreased production of antimicrobial effect. Then, the antifungal and antibacterial activities of synthesised AgNPs were investigated. The synthesised AgNPs showed significant inhibitory effects on Rhizoctonia solani (AG2_2) cultures, so that the concentration of 25 µg/ml prevented approximately 83% of the mycelium growth of the fungus. Then, the broth macro-dilution method was used for examining antibacterial effect of AgNPs. The minimum inhibitory concentration and minimum bactericide concentration against Klebsiella pneumonia (PCI 602) and Acinetobacter baumannii (ATCC 19606) were recorded as 1.56 and 3.12 µg/ml AgNPs, respectively.

Neurite outgrowth stimulatory effects of myco synthesized AuNPs from Hericium erinaceus (Bull.: Fr.) Pers. on pheochromocytoma (PC-12) cells

Background

Hericium erinaceus has been reported to have a wide range of medicinal properties such as stimulation of neurite outgrowth, promotion of functional recovery of axonotmetic peroneal nerve injury, antioxidant, antihypertensive, and antidiabetic properties. In recent years, the green synthesis of gold nanoparticles (AuNPs) has attracted intense interest due to the potential use in biomedical applications. The aim of this study was to investigate the effects of AuNPs from aqueous extract of H. erinaceus on neurite outgrowth of rat pheochromocytoma (PC-12) cells.

Methods

The formation of AuNPs was characterized by UV–visible spectrum, energy dispersive X-ray (EDX), field-emission scanning electron microscope (FESEM), transmission electron microscopy (TEM), particle size distribution, and Fourier transform-infrared spectroscopy (FTIR). Furthermore, the neurite extension study of synthesized AuNPs was evaluated by in vitro assay.

Results

The AuNPs exhibited maximum absorbance between 510 and 600 nm in UV–visible spectrum. FESEM and TEM images showed the existence of nanoparticles with sizes of 20–40 nm. FTIR measurements were carried out to identify the possible biomolecules responsible for capping and efficient stabilization of the nanoparticles. The purity and the crystalline properties were confirmed by EDX diffraction analysis, which showed strong signals with energy peaks in the range of 2–2.4 keV, indicating the existence of gold atoms. The synthesized AuNPs showed significant neurite extension on PC-12 cells. Nerve growth factor 50 ng/mL was used as a positive control. Treatment with different concentrations (nanograms) of AuNPs resulted in neuronal differentiation and neuronal elongation. AuNPs induced maximum neurite outgrowth of 13% at 600 ng/mL concentration.

Conclusion

In this study, the AuNPs synthesis was achieved by a simple, low-cost, and rapid bioreduction approach. AuNPs were shown to have potential neuronal differentiation and stimulated neurite outgrowth. The water-soluble bioconstituents could be responsible for the neuroactivity. This is the first report for the biosynthesis of AuNPs using the hot aqueous extract of H. erinaceus.