Sonochemical coating of paper by microbiocidal silver nanoparticles

Sono-processes: Emerging systems and their applicability within the (bio-)medical field

Sonochemistry, although established in various fields, is still an emerging field finding new effects of ultrasound on chemical systems and are of particular interest for the biomedical field. This interdisciplinary area of research explores the use of acoustic waves with frequencies ranging from 20 kHz to 1 MHz to induce physical and chemical changes. By subjecting liquids to ultrasonic waves, sonochemistry has demonstrated the ability to accelerate reaction rates, alter chemical reaction pathways, and change physical properties of the system while operating under mild reaction conditions. It has found its way into diverse industries including food processing, pharmaceuticals, material science, and environmental remediation. This review provides an overview of the principles, advancements, and applications of sonochemistry with a particular focus on the domain of (bio-)medicine. Despite the numerous benefits sonochemistry has to offer, most of the research in the (bio-)medical field remains in the laboratory stage. Translation of these systems into clinical practice is complex as parameters used for medical ultrasound are limited and toxic side effects must be minimized in order to meet regulatory approval. However, directing attention towards the applicability of the system in clinical practice from the early stages of research holds significant potential to further amplify the role of sonochemistry in clinical applications.

Fast and easy synthesis of silver, copper, and bimetallic nanoparticles on cellulose paper assisted by ultrasound

This work focuses on a systematic method to produce Ag, Cu, and Ag/Cu metallic nanoparticles (MNPs) in situ assisted with ultrasound on cellulose paper. By tuning the concentration of AgNO3 and CuSO4 salt precursors and ultrasound time, combined with a fixed concentration of ascorbic acid (AA) as a reducing agent, it was possible to control the size, morphology, and polydispersity of the resulting MNPs on cellulose papers. Notably, high yield and low polydispersity of MNPs and bimetallic nanoparticles are achieved by increasing the sonication time on paper samples pre-treated with salt precursors before reduction with AA. Moreover, mechanical analysis on paper samples presenting well-dispersed and distributed MNPs showed slightly decreasing values of Young's modulus compared to neat papers. The strain at break is substantially improved in papers containing solely Ag or Cu MNPs. The latter suggests that the elastic/plastic transition and deformation of papers are tuned by cellulose and MNPs interfacial interaction, as indicated by mechanical analysis. The proposed method provides insights into each factor affecting the sonochemistry in situ synthesis of MNPs on cellulose papers. In addition, it offers a straightforward alternative to scale up the production of MNPs on paper, ensuring an eco-friendly method.

Sonochemical treatment of packaging materials for prolonging fresh produce shelf life

Packaging bags made of polyethylene (PE) were sonochemically coated with edible antibacterial nanoparticles of chitosan (CS). In this work, the nanoparticles (NPs) were deposited on the surface of PE packaging bags by applying sonication waves on an acetic solution of chitosan. The characterization of CS NPs and PE bags was conducted by physicochemical techniques. The results showed that the coated bags had longer freshness than the uncoated ones. Furthermore, the characterization of cucumber, mushroom, and garlic placed into coated and uncoated PE bags was conducted by monitoring various parameters such as mass loss, total soluble solids, pH, and visual inspection. The study revealed that the PE bags coated with CS NPs showed a noticeable result in extending the shelf life of fresh produce. Finally, the antibacterial activity of PE bags was evaluated against various bacterial species. Hence, the PE bags coated with CS NPs could be a promising candidate for elongating the shelf life of packaged fresh produce.

Critical Review on Nutritional, Bioactive, and Medicinal Potential of Spices and Herbs and Their Application in Food Fortification and Nanotechnology

Medicinal or herbal spices are grown in tropical moist evergreen forestland, surrounding most of the tropical and subtropical regions of Eastern Himalayas in India (Sikkim, Darjeeling regions), Bhutan, Nepal, Pakistan, Iran, Afghanistan, a few Central Asian countries, Middle East, USA, Europe, South East Asia, Japan, Malaysia, and Indonesia. According to the cultivation region surrounded, economic value, and vogue, these spices can be classified into major, minor, and colored tropical spices. In total, 24 tropical spices and herbs (cardamom, black jeera, fennel, poppy, coriander, fenugreek, bay leaves, clove, chili, cassia bark, black pepper, nutmeg, black mustard, turmeric, saffron, star anise, onion, dill, asafoetida, celery, allspice, kokum, greater galangal, and sweet flag) are described in this review. These spices show many pharmacological activities like anti-inflammatory, antimicrobial, anti-diabetic, anti-obesity, cardiovascular, gastrointestinal, central nervous system, and antioxidant activities. Numerous bioactive compounds are present in these selected spices, such as 1,8-cineole, monoterpene hydrocarbons, γ-terpinene, cuminaldehyde, trans-anethole, fenchone, estragole, benzylisoquinoline alkaloids, eugenol, cinnamaldehyde, piperine, linalool, malabaricone C, safrole, myristicin, elemicin, sinigrin, curcumin, bidemethoxycurcumin, dimethoxycurcumin, crocin, picrocrocin, quercetin, quercetin 4'-O-β-glucoside, apiol, carvone, limonene, α-phellandrene, galactomannan, rosmarinic acid, limonene, capsaicinoids, eugenol, garcinol, and α-asarone. Other than that, various spices are used to synthesize different types of metal-based and polymer-based nanoparticles like zinc oxide, gold, silver, selenium, silica, and chitosan nanoparticles which provide beneficial health effects such as antioxidant, anti-carcinogenic, anti-diabetic, enzyme retardation effect, and antimicrobial activity. The nanoparticles can also be used in environmental pollution management like dye decolorization and in chemical industries to enhance the rate of reaction by the use of catalytic activity of the nanoparticles. The nutritional value, phytochemical properties, health advantages, and both traditional and modern applications of these spices, along with their functions in food fortification, have been thoroughly discussed in this review.

Fabrication of silver nanoparticles-deposited fabrics as a potential candidate for the development of reusable facemasks and evaluation of their performance

Recently, wearing facemasks in public has been raised due to the coronavirus disease 2019 epidemic worldwide. However, the performance and effectiveness of many existing products have raised significant concerns among people and professionals. Therefore, greater attempts have been focused recently to increase the efficacy of these products scientifically and industrially. In this respect, doping or impregnating facemask fabrics with metallic substances or nanoparticles like silver nanoparticles has been proposed. So, in the present study, we aimed to sonochemically coat silver nanoparticles on the non-woven Spunbond substrates at different sonication times and concentrations to develop antibacterial and antiviral facemask. The coated substrates were characterized using Field Emission Scanning Electron Microscope, Energy Dispersive X-Ray, X-ray diffraction, and Thermogravimetry analysis. The amount of silver released from the coated substrates was measured by atomic absorption spectroscopy. The filtration efficiency, pressure drop, and electrical conductivity of the coated samples were also investigated. The antibacterial activity of fabrics was evaluated against Escherichia coli and Staphylococcus aureus. Cellular viability of samples assessed by MTT and brine shrimp lethality tests. The results revealed that the higher sonication times and precursor concentrations result in a higher and more stable coating, larger particle size, wider particle size distribution, and lower content of released silver. Coated fabrics also revealed enhanced filtration efficiency (against nanosize particles), desired pressure drop, and antibacterial activity without significant cytotoxicity toward HEK 293 cells and Artemia nauplii. As a result, the coated fabrics could find potential applications in the development of facemasks for protection against different pathogenic entities.

Activation of Ibuprofen via Ultrasonic Complexation with Silver in N-Doped Oxidized Graphene Nanoparticles for Microwave Chemotherapy of Cervix Tumor Tissues

An ultrasonic method (20 kHz) is introduced to activate pristine ibuprofen organic molecular crystals via complexation with silver in nitrogen-doped oxidized graphene nanoplatforms (∼50 nm). Ultrasonic complexation occurs in a single-step procedure through the binding of the carboxylic groups with Ag and H-bond formation, involving noncovalent π_C=C → π_C=C* transitions in the altered phenyl ring and π_PY → π_CO* in ibuprofen occurring between the phenyl ring and C-O bonds as a result of interaction with hydroxyl radicals. The ibuprofen-silver complex in ≪NrGO≫ exhibits a ∼42 times higher acceleration rate than free ibuprofen of the charge transfer between hexacyanoferrate and thiosulfate ions. The increased acceleration rate can be caused by electron injection/ejection at the interface of the ≪Ag-NrGO≫ nanoplatform and formation of intermediate species (Fe(CN)₅(CNSO₃)^x- with x = 4 or 5 and AgHS₂O₃) at the excess of produced H⁺ ions. Important for microwave chemotherapy, ibuprofen-silver complexes in the ≪NrGO≫ nanoplatform can produce H⁺ ions at ∼12.5 times higher rate at the applied voltage range from 0.53 to 0.60 V. ≪Ibu-Ag-NrGO≫ NPs develop ∼10⁵ order higher changes of the electric field strength intensity than free ibuprofen in the microwave absorption range of 100-1000 MHz as revealed from the theoretical modeling of a cervix tumor tissue.

Making salty cucumbers and honeyed apples by applying the sonochemical method

Sonochemistry was applied in the last few years for coating surfaces of various substrates for imparting desired properties to the surface. In the current paper the coating of cucumbers with NaCl nanoparticles and apples with honey nanoparticles was accomplished by applying the sonochemical method. In both coating the nanoparticles were deposited from aqueous solutions. The products were characterized by Inductively coupled plasma, Dynamic light scattering, Scanning electron microscopy, and Nuclear magnetic resonance.

Paper-based plasmonic substrates as surface-enhanced Raman scattering spectroscopy platforms for cell culture applications

The engineering of advanced materials capable of mimicking the cellular micro-environment while providing cells with physicochemical cues is central for cell culture applications. In this regard, paper meets key requirements in terms of biocompatibility, hydrophilicity, porosity, mechanical strength, ease of physicochemical modifications, cost, and ease of large-scale production, to be used as a scaffold material for biomedical applications. Most notably, paper has demonstrated the potential to become an attractive alternative to conventional biomaterials for creating two-dimensional (2D) and three-dimensional (3D) biomimetic cell culture models that mimic the features of in vivo tissue environments for improving our understanding of cell behavior (e.g. growth, cell migration, proliferation, differentiation and tumor metastasis) in their natural state. On the other hand, integration of plasmonic nanomaterials (e.g. gold nanoparticles) within the fibrous structure of paper opens the possibility to generate multifunctional scaffolds equipped with biosensing tools for monitoring different cell cues through physicochemical signals. Among different plasmonic based detection techniques, surface-enhanced Raman scattering (SERS) spectroscopy emerged as a highly specific and sensitive optical tool for its extraordinary sensitivity and the ability for multidimensional and accurate molecular identification. Thus, paper-based plasmonic substrates in combination with SERS optical detection represent a powerful future platform for monitoring cell cues during cell culture processes. To this end, in this review, we will describe the different methods for fabricating hybrid paper-plasmonic nanoparticle substrates and their use in combination with SERS spectroscopy for biosensing and, more specifically, in cell culture applications.

Development of a Benzalkonium Chloride Based Antibacterial Paper for Health and Food Applications

Pathogenic bacteria and other microorganisms pose a potent threat to humans by causing various infectious diseases. To control the spread of infection, different antibacterial products have been developed. However, most of them are known to be associated with health hazards, environmental pollution, complex fabrication, and/or higher cost. To address these issues, in this study, a low cost, biodegradable and human skin compatible antibacterial paper has been developed. A quaternary ammonium compound, benzalkonium chloride (BKC) has been used for paper surface treatment. The concentration of aqueous solution of BKC coated on paper was varied from 0.1 wt% to 0.2 wt%. No external binder was required for coating BKC onto paper. The efficacy of the coated paper was investigated against Staphylococcus aureus ATCC 6538 and Escherichia coli ATCC 8739 bacterial strains. This antibacterial paper is highly effective against both strains with the concentrations of BKC being within the allowable limit for cytotoxic effects. The optimum concentration of BKC coated on paper can be considered as 0.15 wt%, as nearly 100% inhibition was achieved with it against both strains. The developed antibacterial paper is suitable for being used in the industry for disinfection and food packaging purposes, and also by the public for hand sanitization.

Silver Nanoparticle Production by Ruta graveolens and Testing Its Safety, Bioactivity, Immune Modulation, Anticancer, and Insecticidal Potentials

Ruta graveolens, a plant belonging to the family Rutaceae, is traditionally used as a medicinal plant and a flavoring agent in food. This work aimed to prepare silver nanoparticles (AgNPs) using the ethanol extract from R. graveolens leaves and test different biological activities as well as insecticidal potentials in the extract and extract prepared AgNPs. Dried and powdered R. graveolens leaves were subjected to extraction using ethanol, and this extract was used to synthesize AgNPs. AgNP synthesis was monitored by the change in color, UV spectrophotometry, and electron microscopy (scanning). Fourier transform infrared (FT-IR) spectroscopy was used to monitor the functional groups in the extracts. Immunological, physiological, anticancer, antibacterial, and insecticidal potentials of the extract and its prepared AgNPs were tested. Results showed the ability of the leaf extract to synthesize. SEM examination revealed a spherical shape of AgNPs with a size of 40-45 nm. The extract contained many functional groups as indicated by FT-IR. The extract alone inhibited the growth of normal rat splenic cells, while the extract containing AgNPs stimulated its growth. Extract alone stimulated HeLa cell proliferation and inhibited HepG2 growth, while both cell line growth was inhibited by the extract containing AgNPs. Both the extract and extract with AgNPs were safe on RBCs and did not cause any severe elevation in liver enzymes. The extract alone and with AgNPs showed insecticidal activity against Culex pipiens. Our findings suggest that the R. graveolens leaf extract, alone or with AgNPs, is biologically safe on animal cells and has antibacterial, insecticidal, and immunomodulation potentials.

Zinc oxide nanoparticles decorated fluorescent and antibacterial glass fiber pre-filter paper

Zinc oxide nanoparticles (ZnO–NPs) were synthesized and decorated simultaneously onto the glass fiber pre-filter paper (GF paper) by the sonochemical method without using any additional reagents (a ‘Green’ synthesis approach). ZnO–NPs decorated GF paper was characterized by electron, confocal laser scanning and atomic force microscopy, fourier transform infrared and atomic emission spectroscopy, X-ray diffraction, and thermogravimetric analysis etc. Due to the massive void volume space, exceptional dimensional stability, large thickness (790 μm) of the GF paper (unlike other paper materials) and ultrasonic irradiation effects, ZnO–NPs were decorated in the enormous amount (96 mg per paper) without causing any adverse effects on the GF paper. Such a huge amount decoration onto GF paper makes it multifunctional, fluorescencet (orange-pink color, 535–624 nm) under ultra-violet light (360 nm) and antibacterial. The antibacterial activity of the ZnO–NPs decorated GF paper was examined against Gram-positive bacteria Bacillus subtilis 168 and Staphylococcus aureus (MCC 2043, pathogenic). The outcomes from the antibacterial experiments revealed ∼99% (2 log) reduction in the survival of the filtered bacteria (B. subtilis) on the ZnO–NPs decorated GF paper due to the toxicity of ZnO–NPs on bacterial cells like cell shrinkage, cytoplasmic leakage, cell burst, etc. Multifunctional, ZnO–NPs decorated GF paper could be used for fluorescencet and antibacterial paper-based applications.

Study of anticancer, antimicrobial, immunomodulatory, and silver nanoparticles production by Sidr honey from three different sources

Sidr honey is used as food and medicine in many countries. Study of immunomodulatory and anticancer activity of Sidr honey did not tested before. The aim of this work was to study the anticancer activity and immunomodulatory as well as antimicrobial potential of Sidr honey and its synthesized silver nanoparticles (AgNPs). Sidr honey from three sources (two from Kingdom of Saudi Arabia (KSA) and one from Pakistan) was diluted to 20% and tested for its biological activities and to synthesize AgNPs. The results demonstrated that honeys could produce AgNPs (spherical shape), modulated the growth of normal splenic cells, and have antimicrobial activities. Sidr honey has anticancer activity against HepG2 but not Hela cells. Sidr honey can be used as antimicrobial agent, but can be used as anticancer agent with care as it stimulated cell growth of some lines (e.g., Hala) and inhibited another (e.g., HepG2).

The nanotech potential of turmeric (Curcuma longa L.) in food technology: A review

New trends in food are emerging in response to consumer awareness of the relationship between food and health, which has triggered the need to generate new alternatives that meet the expectations of the market. Revolutionary fields such as nanotechnology have been used for the encapsulation of nutritional ingredients and have great potential for the management of food additives derived from fruits and plant species. Turmeric, a spice that has been used as a dyeing agent, is recognized for its properties in Ayurveda medicine. This article aims to provide an overview of the characteristics of turmeric as an ingredient for the food industry, including its properties as a coloring agent, antioxidant, and functional ingredient. This article also highlights the potential of nanotechnology to enhance these properties of turmeric and increase the possibilities for the application of its components, such as cellulose and starch, in the development of nanostructures for food development.

Environment-friendly green composites based on soluble soybean polysaccharide: A review

The objective of the present review was to acquaint the readers with recent advances in soluble soy bean polysaccharide (SSPS)-based films. An efficient extraction method containing refining, pasteurizing and spray-drying is commonly used to extract SSPS. SSPS is a high molecular weight polysaccharide with a pectin-like structure. The predominant monosaccharide components are arabinose, galactose and galacturonic acid. Additionally, a trace amount of other monosaccharides such as glucose, fucose, rhamnose, and xylose are also present. SSPS allows us to make water-soluble, colorless, transparent, and edible films due to its high adhesive strength. The evaluation of recently published data on the development of SSPS films has demonstrated that nanoparticles can be used to improve the physicochemical characteristics of SSPS films. These nanoparticles not only reinforce the mechanical, thermal and physical properties of SSPS films, but also improve their antibacterial, anti-mold and anti-yeast activities. Hence, reinforcement of SSPS with nanoparticles is expected to open new approaches for revealing their applications in food packaging.

Anticancer Potential of Green Synthesized Silver Nanoparticles Using Extract of Nepeta deflersiana against Human Cervical Cancer Cells (HeLA)

In this study, silver nanoparticles (AgNPs) were synthesized using aqueous extract of Nepeta deflersiana plant. The prepared AgNPs (ND-AgNPs) were examined by ultraviolet-visible spectroscopy, Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscope (SEM), and energy dispersive spectroscopy (EDX). The results obtained from various characterizations revealed that average size of synthesized AgNPs was 33 nm and in face-centered-cubic structure. The anticancer potential of ND-AgNPs was investigated against human cervical cancer cells (HeLa). The cytotoxic response was assessed by 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide (MTT), neutral red uptake (NRU) assays, and morphological changes. Further, the influence of cytotoxic concentrations of ND-AgNPs on oxidative stress markers, reactive oxygen species (ROS) generation, mitochondrial membrane potential (MMP), cell cycle arrest and apoptosis/necrosis was studied. The cytotoxic response observed was in a concentration-dependent manner. Furthermore, the results also showed a significant increase in ROS and lipid peroxidation (LPO), along with a decrease in MMP and glutathione (GSH) levels. The cell cycle analysis and apoptosis/necrosis assay data exhibited ND-AgNPs-induced SubG1 arrest and apoptotic/necrotic cell death. The biosynthesized AgNPs-induced cell death in HeLA cells suggested the anticancer potential of ND-AgNPs. Therefore, they may be used to treat the cervical cancer cells.

Production and Characterization of Superhydrophobic and Antibacterial Coated Fabrics Utilizing ZnO Nanocatalyst

Dirt and microorganisms are the major problems in textiles which can generate unpleasant odor during their growth. Here, zinc oxide (ZnO) nanoparticles prepared by sol-gel method were loaded on the cotton fabrics using spin coating technique to enhance their antimicrobial properties and water repellency. The effects of ZnO precursor concentration, precursor solution pH, number of coating runs, and Mg doping percent on the structures, morphologies, and water contact angles (WCA) of the ZnO-coated fabrics were addressed. At 0.5 M concentration and pH7, more homogeneous and smaller ZnO nanoparticles were grown along the preferred (0 0 2) direction and uniformly distributed on the fabric with a crystallite size 17.98 nm and dislocation density 3.09 × 10-3 dislocation/nm2. The substitution of Zn 2+ with Mg 2+ ions slightly shifted the (002) peak position to a higher angle. Also, the zeta potential and particle size distribution were measured for ZnO nanoparticle suspension. A superhydrophobic WCA = 154° was measured for the fabric that coated at 0.5 M precursor solution, pH 7, 20 runs and 0% Mg doping. Moreover, the antibacterial activities of the ZnO-coated fabric were investigated against some gram-positive and gram-negative bacteria such as Salmonella typhimurium, Klebsiella pneumonia, Escherichia coli, and Bacillus subtilis.

Heterostructured ferromagnet-topological insulator with dual-phase magnetic properties

The introduction of ferromagnetism at the surface of a topological insulator (TI) produces fascinating spin-charge phenomena. It has been assumed that these fascinating effects are associated with a homogeneous ferromagnetic (FM) layer possessing a single type of magnetic phase. However, we obtained phase separation within the FM layer of a Ni80Fe20/Bi2Se3 heterostructure. This phase separation was caused by the diffusion of Ni into Bi2Se3, forming a ternary magnetic phase of Ni:Bi2Se3. The inward diffusion of Ni led to the formation of an FeSe phase outward, transforming the original Ni80Fe20/Bi2Se3 into a sandwich structure comprising FeSe/Ni:Bi2Se3/Bi2Se3 with dual-phase magnetic characteristics similar to that driven by the proximity effect. Such a phenomenon might have been overlooked in previous studies with a strong focus on the proximity effect. X-ray magnetic spectroscopy revealed that FeSe and Ni:Bi2Se3 possess horizontal and perpendicular magnetic anisotropy, respectively. The overall magnetic order of the heterostructure can be easily tuned by adjusting the thickness of the Bi2Se3 as it compromises the magnetic orders of the two magnetic phases. This discovery is essential to the quantification of spin-charge phenomena in similar material combinations where the FM layer is composed of multiple elements.

Food Quality Monitor: Paper-Based Plasmonic Sensors Prepared Through Reversal Nanoimprinting for Rapid Detection of Biogenic Amine Odorants

This paper describes the fabrication of paper-based plasmonic refractometric sensors through the embedding of metal nanoparticles (NPs) onto flexible papers using reversal nanoimprint lithography. The NP-embedded papers can serve as gas sensors for the detection of volatile biogenic amines (BAs) released from spoiled food. Commercial inkjet papers were employed as sensor substrates-their high reflectance (>80%) and smooth surfaces (roughness: ca. 4.9 nm) providing significant optical signals for reflection-mode plasmonic refractometric sensing and high particle transfer efficiency, respectively; in addition, because inkjet papers have lightweight and are burnable and flexible, they are especially suitable for developing portable, disposable, cost-effective, eco-friendly sensing platforms. Solid silver NPs (SNPs), solid gold NPs (GNPs), and hollow Au-Ag alloyed NPs (HGNs) were immobilized on a solid mold and then transferred directly onto the softened paper surfaces. The particle number density and exposure height of the embedded NPs were dependent on two imprinting parameters: applied pressure and temperature. The optimal samples exhibited high particle transfer efficiency (ca. 85%), a sufficient exposure surface area (ca. 50% of particle surface area) presented to the target molecules, and a strong resonance reflectance dip for detection. Moreover, the HGN-embedded paper displayed a significant wavelength dip shift upon the spontaneous adsorption of BA vapors (e.g., Δλ = 33 nm for putrescine; Δλ = 24 nm for spermidine), indicating high refractometric sensitivity; in contrast, no visible spectroscopic responses were observed with respect to other possibly coexisting gases (e.g., air, N₂, CO₂, water vapor) during the food storage process, indicating high selectivity. Finally, the plasmonic sensing papers were used to monitor the freshness of a food product (salmon).

Nanotechnology in Food Packaging

Food packaging is an integral component of the global food supply chain, protecting food from dirt, chemical contaminants and microorganisms, and helping to maintain food quality during transport and storage. Much of this packaging relies on modern polymeric materials, which have been developed to help control the exposure of products to light, oxygen and moisture. These have the benefits of being lightweight, cost-effective, reusable, recyclable and resistant to chemical and physical damage. Although traditional polymeric materials can fulfill many of these requirements, efforts continue to maintain or improve packaging performance while reducing the use of raw materials, waste and costs. The use of nanotechnology to produce nanocomposite materials has great promise to improve the characteristics of food packaging, but many of the products are still in their infancy. Only a relatively small number of nanoenabled products have entered the market and many, but not all, occupy niche markets. This chapter briefly describes the areas where nanomaterials have been used in research and commercial products to improve mechanical and barrier properties and to create active and intelligent packaging materials. It also addresses the regulation of nanomaterials in food contact applications and migration when evaluating the safety of these materials.

An overview application of silver nanoparticles in inhibition of herpes simplex virus

Nanoscale particles and molecules are a potential different for the treatment of disease because they have distinctive biologic property based on their structure and size, which is different from traditional small-molecule drugs. The antimicrobial mechanisms of silver nanoparticles include the formation of free radicals damaging the bacterial membranes, interactions with DNA, adhesion to cell surface altering the membrane properties, and enzyme damage. In this review, we focus on applications of silver nanoparticles in inhibition of herpes simplex virus.

Sonochemical production of nanoparticle metal oxides for potential use in dentistry

Two types of ultrasonic instruments used in dentistry have been compared with a sonochemical horn for the production of copper oxide and zinc oxide nanoparticles. The nanoparticles can be produced from benign reagents using dental instruments as the source of sonochemical enhancement. The process has been operated in resin models of teeth in a preliminary exploration of the potential of the method for enhancing procedures such as root canal surgery. The technique is potentially useful but further work is needed for a full assessment of using in-situ generated nanoparticles as an aid to disinfection during some types of dental surgery.

Nanostructured Materials Synthesis Using Ultrasound

Recent applications of ultrasound to the production of nanostructured materials are reviewed. Sonochemistry permits the production of novel materials or provides a route to known materials without the need for high bulk temperatures, pressures, or long reaction times. Both chemical and physical phenomena associated with high-intensity ultrasound are responsible for the production or modification of nanomaterials. Most notable are the consequences of acoustic cavitation: the formation, growth, and implosive collapse of bubbles, and can be categorized as primary sonochemistry (gas-phase chemistry occurring inside collapsing bubbles), secondary sonochemistry (solution-phase chemistry occurring outside the bubbles), and physical modifications (caused by high-speed jets, shockwaves, or inter-particle collisions in slurries).

Hybrid Plasmonic Nanostructures

Plasmonic hybrid nanostructure including Semiconductor-metallic nanoparticles, and graphene-plasmonic nanocomposites have great potential to be used as photocatalyst for hydrogen production and for photodegradation of organic waste. Also, they are potential candidate as active materials in photovoltaic devices. Plasmonic-magnetic nanocomposites could be used in photothermal therapy and biomedical imaging. This chapter will focus on the environmental impact of these materials and their in-vitro and in-vivo toxicity. In addition, the applications of these hybrid nanostructures in energy and environment will be discussed in details.

Biocompatible silver nanoparticles prepared with amino acids and a green method

The synthesis of nanoparticles is usually carried out by chemical reduction, which is effective but uses many toxic substances, making the process potentially harmful to the environment. Hence, as part of the search for environmentally friendly or green synthetic methods, this study aimed to produce silver nanoparticles (AgNPs) using only AgNO₃, Milli-Q water, white light from a xenon lamp (Xe) and amino acids. Nanoparticles were synthetized using 21 amino acids, and the shapes and sizes of the resultant nanoparticles were evaluated. The products were characterized by UV-Vis, zeta potential measurements and transmission electron microscopy. The synthesis of silver nanoparticles with tryptophan and tyrosine, methionine, cystine and histidine was possible through photoreduction method. Spherical nanoparticles were produced, with sizes ranging from 15 to 30 nm. Tryptophan does not require illumination nor heating, and the solution color changes immediately after the mixing of reagents if sodium hydroxide is added to the solution (pH = 10). The Xe illumination acts as sodium hydroxide in the nanoparticles synthesis, releases H⁺ and allows the reduction of silver ions (Ag⁺) in metallic silver (Ag⁰).

Shadow-casted ultrathin surface coatings of titanium and titanium/silicon oxide sol particles via ultrasound-assisted deposition

Ultrasound-assisted deposition (USAD) of sol nanoparticles enables the formation of uniform and inherently stable thin films. However, the technique still suffers in coating hard substrates and the use of fast-reacting sol-gel precursors still remains challenging. Here, we report on the deposition of ultrathin titanium and titanium/silicon hybrid oxide coatings using hydroxylated silicon wafers as a model hard substrate. We use acetic acid as the catalyst which also suppresses the reactivity of titanium tetraisopropoxide while increasing the reactivity of tetraethyl orthosilicate through chemical modifications. Taking the advantage of this peculiar behavior, we successfully prepared titanium and titanium/silicon hybrid oxide coatings by USAD. Varying the amount of acetic acid in the reaction media, we managed to modulate thickness and surface roughness of the coatings in nanoscale. Field-emission scanning electron microscopy and atomic force microscopy studies showed the formation of conformal coatings having nanoroughness. Quantitative chemical state maps obtained by x-ray photoelectron spectroscopy (XPS) suggested the formation of ultrathin (<10nm) coatings and thickness measurements by rotating analyzer ellipsometry supported this observation. For the first time, XPS chemical maps revealed the transport effect of ultrasonic waves since coatings were directly cast on rectangular substrates as circular shadows of the horn with clear thickness gradient from the center to the edges. In addition to the progress made in coating hard substrates, employing fast-reacting precursors and achieving hybrid coatings; this report provides the first visual evidence on previously suggested "acceleration and smashing" mechanism as the main driving force of USAD.

Flexible Plasmonic Sensors

Mechanical flexibility and the advent of scalable, low-cost, and high-throughput fabrication techniques have enabled numerous potential applications for plasmonic sensors. Sensitive and sophisticated biochemical measurements can now be performed through the use of flexible plasmonic sensors integrated into existing medical and industrial devices or sample collection units. More robust sensing schemes and practical techniques must be further investigated to fully realize the potentials of flexible plasmonics as a framework for designing low-cost, embedded and integrated sensors for medical, environmental, and industrial applications.

Sonochemistry: Science and Engineering

Sonochemistry offers a simple route to nanomaterial synthesis with the application of ultrasound. The tiny acoustic bubbles, produced by the propagating sound wave, enclose an incredible facility where matter interact among at energy as high as 13 eV to spark extraordinary chemical reactions. Within each period - formation, growth and collapse of bubbles, lies a coherent phase of material formation. This effective yet highly localized method has facilitated synthesis of various chemical and biological compounds featuring unique morphology and intrinsic property. The benign processing lends to synthesis without any discrimination towards a certain group of material, or the substrates where they are grown. As a result, new and improved applications have evolved to reach out various field of science and technology and helped engineer new and better devices. Along with the facile processing and notes on the essence of sonochemistry, in this comprehensive review, we discuss the individual and mutual effect of important input parameters on the nanomaterial synthesis process as a start to help understand the underlying mechanism. Secondly, an objective discussion of the diversely synthesized nanomaterial follows to divulge the easiness imparted by sonochemistry, which finally blends into the discussion of their applications and outreach.

Imparting commercial antimicrobial dressings with low-adherence to burn wounds

The objective of our study was to decrease the wound adherence of commercial silver based wound dressings by depositing a non-adherent layer. Our hypothesis was that this non-adherent layer will lower the dressing's adherence to burn wounds without compromising the antimicrobial activity or increasing the cytotoxicity. A polyacrylamide (PAM) hydrogel layer was grafted on two commercial silver antimicrobial dressings (silver nanocrystal dressing (NC) and silver plated dressing (SP)) using a proprietary technique. The grafted PAM served as the non-adherent layer. Dressing adherence was measured with a previously published in vitro gelatin model using an Instron mechanical force testing instrument. The dressings were challenged with two clinically retrieved bacterial strains (Methicillin-resistant Staphylococcus aureus (MRSA) and multidrug resistant (MDR) Pseudomonas aeruginosa) with both a disk diffusion test, and a suspension antibacterial test. The cytotoxicity of samples to human neonatal fibroblast cells was evaluated with 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyltetrazolium bromide (MTT) assay. Both untreated dressings showed high peeling energy: 2070±453J/m(2) (NC) and 669±68J/m(2) (SP), that decreased to 158±119J/m(2) (NC) and 155±138J/m(2) (SP) with the PAM deposition. Addition of the PAM caused no significant difference in zone of inhibition (ZOI) (disk diffusion test) or antibacterial kinetics (suspension test) against both bacteria (p>0.05, n=6) in either dressing. Survival of fibroblasts was improved by the PAM grafting from 48±5% to 60±3% viable cells in the case of NC and from 55±8% to 61±4% viable cells in SP (p<0.05, n=12). It was concluded that PAM as a non-adherent layer significantly decreases the adherence of these two commercial antimicrobial dressings in an in vitro gelatin model while preserving their antimicrobial efficacy, and reducing their cytotoxicity.

Sonochemical co-deposition of antibacterial nanoparticles and dyes on textiles

The sonochemical technique has already been proven as one of the best coating methods for stable functionalization of substrates over a wide range of applications. Here, we report for the first time on the simultaneous sonochemical dyeing and coating of textiles with antibacterial metal oxide (MO) nanoparticles. In this one-step process the antibacterial nanoparticles are synthesized in situ and deposited together with dye nanoparticles on the fabric surface. It was shown that the antibacterial behavior of the metal oxides was not influenced by the presence of the dyes. Higher K/S values were achieved by sonochemical deposition of the dyes in comparison to a dip-coating (exhaustion) process. The stability of the antibacterial properties and the dye fastness was studied for 72 h in saline solution aiming at medical applications.

Effect of polyethylene glycol on the antibacterial properties of polyurethane/carbon nanotube electrospun nanofibers

The as-prepared nanofibers have better antibacterial properties. Incorporating PEG effectively reduced the CNT toxicity to human cells and also decreased the attachment of bacteria.