Development of super nanoantimicrobials combining AgCl, tetracycline and benzalkonium chloride

In this work, we demonstrate that a simple argentometric titration is a scalable, fast, green and robust approach for producing AgCl/antibiotic hybrid antimicrobial materials. We titrated AgNO3 into tetracycline hydrochloride (TCH) aqueous solution, thus forming AgCl/TCH in a one-step procedure. Furthermore, we investigated the one-pot synthesis of triply synergistic super-nanoantimicrobials, combining an inorganic source of Ag+ ions (AgCl), a disinfecting agent (benzyl-dimethyl-hexadecyl-ammonium chloride, BAC) and a molecular antibiotic (tetracycline hydrochloride, TCH). Conventional antimicrobial tests, industrial biofilm detection protocols, and in situ IR-ATR microbial biofilm monitoring, have been adapted to understand the performance of the synthesized super-nanoantimicrobial. The resulting hybrid AgCl/BAC/TCH nanoantimicrobials are found to be synergistically active in eradicating Salmonella enterica and Lentilactobacillus parabuchneri bacteria and biofilms. This study paves the way for the development of a new class of super-efficient nanoantimicrobials that combine relatively low amounts of multiple active species into a single (nano)formulation, thus preventing the development of antimicrobial resistance towards a single active principle.

Synthesis and Antimicrobial Activity of 3D Micro-Nanostructured Diatom Biosilica Coated by Epitaxially Growing Ag-AgCl Hybrid Nanoparticles

The 3D (three-dimensional) micro-nanostructured diatom biosilica obtained from cultivated diatoms was used as a support to immobilize epitaxially growing AgCl-Ag hybrid nanoparticles ((Ag-AgCl)NPs) for the synthesis of nanocomposites with antimicrobial properties. The prepared composites that contained epitaxially grown (Ag-AgCl)NPs were investigated in terms of their morphological and structural characteristics, elemental and mineral composition, crystalline forms, zeta potential, and photoluminescence properties using a variety of instrumental methods including SEM (scanning electron microscopy), TEM (transmission electron microscopy), EDX (energy-dispersive X-ray spectroscopy), XRD (X-ray powder diffraction), zeta-potential measurement, and photoluminescence spectroscopy. The content of (AgCl-Ag)NPs in the hybrid composites amounted to 4.6 mg/g and 8.4 mg/g with AgClNPs/AgNPs ratios as a percentage of 86/14 and 51/49, respectively. Hybrid nanoparticles were evenly dispersed with a dominant size of 5 to 25 nm in composite with an amount of 8.4 mg/g of silver. The average size of the nanoparticles was 7.5 nm; also, there were nanoparticles with a size of 1-2 nm and particles that were 20-40 nm. The synthesis of (Ag-AgCl)NPs and their potential mechanism were studied. The MIC (the minimum inhibitory concentration method) approach was used to investigate the antimicrobial activity against microorganisms Klebsiella pneumoniae, Escherichia coli, and Staphylococcus aureus. The nanocomposites containing (Ag-AgCl)NPs and natural diatom biosilica showed resistance to bacterial strains from the American Type Cultures Collection and clinical isolates (diabetic foot infection and wound isolates).

Ag Nanoparticles and Rod-Shaped AgCl Decorated Porous PEDOT as a Bifunctional Material for Hydrogen Evolution Catalyst and Supercapacitor Electrode

PEDOT-Ag/AgCl is a highly promising material with dual functions of hydrogen evolution reaction (HER) and supercapacitors. In this study, a simple low-temperature stirring and light irradiation method was used to synthesize PEDOT-Ag/AgCl on the surface. Then, PEDOT-Ag/AgCl was analyzed using X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy, and transmission electron microscopy. PEDOT-Ag/AgCl reacted in 1 M KOH alkaline electrolyte with an overpotential of 157 mV at 20 mA·cm-2 and a Tafel slope of 66.95 mv·dec-1. Owing to the synergistic effect of PEDOT and Ag/AgCl, this material had a small resistance (1.7 Ω) and a large specific capacitance (978 F·g-1 at current density of 0.5 A·g-1). The synthesis method can prepare nanostructured PEDOT with uniformly-distributed Ag nanoparticles and rod-shaped AgCl on the surface, which can be used as both HER electrocatalysts and supercapacitor electrodes.

Modification of poly(L-lactic acid)-based films and evaluation of physical and antibacterial properties by using multivariate data analysis

The aim of this study is to prepare new packaging materials with improved physical and antimicrobial properties that prevent the growth of microorganisms. Poly(L-lactic acid) (PLA) based packaging films were prepared by the solvent-casting method using spruce resin (SR), epoxidized soybean oil, an essential oil mixture (calendula and clove oil), and silver nanoparticles (AgNPs). The AgNPs were synthesized by the polyphenol reduction method, using spruce resin dissolved in methylene chloride. The prepared films were tested for antibacterial activity and physical properties, such as tensile strength (TS), elongation at break (EB), elastic modulus (EM), water vapor permeability (WVP), and UV-C blocking effect. The addition of SR decreased the water vapor permeation (WVP) of the films, whereas the addition of essential oils (EOs) increased this property due to their higher polarity. The morphological, thermal, and structural properties were characterized using SEM, UV-Visible spectroscopy, FTIR, and DSC. The agar disc well method showed that SR, AgNPs, and EOs imparted antibacterial activity to the PLA-based films against Staphylococcus aureus and Escherichia coli. Multivariate data analysis tools, such as principal component and hierarchical cluster analysis, were used to discriminate PLA-based films by simultaneously evaluating their physical and antibacterial properties.

Ag/Ag3PO4 Nanoparticle-Decorated Hydroxyapatite Functionalized Calcium Carbonate: Ultrasound-Assisted Sustainable Synthesis, Characterization, and Antimicrobial Activity

Silver nanoparticles are usually prepared by the reduction of silver cations through chemical and non-sustainable procedures that involve the use of reducing chemical agents. Therefore, many efforts have been made in the search for sustainable alternative methods. Among them, an ultrasound-assisted procedure could be a suitable and sustainable method to afford well-dispersed and nanometric silver particles. This paper describes a sustainable, ultrasound-assisted method using citrate as a reducing agent to prepare silver@hydroxyapatite functionalized calcium carbonate composites. For comparison, an ultrasound-assisted reduction was performed in the presence of NaBH₄. The composites obtained in the presence of these two different reducing agents were compared in terms of nanoparticle nature, antimicrobial activity, and cytotoxic activity. The nanoparticle nature was investigated by several techniques, including X-ray powder diffraction, field-emission scanning electron microscopy, transmission electron microscopy, UV-Vis spectroscopic measurements, and X-ray photoemission spectroscopy. Nanoparticles with a predominance of Ag or Ag₃PO₄ were obtained according to the type of reducing agent used. All composites were tested for antimicrobial and antibiofilm activities against Gram-positive and Gram-negative (Staphylococcus aureus and Pseudomonas aeruginosa, respectively) bacteria and for cytotoxicity towards human skin keratinocytes and human fibroblasts. The nature of the nanoparticles, Ag or Ag₃PO₄, and their predominance seemed to affect the in vitro silver release and the antimicrobial and antibiofilm activities. The composites obtained by the citrate-assisted reduction gave rise to the best results.

Alginate Ag/AgCl Nanoparticles Composite Films for Wound Dressings with Antibiofilm and Antimicrobial Activities

Recently, silver-based nanoparticles have been proposed as components of wound dressings due to their antimicrobial activity. Unfortunately, they are cytotoxic for keratinocytes and fibroblasts, and this limits their use. Less consideration has been given to the use of AgCl nanoparticles in wound dressings. In this paper, a sustainable preparation of alginate AgCl nanoparticles composite films by simultaneous alginate gelation and AgCl nanoparticle formation in the presence of CaCl₂ solution is proposed with the aim of obtaining films with antimicrobial and antibiofilm activities and low cytotoxicity. First, AgNO₃ alginate films were prepared, and then, gelation and nanoparticle formation were induced by film immersion in CaCl₂ solution. Films characterization revealed the presence of both AgCl and metallic silver nanoparticles, which resulted as quite homogeneously distributed, and good hydration properties. Finally, films were tested for their antimicrobial and antibiofilm activities against Staphylococcus epidermidis (ATCC 12228), Staphylococcus aureus (ATCC 29213), Pseudomonas aeruginosa (ATCC 15692), and the yeast Candida albicans. Composite films showed antibacterial and antibiofilm activities against the tested bacteria and resulted as less active towards Candida albicans. Film cytotoxicity was investigated towards human dermis fibroblasts (HuDe) and human skin keratinocytes (NCTC2544). Composite films showed low cytotoxicity, especially towards fibroblasts. Thus, the proposed sustainable approach allows to obtain composite films of Ag/AgCl alginate nanoparticles capable of preventing the onset of infections without showing high cytotoxicity for tissue cells.

Green Synthesis and Characterization of Antimicrobial Synergistic AgCl/BAC Nanocolloids

All over the world, one of the major challenges is the green synthesis of potential materials against antimicrobial resistance and viruses. This study demonstrates a simple method like chemistry lab titration to synthesize green, facile, scalable, reproducible, and stable synergistic silver chloride/benzyldimethylhexadecyl-ammonium chloride (AgCl/BAC) colloidal Nanoantimicrobials (NAMs). Nanocolloidal dispersions of AgCl in an aqueous medium are prepared by using silver nitrate (AgNO₃) as precursor and BAC as both sources of chloride and stabilizer, holding an asymmetric molecular structure. The synthetic approach is scalable and green. Both the morphology and stability of AgCl/BAC nanocolloids (NCs) were investigated as a function of different molar fractions of the reagents. AgCl/BAC NCs were characterized by transmission electron microscopy (TEM) and X-ray photoelectron and UV–vis spectroscopies. Zeta potential measurements revealed increasing positive potential values at every stage of the synthesis. Size distribution and hydrodynamic diameter of the particles were measured by dynamic light scattering (DLS), which predicted the formation of BAC layered structures associated with the AgCl nanoparticles (NPs). Small-angle X-ray scattering (SAXS) experiments verify the thickness of the BAC bilayer around AgCl. The produced AgCl/BAC NCs probably have synergistic antimicrobial properties from the AgCl core and the biocide BAC shell. AgCl/BAC NCs stability over months was investigated. The experimental evidence supports the morphological stability of the AgCl/BAC NCs, while higher positive zeta potential values anticipate a long-term antimicrobial effect: a higher surface charge causes NPs to be potentially more lethal to bacteria. AgCl/BAC antimicrobial aqueous colloidal suspensions will be used as additives for the industrial production of antimicrobial coatings.

Direct contact, dissolution and generation of reactive oxygen species: How to optimize the antibacterial effects of layered double hydroxides

Infections by pathogenic bacteria have been threatening several fields as food industries, agriculture, textile industries and healthcare products. Layered double hydroxides materials (LDHs), also called anionic clays, could be utilized as efficient antibacterial materials due to their several interesting properties such as ease of synthesis, tunable chemical composition, biocompatibility and anion exchange capacity. Pristine LDHs as well as LDH-composites including antibacterial molecules and nanoparticles loaded-LDHs were proven to serve as efficient antibacterial agents against various Gram-positive and Gram-negative bacterial strains. The achieved antibacterial effect was explained by the following mechanisms: (1) Direct contact between the materials and bacterial cells driven by electrostatic interactions between positively charged layers and negatively charged cell membranes, (2) Dissolution and gradual release over time of metallic ions or antibacterial molecules, (3) Generation of reactive oxygen species.

Overcoming Antibiotic Resistance: Playing the 'Silver Nanobullet' Card

Enhancing the antibacterial activity of old antibiotics by a multitarget approach, such as combining antibiotics with metal nanoparticles, is a valuable strategy to overcome antibacterial resistance. In this work, the synergistic antimicrobial effect of silver nanoparticles and antibiotics, immobilized on a solid support, was investigated. Nanometric layered double hydroxides (LDH) based on Zn(II) and Al(III) were prepared by the double microemulsion technique. The dual function of LDH as an anionic exchanger and support for metal nanoparticles was exploited to immobilize both silver and antibiotics. Cefazolin (CFZ), a β-lactam, and nalidixic acid (NAL), a quinolone, were selected and intercalated into LDH obtaining ZnAl-CFZ and ZnAl-NAL samples. These samples were used for the growth of silver nanoparticles with dimension ranging from 2.5 to 8 nm. Silver and antibiotics release profiles, from LDH loaded with antibiotics and Ag/antibiotics, were evaluated in two different media: water and phosphate buffer. Interestingly, the release profiles are affected by both the acceptor media and the presence of silver. The synergistic antibacterial activity of LDH containing both silver and antibiotics were investigated on gram-positives (Staphylococcus aureus and Streptococcus pneumoniae) and gram-negatives (Pseudomonas aeruginosa) and compared with the plain antimicrobials and LDH containing only antibiotics or silver.

Hybrid Polydopamine/Ag Shell-Encapsulated Magnetic Fe3O4 Nanosphere with High Antibacterial Activity

The bacteria, which usually contaminate water environment, often cause terrible infectious diseases thus seriously threaten people's health. To meet the increasing requirement of the public health care, an easily separable nanomaterial with sustainable anti-bacteria performance is required. This work reports a Fe₃O₄@PDA/Ag/PDA core-shell nanosphere in which the Ag nanocrystals immobilized on the magnetic carrier are protected by an external polydopamine (PDA) layer. The magnetic hybrid nanospheres are constructed by a tunable coating method and the particle parameters can be effectively controlled by the experimental condition. The antibacterial potential of the nanospheres is evaluable by using the Staphylococcus aureus and Escherichia coli as the models. The results indicate the Fe₃O₄@PDA/Ag/PDA core-shell nanospheres have a high antibacterial performance by measuring the minimum inhibitory concentration and the minimum bactericidal concentration. Finally, the product is expected to have a sustainable activity because the protecting PDA layer reduce the releasing rate of the Ag⁺ ions and the materials can be magnetically recovered from the media after the disinfection procedure.

Recent innovations in functionalized layered double hydroxides: Fabrication, characterization, and industrial applications

Layered Double Hydroxides (LDHs) are a group of hydrotalcite-like nano-sized materials with cationic layers and exchangeable interlayer anions. The wide range of divalent and trivalent cationic metals and anionic compounds are employed in the synthesis of LDH materials, which have improved their importance among the researchers. Because of their high anion exchange property, memory effect, tunable behavior, bio-friendly, simple preparation, and their affordability, these nano-materials are essentially interested today. Modification of LDHs improves their behaviours to make them appropriate in industrial fields, including biological, adsorbent, mechanical, optical, thermal, electrical fields, etc. This review has critically discussed the structural features, main properties, and also clarified the most important methods of modification and intercalation of LDH nano-materials. Moreover, some novel reported researches related to the successful modification of LDH materials have been characterized and briefly the advantages, disadvantages, and applications are presented in the industrial fields.

Application of Protein-Based Films and Coatings for Food Packaging: A Review

As the IV generation of packaging, biopolymers, with the advantages of biodegradability, process ability, combination possibilities and no pollution to food, have become the leading food packaging materials. Biopolymers can be directly extracted from biomass, synthesized from bioderived monomers and produced directly by microorganisms which are all abundant and renewable. The raw materials used to produce biopolymers are low-cost, some even coming from agrion dustrial waste. This review summarized the advances in protein-based films and coatings for food packaging. The materials studied to develop protein-based packaging films and coatings can be divided into two classes: plant proteins and animal proteins. Parts of proteins are referred in this review, including plant proteins i.e., gluten, soy proteins and zein, and animal proteins i.e., casein, whey and gelatin. Films and coatings based on these proteins have excellent gas barrier properties and satisfactory mechanical properties. However, the hydrophilicity of proteins makes the protein-based films present poor water barrier characteristics. The application of plasticizers and the corresponding post-treatments can make the properties of the protein-based films and coatings improved. The addition of active compounds into protein-based films can effectively inhibit or delay the growth of microorganisms and the oxidation of lipids. The review also summarized the research about the storage requirements of various foods that can provide corresponding guidance for the preparation of food packaging materials. Numerous application examples of protein-based films and coatings in food packaging also confirm their important role in food packaging materials.

AgCl-ZnAl Layered Double Hydroxides as Catalysts with Enhanced Photodegradation and Antibacterial Activities

Surface-modified ZnAl layered double hydroxides (LDHs) were prepared by reaction of AgNO3, with both ZnAlCl (LDH1) and ZnAlCO3 exchanged on the surface with chloride anions (LDH3). In this way, AgCl nanoparticles with crystalline domains ranging from 40 to 100 nm were grown on the LDH surface. An additional sample was prepared by partial reduction of silver to obtain Ag@AgCl-LDH (LDH2). The composites were tested as catalysts in Rhodamine B (RhB) degradation, wherein LDH2 showed complete cleavage of RhB after 45 min of irradiation versus 70 min needed in the presence of AgCl. This time decreased to 35 min for LDH1 and 15 min for LDH3, underlining the role of the AgCl dimensions and anion in the interlayer region. Studies on the reactive species involved in the degradation process revealed that, for all catalysts, O2·− was the main active species, while, to some extent, holes contribute to the activity of the LDH3. Finally, the composites showed high bactericidal activity, under irradiation, against Escherichia coli, comparable with that of Gentamicin, the positive control. A synergic effect of silver released from the composites and the production of reactive oxygen species was considered.

Nanostructuring Biopolymers for Improved Food Quality and Safety

Food-grade biopolymers, apart from their inherent nutritional properties, can be tailored designed for improving food quality and safety, either serving as delivery vehicles for bioactive molecules, or as novel packaging components, not only improving the transport properties of biobased packaging structures, but also imparting active antibacterial and antiviral properties. In this chapter, the potential of different food-grade biopolymers (mainly proteins and carbohydrates but also some biopolyesters) to serve as encapsulating matrices for the protection of sensitive bioactives or as nanostructured packaging layers to improve transport properties and control the growth of pathogenic bacteria and viruses are described based on some developments carried out by the authors, as well as the most prominent works found in literature in this area.

Natural extracted aerogels with inherent anisotropy and their 3D printing assisted biomedical applications

Exemplified with jackfruit and sugarcane, natural extracted aerogels with inherent structural anisotropy were investigated for the first time. With the help of nano-modification, the dual liquid/current directing capability of the Ag decorated jackfruit aerogel was discovered. This interesting material was then applied as the core component of a 3D printed wearable device for intelligent wound management. The as-prepared ultra-light (<10 g) wearable device could provide drainage diversion, wound warning and triple antibacterial treatment in a continuous and automatic manner.

Characterization of Antimicrobial Poly (Lactic Acid)/Nano-Composite Films with Silver and Zinc Oxide Nanoparticles

Antimicrobial active films based on poly (lactic acid) (PLA) were prepared with nano-silver (nano-Ag) and nano-zinc oxide (nano-ZnO) using a solvent volatilizing method. The films were characterized for mechanical, structural, thermal, physical and antimicrobial properties. Scanning electron microscopy (SEM) images characterized the fracture morphology of the films with different contents of nano-Ag and nano-ZnO. The addition of nanoparticles into the pure PLA film decreased the tensile strength and elasticity modulus and increased the elongation of breaks-in other words, the flexibility and extensibility of these composites improved. According to the results of differential scanning calorimetry (DSC), the glass transition temperature of the PLA nano-composite films decreased, and the crystallinity of these films increased; a similar result was apparent from X-ray diffraction (XRD) analysis. The water vapor permeability (WVP) and opacity of the PLA nano-composite films augmented compared with pure PLA film. Incorporation of nanoparticles to the PLA films significantly improved the antimicrobial activity to inhibit the growth of Escherichia coli. The results indicated that PLA films with nanoparticles could be considered a potential environmental-friendly packaging material.

A novel in situ silver/hyaluronan bio-nanocomposite fabrics for wound and chronic ulcer dressing: In vitro and in vivo evaluations

In-situ formed hyaluronan/silver (HA/Ag) nanoparticles (NPs) were used to prepare composite fibers/fabrics for the first time. Different concentrations of silver nitrate (1, 2mg/100ml) were added at ambient temperature to sodium hyaluronate solution (40mg/ml), then the pH was increased to 8 by adding sodium hydroxide. The in-situ formed HA/Ag-NPs were used to prepare fibers/nonwoven fabrics by wet-dry-spinning technique (WDST). UV/vis spectroscopy, SEM, TEM, DLS, XPS, XRD and TGA were employed to characterize the structure and composition of the nanocomposite, surface morphology of fiber/fabrics, particle size of Ag-NPs, chemical interactions of Ag⁰ and HA functional groups, crystallinity and thermal stability of the wound dressing, respectively. The resultant HA/Ag-NPs1 and HA/Ag-NPs2 composite showed uniformly dispersed throughout HA fiber/fabrics (SEM), an excellent distribution of Ag-NPs with 25±2, nm size (TEM, DLS) and acceptable mechanical properties. The XRD analysis showed that the in-situ preparation of Ag-NPs increased the crystallinity of the resultant fabrics as well as the thermal stability. The antibacterial performance of medical HA/Ag-NPs fabrics was evaluated against gram negative bacteria E. coli K12, exhibiting significant bactericidal activity. The fibers did not show any cytotoxicity against human keratinocyte cell line (HaCaT). In-vivo animal tests indicated that the prepared wound dressing has strong healing efficacy (non-diabetics/diabetics rat model) compared to the plain HA fabrics and greatly accelerated the healing process. Based on our results, the new HA/Ag-NPs-2mg nonwoven wound dressing fabrics can be used in treating wounds and chronic ulcers as well as cell carrier in different biological research and tissue engineering.

A Nanoscale Interface Promoting Molecular and Functional Differentiation of Neural Cells

Potassium channels and aquaporins expressed by astrocytes are key players in the maintenance of cerebral homeostasis and in brain pathophysiologies. One major challenge in the study of astrocyte membrane channels in vitro, is that their expression pattern does not resemble the one observed in vivo. Nanostructured interfaces represent a significant resource to control the cellular behaviour and functionalities at micro and nanoscale as well as to generate novel and more reliable models to study astrocytes in vitro. However, the potential of nanotechnologies in the manipulation of astrocytes ion channels and aquaporins has never been previously reported. Hydrotalcite-like compounds (HTlc) are layered materials with increasing potential as biocompatible nanoscale interface. Here, we evaluate the effect of the interaction of HTlc nanoparticles films with primary rat neocortical astrocytes. We show that HTlc films are biocompatible and do not promote gliotic reaction, while favouring astrocytes differentiation by induction of F-actin fibre alignment and vinculin polarization. Western Blot, Immunofluorescence and patch-clamp revealed that differentiation was accompanied by molecular and functional up-regulation of both inward rectifying potassium channel Kir 4.1 and aquaporin 4, AQP4. The reported results pave the way to engineering novel in vitro models to study astrocytes in a in vivo like condition.

Biomedical Potential of Ultrafine Ag/AgCl Nanoparticles Coated on Graphene with Special Reference to Antimicrobial Performances and Burn Wound Healing

In recent years, researchers have proven the release of silver ions (Ag(+)) from silver nanoparticles (Ag NPs) significantly affects their toxicity to bacteria and other organisms. Due to the difficulty in maintaining a steady flux of a high concentration of Ag(+), it is still challenging to develop a highly efficient, stable, and biocompatible Ag NP-based antimicrobial material. To circumvent this issue, we developed a new Ag-based bactericide through the fabrication of sunlight-driven and ultrafine silver/silver chloride anchored on reduced graphene oxide (Ag/AgCl/rGO). This stable Ag/AgCl nanophotocatalyst with negligible release of Ag(+) generated a high amount of oxidative radicals, killing the bacteria, thus achieving both high bactericidal efficiency and stability. Moreover, functionalization of the nanomaterial with poly(diallyldimethylammonium chloride) (PDDA) gives it a highly adsorptive capacity, which allows it to capture the bacteria and possibly enhances the bactericidal activity. In vivo histopathological studies showed that the Ag/AgCl/rGO nanomaterial could obviously promote the regeneration of the epidermis, which indicated the good biomedical potential of Ag/AgCl/rGO nanomaterial in burn wound healing.

One-step synthesis of silver metallosurfactant as an efficient antibacterial and anticancer material

A silver based double chained metallosurfactant was synthesized and characterized with various analytical methods. Along with the self aggregation behavior, DNA binding abilities of metallomicelles and antimicrobial and anticancer activities were evaluated.

Facile synthesis of silver nanoparticles deposited on a calcium silicate hydrate composite as an efficient bactericidal agent

Silver nanoparticles deposited calcium silicate hydrate composite was synthesized and demonstrated high antibacterial activities against Gram-negative and Gram-positive bacteria.

Carboxymethylcellulose films containing chlorhexidine–zirconium phosphate nanoparticles: antibiofilm activity and cytotoxicity

Hybrid composite films of carboxymethylcellulose and chlorhexidine intercalated nanosized zirconium phosphate result able to reduce the formation of biofilms on wound surface.

Evaluation of Novel Antibacterial N-Halamine Nanoparticles Prodrugs towards Susceptibility of Escherichia coli Induced by DksA Protein

Novel N-halamine nanoparticles potentially useful for killing pathogenic bacteria, i.e., SiO2@PS/N-halamine NPs, were successfully synthesized via the immobilization of N-halamines onto the polystyrene-coated silica nanoparticles (SiO2@PS NPs). The effect of reaction conditions, i.e., chlorination temperature, bleaching concentration, chlorination time, on the oxidative chlorine content in the products was systematically investigated. The antibacterial activity of the products was tested via the modified plate counting methd using Escherichia coli (E. coli) as a model bacterium. The possible mechanism of the antibacterial action of the products was also studied using scanning electron microscopy combined with a inhibition zone study. The antimicrobial capability of the products was well controlled by tuning the oxidative chlorine content in the products. More importantly, the role of DksA protein in the susceptibility of E. coli against the products was proven using a time-kill assay. This in-depth investigation of the sensitivity of E. coli towards N-halamine NPs provides a systematic understanding of the utility of N-halamines for deactivating bacteria or even disease control.

Influence of physicochemical properties of silver nanoparticles on mast cell activation and degranulation

Silver nanoparticles (AgNPs) are increasingly being incorporated into products for their antimicrobial properties. This has resulted in increased human exposures and the possibility of adverse health effects. Mast cells orchestrate allergic immune responses through degranulation and release of pre-formed mediators. Little data exists on understanding interactions of AgNPs with mast cells and the properties that influence activation and degranulation. Using bone marrow-derived mast cells and AgNPs of varying physicochemical properties we tested the hypothesis that AgNP physicochemical properties influence mast cell degranulation and osteopontin production. AgNPs evaluated included spherical 20 nm and 110 nm suspended in either polyvinylpyrrolidone (PVP) or citrate, Ag plates suspended in PVP of diameters between 40–60 nm or 100–130 nm, and Ag nanowires suspended in PVP with thicknesses <100 nm and length up to 2 μm. Mast cell responses were found to be dependent on the physicochemical properties of the AgNP. Further, we determined a role for scavenger receptor B1 in AgNP-induced mast cell responses. Mast cell degranulation was not dependent on AgNP dissolution but was prevented by tyrosine kinase inhibitor pretreatment. This study suggests that exposure to AgNPs may elicit adverse mast cell responses that could contribute to the initiation or exacerbation of allergic disease.

A facile ultrasonication assisted method for Fe3O4@SiO2-Ag nanospheres with excellent antibacterial activity

A novel ultrasonication assisted method was developed to synthesize monodisperse Fe₃O₄@SiO₂-Ag nanospheres which exhibited excellent antibacterial activities against bothStaphylococcus aureusandEscherichia coli.

Advanced nanoarchitectures of silver/silver compound composites for photochemical reactions

Silver/silver compound (SSC) composites have received much attention as a type of potential materials in photochemical reactions due to their high efficiency, facile syntheses and availability of raw materials. This article reviews the state-of-the-art progress on the advanced nanoarchitectures of SSC composites. We begin with a survey on the general synthetic strategies for SSC composites, and then step into relatively detailed methods for size and morphology tunable two-component and more delicate multi-component SSC nanostructures. In addition, the electronic structure-related mechanisms of such materials and the recent studies on their stability are summarized. This review also highlights some perspectives on challenges related to the SSC composites and the possible research in the future.

Recent advances in synthesis and applications of clay-based photocatalysts: a review

Clay-based photocatalysts with high adsorbability and special structures have attracted extensive attention because of their applications in environment and energy fields.

Ion exchange and intercalation properties of layered double hydroxides towards halide anions

The selectivity towards halides and the mechanism of ion exchange of ZnAl-LDH in the chloride form (X⁻ = F⁻, Br⁻, I⁻) were investigated using ion exchange isotherms of Cl⁻/X⁻.

Redox properties of LDH microcrystals coated with a catechol-bearing phosphonate derived from dopamine

The surface of Zn–Al-chloride LDH microcrystals (LDH = Layered Double Hydroxides) was activated by grafting a redox active catechol bearing bis-phosphonate obtained by dopamine derivatization.