Silver-nanoparticle-embedded antimicrobial paints based on vegetable oil

Effects of Baseplates of Orthodontic Appliances with in situ generated Silver Nanoparticles on Cariogenic Bacteria: A Randomized, Double-blind Cross-over Clinical Trial

AIM

Polymethyl-methacrylate (PMMA) is commonly used primarily for baseplates of orthodontic appliances (BOA). The activities of cariogenic bacteria in biofilm on these surfaces may contribute to dental caries, gingival inflammation and periodontal disease. The PMMA incorporated with nanoparticles of silver (NanoAg-I-PMMA) and NanoAg in situ in PMMA (NanoAg-IS-PMMA) have been shown to control the growth of cariogenic bacteria, but clinical trial of anti-cariogenic application of these novel materials in orthodontics has not been evaluated. The main aim of the study is to compare the clinical effectiveness of using NanoAg-IS-PMMA and NanoAg-I-PMMA for construction of new BOA in inhibiting the planktonic growth and biofilm formation of the cariogenic bacteria.

MATERIALS AND METHODS

Twenty four patients with a median age of 12.6 years (7-15) harboring Streptococcus mutans, Streptococcus sobrinus and Lactobacillus acidophilus as well as Lactobacillus casei participated in the randomized, double-blind, cross-over study. The experimental BOA, NanoAg-IS-BOA and NanoAg-I-BOA, contained 0.5% w/w NanoAg while the control BOA was standard PMMA. Antibacterial effect of NanoAg-IS-BOA and NanoAg-I-BOA was assessed against test cariogenic bacteria by planktonic and biofilm bacterial cells growth inhibition.

RESULTS

The average levels of test cariogenic bacteria in saliva decreased about 2 to 70 fold (30.9-98.4%) compared to baseline depending on the microorganism type and test BOA. Biofilm inhibition analysis demonstrated that NanoAg-I-BOA and NanoAg-IS-BOA inhibited the biofilm of all test bacteria by 20.1 to 79.9% compared to BOA. NanoAg-IS-BOA had a strong anti-biofilm effect against S. mutans, S. sobrinus and L. casei. However, NanoAg-I-BOA showed only slight anti-biofilm effects on test bacteria. Most notably, at all period of the clinical trial, NanoAg-IS-BOA showed a higher antibacterial activity than NanoAg-I-BOA.

CONCLUSION

Based on the novel data that presented here, the NanoAg-IS-BOA had strong antimicrobial activity in the planktonic phase and subsequent biofilm formation of the cariogenic bacteria.

CLINICAL SIGNIFICANCE

Wearing of NanoAg-IS-BOA has the potential to minimize dental plaque formation and caries during orthodontic treatment.

ZnO nanoparticles impose a panmetabolic toxic effect along with strong necrosis, inducing activation of the envelope stress response in Salmonella enterica serovar Enteritidis

In this study, we tested the antimicrobial activity of three metal nanoparticles (NPs), ZnO, MgO, and CaO NPs, against Salmonella enterica serovar Enteritidis in liquid medium and on solid surfaces. Out of the three tested metal NPs, ZnO NPs exhibited the most significant antimicrobial effect both in liquid medium and when embedded on solid surfaces. Therefore, we focused on revealing the mechanisms of surface-associated ZnO biocidal activity. Using the global proteome approach, we report that a great majority (79%) of the altered proteins in biofilms formed by Salmonella enterica serovar Enteritidis were downregulated, whereas a much smaller fraction (21%) of proteins were upregulated. Intriguingly, all downregulated proteins were enzymes involved in a wide range of the central metabolic pathways, including translation; amino acid biosynthetic pathways; nucleobase, nucleoside, and nucleotide biosynthetic processes; ATP synthesis-coupled proton transport; the pentose phosphate shunt; and carboxylic acid metabolic processes, indicating that ZnO NPs exert a panmetabolic toxic effect on this prokaryotic organism. In addition to their panmetabolic toxicity, ZnO NPs induced profound changes in cell envelope morphology, imposing additional necrotic effects and triggering the envelope stress response of Salmonella serovar Enteritidis. The envelope stress response effect activated periplasmic chaperones and proteases, transenvelope complexes, and regulators, thereby facilitating protection of this prokaryotic organism against ZnO NPs.

Functionalized scaffolds to enhance tissue regeneration

Tissue engineering scaffolds play a vital role in regenerative medicine. It not only provides a temporary 3-dimensional support during tissue repair, but also regulates the cell behavior, such as cell adhesion, proliferation and differentiation. In this review, we summarize the development and trends of functional scaffolding biomaterials including electrically conducting hydrogels and nano-composites of hydroxyapatite (HA) and bioactive glasses (BGs) with various biodegradable polymers. Furthermore, the progress on the fabrication of biomimetic nanofibrous scaffolds from conducting polymers and composites of HA and BG via electrospinning, deposition and thermally induced phase separation is discussed. Moreover, bioactive molecules and surface properties of scaffolds are very important during tissue repair. Bioactive molecule-releasing scaffolds and antimicrobial surface coatings for biomedical implants and scaffolds are also reviewed.

Metal matrix-metal nanoparticle composites with tunable melting temperature and high thermal conductivity for phase-change thermal storage

Phase-change materials (PCMs) are of broad interest for thermal storage and management applications. For energy-dense storage with fast thermal charging/discharging rates, a PCM should have a suitable melting temperature, large enthalpy of fusion, and high thermal conductivity. To simultaneously accomplish these traits, we custom design nanocomposites consisting of phase-change Bi nanoparticles embedded in an Ag matrix. We precisely control nanoparticle size, shape, and volume fraction in the composite by separating the nanoparticle synthesis and nanocomposite formation steps. We demonstrate a 50-100% thermal energy density improvement relative to common organic PCMs with equivalent volume fraction. We also tune the melting temperature from 236-252 °C by varying nanoparticle diameter from 8.1-14.9 nm. Importantly, the silver matrix successfully prevents nanoparticle coalescence, and no melting changes are observed during 100 melt-freeze cycles. The nanocomposite's Ag matrix also leads to very high thermal conductivities. For example, the thermal conductivity of a composite with a 10% volume fraction of 13 nm Bi nanoparticles is 128 ± 23 W/m-K, which is several orders of magnitude higher than typical thermal storage materials. We complement these measurements with calculations using a modified effective medium approximation for nanoscale thermal transport. These calculations predict that the thermal conductivity of composites with 13 nm Bi nanoparticles varies from 142 to 47 W/m-K as the nanoparticle volume fraction changes from 10 to 35%. Larger nanoparticle diameters and/or smaller nanoparticle volume fractions lead to larger thermal conductivities.

Silver resistance in Gram-negative bacteria: a dissection of endogenous and exogenous mechanisms

Objectives

To gain a more detailed understanding of endogenous (mutational) and exogenous (horizontally acquired) resistance to silver in Gram-negative pathogens, with an emphasis on clarifying the genetic bases for resistance.

Methods

A suite of microbiological and molecular genetic techniques was employed to select and characterize endogenous and exogenous silver resistance in several Gram-negative species.

Results

In Escherichia coli, endogenous resistance arose after 6 days of exposure to silver, a consequence of two point mutations that were both necessary and sufficient for the phenotype. These mutations, in ompR and cusS, respectively conferred loss of the OmpC/F porins and derepression of the CusCFBA efflux transporter, both phenotypic changes previously linked to reduced intracellular accumulation of silver. Exogenous resistance involved derepression of the SilCFBA efflux transporter as a consequence of mutation in silS, but was additionally contingent on expression of the periplasmic silver-sequestration protein SilE. Silver resistance could be selected at high frequency (>10⁻⁹) from Enterobacteriaceae lacking OmpC/F porins or harbouring the sil operon and both endogenous and exogenous resistance were associated with modest fitness costs in vitro.

Conclusions

Both endogenous and exogenous silver resistance are dependent on the derepressed expression of closely related efflux transporters and are therefore mechanistically similar phenotypes. The ease with which silver resistance can become selected in some bacterial pathogens in vitro suggests that there would be benefit in improved surveillance for silver-resistant isolates in the clinic, along with greater control over use of silver-containing products, in order to best preserve the clinical utility of silver.

Understanding the pathway of antibacterial activity of copper oxide nanoparticles

This work investigates the role of oxidation state in the antibacterial activity of copper oxide nanoparticles (NPs).

ZnO/Ag micro/nanospheres with enhanced photocatalytic and antibacterial properties synthesized by a novel continuous synthesis method

A continuous concentric impinging stream method was used for preparing ZnO/Ag MNSs, which possessed excellent photocatalytic and antibacterial activities.

Plasmonic resonance of Ag nanoclusters diffused in soda-lime glasses

Silver nanoclusters were prepared in a soda-lime glass matrix through the ion-exchange method followed by thermal annealing. The work provides an insight into the nano-clustering and plasmonic effects of the nanoparticles.

One-step synthesis of Ag–reduced graphene oxide–multiwalled carbon nanotubes for enhanced antibacterial activities

A silver nanoparticles decorated reduced graphene oxide–multiwalled carbon nanotubes (Ag–rGO–MWCNTs) hybrid exhibits an excellent antibacterial activity against Escherichia coli (E. coli).

A novel non-releasing antibacterial poly(styrene-acrylate)/waterborne polyurethane composite containing gemini quaternary ammonium salt

Novel non-releasing antibacterial poly(styrene-acrylate)/waterborne polyurethane composites containing gemini quaternary ammonium salt were designed and preparedviaa facile blending strategy.

How morphology and surface crystal texture affect thermal stability of a metallic nanoparticle: the case of silver nanobelts and pentagonal silver nanowires

Nanobelts are a new type silver nanoparticle, more thermodynamically stable than other one-dimensional alternatives.

Influence of a blend of guar gum and poly(vinyl alcohol) on long term stability, and antibacterial and antioxidant efficacies of silver nanoparticles

A blend of guar gum and poly(vinyl alcohol) reduced and stabilized incipient silver nanoparticles which could be stored for 60 days. Silver nanoparticles also exhibited good antibacterial and antioxidant properties.

Opacity and plasmonic properties of Ag embedded glass based metamaterials

Opacity variations with increasing annealing temperatures in Ag⁺-exchange soda-lime glass.

Theranostic potentials of multifunctional chitosan–silver–phycoerythrin nanocomposites against triple negative breast cancer cells

Study focused to the applications of nanocomposites with therapeutic and imaging functions against TNBC cells. The developed multifunctional nanocomposites exhibited cell imaging, cytotoxicity with apoptosis induction against cancer cells.

Preparation of silver nanoparticles supported mesoporous silica microspheres with perpendicularly aligned mesopore channels and their antibacterial activities

In this study, a facile and effective route for the preparation of silver nanoparticle supported surface mesoporous silica microspheres with perpendicularly aligned mesopore channels and their antibacterial activities were reported.

Composite copolymer hybrid silver nanoparticles: preparation and characterization of antibacterial activity and cytotoxicity

The AgNPs could adhere to the bacterial membrane through electrostatic force, then damage the bacterial membrane irreversibly and lead to bacterial apoptosis finally.

Polyurethane-coated silica particles with broad-spectrum antibacterial properties

Antibacterial polyurethane-coated silica particles were synthesized using a “grafting to” approach via surface-to-end-group and surface-to-backbone strategies.

Enhanced colloidal stability and antibacterial performance of silver nanoparticles/cellulose nanocrystal hybrids

Preparation of polydopamine functionalized CNCs and silver nanoparticle immobilized CNCs.

Silver sputtering into a liquid matrix containing mercaptans: the systematic size control of silver nanoparticles in single nanometer-orders

A novel methodology to synthesize silver nanoparticles with precisely controlled diameters in single nano-meter orders by sputtering into a liquid matrix containing mercaptans as an environmental friendly preparation without reductants.

Synthesis of Ag@SiO2 yolk–shell nanoparticles for hydrogen peroxide detection

A novel nonenzymatic H₂O₂ sensor is fabricated based on Ag@SiO₂ yolk–shell nanoparticles (YSNs) via a sequential impregnation–reduction approach. These exhibit outstanding H₂O₂ reduction, with a fast amperometric response, a low detection limit and a wide linear range.

Water soluble blue-emitting AuAg alloy nanoparticles and fluorescent solid platforms for removal of dyes from water

We report here the successful formation of blue-emitting AuAg alloy nanoparticles and a solid fluorescent platform by a biotemplate-induced reduction process using egg shell membrane, and the applications of the nanoparticles.

Role of synergistic π–π stacking and X–H⋯Cl (X = C, N, O) H-bonding interactions in gelation and gel phase crystallization

Gel phase crystallization in a transparent gel via synergistic non-covalent interactions has been reported along with various remarkable features.

Refractive index determination of nanoparticles in suspension using nanoparticle tracking analysis

The refractive index (RI) dictates interaction between light and nanoparticles and therefore is important to health, environmental, and materials sciences. Using nanoparticle tracking analysis, we have determined the RI of heterogeneous particles <500 nm in suspension. We demonstrate feasibility of distinguishing silica and polystyrene beads based on their RI. The hitherto unknown RI of extracellular vesicles from human urine was determined at 1.37 (mean). This method enables differentiation of single nanoparticles based on their RI.

Biosynthesis of Ag nanoparticles using pedicellamide and its photocatalytic activity: an eco-friendly approach

The synthesis of silver (Ag) nanoparticles using by pedicellamide (A), isolated from Piper pedicellatum C.DC leaf is demonstrated here. TEM analysis revealed that the Ag nanoparticles predominantly form spherical in shape. The compound 'A' act as a reducing, stabilizing and capping agent. The reaction mechanism was established by using density functional theory (DFT). Photocatalytic property of the Ag nanoparticles is investigated by degradation of Methyl Red (MR) dye under UV light. The kinetic, reaction mechanism and rate constant of photocatalytic degradation of MR was evaluated. The results show that Ag nanoparticles have suitable photocatalytic activity for the degradation of MR dye.

Catalytically and biologically active silver nanoparticles synthesized using essential oil

There are numerous reports on phytosynthesis of silver nanoparticles and various phytochemicals are involved in the reduction and stabilization. Pure explicit phytosynthetic protocol for catalytically and biologically active silver nanoparticles is of importance as it is an environmentally benign green method. This paper reports the use of essential oil of Myristica fragrans enriched in terpenes and phenyl propenes in the reduction and stabilization. FTIR spectra of the essential oil and the synthesized biogenic silver nanoparticles are in accordance with the GC-MS spectral analysis reports. Nanosilver is initially characterized by an intense SPR band around 420 nm, followed by XRD and TEM analysis revealing the formation of 12-26 nm sized, highly pure, crystalline silver nanoparticles. Excellent catalytic and bioactive potential of the silver nanoparticles is due to the surface modification. The chemocatalytic potential of nanosilver is exhibited by the rapid reduction of the organic pollutant, para nitro phenol and by the degradation of the thiazine dye, methylene blue. Significant antibacterial activity of the silver colloid against Gram positive, Staphylococcus aureus (inhibition zone--12 mm) and Gram negative, Escherichia coli (inhibition zone--14 mm) is demonstrated by Agar-well diffusion method. Strong antioxidant activity of the biogenic silver nanoparticles is depicted through NO scavenging, hydrogen peroxide scavenging, reducing power, DPPH and total antioxidant activity assays.

Histopathological and ultra structural effects of nanoparticles on rat testis following 90 days (Chronic study) of repeated oral administration

Background

Nanoparticles (Ag NPs) have recently received much attention for their possible applications in biotechnology and biomedical. However, little is known about the toxicity in reproductive organs of animal model following exposure to nanoparticles.

Objective

This study therefore, tried to examine the effects of nanoparticles with a diameter range of 5-20 nm on the histology of the testis of wistar rats and correlate it with Transmission Electron Microscopy results.

Materials and methods

Sixteen wistar rats were randomly divided into two groups of 8 rats each. Each group received the following via gavage technique for 90 days: Control Group (Group-1)-tap water; Experimental group (Group 2) - nanoparticles (20ug/kg/day). After ninety days (chronic study), rats were sacrificed and testis tissues was processed for histology and transmission electron microscopic study.

Results

There was significant difference between the observations of group-1 and group 2. The changes observed in the testis were disarray of the spermatogenic cells and disorientation of the testis. These changes were observed to have been disappearing from normal histological features. Detailed structural damages were observed with TEM analysis, such as depletion of germ cells, germinal cells necrosis, especially in spermatogonia and Leydig cells had an abnormal fibroblast-like appearance, abnormal space between neighboring sertoli cells, mitochondria, lost cristae and vacuolated (none energized) with those animals exposed to nanoparticles.

Conclusion

It seems that nanoparticles have acute and significant effects on spermatogenesis and number of spermatogenic cells. More experimental investigations are necessary to elucidate better conclusion regarding the safety of nanoparticles on male reproduction system.

Lysozyme-coated silver nanoparticles for differentiating bacterial strains on the basis of antibacterial activity

Lysozyme, an antibacterial enzyme, was used as a stabilizing ligand for the synthesis of fairly uniform silver nanoparticles adopting various strategies. The synthesized particles were characterized using UV-visible spectroscopy, FTIR, dynamic light scattering (DLS), and TEM to observe their morphology and surface chemistry. The silver nanoparticles were evaluated for their antimicrobial activity against several bacterial species and various bacterial strains within the same species. The cationic silver nanoparticles were found to be more effective against Pseudomonas aeruginosa 3 compared to other bacterial species/strains investigated. Some of the bacterial strains of the same species showed variable antibacterial activity. The difference in antimicrobial activity of these particles has led to the conclusion that antimicrobial products formed from silver nanoparticles may not be equally effective against all the bacteria. This difference in the antibacterial activity of silver nanoparticles for different bacterial strains from the same species may be due to the genome islands that are acquired through horizontal gene transfer (HGT). These genome islands are expected to possess some genes that may encode enzymes to resist the antimicrobial activity of silver nanoparticles. These silver nanoparticles may thus also be used to differentiate some bacterial strains within the same species due to variable silver resistance of these variants, which may not possible by simple biochemical tests.

Opportunities and challenges of nanotechnology in the green economy

In a world of finite resources and ecosystem capacity, the prevailing model of economic growth, founded on ever-increasing consumption of resources and emission pollutants, cannot be sustained any longer. In this context, the "green economy" concept has offered the opportunity to change the way that society manages the interaction of the environmental and economic domains. To enable society to build and sustain a green economy, the associated concept of "green nanotechnology" aims to exploit nano-innovations in materials science and engineering to generate products and processes that are energy efficient as well as economically and environmentally sustainable. These applications are expected to impact a large range of economic sectors, such as energy production and storage, clean up-technologies, as well as construction and related infrastructure industries. These solutions may offer the opportunities to reduce pressure on raw materials trading on renewable energy, to improve power delivery systems to be more reliable, efficient and safe as well as to use unconventional water sources or nano-enabled construction products therefore providing better ecosystem and livelihood conditions.However, the benefits of incorporating nanomaterials in green products and processes may bring challenges with them for environmental, health and safety risks, ethical and social issues, as well as uncertainty concerning market and consumer acceptance. Therefore, our aim is to examine the relationships among guiding principles for a green economy and opportunities for introducing nano-applications in this field as well as to critically analyze their practical challenges, especially related to the impact that they may have on the health and safety of workers involved in this innovative sector. These are principally due to the not fully known nanomaterial hazardous properties, as well as to the difficulties in characterizing exposure and defining emerging risks for the workforce. Interestingly, this review proposes action strategies for the assessment, management and communication of risks aimed to precautionary adopt preventive measures including formation and training of employees, collective and personal protective equipment, health surveillance programs to protect the health and safety of nano-workers. It finally underlines the importance that occupational health considerations will have on achieving an effectively sustainable development of nanotechnology.

Antimicrobial activity of cobalt imidazolate metal-organic frameworks

Two cobalt imidazolate metal-organic frameworks were evaluated as a bactericidal material against the growth of the Gram-negative bacteria Pseudomonas putida and Escherichia coli. Under the most unfavourable conditions, within the exponential growth phase and in the culture media for both microorganisms, the growth inhibition reached over 50% for concentrations of biocidal material in the 5-10mgL(-1) range. The release of metal gives excellent durability with the antibacterial effect persisting after 3months. Both cobalt-based materials can be prepared with simple, cheap and easily accessible commercial ligands, leading to a more affordable possible future application as antimicrobial materials.

Coconut water assisted green synthesis of silver nanoparticles

AIM OF THE STUDY

The synthesis, characterization and application of biologically synthesized nanomaterials are an important aspect in nanotechnology.

MATERIALS AND METHODS

The present study deals with the synthesis of silver nanoparticles (Ag-NPs) using the coconut water (C. nucifera) as the reducing agent. The formation of Ag-NPs was characterized by UV-Visible Spectroscopy, Scanning Electron Microscopy (SEM), EDX, X-ray Diffraction (XRD) and FTIR spectroscopy.

RESULTS

The synthesized Ag-NPs were predominately polydispersed. Crystalline nature of the nanoparticle in the face centered cubic (fcc) structure are confirmed by the peaks in the XRD pattern corresponding to (111), (200), (220) and (311) planes. Fourier Transform Infra-Red (FT-IR) spectroscopy analysis showed that the synthesized nanoparicles was capped with bimolecular compounds which are responsible for the reduction of silver ions.

CONCLUSION

The approach of green synthesis appears to be cost efficient, ecofriendly and easy alternative to conventional methods of silver nanoparticle synthesis.

Fabrication of SWCNT-Ag nanoparticle hybrid included self-assemblies for antibacterial applications

The present article reports the development of soft nanohybrids comprising of single walled carbon nanotube (SWCNT) included silver nanoparticles (AgNPs) having superior antibacterial property. In this regard aqueous dispersing agent of carbon nanotube (CNT) containing a silver ion reducing unit was synthesised by the inclusion of tryptophan and tyrosine within the backbone of the amphiphile. The dispersions were characterized spectroscopically and microscopically using TEM, AFM and Raman spectroscopy. The nanotube-nanoparticle conjugates were prepared by the in situ photoreduction of AgNO3. The phenolate residue and the indole moieties of tyrosine and tryptophan, respectively reduces the sliver ion as well as acts as stabilizing agents for the synthesized AgNPs. The nanohybrids were characterized using TEM and AFM. The antibacterial activity of the nanohybrids was studied against Gram-positive (Bacillus subtilis and Micrococcus luteus) and Gram-negative bacteria (Escherichia coli and Klebsiella aerogenes). The SWCNT dispersions showed moderate killing ability (40-60%) against Gram-positive bacteria however no antibacterial activity was observed against the Gram negative ones. Interestingly, the developed SWCNT-amphiphile-AgNP nanohybrids exhibited significant killing ability (∼90%) against all bacteria. Importantly, the cell viability of these newly developed self-assemblies was checked towards chinese hamster ovarian cells and high cell viability was observed after 24 h of incubation. This specific killing of bacterial cells may have been achieved due to the presence of higher -SH containing proteins in the cell walls of the bacteria. The developed nanohybrids were subsequently infused into tissue engineering scaffold agar-gelatin films and the films similarly showed bactericidal activity towards both kinds of bacterial strains while allowing normal growth of eukaryotic cells on the surface of the films.

Fluorinated TiO₂ as an ambient light-activated virucidal surface coating material for the control of human norovirus

We evaluated the virucidal efficacy of light-activated fluorinated TiO₂ surface coatings on human norovirus and several surrogates (bacteriophage MS2, feline calcivirus (FCV), and murine norovirus (MNV)). Inactivation of viruses on surfaces exposed to a common fluorescent lamp was monitored and the effects of UVA intensity, temperature, and fluoride content were assessed. Destruction of RNA and capsid oxidation were evaluated for human norovirus inocula on the F-TiO₂ surfaces, while contact with the F-TiO₂ surface and exposure to residual UVA radiation of 10 μW cm(-2) for 60 min resulted in infectivity reductions for the norovirus surrogates of 2-3 log₁₀. Infectivity reductions on pristine TiO₂ surfaces in identical conditions were over 2 orders of magnitude lower. Under realistic room lighting conditions, MS2 infectivity declined below the lower detection limit after 12h. Reductions in RNA were generally low, with the exception of GII.4, while capsid protein oxidation likely played a larger role in infectivity loss. Inactivation of norovirus surrogates occurred significantly faster on F-TiO₂ compared to pristine TiO₂ surfaces. The material demonstrated antiviral action against human norovirus surrogates and was shown to effectively inhibit MS2 when exposed to residual UVA present in fluorescent room lighting conditions in a laboratory setting.

Nanostructured molybdenum oxide-based antibacterial paint: effective growth inhibition of various pathogenic bacteria

The prevention of bacterial infections in the health care environment is paramount to providing better treatment. Covering a susceptible environment with an antimicrobial coating is a successful way to avoid bacterial growth. Research on the preparation of durable antimicrobial coatings is promising for both fundamental surface care and clinical care applications. Herein, we report a facile, efficient, and scalable preparation of MoO3 paint using a cost-effective ball-milling approach. The MoO3 nanoplates (synthesized by thermal decomposition of ammonium heptamolybdate) are used as a pigment and antibacterial activity moiety in alkyd resin binders and other suitable eco-friendly additives in the preparation of paint. Surface morphology, chemical states, bonding nature, and intermolecular interaction between the MoO3 and the alkyd resin were studied using Raman and x-ray photoelectron spectroscopic analysis. The antibacterial properties of a prepared MoO3 nanoplate against various bacterial strains (Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus, and Klebsiella pneumoniae) was determined using the microdilution method. Bacterial strains exposed to an MoO3 paint coated surface exhibit a significant loss of viability in a time-dependent manner. Fundamental modes of antibacterial activities ascribed from a biocompatible and durable MoO3 nanostructure incorporated into an alkyd resin complex are discussed. The obtained experimental findings suggest the potential utility of prepared MoO3-based paint coating for the prevention of health care associated infections.

Exploring silver as a contrast agent for contrast-enhanced dual-energy X-ray breast imaging

OBJECTIVE

Through prior monoenergetic modelling, we have identified silver as a potential alternative to iodine in dual-energy (DE) X-ray breast imaging. The purpose of this study was to compare the performance of silver and iodine contrast agents in a commercially available DE imaging system through a quantitative analysis of signal difference-to-noise ratio (SDNR).

METHODS

A polyenergetic simulation algorithm was developed to model the signal intensity and noise. The model identified the influence of various technique parameters on SDNR. The model was also used to identify the optimal imaging techniques for silver and iodine, so that the two contrast materials could be objectively compared.

RESULTS

The major influences on the SDNR were the low-energy dose fraction and breast thickness. An increase in the value of either of these parameters resulted in a decrease in SDNR. The SDNR for silver was on average 43% higher than that for iodine when imaged at their respective optimal conditions, and 40% higher when both were imaged at the optimal conditions for iodine.

CONCLUSION

A silver contrast agent should provide benefit over iodine, even when translated to the clinic without modification of imaging system or protocol. If the system were slightly modified to reflect the lower k-edge of silver, the difference in SDNR between the two materials would be increased.

ADVANCES IN KNOWLEDGE

These data are the first to demonstrate the suitability of silver as a contrast material in a clinical contrast-enhanced DE image acquisition system.

Ag nanoprisms with Ag₂S attachment

Triangular Ag nanoprisms are a type of most-studied noble-metal nanostructures over the past decade owing to their special structural architecture and outstanding optical and catalytic properties for a wide range of applications. Nevertheless, in contrast to active research for the synthesis of phase-pure Ag nanoprisms, no asymmetric heterodimers containing Ag prisms have been developed so far, probably due to lack of suitable synthetic methods. Herein, we devise a simple ion-exchange method to synthesize Ag2S/Ag heterodimers at room temperature, through which Ag nanoprisms with controllable size and thickness can be fabricated. Formation chemistry and optical properties of the heterodimers have been investigated. These semiconductor/metal heterodimers have exhibited remarkable bactericidal activity to E. coli cells under visible light illumination.

Graphene-based nanocomposite as an effective, multifunctional, and recyclable antibacterial agent

The development of new antibacterial agents that are highly effective are of great interest. Herein, we present a recyclable and synergistic nanocomposite by growing both iron oxide nanoparticles (IONPs) and silver nanoparticles (AgNPs) on the surface of graphene oxide (GO), obtaining GO-IONP-Ag nanocomposite as a novel multifunctional antibacterial material. Compared with AgNPs, which have been widely used as antibacterial agents, our GO-IONP-Ag shows much higher antibacterial efficiency toward both Gram-negative bacteria Escherichia coli (E. coli) and Gram-positive bacteria Staphylococcus aureus (S. aureus). Taking the advantage of its strong near-infrared (NIR) absorbance, photothermal treatment is also conducted with GO-IONP-Ag, achieving a remarkable synergistic antibacterial effect to inhibit S. aureus at a rather low concentration of this agent. Moreover, with magnetic IONPs existing in the composite, we can easily recycle GO-IONP-Ag by magnetic separation, allowing its repeated use. Given the above advantages as well as its easy preparation and cheap cost, GO-IONP-Ag developed in this work may find potential applications as a useful antibacterial agent in the areas of healthcare and environmental engineering.