Silver nanoparticle ecotoxicity and phytoremediation: a critical review of current research and future prospects

Silver nanoparticles (AgNPs) are widely used in various industries, including textiles, electronics, and biomedical fields, due to their unique optical, electronic, and antimicrobial properties. However, the extensive use of AgNPs has raised concerns about their potential ecotoxicity and adverse effects on the environment. AgNPs can enter the environment through different pathways, such as wastewater, surface runoff, and soil application and can interact with living organisms through adsorption, ingestion, and accumulation, causing toxicity and harm. The small size, high surface area-to-volume ratio, and ability to generate reactive oxygen species (ROS) make AgNPs particularly toxic. Various bioremediation strategies, such as phytoremediation, have been proposed to mitigate the toxic effects of AgNPs and minimize their impact on the environment. Further research is needed to improve these strategies and ensure their safety and efficacy in different environmental settings.

Eco-friendly Synthesis of Silver Nanoparticles and its Application in Hydrogen Photogeneration and Nanoplasmonic Biosensing

Environmentally friendly methods for silver nanoparticles (AgNPs) synthesis without the use of hazardous chemicals have recently drawn attention. In this work, AgNPs have been synthesized by microwave irradiation using only honey solutions or aqueous fresh pink radish extracts. The concentrations of honey, radish extract, AgNO3 and pH were varied. AgNPs presented mean sizes between 7.0 and 12.8 nm and were stable up to 120 days. The AgNPs were employed as co-catalyst (TiO2 @AgNPs) to increase the hydrogen photogeneration under UV-vis and only visible light irradiation, when compared to pristine TiO2 NPs. The prepared photocatalyst also showed hydrogen generation under visible light. Additionally, AgNPs were used to assemble a nanoplasmonic biosensor for the biodetection of extremely low concentrations of streptavidin, owing to its specific binding to biotin. It is shown here that green AgNPs are versatile nanomaterials, thus being potential candidates for hydrogen photogeneration and biosensing applications.

Interplay between Nanoparticles and Phosphorus Dendrimers, and Their Properties

This review presents the state of the art of interactions between two different families of nanoobjects: nanoparticles-mainly metal nanoparticles, and dendrimers-mainly phosphorhydrazone dendrimers (or dendrons). The review firstly presents the encapsulation/protection of existing nanoparticles (organic or metallic) by phosphorus-based dendrimers and dendrons. In the second part, several methods for the synthesis of metal nanoparticles, thanks to the dendrimer that acts as a template, are presented. The properties of the associations between dendrimers and nanoparticles are emphasized throughout the review. These properties mainly concern the elaboration of diverse types of hybrid materials, some of them being used as sensitive chemosensors or biosensors. Several examples concerning catalysis are also given, displaying in particular the efficient recovery and reuse of the catalytic entities.

Thermoresponsive Zinc TetraPhenylPorphyrin Photosensitizer/Dextran Graft Poly(N-IsoPropylAcrylAmide) Copolymer/Au Nanoparticles Hybrid Nanosystem: Potential for Photodynamic Therapy Applications

The thermoresponsive Zinc TetraPhenylPorphyrin photosensitizer/Dextran poly (N-isopropylacrylamide) graft copolymer/Au Nanoparticles (ZnTPP/D-g-PNIPAM/AuNPs) triple hybrid nanosystem was synthesized in aqueous solution as a nanodrug for potential use in thermally driven and controlled photodynamic therapy applications. The aqueous solution of the nanosystem has demonstrated excellent stability in terms of aggregation and sedimentation several days after preparation. Optimal concentrations of the components of hybrid nanosystem providing the lowest level of aggregation and the highest plasmonic enhancement of electronic processes in the photosensitizer molecules have been determined. It has been revealed that the shrinking of D-g-PNIPAM macromolecule during a thermally induced phase transition leads to the release of both ZnTPP molecules and Au NPs from the ZnTPP/D-g-PNIPAM/AuNPs macromolecule and the strengthening of plasmonic enhancement of the electronic processes in ZnTPP molecules bound with the polymer macromolecule. The 2.7-fold enhancement of singlet oxygen photogeneration under resonant with surface plasmon resonance has been observed for ZnTPP/D-g-PNIPAM/AuNPs proving the plasmon nature of such effect. The data obtained in vitro on wild strains of Staphylococcus aureus have proved the high potential of such nanosystem for rapid photodynamic inactivation of microorganisms particular in wounds or ulcers on the body surface.

Current and promising pharmacotherapeutic options for candidiasis

Introduction: Candida spp. are commensal yeasts capable of causing infections such as superficial, oral, vaginal, or systemic infections. Despite medical advances, the antifungal pharmacopeia remains limited and the development of alternative strategies is needed.Areas covered: We discuss available treatments for Candida spp. infections, highlighting advantages and limitations related to pharmacokinetics, cytotoxicity, and antimicrobial resistance. Moreover, we present new perspectives to improve the activity of the available antifungals, discussing their immunomodulatory potential and advances on drug delivery carriers. New therapeutic approaches are presented including recent synthesized antifungal compounds (Enchochleated-Amphotericin B, tetrazoles, rezafungin, enfumafungin, manogepix and arylamidine); drug repurposing using a diversity of antibacterial, antiviral and non-antimicrobial drugs; combination therapies with different compounds or photodynamic therapy; and innovations based on nano-particulate delivery systems.Expert opinion: With the lack of novel drugs, the available assets must be leveraged to their best advantage through modifications that enhance delivery, efficacy, and solubility. However, these efforts are met with continuous challenges presented by microbes in their infinite plight to resist and survive therapeutic drugs. The pharmacotherapeutic options in development need to focus on new antimicrobial targets. The success of each antimicrobial agent brings strategic insights to the next phased approach in treatingCandida spp. infections.

Efficient loading of silver nanoparticles on graphene oxide and its antibacterial properties

Graphene oxide contains polyaromatic structure and a variety of oxygen functional groups, which can form π-type metal ion-aromatic or metal ion-oxygen interaction with transition metals, thus it is a promising dispersant and carrier for silver nanoparticles (AgNPs). Herein, silver nanoparticles/reduced graphene oxide (AgNPs/rGO) was fabricated with scalable synthesis method without additional dispersing agent. The mass percent of AgNPs loading on rGO could be adjusted according to the requirement of applications from 1 ∼ 67% of the total weight of AgNPs/rGO with the sizes of AgNPs 10 ∼ 30 nm. AgNPs/rGO exhibited excellent antibacterial activity towards both gram-positive S. aureus and gram-negative E. coli. In addition, AgNPs/rGO could be easily dispersed in liquid silicone rubber, and when the rubber solidified and formed a three-dimensional structure, AgNPs/rGO-silicone rubber has both effective antibacterial property and very low effusion of AgNPs. This composite has potential to be used as a material of bacteriostasis bottles and wound dressings.

Antibacterial activity of chlorogenic acid-loaded SiO2 nanoparticles caused by accumulation of reactive oxygen species

Diseases caused by pathogenic bacilli pose an increasing threat to human health. A common feature of these bacteria is a complete cell wall; therefore, drugs that can penetrate this protective barrier could be used as a novel approach for treating these infections. Here we present a simple method for synthesizing a silica mesoporous material loaded with cadmium selenide (CdSe) and chlorogenic acid. Using UV-visible, fluorescence, and infrared imaging in combination with transmission electron microscopy, it was shown that CdSe and chlorogenic acid could be successfully embedded in the mesopores of silica nanoparticles (CSC NPs), and these NPs presented with a strong fluorescence, uniform size, and good dispersion. Additionally, the results of these analyses indicated that the fluorescence of the CSC NPs was localized within the cells of Escherichia coli and Bacillus subtilis, signifying that these NPs could breach the cell wall and enter the cells of these two bacilli. Additional assessments found that these CSC NPs inhibited the proliferation of the bacteria by disrupting the cell wall, and this was most likely due to the overproduction of reactive oxygen species induced by chlorogenic acid. Importantly, histopathology analysis indicated that the CSC NPs had limited side effects and high biocompatibility.

Enzyme-Responsive Ag Nanoparticle Assemblies in Targeting Antibacterial against Methicillin-Resistant Staphylococcus Aureus

The abuse of antibiotics resulted in the emergence of antibiotics-resistant bacteria, which has raised a great social concern together with the impetus to develop effective antibacterial materials. Herein, the synthesis of biocompatible enzyme-responsive Ag nanoparticle assemblies (ANAs) and their application in the high-efficiency targeted antimicrobial treatment of methicillin-resistant Staphylococcus aureus (MRSA) have been demonstrated. The ANAs could collapse and undergo stable/collapsed transition on approaching MRSA because of the serine protease-like B enzyme proteins (SplB)-triggered decomposition of the branched copolymers which have been employed as the macrotemplate in the synthesis of responsive ANAs. This transition contributed greatly to the high targeting affinity and efficiency of ANAs to MRSA. The minimum inhibitory concentration and minimum bactericidal concentration against MRSA were 2.0 and 32.0 μg mL^-1, respectively. Skin wound healing experiments confirmed that the responsive ANAs could serve as an effective wound dressing to accelerate the healing of MRSA infection.

Synthesis of Silver Nanoparticles Loaded onto Polymer-Inorganic Composite Materials and Their Regulated Catalytic Activity

We present a novel approach for the preparation of polymer-TiO₂ composite microgels. These microgels were prepared by the in situ hydrolysis and condensation of titanium tetrabutoxide (TBOT) in a mixed ethanol/acetonitrile solvent system, using poly(styrene-co-N-isopropylacrylamide)/poly(N-isopropylacrylamide-co-methacrylic acid) (P(St-NIPAM/P(NIPAM-co-MAA)) as the core component. Silver nanoparticles (AgNPs) were controllably loaded onto the polymer-TiO₂ composite microgels through the reduction of an ammoniacal silver solution in ethanol catalyzed by NaOH. The results showed that the P(St-NIPAM)/P(NIPAM-co-MAA)-TiO₂ (polymer-TiO₂) organic-inorganic composite microgels were less thermally sensitive than the polymer gels themselves, owing to rigid O–Ti–O chains introduced into the three-dimensional framework of the polymer microgels. The sizes of the AgNPs and their loading amount were controlled by adjusting the initial concentration of [Ag(NH₃)₂]⁺. The surface plasmon resonance (SPR) band of the P(St-NIPAM)/P(NIPAM-co-MAA)-TiO₂/Ag (polymer-TiO₂/Ag) composite microgels can be tuned by changing the temperature of the environment. The catalytic activities of the polymer-TiO₂/Ag composite microgels were investigated in the NaBH₄ reduction of 4-nitrophenol. It was demonstrated that the organic-inorganic network chains of the polymer microgels not only favor the mass transfer of the reactant but can also modulate the catalytic activities of the AgNPs by tuning the temperature.

Effect of polyhexamethylene biguanide functionalized silver nanoparticles on the growth of Staphylococcus aureus

Polyhexamethylene biguanide (PHMB) was used as a stabilizing ligand to synthesize uniform silver nanoparticles (Ag NPs). The effects and action mechanism of PHMB functionalized Ag NPs (Ag NPs-PHMB) on the growth of the Gram-positive bacteria Staphylococcus aureus were investigated. The results showed that a high concentration Ag NPs-PHMB could be obtained and prepared particles were fairly uniform. Prepared Ag NPs-PHMB enhanced the bactericidal effect and the log kill reached 5.06 when S. aureus was exposed to Ag NPs-PHMB for 20 min. Ag NPs-PHMB caused damage to cell wall, a decrease in the membrane fluidity, and leakage of K+, Mg2+, ATP and proteins from the cell, eventually leading to the death of S. aureus.

Rapid and sensitive colorimetric detection of pathogens based on silver–urease interactions

Herein, we demonstrate a facile and economic approach for colorimetric detection of microbial pathogens in drinking water, employing silver–urease interactions.

Exploiting Synergetic Effects of Graphene Oxide and a Silver-Based Metal-Organic Framework To Enhance Antifouling and Anti-Biofouling Properties of Thin-Film Nanocomposite Membranes

Thin-film composite (TFC) membranes still suffer from fouling and biofouling. In this work, by incorporating a graphene oxide (GO)-silver-based metal-organic framework (Ag-MOF) into the TFC selective layer, we synthesized a thin-film nanocomposite (TFN) membrane that has notably improved anti-biofouling and antifouling properties. The TFN membrane has a more negative surface charge, higher hydrophilicity, and higher water permeability compared with the TFC membrane. Fluorescence imaging revealed that the GO-Ag-MOF TFN membrane kills Escherichia (E.) coli more than the Ag-MOF TFN, GO TFN, and pristine TFC membranes by 16, 30, and 92%, respectively. Forward osmosis experiments with E. coli and sodium alginate suspensions showed that the GO-Ag-MOF TFN membrane by far has the lowest water flux reduction among the four membranes, proving the exceptional anti-biofouling and antifouling properties of the GO-Ag-MOF TFN membrane.

Antimicrobial activity of nano-sized silver colloids stabilized by nitrogen-containing polymers: the key influence of the polymer capping

Synthesis of stable silver colloids was achieved using nitrogen-containing polymers acting simultaneously as a reducing and stabilizer agent. The polymers polyethyleneimine (PEI), polyvinylpyrrolidone (PVP) and poly(2-vinyl pyridine)-b-poly(ethylene oxide) (PEO-b-P2VP) were used in the procedures. The influence of the surface chemistry and chemical nature of the stabilizer on the cytotoxicity and antimicrobial properties have been evaluated. The produced nanomaterials were found to be non-toxic up to the highest evaluated concentration (1.00 ppm). Nevertheless, at this very low concentration, the AgNPs stabilized by PVP and PEO-b-P2VP were found to be remarkable biocides against bacteria and fungus. On the other hand, we have surprisingly evidenced negligible antimicrobial activity of AgNPs stabilized by positively charged PEI although both (AgNPs and PEI) materials separately are known for their antimicrobial activity as also evidenced in the current investigation. The evidence is claimed to be related to the blocking of Ag+ kinetic release. Accordingly, the antimicrobial effect of nano-sized silver colloids largely depends on the chemical nature of the polymer coating. Possibly, the outstanding colloid stabilization provided by polyethyleneimine slows down Ag+ release thereby hampering its biological activity whereas the poorer stabilization and good ionic transport property of PVP and PEO-b-P2VP allows much faster ion release and cell damage.

Laser-driven structural transformations in dextran-graft-PNIPAM copolymer/Au nanoparticles hybrid nanosystem: the role of plasmon heating and attractive optical forces

Structural transformations in D-g-PNIPAM/AuNPs hybrid nanosystem arise from the synergetic action of plasmonic heating and attractive optical plasmonic forces.

Plant extracts as green reductants for the synthesis of silver nanoparticles: lessons from chemical synthesis

From conventional synthesis to green transformations: a brief literature overview and insight for the synthesis of Ag nanoparticles.

Improvement of Cochineal Extract (Dactylopius coccus Costa) Properties Based on the Green Synthesis of Silver Nanoparticles for Application in Organic Devices

The UV-Vis absorption and conductivity properties of the organic sample cochineal (Dactylopius coccus Costa) were modified by using it as a reducing agent in the biosynthesis of silver nanoparticles. This was done in a straightforward way in order to allow its possible application in organic devices. The biosynthesized solution exhibited a hybrid material with a UV-Vis absorbance range from 205 to 650 nm. The sizes of silver nanoparticles of the hybrid material were between 5 and 10 nm. X-ray diffraction (XRD) revealed silver structures, when samples were dried at 100°C. At 40°C, the structures detected were chlorargyrite (AgCl) and silver oxide (Ag2O). The nucleation and subsequent growth of the hybrid thin film on the substrates indicated an increase of clusters and roughness in comparison to thin films made solely from cochineal. The thin films of hybrid materials showed an improvement of 40% in their electrical potential. The stability at room temperature demonstrated that the hybrid material could be useful as a potential candidate for photoactive thin films in organic devices.

Challenges in Application of Langmuir Monolayer Studies To Determine the Mechanisms of Bactericidal Activity of Ruthenium Complexes

The effects induced by antibiotics on the bacterial membrane may be correlated with their bactericidal activity, and such molecular-level interactions can be probed with Langmuir monolayers representing the cell membrane. In this study, we investigated the interaction between [Ru(mcbtz)₂(PPh₃)₂] (RuBTZ, mcbtz = 2-mercaptobenzothiazoline) and [Ru(mctz)₂(PPh₃)₂] (RuCTZ, mctz = 2-mercaptothiazoline) with Langmuir monolayers of a lipid extract of Escherichia coli, an extract of lipopolysaccharides (LPSs), and a zwitterionic phospholipid, dioleoylphosphatidyl choline (DOPC). RuBTZ and RuCTZ had little effects on DOPC, which is consistent with their negligible toxicity toward mammalian cells that may be approximated by a zwitterionic monolayer. Also little were their effects on LPSs. In contrast, RuBTZ and RuCTZ induced expansion in the surface pressure isotherms and decreased the compressional modulus of the E. coli lipid extract. While the more hydrophobic RuBTZ seemed to affect the hydrophobic tails of the E. coli extract monolayer to a larger extent, according to polarization modulation infrared reflection absorption spectroscopy results, evidence of a stronger RuBTZ interaction could not be confirmed unequivocally. Therefore, the interaction with the E. coli cell membrane cannot be directly correlated with the observed higher bactericidal activity of RuBTZ, in comparison to that of RuCTZ. This appears to be a case in which Langmuir monolayer studies do not suffice to determine the mechanisms responsible for the bactericidal activity.

Biomolecular corona formation: nature and bactericidal impact on surface-modified silica nanoparticles

Biological fluids contain a plethora of different components that can coat nanoparticle's surface and critically affect their interaction with living systems. The recent literature has focused efforts on understanding the overall protein role in this nanoparticle's coating (commonly called a protein corona) without considering other components' influence. Here, we report a protocol to study the relationship between biological fluid components excluding proteins (referred to as a biomolecular corona) and nanoparticles. For this purpose, functionalized silica nanoparticles were duly synthesized to experimentally investigate the extent of biomolecular corona adsorption over different surfaces. This adsorption was directly correlated with the silica surface chemical constitution, while the extent of biomolecular corona coating affected the overall surface charge and the colloidal stability of the functionalized nanoparticles. In addition, the bactericidal properties of biomolecular corona-coated nanoparticles were tested against two medically relevant bacteria (Escherichia coli and Staphylococcus aureus). Biological results indicated that the presence and the extent of the biomolecular corona affect the bactericidal properties of the nanoparticles.

Synergistic Bacteria Killing through Photodynamic and Physical Actions of Graphene Oxide/Ag/Collagen Coating

Researchers have widely agreed that the broad spectrum antibacterial activity of silver nanoparticles (AgNPs) can be predominantly ascribed to the action of Ag⁺. This study marks the first report detailing the rapid and highly efficient synergistic bacteria killing of AgNPs, which is achieved by inspiring AgNPs' strong photocatalytic capability to rapidly produce radical oxygen species using 660 nm visible light together with the innate antimicrobial ability of Ag⁺. These AgNPs were uniformly distributed into well-defined graphene oxide (GO) nanosheets through an in situ reduction of Ag⁺ and subsequently wrapped with a thin layer of type I collagen. In vivo subcutaneous tests demonstrated that 20 min irradiation of 660 nm visible light could achieve a high antibacterial efficacy of 96.3% and 99.4% on the implant surface against Escherichia coli and Staphylococcus aureus, respectively. In addition, the collagen could reduce the coatings' possible cytotoxicity. The results of this work can provide a highly effective and universal GO-based bioplatform for combination with inorganic antimicrobial NPs (i.e., AgNPs) with excellent photocatalytic properties, which can be utilized for facile and rapid in situ disinfection, as well as long-term prevention of bacterial infection through the synergistic bacteria killing of both 660-nm light-inspired photodynamic action and their innate physical antimicrobial ability.

A purely green synthesis of silver nanoparticles using Carica papaya, Manihot esculenta, and Morinda citrifolia: synthesis and antibacterial evaluations

Green procedure for synthesizing silver nanoparticles (AgNPs) is currently considered due to its economy and toxic-free effects. Several existing works on synthesizing AgNPs using leaves extract still involve the use of physical or mechanical treatment such as heating or stirring, which consume a lot of energy. To extend and explore the green extraction philosophy, we report here the synthesis and antibacterial evaluations of a purely green procedure to synthesize AgNPs using Carica papaya, Manihot esculenta, and Morinda citrifolia leaves extract without the aforementioned additional treatment. The produced AgNPs were characterized using the ultraviolet-visible spectroscopy, field emission scanning electron microscopy, energy-dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy, and antibacterial investigations. For antibacterial tests, two bacteria namely Escherichia coli and Bacillus cereus were selected. The presently employed method has successfully produced spherical AgNPs having sizes ranging from 9 to 69 nm, with plasmonic characteristics ranging from 356 to 485 nm, and energy-dispersive X-ray peak at approximately 3 keV. In addition, the smallest particles can be produced when Manihot esculenta leaves extract was applied. Moreover, this study also confirmed that both the leaves and synthesized AgNPs exhibit the antibacterial capability, depending on their concentration and the bacteria type.

An Efficient and Benign Antimicrobial Depot Based on Silver-Infused MoS2

Silver nanoparticles (AgNPs) have been used as a broad-spectrum antimicrobial agent, whose toxicity originates from the localized release of Ag⁺ ions. However, the residual AgNPs core could generate potential risk to humans and waste of noble metals. Herein, we infused the cysteine-modified molybdenum disulfide with minimum Ag⁺ ions and coated with a layer of cationic polyelectrolyte to construct an efficient and benign antimicrobial depot. The system exhibited much enhanced broad-spectrum antibacterial activity compared with an equivalent amount of silver nitrate, owing to its increasing accessibility of released Ag⁺ to the cell walls of microorganisms. More importantly, the antibacterial system could be successfully applied to treat wound infection, while retaining high antibacterial activities, exhibiting negligible biotoxicity and avoiding the waste of Ag.

Applications of white rot fungi in bioremediation with nanoparticles and biosynthesis of metallic nanoparticles

White rot fungi (WRF) are important environmental microorganisms that have been widely applied in many fields. To our knowledge, the application performance of WRF in bioremediation can be greatly improved by the combination with nanotechnology. And the preparation of metallic nanoparticles using WRF is an emerging biosynthesis approach. Understanding the interrelation of WRF and nanoparticles is important to further expand their applications. Thus, this mini-review summarizes the currently related reports mainly from the two different point of views. We highlight that nanoparticles as supports or synergistic agents can enhance the stability and bioremediation performance of WRF in wastewater treatment and the biosynthesis process and conditions of several important metallic nanoparticles by WRF. Furthermore, the potential toxicity of nanoparticles on WRF and challenges encountered are also discussed. Herein, we deem that this mini-review will strengthen the basic knowledge and provide valuable insight for the applications of WRF and nanoparticles.

Defeating Bacterial Resistance and Preventing Mammalian Cells Toxicity Through Rational Design of Antibiotic-Functionalized Nanoparticles

The rational synthesis of alternative materials is highly demanding due to the outbreak of infectious diseases and resistance to antibiotics. Herein, we report a tailored nanoantibiotic synthesis protocol where the antibiotic binding was optimized on the silver-silica core-shell nanoparticles surface to maximize biological responses. The obtained silver nanoparticles coated with mesoporous silica functionalized with ampicillin presented remarkable antimicrobial effects against susceptible and antibiotic-resistant Escherichia coli. In addition, these structures were not cell-death inducers and different steps of the mitotic cell cycle (prophase, anaphase and metaphase) were clearly identified. The superior biological results were attributed to a proper and tailored synthesis strategy.

Antimicrobial technology in orthopedic and spinal implants

Infections can hinder orthopedic implant function and retention. Current implant-based antimicrobial strategies largely utilize coating-based approaches in order to reduce biofilm formation and bacterial adhesion. Several emerging antimicrobial technologies that integrate a multidisciplinary combination of drug delivery systems, material science, immunology, and polymer chemistry are in development and early clinical use. This review outlines orthopedic implant antimicrobial technology, its current applications and supporting evidence, and clinically promising future directions.

Silver nanoparticles supported on carbon nanotube carpets: influence of surface functionalization

The effectiveness of nanoparticle-based functional devices depends strongly on the surface morphology and area of the support. An emerging powerful approach of increasing the available surface area without decreasing strength or increasing bulk is to attach arrays of suitable nanotubes on the surface, and to attach the necessary nanoparticles to them. Earlier publications by this team have shown that carpet-like arrays of carbon nanotubes (CNTs) can be successfully grown on a variety of larger carbon substrates such as graphite, foams and fabric, which offer hierarchical multiscale supporting architecture suitable for the attachment of silver nanoparticles (AgNPs). A limiting factor of pure CNT arrays in fluid-based applications is their hydrophobicity, which can reduce the percolation of an aqueous medium through individual nanotubes. Previous studies have demonstrated that the treatment of CNT carpets with dry (oxygen) plasma can induce reversible wettability, and treatment with wet (sol-gel) coating can impart permanent wettability. In this paper, we report the influence of such treatments on the attachment of AgNPs, and their effectiveness in water disinfection treatments. Both types of hydrophilic surface treatment show an increase in silver loading on the CNT carpets. Oxygen-plasma treated surfaces (O-CNT) show fine and densely packed AgNPs, whereas silica-coated nanotubes (silica-CNT) show uneven clusters of AgNPs. However, O-CNT surfaces lose their hydrophilicity during AgNP deposition, whereas silica-CNT surfaces remain hydrophilic. This difference significantly impacts the antibacterial effectiveness of these materials, as tested in simulated water containing Gram negative Escherichia coli (E. coli, JM109). AgNPs on silica-coated CNT substrates showed significantly higher reduction rates of E. coli compared to AgNPs on plasma-treated CNT substrates, despite the finer and better dispersed AgNP distribution in the latter. These results provide important insights into different aspects of surface modification approaches that can control the wettability of CNT carpets, and their applicability in water treatment applications.

Thermal co-reduction approach to vary size of silver nanoparticle: its microbial and cellular toxicology

In recent years, silver nanoparticles (AgNPs) have attracted considerable interest in the field of food, agriculture and pharmaceuticals mainly due to its antibacterial activity. AgNPs have also been reported to possess toxic behavior. The toxicological behavior of nanomaterials largely depends on its size and shape which ultimately depend on synthetic protocol. A systematic and detailed analysis for size variation of AgNP by thermal co-reduction approach and its efficacy toward microbial and cellular toxicological behavior is presented here. With the focus to explore the size-dependent toxicological variation, two different-sized NPs have been synthesized, i.e., 60 nm (Ag60) and 85 nm (Ag85). A detailed microbial toxicological evaluation has been performed by analyzing minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC), diameter of inhibition zone (DIZ), growth kinetics (GrK), and death kinetics (DeK). Comparative cytotoxicological behavior was analyzed by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. It has been concluded by this study that the size of AgNPs can be varied, by varying the concentration of reactants and temperature called as "thermal co-reduction" approach, which is one of the suitable approaches to meet the same. Also, the smaller AgNP has shown more microbial and cellular toxicity.

Stability of gum arabic-gold nanoparticles in physiological simulated pHs and their selective effect on cell lines

Stable gold nanoparticles coated with gum arabic (GA-AuNPs) exhibit selective effect on B16-F10 cells that could provide a future alternative for melanoma treatment.

Photochemically assisted one-pot synthesis of PMMA embedded silver nanoparticles: antibacterial efficacy and water treatment

Achievement of simultaneous reduction of bactericidal silver nanoparticles and in situ polymerization by photo irradiation is beneficial for water treatment.

Metal nanoparticle catalyzed charge rearrangement in selenourea probed by surface-enhanced Raman scattering

The adsorption behavior of selenourea (SeU) on Ag and Au nanoparticles was investigated using the surface-enhanced Raman scattering technique in combination with X-ray photoelectron spectroscopy and density functional theoretical calculations.

Optical paper-based sensor for ascorbic acid quantification using silver nanoparticles

In this paper, we demonstrate for the first time the use of silver nanoparticles (AgNPs) for colorimetric ascorbic acid (AA) quantification in a paper-based sensor. This device is constituted by spot tests modified with AgNPs and silver ions bordered by a hydrophobic barrier which provides quantitative and fast analysis of AA. In addition, this device is employed as point-of-care monitoring using a unique drop of the sample. AgNPs paper-based sensor changed from light yellow to gray color after the addition of AA due to nanoparticle growth and clusters formation. The color intensities were altered as a function of AA concentration which were measured by either a scanner or a homemade portable transmittance colorimeter. Under the selected measurement conditions, results presented limit of detection which was comparable to analytical laboratory-based methodologies. In addition, the sensitivity of our sensor was comparable to the standard titration method when real samples were investigated.

Preparation of different sized nano-silver loaded on functionalized graphene oxide with highly effective antibacterial properties

The synthesis of GO@PEG@AgNPs composites: step 1, synthesis of single-layer GO, step 2, the amidation reaction between carboxylic groups of GO and amine group of PEG to synthesize GO@PEG, step 3, GO@PEG in the presence the silver nitrate produces a GO@PEG@AgNPs composites.

Tailored silica-antibiotic nanoparticles: overcoming bacterial resistance with low cytotoxicity

New and more aggressive antibiotic resistant bacteria arise at an alarming rate and represent an ever-growing challenge to global health care systems. Consequently, the development of new antimicrobial agents is required to overcome the inefficiency of conventional antibiotics and bypass treatment limitations related to these pathologies. In this study, we present a synthesis protocol, which was able to entrap tetracycline antibiotic into silica nanospheres. Bactericidal efficacy of these structures was tested against bacteria that were susceptible and resistant to antibiotics. For nonresistant bacteria, our composite had bactericidal efficiency comparable to that of free-tetracycline. On the other hand, the synthesized composites were able to avoid bacterial growth of resistant bacteria while free-tetracycline has shown no significant bactericidal effect. Finally, we have investigated the cytotoxicity of these nanoparticles against mammalian cells to check any possible poisoning effect. It was found that these nanospheres are not apoptosis-inducers and only a reduction on the cell replication rate was seen when compared to the control without nanoparticles.

Partial aggregation of silver nanoparticles induced by capping and reducing agents competition

It is well known that nanomaterials properties and applications are dependent on the size, shape, and morphology of these structures. Among nanomaterials, silver nanoparticles (AgNPs) have attracted attention since they have considerably versatile properties, such as a variable surface area to volume ratio, which is very useful for many biomedical and technological applications. Within this scenario, small nanoparticle aggregates can have their properties reduced due to the increased size and alterations in their shape/morphology. In this work, silver nanoparticles aggregation was studied through chemical reduction of silver nitrate in the presence of sodium borohydride (reducing agent) and sodium citrate (capping agent). By changing the amount of reducing agent along the reaction, unaggregated and partially aggregated samples were obtained and characterized by UV-vis, zeta potential, and SAXS techniques. pH was measured in every step of the reaction in order to correlate these results with those obtained from structural techniques. Addition of the reducing agent first causes the reduction of Ag(+) to silver nanoparticles. For higher concentrations of sodium borohydrate, the average AgNPs size is increased and NPs aggregation is observed. It was found that zeta potential and pH values have a strong influence on AgNPs formation, since reducing agent addition can induce partial removal of citrate weakly associated on the AgNPs surface and increase the ionic strength of the solution, promoting partial aggregation of the particles. This aggregation state was duly identified by coupling SAXS, zeta potential and pH measurements. In addition, the SAXS technique showed that aggregates formed along the process are elongated-like particles due to the exponential decay evidenced through SAXS curves.

Electrospun chitosan nanofibers with controlled levels of silver nanoparticles. Preparation, characterization and antibacterial activity

The ideal wound dressing would have properties that allow for absorption of exudates, and inhibition of microorganism for wound protection. In this study, we utilized an electrospinning (ELSP) technique to design a novel wound dressing. Chitosan (CTS) nanofibers containing various ratios of silver nanoparticles (AgNPs) were obtained. AgNPs were generated directly in the CTS solution by using a chemical reduction method. The formation and presence of AgNPs in the CTS/AgNPs composite was confirmed by x-ray diffraction (XRD), ultraviolet-visible spectroscopy (UV) and thermogravimetric analysis (TGA). The electrospun CTS/AgNPs nanofibers were characterized morphologically by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). These nanofibers were subsequently tested to evaluate their antibacterial activity against gram-negative Pseudomonas aeruginosa (P. aeruginosa) and gram-positive Methicillin-resistant Staphylococcus aureus (MRSA). Results of this antibacterial testing suggest that CTS/AgNPs nanofibers may be effective in topical antibacterial treatment in wound care.