Immobilization Of AgNPs Research Articles

Antibacterial fibers impregnated with mycosynthetized AgNPs for control of Pectobacterium carotovorum

Using biopolymers functionalized with antibacterial agents to manufacture active packaging is a clean alternative to mitigate food losses due to postharvest plant diseases. In this study, two mycosynthetized AgNPs impregnation methodologies on cotton (cationization and in situ biochemical reduction) were used to obtain the antibacterial fibers (A-AgNPs-C and A-AgNPs-IBR), which, in addition to being characterized by SEM-EDX, XRD, were evaluated as antibacterial materials. The cotton fibers showed growth inhibition of Pectobacterium carotovorum at 48 h. The reuse tests of these cotton fibers showed that the two types of fibers could have up to three successive uses without losing their effectiveness, regardless of the impregnation method used. Is important to highlight that the retention tests indicated that the AgNPs remain attached to the A-AgNPs-C and A-AgNPs-IBR fibers after several successive washes. Finally, the mycosynthesized AgNPs were also impregnated on fique fibers (Fique-AgNPs) by cationization to obtain little antibacterial sacks. Nanostructured materials that in in vivo tests on potatoes showed only 7.8 % of affectation, while the tubers stored in the traditional sacks had an affectation of 25 %. This immobilization of AgNPs in natural fibers will allow the development of a nanobiotechnological application in the storage and transport of potatoes, after performing some additional cytotoxicity tests to guarantee its safety.

Investigation of Antimicrobial Effects of Polydopamine-Based Composite Coatings.

Herein, polydopamine (PDA)-based antimicrobial coatings loaded with silver nanoparticles (Ag NPs) and gentamicin were designed and prepared on glass slides using two different approaches. To our knowledge, this study was performed for the first time with the aim to compare these methods (viz., in situ loading and physical adsorption method) regarding the loading and release behavior of payloads. In one method, gentamicin was in situ loaded on PDA-coated substrates during PDA polymerization followed by Ag NPs immobilization (named as Ag@Gen/PDA); for the second method, Ag NPs and gentamicin were simultaneously loaded onto PDA via physical adsorption by immersing pre-formed PDA coatings into a mixed solution of Ag NPs and gentamicin (named as Ag/Gen@PDA). The loading and release characteristics of these antimicrobial coatings were compared, and both gave variable outcomes. The in situ loading method consequently provided a relatively slow release of loaded antimicrobials, i.e., approx. 46% for Ag@Gen/PDA as compared to 92% from physically adsorbed Ag/GenPDA in an immersion period of 30 days. A similar trend was observed for gentamicin release, i.e., ~0.006 µg/mL from Ag@Gen/PDA and 0.02 µg/mL from Ag/Gen@PDA each day. The slower antimicrobial release from Ag@Gen/PDA coatings would ultimately provide an effective long-term antimicrobial property as compared to Ag/Gen@PDA. Finally, the synergistic antimicrobial activities of these composite coatings were assessed against two microbial species, namely, Staphylococcus aureus and Escherichia coli, hence providing evidence in the prevention of bacterial colonization.

Photocatalytic degradation activity of goji berry extract synthesized silver-loaded mesoporous zinc oxide (Ag@ZnO) nanocomposites under simulated solar light irradiation

Different approaches have been developed for the synthesis of various nanostructured materials with unique morphologies. This study demonstrated the photocatalytic and antimicrobial abilities of silver-loaded zinc oxide nanocomposites (Ag@ZnO NCs). Initially, ZnO with a unique mesoporous ellipsoidal morphology in the size range of 0.59 ± 0.11 × 0.33 ± 0.09 µm (length × width) was synthesized using aqueous precipitation in a mild hydrothermal condition (80 °C) with the aqueous fruit extract of goji berry (GB) (as an additive) and calcined in air at 200 °C/2 h and 250 °C/3 h. Powder X-ray diffraction (XRD) revealed the formation of a hexagonal phase of the wurtzite (WZ) structure. The average crystallite size of ZnO was 23.74 ± 4.9 nm as calculated using Debye–Scherrer’s equation. It also possesses higher thermal stability with the surface area, pore volume, and pore size of 11.77 m2/g, 0.027 cm3/g, and 9.52 nm, respectively. Furthermore, different mesoporous Ag@ZnO NCs loaded with face-centered cubic (fcc) silver nanoparticles (Ag NPs) in the range of 90–160 nm were synthesized by GB extract as a reducing and capping agent on the surface of ZnO after calcination in air. The immobilization of Ag NPs was confirmed by XRD, X-ray photoelectron spectroscopy (XPS), field-emission scanning electron microscopy (FE-SEM), FE-transmission electron microscopy (FE-TEM), and energy-dispersive X-ray spectroscopy (EDS). It was found that Ag0.2@ZnO NC (0.2 wt% of Ag) showed excellent photocatalytic degradation of both methylene blue (MB) (cationic) and congo red (CR) (anionic) dyes under simulated solar irradiation. The photocatalytic degradation of 99.3 ± 0.35% MB and 98.5 ± 1.3% CR occurred in 90 and 55 min, respectively, at room temperature by Ag0.2@ZnO NC. Besides, these NCs also showed broad-spectrum antibacterial activity against both Gram-positive and Gram-negative bacteria. The mechanistic concept of generating reactive oxygen species (ROS) by electron and hole charge (e‾/h+) carriers seems to be responsible for the photocatalytic degradation of commercial dyes and antibacterial activities by Ag@ZnO NCs. Thus, these silver-loaded mesoporous ellipsoidal ZnO NCs are promising candidates as photocatalysts for industrial/wastewater treatment as well as in antimicrobial therapeutics.

Adsorption of Ag/Au nanoparticles by ordered macro-microporous ZIF-67, and their synergistic catalysis application

Silver nanoparticles (AgNPs) and gold nanoparticles (AuNPs) are universally used in diverse fields, but the use and treatment of various commodities will adversely affect the human health. Therefore, the recovery and immobilization of AgNPs and AuNPs from wastewater has important economic and social benefits. The ordered macro-microporous ZIF-67 single crystal (SOM-ZIF-67) was prepared by double solvent-assisted strategy. It was used as an adsorbent to remove precious metal pollutants, AuNPs and AgNPs. Under the optimal experimental conditions, the adsorption process of nanoparticles on SOM-ZIF-67 conformed to the pseudo-second-order kinetics. The theoretical maximum adsorption capacity of SOM-ZIF-67 towards AgNPs and AuNPs was 1250 mg g−1 and 2000 mg g−1, respectively. Through some characterization methods, it can be inferred that the adsorption mechanism might include ion-dipole interaction, metal-ligand interaction, and hydrogen bond, chelation and ion exchange between AgNPs/AuNPs and nitrogen and oxygen atom, and reduction etc. Furthermore, the interpenetrating macropores and micropores of SOM-ZIF-67 further promoting the adsorption capacity. Meanwhile, after the adsorption, the composite material (SOM-ZIF-67@AgNPs or SOM-ZIF-67@AuNPs) was developed as a new kind of heterogeneous catalyst that had good catalytic activity and cycle catalytic performance for 4-nitrophenol in the presence of NaBH4. At last, the adsorbent and catalyst could be regenerated. Simultaneously recycling of precious noble metal was also possible. Thus, the prepared SOM-ZIF-67 was a potential green adsorbent for the removal and recovery of precious metal nanoparticles. The secondary utilization as an effective catalyst would elaborate the sustainability of the method.

Exploring flowery MnO2/Ag nanocomposite as an efficient solar-light-driven photocatalyst

An efficient approach was developed to boost the solar light driven photocatalytic efficacy of pristine flowery MnO2 NCs through the immobilization of Ag NPs, which in turn produces MnO2/Ag NCs.

Concurrent Synthesis and Immobilization of Ag Nanoparticles over TiO2 via Plasma Reduction for Photocatalytic Treatment of Methyl Blue in Water.

Pure TiO2 nanoparticles (TiO2NPs) were produced via the sol–gel method and then coated with silver nanoparticles (AgNPs) to reduce their optical band gap. The concurrent synthesis and immobilization of AgNPs over TiO2NPs was achieved through the interaction of an open-air argon plasma jet with a solution of silver nitrate/stabilizer/TiO2NPs. The one-pot plasma synthesis and coating of AgNPs over TiO2NPs is a more straightforward and environmentally friendly method than others. The plasma-produced Ag/TiO2 nanocomposites were characterized and tested for their photocatalytic potential by degrading different concentrations of methyl blue (MB) in water. The dye concentration, oxidant dose, catalyst dose, and reaction time were also optimized for MB degradation. XRD results revealed the formation of pure AgNPs, pure TiO2NPs, and Ag/TiO2 nanocomposites with an average grain size of 12.36 nm, 18.09 nm, and 15.66 nm, respectively. The immobilization of AgNPs over TiO2NPs was also checked by producing SEM and TEM images. The band gap of AgNPs, TiO2NPs, and Ag/TiO2 nanoparticles was measured about 2.58 eV, 3.36 eV, and 2.86 eV, respectively. The ultraviolet (UV) results of the nanocomposites were supportive of the degradation of synthetic dyes in the visible light spectrum. The AgNPs in the composite not only lowered the band gap but also obstructed the electron–hole recombinations. The Ag/TiO2 composite catalyst showed 90.9% degradation efficiency with a 5 ppm dye concentration after 120 min of light exposure.

Modification of a SERS-active Ag surface to promote adsorption of charged analytes: effect of Cu2+ ions

This work studies the impact of the electrostatic interaction between analyte molecules and silver nanoparticles (Ag NPs) on the intensity of surface-enhanced Raman scattering (SERS). For this, we fabricated nanostructured plasmonic films by immobilization of Ag NPs on glass plates and functionalized them by a set of differently charged hydrophilic thiols (sodium 2-mercaptoethyl sulfonate, mercaptopropionic acid, 2-mercaptoethanol, 2-(dimethylamino)ethanethiol hydrochloride, and thiocholine) to vary the surface charge of the SERS substrate. We used two oppositely charged porphyrins, cationic copper(II) tetrakis(4-N-methylpyridyl) porphine (CuTMpyP4) and anionic copper(II) 5,10,15,20-tetrakis(4-sulfonatophenyl)porphine (CuTSPP4), with equal charge value and similar structure as model analytes to probe the SERS signal. Our results indicate that the SERS spectrum intensity strongly, up to complete signal disappearance, correlates with the surface charge of the substrate, which tends to be negative. Using the data obtained and our model SERS system, we analyzed the modification of the Ag surface by different reagents (lithium chloride, polyethylenimine, polyhexamethylene guanidine, and multicharged metal ions). Finally, all those surface modifications were tested using a negatively charged oligonucleotide labeled with Black Hole Quencher dye. Only the addition of copper ions into the analyte solution yielded a good SERS signal. Considering the strong interaction of copper ions with the oligonucleotide molecules, we suppose that inversion of the analyte charge played a key role in this case, instead of a change of charge of the substrate surface. Changing the charge of analytes could be a promising way to get clear SERS spectra of negatively charged molecules on Ag SERS-active supports.

Multiple effect of thermal treatment approach on PVDF membranes: Permeability enhancement and silver nanoparticles immobilization

Impregnation of the noble metal, silver nanoparticles (AgNPs) as a disinfectant into the polymeric membrane is one of the empirical modification methods in producing safe drinking water. However, the dispersion and immobilization of AgNPs during membrane fabrication and application is least discussed despite numerous leaching phenomena reported. In this study, silver nanoparticles type 1 (AgNPs-1) and type 2 (AgNPs-2) were prepared and incorporated into polyvinylidene fluoride (PVDF) ultrafiltration membrane with the presence of thermal treatment. The effect of thermal treatment was studied at temperature 25 °C, 40 °C and 55 °C which significantly influenced the physicochemical characteristics of the PVDF membrane. Membrane incorporated with AgNPs-1 and AgNPs-2 fabricated at highest temperature portrayed improved mechanical properties and pure water flux. PVDF/PVP/AgNPs-2 membrane released the smallest amount of Ag (3.81%) while PVDF/PVP/AgNPs-1 cast at 40 °C released the largest amount of Ag (42.34%) during the phase inversion at fabrication. Notably, no Ag leaching was found in all membranes during the dead-end filtration at 0.5 bar. Membranes with AgNPs-1 and AgNPs-2 showed remarkable bactericidal performance towards E. coli with a percentage reduction of 90.38% and 80.77%, respectively. Thus, membranes with AgNPs fabricated at 55 °C offered better mechanical properties of the enhanced permeability and excellent stability of AgNPs immobilization which signified the thermal treatment approach.

Green synthesis of highly dispersed Ag nanoparticles on polydopamine-functionalized graphene oxide and their high catalytic reduction reaction

Herein, we introduce a tailored mussel-inspired concept to facilitate the sustainable immobilization of silver nanoparticles (Ag NPs), which are accepted for the effectiveness in controlling the silver nanoparticle density and morphology onto the surface of the graphene oxide sheets (GO). Immobilization of Ag NPs on polydopamine (PDOP) functionalized GO is performed via the self-polymerization of dopamine by a facile in situ reduction method. The catalytic ability of the as-synthesized [email protected] catalyst was searched for the reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) as a class of widespread toxic organic pollutant. The dopamine-mediated graphene hybrid with Ag NPs exhibited excellent catalytic reduction activities due to promoting the electron transfer and the dispersion of small-sized silver nanoparticles imposed upon the surface of graphene. The resulting hybrid exhibited 15 times higher catalytic activity than that of the graphene/silver hybrid without any modification.

In situ synthesis of silver nanoparticles on modified poly(ethylene terephthalate) fibers by grafting for obtaining versatile antimicrobial materials

Because of having high mechanical properties and cheapness of PET textiles, functionalization of them for new properties is an active research area. In the present work, methacrylic acid (MAA)-grafted PET fibers (PET-g-MAA) were obtained by grafting of MAA monomers to PET surface for an antimicrobial material synthesis. The morphologies of the obtained graft copolymers were examined with a scanning electron microscopy (SEM), and the chemical modification after grafting was determined with Fourier-transform infrared spectroscopy (FTIR) analysis. Subsequently, silver ions were adsorbed onto the PET-g-MAA fibers surface and the adsorbed ions to the surface were reduced to silver nanoparticles (AgNPs) by UVC light. The morphology of fiber surfaces modified with MAA and coated with AgNPs was examined by SEM studies, and it was observed that AgNPs were disturbed along the fibers. The presence of silver on the surface was also confirmed by energy-dispersive X-ray spectroscopy (EDS) and energy dispersion X-ray fluorescence spectrometry (EDXRF). The crystalline structure of the original PET fiber, PET-g-MAA fiber and PET-g-MAA fiber modified with AgNPs was investigated by X-ray diffraction (XRD). The thermal properties of the obtained fibers were investigated by thermogravimetric analysis (TGA). The immobilization of AgNPs on the grafted fibers leads to a change on the patterns of TGA curves. The most significant change is the less weight reduction in the temperature range of 200–300°C. Disk diffusion test was performed using Staphylococcus aureus (ATCC 6538) and Escherichia coli (ATCC 25,922) bacteria in order to investigate the antibacterial ability of the obtained fibers, and it was found that the fibers coated with AgNPs had antibacterial effect on both bacterial species. The cytotoxicity of the groups with the best antibacterial properties was determined by MTT test, and the synthesized material did not have cytotoxic effects on L929 fibroblast cells. The material obtained has the potential to be used in antimicrobial applications.

Green synthesis and immobilization of AgNPs by lumpy corn stalk as interlayer filling material for durable antibacterial

Lumpy corn stalk is conventionally used as interlayer filling material in plywood, while high temperature and humidity in tropical and subtropical areas are easy to cause bacteria growth on plywood. Silver nanoparticles (AgNPs) are one of efficient antibacterial metal nanoparticles due to their excellent broad-spectrum antibacterial properties. But most of these AgNPs are normally in solution and easy to aggregate, which limits their utilization. Besides, the synthesis of AgNPs always needs chemical reducing agents, which can cause environmental and cost problems. In this study, lumpy corn stalk with honeycomb-like structure acted as green reducing agent and stabilizer to in situ synthesize AgNPs, the obtained antibacterial lumpy corn stalk (CS@AgNPs) could be used as interlayer filling material to protect plywood from bacteria erosion. Durable antibacterial study showed that the bacteriostatic properties of lumpy CS@AgNPs against E. coli and S. aureus were stronger and more durable than commercial Ag+ spray and hydrogel. The antibacterial mechanism may be that the controlled-released AgNPs destroyed the morphological structure of bacteria by penetrating into the bacterial cell membrane, following by leaking cellular content. Notably, the final release amount of AgNPs from lumpy CS@AgNPs after 12 days in buffer solution was only 0.011 mg/L, which was 9 times lower than the domestic drinking water limit presented by United States Environmental Protection Agency (USEPA). The plywood with lump CS@AgNPs as interlayer filling material could keep efficient and durable bacteria killing activity in 21 days, which could be used safely in food packaging, furniture and flooring fields.

Surface modification of SiO2 nanoparticles with PDMAEMA brushes and Ag nanoparticles as antifungal coatings using electron beam assisted synthesis

A model functional, stable and dispersible silver nanoparticles (AgNPs) immobilized on polymeric brushes grafted silica nanoparticle is proposed as antimicrobial additive for coating applications. The aim of this work is to modify silica nanoparticles (SiO2NPs) with poly 2-(dimethyl amino) ethyl methacrylate (PDMAEMA) brushes for template synthesis and immobilization of AgNPs using electron beam assisted grafting and reduction reactions. The PDMAEMA moieties were grafted onto vinyltrimethoxysilane (VTMS) modified SiO2NPs using pre-irradiation and peroxidation grafting approaches. Several grafting parameters, i.e., pre-irradiation doses, DMAEMA monomer concentrations, reaction times and temperatures, were studied to optimize degree of grafting (DG). AgNPs were constructed on the SiO2NPs through the grafted PDMAEMA brushes as polymer shell template. AgNPs were successfully created on SiO2NPs-VTMS-PDMAEMA by electron-induced reduction reaction. DG of the PDMAEMA on SiO2NPs-VTMS was confirmed by gravimetric measurement, FTIR, TGA, TEM, FE-SEM. The nanostructure information and AgNPs immobilization were revealed by UV–Vis, TEM, SEM-EDX and XRD. The optimized grafting degree to obtain desirable appearance was 190%. The AgNPs (6 ± 2 nm) on SiO2NPs-VTMS-PDMAEMA exhibited the characteristic UV-vis absorbance of spherical Ag nanoarchitecture around 418 nm. The AgNPs immobilized SiO2NPs-VTMS-PDMAEMA efficiently inhibited the growth of fungi, i.e., Aspergillus niger and Syncephalatrum racemosum found on building materials.

Laser Functionalization of Carbon Membranes for Effective Immobilization of Antimicrobial Silver Nanoparticles

Abstract Microbial contamination and biofilm formation are serious challenges in water filtration applications. Recently, carbon nanocomposite membranes with modified silver nanoparticles (AgNPs) have attracted much attention as compelling water purification membranes that can deactivate pathogenic bacteria and prevent biofilm formation. However, the effective attachment of AgNPs onto such carbon-based surfaces has proven difficult to accomplish via inexpensive and rapid fabrication processes. In this study, we introduce a simple laser-assisted process that enables rapid surface functionalization and immobilization of AgNPs onto carbon cloth membrane surfaces comprised of woven carbon micro fibers. The laser functionalization provides a unique modification in surface morphology of the fibers by creating nanotextures as well as inducing changes in surface chemistry, all of which increase the physical and chemical bonding of AgNPs onto the surface of carbon fibers. Elemental and surface morphology analysis via XRD, SEM, and EDX reveal a uniform coating and strong attachment of AgNPs onto the laser functionalized carbon surface, even after vigorous mechanical agitations and probe sonication. The analysis showed the samples prepared by the laser functionalization prior to AgNPs coating provided exceptional antibacterial activity and ability to completely eradicate the bacteria within 4 h and resist biofilm formation against pathogenic bacterial strains of Escherichia coli. The developed technology provides new opportunities to develop a scalable, fast, and cost-effective preparation method for producing carbon-based materials/membranes with high antimicrobial activities which can be applied for water purification and other environmental applications.

Facile fabrication of functional cellulose paper with high-capacity immobilization of Ag nanoparticles for catalytic applications for tannery wastewater

It has been a research goal to develop macroscopic materials with an optimized surface structure to affix silver nanoparticles which could contaminate water and maximize their practical functions. Cellulose paper is a versatile biomass material valued for its abundance, low cost, biocompatibility, and natural composition. Until now, its potential application in water purification has not been adequately explored. In this study, gallic acid-modified silver nanoparticles (GA@AgNPs) were loaded onto commercial cellulose filter paper using a simple lipoic acid modification process (GA@AgNPs-LA-CP). Scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD) were used to characterize the GA@AgNPs-LA-CP. The catalytic activity of the GA@AgNPs-LA-CP was evaluated by the reduction reaction of methylene blue (MB), Rhodamine B (RhB), and 4-nitrophenol (4-NP) with sodium borohydride (NaBH4). The GA@AgNPs-LA-CP exhibited excellent catalytic activity toward MB, RhB, and 4-NP, taking advantage of its high specific surface area generated by the cellulose fiber network structure. Interestingly, due to the electrostatic interactions between the cationic dyes and the GA@AgNPs, the as-prepared catalytic composite material serves as a better catalyst for MB and RhB, suggesting dual applications of the composite materials for organic wastewater treatment and the removal of harmful dyes. This implies that the immobilization of AgNPs on cellulose papers is an effective method and can be applied to efficient wastewater treatment applications.Graphical abstract

Affordable and environmentally friendly method for the synthesis of a green silver nanophotocatalyst based on Mespilus germanica

Leaves of Mespilus germanica have been utilized as a green and inexpensive reducing and stabilizing agent to synthesize silver nanoparticles without using any capping agent or harsh and toxic solvents. In this protocol a silver nanophotocatalyst was synthesized by a green method via immobilization of Ag NPs on the surface of Mespilus germanica seed as a green photocatalyst. The biosynthesized nanophotocatalyst was characterized by ultraviolet–visible, Fourier-transform infrared, X-ray diffraction, field emission scanning electron microscopy, energy dispersive X-ray spectroscopy, and transmission electron microscopy. The photocatalytic activity of the synthesized silver nanocatalyst was investigated by using it for the degradation of methylene blue under sunlight. The results showed good photocatalytic activity without any agglomeration. In addition, the silver nanophotocatalyst can be recycled and reused several times in the same reaction without significant loss of activity.

On demand release of ionic silver from gold-silver alloy nanoparticles: fundamental antibacterial mechanisms study

Synthesis and biomedical research of bimetallic gold-silver nanoparticles (Au–Ag NPs) have gained much attention due to their unique properties. Antibacterial mechanism of gold-silver nanoparticles is a current topic of interest in nanomedicine engineering. We used three routes in the synthesis of Au–Ag NPs alloy: i) Co-reduction of [HOOC-4-C6H4NN]AuCl4/AgNO3, ii) Seeding of AuNPs-COOH/AgNO3 and iii) immobilization of AgNPs over the parent AuNPs-COOH. Two mild reducing agents, NaBH4 and 9-BBN (9-borabicyclo(3.3.1)nonane), were used. Colloidal alloy nanoparticles structure was confirmed using transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). The particles reduced using NaBH4 were larger (~20 nm) than those synthesized using 9-BBN (<10 nm). The synthesized nanoparticles showed high stability under notoriously leaching conditions of chloride-containing electrolytes. Moreover, we studied the Au–Ag NPs antibacterial activity against the growth of Gram-negative Escherichia coli ATCC strain 25922 and Gram-positive Staphylococcus aureus ATCC strain 29213. The antibacterial mechanisms were evaluated by studying the time-dependent generation of reactive oxygen species (ROS). A major destruction of the bacterial cell wall and leakage of cell components were observed by scanning electron microscopy (SEM), which is clearly visible towards E. coli more than S. aureus bacterial strain. The destruction of the bacterial cell wall was further confirmed by detecting the DNA leakage using gel electrophoresis. The synergistic effect of gold enhanced the antibacterial properties, however, with low cytotoxicity to human dermal fibroblast cells. This study deals with the important aspects of time-dependent mechanisms of the antibacterial action of Au–Ag NPs since the leaching out of Ag ion is slow compared to AgNPs. The Au–Ag NPs alloy efficiently tackles microbial activity that can be controlled to minimize cytotoxicity and thus opens their future applications as antibacterial agents.

Ultrafine Silver Nanoparticles Embedded in Cyclodextrin Metal-Organic Frameworks with GRGDS Functionalization to Promote Antibacterial and Wound Healing Application.

The challenge of bacterial infection increases the risk of mortality and morbidity in acute and chronic wound healing. Silver nanoparticles (Ag NPs) are a promising new version of conventional antibacterial nanosystem to fight against the bacterial resistance in concern of the drug discovery void. However, there are several challenges in controlling the size and colloidal stability of Ag NPs, which readily aggregate or coalesce in both solid and aqueous state. In this study, a template-guided synthesis of ultrafine Ag NPs of around 2 nm using water-soluble and biocompatible γ-cyclodextrin metal-organic frameworks (CD-MOFs) is reported. The CD-MOF based synthetic strategy integrates AgNO3 reduction and Ag NPs immobilization in one pot achieving dual functions of reduced particle size and enhanced stability. Meanwhile, the synthesized Ag NPs are easily dispersible in aqueous media and exhibit effective bacterial inhibition. The surface modification of cross-linked CD-MOF particles with GRGDS peptide boosts the hemostatic effect that further enhances wound healing in synergy with the antibacterial effect. Hence, the strategy of ultrafine Ag NPs synthesis and immobilization in CD-MOFs together with GRGDS modification holds promising potential for the rational design of effective wound healing devices.

Cancer cell targeting and therapeutic delivery of silver nanoparticles by mesoporous silica nanocarriers: insights into the action mechanisms using quantitative proteomics.

An approach for safely delivering AgNPs to cancer cells and the evaluation of the affected cellular mechanism are presented. The use of mesoporous silica nanoparticles (MSNs) as nanovehicles decorated with transferrin (Tf, targeting agent) provides a nanoplatform for the nucleation and immobilization of AgNPs (MSNs-Tf-AgNPs). We performed the physico-chemical characterization of the nanosystems and evaluated their therapeutic potential using bioanalytical strategies to estimate the efficiency of the targeting, the degree of cellular internalization in two cell lines with different TfR expression, and the cytotoxic effects of the delivered AgNPs. In addition, cellular localization of the nanosystems in cells has been evaluated by a transmission electron microscopy analysis of ultrathin sections of human hepatocarcinoma (HepG2) cells exposed to MSNs-Tf-AgNPs. The in vitro assays demonstrate that only the nanosystem functionalized with Tf is able to transport the AgNPs inside the cells which overexpress transferrin receptors. Therefore, this novel nanosystem is able to deliver AgNPs specifically to cancer cells overexpressing Tf receptors and offers the possibility of a targeted therapy using reduced doses of silver nanoparticles as cytotoxic agents. Then, a quantitative proteomic experiment validated through the analysis of gene expression has been performed to identify the molecular mechanisms of action associated with the chemotherapeutic potential of the MSNs-Tf-AgNP nanocarriers.

Encapsulation of AgNPs within Zwitterionic Hydrogels for Highly Efficient and Antifouling Catalysis in Biological Environments.

Silver nanoparticles (AgNPs) have been widely used as catalysts in a variety of chemical reactions owing to their unique surface and electronic properties, but their practical applications have been hindered by severe aggregation. The immobilization of AgNPs is crucial to preventing their aggregation or precipitation as well as to improving their reusability. Herein, we developed a facile route for the reductant-free in situ synthesis of AgNPs in zwitterionic hydrogels. Via this method, the embedded AgNPs had a uniform distribution, high activity, and antibiofouling capability. The catalytic reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) using polycarboxybetaine-AgNPs (PCB-AgNPs) could achieve >95% conversion efficiency within 5 min. Meanwhile, the normalized rate constant knor (10.617 s-1mmol-1) was higher than that of most of the reported immobilized nanocatalysts. More importantly, in a biofouling environment, PCB-AgNPs could still exhibit >97% initial catalytic activity while AgNPs in the PSB or PHEMA hydrogel lost ∼60% activity. This strategy holds great potential for the immobilization of nanoparticle catalysts, especially for applications in biological environments.

Facile and efficient in situ synthesis of silver nanoparticles on diverse filtration membrane surfaces for antimicrobial performance

Membrane biofouling remains a major limiting factor for the membrane-based water purification technology. The development of antibacterial membrane surfaces is very important for membrane biofouling mitigation. In this study, we developed a one-pot method of synthesizing silver nanoparticles (Ag NPs) and immobilizing them onto membranes via simply soaking the membranes in a mixture solution of silver nitrate, poly (ethylene glycol) methyl ether thiol (mPEG-SH) and dopamine. Results illustrate that mPEG-SH works as a ligand to slow down the reduction process of silver ions by dopamine for the synthesis of Ag NPs in a controllable manner and also the prevention of Ag NPs aggregation in solution. Moreover, the Ag NPs could be in situ immobilized onto polysulfone ultrafiltration membrane, glass fiber membrane and stainless steel, regardless of their surface properties, but the size of Ag NPs was affected by the substrates. In addition, the Ag NPs immobilization on the polysulfone ultrafiltration membranes increased the bovine serum albumin rejection rate of membrane by 16%, but decreased membrane permeability by 14% compared to that of the pristine membranes. The Ag NPs containing membranes exhibited outstanding antibacterial properties with more than 90% antibacterial efficiency against both Gram-negative bacteria Escherichia coli and Gram-positive bacteria Staphylococcus aureus. During the filtration test, the silver release from the Ag NPs containing polysulfone ultrafiltration membranes was very slow and the total accumulation of silver ions released from the membranes was only 7% of its initial Ag NPs loading after 24 h filtration operation. The silver ion concentration in the permeate water was 0.35 ± 0.16 ppb, far below the maximal contaminant limit of silver ions in drinking water with no risk for the application of Ag NPs incorporated membranes to treat water. Our work provides a facile and universal approach of synthetizing and simultaneously immobilizing Ag NPs onto diverse membranes for antibacterial properties.