Commercial AgNPs Research Articles

Performance of modified hollow fiber membrane silver nanoparticles-zeolites Na–Y/PVDF composite used in membrane bioreactor for industrial wastewater treatment

Membrane bioreactor (MBR) deteriorates due to fouling on the membrane pores, which can reduce the membrane performance. To reduce membrane fouling, the addition of inorganic filler can enhance the antifouling properties. This study investigates two different membrane preparation by thermally induced phase separation (TIPS) and dip coating methods to modify hollow fiber membrane with Silver Nanoparticles (AgNPs)-Zeolites used in MBR for industrial wastewater treatment. Performance was evaluated by analyzing the flux of water and wastewater, rejection, water content, and antifouling properties. Characterization result represented the synthesized silver nanoparticles had similar diffraction peak with commercial AgNPs, then the micrograph of AgNPs and zeolites addition membrane showed that the inorganic material had an octahedral shape representing zeolite crystal and irregular shape representing AgNPs. The addition of zeolites and AgNPs resulted in satisfying performance, increased flux, rejection, and antifouling properties.

Ångstrom-scale silver particles ameliorate collagen-induced and K/BxN-transfer arthritis in mice via the suppression of inflammation and osteoclastogenesis.

Nanoparticles (NPs) hold a great promise in combating rheumatoid arthritis, but are often compromised by their toxicities because the currently used NPs are usually synthesized by chemical methods. Our group has previously fabricated Ångstrom-scale silver particles (AgÅPs) and demonstrated the anti-tumor and anti-sepsis efficacy of fructose-coated AgÅPs (F-AgÅPs). This study aimed to uncover the efficacy and mechanisms of F-AgÅPs for arthritis therapy. We evaluated the efficacy of F-AgÅPs in collagen-induced arthritis (CIA) mice. We also compared the capacities of F-AgÅPs, the commercial AgNPs, and the clinical drug methotrexate (MTX) in protecting against K/BxN serum-transfer arthritis (STA) mice. Moreover, we evaluated the effects of F-AgÅPs and AgNPs on inflammation, osteoclast formation, synoviocytes migration, and matrix metalloproteinases (MMPs) production in vitro and in vivo. Meanwhile, the toxicities of F-AgÅPs and AgNPs in vitro and in vivo were also tested. F-AgÅPs significantly prevented bone erosion, synovitis, and cartilage damage, attenuated rheumatic pain, and improved the impaired motor function in mouse models of CIA or STA, the anti-rheumatic effects of which were comparable or stronger than AgNPs and MTX. Further studies revealed that F-AgÅPs exhibited similar or greater inhibitory abilities than AgNPs to suppress inflammation, osteoclast formation, synoviocytes migration, and MMPs production. No obvious toxicities were observed in vitro and in vivo after F-AgÅPs treatment. F-AgÅPs can effectively alleviate arthritis without notable toxicities and their anti-arthritic effects are associated with the inhibition of inflammation, osteoclastogenesis, synoviocytes migration, and MMPs production. Our study suggests the prospect of F-AgÅPs as an efficient and low-toxicity agent for arthritis therapy.

Synthesized silver nanoparticles decorated reduced graphene oxide/silver ink for aerosol jet printed conformal temperature sensor with a wide sensing range and excellent stability

Three-dimensional (3D) conformal printing of temperature sensors with a wide sensing range and high stability requires the potential printable material with excellent functionality and printability. Herein, a high-performance silver nanoparticles (Ag NPs) decorated reduced graphene oxide (RGO)/Ag (ADR/Ag) ink with low viscosity was synthesized for aerosol jet printing (AJP). Ag ions are electrostatically adsorbed on the graphene oxide (GO) surface, and Ag NPs (∼10 nm) were attached onto the RGO surface by in-situ liquid-phase reduction. The ADR nanoflakes were mixed with commercial Ag NPs ink, high resolution patterns with ink stream widths down to 10 μm are printed, and ADR/Ag-0.8% ink shows excellent low-temperature sintering capability and flexibility, and the resistivity of the printed traces is 9.79 × 10−5 Ω m after 1 h sintering at a relatively low temperature (75 °C). The resistance negligibly increases by only 5% after 1000 bending cycles, which is about 7 times lower compared to the pure Ag traces. Furthermore, we achieve the 3D printing of a conformal temperature sensor with a sensitivity range of (1.162–1.519) × 10−3/°C in the broad sensing range of 0–200 °C. These findings shed light on the additive manufacturing of high-performance conformal electronics using the emerging AJP technology.

Eco-Friendly Green Synthesis of Rubropunctatin Functionalized Silver Nanoparticles and Evaluation of Antibacterial Activity.

In order to solve the problems of rubropunctatin insoluble in water and its low bioavailability, and explore the synthesis method of green silver nanoparticles, rubropunctatin was used as reducing agent and blocking agent, rubropunctatin-functionalized silver nanoparticles (R-AgNPs) were successfully synthesized. The distinctive absorption peak at 410 nm confirmed the formation of R-AgNPs. Zeta potential measurement showed excellent stability of R-AgNPs with negative values of -29.81 ± 0.37 mV. The results of TEM and XRD showed that the prepared R-AgNPs were round, well dispersed and crystallized with average particle size of 13.54 ± 0.42 nm. FT-IR and XPS studies show that functional groups are involved in R-AgNPs synthesis. The antibacterial activity of R-AgNPs was compared with commercial silver nanoparticles (AgNPs) by microdilution method. The results showed that R-AgNPs (MIC 7.81 μg/mL) has stronger antibacterial activity than commercial AgNPs. The bacteria morphology was observed by the live and dead (SYTO 9/PI) staining assay and SEM showed that the antibacterial effect of R-AgNPs was caused by the destruction of the bacterial cell membrane. Cytotoxicity of rubropunctatin-functionalized silver nanoparticles and commercial silver nanoparticles on mouse fibroblast 3T3 cells was assessed by CCK-8 assay. The results showed that the toxicity of rubropunctatin-functionalized silver nanoparticles to 3T3 cells was lower than that of commercial silver nanoparticles. In summary, synthesis of silver nanoparticles using rubropunctatin is a green synthesis method, and R-AgNPs is a potential antibacterial agent.

Biogenic Silver Nanoparticles Processed Twice Using 8M Urea Exhibit Superior Antibacterial and Antifungal Activity to Commercial Chemically Synthesized Counterparts

Biogenic silver nanoparticles (b-AgNPs) were produced extracellularly using a cell lysate of genetically modified Escherichia coli and subdivided into three groups. Each group received a different treatment to determine which one best removed residual cell lysate material. The first group was treated twice using only water (water ×2), the second using 8M urea once (8M urea ×1), and the third using 8M urea twice (8M urea ×2). Subsequently, each group was assessed for its ability to inhibit the growth of six bacterial and two fungal pathogens. Testing was accomplished using the minimum inhibitory concentration (MIC) method. Commercially produced c-AgNPs were included for comparison. In all cases, the b-AgNPs (8M urea ×2) demonstrated the greatest inhibition of microbe growth. Conversely, the commercial AgNPs failed to show any growth inhibition at 10 µg/mL the highest concentration tested. The greater antibacterial activity of the b-AgNPs (8M urea ×2) over both b-AgNPs (8M urea ×1) and b-AgNPs (water ×2) is thought to be due to a larger degree of biofunctionalization (coating) occurring during the two sequential 8M urea treatments.

Streptomyces chiangmaiensis SSUT88A mediated green synthesis of silver nanoparticles: characterization and evaluation of antibacterial action against clinical drug-resistant strains.

This study involved the characterization of AgNPs synthesized from soil isolate Streptomyces sp. SSUT88A and their antimicrobial activities. The strain SSUT88A revealed 98.8% similarity of the 16s rRNA gene to Streptomyces chiangmaiensis TA4-1T. The AgNPs were synthesized by mixing either intracellular or extracellular cell-free supernatant of strain SSUT88A with AgNO3. The synthesized AgNPs from intracellular cell-free supernatant and extracellular cell-free supernatant were designated as IS-AgNPs and ES-AgNPs, respectively. The IS-AgNPs showed maximum absorbance of UV-vis spectra at 418 nm, while ES-AgNPs revealed maximum absorbance at 422 nm. The TEM observation of synthesized AgNPs revealed a spherical shape with an average diameter of 13.57 nm for IS-AgNPs and 30.47 nm for ES-AgNPs. The XRD and XANES spectrum profile of both synthesized AgNPs exhibited similar spectrum energy, which corresponded to AgNPs. The IS-AgNPs revealed antimicrobial activity against clinical isolate drug-resistant bacteria (Acinetobacter baumannii, Escherichia coli 8465, Klebsiella pneumoniae 1617, and Pseudomonas aeruginosa N90PS), while ES-AgNPs had no antimicrobial activity. When compared to commercial AgNPs, IS-AgNPs exhibited antibacterial efficacy against all clinical isolate bacteria including A. baumannii, one of the most threatening multi-drug resistant strains, while commercial AgNPs did not. Thus, IS-AgNPs has potential to be further developed as an antimicrobial agent against drug-resistant bacteria.

A chitosan-based multifunctional hydrogel containing in situ rapidly bioreduced silver nanoparticles for accelerating infected wound healing.

Generally, bacterial infection seriously hinders the wound healing process, so it is crucial to safeguard the wound from severe infection. Besides, multifunctional hydrogel dressings (self-healing, injectable, antibacterial and adaptable) seem to be conducive to meet the needs of wound healing. Here, a double-crosslinked multifunctional hydrogel (COC hydrogel) based on quaternized chitosan, methacrylate anhydride-modified collagen and oxidized dextran was developed. The double-crosslinked network improved the stability of the hydrogel while not destroying the functionality of the Schiff base bond. More importantly, silver ions were rapidly in situ bioreduced to silver nanoparticles (AgNPs) during the formation of the COC hydrogel, which can essentially avoid the dispersion and agglomeration problems. The obtained COC@AgNP hydrogel had good biocompatibility compared with that loaded with silver ions and excellent antibacterial properties compared with that loaded with the same amount of commercial AgNPs. In vivo results indicated that the COC@AgNP hydrogel accelerated the healing process of infected full-thickness skin defects through anti-infection, anti-inflammation, stimulating collagen deposition, and promoting the formation of epithelia and blood vessels. Collectively, the COC@AgNP hydrogel has good potential for clinical infected wound dressing applications.

Green Synthesis of Silver-Peptide Nanoparticles Generated by the Photoionization Process for Anti-Biofilm Application.

An alarming increase in antibiotic-resistant bacterial strains is driving clinical demand for new antibacterial agents. One of the oldest antimicrobial agents is elementary silver (Ag), which has been used for thousands of years. Even today, elementary Ag is used for medical purposes such as treating burns, wounds, and microbial infections. In consideration of the effectiveness of elementary Ag, the present researchers generated effective antibacterial/antibiofilm agents by combining elementary Ag with biocompatible ultrashort peptide compounds. The innovative antibacterial agents comprised a hybrid peptide bound to Ag nanoparticles (IVFK/Ag NPs). These were generated by photoionizing a biocompatible ultrashort peptide, thus reducing Ag ions to form Ag NPs with a diameter of 6 nm. The IVFK/Ag NPs demonstrated promising antibacterial/antibiofilm activity against reference Gram-positive and Gram-negative bacteria compared with commercial Ag NPs. Through morphological changes in Escherichia coli and Staphylococcus aureus, we proposed that the mechanism of action for IVFK/Ag NPs derives from their ability to disrupt bacterial membranes. In terms of safety, the IVFK/Ag NPs demonstrated biocompatibility in the presence of human dermal fibroblast cells, and concentrations within the minimal inhibitory concentration had no significant effect on cell viability. These results demonstrated that hybrid peptide/Ag NPs hold promise as a biocompatible material with strong antibacterial/antibiofilm properties, allowing them to be applied across a wide range of applications in tissue engineering and regenerative medicine.

Impact of polyvinylpyrrolidone and quantity of silver nitrate on silver nanoparticles sizing via solvothermal method for dye‐sensitized solar cells

The multiple sizing of silver nanoparticles (AgNPs) were synthesized from the miscible compound of ethylene glycol (EG), polyvinylpyrrolidone (PVP) and silver nitrate (AgNO3) via the solvothermal method. During the synthesis, the PVP‐AgNO3 was contemplated as a paramount parameter. Using the simple method of solvothermal, the sizing of AgNPs was easily controlled in accord with the augmentation of PVP‐AgNO3 at secured and moderate temperature. In regards to the sizing of AgNPs, the presence of minimum agglomeration, the absorption capability and chemical structures were highlighted through a series of verification includes ultraviolet–visible (UV–Vis) spectroscopy, Fourier‐transform infrared (FTIR) spectroscopy and transmission electron microscopy (TEM) analysis. The effectiveness of the synthesized AgNPs was further investigated and compared with the commercial AgNPs by incorporating the AgNPs into titanium dioxide (TiO2) semiconductor film‐based dye‐sensitized solar cells (DSSCs). Results signified that the spherical AgNPs with produced sizing within the range of 19.6 to 45.2 nm were greatly impacting by tunable quantities of PVP‐AgNO3, which was validated in the forms of linear equations. A larger size promotes a slower nucleation rate that conduces agglomeration. In opposition to this, the smallest size of AgNPs develops a faster formation rate of Ag ions into AgNPs, inducing the deterrent of agglomeration in light of notable particle dispersion. The power conversion efficiency (PCE) contributed by the incorporation of synthesized AgNPs into TiO2 is also 41.2% higher than that of the commercial AgNPs‐TiO2. This is because the synthesized AgNPs provides less agglomeration which led to a better surface plasmonic effect towards the nanoparticles.

Insight into the Antibacterial Activity of Selected Metal Nanoparticles and Alterations within the Antioxidant Defence System in Escherichia coli, Bacillus cereus and Staphylococcus epidermidis.

The antimicrobial activity of nanoparticles (NPs) is a desirable feature of various products but can become problematic when NPs are released into different ecosystems, potentially endangering living microorganisms. Although there is an abundance of advanced studies on the toxicity and biological activity of NPs on microorganisms, the information regarding their detailed interactions with microbial cells and the induction of oxidative stress remains incomplete. Therefore, this work aimed to develop accurate oxidation stress profiles of Escherichia coli, Bacillus cereus and Staphylococcus epidermidis strains treated with commercial Ag-NPs, Cu-NPs, ZnO-NPs and TiO2-NPs. The methodology used included the following determinations: toxicological parameters, reactive oxygen species (ROS), antioxidant enzymes and dehydrogenases, reduced glutathione, oxidatively modified proteins and lipid peroxidation. The toxicological studies revealed that E. coli was most sensitive to NPs than B. cereus and S. epidermidis. Moreover, NPs induced the generation of specific ROS in bacterial cells, causing an increase in their concentration, which further resulted in alterations in the activity of the antioxidant defence system and protein oxidation. Significant changes in dehydrogenases activity and elevated lipid peroxidation indicated a negative effect of NPs on bacterial outer layers and respiratory activity. In general, NPs were characterised by very specific nano-bio effects, depending on their physicochemical properties and the species of microorganism.

Detection of Silver Nanoparticles in Seawater Using Surface-Enhanced Raman Scattering.

Nanomaterials significantly contribute to the development of new solutions to improve consumer products properties. Silver nanoparticles (AgNPs) are one of the most used, and as human exposure to such NPs increases, there is a growing need for analytical methods to identify and quantify nanoparticles present in the environment. Here we designed a detection strategy for AgNPs in seawater using surface-enhanced Raman Scattering (SERS). Three commercial AgNPs coated with polyvinylpyrrolidone (PVP) were used to determine the relative impact of size (PVP-15nmAgNPs and PVP-100nmAgNPs) and aggregation degree (predefined Ag aggregates, PVP-50–80nmAgNPs) on the SERS-based detection method. The study of colloidal stability and dissolution of selected AgNPs into seawater was carried out by dynamic light scattering and UV-vis spectroscopy. We showed that PVP-15nmAgNPs and PVP-100nmAgNPs remained colloidally stable, while PVP-50–80nmAgNPs formed bigger aggregates. We demonstrated that the SERS-based method developed here have the capacity to detect and quantify single and aggregates of AgNPs in seawater. The size had almost no effect on the detection limit (2.15 ± 1.22 mg/L for PVP-15nmAgNPs vs. 1.51 ± 0.71 mg/L for PVP-100nmAgNPs), while aggregation caused an increase of 2.9-fold (6.08 ± 1.21 mg/L). Our results demonstrate the importance of understanding NPs transformation in seawater since this can influence the detection method performance.

Productivity performance of peach trees, insecticidal and antibacterial bioactivities of leaf extracts as affected by nanofertilizers foliar application

The current study was performed on eight years old peach (Prunus persica L. Batsch) trees cv. Florida prince to study the influence of spraying of commercial nano fertilizer on vegetative growth, pollen grain viability, yield, and fruit quality of the "Florida prince" peach cultivar. Furthermore, extracts from the nanofertilizer treated leaves were studied for their bioactivity as insecticidal or bactericidal activities against some stored grain insects and plant bacterial pathogens. Seventy uniform peach trees were sprayed three time as follow: before flowering; during full bloom, and one month later in addition using the water as a control. Commercial silver particales (Ag NPs) at 10, 12.5, and 15 mL/L and zinc particales (Zn NPs) at 2.5, 5 and 7.5 mL/L as recommended level in a randomized complete block design in ten replicates/trees. Spraying Ag NP at 15 mL/L increased shoot diameter, leaf area, total chlorophyll, flower percentage, fruit yield and fruit physical and chemical characteristics, followed by Ag NPs at 12.5 mL/L and Zn NPs at 7.5 mL/L. Moreover, Zn and Ag NPs caused a highly significant effect on pollen viability. Different type of pollen aberrations were detected by Zn NPs treatment. The commercial Ag NPs showed a high increase in pollen viability without any aberrations. The Ag NPs significantly increased the pollen size, and the spores also increased and separated in different localities, searching about the egg for pollination and fertilization. Peach leaves extract was examined for their insecticidal activity against rice weevil (Sitophilus oryzea L.) and the lesser grain borer (Rhyzopertha dominica, Fabricius) by fumigation method. The antibacterial activity of all treatments was also performed against molecularly identified bacteria. Ag NPs treated leaves extract at concentration 3000 µg/mL were moderate sufficient to inhibit all the bacterial isolates with inhibition zone (IZ) ranged 6–8.67 mm with high efficiency of acetone extracts from leaves treated with Ag NPs compared with Zn NPs. Also, S. oryzae was more susceptible to acetone extracts from leaves treated with both nanomaterials than R. dominica.

Green synthesis, characterization, antibacterial and biofilm inhibitory activity of silver nanoparticles compared to commercial silver nanoparticles

This study was aimed to fabricate Zataria multiflora-derived silver nanoparticles (AgNPs) and evaluate the antibacterial activity and biofilm inhibitory activity of plant-mediated fabricated AgNPs (P-AgNPs) compared to commercial AgNPs (C-AgNPs) against Staphylococcus aureus ATCC 25923. The P-AgNPs were characterized by using UV–vis spectroscopy, Transmission electron microscopy (TEM), Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM), Energy Dispersive X-ray spectroscopy (EDX), Dynamic Light Scattering (DLS), and Fourier Transform Infrared (FT-IR) spectrum. The P-AgNPs were formed fairly uniform in size with a spherical morphology and an average hydrodynamic diameter of 25.5 nm at pH value of 9. Besides, the EDX analysis confirmed the presence of silver ions in the fabricated P-AgNPs. The FT-IR analysis also confirmed the presence of different functional groups on the surface of P-AgNPs. The P-AgNPs and C-AgNPs represented significant antibacterial activity with minimum inhibitory concentration (MIC) of 4 and 8 µg/mL against S. aureus, respectively. Both P-AgNPs and C-AgNPs at the concentrations of 0.5, 1, 2, and 4*MIC caused strong biofilm, weak biofilm, weak biofilm and no biofilm, respectively. Notably, at the concentrations of ≥8 µg/mL, both types of AgNPs exhibited significant biofilm inhibitory activity, whereas at the lower concentrations, the P-AgNPs showed greater biofilm inhibition formed by S. aureus.

Antibacterial and wound healing–promoting effect of sponge-like chitosan-loaded silver nanoparticles biosynthesized by iturin

Silver nanoparticles (AgNPs) are widely used in wound dressing, but are limited in the application due to its high toxicity at effective concentrations. iturin-AgNPs was previously found to have much higher antibacterial activity at lower AgNPs content than the commercial AgNPs. To verify its potential application in the promotion of wound healing, a chitosan (CS) composite sponge dressing–loaded iturin-AgNPs was developed and evaluated for their antibacterial activity in vitro and used for wound healing in vivo. As results, the synthesized CS dressing had high porosity and water absorption. As expected, the antibacterial activity of CS dressing was significantly promoted by the incorporation of iturin-AgNPs. The CS dressing–loaded iturin-AgNPs showed more effective inhibition of bacterial infection and promotion of wound healing processing and quality than the commercial wound dressing loaded AgNPs in vivo. The mechanisms for the promotion of wound healing by the CS dressing-loaded iturin-AgNPs were found as the enhancement of re-epithelialization and collagen formation, as well as the increased antibacerial activity. No toxicity was found to all organs of mice. The study developed an efficient way to enhance the antibacterial activity of CS dressing loaded AgNPs at low toxicity, which has great potential in wound care application.

Synthesis of silver nanoparticles stabilised by PVP for polymeric membrane application: a comparative study

ABSTRACT Silver nanoparticles (AgNPs) has the potential for membrane development with antibacterial properties. However, the synthesis method and parameter are crucial factors in determining nanoparticles formation and nucleation process. This study presents the effects of precursor concentration and synthesis temperature towards AgNPs formation in two distinctive methods. The results have shown a significant variation of AgNPs-1 and AgNPs-2 synthesised with different synthesis parameters. With respect to particles size determined using particle size analyser, the best synthesis condition for AgNPs-1 was at 25°C using 0.255 g AgNO3 while for AgNPs-2 was at 75°C using 0.03 mol/L AgNO3. The characteristics of selected AgNPs-1 and AgNPs-2 were analysed via Uv-Vis, FTIR, FESEM, EDX and HR-TEM. The efficiency of AgNPs-1 and AgNPs-2 were compared with commercial AgNPs based on its antibacterial performances towards E. coli and S. aureus using bacteria plate count method. Remarkably, both synthesised AgNPs possessed improved bactericidal effect compared to commercial AgNPs.

Green Synthesis of Silver Nanoparticles from Phaseolus vulgaris L. Extracts and Investigation of their Antifungal Activities

In this study, we aimed to synthesize silver nanoparticles (AgNPs) using leaf, root, and stem extracts of Phaseolus vulgaris L. (Yunus-90) and elucidate their antifungal activities. In this regard, the prepared AgNPs have been characterized by using UV-vis, FT-IR, TEM, SEM, and DLS techniques. Then, the antifungal activity of both synthesized and commercially purchased AgNPs was investigated via (i) agar well diffusion, (ii) fungal colony morphotype diversity, (iii) inhibition of hyphae and (iv) minimum inhibition concentration (MIC) analyses against Colletotrichum sp., Fusarium oxysporum, Fusarium acuminatum, Fusarium tricinctum, Fusarium graminearum, Fusarium incarnatum, Rhizoctonia solani, Sclerotinia sclerotiorum, and Alternaria alternata. The AgNPs derived from the leaf extract displayed significantly higher levels of antifungal activity relative to the AgNPs prepared from the root and stem extracts. The commercial AgNPs also displayed lower antifungal activity than their green equivalents synthesized in this research, and even a low (~50 μg/mL) concentration of synthesized AgNPs was found to be effective in suppressing the growth of Fusarium tricinctum and Colletotrichum sp.

Highly efficient nanomedicine from cationic antimicrobial peptide-protected Ag nanoclusters.

Designing the homogeneous assembly of the bio-nano interface to fine-tune the interactions between the nanoprobes and biological systems is of prime importance to improve the antimicrobial efficiency of nanomedicines. In this work, highly luminescent silver nanoclusters with the homogeneous conjugation of an antimicrobial peptide (referred to as Dpep-Ag NCs) were achieved via the reduction-decomposition-reduction process as a single package. The as-designed Dpep-Ag NCs inherited the two distinctive features of bactericides from the Ag+ species and the antimicrobial peptide of Dpep, and exhibited enhanced bacterial killing efficiency compared with other control groups including BSA-capped Ag NCs and the original antimicrobial peptide bactenecin (Opep)-protected Ag nanoparticles (Opep-Ag NPs). The ultrasmall size feature of Dpep-Ag NCs combined with the positively charged bactericidal tail allow a better interface and interaction with the cell membrane owing to the selective targeting of lipopolysaccharides in the Gram-negative bacteria and electrostatic interaction, facilitating the membrane permeability. Dpep-Ag NCs restrained the E. coli growth visibly and outperformed commercial Ag NPs (30 nm) with reduced (ca. 100-fold) minimal inhibitory concentration. The analysis of infected wound sizes and tissues treated with Dpep-Ag NCs in a murine model reveal obvious differences in the healing effect compared with the other counterparts, demonstrating its antibacterial efficiency in practical application.

Sex-dependent and organ-specific toxicity of silver nanoparticles in livers and intestines of adult zebrafish

Silver nanoparticles (AgNPs) have been increasingly manufactured and thus are increasingly detected in aquatic systems. However, there are still some overlooked factors (e.g., organism sex) in the field of nano-toxicological assessment. In this study, to explore the role of sex in nanotoxicity, adult male and female zebrafish were exposed to 100 μg/L of two uncoated commercial AgNPs with primary sizes 20 nm and 80 nm for 2 weeks, after which the impacts of AgNPs on intestines and livers of both male and female zebrafish were assessed using a suite of biomarkers. Results demonstrated that the intestinal Na/K-ATPase activity as well as the superoxide dismutase activity in male zebrafish differed significantly between 20-nm AgNPs and 80-nm AgNPs treatments (p < 0.05), indicating 20-nm AgNPs showing higher toxicity to zebrafish than the 80-nm AgNPs. Also, we noted that the used AgNPs induced sex-dependent effects on growth indices, oxidative/anti-oxidative status, neural signaling and hepatic lipid metabolism, with the male zebrafish being more sensitive to AgNPs than the females. Further, the tested AgNPs impaired the intestine much more seriously than the liver, as evidenced by the disruptions of Na/K-ATPase and antioxidant system in intestine but not in liver. These findings imply that prolonged exposure to AgNPs might induce size-related, sex-dependent, and organ-specific toxicity to adult zebrafish, thereby may significantly extend our understanding of the toxic effects of AgNPs in aquatic environment.

Silver nanoparticles-decorated and mesoporous silica coated single-walled carbon nanotubes with an enhanced antibacterial activity for killing drug-resistant bacteria

The mounting threat of antibiotic-resistant bacterial infections has made it imperative to develop innovative antibacterial strategies. Here we propose a novel antibacterial nanoplatform of silver nanoparticles-decorated and mesoporous silica coated single-walled carbon nanotubes constructed via a N-[3-(trimethoxysilyl)propyl]ethylene diamine (TSD)-mediated method (SWCNTs@mSiO2-TSD@Ag). In this system, the outer mesoporous silica shells are able to improve the dispersibility of SWCNTs, which will increase their contact area with bacteria cell walls. Meanwhile, the large number of mesopores in silica layers act as microreactors for in situ synthesis of Ag NPs with controlled small size and uniform distribution, which induces an enhanced antibacterial activity. Compared with TSD modified mesoporous silica coated single-walled carbon nanotubes (SWCNTs@mSiO2-TSD) and commercial Ag NPs, this combination nanosystem of SWCNTs@mSiO2-TSD@Ag exhibits much stronger antibacterial performance against multi-drug-resistant bacteria Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) in vitro through damaging the bacterial cell membranes and a fast release of silver ions. Furthermore, the in vivo rat skin infection model verifies that SWCNTs@mSiO2-TSD@Ag have remarkably improved abilities of bacterial clearance, wound healing promoting as well as outstanding biocompatibility. Therefore, this novel nanoplatform indicates promising potentials as a safe and powerful tool for the treatment of clinical drug-resistant infections.

Freezing Facilitates Formation of Silver Nanoparticles under Natural and Simulated Sunlight Conditions.

Freezing is essential in the light-mediated transformation of organic pollutants. However, the effects of the freezing process on the reduction of Ag+ by natural organic matter (NOM) remains unclear, causing significant uncertainties in the natural formation of silver nanoparticles (AgNPs). This study investigated the sunlight-induced reduction of Ag+ by NOM under natural or controlled freezing processes. Natural (outdoor) freezing experiments demonstrated intense aggregation and precipitation of AgNPs in three aqueous media, including a NOM solution and two river water samples, under natural sunlight irradiation. Indoor experiments under simulated sunlight irradiation and controlled freezing processes showed that freezing at -20 °C and repeated freeze-thaw cycles (-20 to 4 °C) drastically accelerated the formation and growth of AgNPs compared to maintenance at 4 °C. Finally, under the natural freezing process, commercial AgNPs were found to influence the redox reduction of Ag+ probably through a reduction in dissolution rates and homoaggregation with AgNPs newly formed in the river water samples. Additionally, the enhancement effect of freezing on AgNP formation was confirmed in the presence of Ag+ and AgNPs both at environmentally relevant concentration levels, especially upon light irradiation. This work emphasizes the importance of freezing processes on the natural formation of AgNPs.