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1.
Environ Res ; 216(Pt 3): 114706, 2023 Jan 01.
Artigo em Inglês | MEDLINE | ID: mdl-36336094

RESUMO

Silver nanoparticles (AgNPs) are often used as antibacterial agents. Here, graphene-silver nanoparticles (G-Ag) and graphene-silver nanoparticles poly-vinylpyrrolidone (G-AgPVPy) were prepared by chemical reduction and in-situ polymerization of vinylpyrrolidone (VPy). The prepared G-Ag and G-AgPVPy composites were characterized using various techniques. The size of the AgNPs on the graphene surface in the prepared G-Ag and G-AgPVPy composites was measured as ∼20 nm. The graphene sheets size in the G-Ag and G-AgPVPy composites were measured as 6.0-2.0 µm and 4.0-0.10 µm, respectively, which are much smaller than graphene sheets in graphite powder (GP) (10.0-3.0 µm). The physicochemical analysis confirmed the formation of G-Ag and G-AgPVPy composites and even the distribution of AgNPs and PVPy on the graphene sheets. The synthesized composites (G-AgPVPy, G-Ag) exhibited a broad-spectrum antibacterial potential against both Gram-negative and Gram-positive bacteria. The lowest minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) values were calculated as >40 µg/mL using G-Ag and GP, while G-AgPVPy showed as 10 µg/mL against Staphylococcus aureus. Among GP, G-Ag, and G-AgPVPy, G-AgPVPy disturbs the cell permeability, damages the cell walls, and causes cell death efficiently. Also, G-AgPVPy was delivered as a significant reusable antibacterial potential candidate. The MIC value (10 µg/mL) did not change up to six subsequent MIC analysis cycles.


Assuntos
Grafite , Nanopartículas Metálicas , Grafite/química , Prata/química , Nanopartículas Metálicas/química , Escherichia coli , Testes de Sensibilidade Microbiana , Antibacterianos/farmacologia , Antibacterianos/química
2.
J Environ Sci (China) ; 124: 491-504, 2023 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-36182157

RESUMO

Ce1-xZrxO2 composite oxides (molar, x = 0-1.0, interval of 0.2) were prepared by a cetyltrimethylammonium bromide-assisted precipitation method. The enhancement of silver-species modification and catalytic mechanism of adsorption-transformation-desorption process were investigated over the Ag-impregnated catalysts for low-temperature selective catalytic oxidation of ammonia (NH3-SCO). The optimal 5 wt.% Ag/Ce0.6Zr0.4O2 catalyst presented good NH3-SCO performance with >90% NH3 conversion at temperature (T) ≥ 250°C and 89% N2 selectivity. Despite the irregular block shape and underdeveloped specific surface area (∼60 m2/g), the naked and Ag-modified Ce0.6Zr0.4O2 solid solution still obtained highly dispersed distribution of surface elements analyzed by scanning electron microscope-energy dispersive spectrometer (SEM-EDS) (mapping), N2 adsorption-desorption test and X-ray diffraction (XRD). H2 temperature programmed reduction (H2-TPR) and X-ray photoelectron spectroscopy (XPS) results indicated that Ag-modification enhanced the mobility and activation of oxygen-species leading to a promotion on CeO2 reducibility and synergistic Ag0/Ag+ and Ce4+/Ce3+ redox cycles. Besides, Ag+/Ag2O clusters could facilitate the formation of surface oxygen vacancies that was beneficial to the adsorption and activation of ammonia. NH3-temperature programmed desorption (NH3-TPD) showed more adsorption-desorption capacity to ammonia were provided by physical, weak- and medium-strong acid sites. Diffused reflectance infrared Fourier transform spectroscopy (DRIFTS) experiments revealed the activation of ammonia might be the control step of NH3-SCO procedure, during which NH3 dehydrogenation derived from NHx-species and also internal selective catalytic reduction (i-SCR) reactions were proposed.


Assuntos
Amônia , Prata , Amônia/química , Catálise , Cetrimônio , Oxirredução , Óxidos , Oxigênio
3.
Spectrochim Acta A Mol Biomol Spectrosc ; 284: 121817, 2023 Jan 05.
Artigo em Inglês | MEDLINE | ID: mdl-36084581

RESUMO

With the growing popularity of the non-destructive technique, surface-enhanced Raman spectroscopy (SERS) demands a highly sensitive and reproducible plasmonic nanoparticles substrate. In this study, a novel bimetallic core-shell nanoparticles (Au@Ag@mSiO2NP) substrate consisting of a gold core, silver shell, and a mesoporous silica coating was synthesized. The mesoporous coating structure was created by employing template molecules such as surfactant and their subsequent removal allowing selective screening based on the size of analyte molecules. Results showed that the plasmonic substrate could selectively enhance small molecules by preventing large macromolecules to reach the exciting zone of the substrate core, achieving the detection of chloramphenicol in milk samples with a detection limit of 6.68 × 10-8 M. Moreover, the mesoporous coating provided additional stability to the Au@Ag nanoparticles, leading to the reusability of the substrate. Thus, this work offered a simple and smart Au@Ag@mSiO2NP substrate for effective SERS detection of analytes.


Assuntos
Nanopartículas Metálicas , Prata , Cloranfenicol , Ouro/química , Nanopartículas Metálicas/química , Dióxido de Silício/química , Prata/química , Análise Espectral Raman/métodos , Tensoativos
4.
Spectrochim Acta A Mol Biomol Spectrosc ; 284: 121789, 2023 Jan 05.
Artigo em Inglês | MEDLINE | ID: mdl-36088743

RESUMO

Chromium (Cr) is a toxic environmental pollutant that majorly exists in trivalent and hexavalent forms. Though Cr(VI) is more dangerous than Cr(III), the trivalent Cr forms complexes with environmentally-available organic molecules. This makes them potentially harmful and difficult to detect. In this study, we have designed an ultrasensitive plasmonic nanosensor using citrate and PVP functionalized Ag nanoparticles (Ag-citrate-PVPNPs) for the detection of trivalent chromium organic complexes such as Cr(III)-EDTA (Cr-E), Cr(III)-acetate (Cr-A), Cr(III)-citrate (Cr-C) and Cr(III)-tartrate (Cr-T). The nanoparticles (NPs) were structurally characterized by XRD, SEM, HRTEM, SAED, EDX and elemental mapping. The citrate and PVP molecules played a vital role in the detection mechanism and stability of the sensor. Upon detection, the yellow-colored Ag-citrate-PVP NPs turned into different shades of brown depending on the type of the Cr complex and concentration. It was accompanied by diminishing and/or shifting UV-Visible absorbance peaks due to the aggregation of Ag-citrate-PVP NPs. Further, a linear relationship was observed between absorbance reduction and analyte concentration. The selectivity tests showed that the sensor was non-functional to other metal ions and inorganic anions. The sensor was optimized using pH and temperature studies. The mechanism of detection was elucidated with the help of characterization techniques such as Raman spectroscopy, FTIR, XPS and UV-visible spectrophotometer. The limit of detection (LOD) was found to be 3.29, 4.87, 1.76 and 1.79 nM for Cr-E, Cr-A, Cr-C and Cr-T complexes respectively. This study provides a rapid and sensitive approach for the detection of multiple Cr(III)-organic complexes present in an aqueous solution.


Assuntos
Nanopartículas Metálicas , Poluentes Químicos da Água , Cromo/análise , Ácido Cítrico/química , Ácido Edético/química , Nanopartículas Metálicas/química , Prata/química , Tartaratos , Poluentes Químicos da Água/análise
5.
Talanta ; 251: 123795, 2023 Jan 01.
Artigo em Inglês | MEDLINE | ID: mdl-35952502

RESUMO

The development of a biosensing platform with high sensitivity, high specificity, and low cost for the detection of biomarkers, especially one that is programmable and universal, is critical for disease surveillance and diagnosis, yet it remains a difficulty. Herein, we combined the clustered regularly interspaced short palindromic repeats (CRISPR)/Cas system with a fluorescent label-free biosensor platform for sensitive and specific detection of disease-related protein, small molecule and nucleic acid. In this strategy, we designed an exonuclease III-mediated target cycle and released a universal trigger chain to stimulate the enzyme activity of CRISPR/Cas12a for additional signal amplification. The hydrolysis of ssDNA-templated silver nanoclusters (ssDNA-Ag NCs) as the reporter probe resulted in a significant decrease of fluorescence intensity. This biosensing platform can be flexibly used to the sensitive and specific determination of protein, small molecule, or microRNA in biological samples by simply transforming the target recognized sequences in the DNA hairpin. In this work, a new label-free sensing system used the fluorescent ssDNA-Ag NCs as the signal output does not need to be marked in advance and has no background signal. In addition, the method has the advantages of low cost, simple operation and high speed, and provides an innovative idea for the development of a powerful clinical diagnosis tool.


Assuntos
Técnicas Biossensoriais , MicroRNAs , Biomarcadores , Técnicas Biossensoriais/métodos , Sistemas CRISPR-Cas , DNA/genética , DNA de Cadeia Simples/genética , Limite de Detecção , Prata
6.
J Colloid Interface Sci ; 629(Pt A): 766-777, 2023 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-36099844

RESUMO

The size of silver nanoparticles (Ag NPs) and loading amount of Ag NPs onto their substrate/carrier are two key factors for their efficient applications. Herein, we present a facile method for in situ synthesizing ultrafine and highly loaded Ag NPs on the surface of tannin-coated catechol-formaldehyde resin (TA-CFR) nanospheres. TA-CFR nanospheres act as green and highly efficient reducing agents for converting silver ions (Ag+) into Ag NPs, and the size of resultant Ag NPs is only âˆ¼ 7.5 nm, and the Ag NPs loading capacity of TA-CFR is as high as 61.5 wt%, both of which contribute to the very high specific surface area of Ag NPs. Consequently, the as-synthesized TA-CFR@Ag composites show high catalytic performance, and the catalytic rate for the reduction of 4-nitrophenol is almost 10 times higher than that of the control. Meanwhile, TA-CFR@Ag composites also possess high antibacterial activity, efficiently inhibiting the growth of Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). Furthermore, tannin coating (thickness: ∼ 15 nm) minimizes the aggregation of Ag NPs, and enhances the reusability and stability of resultant Ag NPs, because of their high surface charges (the zeta potential is up to -65.5 ± 1.9 mV) and strong coordination capability with Ag NPs. This work provides a new frontier to develop multifunctional nanomaterials focusing on the green catalyst synthesis and environmental-remedy applications.


Assuntos
Nanopartículas Metálicas , Prata , Prata/farmacologia , Antibacterianos/farmacologia , Staphylococcus aureus , Escherichia coli , Substâncias Redutoras , Catecóis , Taninos , Formaldeído , Testes de Sensibilidade Microbiana
7.
Food Chem ; 402: 134241, 2023 Feb 15.
Artigo em Inglês | MEDLINE | ID: mdl-36126581

RESUMO

A simple, ultra-sensitive, and super-stable hydrophobic SERS platform for detection of melamine in milk is developed. The hydrophobic SERS platform was constructed via directly growing hydrophobic carbon/silver nanoparticles on glass by in-situ one-step carbonization using hexadecylpyridinium chloride monohydrate as stabilizer and reducing agent. The performances of SERS platform are systematically studied by using Rhodamine 6G (R6G) as a model, which achieves detection level of 10-13 M and enhancement factor of 3.4 × 1010 for R6G detection with good uniformity and reproducibility, as well as 110 days stability in air. The FDTD simulation was used to confirm SERS enhancement mechanism. More importantly, SERS platform delivers good linear property in the range from 0.01 to 100 ppm, and low limit detection of 9 ppb for melamine detection in milk through direct drop on the platform. The SERS platform could have great applications in food safety, environmental monitoring, biomedicine and other fields.


Assuntos
Nanopartículas Metálicas , Prata , Animais , Prata/química , Nanopartículas Metálicas/química , Leite/química , Análise Espectral Raman , Substâncias Redutoras/análise , Reprodutibilidade dos Testes , Cetilpiridínio/análise , Cloretos/análise , Limite de Detecção , Carbono/análise
8.
J Colloid Interface Sci ; 629(Pt A): 864-872, 2023 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-36152616

RESUMO

HYPOTHESIS: The dynamic behaviors of colloidal particles have already been considered as one of the key issues in their practical application, such as aggregation and dispersion. However, it is still remained significant challenge in developing the real time techniques to capture their dynamic tracks. The nano/subnanometer scale gap generated during the colloidal collisions served as the critical location for amplifying the Raman signal, so called as gap ("hot spots") based surface enhanced Raman spectroscopy (SERS). The alternating reversible "spike" of SERS intensity and irreversible step in baseline intensity are contributed to the preferred stability and the aggregation of colloid respectively. EXPERIMENTS: A facile approach is developed to track colloidal stability in real-time based on collisions and SERS. The effects of particle concentration, the dispersion medium, and solution pH on colloidal stability are systematically investigated, and the SERS intensity of a simulated single-like "hot spot" was calculated by combining a SEM position with SERS mapping technology to estimate the intensity of single-particle collision. FINDINGS: The colloidal particles exhibited higher stability in the solution with lower particle concentration, higher viscosity and neutral medium. The SERS intensity of single-particle collision was estimated to be about 2.06 × 10-7 counts, and the average number of collisions for the 0.13 mmol/dm3 SiO2@Ag solution was about 1.11 × 108 times/spike in the "spikes" with SERS intensity of 23.0 cps. It is believed that the SERS based strategy would be developed as a promising tool for obtaining the deeper insight into the nature of collisions in the colloidal science.


Assuntos
Prata , Análise Espectral Raman , Análise Espectral Raman/métodos , Prata/química , Dióxido de Silício , Propriedades de Superfície , Coloides/química
9.
Food Chem ; 400: 133960, 2023 Jan 30.
Artigo em Inglês | MEDLINE | ID: mdl-36063680

RESUMO

A proper understanding of silver (Ag) nanoparticles properties is fundamental for developing new antimicrobial agents. In this study, Ag nanoparticles were obtained by green synthesis methods using natural reducing agents present in extracts of apples, oranges, potatoes, red pepper, white onion, garlic and radish. The antimicrobial properties of respective nanoparticles, expressed as the minimum inhibitory concentration, were assessed against Staphylococcus aureus, Bacillus cereus, Escherichia coli, and Candida krusei. Characterization of Ag nanoparticles was done with the application of transmission electron microscopy, X-ray diffraction and UV-vis spectroscopy. The obtained results led to the conclusions that in each extract (pH from 2.1 to 6.2) were obtained specific particles (size from 9 to 30 ± 2 nm) with different antimicrobial activity. Our study indicates that plant extracts gives the Ag nanoparticles specific properties, yet the best antimicrobial properties show nanoparticles obtained in the presence of potato extract.


Assuntos
Anti-Infecciosos , Nanopartículas Metálicas , Antibacterianos/química , Antibacterianos/farmacologia , Anti-Infecciosos/química , Anti-Infecciosos/farmacologia , Escherichia coli , Química Verde/métodos , Nanopartículas Metálicas/química , Testes de Sensibilidade Microbiana , Extratos Vegetais/química , Extratos Vegetais/farmacologia , Substâncias Redutoras , Prata/química , Prata/farmacologia , Espectroscopia de Infravermelho com Transformada de Fourier
10.
Food Chem ; 403: 134415, 2023 Mar 01.
Artigo em Inglês | MEDLINE | ID: mdl-36358072

RESUMO

In this work, a new sustainable melamine detection method was developed. Biomass-derived carbon dots (CDs) were successfully prepared by ionic liquid (1-Allyl-3-methylimidazolium chloride, IL) hydrothermal method using agricultural waste corn cob as the carbon source, and combined with silver nanoparticles (AgNPs) to construct fluorescent probe CDs@IL-AgNPs. The probe was characterized and the formation mechanism of the probe was discussed. The direct detection of H2O2 and the indirect sensitive detection of melamine were realized. The detection limit of melamine was 0.94 µmol/L, which is far lower than the minimum allowable amount of melamine in milk powder (7.95 µmol/L). The high sensitivity and selectivity probe was used to detect melamine in commercial dairy products, and the recovery rate of standard addition was between 94 % and 110 %. This study provides valuable new application ideas for the detection of melamine in dairy products and the low-carbon and environmentally friendly treatment of agricultural waste.


Assuntos
Líquidos Iônicos , Nanopartículas Metálicas , Animais , Prata , Corantes Fluorescentes , Peróxido de Hidrogênio/análise , Zea mays , Carbono , Limite de Detecção , Leite/química , Triazinas/análise
11.
Spectrochim Acta A Mol Biomol Spectrosc ; 285: 121843, 2023 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-36099730

RESUMO

Surface-enhanced Raman scattering (SERS) enables food contaminants monitoring become facile and efficient. Herein, a facile strategy of integrating three-dimensional Ni form with Co/Ni bimetal-organic frameworks combining Ag nanoparticles via electrochemical synthesis method was proposed to develop a high-performance SERS substrate (CoNi-ZIFs@Ag@NF) for efficient detection of tetracycline. The flexible Ni foam (NF) acted as scaffold which can contribute to dramatically enhancing intrinsic electrical conductivity and endowing prepared substrate with high stability and uniform distribution of Ag nanoparticles. Furthermore, the pre-concentration effect of CoNi-ZIFs@Ag@NF for target molecules enhanced SERS performance dramatically. Besides, tetracycline was sensitively detected using CoNi-ZIFs@Ag@NF with low limit of detection (1.0 × 10-11 M) and wide linear detection range (10-10 - 10-5 M) in aqueous solution. Also, the satisfactory recovery (94.45 - 114.25 %) was realized with less than 6.78 % of RSD in real samples. This method would provide a potential and high-performance substrate for SERS monitoring of tetracycline in food and environment.


Assuntos
Nanopartículas Metálicas , Prata , Prata/química , Nanopartículas Metálicas/química , Análise Espectral Raman/métodos , Técnicas Eletroquímicas , Tetraciclina , Antibacterianos
12.
Spectrochim Acta A Mol Biomol Spectrosc ; 284: 121779, 2023 Jan 05.
Artigo em Inglês | MEDLINE | ID: mdl-36041262

RESUMO

Online monitoring of antibiotics in the environment attracts more and more attention. Surface-enhanced Raman scattering (SERS) is a promising technique for the detection of trace amounts of antibiotics in the environment, which is fast, non-invasive and sensitive. To investigate the enrichment of trace amounts of antibiotics in water, polyethylene microplastics (PE MPs) were prepared as sorbents to simply concentrate enrofloxacin, ciprofloxacin hydrochloride monohydrate and triclosan in water, followed by the SERS measurement of antibiotics extract washed from MPs on an AgNPs@Si SERS substrate. Limit of detection of Rhodamine 6G is 2.1 × 10-12 M achieved from the AgNPs@Si SERS, indicating a high enhancement. The detection results show that SERS peaks of the antibiotics could be observed from the spectra of the extracts eluted from MPs, indicating MPs could adsorb and desorb antibiotics from water. Besides, for enrofloxacin and triclosan, the intensity of SERS measured from the MPs extracts are higher than that of directly from the spiked water, demonstrating the proposed method could lower the detectable concentration of hydrophobic antibiotics in water. Moreover, the proposed MPs sorbents combined with SERS method was applied to detect the antibiotics in real river water, with minimal detection of 10-10 M, 10-8 M, and 10-8 M achieved for enrofloxacin, ciprofloxacin hydrochloride monohydrate and triclosan, respectively. The proposed method provides a promising simple, rapid and low reagent consuming means for monitoring antibiotics in water.


Assuntos
Antibacterianos , Triclosan , Antibacterianos/análise , Ciprofloxacina , Enrofloxacina , Microplásticos , Plásticos , Polietilenos , Prata/química , Análise Espectral Raman/métodos , Tecnologia , Água
13.
Spectrochim Acta A Mol Biomol Spectrosc ; 284: 121735, 2023 Jan 05.
Artigo em Inglês | MEDLINE | ID: mdl-36049297

RESUMO

A novel surface enhanced Raman scattering (SERS) method was developed based on Ag nanowires embedded into functionalized metal-organic framework ZIF-67 (ZIF-67@Ag NWs) composite as substrate, which was applied for rapid recognition and sensitive detection of six PAEs. The Raman signals for PAEs detection were gained at ZIF-67@Ag NWs substrate mainly due to the "sharp tip effect" of rough Ag nanowires and excellent absorptive capacity of ZIF-67 to capture targeted molecules into the electromagnetic field. Different structural PAEs, including carbon chain lengths, isomers, and substituents, were evaluated for SERS performance and characteristic peaks under the optimal conditions. The SERS spectra proved that different PAEs exhibited some typically characteristic peaks in favor of recognizing and distinguishing them. The ZIF-67@Ag NWs as SERS substrate was successfully applied to detect six PAEs and exhibited wide linear ranges, low detection limit (LOD), excellent repeatability and stability (such as dibutyl phthalate DBP: linear range of 10-2 âˆ¼ 10-12 mol/L, LOD 3 × 10-13 mol/L). The ZIF-67@Ag NWs substrate by SERS was implemented to determine trace DBP in plastics with satisfactory recoveries of 82.5 % ∼ 108.3 %. The proposed ZIF-67@Ag NWs substrate may provide an effective and promising SERS platform for recognition and quantitative determination of different structural PAEs in environment.


Assuntos
Nanopartículas Metálicas , Estruturas Metalorgânicas , Nanofios , Carbono , Dibutilftalato , Ésteres , Nanopartículas Metálicas/química , Ácidos Ftálicos , Plásticos , Prata/química , Análise Espectral Raman/métodos
14.
J Colloid Interface Sci ; 630(Pt A): 484-493, 2023 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-36265349

RESUMO

Particular matter (PM), oily wastewater, and microorganisms (e.g., bacteria) have caused serious environmental, health, and safety issues. However, the development of multifunctional filtration materials to address these problems remains a great challenge. Here, we present a series of gradient structured air filters by simply spray coating poly(vinyl alcohol-co-ethylene) (PVA-co-PE) nanofibers on nylon mesh, followed by silver nanowires (AgNWs). Interestingly, it is found that the ANF-6 air filter is an anisotropic Janus membrane with asymmetric wettability and translucency. The as-prepared ANF-6 air filter exhibits excellent water vapor transmission rate (4447.92 ± 184.78 g/(m2. d)), PM filtration (96.42 ± 0.64 % for PM0.3), photothermal (79.6 °C under 1sun in 150 s), thermal insulation, antibacterial, and oil water separation. Additionally, the obtained ANF-6 air filter was impregnated with carbon black (CB) dispersion and served as flexible pressure sensors to monitor human respiration rate (17 times/min) and wrist pulse rate (80 times/min). The gradient structured PVA-co-PE nanofibers and AgNWs network provides excellent air filtration, oil water separation, and sensitivity performance for the sensors. These results provide a new scheme for designing multifunctional filtration materials and wearable pressure sensors in the application of air filtration, oil water separation, and wearable electronics for monitoring human health.


Assuntos
Filtros de Ar , Nanofibras , Nanofios , Dispositivos Eletrônicos Vestíveis , Humanos , Prata
15.
J Colloid Interface Sci ; 631(Pt A): 66-76, 2023 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-36371827

RESUMO

We present a short peptide of only six amino acids that can be used in ambient conditions to simultaneously reduce either Au3+ or Ag+ ions, forming nanoparticles, and function as a stabilizing capping agent. At acidic pH, Hg2+ ions oxidize the silver nanoparticles and Fe2+ ions promote the aggregation of the gold nanoparticles. At alkaline conditions, Mn2+ ions induce the aggregation of the silver nanoparticles. Through the absorbance changes of these processes, these peptide-capped nanoparticles demonstrated a fast, selective, and sensitive pH-dependent detection system. The limit of detection of Hg2+, Mn2+, and Fe2+ was 319 nм, 184 nм, and 320 nм, respectively. Furthermore, the formed gold nanoparticles were successfully enveloped by a silver shell in a peptide-mediated photoreduction process. These bimetallic Au@Ag core/shell nanoparticles were characterized using UV-vis spectroscopy, high-resolution scanning transmission electron microscopy (HR-STEM), and energy dispersive X-ray spectroscopy (EDS). While prior studies used peptides as ligands for nanoparticles, the versatile abilities of the novel peptide presented in this study display the promising potential of using peptides for nanoparticles synthesis. This is because a single peptide can be used in a single-step one-pot synthesis to prepare and stabilize AuNPs, AgNPs, and Au@Ag core/shell nanoparticles, while also allowing to selectively probe different metal ions.


Assuntos
Mercúrio , Nanopartículas Metálicas , Ouro/química , Prata/química , Nanopartículas Metálicas/química , Íons , Peptídeos
16.
J Colloid Interface Sci ; 631(Pt A): 165-180, 2023 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-36375299

RESUMO

Silver nanoparticles (AgNPs) have found widespread commercial applications due to their unique physical and chemical properties. However, their relatively poor stability remains a main problem. An ideal way to improve the stability of AgNPs is not only to endow colloidal stability to individual nanoparticles but also to protect them from environmental factors that induce their agglomeration, like variation of ionic strength and pH, presence of macromolecules, etc. Mesoporous calcium carbonate vaterite crystals (CaCO3 vaterite) have recently attracted significant attention as inexpensive and biocompatible carriers for the encapsulation and controlled release of both drugs and nanoparticles. This work aimed to develop an approach to load AgNPs into CaCO3 vaterite without affecting their properties. We focused on improving the colloidal stability of AgNPs by using different capping agents, and understanding the mechanism behind AgNPs loading and release from CaCO3 crystals. Various methods were applied to study the AgNPs and CaCO3 crystals loaded with AgNPs (CaCO3/AgNPs hybrids), such as scanning and transmission electron microscopy, X-ray diffraction, infrared and mass spectrometry. The results demonstrated that polyvinylpyrrolidone and positively charged diethylaminoethyl-dextran can effectively keep the colloidal stability of AgNPs during co-precipitation with CaCO3 crystals. CaCO3/AgNPs hybrids composed of up to 4 % weight content of nanoparticles were produced, with the loading mechanism being well-described by the Langmuir adsorption model. In vitro release studies demonstrated a burst release of stable AgNPs at pH 5.0 and a sustained release at pH 7.5 and 9.0. The antibacterial studies showed that these hybrids are effective against Escherichia coli, methicillin-resistant Staphylococcus aureus and Pseudomonas aeruginosa, three important bacteria responsible for nosocomial infections. The developed approach opens a new way to stabilise, protect, store and release AgNPs in a controlled manner for their use as antimicrobial agents.


Assuntos
Nanopartículas Metálicas , Staphylococcus aureus Resistente à Meticilina , Prata/química , Nanopartículas Metálicas/química , Carbonato de Cálcio/química , Antibacterianos/farmacologia , Antibacterianos/química , Escherichia coli , Testes de Sensibilidade Microbiana
17.
Braz. j. biol ; 83: e244675, 2023. tab, graf
Artigo em Inglês | LILACS, VETINDEX | ID: biblio-1339348

RESUMO

Abstract Several species of thymus have therapeutic properties, so they are used in traditional medicine. In this work was carried out to synthesize Thymus vulgalis silver nanoparticles (TSNPS) and evaluate antioxidant and antimicrobial activities of TSNPS and T. vulgalis essential oil extract (TEOE). The essential oils analyzed by GC-MS and were characterized. Major compounds of phenol, 2 methyl 5 (1 methylethyle) (CAS), thymol and 1,2 Benzene dicarboxylic acid, 3 nitro (CAS) (48.75%, 32.42% and 8.12%, respectively) were detected. Results demonstrated that the TSNPS gave a highest DPPH radical scavenging activity, it was obtained 97.2 at 1000 ug/ml. TSNPS, Thymus + Hexane (T+H), Thymus + Ethanol (T+E) gave the greatest antimicrobial activity than amoxicillin (AM) and ciprofloxacin (CIP). In conclusion: The essential oil of thymus (Vulgaris) and thymus (Vulgaris) silver nanoparticles can be a good source of natural preservatives as an antioxidant and antimicrobial agents for increasing the shelf life of foodstuffs.


Resumo Diversas espécies de timo possuem propriedades terapêuticas, por isso são utilizadas na medicina tradicional. Neste trabalho foi realizado para sintetizar nanopartículas de prata Thymus vulgalis (TSNPS) e avaliar as atividades antioxidante e antimicrobiana de TSNPS e extrato de óleo essencial de T. vulgalis (TEOE). Os óleos essenciais analisados por GC-MS e foram caracterizados. Os principais compostos de fenol, 2 metil 5 (1 metiletilo) (CAS), timol e ácido 1,2 Benzenodicarboxílico, 3 nitro (CAS) (48,75%, 32,42% e 8,12%, respectivamente) foram detectados. Os resultados demonstraram que o TSNPS deu uma maior atividade de eliminação do radical DPPH , foi obtido 97,2 a 1000 ug / ml. TSNPS, Timo + Hexano (T + H), Timo + Etanol (T + E) deu a maior atividade antimicrobiana do que amoxicilina (AM) e ciprofloxacina (CIP). Em conclusão: O óleo essencial de nanopartículas de prata do timo (Vulgaris) e do timo (Vulgaris) pode ser uma boa fonte de conservantes naturais como agentes antioxidantes e antimicrobianos para aumentar a vida útil de alimentos.


Assuntos
Óleos Voláteis/farmacologia , Thymus (Planta) , Nanopartículas Metálicas , Anti-Infecciosos/farmacologia , Prata , Antioxidantes/farmacologia
18.
J Environ Manage ; 325(Pt A): 116578, 2023 Jan 01.
Artigo em Inglês | MEDLINE | ID: mdl-36419287

RESUMO

Recent advances in immobilized biologic systems for decolorizing azo dyes are gaining great attention due to microorganisms like bacteria and nanoparticles that could stimulate decolorization. Enhanced decolorization performance was observed in this study, indicating the great potential of the immobilized complex of bacterial cells and AgNPs as an alternative to the traditional biological processes to improve the performance of biological systems. The biodegradation and decolorization of Disperse Blue183 (DB 183) were investigated utilizing a novel combination of Enterococcus casseliflavus strain A2 mediated by silver nanoparticles synthesized by Marinospirillum alkaliphilum strain N in three different conditions. Ⅰ: free bacterial strain A2 (100% dye removal in 72 h), Ⅱ: immobilized bacterial strain A2 in Ca-Alg beads (100% dye removal in 15 h), and Ⅲ: immobilized bacterial strain A2 with silver nanoparticles (AgNPs) as support in Ca-Alg beads (100% dye removal in 9 h). The presence of bacterial cells and nanoparticles in Ca-Alg beads was assessed and proved by scanning electron microscope (SEM) and X-ray energy diffraction (EDX) analysis. Moreover, DB 183 and its decolorization metabolites were evaluated by applying UV-Vis, infrared spectroscopy (FTIR), and GC/MS, and the results showed that the dye was degraded. The antimicrobial effect, brine shrimp toxicity (BST) test, and mutagenicity assay in the presence and absence of metabolic activation (+S9/-S9) were run to assess DB 183 and metabolite obtained from biodegradation. The antimicrobial activity of DB 183 disappeared after treatment. Further, the results of the BST test determined that the dye has moderate biotoxicity (LC50:0.064 mg/mL), and the after-treatment product was not toxic. According to the Ames test, DB 183 had mutagenicity effect (69-84%), and the metabolic activation increased the mutagenicity of the dye) 12-25%). However, the percentage mutagenicity of decolorization products decreased, ranging from 50 to 80% without activation (-S9) and 83-96% in present activation (+S9). This work used the immobilized bacterial cells and AgNPs Ca-Alg gel beads for the first time to introduce this kind of system as a suitable technique for rapid decolorization. Using this application enables a remarkable reduction in the time dedicated to the bioremediation of dyeing wastewater.


Assuntos
Anti-Infecciosos , Nanopartículas Metálicas , Mutagênicos , Prata , Corantes
19.
Carbohydr Polym ; 300: 120257, 2023 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-36372485

RESUMO

Nanocelluloses, such as cellulose nanofibers and nanocrystals, are sustainable nanomaterials that are generally extracted from natural raw materials in a top-down manner. These nanomaterials and their assemblies are facilitating new applications of biopolymers. However, creating nanostructures from conventional cellulosic materials including paper and cloth remains challenging. Herein, we report an approach for bottom-up nanostructuring of conventional microfibrous cellulose materials via a molecular self-assembly strategy. As a precursor cellulose material, paper was allowed to swell with aqueous phosphoric acid for the partial dissolution and hydrolysis of cellulose while maintaining its microfibrous structure. The generated cello-oligosaccharides in a dissolved state started to self-assemble upon adding water as a coagulant, resulting in nanospike-like assemblies on the microfiber surfaces. The resultant nanospiked papers were found to serve as a precursor for synthesizing silver nanoparticle-cellulose composites with bactericidal activities. Our findings promote the development of cellulose-based functional materials with nanostructures designed via molecular self-assembly.


Assuntos
Nanopartículas Metálicas , Nanopartículas , Nanoestruturas , Celulose/química , Hidrólise , Prata/química , Nanoestruturas/química , Nanopartículas/química
20.
J Environ Sci (China) ; 125: 616-629, 2023 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-36375944

RESUMO

The widely use of silver nanoparticles (AgNPs) as antimicrobial agents gives rise to potential environmental risks. AgNPs exposure have been reported to cause toxicity in animals. Nevertheless, the known mechanisms of AgNPs toxicity are still limited. In this study, we systematically investigated the toxicity of AgNPs exposure using Drosophila melanogaster. We show here that AgNPs significantly decreased Drosophila fecundity, the third-instar larvae weight and rates of pupation and eclosion in a dose-dependent manner. AgNPs reduced fat body cell viability in MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assays. AgNPs caused DNA damage in hemocytes and S2 cells. Interestingly, the mRNA levels of the entire metallothionein gene family were increased under AgNPs exposure as determined by RNA-seq analysis and validated by qRT-PCR, indicating that Drosophila responded to the metal toxicity of AgNPs by producing metallothioneins for detoxification. These findings provide a better understanding of the mechanisms of AgNPs toxicity and may provide clues to effect on other organisms, including humans.


Assuntos
Nanopartículas Metálicas , Prata , Humanos , Animais , Prata/toxicidade , Drosophila melanogaster/genética , Nanopartículas Metálicas/toxicidade , Espécies Reativas de Oxigênio , Drosophila , Mecanismos de Defesa
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