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An in situ SAXS investigation of the formation of silver nanoparticles and bimetallic silver-gold nanoparticles in controlled wet-chemical reduction synthesis.

ABSTRACT: We present a study on the formation of silver (Ag) and bimetallic silver-gold (AgAu) nanoparticles monitored by in situ SAXS as well as by ex situ TEM, XRD and UV-vis analysis in a flow reactor at controlled reaction temperature. The formation mechanism of the nanoparticles is derived from the structural parameters obtained from the experimental data. The evolution of the average particle size of pure and alloyed nanoparticles shows that the particle growth occurs initially by a coalescence mechanism. The later growth of pure silver nanoparticles is well described by Ostwald ripening and for the alloyed nanoparticles by a process with a significantly slower growth rate. Additionally, the SAXS data of pure silver nanoparticles revealed two major populations of nanoparticles, the first one with a continuous crystal growth to a saturation plateau, and the second one probably with a continuous emergence of small new crystals. The particle sizes obtained by SAXS agree well with the results from transmission electron microscopy and X-ray diffraction. The present study demonstrates the capability of an in situ investigation of synthesis processes using a laboratory based SAXS instrument. Online monitoring of the synthesis permitted a detailed investigation of the structural evolution of the system.

SUBMITTER: Garcia PRAF

PROVIDER: S-EPMC9418936 | biostudies-literature | 2020 Jan

REPOSITORIES: biostudies-literature

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An in situ SAXS investigation of the formation of silver nanoparticles and bimetallic silver-gold nanoparticles in controlled wet-chemical reduction synthesis.

Garcia Paulo R A F PRAF Prymak Oleg O Grasmik Viktoria V Pappert Kevin K Wlysses Wagner W Otubo Larissa L Epple Matthias M Oliveira Cristiano L P CLP

Nanoscale advances 20191125 1

We present a study on the formation of silver (Ag) and bimetallic silver-gold (AgAu) nanoparticles monitored by in situ SAXS as well as by ex situ TEM, XRD and UV-vis analysis in a flow reactor at controlled reaction temperature. The formation mechanism of the nanoparticles is derived from the structural parameters obtained from the experimental data. The evolution of the average particle size of pure and alloyed nanoparticles shows that the particle growth occurs initially by a co ...[more]

PMID: 36133991

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Project description:PurposeMulti- and extensively drug-resistant tuberculosis (TB) is a global threat to human health. It requires immediate action to seek new antitubercular compounds and devise alternate strategies. Nanomaterials, in the present scenario, have opened new avenues in medicine, diagnosis, and therapeutics. In view of this, the current study aims to determine the efficacy of phytogenic metal nanoparticles to inhibit mycobacteria.MethodsSilver (AgNPs), gold (AuNPs), and gold-silver bimetallic (Au-AgNPs) nanoparticles synthesized from medicinal plants, such as Barleria prionitis, Plumbago zeylanica, and Syzygium cumini, were tested against Mycobacterium tuberculosis and M. bovis BCG. In vitro and ex vivo macrophage infection model assays were designed to determine minimum inhibitory concentration (MIC) and half maximal inhibitory concentration of nanoparticles. Microscopic analyses were carried out to demonstrate intracellular uptake of nanoparticles in macrophages. Besides this, biocompatibility, specificity, and selectivity of nanoparticles were also established with respect to human cell lines.ResultsAu-AgNPs exhibited highest antitubercular activity, with MIC of <2.56 μg/mL, followed by AgNPs. AuNPs did not show such activity at concentrations of up to 100 μg/mL. In vitro and ex vivo macrophage infection model assays revealed the inhibition of both active and dormant stage mycobacteria on exposure to Au-AgNPs. These nanoparticles were capable of entering macrophage cells and exhibited up to 45% cytotoxicity at 30 μg/mL (ten times MIC concentration) after 48 hours. Among these, Au-AgNPs synthesized from S. cumini were found to be more specific toward mycobacteria, with their selectivity index in the range of 94-108.ConclusionThis is the first study to report the antimycobacterial activity of AuNPs, AgNPs, and Au-AgNPs synthesized from medicinal plants. Among these, Au-AgNPs from S. cumini showed profound efficiency, specificity, and selectivity to kill mycobacteria. These should be investigated further to develop novel TB nanoantibiotics.

Project description:Breast cancer poses a global threat with rising incidence and high mortality. Conventional treatments, including chemotherapy, radiation, surgery, and immunotherapy, have side effects, such as resistance issues and adverse effects due to genetic mutations. Meanwhile, noble metal nanoparticles (NPs) synthesized using environmentally friendly methods offer alternative treatments. Bimetallic gold (Au) and silver (Ag) NPs, using natural compounds like starch as stabilizers, enhance biomedical applications, including breast cancer therapies. In this work, the optical properties, stability, and particle size of colloidal bimetallic Ag/Au NPs were analyzed using UV-visible spectroscopy and ζ-potential measurements. The structural properties of the NPs were studied by powder X-ray diffraction (PXRD), while the morphology, chemical composition and particle size were determined using scanning transmission electron microscopy (STEM). The antitumor properties of the Ag/Au NPs were analyzed on human breast cancer cells (MCF-7) using the MTT viability method, reactive oxygen species (ROS) production, and genotoxicity assays. Peripheral blood mononuclear cells (PBMCs) were used as a reference of healthy cells. UV-vis spectroscopy and EDX mapping analysis confirmed the synthesis of bimetallic Ag/Au NPs. Localized surface plasmon resonance (LSPR) absorption bands shifted from 407 nm (Ag) to 524 nm (Au) based on the chemical composition of the NPs. The Ag/Au NPs showed cytocompatibility in PBMCs and a dose-dependent anticancer effect against MCF-7 cancer cells, as well as cell death dependent on ROS production was observed, particularly in NPs with atomic compositions of 50 and 75 at% Ag. This biological activity of the bimetallic NPs was associated with genotoxic damage of 20-24% greater than that observed in the monometallic counterparts. This study demonstrated the synthesis of mono- and bimetallic Ag/Au NPs using a rapid, reproducible and environmentally friendly method, with successful biomedical application against human breast cancer MCF-7 cells.

Project description:Background and aimBimetallic silver/gold nanosystems are expected to significantly improve therapeutic efficacy compared to their monometallic counterparts by maintaining the general biocompatibility of gold nanoparticles (AuNPs) while, at the same time, decreasing the relatively high toxicity of silver nanoparticles (AgNPs) toward healthy human cells. Thus, the aim of this research was to establish a highly reproducible one-pot green synthesis of colloidal AuNPs and bimetallic Ag/Au alloy nanoparticles (NPs; Ag/AuNPs) using starch as reducing and capping agent.MethodsThe optical properties, high reproducibility, stability and particle size distribution of the colloidal NPs were analyzed by ultraviolet (UV)-visible spectroscopy, dynamic light scattering (DLS) and ζ-potential. The presence of starch as capping agent was determined by Fourier transform infrared (FT-IR) spectroscopy. The structural properties were studied by X-ray diffraction (XRD). Transmission electron microscopy (TEM) imaging was done to determine the morphology and size of the nanostructures. The chemical composition of the nanomaterials was determined by energy-dispersive X-ray spectroscopy (EDS) and inductively coupled plasma mass spectrometry (ICP-MS) analysis. To further study the biomedical applications of the synthesized nanostructures, antibacterial studies against multidrug-resistant (MDR) Escherichia coli and methicillin-resistant Staphylococcus aureus (MRSA) were conducted. In addition, the NPs were added to the growth media of human dermal fibroblast (HDF) and human melanoma cells to show their cytocompatibility and cytotoxicity, respectively, over a 3-day experiment.ResultsUV-visible spectroscopy confirmed the highly reproducible green synthesis of colloidal AuNPs and Ag/AuNPs. The NPs showed a face-centered cubic crystal structure and an icosahedral shape with mean particle sizes of 28.5 and 9.7 nm for AuNPs and Ag/AuNPs, respectively. The antibacterial studies of the NPs against antibiotic-resistant bacterial strains presented a dose-dependent antimicrobial behavior. Furthermore, the NPs showed cytocompat-ibility towards HDF, but a dose-dependent anticancer effect was found when human melanoma cells were grown in presence of different NP concentrations for 72 hours.ConclusionIn this study, mono- and bimetallic NPs were synthesized for the first time using a highly reproducible, environmentally friendly, cost-effective and quick method and were successfully characterized and tested for several anti-infection and anticancer biomedical applications.

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An in situ SAXS investigation of the formation of silver nanoparticles and bimetallic silver-gold nanoparticles in controlled wet-chemical reduction synthesis.

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An <i>in situ</i> SAXS investigation of the formation of silver nanoparticles and bimetallic silver-gold nanoparticles in controlled wet-chemical reduction synthesis.

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