Highly efficient in vitro biosynthesis of silver nanoparticles using Lysinibacillus sphaericus MR-1 and their characterization

Abstract

Silver nanoparticles (AgNPs) have been widely used in diverse fields due to their superior properties. Currently the biosynthesis of AgNPs is in the limelight of modern nanotechnology because of its green properties. However, relatively low yield and inefficiency diminish the prospect of applying these biosynthesized AgNPs. In this work, a rapid mass AgNP biosynthesis method using the cell-free extract of a novel bacterial strain, Lysinibacillus sphaericus MR-1, which has been isolated from a chemical fertilizer plant, is reported. In addition, the optimum synthesis conditions of AgNPs were investigated. The optimum pH, temperature, dosage, and reaction time were 12, 70 °C, 20 mM AgNO₃, and 75 min, respectively. Finally, AgNPs were characterized by optical absorption spectroscopy, zeta potential and size distribution analysis, x-ray diffraction, electron microscopy, and energy-dispersive x-ray spectroscopy. The results revealed that these biosynthesized AgNPs were bimolecular covered, stable, well-dispersed face centered cubic (fcc) spherical crystalline particles with diameters in the range 5–20 nm. The advantages of this approach are its simplicity, high efficiency, and eco-friendly and cost-effective features.     

Medicinal plants mediated the green synthesis of silver nanoparticles and their biomedical applications

The alarming effect of antibiotic resistance prompted the search for alternative medicine to resolve the microbial resistance conflict. Over the last two decades, scientists have become increasingly interested in metallic nanoparticles to discover their new dimensions. Green nano synthesis is a rapidly expanding field of interest in nanotechnology due to its feasibility, low toxicity, eco‐friendly nature, and long‐term viability. Some plants have long been used in medicine because they contain a variety of bioactive compounds. Silver has long been known for its antibacterial properties. Silver nanoparticles have taken a special place among other metal nanoparticles. Silver nanotechnology has a big impact on medical applications like bio‐coating, novel antimicrobial agents, and drug delivery systems. This review aims to provide a comprehensive understanding of the pharmaceutical qualities of medicinal plants, as well as a convenient guideline for plant‐based silver nanoparticles and their antimicrobial activity.     

Converting ultrafine silver nanoclusters to monodisperse silver sulfide nanoparticles via a reversible phase transfer protocol

To achieve better control of the formation of silver sulfide (Ag₂S) nanoparticles, ultrasmall Ag nanoclusters protected by thiolate ligands (Ag₄₄(SR)₃₀ and Ag₁₆(GSH)₉) are used as precursors, which, via delicate chemistry, can be readily converted to monodisperse Ag₂S nanoparticles with controllable sizes (4–16 nm) and switchable solvent affinity (between aqueous and organic solvents). This new synthetic protocol makes use of the atomic monodispersity and rich surface chemistry of Ag nanoclusters and a novel two-phase protocol design, which results in a well-controlled reaction environment for the formation of Ag₂S nanoparticles.

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Preparation and characterisation of ciprofloxacin‐loaded silver nanoparticles for drug delivery

Silver nanoparticles (AgNPs) have shown potential applications in drug delivery. In this study, the AgNPs was prepared from silver nitrate in the presence of alginate as a capping agent. The ciprofloxacin (Cipro) was loaded on the surface of AgNPs to produce Cipro‐AgNPs nanocomposite. The characteristics of the Cipro‐AgNPs nanocomposite were studied by X‐ray diffraction (XRD), UV–Vis, transmission electron microscopy (TEM), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), Fourier‐transform infra‐red analysis (FT‐IR) and zeta potential analyses. The XRD of AgNPs and Cipro‐AgNPs nanocomposite data showed that both have a crystalline structure in nature. The FT‐IR data indicate that the AgNPs have been wrapped by the alginate and loaded with the Cipro drug. The TEM image showed that the Cipro‐AgNPs nanocomposites have an average size of 96 nm with a spherical shape. The SEM image for AgNPs and Cipro‐AgNPs nanocomposites confirmed the needle‐lumpy shape. The zeta potential for Cipro‐AgNPs nanocomposites exhibited a positive charge with a value of 6.5 mV. The TGA for Cipro‐AgNPs nanocomposites showed loss of 79.7% in total mass compared to 57.6% for AgNPs which is due to the Cipro loaded in the AgNPs. The release of Cipro from Cipro‐AgNPs nanocomposites showed slow release properties which reached 98% release within 750 min, and followed the Hixson–Crowell kinetic model. In addition, the toxicity of AgNPs and Cipro‐AgNPs nanocomposites was evaluated using normal (3T3) cell line. The present work suggests that Cipro‐AgNPs are suitable for drug delivery.     

Eco-friendly green synthesis of silver nanoparticles and their potential applications as antioxidant and anticancer agents

Abstract

Eco-friendly green synthesis of nanoparticles using medicinal plants gained immense importance due to its potential therapeutic uses. In the current study, silver nanoparticles (AgNPs) were synthesized using water extract of Jurinea dolomiaea leaf and root at room temperature. MTT assay was used to study anticancer potential of AgNPs against cervical cancer cell line (HeLa), breast cancer cell lines (MCF-7), and mouse embryonic fibroblast (NIH-3 T3) cell line for toxicity evaluation. The antioxidant potential was evaluated using stable DPPH radicals. In addition, the apoptotic nuclear changes prompted by AgNPs in more susceptible HeLa cells were observed using fluorescence microscope through DAPI and PI staining. Physiochemical properties of biosynthesized AgNPs were characterized using various techniques. AgNPs were formed in very short time and UV–vis spectra showed characteristic absorption peak of AgNPs. SEM and TEM showed spherical shape of AgNPs and XRD revealed their crystalline nature. EDX analysis revealed high percentage of silver in green synthesized AgNPs. FTIR analysis indicated involvement of secondary metabolites in fabrication of AgNPs. In vitro cytotoxic and antioxidant study revealed that herb and biosynthesized AgNPs exhibited significant dose-dependent and time-dependent anticancer and antioxidant potential. Furthermore, study on normal cell line and microscopic analysis of apoptosis revealed that AgNPs exhibited good safety profile as compared to cisplatin and induces significant apoptosis effect. Based on the current findings, it is strongly believe that use of J. dolomiaea offers large scale production of biocompatible AgNPs that can be used as alternative anticancer agents against cancer cell lines tested.     

Synthesis and characterization of silver nanoparticles and their antimicrobial efficacy

An efficient protocol for synthesis of silver nanoparticles (AgNPs) using the combination of aqueous extract of Tinospora cordifolia leaves and 5 mM silver nitrate (AgNO₃) solution was developed. This study revealed that bioactive compounds present in the extract function as stabilizing and capping agent for AgNPs. Scanning electron microscope and transmission electron microscope studies confirm the structure and surface morphology of the AgNPs. The size of synthesized AgNPs was in the range of 30–50 nm having spherical morphology. The crystalline nature of NPs was defined by the X-ray diffraction pattern. The AgNPs were found to be toxic against pathogenic bacteria such as Escherichia coli (ATCC 25922), Pseudomonas aeruginosa (ATCC 27853), and Staphylococcus aureus (ATCC 29213) and against plant pathogenic fungi Fusarium oxysporum (MTCC 8608) and Sclerotinia sclerotiorum (MTCC 8785). The use of AgNPs as antibacterial and antifungal agent is advantageous over other methods for control of pathogenic microorganisms, and it can be of great importance in developing novel drugs for curing many lethal diseases.     

Highly efficient in vitro biosynthesis of silver nanoparticles using Lysinibacillus sphaericus MR-1 and their characterization

Silver nanoparticles (AgNPs) have been widely used in diverse fields due to their superior properties. Currently the biosynthesis of AgNPs is in the limelight of modern nanotechnology because of its green properties. However, relatively low yield and inefficiency diminish the prospect of applying these biosynthesized AgNPs. In this work, a rapid mass AgNP biosynthesis method using the cell-free extract of a novel bacterial strain, Lysinibacillus sphaericus MR-1, which has been isolated from a chemical fertilizer plant, is reported. In addition, the optimum synthesis conditions of AgNPs were investigated. The optimum pH, temperature, dosage, and reaction time were 12, 70 °C, 20 mM AgNO₃, and 75 min, respectively. Finally, AgNPs were characterized by optical absorption spectroscopy, zeta potential and size distribution analysis, x-ray diffraction, electron microscopy, and energy-dispersive x-ray spectroscopy. The results revealed that these biosynthesized AgNPs were bimolecular covered, stable, well-dispersed face centered cubic (fcc) spherical crystalline particles with diameters in the range 5–20 nm. The advantages of this approach are its simplicity, high efficiency, and eco-friendly and cost-effective features.     

Synthesis of silver nanoparticles by chemical and biological methods and their antimicrobial properties

Biogenic synthesis of nanoparticles offers an attractive alternate to chemical synthesis methods. Various hazard free, eco-friendly methods of synthesis of silver nanoparticles are in operation. In chemical reduction methods, the reducing agent is a chemical solution, whereas in biological ones, the collection of enzymes, especially nitrate reductase, plays this role. The highest antibacterial activity of silver nanoparticles synthesised by chemical and biological methods was found in Staphylococcus aureus and Escherichia coli. The paper aims to discuss some fundamental issues about non-biological methods and benefits about biological methods for silver nanoparticles synthesis and their antibacterial studies.     

Highly size- and shape-controlled synthesis of silver nanoparticles via a templated Tollens reaction

A mild, facile one-step synthetic strategy for the preparation of size- and shape-controlled silver nanoparticles (AgNPs) is presented. The high degree of size- and shape-control of these AgNPs is achieved by the use of triazole sugar ligands scaffolded by a central resorcinol ether core. Both the triazoles and the resorcinol ether core mediate the nucleation, growth, and passivation phases of the preparation of AgNP in the presence of the Tollens reagent as the silver source. Kinetic and (1)H NMR titration data is presented describing the nature of the interactions between the Tollens reagent and these ligands.     

Green synthesis of silver nanoparticles using Cyathea nilgirensis Holttum and their cytotoxic and phytotoxic potentials

The present study aimed at synthesizing silver nanoparticles (AgNPs) from the aqueous extract of C. nilgirensis and their biopotential using cytotoxicity and phytotoxicity. On mixing the aqueous extract with 1?mM AgNO₃ solution, the color changes from pale yellow to yellowish brown color. The absorption spectra of yellowish brown nanoparticle showed a plasmon absorption band with a maximum of 3.806 and 1.028 abs in 311 and 440?nm, respectively. The Fourier transform infrared spectroscopy (FTIR) spectra confirmed that phenolic compounds have stronger ability to bind with metal, indicating that phenolics could possibly form metal nanoparticles to prevent agglomeration and thereby stabilize the medium. The size of AgNP is found to be in the 45.0–74.0?nm range. The Energy-dispersive X-ray (EDX) spectra analysis revealed the presence of a strong Ag peak. The results indicated that C. nilgirensis aqueous extract was found efficient for the synthesis of AgNPs.     

Antibacterial mechanism of biogenic silver nanoparticles of Lactobacillus acidophilus

The development of reliable, eco-friendly protocol for the synthesis of nanomaterials is a challenging issue in the current nanotechnology. In the present study, we reported an environmentally benign and rapid method for biogenesis of silver nanoparticles using Gram-positive bacterium Lactobacillus acidophilus which acts both as reducing and capping agent. It was observed that the culture filtrate reduced silver ions into silver nanoparticles within 24 hrs of reaction time under room temperature. The UV–Vis spectrum shows the absorbance maximum at 434 nm, which is a characteristic of surface plasmon resonance of silver. X-ray diffraction analysis showed that the nanoparticles were of face-centred cubic crystalline structure. The presence of stable spherical-shaped silver nanoparticles in the size range of 4–50 nm was determined using the transmission electron microscopy analysis. Further, these nanoparticles showed effective antibacterial activity towards Klebsiella pneumoniae. The mechanism of the silver nanoparticle bactericidal activity is discussed in terms of its interaction with the cell membrane of bacteria by causing cytolysis and leakage of proteins and carbohydrates.     

Green synthesis of silver nanoparticles from purple acid phosphatase apoenzyme isolated from a new source Limonia acidissima

Green synthesis of nanoparticles is regarded as a safe and non-toxic process whereas conventional synthesis using chemical methods produces toxic substance. This study provides a novel insight for enzymatic synthesis method of silver nanoparticles using purple acid phosphatase, isolated from Limonia acidissima (wood apple) as a new source and used in the synthesis of silver nanoparticles. Stable silver nanoparticles were produced by sonochemical method using apoenzyme as a stabilising and capping agent and were characterised by various physicochemical techniques like UV–Visible spectroscopy, Fourier-transform infrared, X-ray diffraction and transmission electron microscopy. X-ray study shows that nanoparticles are composed of silver and silver oxide. The synthesised nanoparticles exhibited excellent antimicrobial activity against Escherichia coli, Pseudomonas aeruginosa and Staphylococcus aureus.     

Differential interaction of silver nanoparticles with cysteine

Understanding the characteristics of cysteine on a solid surface is an important issue in protein study and amino acid analysis. Therefore, cysteine was selected as a model biomolecule to study the interaction with plasmonic silver nanoparticles. In this study, we report the differential interaction of cysteine with silver nanoparticles synthesised by Lee and Meisel (using citrate as reductant), and modified Creighton (citrate and borohydride as reductant) methods. In Lee and Meisel's method, the red-shifting of silver plasmon resonance in the UV–vis spectra and the aggregation of the particles occurred owing to a decrease in stability of silver nanoparticles upon interaction with cysteine. In contrast, the other method did not cause any aggregation or significant spectral changes. The differential behaviour may be due to surface chemical changes on cysteine with pH, which plays a major role in the nanoparticle-biomolecule interaction. The synthesis of silver nanoparticles applying two sol gel methods followed by interactions with cysteine induces different functionalities on the nanoparticles, which may find specific applications in bio-sensing and drug delivery.     

Biosynthesis and structural characterization of silver nanoparticles from bacterial isolates

This study aimed to develop a green process for biosynthesis of silver nanomaterials by some Egyptian bacterial isolates. This target was achieved by screening an in-house culture collection consists of 300 bacterial isolates for silver nanoparticle formation. Through screening process, it was observed that strains belonging to Escherichia coli (S30, S78), Bacillus megaterium (S52), Acinetobacter sp. (S7) and Stenotrophomonas maltophilia (S54) were potential candidates for synthesis of silver nanoparticles. The extracellular production of silver nanoparticles by positive isolates was investigated by UV-Vis spectroscopy, X-ray diffraction (XRD), transmission electron microscope (TEM), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). The results demonstrated that UV-visible spectrum of the aqueous medium containing silver ion showed a peak at 420 nm corresponding to the plasmon absorbance of silver nanoparticles. Scanning electron microscopy micrograph showed formation of silver nanoparticles in the range of 15-50 nm. XRD-spectrum of the silver nanoparticles exhibited 2θ values corresponding to the silver nanocrystal that produce in hexagonal and cubic crystal configurations with different plane of orientation. In addition, the signals of the silver atoms were observed by EDS-spectrum analysis that confirms the presence of silver nanoparticles (AgNPs) in all positive bacterial isolates.     

Formation process of silver nanoparticles in DTAB/SDBS/PVP aqueous solution

Silver nanoparticles were prepared from the nitrate silver solution in dodecyl trimethyl ammonium bromide (DTAB)/sodium dodecylbenzenesulfonate (SDBS)/polyvinyl pyrrolidone (PVP) complex solution with hydrazine as the reductant. Scanning electron microscopy (SEM), X-ray diffraction (XRD) and UV–Vis spectroscopic analysis were conducted to investigate the role of anionic–cationic surfactants on the growth process of silver particles. The results showed that, before the formation of spherical silver nanoparticles, the cube and then tetrakaidecahedrons of AgBr were initially formed. It is concluded that the selective interaction of bow-like electric double-layer structure of anionic–cationic surfactants with certain crystallographic planes of crystals dominated the morphology evolvement of the reaction products. In addition; the PVP coverage finally encouraged the formation of well-dispersed spherical silver nanoparticles.     

Influences of gold and silver nanoparticles in loop-mediated isothermal amplification reactions

Loop-mediated isothermal amplification (LAMP) performed with protein DNA polymerase Bst and DNA chains was influenced by nanoparticles in different ways. The effects of different concentrations of gold nanoparticles (AuNPs) with diameters 10 and 20?nm and silver nanoparticles (AgNPs) 1–10?nm in diameter on the amplification of the pR72H gene of Vibrio parahaemolyticus were investigated. AuNPs with a diameter of 10?nm in 0.6–60?nM concentration accelerated initiation of the LAMP reaction, 3?nM AuNPs reduced the reaction time by about 10?min, whereas 20?nm AuNPs did not, although neither size increased the yield after 60?min. AgNPs inhibited the LAMP reaction both in speed and yield at concentrations of 0.6–60?nM; the yield of amplification was reduced by 50% and 80% for 12 and 60?nM, respectively, after reaction for 1?h. This indicated that strong bactericidal effects of silver are also observed in its nanoparticles. The molecular mechanism of AuNPs and AgNPs in LAMP needs to be explored further, although their size-related electronic, magnetic and optical properties, as well as their ability to affect protein denaturation, or hydrophilic/hydrophobic effects may be involved.     

化学还原法制备纳米银粒子及其表征

采用化学还原法, 通过一系列条件实验,借助紫外-可见分光光度计(UV-vis)得到最佳实验条件,在最佳实验条件下制得紫黑色溶胶,在40℃下真空干燥3h,获纳米银粉.制备的纳米银粉用X射线衍射仪(XRD)和透射电镜(TEM)分析表明,其粒径大小分布范围窄,形状为单一球形,平均粒径为18nm.     

Controllable assembly of silver nanoparticles induced by femtosecond laser direct writing

We report controllable assembly of silver nanoparticles (Ag NPs) for patterning of silver microstructures. The assembly is induced by femtosecond laser direct writing (FsLDW). A tightly focused femtosecond laser beam is capable of trapping and driving Ag NPs to form desired micropatterns with a high resolution of ∼190 nm. Taking advantage of the ‘direct writing’ feature, three microelectrodes have been integrated with a microfluidic chip; two silver-based microdevices including a microheater and a catalytic reactor have been fabricated inside a microfluidic channel for chip functionalization. The FsLDW-induced programmable assembly of Ag NPs may open up a new way to the designable patterning of silver microstructures toward flexible fabrication and integration of functional devices.     

Controllable assembly of silver nanoparticles induced by femtosecond laser direct writing

Abstract

We report controllable assembly of silver nanoparticles (Ag NPs) for patterning of silver microstructures. The assembly is induced by femtosecond laser direct writing (FsLDW). A tightly focused femtosecond laser beam is capable of trapping and driving Ag NPs to form desired micropatterns with a high resolution of ～190 nm. Taking advantage of the ‘direct writing’ feature, three microelectrodes have been integrated with a microfluidic chip; two silver-based microdevices including a microheater and a catalytic reactor have been fabricated inside a microfluidic channel for chip functionalization. The FsLDW-induced programmable assembly of Ag NPs may open up a new way to the designable patterning of silver microstructures toward flexible fabrication and integration of functional devices.