Biogenic synthesis of multidimensional gold nanoparticles assisted by Streptomyces hygroscopicus and its electrochemical and antibacterial properties

Bioactive Streptomycetes: A Powerful Tool to Synthesize Diverse Nanoparticles With Multifarious Properties

Nanobiotechnology has gained significant attention due to its capacity to generate substantial benefits through the integration of microbial biotechnology and nanotechnology. Among microbial organisms, Actinomycetes, particularly the prominent genus Streptomycetes, have garnered attention for their prolific production of antibiotics. Streptomycetes have emerged as pivotal contributors to the discovery of a substantial number of antibiotics and play a dominant role in combating infectious diseases on a global scale. Despite the noteworthy progress achieved through the development and utilization of antibiotics to combat infectious pathogens, the prevalence of infectious diseases remains a prominent cause of mortality worldwide, particularly among the elderly and children. The emergence of antibiotic resistance among pathogens has diminished the efficacy of antibiotics in recent decades. Nevertheless, Streptomycetes continue to demonstrate their potential by producing bioactive metabolites for the synthesis of nanoparticles. Streptomycetes are instrumental in producing nanoparticles with diverse bioactive characteristics, including antiviral, antibacterial, antifungal, antioxidant, and antitumor properties. Biologically synthesized nanoparticles have exhibited a meaningful reduction in the impact of antibiotic resistance, providing resources for the development of new and effective drugs. This review succinctly outlines the significant applications of Streptomycetes as a crucial element in nanoparticle synthesis, showcasing their potential for diverse and enhanced beneficial applications.

Streptomyces monashensis MSK03-mediated synthesis of gold nanoparticles: characterization and antibacterial activity

Nanotechnology is a cutting-edge field with diverse applications, particularly in the utilization of gold nanoparticles (AuNPs) due to their stability and biocompatibility. AuNPs serve as pivotal components in medical applications, with a specific emphasis on their significant antibacterial efficacy. This study focuses on synthesizing AuNPs using the cell-free supernatant of Streptomyces monashensis MSK03, isolated from terrestrial soil in Thailand. The biosynthesis process involved utilizing the cell-free supernatant of S. monashensis MSK03 and hydrogen tetrachloroauric acid (HAuCl4) under controlled conditions of 37 °C and 200 rpm agitation. Characterization studies revealed spherical AuNPs with sizes ranging from 7.1 to 40.0 nm (average size: 23.2 ± 10.7 nm), as confirmed by TEM. UV-Vis spectroscopy indicated a localized surface plasmon resonance (LSPR) band at 545 nm, while XRD analysis confirmed a crystalline structure with characteristics of cubic lattice surfaces. The capping molecules on the surface of AuNPs carry a negative charge, indicated by a Zeta potential of -26.35 mV, and FTIR analysis identified functional groups involved in reduction and stabilization. XANES spectra further confirmed the successful reduction of Au3+ to Au0. Moreover, the synthesized AuNPs demonstrated antibacterial activity against drug-resistant strains of Pseudomonas aeruginosa and Acinetobacter baumannii. Interestingly, the AuNPs showed non-toxicity to Vero cell lines. These significant antibacterial properties of the produced nanoparticles mean they hold great promise as new antimicrobial treatments for tackling the increasing issue of antibiotic resistance.

Utilization of aqueous broccoli florets extract for green synthesis and characterization of silver nanoparticles, with potential biological applications

The process of creating nanoparticles using chemicals is not eco-friendly. However, a more environmentally conscious approach known as green chemistry, which involves using vegetable-mediated nanoparticle production, combines nanotechnology with biotechnology. In this study, the researchers aimed to assess the effectiveness of the green chemistry technique in producing silver nanoparticles using an liquid extract from broccoli florets (Brassica oleracea) under ideal environment. The successful production of silver nanoparticles was achieved through silver nitrate (AgNO₃) biological reduction with the help of an aqueous broccoli florets extract at a slightly acidic pH of 6-7. The silver nanoparticles occurrence was shown by a change of color that moved from colorless to reddish-brown. To characterize the green-produced nanoparticles, various analytical techniques such as Ultraviolet-Visible Spectroscopy (UV-VIS), Fourier Transform Infrared Spectroscopy (FT-IR), X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), and Energy-Dispersive X-ray Spectroscopy (EDAX) were employed. The antioxidant properties of the formed silver nanoparticles (AgNPs) were examined in vitro using the 2,2-diphenyl-1-picrylhydrazyl (DPPH) and Ferric Reducing Antioxidant Power (FRAP) tests. Additionally, the antibacterial properties of AgNPs against various pathogenic bacteria was evaluated. The reduction procedure was easy and simple manageable, with UV-Vis spectroscopy indicating the surface plasmon resonance (SPR) presence at 425 nm. FTIR was utilized to identify active chemical groups in the biomass before and after reduction. SEM and X-ray diffraction analyses indicated that the silver nanoparticles had an average the size of individual particles of 33 nm and exhibited a face-centered cubic (FCC) structure. EDAX analysis confirmed the occurrence of elemental silver in the nanoparticles. The study demonstrated that the biosynthesis of AgNPs led to significant variations in antioxidant activity, which was dose-dependent and showed a similar pattern to the testing of the scarfing action of the ascorbic acid against free radicals using DPPH and FRAP. The AgNPs also dispalyed firm deep-spectrum antibacterial action observed against the tested pathogenic bacteria, outperforming certain medications. Interestingly, the silver nanoparticles remained stable at ambient temperature for 25 days without precipitation, retaining their antioxidant and antibacterial properties. In conclusion, the research findings suggest that an aqueous extract of fresh broccoli florets can serve as a viable and environmentally friendly method for producing stable silver nanoparticles with beneficial antioxidant and antibacterial characteristics.

Statistical optimization and characterization of monodisperse and stable biogenic gold nanoparticle synthesis using Streptomyces sp. M137-2

Microbial synthesis of gold nanoparticles (AuNPs), which are used in various forms with different properties in medicine, as a renewable bioresource has become increasingly important in recent years. In this study, statistical optimization of stable and monodispersed AuNPs synthesis was performed using a cell-free fermentation broth of Streptomyces sp. M137-2 and AuNPs were characterized, and their cytotoxicity was determined. The three factors determined as pH, gold salt (HAuCl₄) concentration, and incubation time, which are effective in the extracellular synthesis of biogenic AuNPs, were optimized by Central Composite Design (CCD) and then UV-Vis Spectroscopy, Dynamic Light Scattering (DLS), X-Ray Diffraction (XRD), Scanning Electron Microscope (SEM), Scanning Transmission Electron Microscope (STEM), size distribution, Fourier-Transform Infrared (FT-IR) Spectroscopy, X-Ray Photoelectron Spectrophotometer (XPS) and stability analyzes of AuNPs were carried out. Optimum values of the factors were determined as pH 8, 10^- 3 M HAuCl₄, and 72 h incubation using Response Surface Methodology (RSM). Almost spherical AuNPs with 20-25 nm protein corona on the surface, 40-50 nm in size, monodisperse, and highly stable form were synthesized. Biogenic AuNPs were confirmed from characteristic diffraction peaks in the XRD pattern, UV-vis peak centred at 541 nm. The FT-IR results confirmed the role of Streptomyces sp. M137-2 metabolites in the reduction and stabilization of AuNPs. The cytotoxicity results also showed that AuNPs obtained using Streptomyces sp. can be used safely in medicine. This is the first report to perform statistical optimization of size-dependent biogenic AuNPs synthesis using a microorganism.

Molecular and therapeutic insights of rapamycin: a multi-faceted drug from Streptomyces hygroscopicus

The advancement in pharmaceutical research has led to the discovery and development of new combinatorial life-saving drugs. Rapamycin is a macrolide compound produced from Streptomyces hygroscopicus. Rapamycin and its derivatives are one of the promising sources of drug with broad spectrum applications in the medical field. In recent times, rapamycin has gained significant attention as of its activity against cytokine storm in COVID-19 patients. Rapamycin and its derivatives have more potency when compared to other prevailing drugs. Initially, it has been used exclusively as an anti-fungal drug. Currently rapamycin has been widely used as an immunosuppressant. Rapamycin is a multifaceted drug; it has anti-cancer, anti-viral and anti-aging potentials. Rapamycin has its specific action on mTOR signaling pathway. mTOR has been identified as a key regulator of different pathways. There will be an increased demand for rapamycin, because it has lesser adverse effects when compared to steroids. Currently researchers are focused on the production of effective rapamycin derivatives to combat the growing demand of this wonder drug. The main focus of the current review is to explore the origin, development, molecular mechanistic action, and the current therapeutic aspects of rapamycin. Also, this review article revealed the potential of rapamycin and the progress of rapamycin research. This helps in understanding the exact potency of the drug and could facilitate further studies that could fill in the existing knowledge gaps. The study also gathers significant data pertaining to the gene clusters and biosynthetic pathways involved in the synthesis and production of this multi-faceted drug. In addition, an insight into the mechanism of action of the drug and important derivatives of rapamycin has been expounded. The fillings of the current review, aids in understanding the underlying molecular mechanism, strain improvement, optimization and production of rapamycin derivatives.

Antibiofilm and cytotoxic potential of extracellular biosynthesized gold nanoparticles using actinobacteria Amycolatopsis sp. KMN

This study intends to biosynthesize gold nanoparticles (AuNPs) using Amycolatopsis sp. KMN and to investigate its potential antibiofilm, cytotoxic and antioxidant activities. The physicochemical characterization of biosynthesize AuNPs was identified by UV-Visible, energy-dispersive X-ray, and Fourier transform infrared spectroscopy, as well as high-resolution transmission electron microscopy, X-ray diffraction, zeta potential, and dynamic light scattering methods. Crystal violet assay and scanning electron microscopy showed that the AuNPs with a particle size of 44.4 nm have a strong antibiofilm activity (at 750 µg/ml concentration) against bacteria strains viz Staphylococcus aureus ATCC 29213, Escherichia coli ATCC 25922, and Pseudomonas aeruginosa ATCC 27853. The result also demonstrated strong cytotoxic activity against two cell lines, MCF-7 and HT-29. The MTT test result displayed that over a period of 48 hr, the IC₅₀ of AuNPs was 600 and 300 µg/ml for MCF-7 and HT-29 cell lines, respectively. The IC₅₀ of AuNPs against DPPH was 46.87 µg/ml. This is the first report that examines Amycolatopsis sp. strain KMN-mediated synthesis of AuNPs is rapid and in situ with antibiofilm and cytotoxicity activities. Moreover, it has the potential for an effective antibiofilm and cytotoxic activity that could be used in future therapeutic applications.

Biosynthesis of silver nanoparticles by Nocardiopsis sp.-MW279108 and its antimicrobial activity

The utilization of microorganisms like bacteria in the biological synthesis of silver nanoparticles (AgNPs) has attracted widespread attention due to their ability to synthesize different shape sizes, states, and morphology nanoparticles. In the current study, the green synthesis of AgNPs by Nocardiopsis sp. 16S ribosomal RNA analysis was used to characterize the Nocardiopsis sp. The synthesized AgNPs were characterized through multi-instrument platforms such as transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), UV-Vis spectroscopy, scanning electron microscope (SEM), and X-ray diffraction analysis (XRD). The antimicrobial activity of the synthesized AgNPs was determined by the agar plate diffusion method. The UV-Vis absorbance analysis of the synthesized AgNPs has a significant absorbance at 384 nm, confirming the AgNPs' surface plasmon resonance. The SEM and TEM characterizations indicate that the particle size ranges from 2 to 10 nm and is spherical. Additionally, the FTIR spectra revealed bands from 476 to 3819cm^-1 , respectively. The XRD planes study pronounced strong bands ranging are between 111 and 311 corresponding to cubic face-center of the silver. Also, the antimicrobial activity of AgNPs indicated the biogenic AgNPs could control the growth of the clinical isolates. The AgNPs produced by Nocardiopsis sp. supernatant could be used in different nanomedicinal applications.

Diatoms decorated with gold nanoparticles by In-situ and Ex-situ methods for in vitro gentamicin release

The use of natural diatoms is currently a topic of interest for therapeutic applications due to its facilities, low cost, and biocompatibility. Here, we report the chemical modification of diatoms Aulacoseria genus microalgae-derived biosilica from Guayllabamba - Ecuador decorated with gold nanoparticles by In-situ and Ex-situ methods to study the in vitro gentamicin loading and release properties in simulated body fluid (SBF). Successful decoration of the diatoms and loaded with gentamicin was confirmed using Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), Raman spectroscopy and Fluorescence Microscopy. We follow the In-vitro drug release by using Ultraviolet-Visible Spectroscopy (UV-vis). Our results revealed that diatoms decorated with gold nanoparticles using the Ex-situ method (Au/CTAB-Diatom) showed a faster release reaching a maximum of 93% in 10 days and a lower loading rate, while the samples decorated by the In-situ method presented longer and slower release behavior. Fluorescence properties were enhanced after the gentamicin loaded. The advantage of this work is the control of the structural and optical properties of diatoms decorated with gold nanoparticles for the gentamicin drug delivery.

Antibacterial activity of ultrathin platinum islands on flat gold against Escherichia coli

Nanoporous Au exhibits high antibacterial activity (AA) without releasing reactive oxygen species or metal ions, instead its AA depends on the work function (WF) because cell walls are affected by peculiar electronic states at the surface. Based on this mechanism, a flat surface without nanostructure should show high AA if the WF of the surface is suitably tuned. To verify this, ultrathin Pt islands with high WF was fabricated on flat Au by underpotential deposition (UPD) of copper and subsequent redox replacement with Pt, and the AA of the Pt/Au substrate on Escherichia coli was evaluated. The Pt/Au substrate showed higher AA than Pt and Au surfaces, and a positive relationship between AA and WF was demonstrated. In addition, first principles calculations were performed to investigate the mechanism for the high WF of the Pt/Au substrate. The findings suggest that the high WF of the Pt/Au substrate is at least partly due to charge transfer from Au to Pt.

Novel marine Nocardiopsis dassonvillei-DS013 mediated silver nanoparticles characterization and its bactericidal potential against clinical isolates

The sediment marine samples were obtained from several places along the coastline of the Tuticorin shoreline, Tamil Nadu, India were separated for the presence of bioactive compound producing actinobacteria. The actinobacterial strain was subjected to 16Sr RNA sequence cluster analysis and identified as Nocardiopsis dassonvillei- DS013 NCBI accession number: KM098151. Bacterial mediated synthesis of nanoparticles gaining research attention owing its wide applications in nonmedical biotechnology. In the current study, a single step eco-friendly silver nanoparticles (AgNPs) were synthesized from novel actinobacteria Nocardiopsis dassonvillei- DS013 has been attempted. The actinobacterial mediated silver nanoparticles were characterized by TEM, UV-Visible, XRD, FT-IR spectroscopy. The initial detection of AgNPs was identified using UV-Vis spectrum and confirmed by the appearance of absorbance peak at 408 nm. A Fourier transform infrared spectroscopy (FT-IR) result reveals the presence of protein component in the culture supernatant may act as protecting agents. The XRD pattern indicated that the typical peaks reveal the presence of nanoparticles. The TEM morphology confirms the formation of circular and non uniform distributions of AgNPs with the size range from 30 to 80 nm. The antibacterial activity of both isolated actinobacterial (IA) and silver nanoparticles mediated actinobacterial (SNA) of Nocardiopsis dassonvillei- DS013 were done by well diffusion method against selected clinical isolates of bacteria, namely Escherichia coli, Enterococcus sp., Pseudomonas sp., Klebsiella sp., Proteus sp., Shigella sp., Bacillus subtilis, and Streptococcus sp. When compared to isolated actinobacteria, the SNA shows the better antibacterial activity against clinical isolates.

Effect of NaOH concentration on antibacterial activities of Cu nanoparticles and the antibacterial mechanism

A series of Cu nanoparticles (NPs) have been prepared by a facile hydrothermal method at 180 °C using different concentrations of NaOH solutions and characterized by XRD, SEM, TEM and FT-IR spectra. Their antibacterial activities were assessed by means of Gram-positive S. aureus and Gram-negative E. coli bacteria, where various dosages (3, 5, 7, 10 mg) of the antibacterial agents were applied, and compared with that of the commercial CuSO₄ salt. The antibacterial mechanism was explored based on series of control experiments. The results show that the NaOH concentration affects the crystallinity, crystal size and surface hydroxyl content of the Cu NPs, which significantly influence the antibacterial activities. Compared to the commercial CuSO₄ salt, the four Cu samples prepared using no <4 mol L^-1 of NaOH display excellent antibacterial activities with low concentrations of copper leachates, which is great beneficial to the practical applications. The experimental results support that the highly reactive and soluble copper species in the antibacterial system of the Cu NPs is a Cu (II)-peptide complex, but not free Cu²⁺ ions.

Toxicological Behavior of Gold Nanoparticles on Various Models: Influence of Physicochemical Properties and Other Factors

Potential applications of gold nanoparticles in biomedicine have increasingly been reported on account of the ease of synthesis, bioinert characteristics, optical properties, chemical stability, high biocompatibility, and specificity. The safety of these particles remains a great concern, as there are differences among toxicity study protocols used. This article focuses on integrating results of research on the toxicological behavior of gold nanoparticles. This can be influenced by the physicochemical properties, including size, shape, surface charge, and other factors, such as methods used in the synthesis of gold nanoparticles, models used, dose, in vivo route of administration, and interference of gold nanoparticles with in vitro toxicity assay systems. Several researchers have reported toxicological studies with regard to gold nanoparticles, using various in vitro, in vivo, and in ovo models. The conflicting results concerning the toxicity of gold nanoparticles should thus be addressed to justify the safe use of gold nanoparticles in biomedicine.

Biological synthesis of metallic nanoparticles (MNPs) by plants and microbes: their cellular uptake, biocompatibility, and biomedical applications

Metallic nanoparticles (MNPs) with their diverse physical and chemical properties have been applied in various biomedical domains. The increasing demand for MNPs has attracted researchers to develop straightforward, inexpensive, simple, and eco-friendly processes for the enhanced production of MNPs. To discover new biomedical applications first requires knowledge of the interactions of MNPs with target cells. This review focuses on plant and microbial synthesis of biological MNPs, their cellular uptake, biocompatibility, any biological consequences such as cytotoxicity, and biomedical applications. We highlighted the involvement of biomolecules in capping and stabilization of MNPs and the effect of physicochemical parameters particularly the pH on the synthesis of MNPs. Recently achieved milestones to understand the role of synthetic biology (SynBiol) in the synthesis of tailored MNPs are also discussed.

Antimicrobial mechanisms due to hyperpolarisation induced by nanoporous Au

Nanomaterials such as nanoparticles exhibit remarkable antimicrobial activities. Nanoparticles directly disturb the cell membrane or cytoplasmic proteins because they pass through the cell wall. Nanoporous Au (NPG) is another antimicrobial nanomaterial, which cannot pass through the cell wall of bacteria but can still kill bacteria, utilising interactions between the surface of NPG and cell wall of bacteria. The origins of antimicrobial activities without direct interactions are unknown. It is necessary to elucidate these mechanisms to ensure safe usage. Here we show that the antimicrobial mechanism of NPG consists of two interactions: between the surface of NPG and cell wall, and between the cell wall and cell membrane. Fluorescent experiments showed that the cell wall was negatively hyperpolarised by NPG, and molecular dynamics simulations and first-principles calculations suggested that the hyperpolarisation of the cell wall leads to delicate structural changes in the membrane proteins, rendering them bactericidal. Thus, the hyperpolarisation induced by NPG plays a critical role in both interactions. The combination of molecular dynamics simulations and first-principles calculations allows a deeper understanding of the interactions between metallic surfaces and biomolecules, because charge transfer and exchange interactions are calculated exactly.

Nanotechnology, Metal Nanoparticles, and Biomedical Applications of Nanotechnology

Nanotechnology has emerged as an important field of modern scientific research due to its diverse range of applications in the area of electronics, material sciences, biomedical engineering, and medicines at nano levels such as healthcare, cosmetics, food and feed, environmental health, optics, biomedical sciences, chemical industries, drug-gene delivery, energy science, optoelectronics, catalysis, reprography, single electron transistors, light emitters, nonlinear optical devices, and photoelectrochemical applications and other applications. Due to these immense applications of nanotechnology in biomedical science, it has became possible to design the pharmaceuticals in such a way that they could directly treat diseased cells like cancer and make microscopic repairs in hard-to-operate-on areas of the body. The nanomachines have been designed to clean up toxins or oil spills, recycle all garbage, eliminate landfills, etc. The chapter summarizes the present and future applications of nanotechnology for human welfare but needs further study in catalysis, optical devices, sensor technology, cancer treatment, and drug delivery systems.

Extracellular synthesis of gold bionanoparticles by Nocardiopsis sp. and evaluation of its antimicrobial, antioxidant and cytotoxic activities

Advancement of biological process for the synthesis of bionanoparticles is evolving into a key area of research in nanotechnology. The present study deals with the biosynthesis, characterization of gold bionanoparticles by Nocardiopsis sp. MBRC-48 and evaluation of their antimicrobial, antioxidant and cytotoxic activities. The gold bionanoparticles obtained were characterized by UV-visible spectroscopy, X-ray diffraction analysis, Fourier transform infrared spectroscopy, field emission scanning electron microscopy, energy dispersive X-ray analysis and transmission electron microscopy (TEM). The synthesized gold bionanoparticles were spherical in shape with an average of 11.57 ± 1.24 nm as determined by TEM and dynamic light scattering (DLS) particle size analyzer, respectively. The biosynthesized gold nanoparticles exhibited good antimicrobial activity against pathogenic microorganisms. It showed strong antioxidant activity as well as cytotoxicity against HeLa cervical cancer cell line. The present study demonstrated the potential use of the marine actinobacterial strain of Nocardiopsis sp. MBRC-48 as an important source for gold nanoparticles with improved biomedical applications including antimicrobial, antioxidant as well as cytotoxic agent.

Antimicrobial Activity of Gold Nanoparticles and Ionic Gold

Gold, in both nanoparticle (AuNPs) and ionic forms, has been studied for antibiotic activities. Some of the organic complexes of Au (I & III) ions are antibacterial. AuNPs are antifungal, but with conflicting results on their antibacterial activity. We summarized these publications and found that AuNPs are generally not bactericidal, or only weakly at high concentrations. However, the reason AuNPs appear to be bactericidal is possibly due to the bactericidal activity of co-existing chemicals not completely removed from AuNPs: gold ions, surface coating agents, and chemicals involved in the synthesis. AuNPs can also act as carriers or delivery vehicles of antibiotics, thus enhancing the bactericidal effect of the antibiotics.

Actinobacteria mediated synthesis of nanoparticles and their biological properties: A review

Nanotechnology is gaining tremendous attention in the present century due to its expected impact on many important areas such as medicine, energy, electronics, and space industries. In this context, actinobacterial biosynthesis of nanoparticles is a reliable, eco-friendly, and important aspect of green chemistry approach that interconnects microbial biotechnology and nanobiotechnology. Antibiotics produced by actinobacteria are popular in almost all the therapeutic measures and it is known that these microbes are also helpful in the biosynthesis of nanoparticles with good surface and size characteristics. In fact, actinobacteria are efficient producers of nanoparticles that show a range of biological properties, namely, antibacterial, antifungal, anticancer, anti-biofouling, anti-malarial, anti-parasitic, antioxidant, etc. This review describes the potential use of the actinobacteria as the novel sources for the biosynthesis of nanoparticles with improved biomedical applications.

Mosquito larvicidal activity of silver nanoparticles synthesised using actinobacterium, Streptomyces sp. M25 against Anopheles subpictus, Culex quinquefasciatus and Aedes aegypti

The present work reports the larvicidal potential of microbially synthesised silver nanoparticles (AgNPs) by using an actinobacterium, Streptomyces sp. M25 isolated from Western Ghats, Tamil Nadu, India. The biomass of Streptomyces sp. was exposed to 1 mM silver nitrate (AgNO3) solution. The synthesis of AgNPs was confirmed by visual inspection followed by instrumental analysis such as UV-vis spectroscopy, fourier transform infrared spectroscopy, X-ray diffraction (XRD), energy dispersive X-ray spectroscopy, scanning electron microscopy, atomic force microscopy and transmission electron microscopy (TEM) with selected area electron diffraction. Based on the TEM and XRD analysis, the average size of the AgNPs was determined to be 10-35 nm. The biosynthesised AgNPs exhibited significant larvicidal activity against malarial vector, Anopheles subpictus (LC50 51.34 mg/L and χ (2) value of 8.228), filarial vector, Culex quinquefasciatus (LC50 48.98 mg/L and χ (2) value of 14.307) and dengue vector, Aedes aegypti (LC50 60.23 mg/L and χ (2) value of 4.042), respectively. Similarly, AgNO3 had larvicidal activity against malarial vector, A. subpictus (LC50 42.544 mg/L and χ (2) value of 2.561), filarial vector, C. quinquefasciatus (LC50 44.922 mg/L and χ (2) value of 1.693) and dengue vector, A. aegypti (LC50 39.664 mg/L and χ (2) value of 5.724), respectively. The current study is a rapid, cost effective, eco-friendly and single step approach. The Streptomyces sp. M25 is a newly added source for the synthesis of AgNPs with improved larvicidal activity.

Biosynthesis and microscopic study of metallic nanoparticles

Nanobiotechnology, bionanotechnology, and nanobiology are terms that have emerged in reference to the combination of nanotechnology and biology. Through the convergence of these disciplines, the production of metallic nanoparticles (NPs) using biological material as reducing agents is rapidly progressing. In the near future, the application of clean, non-toxic, and eco-friendly nanostructured material will be possible in industry and/or biomedicine. Currently, there is a wide range of organisms that have been reported to be useful in producing NPs. However, the development of finer protocols and the applicability of biosynthesized nanostructures are presently under study. Silver and gold are among the most studied metals due to their potential use in medical treatment. In fact, silver NPs have been evaluated as antimicrobial agents, having been successfully used against several types of fungi and bacteria. However, the use of such material in our daily life must be carefully evaluated. This article summarizes some of the most significant results using organisms to produce metallic NPs as well as the microscopic analyses used to characterize the nanostructured material obtained, providing a valuable database for future research.

Biosynthesis, antimicrobial and cytotoxic effect of silver nanoparticles using a novel Nocardiopsis sp. MBRC-1

The biosynthesis of nanoparticles has been proposed as a cost effective environmental friendly alternative to chemical and physical methods. Microbial synthesis of nanoparticles is under exploration due to wide biomedical applications, research interest in nanotechnology and microbial biotechnology. In the present study, an ecofriendly process for the synthesis of nanoparticles using a novel Nocardiopsis sp. MBRC-1 has been attempted. We used culture supernatant of Nocardiopsis sp. MBRC-1 for the simple and cost effective green synthesis of silver nanoparticles. The reduction of silver ions occurred when silver nitrate solution was treated with the Nocardiopsis sp. MBRC-1 culture supernatant at room temperature. The nanoparticles were characterized by UV-visible, TEM, FE-SEM, EDX, FTIR, and XRD spectroscopy. The nanoparticles exhibited an absorption peak around 420 nm, a characteristic surface plasmon resonance band of silver nanoparticles. They were spherical in shape with an average particle size of 45 ± 0.15 nm. The EDX analysis showed the presence of elemental silver signal in the synthesized nanoparticles. The FTIR analysis revealed that the protein component in the form of enzyme nitrate reductase produced by the isolate in the culture supernatant may be responsible for reduction and as capping agents. The XRD spectrum showed the characteristic Bragg peaks of 1 2 3, 2 0 4, 0 4 3, 1 4 4, and 3 1 1 facets of the face centered cubic silver nanoparticles and confirms that these nanoparticles are crystalline in nature. The prepared silver nanoparticles exhibited strong antimicrobial activity against bacteria and fungi. Cytotoxicity of biosynthesized AgNPs against in vitro human cervical cancer cell line (HeLa) showed a dose-response activity. IC50 value was found to be 200 μg/mL of AgNPs against HeLa cancer cells. Further studies are needed to elucidate the toxicity and the mechanism involved with antimicrobial and anticancer activity of the synthesized AgNPs as nanomedicine.