Biosynthesis of gold nanoparticles by Bacillus marisflavi and its potential in catalytic dye degradation

Microbial Nanotechnology for Precision Nanobiosynthesis: Innovations, Current Opportunities and Future Perspectives for Industrial Sustainability

A new area of biotechnology is nanotechnology. Nanotechnology is an emerging field that aims to develope various substances with nano-dimensions that have utilization in the various sectors of pharmaceuticals, bio prospecting, human activities and biomedical applications. An essential stage in the development of nanotechnology is the creation of nanoparticles. To increase their biological uses, eco-friendly material synthesis processes are becoming increasingly important. Recent years have shown a lot of interest in nanostructured materials due to their beneficial and unique characteristics compared to their polycrystalline counterparts. The fascinating performance of nanomaterials in electronics, optics, and photonics has generated a lot of interest. An eco-friendly approach of creating nanoparticles has emerged in order to get around the drawbacks of conventional techniques. Today, a wide range of nanoparticles have been created by employing various microbes, and their potential in numerous cutting-edge technological fields have been investigated. These particles have well-defined chemical compositions, sizes, and morphologies. The green production of nanoparticles mostly uses plants and microbes. Hence, the use of microbial nanotechnology in agriculture and plant science is the main emphasis of this review. The present review highlights the methods of biological synthesis of nanoparticles available with a major focus on microbially synthesized nanoparticles, parameters and biochemistry involved. Further, it takes into account the genetic engineering and synthetic biology involved in microbial nanobiosynthesis to the construction of microbial nanofactories.

Tackling breast cancer with gold nanoparticles: twinning synthesis and particle engineering with efficacy

The World Health Organization identifies breast cancer as the most prevalent cancer despite predominantly affecting women. Surgery, hormonal therapy, chemotherapy, and radiation therapy are the current treatment modalities. Site-directed nanotherapeutics, engineered with multidimensional functionality are now the frontrunners in breast cancer diagnosis and treatment. Gold nanoparticles with their unique colloidal, optical, quantum, magnetic, mechanical, and electrical properties have become the most valuable weapon in this arsenal. Their advantages include facile modulation of shape and size, a high degree of reproducibility and stability, biocompatibility, and ease of particle engineering to induce multifunctionality. Additionally, the surface plasmon oscillation and high atomic number of gold provide distinct advantages for tailor-made diagnosis, therapy or theranostic applications in breast cancer such as photothermal therapy, radiotherapy, molecular labeling, imaging, and sensing. Although pre-clinical and clinical data are promising for nano-dimensional gold, their clinical translation is hampered by toxicity signs in major organs like the liver, kidneys and spleen. This has instigated global scientific brainstorming to explore feasible particle synthesis and engineering techniques to simultaneously improve the efficacy and versatility and widen the safety window of gold nanoparticles. The present work marks the first study on gold nanoparticle design and maneuvering techniques, elucidating their impact on the pharmacodynamics character and providing a clear-cut scientific roadmap for their fast-track entry into clinical practice.

Phytogenic nanoparticles: synthesis, characterization, and their roles in physiology and biochemistry of plants

Researchers are swarming to nanotechnology because of its potentially game-changing applications in medicine, pharmaceuticals, and agriculture. This fast-growing, cutting-edge technology is trying different approaches for synthesizing nanoparticles of specific sizes and shapes. Nanoparticles (NPs) have been successfully synthesized using physical and chemical processes; there is an urgent demand to establish environmentally acceptable and sustainable ways for their synthesis. The green approach of nanoparticle synthesis has emerged as a simple, economical, sustainable, and eco-friendly method. In particular, phytoassisted plant extract synthesis is easy, reliable, and expeditious. Diverse phytochemicals present in the extract of various plant organs such as root, leaf, and flower are used as a source of reducing as well as stabilizing agents during production. Green synthesis is based on principles like prevention/minimization of waste, reduction of derivatives/pollution, and the use of safer (or non-toxic) solvent/auxiliaries as well as renewable feedstock. Being free of harsh operating conditions (high temperature and pressure), hazardous chemicals and the addition of external stabilizing or capping agents makes the nanoparticles produced using green synthesis methods particularly desirable. Different metallic nanomaterials are produced using phytoassisted synthesis methods, such as silver, zinc, gold, copper, titanium, magnesium, and silicon. Due to significant differences in physical and chemical properties between nanoparticles and their micro/macro counterparts, their characterization becomes essential. Various microscopic and spectroscopic techniques have been employed for conformational details of nanoparticles, like shape, size, dispersity, homogeneity, surface structure, and inter-particle interactions. UV-visible spectroscopy is used to examine the optical properties of NPs in solution. XRD analysis confirms the purity and phase of NPs and provides information about crystal size and symmetry. AFM, SEM, and TEM are employed for analyzing the morphological structure and particle size of NPs. The nature and kind of functional groups or bioactive compounds that might account for the reduction and stabilization of NPs are detected by FTIR analysis. The elemental composition of synthesized NPs is determined using EDS analysis. Nanoparticles synthesized by green methods have broad applications and serve as antibacterial and antifungal agents. Various metal and metal oxide NPs such as Silver (Ag), copper (Cu), gold (Au), silicon dioxide (SiO2), zinc oxide (ZnO), titanium dioxide (TiO2), copper oxide (CuO), etc. have been proven to have a positive effect on plant growth and development. They play a potentially important role in the germination of seeds, plant growth, flowering, photosynthesis, and plant yield. The present review highlights the pathways of phytosynthesis of nanoparticles, various techniques used for their characterization, and their possible roles in the physiology of plants.

Xanthan gum-based copper nano-magnetite doped carbon aerogel: A promising candidate for environmentally friendly catalytic dye degradation

In this work, a novel copper nano-magnetite doped carbon aerogel (CXMCA) was created utilizing a simple graft co-polymerization approach with xanthan gum (XG) as a template to tackle the agglomeration problem caused by magnetic nanoparticle magnetism. The results indicated that the XG based CXMCA exhibited outstanding magnetic properties (Ms = 36.52 emu/g) as well as strong catalytic activity for the degradation of cationic and anionic dyes. Among all organic dyes, methylene blue and crystal violet (MB, CV) as cationic dyes, as well as congo red and methyl orange (CR, and MO) as anionic dyes, CXMCA demonstrated an exceptional dye degradation rate (8.06 × 10-3 s-1-1.12 × 10-2 s-1) and was highly competent for cationic dyes with degradation (90 %-98 %) as compared to its unsupported magnetic nanoparticles. The formation of CXMCA catalyst is clearly confirmed by the FTIR, XRD, XPS, VSM, SEM & TEM analyses. We report a very effective xanthan gum-based copper nano-magnetite doped carbon aerogel dye scavenger with application in percentage dye degradation and kinetic investigations, as well as a remarkable reusability assay up to 7 repetition cycles. The findings suggested that using biological macromolecules like xanthan gum as a foundation to generate magnetic aerogels might be a good choice for evaluating environmental aspects.

Biogenic synthesis of AuNPs using Solanum virginianum L. and their antibacterial, antioxidant and catalytic applications

Biogenic synthesis of nanoparticles is gaining popularity worldwide because of being ecofriendly as well as economical, with minimal production of hazardous by-products. The present study was targeted to determine the antibacterial, free radical scavenging and catalytic activity of gold nanoparticles synthesized from Solanum virginianum L. (Sv-AuNPs). After addition of auric chloride, the color of aqueous plant extract changed from light yellow to purple-red, indicating the formation of nanoparticles. A strong peak at 536 nm affirmed synthesis of Sv-AuNPs, and negative zeta potential (- 30.7) indicated their being wrapped in anions. They exhibited face-centered cubic and crystalline nature as revealed by X-ray diffraction. Elemental composition of Sv-AuNPs was ascertained by energy-dispersive X-ray spectroscopy, and a sharp peak at 2.2 keV confirmed the presence of gold. The shape of Sv-AuNPs synthesized was spherical with size ranging from 29.1 ± 1 nm to 51.2 ± 0.7 nm. Antibacterial potential was evaluated against E. coli, C. violaceum, K. pneumoniae, P. aeruginosa, B. subtilis, M. smegmatis, and S. aureus and was found to be greater than aqueous plant extract. Sv-AuNPs exhibited antioxidant potential comparable to ascorbic acid, demonstrating their vital role in the prevention of reactive oxygen species related diseases. Apart from their pharmaceutical potential, these nanoparticles also exhibited promising catalytic efficacy. They degraded harmful dyes i.e. 4-nitro phenol (4-NP) and congo red (CR) at a very low concentration of 50 µg/ml. This is the first report on the antibacterial, antioxidant, and catalytic properties of Sv-AuNPs and we hope it will lead the way for nanoparticles multifunctionality.

Graphical abstract

GC-MS metabolomics profile of methanol extract of Acacia modesta gum and gum-assisted fabrication and characterization of gold nanoparticles through green synthesis approach

Hereunder, for the first time, we reported phytocompounds in the methanolic extract of Acacia modesta (AM) gum through Gas chromatography-mass spectrometry (GS-MS). Further, the AM gum aqueous solution was used for gold nanoparticles (AuNPs) synthesis through a simple, swift, eco-friendly, and less costly green synthesis approach. A total of 108 phytocompounds (63 with nonpolar, 45 with polar column) were identified in the gum extract, which includes fatty acids, alcohols, sterols, aldehyde/ketones, furans, aromatic compounds, esters, phenols, terpenes, sugar derivatives, alkaloids, and flavones. From three used concentrations (5, 10, and 15 mg/mL) of the AM gum aqueous solution, the 15 mg/mL gum solution resulted in more successful AuNP synthesis with a smaller size, which was visualized by a rusty red color appearance. UV-Visible absorption spectroscopy revealed the characteristic surface plasmon resonance (SPR) of AuNPs in aqueous solution at 540 nm. Dynamic light scattering (DLS) measurement of NPs solution revealed a hydrodynamic diameter of 162 ± 02 nm with the highest gum concentration where core AuNPs diameter was 22 ± 03 nm, recorded by Transmission electron microscopy. Zeta potential revealed fair stability of AuNPs that was not decreased with time. Catalytic activity experiments revealed that AM gum-based AuNPs can increase the rate of the reduction of methylene blue 10 times in comparison with AM gum extract alone. Results from this study showed that a diverse array of phytocompounds in AM gum can successfully reduce gold ions into gold nanoparticles, which can be used further in different pharmaceutical and industrial applications.

Draft genome sequence of potato crop bacterial isolates and nanoparticles-intervention for the induction of secondary metabolites biosynthesis

Introduction

Insights about the effects of gold nanoparticles (AuNPs) on the biosynthetic manipulation of unknown microbe secondary metabolites could be a promising technique for prospective research on nano-biotechnology.

Aim

In this research, we aimed to isolate a fresh, non-domesticated unknown bacterium strain from a common scab of potato crop located in Saudi Arabia and study the metabolic profile.

Methodology

This was achieved through genomic DNA (gDNA) sequencing using Oxford Nanopore Technology. The genomic data were subjected to several bioinformatics tools, including canu-1.9 software, Prokka, DFAST, Geneious Prime, and AntiSMASH. We exposed the culture of the bacterial isolate with different concentrations of AuNPs and investigated the effects of AuNPs on secondary metabolites biosynthesis using several analytical techniques. Furthermore, Tandem-mass spectrometric (MS/MS) technique was optimized for the characterization of several significant sub-classes.

Results

The genomic draft sequence assembly, alignment, and annotation have verified the bacterial isolate as Priestia megaterium. This bacterium has secondary metabolites related to different biosynthetic gene clusters. AuNPs intervention showed an increase in the production of compounds with the molecular weights of 254 and 270 Da in a direct-dependent manner with the increase of the AuNPs concentrations.

Conclusion

The increase in the yields of compound 1 and 2 concomitantly with the increase in the concentration of the added AuNPs provide evidences about the effects of nanoparticles on the biosynthesis of the secondary metabolites. It contributes to the discovery of genes involved in different biosynthetic gene clusters (BGCs) and prediction of the structures of the natural products.

Activation of peroxymonosulfate by base for degradation of methylene blue: role of bromide ions

Bromide ions are inevitable in aquatic environment and influence the degradation of contaminants in non-radical based advanced oxidation processes, but the role of reactive bromine species (RBS) remain obscure. This study investigated the role of bromide ions in the degradation of methylene blue (MB) during the base/peroxymonosulfate (PMS) process. The formation of RBS as a function of bromide ions were evaluated using a kinetic modelling. Bromide ions were shown to play crucial roles in MB degradation. Increasing the dosage of NaOH and Br^- increased the transformation kinetics of MB. However, brominated intermediates which are more toxic than precursor MB were generated in the presence of Br^-. The formation of adsorbable organic halides (AOX) was enhanced by elevating the dosage of Br^-. The formation of AOX was even more significant in the absence of NaOH, and the AOX values decreased with the increasing alkalinity. The kinetic model indicated that the dominant reactive species formed in the base/PMS/Br^- process are ¹O₂ and HOBr, and Br₂ in the Br^-/PMS process. Therefore, the influence of bromide ions should be taken into consideration in the application of the base/PMS process for organic matters in bromide-containing natural water. Strategies should be developed to make full use of RBS for the abatement of organic pollutants and to reduce the formation of AOX. This study reveals that in the treatment of saline wastewater by PMS-based processes, increasing the amount of NaOH may be an effective strategy to inhibit the accumulation of AOX.

Biogeneration of silver nanoparticles from Cuphea procumbens for biomedical and environmental applications

Nanotechnology is one of the most important and relevant disciplines today due to the specific electrical, optical, magnetic, chemical, mechanical and biomedical properties of nanoparticles. In the present study we demonstrate the efficacy of Cuphea procumbens to biogenerate silver nanoparticles (AgNPs) with antibacterial and antitumor activity. These nanoparticles were synthesized using the aqueous extract of C. procumbens as reducing agent and silver nitrate as oxidizing agent. The Transmission Electron Microscopy demonstrated that the biogenic AgNPs were predominantly quasi-spherical with an average particle size of 23.45 nm. The surface plasmonic resonance was analyzed by ultraviolet visible spectroscopy (UV-Vis) observing a maximum absorption band at 441 nm and Infrared Spectroscopy (FT IR) was used in order to structurally identify the functional groups of some compounds involved in the formation of nanoparticles. The AgNPs demonstrated to have antibacterial activity against the pathogenic bacteria Escherichia coli and Staphylococcus aureus, identifying the maximum zone of inhibition at the concentration of 0.225 and 0.158 µg/mL respectively. Moreover, compared to the extract, AgNPs exhibited better antitumor activity and higher therapeutic index (TI) against several tumor cell lines such as human breast carcinoma MCF-7 (IC₅₀ of 2.56 µg/mL, TI of 27.65 µg/mL), MDA-MB-468 (IC₅₀ of 2.25 µg/mL, TI of 31.53 µg/mL), human colon carcinoma HCT-116 (IC₅₀ of 1.38 µg/mL, TI of 51.07 µg/mL) and melanoma A-375 (IC₅₀ of 6.51 µg/mL, TI of 10.89 µg/mL). This fact is of great since it will reduce the side effects derived from the treatment. In addition, AgNPs revealed to have a photocatalytic activity of the dyes congo red (10^-3 M) in 5 min and malachite green (10^-3 M) in 7 min. Additionally, the degradation percentages were obtained, which were 86.61% for congo red and 82.11% for malachite green. Overall, our results demonstrated for the first time that C. procumbens biogenerated nanoparticles are excellent candidates for several biomedical and environmental applications.

Facile Synthesis and Fabrication of NIPAM-Based Cryogels for Environmental Remediation

Herein, polymeric cryogels containing poly(N-isopropylacrylamide) were synthesized by cryo-polymerization at subzero temperature. The synthesized cryogels were loaded with silver and palladium nanoparticles by the chemical reduction method at room temperature using the reducing agent NaBH₄. Moreover, for comparison with cryogels, pure poly(N-isopropylacrylamide) hydrogel and its silver hybrid were also prepared by the conventional method at room temperature. The chemical structure and functional group analysis of the pure cryogels was confirmed by Fourier transform infrared spectroscopy. The synthesis of hybrid cryogels was confirmed by the X-ray diffraction technique and energy dispersive X-ray. The pore size and surface morphology of the pure cryogels, their respective hybrid cryogels and of conventional hydrogels were studied by using the scanning electron microscopy technique. The hybrid cryogels were successfully used as a catalyst for the degradation of methyl orange dye. The degradation performance of the hybrid cryogels was much better than its counterpart hybrid hydrogel for methyl orange dye. The effect of temperature and amount of catalyst on catalytic performance was studied by UV-visible spectroscopy. The reduction follows pseudo-first-order reaction kinetics. In addition, the antibacterial activities of these cryogels were evaluated against Gram-positive bacteria (Staphylococcus aureus, ATCC: 2593) and Gram-negative bacteria (Escherichia coli, ATCC: 25922). Both hybrid cryogels have shown much better antibacterial activity for these two strains of bacteria compared to pure cryogels. The results indicate that these cryogels are potential candidates for water purification systems as well as biomedical applications.

Antibody-modified Gold Nanobiostructures: Advancing Targeted Photodynamic Therapy for Improved Cancer Treatment

Photodynamic therapy (PDT) is an innovative, non-invasive method of treating cancer that uses light-activated photosensitizers to create reactive oxygen species (ROS). However, challenges associated with the limited penetration depth of light and the need for precise control over photosensitizer activation have hindered its clinical translation. Nanomedicine, particularly gold nanobiostructures, offers promising solutions to overcome these limitations. This paper reviews the advancements in PDT and nanomedicine, focusing on applying antibody-modified gold nanobiostructures as multifunctional platforms for enhanced PDT efficacy and improved cancer treatment outcomes. The size, shape, and composition of gold nanobiostructures can significantly influence their PDT efficacy, making synthetic procedures crucial. Functionalizing the surface of gold nanobiostructures with various molecules, such as antibodies or targeting agents, bonding agents, PDT agents, photothermal therapy (PTT) agents, chemo-agents, immunotherapy agents, and imaging agents, allows composition modification. Integrating gold nanobiostructures with PDT holds immense potential for targeted cancer therapy. Antibody-modified gold nanobiostructures, in particular, have gained significant attention due to their tunable plasmonic characteristics, biocompatibility, and surface functionalization capabilities. These multifunctional nanosystems possess unique properties that enhance the efficacy of PDT, including improved light absorption, targeted delivery, and enhanced ROS generation. Passive and active targeting of gold nanobiostructures can enhance their localization near cancer cells, leading to efficient eradication of tumor tissues upon light irradiation. Future research and clinical studies will continue to explore the potential of gold nanobiostructures in PDT for personalized and effective cancer therapy. The synthesis, functionalization, and characterization of gold nanobiostructures, their interaction with light, and their impact on photosensitizers' photophysical and photochemical properties, are important areas of investigation. Strategies to enhance targeting efficiency and the evaluation of gold nanobiostructures in vitro and in vivo studies will further advance their application in PDT. The integrating antibody-modified gold nanobiostructures in PDT represents a promising strategy for targeted cancer therapy. These multifunctional nanosystems possess unique properties that enhance PDT efficacy, including improved light absorption, targeted delivery, and enhanced ROS generation. Continued research and development in this field will contribute to the advancement of personalized and effective cancer treatment approaches.

New aspects of lipopeptide-incorporated nanoparticle synthesis and recent advancements in biomedical and environmental sciences: a review

The toxicity of metal nanoparticles has introduced promising research in the current scenario since an enormous number of people have been potentially facing this problem in the world. The extensive attention on green nanoparticle synthesis has been focussed on as a vital step in bio-nanotechnology to improve biocompatibility, biodegradability, eco-friendliness, and huge potential utilization in various environmental and clinical assessments. Inherent influence on the study of green nanoparticles plays a key role to synthesize the controlled and surface-influenced molecule by altering the physical, chemical, and biological assets with the provision of various precursors, templating/co-templating agents, and supporting solvents. However, in this article, the dominant characteristics of several kinds of lipopeptide biosurfactants are discussed to execute a critical study of factors affecting synthesis procedure and applications. The recent approaches of metal, metal oxide, and composite nanomaterial synthesis have been deliberated as well as the elucidation of the reaction mechanism. Furthermore, this approach shows remarkable boosts in the production of nanoparticles with the very less employed harsh and hazardous processes as compared to chemical or physical method-based nanoparticle synthesis. This study also shows that the advances in strain selection for green nanoparticle production could be a worthwhile and strong economical approach in futuristic medical science research.

Nanogold morphologies with the same surface chemistry provoke a different innate immune response: An in-vitro and in-vivo study

Gold nanomaterials (GNMs) have unique optical properties with less antigenicity, and their physicochemical properties have strong relation with an immunological response at bio-interface including antigenicity. An interpretation of this correlation would significantly impact on the clinical and theranostic applications of GNMs. Herein, we studied the effect of GNMs morphology on the cytotoxicity (in-vitro), innate immune responses, hepatotoxicity, and nephrotoxicity (in-vivo studies) using gold nano-cups (GNCs), porous gold nanospheres (PGNSs) and solid gold nano particles (SGNPs) coated with the same ligand to ensure similar surface chemistry. The cytotoxicity was assessed via sulfo-rhodamine B (SRB) assay, and the cytotoxicity data showed that morphological features at nanoscale dimensions like surface roughness and hollowness etc. have a significant impact on cellular viability. The biochemical and histopathological study of liver and kidney tissues also showed that all GNMs did not show any toxicity even at high concentration (100 μL). The relative quantification of cytokine gene expression of TNF-α, IFN-γ, IL-4, 1L-6, and 1L-17 (against each morphology) was checked after in-vivo activation in mice. Among the different nanogold morphologies, PVP stabilized GNCs (PVP-GNCs) showed the highest release of pro-inflammatory cytokines, which might be due to their high surface energy and large surface area for exposure as compared to other nanogold morphologies studied. The pro-inflammatory cytokine release could be suppressed by coating with some anti-inflammatory polymer, i.e., inulin. The in-vitro results of pro-inflammatory (TNF-α, IL-1) cytokines also suggested that all GNMs may induce activation of macrophages and Th1 immune response. The in-vivo activation results showed a decrease in mRNA expression of the cytokines (TNF-α, IFN-γ, IL-4, 1L-6 and 1L-17). Based on these findings, we proposed that the shape and morphology of GNMs control their immune response at nano-bio interface, and it must be considered while designing their role for different biomedical applications like immuno-stimulation and bio-imaging.

Green Chemistry Based Gold Nanoparticles Synthesis Using the Marine Bacterium Lysinibacillus odysseyi PBCW2 and Their Multitudinous Activities

Green chemistry has paved an 'avant-garde avenue' in the production and fabrication of eco-friendly stable nanoparticles employing the utilization of biological agents. In the present study we present the first report on the potential of the marine bacterium Lysinibacillus odysseyi PBCW2 for the extracellular production of gold nanoparticles (AuNPs). Utilizing a variety of methods, AuNPs in the cell-free supernatant of L. odysseyi (CFS-LBOE) were identified and their antioxidant, antibacterial, and dye-degrading properties were examined. The visual coloring of the reaction mixture to a ruby red hue showed the production of LBOE-AuNPs; validated by means of XRD, TEM, SEM, XRD, DLS, TGA, and FT-IR analysis. Additionally, the 2,2-diphenyl-1-picrylhydrazyl technique and the well diffusion assay were used to examine their dose-dependent antioxidant and antibacterial activity. These biogenic LBOE-AuNPs showed 91% dye degradation efficiency during catalytic reduction activity on BTB dye, demonstrating their versatility as options for heterogeneous catalysis.

A comprehensive review on sustainable greener nanoparticles for efficient dye degradation

The effluents released from textile industries mainly consist of dyes, metals and other pollutants. Dyes often are discharged in wastewater streams causing adverse effect on the environment. To eliminate these harmful dyes, various techniques are emerging out of which nanotechnology is the most reliable and safer. Nanotechnology offers convincing applications in case of environmental and economic concerns. The bio-synthesis of nanoparticles has several advantages over conventional methods and approach towards environment concern as well. Biological method of nanoparticles synthesis is concluded to be the most promising and efficient in action. Bio-synthesised nanoparticles could be used for treatment and decolourisation of dyes in an efficient manner. This review comprises the study of number of bio-synthesised nanoparticles utilised for degradation of various dyes present as pollutants in wastewater. Bio-synthesised nanoparticles such as gold, silver, iron, cobalt, zinc, titanium and molybdenum used for degradation of various dyes have been discussed in this review.

Recent advances on botanical biosynthesis of nanoparticles for catalytic, water treatment and agricultural applications: A review

Green synthesis of nanoparticles using plant extracts minimizes the usage of toxic chemicals or energy. Here, we concentrate on the green synthesis of nanoparticles using natural compounds from plant extracts and their applications in catalysis, water treatment and agriculture. Polyphenols, flavonoid, rutin, quercetin, myricetin, kaempferol, coumarin, and gallic acid in the plant extracts engage in the reduction and stabilization of green nanoparticles. Ten types of nanoparticles involving Ag, Au, Cu, Pt, CuO, ZnO, MgO, TiO₂, Fe₃O₄, and ZrO₂ with emphasis on their formation mechanism are illuminated. We find that green nanoparticles serve as excellent, and recyclable catalysts for reduction of nitrophenols and synthesis of organic compounds with high yields of 83-100% and at least 5 recycles. Many emerging pollutants such as synthetic dyes, antibiotics, heavy metal and oils are effectively mitigated (90-100%) using green nanoparticles. In agriculture, green nanoparticles efficiently immobilize toxic compounds in soil. They are also sufficient nanopesticides to kill harmful larvae, and nanoinsecticides against dangerous vectors of pathogens. As potential nanofertilizers and nanoagrochemicals, green nanoparticles will open a revolution in green agriculture for sustainable development.

Plant Extract-Based Synthesis of Metallic Nanomaterials, Their Applications, and Safety Concerns

Nanotechnology has attracted the attention of researchers from different scientific fields because of the escalated properties of nanomaterials compared with the properties of macromolecules. Nanomaterials can be prepared through different approaches involving physical and chemical methods. The development of nanomaterials through plant-based green chemistry approaches is more advantageous than other methods from the perspectives of environmental safety, animal, and human health. The biomolecules and metabolites of plants act as reducing and capping agents for the synthesis of metallic green nanomaterials. Plant-based synthesis is a preferred approach as it is not only cost-effective, easy, safe, clean, and eco-friendly but also provides pure nanomaterials in high yield. Since nanomaterials have antimicrobial and antioxidant potential, green nanomaterials synthesized from plants can be used for a variety of biomedical and environmental remediation applications. Past studies have focused mainly on the overall biogenic synthesis of individual or combinations of metallic nanomaterials and their oxides from different biological sources, including microorganisms and biomolecules. Moreover, from the viewpoint of biomedical applications, the literature is mainly focusing on synthetic nanomaterials. Herein, we discuss the extraction of green molecules and recent developments in the synthesis of different plant-based metallic nanomaterials, including silver, gold, platinum, palladium, copper, zinc, iron, and carbon. Apart from the biomedical applications of metallic nanomaterials, including antimicrobial, anticancer, diagnostic, drug delivery, tissue engineering, and regenerative medicine applications, their environmental remediation potential is also discussed. Furthermore, safety concerns and safety regulations pertaining to green nanomaterials are also discussed. This article is protected by copyright. All rights reserved.

Green Synthesis of Gold Nanoparticles: An Eco-Friendly Approach

By virtue of their unique physicochemical properties, gold nanoparticles (AuNPs) have gained significant interest in a broad range of biomedical applications such as sensors, diagnosis, and therapy. AuNPs are generally synthesized via different conventional physical and chemical methods, which often use harmful chemicals that induce health hazards and pollute the environment. To overcome these issues, green synthesis techniques have evolved as alternative and eco-friendly approaches to the synthesis of environmentally safe and less-expensive nanoparticles using naturally available metabolites from plants and microorganisms such as bacteria, fungi, and algae. This review provides an overview of the advances in the synthesis of AuNPs using different biological resources with examples, and their profound applications in biomedicine. A special focus on the biosynthesis of AuNPs using different medicinal plants and their multifunctional applications in antibacterial, anti-inflammatory, and immune responses are featured. Additionally, the applications of AuNPs in cancer theranostics, including contrast imaging, drug delivery, hyperthermia, and cancer therapeutics, are comprehensively discussed. Moreover, this review will shed light on the importance of the green synthesis approach, and discuss the advantages, challenges, and prospects in this field.

Biogenic proficient synthesis of (Au-NPs) via aqueous extract of Red Dragon Pulp and seed oil: Characterization, antioxidant, cytotoxic properties, anti-diabetic anti-inflammatory, anti-Alzheimer and their anti-proliferative potential against cancer cell lines

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Novel Green synthesis of Au-NPs using Dragon fruit pulp and seed oil extract for the first time.

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Use of green and safer protocol for synthesis of Au-NPs further demonstrate that we can apply green chemistry protocols to reduce environmental pollution and disposal of waste toxicants.

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FTIR analysis confirmed the capping of therapeutically potent phytochemicals which are of great use in applied field especially medical.

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Significant Anti-diabetic, Anti-inflammatory, Anti-Alzheimer and Cytotoxic potential of biosynthesized Au-NPs create a new idea and shifting experts to treat cancerous cell lines.

Gold nanoparticles with tiny sizes and biostability are particularly essential and are employed in a variety of biomedical applications. Using a reducing agent and a stabilising agent to make gold nanoparticles has been reported in a number of studies. Gold nanoparticles with a particle size of 25.31 nm were synthesized in this study utilising Hylocereus polyrhizus (Red Pitaya) extract, which functions as a reducing and stabilising agent. The extract of Red Pitaya is said to be a powerful antioxidant and anti-cancer agent. Because of its substantial blood biocompatibility and physiological stability, green production of gold nanoparticles with H. polyrhizus fruit extract is an alternative to chemical synthesis and useful for biological and medical applications. The formation and size distribution of gold nanoparticles were confirmed by HPLC, UV-Vis spectrophotometer, X-ray diffraction (XRD), Dynamic light scattering (DLS), Zeta potential, Transmission electron microscopy (TEM), Fourier transformed infrared spectroscopy (FTIR), Energy dispersive X-ray (EDX) and X-ray photoelectron spectroscopy (XPS). The well-analysed NPs were used in various biological assays, including anti-diabetic, anti-inflammatory, anti-Alzheimer, and antioxidant (DPPH), and cytotoxic investigations. The NPs also showed a dose-dependent cytotoxic activity against HCT-116, HepG2 and MCF-7 cell lines, with IC₅₀ of 100 µg/mL for HCT-116 cells, 155 µg/mL for HepG2, and for MCF-7 cells the value was 165 µg/mL respectively. Finally, the outstanding biocompatibility of Au-NPs has led to the conclusion that they are a promising choice for various biological applications.

Recent developments in hydrogels containing copper and palladium for the catalytic reduction/degradation of organic pollutants

The elimination of toxic and hazardous contaminants from different environmental media has become a global challenge, causing researchers to focus on the treatment of pollutants. Accordingly, the elimination of inorganic and organic pollutants using sustainable, effective, and low-cost heterogeneous catalysts is considered as one of the most essential routes for this aim. Thus, many efforts have been devoted to the synthesis of novel compounds and improving their catalytic performance. Recently, palladium- and copper-based hydrogels have been used as catalysts for reduction, degradation, and decomposition reactions because they have significant features such as high mechanical strength, thermal stability, and high surface area. Herein, we summarize the progress achieved in this field, including the various methods for the synthesis of copper- and palladium-based hydrogel catalysts and their applications for environmental remediation. Moreover, palladium- and copper-based hydrogel catalysts, which have certain advantages, including high catalytic ability, reusability, easy work-up, and simple synthesis, are proposed as a new group of effective catalysts.

The elimination of toxic and hazardous contaminants from different environmental media has become a global challenge, causing researchers to focus on the treatment of pollutants.

Marine Macroalgae Display Bioreductant Efficacy for Fabricating Metallic Nanoparticles: Intra/Extracellular Mechanism and Potential Biomedical Applications

The application of hazardous chemicals during nanoparticle (NP) synthesis has raised alarming concerns pertaining to their biocompatibility and equally to the environmental harmlessness. In the recent decade, nanotechnological research has made a gigantic shift in order to include the natural resources to produce biogenic NPs. Within this approach, researchers have utilized marine resources such as macroalgae and microalgae, land plants, bacteria, fungi, yeast, actinomycetes, and viruses to synthesize NPs. Marine macroalgae (brown, red, and green) are rich in polysaccharides including alginates, fucose-containing sulfated polysaccharides (FCSPs), galactans, agars or carrageenans, semicrystalline cellulose, ulvans, and hemicelluloses. Phytochemicals are abundant in phenols, tannins, alkaloids, terpenoids, and vitamins. However, microorganisms have an abundance of active compounds ranging from sugar molecules, enzymes, canonical membrane proteins, reductase enzymes (NADH and NADPH), membrane proteins to many more. The prime reason for using the aforesaid entities in the metallic NPs synthesis is based on their intrinsic properties to act as bioreductants, having the capability to reduce and cap the metal ions into stabilized NPs. Several green NPs have been verified for their biocompatibility in human cells. Bioactive constituents from the above resources have been found on the green metallic NPs, which has demonstrated their efficacies as prospective antibiotics and anti-cancer agents against a range of human pathogens and cancer cells. Moreover, these NPs can be characterized for the size, shapes, functional groups, surface properties, porosity, hydrodynamic stability, and surface charge using different characterization techniques. The novelty and originality of this review is that we provide recent research compilations on green synthesis of NPs by marine macroalgae and other biological sources (plant, bacteria, fungi, actinomycetes, yeast, and virus). Besides, we elaborated on the detailed intra- and extracellular mechanisms of NPs synthesis by marine macroalgae. The application of green NPs as anti-bacterial, anti-cancer, and popular methods of NPs characterization techniques has also been critically reviewed.

Bioinspired Nanomodification Strategies: Moving from Chemical-Based Agrosystems to Sustainable Agriculture

Agrochemicals have supported the development of the agricultural economy and national population over the past century. However, excessive applications of agrochemicals pose threats to the environment and human health. In the last decades, nanoparticles (NPs) have been a hot topic in many fields, especially in agriculture, because of their physicochemical properties. Nevertheless, the prevalent methods for fabricating NPs are uneconomical and involve toxic reagents, hindering their extensive applications in the agricultural sector. In contrast, inspired by biological exemplifications from microbes and plants, their extract and biomass can act as a reducing and capping agent to form NPs without any toxic reagents. NPs synthesized through these bioinspired routes are cost-effective, ecofriendly, and high performing. With the development of nanotechnology, biosynthetic NPs (bioNPs) have been proven to be a substitute strategy for agrochemicals and traditional NPs in heavy-metal remediation of soil, promotion of plant growth, and management of plant disease with less toxicity and higher performance. Therefore, bioinspired synthesis of NPs will be an inevitable trend for sustainable development in agricultural fields. This critical review will demonstrate the bioinspired synthesis of NPs and discuss the influence of bioNPs on agricultural soil, crop growth, and crop diseases compared to chemical NPs or agrochemicals.

Chemo-metrically formulated consortium with selectively screened bacterial strains for ameliorated biotransformation and detoxification of 1,4-dioxane

The biotransformation of 1,4-dioxane, a endrocrine disrupting chemical was achieved using different bacterial strains and their consortia. Three different bacterial isolates were screened on their ability to grow with 50 mg/L 1,4-dioxane in the basal mineral medium. Then the isolates were tested for its efficiency to biotransform 1000 mg/L 1,4-dioxane at varying period of time; 24-120 h. The isolates were distinguished by their morphological features and 16 S rRNA gene sequencing was done to evaluate the phylogenetic relationships. The isolates were identified as Bacillus marisflavi strain MGA, Aeromonas hydrophila strain AG and Shewanella putrefaciens strain AG. The degree of biotransformation was escalated by constructing a bacterial consortium using statistical tool; response-mixture matrix under the design of experiments. The fully grown bacterial strains were used as ingredients in different proportions to formulate the consortium. The biotransformation was analyzed for functional attenuation using spectroscopic techniques and reduction in 1,4-dioxane level was confirmed using mass spectrometry. The precise quantification of biotransformation using mass spectral profile revealed that the consortium removed 31%, 61% and 85% of 1000 mg/L 1,4-dioxane within 96, 120 and 144 h respectively. The activities of inducible laccase were elucidated during biotransformation of 1,4-dioxane. Bio-toxicity of treated and untreated 1,4-dioxane on brine shrimp; Artemia salina showed that the biotransformed products were less toxic. Therefore, this report would be first of its kind to report the biotransformation and detoxification of 1,4-dioxane by a statistically designed bacterial consortium.

Arabian Primrose leaf extract mediated synthesis of silver nanoparticles: their industrial and biomedical applications

The present study encompasses green synthesis of silver nanoparticles (AgNPs) using aqueous leaf extract of Arabian Primrose within 6 min of reaction at 60 °C, pH 7 and their characterisation using physico-chemical analytical techniques. UV-Visible spectroscopy elucidated the surface plasmon resonance around 420 nm. FESEM and TEM images revealed that AgNPs were spherical with average diameter 10-60 nm. XRD pattern confirmed their crystalline nature. The leaf extract rich in phenolics and flavonoids was subjected to GC-MS analysis that identified bioactive compounds helping in reduction and stabilisation of AgNPs. The synthesised AgNPs possessed high anti-oxidant potential against DPPH and H₂O₂ radicals. Incidentally, the AgNPs acted as excellent nanocatalyst towards borohydride reduction and degradation of structurally different organic dyes. The AgNPs also exhibited selective colorimetric sensing of hazardous mercuric, ferric ions and ammonia. Such AgNPs were cytotoxic against HeLa cells (IC₅₀ 7.18 µg/mL) and compatible towards normal L₂₀B cells. These AgNPs showed effective anti-microbial activity against different human pathogens tested (bacterial and fungal). This is probably the first report of AgNPs synthesis using Arabian Primrose leaf extract showing strong anti-oxidant, catalytic, biosensing, anti-cancer and anti-microbial activities and find remarkable applications in medical, industrial and ecological sectors.

Role of gold nanoparticles in advanced biomedical applications

Gold nanoparticles (GNPs) have generated keen interest among researchers in recent years due to their excellent physicochemical properties. In general, GNPs are biocompatible, amenable to desired functionalization, non-corroding, and exhibit size and shape dependent optical and electronic properties. These excellent properties of GNPs exhibit their tremendous potential for use in diverse biomedical applications. Herein, we have evaluated the recent advancements of GNPs to highlight their exceptional potential in the biomedical field. Special focus has been given to emerging biomedical applications including bio-imaging, site specific drug/gene delivery, nano-sensing, diagnostics, photon induced therapeutics, and theranostics. We have also elaborated on the basics, presented a historical preview, and discussed the synthesis strategies, functionalization methods, stabilization techniques, and key properties of GNPs. Lastly, we have concluded this article with key findings and unaddressed challenges. Overall, this review is a complete package to understand the importance and achievements of GNPs in the biomedical field.

Synthesis of Metal Nanoparticles by Microorganisms

Metal nanoparticles (NPs), with sizes ranging from 1–100 nm, are of great scientific interest because their functions and features differ greatly from those of bulk metal. Chemical or physical methods are used to synthesize commercial quantities of NPs, and green, energy-efficient approaches generating byproducts of low toxicity are desirable to minimize the environmental impact of the industrial methods. Some microorganisms synthesize metal NPs for detoxification and metabolic reasons at room temperature and pressure in aqueous solution. Metal NPs have been prepared via green methods by incubating microorganisms or cell-free extracts of microorganisms with dissolved metal ions for hours or days. Metal NPs are analyzed using various techniques, such as ultraviolet-visible spectroscopy, electron microscopy, X-ray diffraction, electron diffraction, energy-dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy. Numerous publications have focused on microorganisms that synthesize various metal NPs. For example, Ag, Au, CdS, CdSe, Cu, CuO, Gd2O3, Fe3O4, PbS, Pd, Sb2O3, TiO2, and ZrO2 NPs have been reported. Herein, we review the synthesis of metal NPs by microorganisms. Although the molecular mechanisms of their synthesis have been investigated to some extent, experimental evidence for the mechanisms is limited. Understanding the mechanisms is crucial for industrial-scale development of microorganism-synthesized metal NPs.

Plant Extracts Activated by Cold Atmospheric Pressure Plasmas as Suitable Tools for Synthesis of Gold Nanostructures with Catalytic Uses

Because cold atmospheric pressure plasma (CAPP)-based technologies are very useful tools in nanomaterials synthesis, in this work we have connected two unique in their classes approaches-a CAPP-based protocol and a green synthesis method in order to obtain stable-in-time gold nanoparticles (AuNPs). To do so, we have used an aqueous Gingko biloba leave extract and an aqueous Panax ginseng root extract (untreated or treated by CAPP) to produce AuNPs, suitable for catalytical uses. Firstly, we have adjusted the optical properties of resulted AuNPs, applying UV/Vis absorption spectrophotometry (UV/Vis). To reveal the morphology of Au nanostructures, transmission electron microscopy (TEM) in addition to energy dispersive X-ray scattering (EDX) and selected area X-ray diffraction (SAED) was utilized. Moreover, optical emission spectrometry (OES) in addition to a colorimetric method was used to identify and determine the concentration of selected RONS occurring at the liquid-CAPP interface. Additionally, attenuated total reflectance Fourier transform-infrared spectroscopy (ATR FT-IR) was applied to reveal the active compounds, which might be responsible for the AuNPs surface functionalization and stabilization. Within the performed research it was found that the smallest in size AuNPs were synthesized using the aqueous P. ginseng root extract, which was activated by direct current atmospheric pressure glow discharge (dc-APGD), generated in contact with a flowing liquid cathode (FLC). On the contrary, taking into account the aqueous G. biloba leave extract, the smallest in size AuNPs were synthesized when the untreated by CAPP aqueous G. biloba leave extract was involved in the Au nanostructures synthesis. For catalytical studies we have chosen AuNPs produced using the aqueous P. ginseng root extract activated by FLC-dc-APGD as well as AuNPs synthesized using the aqueous G. biloba leave extract also activated by FLC-dc-APGD. Those NPs were successfully used as homogenous catalysts for the reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP).

Selective bacterial colonization processes on polyethylene waste samples in an abandoned landfill site

The microbial colonization of plastic wastes has been extensively studied in marine environments, while studies on aged terrestrial wastes are scarce, and mostly limited to the isolation of plastic-degrading microorganisms. Here we have applied a multidisciplinary approach involving culturomics, next-generation sequencing analyses and fine-scale physico-chemical measurements to characterize plastic wastes retrieved in landfill abandoned for more than 35 years, and to assess the composition of bacterial communities thriving as biofilms on the films’ surfaces. All samples were characterized by different colors but were all of polyethylene; IR and DSC analyses identified different level of degradation, while FT-Raman spectroscopy and X-ray fluorescence further assessed the degradation level and the presence of pigments. Each plastic type harbored distinct bacterial communities from the others, in agreement with the differences highlighted by the physico-chemical analyses. Furthermore, the most degraded polyethylene films were found to host a bacterial community more similar to the surrounding soil as revealed by both α- and β-diversity NGS analyses. This work confirms the novel hypothesis that different polyethylene terrestrial waste samples select for different bacterial communities, and that structure of these communities can be correlated with physico-chemical properties of the plastics, including the degradation degree.

Catalytic and antibacterial properties of gold nanoparticles synthesized by a green approach for bioremediation applications

In this work, we are proposing the green synthesis of gold nanoparticles (AuNPs) using aqueous extracts of A. triphylla and evaluating their antibacterial and catalytic properties. Characterization was performed by UV-Vis and FT-IR spectroscopies, X-ray diffraction, and transmission electron microscopy (TEM). Antibacterial activity of AuNPs was analyzed using E. coli and S. Aureus and catalytic activity was determined by the degradation of methylene blue and congo red. UV-Vis analysis showed an increase in AuNPs concentration by increasing the extract concentration, volume extract, and precursor salt concentration. The crystalline nature of AuNPs was corroborated by X-ray diffraction. TEM analysis showed nanoparticles with spherical morphology (mostly) and size between 40 and 60 nm. These results are novel because they showed a homogeneous morphology and a narrow size distribution which is difficult to obtain in green synthesis processes. Results of antibacterial activity showed inhibition zones of 11.3 mm and 10.6 mm for S. Aureus and E. coli, respectively, indicating the bactericidal capacity of the nanoparticles. The degradation periods for methylene blue and congo red were 5 and 11 min, respectively, which are very short compared with previous reports. These results are of great significance for catalytic applications. Therefore, A. triphylla extracts made possible AuNPs synthesis and the nanoparticles obtained can be used as catalytic and antibacterial materials for water remediation.

Synthesis and applications of biogenic nanomaterials in drinking and wastewater treatment

The continuous increase in water pollution by various organic & inorganic contaminants has become a major issue of concern worldwide. Furthermore, the anthropogenic activities for the manufacturing of various products have boosted this problem manifold. To overcome this serious issue, nanotechnology has initiated to explore various proficient strategies to treat waste water in a more precise and accurate way with the support of various nanomaterials. In recent times, nanosized materials have proved their applicability to provide clean and affordable water treatment technologies. The exclusive features such as high surface area and mechanical properties, greater chemical reactivity, lower cost and energy, efficient regeneration for reuse allow the nanomaterials perfect for water remediation. But the conventional routes of synthesis of nanomaterials encompass the involvement of hazardous and volatile chemicals; therefore the use of nanomaterials further creates the secondary pollution. This issue has intrigued the scientists to develop biogenic pathways and procedures which are environmentally safer and inexpensive. It has led to the new trends that involve developing bio-inspired nano-scale adsorbents and catalysts for the removal and degradation of a wide range of water pollutants. Carbohydrates, proteins, polymers, flavonoids, alkaloids and several antioxidants obtained from plants, bacteria, fungi, and algae have proven their effectiveness as capping and stabilizing agents during manufacture of nanomaterials. Application of biogenic nanomaterials for waste water treatment is relatively newer but rapidly escalating area of research. In the present review, promises and challenges for the synthesis of various biogenic nanomaterials and their potential applications in waste water treatment and/or water purification have been discussed.

Kinetic study of gold nanoparticle mediated photocatalytic degradation of Victoria blue

In the study, biogenic gold nanoparticles (AuNPs) were used for the photocatalytic degradation of triphenylmethane dyes Victoria blue B (VBB) and R (VBR). The process was found to result in an approximate degradation of 65 and 52%, respectively, for VBB and VBR within a period of 8 h. The relative rate of photocatalytic degradation of VBB and VBR was identified to be 0.0195 ± 0.0031/min and 0.0295 ± 0.0025/min, respectively, by using the Langmuir-Hinshelwood model. By using the Vigna unguiculata model system, the degradation products were demonstrated to have non-toxic effect. Moreover, the less toxic nature of AuNPs used for dye removal highlights its feasibility for large-scale application. Hence, the AuNPs-based photocatalytic dye degradation as described in the study is cost-effective, rapid and environment-friendly.

Actinomycetes mediated synthesis of gold nanoparticles from the culture supernatant of Streptomyces griseoruber with special reference to catalytic activity

Biogenic synthesis of nanoparticles has received a tremendous attention from the past few decades. The significant progress in the field of nanotechnology has resulted in a cost-effective and eco-friendly process for nanoparticle synthesis. In the present study, the extracellular synthesis of gold nanoparticles was carried out using culture supernatant of Streptomyces griseoruber, actinomycetes isolated from the soil. Bioreduction of gold nanoparticles was confirmed by UV-visible spectrophotometer that showed the peak between 520 and 550 nm. The crystalline nature and mean size of the GNPs were confirmed using XRD. FTIR revealed the possible functional group that could be useful in immobilisation and stabilisation of GNPs. Size and distribution of the biosynthesized GNPs were analysed by HR-TEM that showed the formation of GNPs in the range of 5-50 nm. The synthesised GNPs showed good catalytic activity for the degradation of methylene blue. The study shows the rapid and eco-friendly synthesis of GNPs from Streptomyces griseoruber, and this is the first report on the catalytic activity of GNPs from actinomycetes so far.