Applications of biosynthesized metallic nanoparticles - a review

Rhodiola rosea Rhizome Extract-Mediated Green Synthesis of Silver Nanoparticles and Evaluation of Their Potential Antioxidant and Catalytic Reduction Activities

The silver nanoparticles (AgNPs) using the rhizome extract of Rhodiola rosea have been reported. However, their antioxidant activity and whether the biogenic AgNPs could be used to catalyze the reduction of hazardous dye or used as fluorescence enhancers are unknown. This study focused on the facile green synthesis of silver nanoparticles using the rhizome aqueous extract of R. rosea (G-AgNPs). We then studied their antioxidant activity and catalytic degradation of hazardous dye Direct Orange 26 (DO26) and Direct Blue 15 (DB15). Their effects on fluorescein's fluorescent properties were also evaluated. The chemical AgNPs (C-AgNPs) were synthesized by reducing solid sodium borohydride (NaBH₄), and its above activities were compared with those of G-AgNPs. The formation of G-AgNPs was confirmed by the appearance of brownish-gray color and the surface plasmon resonance (SPR) peak at 437 nm. The biogenic AgNPs were approximately 10 nm in size with a regular spherical shape identified from transmission electron microscopy (TEM) analysis. G-AgNPs exhibited significantly improved 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging activity than butylated hydroxytoluene (BHT) and C-AgNPs (p < 0.05). The biogenic G-AgNPs were also found to function as an effective green catalyst in reducing DO26 and DB15 by NaBH₄, which is superior to C-AgNPs. Furthermore, G-AgNPs showed better fluorescence enhancement activity than C-AgNPs, and the concentration required was lower. When the concentration of the G-AgNP solution was 64 nmol/L, the fluorescence intensity reached the maximum of 5460, with the fluorescence enhancement efficiency of 3.39, and the fluorescence activity was stable within 48 h. This study shows the efficacy of biogenic AgNPs in catalyzing the reduction of hazardous dye DO26 and DB15. Biogenic AgNPs could also be used as fluorescence enhancers in low concentrations.

Microbial cell factories a new dimension in bio-nanotechnology: exploring the robustness of nature

Bio-based nanotechnology has its existence in biological dimensions e.g. microbial cell factories (bacteria, fungi. algae, yeast, cyanobacteria) plants, and biopolymers. They provide multipurpose biological platforms to supply well-designed materials for diverse nano-biotechnological applications. The "green or bio-based synthesis of nanoparticles (NPs)" has witnessed a research outburst in the past decade. The bio-based synthesis of NPs using microbial cell factories is a benign process and requires mild conditions for the synthesis with end products being less/non-toxic. As a result, its application has extended in multitudinous industries including environment, cosmetics, and pharmaceutical. Thus, the present review summarizes all the significant aspects of nanotechnology and the reason to switch towards the bio-based synthesis of NPs using microbial cell factories. It consists of a detailed description of the bio-based methods employed for the synthesis and classification of NPs. Also, a comprehensive study on the application of bio-based NPs in the various industrial and biotechnological domains has been discussed. The limitation and its solution would help identify the applicability of NPs to "identified and unidentified" sectors.

Systematic Review on Biosynthesis of Silver Nanoparticles and Antibacterial Activities: Application and Theoretical Perspectives

The biosynthesis of silver nanoparticles and the antibacterial activities has provided enormous data on populations, geographical areas, and experiments with bio silver nanoparticles' antibacterial operation. Several peer-reviewed publications have discussed various aspects of this subject field over the last generation. However, there is an absence of a detailed and structured framework that can represent the research domain on this topic. This paper attempts to evaluate current articles mainly on the biosynthesis of nanoparticles or antibacterial activities utilizing the scientific methodology of big data analytics. A comprehensive study was done using multiple databases-Medline, Scopus, and Web of Sciences through PRISMA (i.e., Preferred Reporting Items for Systematic Reviews and Meta-Analyses). The keywords used included 'biosynthesis silver nano particles' OR 'silver nanoparticles' OR 'biosynthesis' AND 'antibacterial behavior' OR 'anti-microbial opposition' AND 'systematic analysis,' by using MeSH (Medical Subject Headings) terms, Boolean operator's parenthesis, or truncations as required. Since their effectiveness is dependent on particle size or initial concentration, it necessitates more research. Understanding the field of silver nanoparticle biosynthesis and antibacterial activity in Gulf areas and most Asian countries also necessitates its use of human-generated data. Furthermore, the need for this work has been highlighted by the lack of predictive modeling in this field and a need to combine specific domain expertise. Studies eligible for such a review were determined by certain inclusion and exclusion criteria. This study contributes to the existence of theoretical and analytical studies in this domain. After testing as per inclusion criteria, seven in vitro studies were selected out of 28 studies. Findings reveal that silver nanoparticles have different degrees of antimicrobial activity based on numerous factors. Limitations of the study include studies with low to moderate risks of bias and antimicrobial effects of silver nanoparticles. The study also reveals the possible use of silver nanoparticles as antibacterial irrigants using various methods, including a qualitative evaluation of knowledge and a comprehensive collection and interpretation of scientific studies.

Biosynthesis of Organic Nanocomposite Using Pistacia vera L. Hull: An Efficient Antimicrobial Agent

Here presented a quick and easy synthesis of copper nanoparticles (CuNPs). Pistachio hull extract has been used as a reducing and stabilizing agent in the preparation of CuNPs. This biosynthesis is a kind of supporter of the environment because chemical agents were not used to making nanoparticles, and on the other hand, it prevents the release of pistachio waste in nature and its adverse effects on nature. The biosynthesized CuNPs and CuNPs/silver Schiff base nanocomposite (CSS NC) were characterized by UV-VIS spectroscopy, Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), and energy-dispersive X-ray spectroscopy (EDS). CuNP and CSS NC antimicrobial activity was examined by both well diffusion and determination MIC methods against four bacteria Staphylococcus aureus, Bacillus cereus, Escherichia coli, and Pseudomonas aeruginosa and two fungi Aspergillus Niger and Candida albicans. CuNPs and CSS NC showed significant antimicrobial activity on the samples, preventing the growth of bacteria and fungi at very low concentrations. CuNPs and CSS NC had the greatest effect on Escherichia coli bacteria and Aspergillus niger fungi. Phenolic compounds are one of the most important antioxidants that are involved in various fields, including pharmacy. Pistacia vera hull is a rich source of phenolic compounds. In this study, the most phenolic compound in Pistacia vera hull is gallic acid and rutin, which has been identified by HPLC analysis. In this study, Pistacia vera hull essential oil analysis was performed by the GC-MS method, in which α-pinene, D-limonene, and isobornyl acetate compounds constitute the highest percentage of Pistacia vera hull essential oil.

Biogenic copper nanoparticles produced by using the Klebsiella pneumoniae strain NST2 curtailed salt stress effects in maize by modulating the cellular oxidative repair mechanisms

The negative effects of salinity on plant growth and physiology are well-established, which is one of the major threats to food security in semi-arid and arid regions of the world. The current research focuses on biosynthesis of copper nanoparticles (CuNPs) from a bacterial strain NST2, which was genetically identified as Klebsiella pneumoniae based on taxonomic identity of 16S rRNA gene. The strain was selected for bioprospecting of CuNPs owing to its Cu tolerance potential. The biologically-synthesized CuNPs were confirmed in culture by using ultraviolet visible spectroscopy. The material characteristics of green CuNPs were further investigated by using Fourier transform infrared spectroscopy, X-ray diffractometer, scanning electron microscopy and transmission electron microscopy, where crystallite size was ranged from 22.44 nm to 44.26 nm and particles were stabilized by various functional groups, such as carbonyl and amine groups. When 100 mg kg^-1 of green CuNPs were mixed in saline soil in a pot experiment, the maize plants showed increased root and shoot length (43.52% and 44.06%, respectively), fresh weight (46.05% and 51.82%, respectively) and dry weight (47.69% and 30.63%, respectively) in comparison to control maize plants without CuNPs application. Moreover, green CuNPs at their highest treatment level (100 mg kg^-1 of soil) counteracted the lipid peroxidation and oxidative damage in maize plants by promoting the activities of antioxidants and demoting the cellular levels of reactive oxygen species and ionic contents of Na⁺ and Cl^-. Conclusively, biogenic CuNPs is an emerging and promising technique, which could replace traditional methods of salinity management in agricultural soils.

Green Synthesis: An Eco-friendly Route for the Synthesis of Iron Oxide Nanoparticles

Green approach has received major attention for the synthesis of metal oxide nanoparticles. One such metal oxide nanoparticles are iron oxide nanoparticles (IONPs). IONPs have fetched a great deal of interest in recent era because of their magnetic nature, as they can be easily recovered from the reaction mixture by applying an external magnetic field. Although, a variety of chemical and physical methods of synthesis are known, green synthesis is safer, sustainable and biologically acceptable. Plants and microbes are the main biological materials used for the green synthesis. In present review, the synthesis of IONPs by using plants, bacteria, fungi and algae have been highlighted. IONPs produced by plants, fungi, bacteria and algae usually falls in 1–100 nm range and are of distinct shapes like cubic, tetragonal crystalline, spherical, cylindrical, elliptical, octahedral, orthorhombic, hexagonal rods, nanosphere and quasi spherical. Furthermore, these biomaterials play role of reducing, capping, stabilizing and fabricating agents in green synthesis of nanoparticles. The review put forward a comprehensive report of various routes used for synthesizing IONP, biologically. Intuition into the procedures for synthesis of nanoparticles will help to nourish our learning in the area of nanotechnology.

Nanotechnological Applications Based on Bacterial Encapsulins

Encapsulins are proteinaceous nanocontainers, constructed by a single species of shell protein that self-assemble into 20-40 nm icosahedral particles. Encapsulins are structurally similar to the capsids of viruses of the HK97-like lineage, to which they are evolutionarily related. Nearly all these nanocontainers encase a single oligomeric protein that defines the physiological role of the complex, although a few encapsulate several activities within a single particle. Encapsulins are abundant in bacteria and archaea, in which they participate in regulation of oxidative stress, detoxification, and homeostasis of key chemical elements. These nanocontainers are physically robust, contain numerous pores that permit metabolite flux through the shell, and are very tolerant of genetic manipulation. There are natural mechanisms for efficient functionalization of the outer and inner shell surfaces, and for the in vivo and in vitro internalization of heterologous proteins. These characteristics render encapsulin an excellent platform for the development of biotechnological applications. Here we provide an overview of current knowledge of encapsulin systems, summarize the remarkable toolbox developed by researchers in this field, and discuss recent advances in the biomedical and bioengineering applications of encapsulins.

Swarna Bindu Prashana-an Ancient Approach to Improve the Infant's Immunity

Swarna bindu prashana (SBP) is a metallic medicinal preparation widely used in Ayurveda pediatrics. The main ingredients of SBP are swarna prashan (gold nanoparticle), gou ghrita (cow ghee), madhu (honey), and other medhya dravyas (drugs which enhance intellectual, memory). According to the Indian classical text, SBP has been proposed as a potent medicine for immunotherapies and vaccine development due to its indefinite size, shapes, charges, and surface functionality. In this review, we describe the plausible mechanism of SBP in dendritic cells maturation and subsequent T cell activation. But being herbo-metallic preparation, its safety and efficacy are well supported by the classical publications of Ayurveda. To conclude, SBP is an immune booster for infants against any viral disease, and it is necessary to validate its safety and efficacy through systematic methodological research.

Biodegradable Chitosan Films with ZnO Nanoparticles Synthesized Using Food Industry By-Products—Production and Characterization

This work aimed to produce bionanocomposites of chitosan incorporated with zinc oxide nanoparticles (ZnO NPs) synthesized using food industry by-products and to characterize them. Such nanoparticles are highlighted due to their low cost, antimicrobial activity, accessibility, and sustainability synthesis. Four different levels of ZnO NPs (0, 0.5, 1.0, and 2.0% w/w of chitosan) were tested, and the bionanocomposites were characterized in terms of their hydrophobicity, mechanical, optical, and barrier properties. Overall, the incorporation of ZnO NPs changed the composites from brittle to ductile, with enhanced elongation at break and reduced Young Modulus and tensile strength. Thus, ZnO NPs acted as plasticizer, turning the films more flexible, due to the presence of organic compounds on the NPs. This also favored permeability of oxygen and of water vapor, but the good barrier properties were maintained. Optical properties did not change statistically with the ZnO NPs incorporation. Thus, the characterization presented in this paper may contribute to support a decision on the choice of the material’s final application.

A Review of the Use of Carbon Nanotubes and Graphene-Based Sensors for the Detection of Aflatoxin M1 Compounds in Milk

This paper presents a comprehensive review of the detection of aflatoxin compounds using carbon allotrope-based sensors. Although aflatoxin M1 and its derivative aflatoxin B1 compounds have been primarily found in milk and other food products, their presence above a threshold concentration causes disastrous health-related anomalies in human beings, such as growth impairment, underweight and even carcinogenic and immunosuppressive effects. Among the many sensors developed to detect the presence of these compounds, the employment of certain carbon allotropes, such as carbon nanotubes (CNTs) and graphene, has been highly preferred due to their enhanced electromechanical properties. These conductive nanomaterials have shown excellent quantitative performance in terms of sensitivity and selectivity for the chosen aflatoxin compounds. This paper elucidates some of the significant examples of the CNTs and graphene-based sensors measuring Aflatoxin M1 (ATM1) and Aflatoxin B1 (AFB1) compounds at low concentrations. The fabrication technique and performance of each of the sensors are shown here, as well as some of the challenges existing with the current sensors.

Lignin, lipid, protein, hyaluronic acid, starch, cellulose, gum, pectin, alginate and chitosan-based nanomaterials for cancer nanotherapy: Challenges and opportunities

Although nanotechnology-driven drug delivery systems are relatively new, they are rapidly evolving since the nanomaterials are deployed as effective means of diagnosis and delivery of assorted therapeutic agents to targeted intracellular sites in a controlled release manner. Nanomedicine and nanoparticulate drug delivery systems are rapidly developing as they play crucial roles in the development of therapeutic strategies for various types of cancer and malignancy. Nevertheless, high costs, associated toxicity and production of complexities are some of the critical barriers for their applications. Green nanomedicines have continually been improved as one of the viable approaches towards tumor drug delivery, thus making a notable impact on which considerably affect cancer treatment. In this regard, the utilization of natural and renewable feedstocks as a starting point for the fabrication of nanosystems can considerably contribute to the development of green nanomedicines. Nanostructures and biopolymers derived from natural and biorenewable resources such as proteins, lipids, lignin, hyaluronic acid, starch, cellulose, gum, pectin, alginate, and chitosan play vital roles in the development of cancer nanotherapy, imaging and management. This review uncovers recent investigations on diverse nanoarchitectures fabricated from natural and renewable feedstocks for the controlled/sustained and targeted drug/gene delivery systems against cancers including an outlook on some of the scientific challenges and opportunities in this field. Various important natural biopolymers and nanomaterials for cancer nanotherapy are covered and the scientific challenges and opportunities in this field are reviewed.

Nanomaterials in Wound Healing and Infection Control

Wounds continue to be a serious medical concern due to their increasing incidence from injuries, surgery, burns and chronic diseases such as diabetes. Delays in the healing process are influenced by infectious microbes, especially when they are in the biofilm form, which leads to a persistent infection. Biofilms are well known for their increased antibiotic resistance. Therefore, the development of novel wound dressing drug formulations and materials with combined antibacterial, antibiofilm and wound healing properties are required. Nanomaterials (NM) have unique properties due to their size and very large surface area that leads to a wide range of applications. Several NMs have antimicrobial activity combined with wound regeneration features thus give them promising applicability to a variety of wound types. The idea of NM-based antibiotics has been around for a decade at least and there are many recent reviews of the use of nanomaterials as antimicrobials. However, far less attention has been given to exploring if these NMs actually improve wound healing outcomes. In this review, we present an overview of different types of nanomaterials explored specifically for wound healing properties combined with infection control.

Amelioration of diethylnitrosamine (DEN) induced renal oxidative stress and inflammation by Carissa carandas embedded silver nanoparticles in rodents

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Phytofabricated silver nanoparticles (CCAgNPs) were biosynthesized and characterized.

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CCAgNPs were evaluated against diethylnitrosamine induced renal cancer.

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Silver nanoparticles have an antioxidant property.

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Silver nanoparticles unveiled a therapeutic effect against renal cancer in vivo.

Introduction

Inflammation and oxidative stress are the main factors ascribed with interruption in the process of renal tissue impairment. The toxicity of different types of nitrosamine is well recognized in animals and humans. Administration of the smallest quantities of diethylnitrosamine or dimethylnitrosamine either orally or parenterally results into renal damage. Therapeutic effects of phytofabricated silver nanoparticles of Carissa carandas aqueous extract has been scrutinised in current study for the assessment of renal cancer activity in animal model.

Methodology

Phytofabricated silver nanoparticles were characterized by using different instrumentation. Nephroprotective activity of silver nanoparticles at different doses was evaluated against N-diethylnitrosamine (200 mg/kg b.w., intraperitoneal) in animal model. Serum and renal homogenate were taken to evaluate the renal toxicity markers, oxidative stress, and antioxidant parameter, proinflammatory cytokines and histopathological study.

Result

Significant outcomes of silver nanoparticles in dose dependent manner down regulated the elevated serum marker, tumour marker enzymes and histopathology observation of repaired tissue assured the renal cancer activity in animals. In addition, profile of enzymatic and non-enzymatic antioxidant, proinflammatory cytokines and tumour promotion marker also favours the anticancer property of silver nanoparticles.

Conclusion

The data of current study reveals silver nanoparticles ameliorates renal oxidative stress and carcinogenesis which was induced by N-diethylnitrosamine and accredited to antioxidant and anticancer activities of phytofabricated nanoparticles by biological approach.

The Emerging Trend of Bio-Engineering Approaches for Microbial Nanomaterial Synthesis and Its Applications

Micro-organisms colonized the world before the multi-cellular organisms evolved. With the advent of microscopy, their existence became evident to the mankind and also the vast processes they regulate, that are in direct interest of the human beings. One such process that intrigued the researchers is the ability to grow in presence of toxic metals. The process seemed to be simple with the metal ions being sequestrated into the inclusion bodies or cell surfaces enabling the conversion into nontoxic nanostructures. However, the discovery of genome sequencing techniques highlighted the genetic makeup of these microbes as a quintessential aspect of these phenomena. The findings of metal resistance genes (MRG) in these microbes showed a rather complex regulation of these processes. Since most of these MRGs are plasmid encoded they can be transferred horizontally. With the discovery of nanoparticles and their many applications from polymer chemistry to drug delivery, the demand for innovative techniques of nanoparticle synthesis increased dramatically. It is now established that microbial synthesis of nanoparticles provides numerous advantages over the existing chemical methods. However, it is the explicit use of biotechnology, molecular biology, metabolic engineering, synthetic biology, and genetic engineering tools that revolutionized the world of microbial nanotechnology. Detailed study of the micro and even nanolevel assembly of microbial life also intrigued biologists and engineers to generate molecular motors that mimic bacterial flagellar motor. In this review, we highlight the importance and tremendous hidden potential of bio-engineering tools in exploiting the area of microbial nanoparticle synthesis. We also highlight the application oriented specific modulations that can be done in the stages involved in the synthesis of these nanoparticles. Finally, the role of these nanoparticles in the natural ecosystem is also addressed.

Silver Nanoparticle-Based Nanocomposites for Combating Infectious Pathogens: Recent Advances and Future Prospects

Silver nanoparticles (Ag NPs) and their nanocomposites with polymers are potent agents for antibacterial and disinfectant applications. The structural parameters of Ag-NPs, such as size, shape, and surface area, are very critical for developing appropriate formulations for the targeted applications. The impact of these factors on the performance of Ag NPs is analyzed. Ag NPs with a broad spectrum of antibacterial activities have already found applications in wound and burn dressing, food preservation, agricultural ponds, treatment for infected areas, coatings, water treatment, and other biomedical applications. Ag NPs are quite useful against antibiotic-resistant bacteria, but their level of toxicity needs careful investigation as their toxicity could be very harmful to human health and the environment. This review discusses the challenges and prospects of various Ag NPs and their composites. The review will enrich the knowledge about the efficiency and mechanism of various Ag nanoparticle-based antibacterial agents.

Bioreduction (AuIII to Au0) and stabilization of gold nanocatalyst using Kappa carrageenan for degradation of azo dyes

Colloidal gold nanoparticles (AuNPs) have been used in high technology applications due to their optical and electronic properties. Unfortunately, these broader applications are severely hampered by their agglomeration tendency and instability. Therefore, in this study, highly stable and aggregation resistant AuNPs were synthesized using Kappa carrageenan (κ-car) media (as a reducing and stabilizing agent) by a green synthesis protocol. The effect of different factors of reaction such as the concentration of κ-car (C_κ-car %), reaction time (t), temperature (T), and solution pH (here after simply define to 'reaction parameters') was studied by one-variable-at-a-time technique to optimize the yield production of AuNPs. The characterization of AuNPs synthesized at optimum conditions revealed that the particles are spherical in shapes, smaller in size (13.5 ± 5.1 nm) with a narrow distribution, highly crystalline (d-spacing = 0.230 nm) in nature, well stabilized (zeta potential = -22.1 mV) by coating by a thin layer of κ-car carbohydrate. The synthesized AuNPs reveal excellent catalytic function in the degradation (up to 99%) of azo-dyes. The kinetics study in the degradation reaction revealed that the technique could be extended to real wastewater treatment applications.

Determination of paracetamol using a sensor based on green synthesis of silver nanoparticles in plant extract

The biosynthesis of nanometals using a plant extract is simple, efficient, fast, cost-effective and eco-friendly. In this study, a pine nut extract (Araucaria angustifolia) was obtained and used as a reducing and stabilizing agent in the synthesis of silver nanoparticles. An electrochemical sensor based on the silver nanoparticles obtained and exfoliated graphite nanoplatelets applied to a glassy carbon electrode was developed for the determination of paracetamol. To optimize the synthesis of the silver nanoparticles, important factors such as temperature, extract:water ratio, silver nitrate concentration and extract stability time were studied. The factors influencing the performance of the sensor were studied in detail and the results demonstrated good repeatability and electrode-to-electrode repeatability (relative standard deviations of 1.8 and 4.0 %, respectively). Under optimized conditions, there was a linear response to paracetamol concentrations of 4.98 × 10^-6 to 3.38 × 10^-5 mol L^-1, with a detection limit of 8.50 × 10^-8 mol L^-1. No reports on the biosynthesis of AgNPs using Araucaria angustifolia could be found in the literature. The sensor developed showed good stability and was used successfully for the quantification of paracetamol in pharmaceutical products.

Green Synthesis of Silver Nanoparticles and Evaluation of Their Antibacterial Activity against Multidrug-Resistant Bacteria and Wound Healing Efficacy Using a Murine Model

Green nanotechnology has significant applications in various biomedical science fields. In this study, green-synthesized silver nanoparticles, prepared by using Catharanthus roseus and Azadirachta indica extracts, were characterized using UV-Vis spectroscopy, dynamic light scattering, X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. Silver nanoparticles (Ag NPs) synthesized from leaf extracts of C. roseus and A. indica effectively inhibited the growth of multidrug-resistant (MDR) bacteria isolated from patients with septic wound infections. The maximum bacteriolytic activity of the green-synthesized Ag NPs of C. roseus and A. indica against the MDR bacterium K. Pneumoniae was shown by a zone of inhibition of 19 and 16 mm, respectively. C. roseus Ag NPs exhibited more bacteriolytic activity than A. indica Ag NPs in terms of the zone of inhibition. Moreover, these particles were effective in healing wounds in BALB/c mice. Ag NPs of C. roseus and A. indica enhanced wound healing by 94% ± 1% and 87% ± 1%, respectively. Our data suggest that Ag NPs from C. roseus and A. indicia ameliorate excision wounds, and wound healing could be due to their effective antimicrobial activity against MDR bacteria. Hence, these Ag NPs could be potential therapeutic agents for the treatment of wounds.

Freshwater Clam as a Potential Bioindicator for Silver/Saponin Nanocomposites Toxicity

Despite the progress in using silver nano products in many fields, including medicine, food, and industry, their effects on the environment need more attention. Therefore, the current study aimed to assess the effect of silver/saponin nanocomposites (Ag/S NCs) for the first time on the aquatic environment by using freshwater clam, Caelatura aegyptiaca, as a fundamental bioindicator in the freshwater system. Following the preparation and characterization of Ag/S NCs by using atomic absorption spectrophotometer, UV-Vis spectrophotometer, X-ray diffraction, transmission electron microscopy, and acute toxicity study, we exposed the clam to three different doses of Ag/S NCs (12.5, 25 and 50 mg L^-1) for consecutive 6 days. All Ag/S NCs concentrations caused a significant increase in malondialdehyde and nitric oxide while induced a notable decrease in glutathione and catalase levels in all studied organs. Moreover, the histological alternations were observed in gills, labial palp, and foot tissues, particularly at dose 50 mg L^-1. From the results of our work, we concluded that toxicity of Ag/S NCs on freshwater clam leads to an oxidative stress response as well as histopathological changes. Besides, we assumed that Coelatura aegyptiaca could be used as a sensitive bioindicator for monitoring water pollution caused by different nanoparticles. Therefore, we do recommend performing further studies by using fresh clam to provide a better assessment for our aquatic environment to prevent water pollution locally and globally.

One-pot synthesis of natural amine-modified biocompatible carbon quantum dots with antibacterial activity

In the present study, the thermal decomposition of citric acid in the presence of biogenic amine was used to synthesize four different functionalized carbon quantum dots (CQDs), namely, histamine-(HCQDs), putrescine-(PCQDs), cadaverine-(CCQDs) and spermine-(SCQDs). The thermal decomposition of the precursors resulted in a decrease in stability and the formation of surface amides via a cross-linking process between the carboxyl and amine groups. The deposition of biogenic amines was confirmed by a structural characterization of the synthesized CQDs. The resulting CQDs, with a net zero charge, exhibited excellent stability in environments with different pH values. Through a set of different cytotoxicity tests, the absence of gene mutations, apoptosis, necrosis or disruption in cell membranes revealed the high biocompatibility of the CQDs. The antimicrobial activity of the synthesized CQDs was investigated against different bacterial species (Staphylococcus aureus, Escherichia coli, and Klebsiella pneumonia). We determined the growth kinetics, production of reactive oxygen species (ROS), cell viability and changes in membrane integrity by scanning electron microscopy (SEM). The minimal inhibitory concentrations (MICs) for S. aureus ranged from 3.4 to 6.9 µg/mL. Regarding E.coli and K. pneumonia, all CQD formulations reduced growth, and the MICs were determined for CCQDs and HCQDs (6.9-19.4 µg/mL). The antibacterial activity mechanism was attributed to the oxidative stress generated after CQD treatment, which resulted in the destabilization of the bacterial membrane. The bacterial permeability to propidium iodide indicated a change in membrane integrity, and the effect of CQDs on the morphology of the bacterial cells was evidenced by SEM.

Green synthesis and environmental application of iron-based nanomaterials and nanocomposite: A review

Green chemistry has been proven to be an efficient route for nanoparticle synthesis. Plant extract based green synthesis of various nanoparticles is extensively studied since the last decade. This paper "Green synthesis and environmental application of Iron-based nanomaterials and nanocomposite: A review" unveils all the possible greener techniques for the synthesis of iron-based nanoparticles and nanocomposites. The use of different plant sources, microorganisms, and various biocompatible green reagents such as biopolymers, cellulose, haemoglobin, and glucose for the synthesis of iron nanoparticles reported in the last decade are summarized. The microwave method, along with hydrothermal synthesis due to their lower energy consumption are also been referred to as a green route. Apart from different plant parts, waste leaves and roots used for the synthesis of iron nanoparticles are extensively briefed here. This review is thus compact in nature which covers all the broad areas of green synthesis of iron nanoparticles (NPs) and iron-based nanocomposites. Detailed discussion on environmental applications of the various green synthesized iron NPs and their composites with performance efficiency is provided in this review article. The advantages of bimetallic iron-based nanocomposites over iron NPs in various environmental applications are discussed in detail. The hazards and toxic properties of green synthesized iron-based NPs are compared with those obtained from chemical methods. The prospects and challenges section of this article provides a vivid outlook of adapting such useful technique into a more versatile process with certain inclusions which may encourage and provide a new direction to future research.

Cytotoxicity and insulin resistance reversal ability of biofunctional phytosynthesized MgO nanoparticles

The present study investigates the cytotoxicity of hexagonal MgO nanoparticles synthesized via Amaranthus tricolor leaf extract and spherical MgO nanoparticles synthesized via Amaranthus blitum and Andrographis paniculata leaf extracts. In vitro cytotoxicity analysis showed that the hexagonal MgO nanoparticles synthesized from A. tricolor extract demonstrated the least toxicity to both diabetic and non-diabetic cells at 600 μl/ml dosage. The viability of the diabetic cells (3T3-L1) after incubation with varying dosages of MgO nanoparticles was observed to be 55.3%. The viability of normal VERO cells was 86.6% and this stabilized to about 75% even after exposure to MgO nanoparticles dosage of up to 1000 μl/ml. Colorimetric glucose assay revealed that the A. tricolor extract synthesized MgO nanoparticles resulted in ~ 28% insulin resistance reversal. A reduction in the expression of GLUT4 protein at 54 KDa after MgO nanopaSrticles incubation with diabetic cells was observed via western blot analysis to confirm insulin reversal ability. Fluorescence microscopic analysis with propidium iodide and acridine orange dyes showed the release of reactive oxygen species as a possible mechanism of the cytotoxic effect of MgO nanoparticles. It was inferred that the synergistic effect of the phytochemicals and MgO nanoparticles played a significant role in delivering enhanced insulin resistance reversal capability in adipose cells.

Phyto-Engineered Gold Nanoparticles (AuNPs) with Potential Antibacterial, Antioxidant, and Wound Healing Activities Under in vitro and in vivo Conditions

Background

A diabetic ulcer is one of the major causes of illness among diabetic patients that involves severe and intractable complications associated with diabetic wounds. Hence, a suitable wound-healing agent is urgently needed at this juncture. Greener nanotechnology is a very promising and emerging technology currently employed for the development of alternative medicines. Plant-mediated synthesis of metal nanoparticles has been intensively investigated and regarded as an alternative strategy for overcoming various diseases and their secondary complications like microbial infections. Hence, we are interested in developing phyto-engineered gold nanoparticles as useful therapeutic agents for the treatment of infectious diseases and wounds effectively.

Methods and Results

We have synthesized phyto-engineered gold nanoparticles from the aqueous extract of Acalypha indica and characterized using advanced bio-analytical techniques. The surface plasmon resonance feature and crystalline behavior of gold nanoparticles were revealed by ultraviolet-visible spectroscopy and X-ray diffraction, respectively. High-performance liquid chromatography analysis of the extract demonstrated the presence of different constituents, while major functional groups were interpreted by the Fourier-transform infrared spectroscopy as the various stretching vibrations appeared for important O-H (3443 cm⁻¹), C=O (1644 cm⁻¹) and C-O (1395 cm⁻¹) groups. Scanning electron microscopy, high-resolution transmission electron microscopy results revealed a distribution of spherical and rod-like nanostructures with 20 nm of size. The gold nanoparticle-coated cotton fabric was evaluated for the antibacterial activity against Staphylococcus epidermidis and Escherichia coli bacterial strains which revealed remarkable inhibition at the zone of inhibition of 31 mm diameter against S. epidermidis. Further, antioxidant activity was tested for their free radical scavenging property, and the maximum antioxidant activity of the extract containing gold nanoparticles was found to be 80% at 100 µg/mL. The potent free radical scavenging property of the nanoparticles is observed at IC₅₀ value 16.25 µg/mL. Moreover, in vivo wound-healing activity was carried out using BALB/c mice model with infected diabetic wounds and observed the stained microscopic images at different time intervals (day 2, day 7 and day 15). It was noted that in 15 days, the wound area is completely re-epithelialized due to the presence of different morphologies such as spherical, needle and triangle nanoparticles. The re-epithelialization layer is fully covered by nanoparticles on the wound area and also collagen filled in the scar tissue when compared with the control group.

Conclusion

The pharmacological evaluation results of the study indicated an encouraging antibacterial and antioxidant activity of the greener synthesized gold nanoparticles tethered with aqueous extract of Acalypha indica. Moreover, we demonstrated enhanced in vivo wound-healing efficiency of the synthesized gold nanoparticles through the animal model. Thus, the outcome of this work revealed that the phyto-engineered gold nanoparticles could be useful for biomedical applications, especially in the development of promising antibacterial and wound-healing agents.

Recent Advances in Nanotechnology-Aided Materials in Combating Microbial Resistance and Functioning as Antibiotics Substitutes

The ongoing escalation of drug-resistant bacteria creates the leading challenges for human health. Current predictions show that deaths due to bacterial illness will be more in comparison to cancer in 2050. Irrational use of antibiotics, prolonged regimen and using as a prophylactic treatment for various infections are leading cause of microbial resistance. It is an emerging approach to introduce evolving nanomaterials (NMs) as a base of antibacterial therapy to overcome the bacterial resistance pattern. NMs can implement several bactericidal ways and turn into a challenge for bacteria to survive and develop resistance against NMs. All the pathways depend on the surface chemistry, shape, core material and size of NMs. Because of these reasons, NMs based stuff shows a critical role in advancing the treatment efficiency by interacting with the cellular system of bacteria and functioned as an antibiotic substitute. We divided this review into two sections. The first part highlights the development of microbial resistance to antibiotics and their mechanisms. The second section details the NMs mechanisms to combat antibiotic resistance. In short, we try to summarize the advances in NMs role to deal with microbial resistance and giving solution as antibiotics substitute.

Botanical insecticide-based nanosystems for the control of Aedes (Stegomyia) aegypti larvae

Aedes (Stegomyia) aegypti is a cosmopolitan species that transmits arbovirus of medical importance as dengue, Zika, and chikungunya. The main strategy employed for the control of this mosquito is the use of larvicidal agents. However, the overuse of synthetic chemical larvicides has led to an increase in resistant insects, making management difficult. Therefore, the use of botanical insecticide-based nanosystems as an alternative to the use of synthetic agents for the control of Ae. aegypti has gained more considerable attention in the last years, mainly due to the advantages of nanostructured delivery systems, such as (a) controlled release; (b) greater surface area; (c) improvement of biological activity; (d) protection of natural bioactive agents from the environment and thus achieving stability; and (e) lipophilic drugs are easier dispersed even in aqueous vehicles. This review summarizes the current knowledge about botanical insecticide-based nanosystems as larvicidal against Ae. aegypti larvae. The majority of papers used metallic nanoparticles (NPs) as larvicidal agents, mainly silver nanoparticles (AgNPs), showing potential for their use as an alternative, followed by nanoemulsions containing vegetable oils, most essential oils, nanosystems that allow the dispersion of this high hydrophobic product in water, the environment of larval development. The final section describes scientific findings about the mode of action of these NPs, showing the gap about this subject in literature.

Preparation, characterization and anti-cancer activity of graphene oxide-‑silver nanocomposite

This work reported the preparation, characterization, cytotoxicity of green synthesized Lespedeza cuneate mediated silver nanoparticles (Lc-AgNPs) and graphene oxide‑silver nanocomposite (GO-AgNComp) using Lc-AgNPs. The UV absorption spectrum at 419 nm indicated the successful formation of GO-AgNComp. The TEM analysis displayed the thin sheet of graphene decorated Lc-AgNPs in GO-AgNComp. Zeta potential was -13.2 mV for Lc-AgNPs and -30.5 mV for GO-AgNComp. The photothermal conversion efficiency was calculated as 31.09% for GO-AgNComp. The negatively charged zeta potential of GO-AgNComp enhanced its cellular penetration through enhanced permeability and retention (EPR) effect. The near-infrared laser (NIR) induced the anticancer activity of Lc-AgNPs and GO-AgNComp in human lung cancer cells (A549) and brain tumour (LN229). The results indicated that about 50% of A549 cells and LN229 cells were ablated by treatment of 24.73 ± 2.98 μg/mL and 27.34 ± 1.62 μg/mL of Lc-AgNPs, as well by 15.46 ± 2.31 μg/mL and 20.95 ± 1.35 μg/mL of GO-AgNComp respectively. Moreover, GO-AgNComp was not cytotoxic to normal mouse fibroblast cells (NIH3T3), but it caused the cancer cell death in A549 and LN229 through ROS generation, nuclear damage, and mitochondrial membrane potential (∆ψm) loss. This work reported the anticancer potential of GO-AgNComp, which deserves further study on the molecular elucidation of GO-AgNComp mediated human lung and tumour therapy.

A Sustainable Approach for the Green Synthesis of Silver Nanoparticles from Solibacillus isronensis sp. and Their Application in Biofilm Inhibition

The use of bacteria as nanofactories for the green synthesis of nanoparticles is considered a sustainable approach, owing to the stability, biocompatibility, high yields and facile synthesis of nanoparticles. The green synthesis provides the coating or capping of biomolecules on nanoparticles surface, which confer their biological activity. In this study, we report green synthesis of silver nanoparticles (AgNPs) by an environmental isolate; named as AgNPs1, which showed 100% 16S rRNA sequence similarity with Solibacillus isronensis. UV/visible analysis (UV/Vis), transmission electron microscopy (TEM), atomic force microscopy (AFM), dynamic light scattering (DLS), and Fourier-transform infrared spectroscopy (FTIR) were used to characterize the synthesized nanoparticles. The stable nature of nanoparticles was studied by thermogravimetric analysis (TGA) and inductively coupled plasma mass spectrometry (ICP-MS). Further, these nanoparticles were tested for biofilm inhibition against Escherichia coli and Pseudomonas aeruginosa. The AgNPs showed minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) values of 3.12 µg/mL and 6.25 µg/mL for E. coli, and 1.56 µg/mL and 3.12 µg/mL for P. aeruginosa, respectively.

Bacterial Synthesis of Ternary CdSAg Quantum Dots through Cation Exchange: Tuning the Composition and Properties of Biological Nanoparticles for Bioimaging and Photovoltaic Applications

In this study, we introduce a biological method for the production of ternary Quantum Dots (QDs): complex nanostructures with tunable optical and structural properties that utilizes post-synthesis modifications through cation exchange. This versatile in-situ cation exchange method being reported for the first time shows great potential for extending the scope of microbial synthesis. By using this bacterial-based method, we easily synthesize and purify CdS, CdSAg, and Ag₂S nanocrystals of a size below 15 nm and with variable morphologies that exhibit fluorescence emissions covering a broad spectral range (from 400 to 800 nm). Energy-dispersive X-ray spectroscopy (EDS) results indicate the partial replacement of Cd²⁺ by Ag⁺ when AgNO₃ concentration is increased. This replacement produces CdSAg ternary QDs hetero-structures with high stability, fluorescence in the NIR-I (700 - 800 nm), and 36.13% quantum yield. Furthermore, this reaction can be extended for the production of soluble Ag₂S nanoparticles (NPs) without any traces of Cd. QDs biosynthesized through this cation exchange process display very low toxicity when tested in bacterial or human cell lines. Biosynthesized ternary hetero-structures were used as red fluorescent dyes to label HeLa cells in confocal microscopy studies, which validates its use in bioimaging applications in the near infrared region. In addition, the application of biologically-produced cadmium NPs in solar cells is reported for the first time. The three biosynthesized QDs were successfully used as photosensitizers, where the CdSAg QDs show the best photovoltaic parameters. Altogether, obtained results validate the use of bacterial cells for the controlled production of nanomaterials with properties that allow their application in diverse technologies. We developed a simple biological process for obtaining tunable Quantum Dots (QDs) with different metal compositions through a cation exchange process. Nanoparticles (NPs) are produced in the extracellular space of bacterial cells exposed to cysteine and CdCl₂ in a reaction that depends on S²⁻ generation mediated by cysteine desulfhydrase enzymes and uses cellular biomolecules to stabilize the nanoparticle. Using this extracellular approach, water-soluble fluorescent CdS, CdSAg, and Ag₂S Quantum Dots with a tunable emission ranging from 400 to 800 nm were generated. This is the first study reporting the use of microorganisms to produce tunable ternary QDs and the first time that a cation exchange process mediated by cells is described. Obtained results validate the use of biological synthesis to produce NPs with new characteristics and opens a completely new research field related to the use of microorganisms to synthesize complex NPs that are difficult to obtain with regular chemical methods.

Biogenic metal nanoparticles as a potential class of antileishmanial agents: mechanisms and molecular targets

Leishmaniasis, a category 1 disease, has remained neglected for decades, and therefore, has developed into a severe health problem worldwide. Unfortunately, the available antileishmanial drugs are limited, and the parasites have shown an inevitable resistance toward most of these drugs. All these factors pose a barrier to control the parasite at present. Hence, new strategies are needed to develop more effective and less toxic nanomedicines that could treat and manage the Leishmania parasite. One of these effective strategies is to construct nanometals with biologically active molecules that could possess dynamic antileishmanial activities with desirable biocompatibility. In this review paper, antileishmanial potencies of different metal nanoparticles, with particular emphasis on biogenic metal nanoparticles from 2011 to 2019, are summarized. The mechanisms by which metal-based nanomedicines kill Leishmania are also discussed.

Bacterial Template Synthesis of Multifunctional Nanospindles for Glutathione Detection and Enhanced Cancer-Specific Chemo-Chemodynamic Therapy

Biological synthetic methods of nanoparticles have shown great advantages, such as environmental friendliness, low cost, mild reaction conditions, and enhanced biocompatibility and stability of products. Bacteria, as one of the most important living organisms, have been utilized as bioreducing nanofactories to biosynthesize many metal nanoparticles or compounds. Here, inspired by the disinfection process of KMnO₄, we for the first time introduce bacteria as both the template and the reducing agent to construct a novel tumor microenvironment-responsive MnO_x-based nanoplatform for biomedical applications in various aspects. It is found that the bacterium/MnO_x-based nanospindles (EM NSs) can efficiently encapsulate the chemotherapeutic agent doxorubicin (DOX), leading to the fluorescence quenching of the drug. The as-formed DOX-loaded EM NSs (EMD NSs) are proven to be decomposed by glutathione (GSH) and can simultaneously release DOX and Mn²⁺ ions. The former can be utilized for sensitive fluorescence-based GSH sensing with a limit of detection as low as 0.28 μM and selective cancer therapy, while the latter plays important roles in GSH-activated magnetic resonance imaging and chemodynamic therapy. We also demonstrate that these nanospindles can generate oxygen in the presence of endogenous hydrogen peroxide to inhibit P-glycoprotein expression under hypoxia and can achieve excellent tumor eradication and tumor metastasis inhibition performance. Taken together, this work designs a multifunctional bacterially synthesized nanomissile for imaging-guided tumor-specific chemo-chemodynamic combination therapy and will have implications for the design of microorganism-derived smart nanomedicines.

Exploiting the role of nanoparticle shape in enhancing hydrogel adhesive and mechanical properties

The ability to control nanostructure shape and dimensions presents opportunities to design materials in which their macroscopic properties are dependent upon the nature of the nanoparticle. Although particle morphology has been recognized as a crucial parameter, the exploitation of the potential shape-dependent properties has, to date, been limited. Herein, we demonstrate that nanoparticle shape is a critical consideration in the determination of nanocomposite hydrogel properties. Using translationally relevant calcium-alginate hydrogels, we show that the use of poly(L-lactide)-based nanoparticles with platelet morphology as an adhesive results in a significant enhancement of adhesion over nanoparticle glues comprised of spherical or cylindrical micelles. Furthermore, gel nanocomposites containing platelets showed an enhanced resistance to breaking under strain compared to their spherical and cylindrical counterparts. This study opens the doors to a change in direction in the field of gel nanocomposites, where nanoparticle shape plays an important role in tuning mechanical properties.

The ability to control nanostructure shape and dimensions presents opportunities to design materials in which their macroscopic properties are dependent upon the nature of the nanoparticle. Here the authors show nanoparticle shape is a critical consideration in the determination of nanocomposite hydrogel properties.

Use of biogenic copper nanoparticles synthesized from a native Escherichia sp. as photocatalysts for azo dye degradation and treatment of textile effluents

Textile wastewater contains a huge amount of azo dyes and heavy metals and catastrophically deteriorates the agricultural field by affecting its phyisco-chemical/biological and nutritional properties when directly drained to agricultural lands without any treatment. Recently, biogenic copper nanoparticles (CuNPs) have gained considerable attention for photocatalytic degradation of wastewater pollutants owing to their unique physico-chemical and biological properties, low cost and environmental sustainability. The current study reports the synthesis of CuNPs by a native copper-resistant bacterial strain Escherichia sp. SINT7 and evaluation of the photocatalytic activity of the biogenic CuNPs for azo dye degradation and treatment of textile effluents. Scanning electron microscopy and transmission electron microscopy revealed the spherical shape of biogenic CuNPs with particle size ranging from 22.33 to 39 nm. Moreover, X-ray diffraction data revealed that the CuNPs have spherical crystalline shapes with an average particle size of 28.55 nm. FTIR spectra showed the presence of coating proteins involved in the stabilization of nanomaterial. Azo dye degradation assays indicated that CuNPs decolorized congo red (97.07%), malachite green (90.55%), direct blue-1 (88.42%) and reactive black-5 (83.61%) at a dye concentration of 25 mg L^-1 after 5 h of sunlight exposure. However, at 100 mg L^-1 dye concentration, the degradation percentage was found to be 83.90%, 31.08%, 62.32% and 76.84% for congo red, malachite green, direct blue-1 and reactive black-5, respectively. Treatment of textile effluents with CuNPs resulted in a significant reduction in pH, electrical conductivity, turbidity, total suspended solids, total dissolved solids, hardness, chlorides and sulfates as compared to the non-treated samples. Thus, the promising dye detoxification and textile effluent recycling efficiency of biogenic CuNPs may lead to the development of eco-friendly and cost-efficient process for large-scale wastewater treatment.

Survival Mechanisms and Xenobiotic Susceptibility of Keratinocytes Exposed to Metal-Derived Nanoparticles

Metal-derived nanoparticles (Mt-NPs) are increasingly used in cosmetology due to their ultraviolet shielding (titanium dioxide [TiO₂]), antioxidant (cerium dioxide [CeO₂]), and biocidal (silver [Ag]) properties. In the absence of overt toxicity (i.e., cell death), Mt-NPs are considered safe for cosmetic applications. However, there is little understanding about the mechanisms involved in the survival of keratinocytes exposed to subtoxic levels of Mt-NPs. Human keratinocytes (HaCaT) were exposed subacutely to subtoxic concentrations (≤30 μg/mL, 48-72 h) of rutile (r) TiO₂ (cylindrical), CeO₂ (cubic) and Ag (spherical) with a core/hydrodynamic size of <50/<100 nm and >98% purity. Mt-NP uptake was indirectly quantified by changes in the light side scatter, where the kinetics (time/dose-response) suggested that the three types of Mt-NPs were similarly uptaken by keratinocytes. rTiO₂ and CeO₂, but not Ag-NPs, increased autophagy, whose inhibition prompted cell death. No increase in the steady-state levels of reactive oxygen species (ROS) was induced by exposure to any of the Mt-NPs tested. Interestingly, intracellular Ag-NP aggregates observed an increased far-red autofluorescence (≥740 nm em), which has been ascribed to their binding to thiol molecules such as glutathione (GSH). Accordingly, inhibition of GSH synthesis, but not the impairment of oxidized GSH recycling, sensitized keratinocytes to Ag-NPs suggesting that GSH homeostasis, and its direct scavenging of Ag-NPs, but not ROS, is essential for keratinocyte survival upon exposure to Ag-NP. rTiO₂ and Ag, but not CeO₂-NPs, compromised metabolic flux (glycolysis and respiration), but ATP levels were unaltered. Finally, we also observed that exposure to Mt-NPs sensitized keratinocytes to non-UV xenobiotic exposure (arsenite and paraquat). Our results demonstrate the differential contribution of autophagy and GSH homeostasis to the survival of human keratinocytes exposed to subtoxic concentrations of Mt-NPs and highlight the increased susceptibility of keratinocytes exposed to Mt-NPs to a second xenobiotic insult.