Cyanobacterial extract-mediated synthesis of silver nanoparticles and their application in ammonia sensing

Formation of plasmonic core/shell nanorods through ammonia-mediated dissolution of silver(i)oxide for ammonia monitoring

Due to the expansion of the aquaculture industry in the world and the importance of controlling ammonia in fish breeding water, high levels of which impose significant damage to fish farming, it is crucial to develop affordable, rapid, and on-site methods for timely and accurate detection of ammonia. In this study, a colorimetric sensor based on the formation of gold/silver core/shell nanorods (NRs) was developed for the rapid detection of ammonia. The sensor functioned by the specific dissolution of silver(i) oxide by ammonia, which triggered the activation of silver ions and the subsequent formation of gold/silver core/shell NRs in the presence of a reducing agent (i.e., ascorbic acid (AA)). This led to changes in the surface composition, size, and aspect ratio of the NRs, which was accompanied by a vivid color change from green to red/orange in less than a minute. The colorimetric sensor was optimized by adjusting the effective parameters, including ascorbic acid, silver ion, and sodium hydroxide concentration as well as pH and reaction time. After the optimization process, the sensor was found to have a linear range from 50 to 800 μmol L-1 (0.85-13.6 ppm). In addition, the application of the sensor was validated by measuring the ammonia content in water samples from rearing ponds for rainbow trout, sturgeon, and tilapia before and after feeding. The sensor's label-free, rapid, user-friendly, naked-eye, and cost-effective operation makes it an attractive option for on-site environmental monitoring of ammonia.

Bioinspired 5-caffeoylquinic acid capped silver nanoparticles using Coffee arabica leaf extract for high-sensitive cysteine detection

Selection of plant extracts as bioactive phytochemical source to synthesize nanoparticles is highly demanding due to the biocompatibility, nontoxicity, and cost-effectiveness over other available physical and chemical methods. Here, for the first time, Coffee arabica leaf extracts (CAE) were used to produce highly stable silver nanoparticles (AgNPs) and the corresponding bio reduction, capping and stabilization mechanism mediated by dominant isomer 5-caffeoylquinic acid (5-CQA) is discussed. UV-Vis, FTIR, μRaman spectroscopy, TEM, DLS and Zeta potential analyzer measurements were employed to characterize these green synthesized NPs. The affinity of 5-CQA capped CAE-AgNPs to thiol moiety of amino acid is utilized for the selective as well as sensitive detection of L-cysteine (L-Cys) to a low detection limit of 0.1 nM, as obtained from its μRaman spectra. Hence, the proposed novel, simple, eco-friendly, and economically sustainable method can provide a promising nanoplatform in the field of biosensors compliant with large-scale industrial production of AgNPs without aid of further instrumentation.

Plant nanobionics: Fortifying food security via engineered plant productivity

The world's human population is increasing exponentially, increasing the demand for high-quality food sources. As a result, there is a major global concern over hunger and malnutrition in developing countries with limited food resources. To address this issue, researchers worldwide must focus on developing improved crop varieties with greater productivity to overcome hunger. However, conventional crop breeding methods require extensive periods to develop new varieties with desirable traits. To tackle this challenge, an innovative approach termed plant nanobionics introduces nanomaterials (NMs) into cell organelles to enhance or modify plant function and thus crop productivity and yield. A comprehensive review of nanomaterials affect crop yield is needed to guide nanotechnology research. This article critically reviews nanotechnology applications for engineering plant productivity, seed germination, crop growth, enhancing photosynthesis, and improving crop yield and quality, and discusses nanobionic approaches such as smart drug delivery systems and plant nanobiosensors. Moreover, the review describes NM classification and synthesis and human health-related and plant toxicity hazards. Our findings suggest that nanotechnology application in agricultural production could significantly increase crop yields to alleviate global hunger pressures. However, the environmental risks associated with NMs should be investigated thoroughly before their widespread adoption in agriculture.

Bioremediation of Hazardous Wastes Using Green Synthesis of Nanoparticles

Advanced agronomic methods, urbanisation, and industrial expansion contaminate air, water and soil, globally. Agricultural and industrial activities threaten living biota, causing biodiversity loss and serious diseases. Strategies such as bioremediation and physiochemical remediation have not been effectively beneficial at treating pollutants. Metal-based nanoparticles (NPs) such as copper, zinc, silver, gold, etc., in various nanoformulations and nanocomposites are used more and more as they effectively resist the uptake of toxic compounds via plants by facilitating their immobilisation. According to studies, bio-based NP synthesis is a recent and agroecologically friendly approach for remediating environmental waste, which is effective against carcinogens, heavy metal contamination, treating marine water polluted with excessive concentrations of phosphorus, nitrogen and harmful algae, and hazardous dye- and pesticide-contaminated water. Biogenic resources such as bacteria, fungi, algae and plants are extensively used for the biosynthesis of NPs, particularly metallic NPs. Strategies involving green synthesis of NPs are nontoxic and could be employed for commercial scale production. Here, the focus is on the green synthesis of NPs for reduction of hazardous wastes to help with the clean-up process.

Photosynthetic microbes in nanobiotechnology: Applications and perspectives

Photosynthetic microbes like brown algae, red algae, green-algae and blue-green algae (cyanobacteria) are utilized extensively for various commercial and industrial purposes. However, in recent time, their application has shifted to nanotechnology. The synthesis of metal nanoparticles using algal resources is known as Phyconanotechnology. Due to various advantages of the photosynthetic microbes such as presence of bioactive molecules, scalability, high metal uptake and cultivability, these microbes form ideal sources for nanoparticle synthesis. The green synthesis of nanoparticles is a non-toxic and environment-friendly alternative compared to other hazardous chemical and physical routes of synthesis. Several species of algae are explored for the fabrication of metal and metal oxide nanoparticles. Various physical characterization techniques collectively contribute in defining the surface morphology of nanoparticles and the existing functional groups for bioreduction and stability. A wide range of nanostructured metals like gold, silver, copper, zinc, iron, platinum and palladium are fabricated using algae and cyanobacteria. Due to the unique properties of the phycogenic nanoparticles, biocompatibility and safety aspects, all of these metal nanoparticles have their applications in facets like infection control, diagnosis, drug delivery, biosensing and bioremediation. Herein, the uniqueness of the phycogenic nanoparticles along with their distinctive antibacterial, antifungal, antibiofilm, algaecidal, antiviral, anticancer, antioxidant, antidiabetic, dye degradation, metal removal and catalytic properties are featured. Lastly, this work highlights the various challenges and future perspectives for further exploration of the biogenic metal nanoparticles for development of nanomedicine and environmental remediation in the coming years.

Green Synthesis and Characterization of Silver Nanoparticles with High Antibacterial Activity Using Cell Extracts of Cyanobacterium Pseudanabaena/Limnothrix sp

In this work, we demonstrated the ability of the cyanobacterium Pseudanabaena/Limnothrix sp. to produce ultra-small silver nanoparticlesin the forms of metallic silver (Ag0) and silver oxides (AgxOy) via a facile green synthetic process. The biological compounds in the cyanobacterial cellular extract acted both as reducing agents for silver ions and functional stabilizing agents for the silver nanoparticles. Furthermore, the antibacterical activity of the as-synthesized nanoparticles against Gram-negative Escherichia coli and Gram-positive Corynebacterium glutamicum bacterial cells was evaluated. The experimental results revealed a remarkable bactericidal activity of the nanoparticles that was both time-dependent and dose-dependent. In addition to their excellent bactericidal properties, the developed nanoparticles can be used as nanosupports in various environmental, biological, and medical applications.

Fabrication of robust silver plated conductive polyamide fibres based on tannic acid modification

A novel method for the preparation of silver plated conductive polyamide fibres (PA/Ag) based on tannic acid modification was reported in this work. The highly adhesive tannic acid was grafted onto the surface of sulphuric acid roughened polyamide fibres to sensitize the fibre. Then, the sensitized polyamide fibres were activated by low-concentration silver nitrate to form reactive centers. Chemical silver plating was finally carried out using silver ammonia solution with glucose. The surface morphology and chemical properties of the prepared polyamide fibres were analyzed and the surface resistance, fastness to washing, thermal decomposition properties, electrothermal properties, sensing properties and practical applications of the silver-plated polyamide fibres were also tested. The test results show that the prepared conductive fibres have excellent conductivity and stability, and have potential applications in flexible electronic devices and sensing fields.

Recent progression of cyanobacteria and their pharmaceutical utility: an update

Cyanobacteria (blue-green algae) are Gram-negative photosynthetic eubacteria that are found everywhere. This largest group of photosynthetic prokaryotes is rich in structurally novel and biologically active compounds; several of which have been utilized as prospective drugs against cancer and other ailments, as well. Consequently, the integument of nanoparticles-synthetic approaches in cyanobacterial extracts should increase pharmacological activity. Moreover, silver nanoparticles (AgNPs) are small materials with diameters below 100 nm that are classified into different classes based on their forms, sizes, and characteristics. Indeed, the biosynthesized AgNPs are generated with a variety of organisms, algae, plants, bacteria, and a few others, for the medicinal purposes, as the bioactive compounds of curio and some proteins from cyanobacteria have the potentiality in the treatment of a wide range of infectious diseases. The critical focus of this review is on the antimicrobial, antioxidant, and anticancer properties of cyanobacteria. This would be useful in the pharmaceutical industries in the future drug development cascades.Communicated by Ramaswamy H. Sarma.

Arthrospira platensis-Mediated Green Biosynthesis of Silver Nano-particles as Breast Cancer Controlling Agent: In Vitro and In Vivo Safety Approaches

Biogenic silver nanoparticles (bio-AgNPs) is one of the most fascinating nanomaterials used for several biomedical purposes. In the current study, we biosynthesized AgNPs (bio-AgNPs) using Arthrospira platensis (A-bio-AgNPs), Microcystis aeruginosa (M-bio-AgNPs), and Chlorella vulgaris (C-bio-AgNPs) active metabolites and evaluated their anticancer efficacy against breast cancer. The recovered bio-AgNPs were characterized using scanning and transmission electron microscopy (SEM and TEM). In addition, their safety profiles were monitored in vitro on PBMCs cells and in vivo on Albino mice. The obtained results indicated the safety usage of bio-AgNPs at concentrations of 0.1 mg/ml on PBMCs cells and 1.5 mg/ml on the Albino mice. The bio-AgNPs displayed dose-dependent cytotoxic effects against HepG-2, CaCO-2, and MCF-7 cell lines by inducing reactive oxygen species (ROS) and arresting the treated cells in G0/G1 and sub G0 phases. In addition, A-bio-AgNPs induced breast cancer cellular apoptosis by downregulating the expression of survivin, MMP7, TGF, and Bcl2 genes. Upon A-bio-AgNPs treatment, a significant reduction in tumor growth and prolonged survival rates were recorded in breast cancer BALB/c model. Furthermore, A-bio-AgNPs treatment significantly decreased the Ki-67 protein marker from 60% (in the untreated group) to 20% (in the treated group) and increased caspase-3 protein levels to 65% (in treated groups) comparing with 45% (in doxorubicin-treated groups).

Cyanobacteria as biochemical energy source for the synthesis of inorganic nanoparticles, mechanism and potential applications: a review

Green synthesis of nanoparticles (NPs) has gained great concern among researchers due to their unique properties, excellent applications and efficient route of synthesis. From the last decades, the number biologicals such as plants, fungus, bacteria, yeast, algae, and cyanobacteria and their products are using by various researchers for the synthesis of different NPs. However, the pillar of green chemistry keeps touching new heights to improve the performance. This review paper unveils almost recent cyanobacteria-assisted greener NP synthesis technique, characterization and application. The enormous potency of cyanobacteria in NP synthesis (silver, gold, copper, zinc, palladium, titanium, cadmium sulfide, and selenium) and significance of reducing enzymes were summarized. The extracellular and intracellular entity such as metabolites, enzyme, protein, pigments in cyanobacteria play a significant role in the conversion of metal ions to metal NPs with unique properties discussed briefly. The green synthesis of nanomaterials is valuable because of their cost-effective, nontoxic and eco-friendly prospects as well as the potential application metal NPs such as antibacterial, antifungal, anticancerous, catalytic, drug delivery, bioimaging, nanopesticide, nanofertilizer, sensing properties, etc. Therefore, in the present review, we have systematically discussed the mechanisms of synthesis and applications of cyanobacteria-assisted green synthesis of NPs.

Biosynthesis of Metal Nanoparticles via Microbial Enzymes: A Mechanistic Approach

During the last decade, metal nanoparticles (MtNPs) have gained immense popularity due to their characteristic physicochemical properties, as well as containing antimicrobial, anti-cancer, catalyzing, optical, electronic and magnetic properties. Primarily, these MtNPs have been synthesized through different physical and chemical methods. However, these conventional methods have various drawbacks, such as high energy consumption, high cost and the involvement of toxic chemical substances. Microbial flora has provided an alternative platform for the biological synthesis of MtNPs in an eco-friendly and cost effective way. In this article we have focused on various microorganisms used for the synthesis of different MtNPs. We also have elaborated on the intracellular and extracellular mechanisms of MtNP synthesis in microorganisms, and have highlighted their advantages along with their challenges. Moreover, due to several advantages over chemically synthesized nanoparticles, the microbial MtNPs, with their exclusive and dynamic characteristics, can be used in different sectors like the agriculture, medicine, cosmetics and biotechnology industries in the near future.