Screening of cyanobacteria and microalgae for their ability to synthesize silver nanoparticles with antibacterial activity

Light-mediated biosynthesis of size-tuned silver nanoparticles using Saccharomyces cerevisiae extract

Bio-based production of silver nanoparticles represents a sustainable alternative to commercially applied physicochemical manufacturing approaches and provides qualitatively highly valuable nanomaterials due to their narrow size dispersity, high stability and biocompatibility with broad application potentials. The intrinsic features of nanoparticles depend on size and shape, whereby the controlled synthesis is a challenging necessity. In the present study, the biosynthesis of size-tuned silver nanoparticles based on cell-free extracts of Saccharomyces cerevisiae DSM 1333 was investigated. Single parameter optimization strategies in phases of cultivation, extraction, and synthesis were performed to modify the nanoparticle scale and yield. Visible light was exploited as a tool in nanoparticle production. The influence of white light on the biosynthesis of silver nanoparticles was determined by using novel LED systems with the exposition of varying irradiation intensities and simultaneous performance of control experiments in the dark. Characterization of the resulting nanomaterials by spectrophotometric analysis, dynamic light scattering, scanning electron microscopy, and energy dispersive X-ray spectroscopy, revealed spherical silver nanoparticles with controlled, light-mediated size shifts in markedly increased quantities. Matching of irradiated and non-irradiated reaction mixtures mirrored the enormous functionality of photon input and the high sensitivity of the biosynthesis process. The silver nanoparticle yields increased by more than 90% with irradiation at 1.0 ± 0.2 mW cm - 2 and the reduction of particle dimensions was achieved with significant shifts of size-specific absorption maxima from 440 to 410 nm, corresponding to particle sizes of 130 nm and 100 nm, respectively. White light emerged as an excellent tool for nano-manufacturing with advantageous effects for modulating unique particle properties.

In vitro assessment of the effect of magnetic fields on efficacy of biosynthesized selenium nanoparticles by Alborzia kermanshahica

Cyanobacteria represent a rich resource of a wide array of unique bioactive compounds that are proving to be potent sources of anticancer drugs. Selenium nanoparticles (SeNPs) have shown an increasing potential as major therapeutic platforms and led to the production of higher levels of ROS that can present desirable anticancer properties. Chitosan-SeNPs have also presented antitumor properties against hepatic cancer cell lines, especially the Cht-NP (Chitosan-NPs), promoting ROS generation and mitochondria dysfunction. It is proposed that magnetic fields can add new dimensions to nanoparticle applications. Hence, in this study, the biosynthesis of SeNPs using Alborzia kermanshahica and chitosan (CS) as stabilizers has been developed. The SeNPs synthesis was performed at different cyanobacterial cultivation conditions, including control (without magnetic field) and magnetic fields of 30 mT and 60 mT. The SeNPs were characterized by uv-visible spectroscopy, Fourier-transform infrared spectroscopy (FT-IR), Dynamic light scattering (DLS), zeta potential, and TEM. In addition, the antibacterial activity, inhibition of bacterial growth, minimum inhibitory concentration (MIC), and minimum bactericidal concentration (MBC), as well as the antifungal activity and cytotoxicity of SeNPs, were performed. The results of uv-visible spectrometry, DLS, and zeta potential showed that 60 mT had the highest value regarding the adsorption, size, and stabilization in compared to the control. FTIR spectroscopy results showed consistent spectra, but the increased intensity of peaks indicates an increase in bond number after exposure to 30 mT and 60 mT. The results of the antibacterial activity and the inhibition zone diameter of synthesized nanoparticles showed that Staphylococcus aureus was more sensitive to nanoparticles produced under 60 mT. Se-NPs produced by Alborzia kermanshahica cultured under a 60 mT magnetic field exhibit potent antimicrobial and anticancer properties, making them a promising natural agent for use in the pharmaceutical and biomedical industries.

Properties and potential applications of bioconjugates of R-phycoerythrin with Ag° or CdS nanoparticle synthesized in its tunnel cavity: A review

Green synthesis is a promising method for the preparation of nanoparticles (NPs) due to its simplicity, low cost, low toxicity, and environmental friendliness. Biosynthesized NPs exhibit multifunctional activity, good biocompatibility, and higher anticancer and antibacterial activity compared to chemically synthesized NPs. R-phycoerythrin, a photosynthetic light-harvesting pigment of protein nature (M.w. 290 kDa), is an attractive platform for the synthesis of small sizes NPs due to its structural features, non-toxicity, water solubility. Photosensitive bioconjugates of R-phycoerythrin with NPs were prepared by synthesizing Ag° and CdS NPs in tunnel cavities of R-phycoerythrin (3.5 × 6.0 nm) isolated from the red seaweed Callithamnion rubosum. The review is devoted to the physical processes and chemical reactions that occur in the native protein macromolecule of a complex structure during the synthesis of a NP in its cavity. The influence of Ago and CdS NPs on the electronic processes caused by the absorption of photons, leading to reversible and irreversible changes in R-phycoerythrin has been analyzed. Properties of R-phycoerythrin bioconjugates Ag° and CdS with NPs combined with the literature data suggest potential applications of Ag°⋅PE and CdS⋅PE bioconjugates for cancer diagnosis, treatment, and monitoring as well as for realizing theranostic strategy in the future. The use of these bioconjugates in anticancer therapy may have synergistic effects since both R-phycoerythrin and NPs induce cancer cell death.

Green Synthesis of Silver Nanoparticles Using the Cell-Free Supernatant of Haematococcus pluvialis Culture

The green synthesis of silver nanoparticles (AgNPs) using the cell-free supernatant of a Haematococcus pluvialis culture (CFS) was implemented in the current study, under illumination conditions. The reduction of Ag+ to AgNPs by the CFS could be described by a pseudo-first-order kinetic equation at the temperature range tested. A high reaction rate during synthesis and stable AgNPs were obtained at 45 °C, while an alkaline pH (pH = 11.0) and a AgNO3 aqueous solution to CFS ratio of 90:10 (v/v) proved to be the most effective conditions in AgNPs synthesis. A metal precursor (AgNO3) at the concentration range tested (1-5 mM) was the limited reactant in the synthesis process. The synthesis of AgNPs was accomplished under static and agitated conditions. Continuous stirring enhanced the rate of reaction but induced aggregation at prolonged incubation times. Zeta potential and polydispersity index measurements indicated stable AgNPs and the majority of AgNPs formation occurred in the monodisperse phase. The X-ray diffraction (XRD) pattern revealed the face-centered cubic structure of the formed AgNPs, while TEM analysis revealed that the AgNPs were of a quasi-spherical shape with a size from 30 to 50 nm. The long-term stability of the AgNPs could be achieved in darkness and at 4 °C. In addition, the synthesized nanoparticles showed antibacterial activity against Escherichia coli.

Microalga Broths Synthesize Antibacterial and Non-Cytotoxic Silver Nanoparticles Showing Synergy with Antibiotics and Bacterial ROS Induction and Can Be Reused for Successive AgNP Batches

The era of increasing bacterial antibiotic resistance requires new approaches to fight infections. With this purpose, silver-based nanomaterials are a reality in some fields and promise new developments. We report the green synthesis of silver nanoparticles (AgNPs) using culture broths from a microalga. Broths from two media, with different compositions and pHs and sampled at two growth phases, produced eight AgNP types. Nanoparticles harvested after several synthesis periods showed differences in antibacterial activity and stability. Moreover, an evaluation of the broths for several consecutive syntheses did not find relevant kinetics or activity differences until the third round. Physicochemical characteristics of the AgNPs (core and hydrodynamic sizes, Z-potential, crystallinity, and corona composition) were determined, observing differences depending on the broths used. AgNPs showed good antibacterial activity at concentrations producing no or low cytotoxicity on cultured eukaryotic cells. All the AgNPs had high levels of synergy against Escherichia coli and Staphylococcus aureus with the classic antibiotics streptomycin and kanamycin, but with ampicillin only against S. aureus and tetracycline against E. coli. Differences in the synergy levels were also dependent on the types of AgNPs. We also found that, for some AgNPs, the killing of bacteria started before the massive accumulation of ROS.

ZnO nanostructured matrix as nexus catalysts for the removal of emerging pollutants

Water pollution stands as a pressing global environmental concern, elevating the significance of innovative, dependable, and sustainable solutions. This study represents an extensive review of the use of photocatalytic zinc oxide nanoparticles (ZnO NPs) for the removal of emerging pollutants from water and wastewater. The study examines ZnO NPs' different preparation methods, including physical, chemical, and green synthesis, and emphasizes on advantages, disadvantages, preparation factors, and investigation methods for the structural and morphological properties. ZnO NPs demonstrate remarkable properties as photocatalysts; however, their small dimensions pose an issue, leading to potential post-use environmental losses. A strategy to overcome this challenge is scaling up ZnO NP matrices for enhanced stability and efficiency. The paper introduces novel ZnO NP composites, by incorporating supports like carbon and clay that serve as photocatalysts in the removal of emerging pollutants from water and wastewater. In essence, this research underscores the urgency of finding innovative, efficient, and eco-friendly solutions for the removal of emerging pollutants from wastewater and highlights the high removal efficiencies obtained when using ZnO NPs obtained from green synthesis as a photocatalyst. Future research should be developed on the cost-benefit analysis regarding the preparation methods, treatment processes, and value-added product regeneration efficiency.

Recent progression on phytochemicals and pharmacological properties of the filamentous cyanobacterium Lyngbya sp

The distribution and phytochemistry of the non-nitrogen fixing, filamentous cyanobacterium (blue-green alga) Lyngbya sp., and the inherent antimicrobial and anticancer activities of its phycochemicals as well as of the biosynthesized nanoparticles as their pharmaceutical potencies are considered. Several phycocompounds of curio, apramide, apratoxin, benderamide, cocosamides, deoxymajusculamide, flavonoids, lagunamides, lipids, proteins, amino acids, lyngbyabellin, lyngbyastatin, majusculamide, peptides, etc. were isolated from Lyngbya sp., which had a lot of potential pharmaceutical activities; those compounds had antibacterial, antiviral, antifungal, anticancer, antioxidant, anti-inflammatory, ultraviolet protectant, and other activities. Particularly, several Lyngbya phycocompounds had potent antimicrobial potencies, seen through in vitro controlling of several frequently encountered multidrug-resistant (MDR) clinically belligerent strains of pathogenic bacteria isolated from clinical samples. The aqueous extracts of Lyngbya sp. were used for the synthesis of silver and copper oxide nanoparticles, which were used in pharmacological trials too. The nanoparticles biosynthesized with Lyngbya sp. had several uses such as biofuel, agro-based applications, in cosmetics, and industrial uses as biopolymers, and being potent antimicrobial and anticancer agents and in drug-delivery too, as medical applications. It could be concluded that the Lyngbya phycochemicals and the biosynthesized nanoparticles have future uses as antimicrobial namely as bacterial and fungal and anti-cancer agents, with promising medical and industrial uses.

Photosynthesis-Mediated Intracellular Biomineralization of Gold Nanoparticles inside Chlorella Cells towards Hydrogen Boosting under Green Light

Engineering living microorganisms to enhance green biomanufacturing for the development of sustainable and carbon-neutral energy strategies has attracted the interest of researchers from a wide range of scientific communities. In this study, we develop a method to achieve photosynthesis-mediated biomineralization of gold nanoparticles (AuNPs) inside Chlorella cells, where the photosynthesis-dominated reduction of Au3+ to Au0 allows the formed AuNPs to locate preferentially around the thylakoid membrane domain. In particular, we reveal that the electrons generated by the localized surface plasmon resonance of AuNPs could greatly augment hypoxic photosynthesis, which then promotes the generation and transferring of photoelectrons throughout the photosynthetic chain for augmented hydrogen production under sunlight. We demonstrate that the electrons from AuNPs could be directly transferred to hydrogenase, giving rise to an 8.3-fold enhancement of Chlorella cells hydrogen production independent of the cellular photosynthetic process under monochromatic 560 nm light irradiation. Overall, the photosynthesis-mediated intracellular biomineralization of AuNPs could contribute to a novel paradigm for functionalizing Chlorella cells to augment biomanufacturing.

Differential Antimicrobial Effect of Three-Sized Biogenic Silver Nanoparticles as Broad-Spectrum Antibacterial Agents against Plant Pathogens

BACKGROUND

Massive fruit losses are caused by microbial pathogens of unknown identities. Therefore, ecofriendly biocontrol measures are well sought after, and biogenic silver nanoparticles are plausible candidates. Here we investigate the antimicrobial effect of three different sized AgNPs samples on those pathogens.

METHODOLOGY

Identities of three local pathogenic bacteria were investigated using molecular methods. Three different-sized samples of silver nanoparticles were bio-synthesized in the external solution of a cyanobacterial culture, characterized, and used in antimicrobial bioassay.

RESULTS

The pathogens were identified as Erwinia pyrifoliae, Staphylococcus warneri, and Xanthomonas citri. UV-vis. and FTIR spectroscopy confirmed the biosynthesis of AgNPs. and their three different sizes were confirmed using Scanning electron microscopy. Growth of bacterial pathogens was inhibited by all three samples of AgNPs, but the largest inhibition zone was for the smallest sized AgNPs against Staphylococcus warneri (1.7 cm).

DISCUSSION

The identity of the pathogens infecting different local fruits is reported for the first time. They belong to different bacterial lineages. The fact that biogenic AAgNPs were effective against all of them shows their broad-spectrum of antibacterial effect. Customized biosynthesis was successful in yielding different-sized AgNPs. The smaller the AgNPs, the stronger the antimicrobial impact.

CONCLUSION

Local bacterial species infecting fruits are diverse. Customized biogenic AgNPs are effective broad-spectrum biocontrol agents against bacterial pathogens of local fruits and thereby help maintain food security and environmental sustainability.

Characterization of Silver Nanoparticle Systems from Microalgae Acclimated to Different CO2 Atmospheres

Green synthesis of metallic nanoparticles using microalgae exposed to high CO₂ atmospheres has not been studied in detail; this is of relevance in biological CO₂ mitigation systems where considerable biomass is produced. In this study, we further characterized the potential of an environmental isolate Desmodesmus abundans acclimated to low and high CO₂ atmospheres [low carbon acclimation (LCA) and high carbon acclimation (HCA) strains, respectively] as a platform for silver nanoparticle (AgNP) synthesis. As previously characterized, cell pellets at pH 11 were selected from the biological components tested of the different microalgae, which included the culture collection strain Spirulina platensis. AgNP characterization showed superior performance of strain HCA components as preserving the supernatant resulted in synthesis in all pH conditions. Size distribution analysis evidenced strain HCA cell pellet platform (pH 11) as the most homogeneous AgNP population (14.9 ± 6.4 nm diameter, -32.7 ± 5.3 mV) followed by S. platensis (18.3 ± 7.5 nm, -33.9 ± 2.4 mV). In contrast, strain LCA presented a broader population where the size was above 100 nm (127.8 ± 14.8 nm, -26.7 ± 2.4 mV). Fourier-transform infrared and Raman spectroscopies showed that the reducing power of microalgae might be attributed to functional groups in the cell pellet from proteins, carbohydrates, and fatty acids and, in the supernatant, from amino acids, monosaccharides, disaccharides, and polysaccharides. Microalgae AgNPs exhibited similar antimicrobial properties in the agar diffusion test against Escherichia coli. However, they were not effective against Gram (+) Lactobacillus plantarum. It is suggested that a high CO₂ atmosphere potentiates components in the D. abundans strain HCA for nanotechnology applications.

Green synthesized silver nanoparticles for iron and manganese ion removal from aqueous solutions

Microalgae and Cyanobacteria extracts can be used for the synthesis of spherical silver nanoparticles by the reduction of AgNO₃ under air atmosphere at room temperature. Here, we synthesized AgNPs using extracts of one cyanobacterium (Synechococcus elongatus) and two microalgae (Stigeoclonium sp. and Cosmarium punctulatum). The nature of the AgNPs was characterized by TEM, HR-TEM, EDS, and UV-Vis. Considering the large quantity of functional groups in the ligands of AgNPs, we suppose they could retain ion metals, which would be useful for water decontamination. Thus, their capacity to adsorb iron and manganese at concentrations of 1.0, 5.0, and 10.0 mg L^-1 in aqueous solutions was evaluated. All experiments were performed in triplicate of microorganism extract with no addition of AgNO₃ (control) and AgNP colloid (treatment) at room temperature. The ICP analyses showed that the treatments containing nanoparticles were commonly more efficient at removing Fe³⁺ and Mn²⁺ ions than the corresponding controls. Interestingly, the smaller nanoparticles (synthesized by Synechococcus elongatus) were the most effective at removing Fe³⁺ and Mn²⁺ ions, probably due to their higher surface area:volume ratio. The green synthesized AgNPs proved to be an interesting system for the manufacture of biofilters that could be used to capture contaminant metals in water.

Nanoparticles from Microalgae and Their Biomedical Applications

Over the years, microalgae have been a source of useful compounds mainly used as food and dietary supplements. Recently, microalgae have been used as a source of metabolites that can participate in the synthesis of several nanoparticles through inexpensive and environmentally friendly routes alternative to chemical synthesis. Notably, the occurrence of global health threats focused attention on the microalgae application in the medicinal field. In this review, we report the influence of secondary metabolites from marine and freshwater microalgae and cyanobacteria on the synthesis of nanoparticles that were applied as therapeutics. In addition, the use of isolated compounds on the surface of nanoparticles to combat diseases has also been addressed. Although studies have proven the beneficial effect of high-value bioproducts on microalgae and their potential in medicine, there is still room for understanding their exact role in the human body and translating lab-based research into clinical trials.

Updates on Biogenic Metallic and Metal Oxide Nanoparticles: Therapy, Drug Delivery and Cytotoxicity

The ambition to combat the issues affecting the environment and human health triggers the development of biosynthesis that incorporates the production of natural compounds by living organisms via eco-friendly nano assembly. Biosynthesized nanoparticles (NPs) have various pharmaceutical applications, such as tumoricidal, anti-inflammatory, antimicrobials, antiviral, etc. When combined, bio-nanotechnology and drug delivery give rise to the development of various pharmaceutics with site-specific biomedical applications. In this review, we have attempted to summarize in brief the types of renewable biological systems used for the biosynthesis of metallic and metal oxide NPs and the vital contribution of biogenic NPs as pharmaceutics and drug carriers simultaneously. The biosystem used for nano assembly further affects the morphology, size, shape, and structure of the produced nanomaterial. The toxicity of the biogenic NPs, because of their pharmacokinetic behavior in vitro and in vivo, is also discussed, together with some recent achievements towards enhanced biocompatibility, bioavailability, and reduced side effects. Because of the large biodiversity, the potential biomedical application of metal NPs produced via natural extracts in biogenic nanomedicine is yet to be explored.

Cyanoremediation and phyconanotechnology: cyanobacteria for metal biosorption toward a circular economy

Cyanobacteria are widespread phototrophic microorganisms that represent a promising biotechnological tool to satisfy current sustainability and circularity requirements. They are potential bio-factories of a wide range of compounds that can be exploited in several fields including bioremediation and nanotechnology sectors. This article aims to illustrate the most recent trends in the use of cyanobacteria for the bioremoval (i.e., cyanoremediation) of heavy metals and metal recovery and reuse. Heavy metal biosorption by cyanobacteria can be combined with the consecutive valorization of the obtained metal-organic materials to get added-value compounds, including metal nanoparticles, opening the field of phyconanotechnology. It is thus possible that the use of combined approaches could increase the environmental and economic feasibility of cyanobacteria-based processes, promoting the transition toward a circular economy.

Plant and Microbial Approaches as Green Methods for the Synthesis of Nanomaterials: Synthesis, Applications, and Future Perspectives

The unique biological and physicochemical characteristics of biogenic (green-synthesized) nanomaterials (NMs) have attracted significant interest in different fields, with applications in the agrochemical, food, medication delivery, cosmetics, cellular imaging, and biomedical industries. To synthesize biogenic nanomaterials, green synthesis techniques use microorganisms, plant extracts, or proteins as bio-capping and bio-reducing agents and their role as bio-nanofactories for material synthesis at the nanoscale size. Green chemistry is environmentally benign, biocompatible, nontoxic, and economically effective. By taking into account the findings from recent investigations, we shed light on the most recent developments in the green synthesis of nanomaterials using different types of microbes and plants. Additionally, we cover different applications of green-synthesized nanomaterials in the food and textile industries, water treatment, and biomedical applications. Furthermore, we discuss the future perspectives of the green synthesis of nanomaterials to advance their production and applications.

Biomedical Applications of Biosynthesized Gold Nanoparticles from Cyanobacteria: an Overview

Recently there had been a great interest in biologically synthesized nanoparticles (NPs) as potential therapeutic agents. The shortcomings of conventional non-biological synthesis methods such as generation of toxic byproducts, energy consumptions, and involved cost have shifted the attention towards green syntheses of NPs. Among noble metal NPs, gold nanoparticles (AuNPs) are the most extensively used ones, owing to the unique physicochemical properties. AuNPs have potential therapeutic applications, as those are synthesized with biomolecules as reducing and stabilizing agent(s). The green method of AuNP synthesis is simple, eco-friendly, non-toxic, and cost-effective with the use of renewable energy sources. Among all taxa, cyanobacteria have attracted considerable attention as nano-biofactories, due to cellular uptake of heavy metals from the environment. The cellular bioactive pigments, enzymes, and polysaccharides acted as reducing and coating agents during the process of biosynthesis. However, cyanobacteria-mediated AuNPs have potential biomedical applications, namely, targeted drug delivery, cancer treatment, gene therapy, antimicrobial agent, biosensors, and imaging.

Phytosynthesis of Zinc Oxide Nanoparticles Using Ceratonia siliqua L. and Evidence of Antimicrobial Activity

Carob (Ceratonia siliqua L.) is a tree crop cultivated extensively in the eastern Mediterranean regions but that has become naturalized in other regions as well. The present study focused on the green synthesis of zinc oxide nanoparticles (ZnONPs) from Carob and their evaluation for antimicrobial activity in bacteria and fungi. The synthesized ZnONPs showed strong antibacterial activity against Staphylococcus aureus ATCC 25 923 (92%). The NPs inhibited the growth of pathogenic yeast strains, including Candida albicans ATCC90028, Candida krusei ATCC6258, and Candida neoformans ATCC14116, by 90%, 91%, and 82%, respectively, compared to the control. Fungal inhibition zones with the ZnONPs were 88.67% and 90%, respectively, larger for Aspergillus flavus 15UA005 and Aspergillus fumigatus ATCC204305, compared to control fungal growth. This study provides novel information relevant for plant-based development of new and potentially antimicrobial ZnONPs based on extracts. In particular, the development and application of phytogenic nanoparticles enhances the biocompatibility of nano-scale materials, thereby allowing to tune effects to prevent adverse outcomes in non-target biological systems.

Biomedical Applications of Plant Extract-Synthesized Silver Nanoparticles

Silver nanoparticles (AgNPs) have attracted a lot of interest directed towards biomedical applications due in part to their outstanding anti-microbial activities. However, there have been many health-impacting concerns about their traditional synthesis methods, i.e., the chemical and physical methods. Chemical methods are commonly used and contribute to the overall toxicity of the AgNPs, while the main disadvantages of physical synthesis include high production costs and high energy consumption. The biological methods provide an economical and biocompatible option as they use microorganisms and natural products in the synthesis of AgNPs with exceptional biological properties. Plant extract-based synthesis has received a lot of attention and has been shown to resolve the limitations associated with chemical and physical methods. AgNPs synthesized using plant extracts provide a safe, cost-effective, and environment-friendly approach that produces biocompatible AgNPs with enhanced properties for use in a wide range of applications. The review focused on the use of plant-synthesized AgNPs in various biomedical applications as anti-microbial, anti-cancer, anti-inflammatory, and drug-delivery agents. The versatility and potential use of green AgNPs in the bio-medicinal sector provides an innovative alternative that can overcome the limitations of traditional systems. Thus proving green nanotechnology to be the future for medicine with continuous progress towards a healthier and safer environment by forming nanomaterials that are low- or non-toxic using a sustainable approach.

Enhancement of Arthrospira sp. culturing for sulfate removal and mining wastewater bioremediation

Sulfate content in mining wastewater can reach concentrations over 2,000 mg·L^-1, which is considered as a pollutant of concern. In this article, two cyanobacteria species were cultured using highly sulfated wastewater (3,000 mg·L^-1) as the culture medium. This investigation aimed to analyze the sulfate bioremediation potential of microalgae while enhancing the uptaking of this pollutant through the design of a novel nutritional medium. The results obtained show the suitability of Arthrospira maxima as a bioremediation organism of sulfated wastewater. The appropriateness of this organism is based on its great growth performance when cultured in this residue, 2.16 times higher than the initial value. Moreover, the initially obtained sulfate reduction, 23.3%, was significantly enhanced to a final removal of 73% (2,247 mg·L^-1). In addition, scanning electron microscopy and energy-dispersive X-ray spectroscopy were used to evaluate sulfur crystallization. To the best of our knowledge, there are no previous works focused on microalgal sulfate removal that have reached such an uptaking rate. Accordingly, this study presents the highest performance on sulfate microalgal bioremediation published to date. Our findings suggest that A. maxima can be cultured for sulfated wastewater bioremediation while showing a removal yield that is theoretically sufficient for industrial applications.

New Green Approaches in Nanoparticles Synthesis: An Overview

Nanotechnology is constantly expanding, with nanomaterials being more and more used in common commercial products that define our modern life. Among all types of nanomaterials, nanoparticles (NPs) occupy an important place, considering the great amount that is produced nowadays and the diversity of their applications. Conventional techniques applied to synthesize NPs have some issues that impede them from being appreciated as safe for the environment and health. The alternative to these might be the use of living organisms or biological extracts that can be involved in the green approach synthesis of NPs, a process that is free of harmful chemicals, cost-effective and a low energy consumer. Several factors, including biological reducing agent concentration, initial precursor salt concentration, agitation, reaction time, pH, temperature and light, can influence the characteristics of biologically synthesized NPs. The interdependence between these reaction parameters was not explored, being the main impediment in the implementation of the biological method on an industrial scale. Our aim is to present a brief review that focuses on the current knowledge regarding how the aforementioned factors can control the size and shape of green-synthesized NPs. We also provide an overview of the biomolecules that were found to be suitable for NP synthesis. This work is meant to be a support for researchers who intend to develop new green approaches for the synthesis of NPs.

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.

Prospects and environmental sustainability of phyconanotechnology: A review on algae-mediated metal nanoparticles synthesis and mechanism

In recent years, researchers have proven that the employment of natural green components in the biogenesis of nanoparticles from microalgae species is one of the ways to delight the global environment issues. The application of nanotechnology with the exploitation of phycochemical produced from algae species is known as 'phyconanotechnology'. The use of biological compounds by microalgae as reducing agents for the synthesis of inorganic nanoparticles has shown promising results such as cost-effective and environmentally friendly. Different classifications of algae such as brown algae, red algae, green algae, and cyanobacteria are studied for the synthesis of different types of metal nanoparticles. It is also an important motive to acknowledge the mechanisms of the microalgae-mediated biosynthesis of nanoparticles via an intracellular pathway or extracellular pathway. Besides, microalgae species as biogenic sources preclude the use of conventional methods reagents, such as sodium borohydride (NaBH₄) and N,N-dimethylformamide (DMF), which further consolidates their position as the best choice for sustainable (economically and environmentally) nanoparticle synthesis compared to the conventional nanoparticles synthesis pathway.

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 (Ag_xO_y) 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.

Cyanobacteria: miniature factories for green synthesis of metallic nanomaterials: a review

Nanotechnology is one of the most promising and advanced disciplines of science that deals with synthesis, characterization and applications of different types of Nanomaterials (NMs) viz. nanospheres, nanoparticles, nanotubes, nanorods, nanowires, nanocomposites, nanoalloys, carbon dots and quantum dots. These nanosized materials exhibit different physicochemical characteristics and act as a whole unit during its transport. The unique characteristics and vast applications of NMs in diverse fields viz. electronics, agriculture, biology and medicine have created huge demand of different type of NMs. Conventionally physical and chemical methods were adopted to manufacture NMs which are expensive and end up with hazardous by-products. Therefore, green synthesis exploiting biological resources viz. algae, bacteria, fungi and plants emerged as a better and promising alternative due to its cost effective and ecofriendly approach and referred as nanobiotechnology. Among various living organisms, cyanobacteria have proved one of the most favourable bioresources for NMs biosynthesis due to their survival in diverse econiches including metal and metalloid contaminated sites and capability to withstand high levels of metals. Biosynthesis of metallic NMs is accomplished through bioreduction of respective metal salts by various capping agents viz. alkaloids, pigments, polysaccharides, steroids, enzymes and peptides present in the biological systems. Advancement in the field of Nanobiotechnology has produced large number of diverse NMs from cyanobacteria which have been used as antimicrobial agents against Gram positive and negative human pathogens, anticancer agents, luminescent nanoprobes for imaging of cells, antifungal agents against plant pathogens, nanocatalyst and semiconductor quantum dots in industries and in bioremediation in toxic pollutant dyes. In the present communication, we have reviewed cyanobacteria mediated biosynthesis of NMs and their applications in various 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.

Green Metallic Nanoparticles: Biosynthesis to Applications

Current advancements in nanotechnology and nanoscience have resulted in new nanomaterials, which may pose health and environmental risks. Furthermore, several researchers are working to optimize ecologically friendly procedures for creating metal and metal oxide nanoparticles. The primary goal is to decrease the adverse effects of synthetic processes, their accompanying chemicals, and the resulting complexes. Utilizing various biomaterials for nanoparticle preparation is a beneficial approach in green nanotechnology. Furthermore, using the biological qualities of nature through a variety of activities is an excellent way to achieve this goal. Algae, plants, bacteria, and fungus have been employed to make energy-efficient, low-cost, and nontoxic metallic nanoparticles in the last few decades. Despite the environmental advantages of using green chemistry-based biological synthesis over traditional methods as discussed in this article, there are some unresolved issues such as particle size and shape consistency, reproducibility of the synthesis process, and understanding of the mechanisms involved in producing metallic nanoparticles via biological entities. Consequently, there is a need for further research to analyze and comprehend the real biological synthesis-dependent processes. This is currently an untapped hot research topic that required more investment to properly leverage the green manufacturing of metallic nanoparticles through living entities. The review covers such green methods of synthesizing nanoparticles and their utilization in the scientific world.

Recent Advances and Mechanistic Insights into Antibacterial Activity, Antibiofilm Activity, and Cytotoxicity of Silver Nanoparticles

The substantial increase in multidrug-resistant (MDR) pathogenic bacteria is a major threat to global health. Recently, the Centers for Disease Control and Prevention reported possibilities of greater deaths due to bacterial infections than cancer. Nanomaterials, especially small-sized (size ≤10 nm) silver nanoparticles (AgNPs), can be employed to combat these deadly bacterial diseases. However, high reactivity, instability, susceptibility to fast oxidation, and cytotoxicity remain crucial shortcomings for their uptake and clinical application. In this review, we discuss various AgNPs-based approaches to eradicate bacterial infections and provide comprehensive mechanistic insights and recent advances in antibacterial activity, antibiofilm activity, and cytotoxicity (both in vitro and in vivo) of AgNPs. The mechanistic of antimicrobial activity involves four steps: (i) adhesion of AgNPs to cell wall/membrane and its disruption; (ii) intracellular penetration and damage; (iii) oxidative stress; and (iv) modulation of signal transduction pathways. Numerous factors affecting the bactericidal activity of AgNPs such as shape, size, crystallinity, pH, and surface coating/charge have also been described in detail. The review also sheds light on antimicrobial photodynamic therapy and the role of AgNPs versus Ag⁺ ions release in bactericidal activities. In addition, different methods of synthesis of AgNPs have been discussed in brief.

Cyanobacterial biorefinery: Towards economic feasibility through the maximum valorization of biomass

Cyanobacteria are well known for their plethora of applications in the fields of food industry, pharmaceuticals and bioenergy. Their simple growth requirements, remarkable growth rate and the ability to produce a wide range of bio-active compounds enable them to act as an efficient biorefinery for the production of valuable metabolites. Most of the cyanobacteria based biorefineries are targeting single products and thus fails to meet the efficient valorization of biomass. On the other hand, multiple products recovering cyanobacterial biorefineries can efficiently valorize the biomass with minimum to zero waste generation. But there are plenty of bottlenecks and challenges allied with cyanobacterial biorefineries. Most of them are being associated with the production processes and downstream strategies, which are difficult to manage economically. There is a need to propose new solutions to eliminate these tailbacks so on to elevate the cyanobacterial biorefinery to be an economically feasible, minimum waste generating multiproduct biorefinery. Cost-effective approaches implemented from production to downstream processing without affecting the quality of products will be beneficial for attaining economic viability. The integrated approaches in cultivation systems as well as downstream processing, by simplifying individual processes to unit operation systems can obviously increase the economic feasibility to a certain extent. Low cost approaches for biomass production, multiparameter optimization and successive sequential retrieval of multiple value-added products according to their high to low market value from a biorefinery is possible. The nanotechnological approaches in cyanobacterial biorefineries make it one step closer to the goal. The current review gives an overview of strategies used for constructing self-sustainable- economically feasible- minimum waste generating; multiple products based cyanobacterial biorefineries by the efficient valorization of biomass. Also the possibility of uplifting new cyanobacterial strains for biorefineries is discussed.

Green approaches in synthesising nanomaterials for environmental nanobioremediation: Technological advancements, applications, benefits and challenges

Green synthesis approaches of nanomaterials (NMs) have received considerable attention in recent years as it addresses the sustainability issues posed by conventional synthesis methods. However, recent works of literature do not present the complete picture of biogenic NMs. This paper addresses the previous gaps by providing insights into the stability and toxicity of NMs, critically reviewing the various biological agents and solvents required for synthesis, sheds light on the factors that affect biosynthesis, and outlines the applications of NMs across various sectors. Despite the advantages of green synthesis, current methods face challenges with safe and appropriate solvent selection, process parameters that affect the synthesis process, nanomaterial cytotoxicity, bulk production and NM morphology control, tedious maintenance, and knowledge deficiencies. Consequently, the green synthesis of NMs is largely trapped in the laboratory phase. Nevertheless, the environmental friendliness, biocompatibility, and sensitivities of the resulting NMs have wider applications in biomedical science, environmental remediation, and consumer industries. To the scale-up application of biogenic NMs, future research should be focused on understanding the mechanisms of the synthesis processes, identifying more biological and chemical agents that can be used in synthesis, and developing the practicality of green synthesis at the industrial scale, and optimizing the factors affecting the synthesis process.

Sargassum myriocystum-mediated TiO2-nanoparticles and their antimicrobial, larvicidal activities and enhanced photocatalytic degradation of various dyes

Recently, the phyco-synthesis of nanoparticles has been applied as a reliable approach to modern research field, and it has yielded a wide spectrum of diverse uses in fields such as biological science and environmental science. This study used marine natural resource seaweed Sargassum myriocystum due to their unique phytochemicals and their significant attributes in giving effective response on various biomedical applications. The response is created by their stress-tolerant environmental adaptations. This inspired us to make an attempt using the above-mentioned charactersitics. Therfore, the current study performed phycosynthesis of titanium dioxide nanoparticles (TiO2-NPs) utilising aqueous extracts of S. myriocystum. The TiO2-NPs formation was confirmed in earlier UV-visible spectroscopy analysis. The crystalline structure, functional groups (phycomolecules), particle morphology (cubic, square, and spherical), size (∼50-90 nm), and surface charge (negative) of the TiO2-NPs were analysed and confirmed by various characterisation analyses. In addition, the seaweed-mediated TiO2-NPs was investigated, which showed potential impacts on antibacterial activity and anti-biofilm actions against pathogens (Staphylococcus aureus, S. epidermidis, Escherichia coli, Proteus vulgaris, Pseudomonas aeruginosa, and Klebsiella pneumoniae). Additionally, some evaluations were performed on larvicidal activities of TiO2-NPs in oppose to Aedes aegypti and Culex quinquefasciatus mosquitos and the environmental effects of photocatalytic activities against methylene blue and crystal violet under sunlight irradiation. The highest percent of methylene blue degradation was observed at 92.92% within 45 min. Overall, our findings suggested that S. myriocystum mediates TiO2-NPs to be a potent disruptive material for bacterial pathogens and mosquito larvae and also to enhance the photocatalytic dye degradation.

Biosynthesis and Characterization of Silver Nanoparticles Produced by Phormidium ambiguum and Desertifilum tharense Cyanobacteria

The world faces a challenge with the pervasion of multidrug-resistant bacteria that encourages scientists to develop and discover alternative, ecofriendly, and easy-to-produce new antibacterial agents. Our work is part of the greater effort of scientists around the world to achieve this goal by the biological synthesis of silver nanoparticles using cyanobacterial extracellular and intracellular components as nonchemical reducing agents. Two Egyptian cyanobacteria were isolated and identified according to 16S rRNA gene sequencing as Phormidium ambiguum and a novel species Desertifilum tharense. The sequences were deposited with accession numbers MW762709 and MW762710 for Desertifilum tharense and Phormidium ambiguum, respectively, in the GenBank. The results of UV-Vis analysis showed promising extracellular Ag-NPs synthesis by Desertifilum tharense and Phormidium ambiguum under light conditions. Therefore, these Ag-NPs were characterized and evaluated for antibacterial and antioxidant activity. TEM and SEM analyses revealed the spherical crystals with face-centered cubic structures and size range of 6.24-11.4 nm and 6.46-12.2 nm for Ag-NPs of Desertifilum tharense and Phormidium ambiguum, respectively. XRD and EDX results confirmed the successful synthesis of Ag-NPs in their oxide form or chloride form. The FTIR spectrum data confirmed the presence of hydroxyl and amide groups. Desertifilum tharense Ag-NPs displayed the largest inhibition zone that ranged from 9 mm against Micrococcus luteus ATCC 10240 to 25 mm against methicillin-resistant Staphylococcus aureus (MRSA) ATCC 43300. For Phormidium ambiguum Ag-NPs, the inhibition zone diameter was in the range of 9 mm to 18 mm. The biosynthesized Ag-NPs significantly inhibited the growth of medically important resistance-pathogenic Gram-positive and Gram-negative bacteria. The Ag-NPs of Phormidium ambiguum exhibited the highest scavenging activity of 48.7% when compared with that of Desertifilum tharense, which displayed 43.753%.

Silver Nanoparticle Production by the Cyanobacterium Cyanothece sp.: De Novo Manipulation of Nano-Biosynthesis by Phytohormones

Background: Numerous cyanobacteria have the potential to reduce metallic ions to form pure metal nanoparticles in a green biosynthesis process. Aim: To investigate the production capacity of silver nanoparticles by the cyanobacterium Cyanothece sp. and to examine the effect of five different phytohormones, indole acetic acid, kinetin; gibberellic acid; abscisic acid; and methyl jasmonate, on this capacity. Methods: The cyanobacterial strain was grown for 60 days and the harvested cyanobacterium biomass was incubated with 0.1 mM of AgNO₃. Percentage conversion of Ag⁺ to Ag⁰ was calculated to indicate the AgNPs’ production capacity. Different concentrations of the five phytohormones were added to cultures and the AgNP production was monitored throughout different time intervals. Results: Cyanothece sp. biosynthesized spherical AgNPs (diameter range 70 to 140 nm, average diameter 84.37 nm). The addition of indole acetic acid and kinetin provoked the maximum conversion (87.29% and 55.16%, respectively) of Ag⁺ to Ag⁰, exceeding or slightly below that of the control (56%). Gibberellic and abscisic acids failed to elevate the Ag⁺ to Ag⁰ conversion rate (45.23% and 47.95%, respectively) above that of the control. Methyl jasmonate increased the Ag⁺ to Ag⁰ conversion rate to 90.29%, although nearly all the cyanobacterial cultures died at the end. Conclusion: Phytohormones could be used to induce or inhibit the green production of AgNPs with the cyanobacterium Cyanothece sp. This novel manipulation technique may have several applications in agriculture or biomedicine.

Nano-reduction of gold and silver ions: A perspective on the fate of microbial laccases as potential biocatalysts in the synthesis of metals (gold and silver) nano-particles

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Potential involvements of microbial laccases in the synthesis of silver and gold nanoparticles have been comprehensively assessed.

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Treasured roles of microbes and associated enzymes in synthesis of gold and silver nanoparticles have also been presented.

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As potential green biocatalysts for the synthesis of metal nanoparticles, microbial laccases may be promisingly used.

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Methodologies as well as involved possible mechanisms have been discussed in details in order to disclose the effectiveness of microbial laccases in the synthesis of gold and silver nanoparticles.

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Different characterization results of synthesized gold and silver nanoparticles based on UV–Vis spectra, XRD, SEM, TEM and other techniques have also been discussed.

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Mechanistic evaluation also shows a hope for the effectiveness of microbial laccases in the synthesis of other metal nanoparticles.

Nanoparticles of metals have momentous place in the field of biological as well as pharmaceutical chemistry due to which in the present scenario of the research, this field is of auspicious interest. Synthesis of metal nanoparticles via microbial assistance is a burning field for their green synthesis. In this direction, microbial enzymes play significant role, out of which microbial laccases may also be a talented biocatalyst for the synthesis of metal nanoparticles considering its efficacy and interesting promising biological applications. A very little works are known on the role of microbial laccases in the synthesis of metal nanoparticles but after effective scrutiny of their reported works on the synthesis of gold and silver nanoparticles, its fate as potential biocatalyst in the synthesis of metals nanoparticles is being automatically established. Thus, this perspective commendably appraises the active applicability of microbial laccases in the synthesis of gold and silver nanoparticles by reducing their ions in suitable reaction environment.

Investigating the Production of Antimicrobial Nanoparticles by Chlorella vulgaris and the Link to Its Loss of Viability

Chlorella vulgaris from Al-Ahsa, KSA was proved to be an active silver and gold nanoparticle producer. Nanogold and nanosilver particles were characterized using UV-visible spectroscopy, Fourier-transform infrared spectroscopy, and scanning electronmicroscopy. Both nanoparticles were used in the antimicrobial bioassay. The two nanoparticles showed antibacterial activities, with the silver nanoparticles being the most effective. To investigate the argumentative nature of their biosynthesis (i.e., whether it is a biotic or abiotic process), we isolated total ribonucleic acid RNA as an indicator of vitality. RNA was completely absent in samples taken after one week of incubation with silver nitrate and even after one or two days. However, successful extraction was only achievable in samples taken after incubation for one and four hours with silver nitrate. Most importantly, the gel image showed recognizable shearing of the nucleic acid after 4 h as compared to the control. An assumption can be drawn that the synthesis of nanoparticles may start biotically by the action of enzyme(s) and abiotically by action of reducing entities. Nonetheless, with prolonged incubation, excessive nanoparticle accumulation can be deadly. Hence, their synthesis continues abiotically. From the RNA banding profile, we suggest that nanosilver production starts both biotically and abiotically in the first few hours of incubation and then continues abiotically. Nanosilver particles proved to have more of an antimicrobial impact than nanogold and hence are recommended for different applications as antibacterial agents.

Synthesis, Characterization and Biomedical Application of Silver Nanoparticles

Silver nanoparticles (AgNPs) have been employed in various fields of biotechnology due to their proven properties as an antibacterial, antiviral and antifungal agent. AgNPs are generally synthesized through chemical, physical and biological approaches involving a myriad of methods. As each approach confers unique advantages and challenges, a trends analysis of literature for the AgNPs synthesis using different types of synthesis were also reviewed through a bibliometric approach. A sum of 10,278 publications were analyzed on the annual numbers of publication relating to AgNPs and biological, chemical or physical synthesis from 2010 to 2020 using Microsoft Excel applied to the Scopus publication database. Furthermore, another bibliometric clustering and mapping software were used to study the occurrences of author keywords on the biomedical applications of biosynthesized AgNPs and a total collection of 224 documents were found, sourced from articles, reviews, book chapters, conference papers and reviews. AgNPs provides an excellent, dependable, and effective solution for seven major concerns: as antibacterial, antiviral, anticancer, bone healing, bone cement, dental applications and wound healing. In recent years, AgNPs have been employed in biomedical sector due to their antibacterial, antiviral and anticancer properties. This review discussed on the types of synthesis, how AgNPs are characterized and their applications in biomedical field.

Biogenic Synthesis of Silver Nanoparticles, Characterization and Their Applications—A Review

With the growing awareness for the need of sustainable environment, the importance of synthesizing and the application of green nanoparticles has gained special focus. Among various metal nanoparticles, silver nanoparticles (AgNPs) have gain significant attention. AgNPs are synthesized conventionally by physical and chemical methods using chemicals such as reducing agents, which are hazardous to environment due to their toxic properties, provoking a serious concern to create and develop environment friendly methods. Thus, biological alternatives are emerging to fill gaps, such as green syntheses that use biological molecules taken from plant sources in the form of extracts, which have shown to be superior to chemical and physical approaches. These biological molecules derived from plants are assembled in a highly regulated manner to make them suitable for metal nanoparticle synthesis. The current review outlines the wide plant diversity that may be used to prepare a rapid and single-step procedure with a green path over the traditional ones, as well as their antifungal activity.

Silver nanoparticles for biolistic transformation in Nicotiana tabacum L

The present study reports the use of silver nanoparticles as a gene carrier, substituting gold microcarrier for biolistic gene delivery in Nicotiana tabacum L. Efficiency of biolistic transformation using silver nanoparticles (100 nm) was compared with that of gold microcarriers (0.6 micron) under varying helium pressure (450 psi, 650 psi, 900 psi and 1100 psi) and target distance (6 cm and 9 cm). Among the different concentrations (0.01-100 mgL^-1) of silver nanoparticles tried, 10 mgL^-1 produced the highest number of transient GUS expression (30) with statistical significance. Helium pressure of 650 and target distance of 9 cm, and 900 psi pressure and 6 cm distance resulted in the highest GUS expression with gold microcarriers and silver nanoparticles, respectively. Transformation efficiency was significantly higher with silver nanoparticles than gold microparticles as carriers resulting in a reduction up to 37.5-fold on the cost of consumables. Regeneration efficiencies of tissues bombarded with gold microcarriers and silver nanoparticles were 62.5% and 70.83%, respectively.

The role of silver nanoparticles biosynthesized by Anabaena variabilis and Spirulina platensis cyanobacteria for malachite green removal from wastewater

In this study, biosynthesis of silver nanoparticles (AgNPs) using two species of cyanobacteria, Anabaena variabilis (Kütz) and Spirulina platensis (Gomont) was investigated and evaluated for dye removing capacity. The formation of AgNPs was detected by the change in colour using UV-Vis spectroscopy and further characterised by X-ray diffraction (XRD), transmission electron microscopy (TEM) and Fourier transform infrared spectroscopy (FTIR). The obtained AgNPs were spherical to oval with average particle size of 17.9 and 26.4 nm for S. platensis and A. variabilis, respectively. These AgNPs were applied as bio-sorbent for the removal of malachite green (MG) dye released into wastewater. Within the tested initial concentration range of MG, the reaction exhibited first order kinetics model as monitored via UV spectroscopy. As the dye concentration decreased, the removal efficiency increased to reach 93% for S. platensis and 82% for A. variabilis AgNPs. The results also indicated that increased AgNPs concentration enhanced the MG removal with an efficiency up to 88% and 81% for S. platensis and A. variabilis AgNPs, respectively. The smaller particle diameter and larger specific surface area of S. platensis AgNPs enabled boosted catalytic activity for dye removal than those of A. variabilis. After the treatment with AgNPs, the resultant dye- AgNPs-free effluent proved non-toxic to Triticum aestivum L (Giza 171) seedlings, implying their safety for cultivation practices.

Phycocyanin, a super functional ingredient from algae; properties, purification characterization, and applications

Phycocyanins (PCYs) are a group of luxuriant bioactive compounds found in blue-green algae with an estimated global market of about US$250 million within this decade. The multifarious markets of PCYs noted by form (e.g. powder or aqueous forms), by grade (e.g. analytical, cosmetic, or food grades), and by application (such as biomedical, diagnostics, beverages, foods, nutraceuticals and pharmaceuticals), show that the importance of PCYs cannot be undermined. In this comprehensive study, an overview on PCY, its structure, and health-promoting features are diligently discussed. Methods of purification including chromatography, ammonium sulfate precipitation and membrane filtration, as well as characterization and measurement of PCYs are described. PCYs could have many applications in food colorants, fluorescent markers, nanotechnology, nutraceutical and pharmaceutical industries. It is concluded that PCYs offer significant potentials, although more investigations regarding its purity and safety are encouraged.

Bionanofactories for Green Synthesis of Silver Nanoparticles: Toward Antimicrobial Applications

Among the various types of nanoparticles and their strategy for synthesis, the green synthesis of silver nanoparticles has gained much attention in the biomedical, cellular imaging, cosmetics, drug delivery, food, and agrochemical industries due to their unique physicochemical and biological properties. The green synthesis strategies incorporate the use of plant extracts, living organisms, or biomolecules as bioreducing and biocapping agents, also known as bionanofactories for the synthesis of nanoparticles. The use of green chemistry is ecofriendly, biocompatible, nontoxic, and cost-effective. We shed light on the recent advances in green synthesis and physicochemical properties of green silver nanoparticles by considering the outcomes from recent studies applying SEM, TEM, AFM, UV/Vis spectrophotometry, FTIR, and XRD techniques. Furthermore, we cover the antibacterial, antifungal, and antiparasitic activities of silver nanoparticles.

Algae-mediated biosystems for metallic nanoparticle production: From synthetic mechanisms to aquatic environmental applications

Driven by the growing impetus of green chemistry and environmental protection, the use of bio-based systems to produce green metallic nanomaterials used for environmental remediation has thus developed urgently. It is proposed that using algae as a living cell factory or algal extract as a natural reducing agent is a green and clean way to efficiently synthesize various metallic nanomaterials. However, studies on algal-based biological synthesis of metallic nanomaterials and their applications towards removal of toxic pollutants from wastewater are still limited, which largely discourage the sustainability. Herein, this review aims to introduce the recent advances on algae-mediated nanomaterial-producing biosystems. The corresponding synthetic mechanisms, operation parameters, and case studies on various algae-synthesized metallic nanoparticles are comprehensively discussed and summarized. More importantly, the applicability of algae-synthesized metallic nanoparticles on water treatment is introduced in-depth. To improve economic viability, the challenges and future perspectives are also considered. Taken together, this review systematically presents the achievements and current progress of algae-mediated metallic nanoparticle biosynthesis towards the aquatic pollutants treatment, which can provide new insights on promoting the algae-based nanomaterial production yield and environmental application potential.