Pigment mediated biogenic synthesis of silver nanoparticles using diatom Amphora sp. and its antimicrobial activity

Application of microbial pigments in the pharmaceutical industry: current status and opportunities

Microbial pigments are a diverse group of compounds synthesized by microorganisms, which have attracted considerable scientific interest due to their multifaceted biological properties and significant potential in pharmaceutical applications. These pigments demonstrate various activities, including antimicrobial, antioxidant, anti-inflammatory, and anticancer effects, often mediated by intricate interactions with cellular components such as membranes, proteins, and deoxyribonucleic acid (DNA). For example, antimicrobial pigments can compromise membrane integrity or inhibit protein synthesis, while anti-inflammatory pigments modulate key signaling pathways involved in inflammation. This review explores the different microorganisms capable of producing different pigments. Furthermore, it examines the technological applications, including their potential use in pharmaceuticals and their current commercial use. In addition, clinical cases demonstrating the efficacy of microbial pigments in various therapeutic contexts will be presented. Moving forward, microbial pigments are poised to play a pivotal role in drug development and other biomedical applications, offering some sustainable solutions to various challenges in medicine and industry.

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.

Glycyrrhizin functionalized CuS Nanoprobes for NIR Light-based therapeutic mitigation of acne vulgaris

Acne Vulgaris or Acne is a multifactorial bacterial infection caused by Propionibacterium acne, leading to inflammation and decreased quality of life, especially in adolescence. Currently, antibiotics and retinoids are preferred for treating acne. However, their continuous usage may lead to anti-microbial resistance and other side effects. Therefore, research on developing effective strategies to reduce antimicrobial resistance and improve acne healing is ongoing. The current work reports the synthesis and evaluation of near-infrared light-absorbing copper sulfide (CuS) nanoparticles loaded with a biomolecule, Glycyrrhizin (Ga). The photothermal efficacy studies, and in-vitro and in-vivo experiments indicated that the Ga-CuS NPs generated localized hyperthermia in acne-causing bacteria, leading to their complete growth inhibition. The results indicated that the Ga-Cus NPs possess excellent antibacterial and anti-inflammatory properties in the acne and inflammatory models. This could be from the synergistic effect of CuS NPs mediated mild Photothermal effect and inherent pharmacological properties of Ga. Further detailed studies of the formulations can pave the way for application in cosmetic clinics for the effective and minimally invasive management of Acne-like conditions.

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

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

What Can Help Students Cope with COVID-19? The Contribution of Psychological Capital, Selfcompassion, and Spirituality to Subjective Well-being

Objectives: In this research, we examined the academic and psychological coping of post-secondary students during the early stages of COVID-19. The main goal was to investigate correlations involving self- compassion, spirituality, psychological capital, and subjective well-being, and evaluate the mediating role of self-compassion and spirituality in the relationship between psychological capital and subjective well-being.Methods: We had 257 participants (ages 19-59) complete 5 questionnaires: demographic and academic information, Psychological Capital Questionnaire, Subjective Well-Being Index, Spiritual Intelligence Self- Assessment Inventory, and Self-Compassion Index. Results: We found a strong positive correlation between psychological capital, self-compassion, and subjective well-being. However, spirituality failed to show statistically significant correlations with self-compassion and subjective well-being, with only weak correlations with psychological capital. Self-compassion positively mediated the relationship between psychological capital and subjective well-being, but not spirituality. Conclusion: These findings indicate the role of positive psychological resources of post-secondary students in coping with a difficult situation like COVID-19.

Marine-Bioinspired Nanoparticles as Potential Drugs for Multiple Biological Roles

The increased interest in nanomedicine and its applicability for a wide range of biological functions demands the search for raw materials to create nanomaterials. Recent trends have focused on the use of green chemistry to synthesize metal and metal-oxide nanoparticles. Bioactive chemicals have been found in a variety of marine organisms, including invertebrates, marine mammals, fish, algae, plankton, fungi, and bacteria. These marine-derived active chemicals have been widely used for various biological properties. Marine-derived materials, either whole extracts or pure components, are employed in the synthesis of nanoparticles due to their ease of availability, low cost of production, biocompatibility, and low cytotoxicity toward eukaryotic cells. These marine-derived nanomaterials have been employed to treat infectious diseases caused by bacteria, fungi, and viruses as well as treat non-infectious diseases, such as tumors, cancer, inflammatory responses, and diabetes, and support wound healing. Furthermore, several polymeric materials derived from the marine, such as chitosan and alginate, are exploited as nanocarriers in drug delivery. Moreover, a variety of pure bioactive compounds have been loaded onto polymeric nanocarriers and employed to treat infectious and non-infectious diseases. The current review is focused on a thorough overview of nanoparticle synthesis and its biological applications made from their entire extracts or pure chemicals derived from marine sources.

Biological Synthesis of Silver Nanoparticles and Prospects in Plant Disease Management

Exploration of nanoparticles (NPs) for various biological and environmental applications has become one of the most important attributes of nanotechnology. Due to remarkable physicochemical properties, silver nanoparticles (AgNPs) are the most explored and used NPs in wide-ranging applications. Also, they have proven to be of high commercial use since they possess great chemical stability, conductivity, catalytic activity, and antimicrobial potential. Though several methods including chemical and physical methods have been devised, biological approaches using organisms such as bacteria, fungi, and plants have emerged as economical, safe, and effective alternatives for the biosynthesis of AgNPs. Recent studies highlight the potential of AgNPs in modern agricultural practices to control the growth and spread of infectious pathogenic microorganisms since the introduction of AgNPs effectively reduces plant diseases caused by a spectrum of bacteria and fungi. In this review, we highlight the biosynthesis of AgNPs and discuss their applications in plant disease management with recent examples. It is proposed that AgNPs are prospective NPs for the successful inhibition of pathogen growth and plant disease management. This review gives a better understanding of new biological approaches for AgNP synthesis and modes of their optimized applications that could contribute to sustainable agriculture.

On Recent Developments in Biosynthesis and Application of Au and Ag Nanoparticles from Biological Systems

Gold nanoparticles (AuNPs) and silver nanoparticles (AgNPs) are extensively studied nanoparticles (NPs) and are known to have profound applications in medicine. The researcher made continuous efforts for the environmental-friendly and economical methods, such as biogenic methods known as green synthesis. There are many strategies for separating and applying gold (Au) and silver (Ag) nanoparticles, of which biological routes have emerged as efficient, low-cost, and environmentally friendly techniques. This review focuses on recent developments of green synthesized AuNPs and AgNPs using biogenic sources such as algae, animals, plants, microbes, bacteria, fungi, and so on. Hence, it discusses their numerous biomedical applications and separating Au and Ag nanoparticles from plants, bacteria, fungi, and algae.

Green route for recycling of low-cost waste resources for the biosynthesis of nanoparticles (NPs) and nanomaterials (NMs)-A review

Nowadays, nanoparticles (NPs) and nanomaterials (NMs) are used extensively in various streams such as medical science, solar energy, drug delivery, water treatment, and detection of persistent pollutants. Intensive synthesis of NPs/NMs carried out via physico-chemical technologies is deteriorating the environment globally. Therefore, an urgent need to adopt cost-effective and green technologies to synthesize NPs/NMs by recycling of secondary waste resources is highly required. Environmental wastes such as metallurgical slag, electronics (e-waste), and acid mine drainage (AMD) are rich sources of metals to produce NPs. This concept can remediate the environment on the one hand and the other hand, it can provide a future roadmap for economic benefits at industrial scale operations. The waste-derived NPs will reduce the industrial consumption of limited primary resources. In this review article, green emerging technologies involving lignocellulosic waste to synthesize the NPs from the waste streams and the role of potential microorganisms such as microalgae, fungi, yeast, bacteria for the synthesis of NPs have been discussed. A critical insight is also given on use of recycling technologies and the incorporation of NMs in the membrane bioreactors (MBRs) to improve membrane functioning and process performance. Finally, this study aims to mitigate various persisting scientific and technological challenges for the safe disposal and recycling of organic and inorganic waste for future use in the circular economy.

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.

Green synthesis of silver nanoparticles with algae and the importance of capping agents in the process

BACKGROUND

Nanoparticle synthesis is a very interesting area of research currently due to the wide applications of nanoparticles. The nanoparticles have a diameter ranging between 1 and 100 nm and they are used in different fields like electronics, pharmaceuticals, cosmetics, biotechnology, medicines, etc. Nanoparticles have gained the interest of researchers due to their large surface-to-volume ratio and their capability to interact effectively with other particles. Several different methods can be used for the production of silver nanoparticles (AgNPs) including chemical, physical, and biological. Out of all the methods, the biological method is considered the cleanest and safest as no toxic chemicals are used in the process. The biological method includes the use of bacteria, fungi, algae, and plant extract for the synthesis. Algal synthesis of AgNPs is especially interesting because of the high capacity of the algae to take in metals and reduce metal ions. Algae is a widely distributed organism and its availability is abundant; an added advantage is their growth under laboratory conditions. These organisms can help in large-scale production at a low cost.

SHORT CONCLUSION

This review article explains the different factors that should be considered for the effective synthesis of AgNPs using algae. Capping agents also affect the stability of nanoparticles. It also sheds light on the importance of capping agents in the synthesis of AgNPs. Alga-mediated synthesis of AgNPs along with the use of different capping agents can help in modulating the stability and size of the nanoparticles, thereby improving its cost-effectiveness and environment-friendly production.

Reducing Efficiency of Fucoxanthin in Diatom Mediated Biofabrication of Gold Nanoparticles

In the present investigation, fucoxanthin—one of the major pigments in diatoms—has been extracted from Nanofrustulum shiloi SZCZM1342, and its reducing efficiency in the biogenesis of gold nanoparticles (GNPs) was checked. Fucoxanthin extracted from golden-brown cells of N. shiloi was compared to the healthy, growing biomass of N. shiloi and standard fucoxanthin after separate exposure to 25 mg L⁻¹ aqueous hydrogen tetrachloroaurate solutions at room temperature. Isolated and standard fucoxanthin were found to be able to reduce gold ions within 12 h whereas, the whole biomass turned pink in color after 72 h of reaction. The synthesized particles were characterized by UV-vis spectroscopy, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). UV–vis spectroscopy of purple-colored suspensions showed the absorption band at approximately 520–545 nm, indicating a strong positive signal for GNP synthesis. The SEM study revealed the deposition of GNPs on siliceous frustules of metal-treated diatom cells. The TEM analysis confirmed the GNPs synthesized by whole biomass are triangular, spherical and hexagonal in nature, whereas the particles produced by extracted and standard fucoxanthin are all spherical in nature. This study demonstrates the involvement of fucoxanthin in the reduction of gold ions and subsequent production of gold nanospheres.

Diatoms with Invaluable Applications in Nanotechnology, Biotechnology, and Biomedicine: Recent Advances

Diatoms are unicellular microalga found in soil and almost every aquatic environment (marine and fresh water). Biogenic silica and diatoms are attractive for biotechnological and industrial applications, especially in the field of biomedicine, industrial/synthetic manufacturing processes, and biomedical/pharmaceutical sciences. Deposition of silica by diatoms allows them to create micro- or nanoscale structures which may be utilized in nanomedicine and especially in drug/gene delivery. Diatoms with their unique architectures, good thermal stability, suitable surface area, simple chemical functionalization/modification procedures, ease of genetic manipulations, optical/photonic characteristics, mechanical resistance, and eco-friendliness, can be utilized as smart delivery platforms. The micro- to nanoscale properties of the diatom frustules have garnered a great deal of attention for their application in diverse areas of nanotechnology and biotechnology, such as bioimaging/biosensing, biosensors, drug/gene delivery, photodynamic therapy, microfluidics, biophotonics, solar cells, and molecular filtrations. Additionally, the genetically engineered diatom microalgae-derived nanoporous biosilica have enabled the targeted anticancer drug delivery to neuroblastoma and B-lymphoma cells as well as the mouse xenograft model of neuroblastoma. In this perspective, current trends and recent advances related to the applications of diatoms for the synthesis of nanoparticles, gene/drug delivery, biosensing determinations, biofuel production, and remediation of heavy metals are deliberated, including the underlying significant challenges and future perspectives.

Microbial Fabrication of Nanomaterial and Its Role in Disintegration of Exopolymeric Matrices of Biofilm

Bacterial biofilms are responsible for the development of various chronic wound-related and implant-mediated infections and confer protection to the pathogenic bacteria against antimicrobial drugs and host immune responses. Hence, biofilm-mediated chronic infections have created a tremendous burden upon healthcare systems worldwide. The development of biofilms upon the surface of medical implants has resulted in the failure of various implant-based surgeries and therapies. Although different conventional chemical and physical agents are used as antimicrobials, they fail to kill the sessile forms of bacterial pathogens due to the resistance exerted by the exopolysaccharide (EPS) matrices of the biofilm. One of the major techniques used in addressing such a problem is to directly check the biofilm formation by the use of novel antibiofilm materials, local drug delivery, and device-associated surface modifications, but the success of these techniques is still limited. The immense expansion in the field of nanoscience and nanotechnology has resulted in the development of novel nanomaterials as biocidal agents that can be either easily integrated within biomaterials to prevent the colonization of microbial cells or directly approach the pathogen overcoming the biofilm matrix. The antibiofilm efficacies of these nanomaterials are accomplished by the generation of oxidative stresses and through alterations of the genetic expressions. Microorganism-assisted synthesis of nanomaterials paved the path to success in such therapeutic approaches and is found to be more acceptable for its "greener" approach. Metallic nanoparticles functionalized with microbial enzymes, silver-platinum nanohybrids (AgPtNHs), bacterial nanowires, superparamagnetic iron oxide (Fe₃O₄), and nanoparticles synthesized by both magnetotactic and non-magnetotactic bacteria showed are some of the examples of such agents used to attack the EPS.

Microbial Fabrication of Nanomaterial and Its Role in Disintegration of Exopolymeric Matrices of Biofilm

Bacterial biofilms are responsible for the development of various chronic wound-related and implant-mediated infections and confer protection to the pathogenic bacteria against antimicrobial drugs and host immune responses. Hence, biofilm-mediated chronic infections have created a tremendous burden upon healthcare systems worldwide. The development of biofilms upon the surface of medical implants has resulted in the failure of various implant-based surgeries and therapies. Although different conventional chemical and physical agents are used as antimicrobials, they fail to kill the sessile forms of bacterial pathogens due to the resistance exerted by the exopolysaccharide (EPS) matrices of the biofilm. One of the major techniques used in addressing such a problem is to directly check the biofilm formation by the use of novel antibiofilm materials, local drug delivery, and device-associated surface modifications, but the success of these techniques is still limited. The immense expansion in the field of nanoscience and nanotechnology has resulted in the development of novel nanomaterials as biocidal agents that can be either easily integrated within biomaterials to prevent the colonization of microbial cells or directly approach the pathogen overcoming the biofilm matrix. The antibiofilm efficacies of these nanomaterials are accomplished by the generation of oxidative stresses and through alterations of the genetic expressions. Microorganism-assisted synthesis of nanomaterials paved the path to success in such therapeutic approaches and is found to be more acceptable for its "greener" approach. Metallic nanoparticles functionalized with microbial enzymes, silver-platinum nanohybrids (AgPtNHs), bacterial nanowires, superparamagnetic iron oxide (Fe3O4), and nanoparticles synthesized by both magnetotactic and non-magnetotactic bacteria showed are some of the examples of such agents used to attack the EPS.

Lichens-A Potential Source for Nanoparticles Fabrication: A Review on Nanoparticles Biosynthesis and Their Prospective Applications

Green synthesis of nanoparticles (NPs) is a safe, eco-friendly, and relatively inexpensive alternative to conventional routes of NPs production. These methods require natural resources such as cyanobacteria, algae, plants, fungi, lichens, and naturally extracted biomolecules such as pigments, vitamins, polysaccharides, proteins, and enzymes to reduce bulk materials (the target metal salts) into a nanoscale product. Synthesis of nanomaterials (NMs) using lichen extracts is a promising eco-friendly, simple, low-cost biological synthesis process. Lichens are groups of organisms including multiple types of fungi and algae that live in symbiosis. Until now, the fabrication of NPs using lichens has remained largely unexplored, although the role of lichens as natural factories for synthesizing NPs has been reported. Lichens have a potential reducible activity to fabricate different types of NMs, including metal and metal oxide NPs and bimetallic alloys and nanocomposites. These NPs exhibit promising catalytic and antidiabetic, antioxidant, and antimicrobial activities. To the best of our knowledge, this review provides, for the first time, an overview of the main published studies concerning the use of lichen for nanofabrication and the applications of these NMs in different sectors. Moreover, the possible mechanisms of biosynthesis are discussed, together with the various optimization factors influencing the biological synthesis and toxicity of NPs.

In-situ green synthesis of fluorescent silica-silver conjugate nanodendrites using nanoporous frustules of diatoms: an unprecedented approach

Generally, nanodendrite synthesis is chemical mediated and expensive. The biogenesis of such hierarchical structures is still in its nascent stage. The present study aimed at exploiting the nanoporous frustules of Halamphora subturgida, as a source of biosilica for the biosynthesis and stabilization of conjugate nanodendrites of silica and silver. These minute diatom frustules when exposed to 9 mM of silver nitrate solution, a highly crystalline nanohybride dendrites were synthesized. The nanohybrid dendrite synthesis was initially confirmed by the formation of greyish-brown frustules after 72 h of exposure. The composite dendrites were thoroughly characterized by standard techniques. Electron microscopic images illustrated that the process began with the formation of isotropic hybrid nanospheres with an internal diameter of 20 nm and continued to develop anisotropic nanocrystals with time. The nanodendrites externally formed on the siliceous frustules, acting as a template for the former. They were characterized by distinct 100 nm wide and 1-2 µm long trunks and 70-100 nm wide and 220-220 nm long branches on either side of the trunk. The optical measurement revealed the fluorescence property of the nanostructures owing to the photoluminescent efficiency of the frustules. Both the externally derived hybrid nanodendrites and internally synthesized nanospheres possessed superior stability in the suspension with a zeta potential value of - 35.7 mV and - 24.8 mV, respectively. Thus, this method is eco-friendly and provides a new dimension for nanodendrite synthesis with minimal cost and maximal yield compared to its non-biologically synthesized counterparts that involve several other drawbacks like chemical hazards and high energy consumption.

Statistical optimization of photo-induced biofabrication of silver nanoparticles using the cell extract of Oscillatoria limnetica: insight on characterization and antioxidant potentiality

Silver nanoparticles were successfully fabricated through a very simple, rapid, one-step photo-induced green approach. The formation of silver nanoparticles was accomplished using the bioactive compounds in the aqueous extract of fresh Oscillatoria limnetica biomass, which acted as a reducing and capping agent at the same time. The biosynthesis of Oscillatoria-silver nanoparticles (O-AgNPs) was investigated under the influence of different light intensities 57.75, 75.90 and 1276.51 μmol m-2 s-1 (bright sunlight). UV-Vis (UV) and Fourier transform infrared (FT-IR) spectroscopy were applied to approve the synthesis of AgNPs. Further, the synthesis process under the exposure to sunlight was adjusted via utilizing one factor at a time, and 0.5 mM AgNO3 concentration, 5 mL O. limnetica solution, pH 6.7 and 30 min sunlight (1276.51 μmol m-2 s-1) were applied. Furthermore, the central composite design (CCD) was applied to boost the biosynthesis process of O-AgNPs (manufactured at light intensity 75.90 μmol m-2 s-1). The maximum production of O-AgNPs was attained with 4 detected variables: initial pH level (6.7), AgNO3 concentration (0.3 mM), O. limnetica extract concentration (3.50 mL) and incubation time (48 h). Moreover, TEM, in addition to SEM, images exposed that the biosynthesized AgNPs were quasi-spherical in shape with a small monodisperse nature, and the size range was between 6.98-23.48 nm in the case of light-induced synthesis (75.90 μmol m-2 s-1) and 11.58-22.31 nm with sunlight (1276.51 μmol m-2 s-1).

Biosynthesis of silver nanoparticles from marine diatoms Chaetoceros sp., Skeletonema sp., Thalassiosira sp., and their antibacterial study

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Marine Diatoms have been envisaged for AgNP synthesis.

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The average size of AgNP ranges from 150 to 350 nm.

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Diatom based AgNP exhibits excellent biocidal activity.

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These AgNP showed inhibition against both Gram-positive and Gram negative bacteria.

Diatoms are a reservoir of metabolites with diverse applications and silver nanoparticle (AgNP) from diatoms holds immense therapeutic potentials against pathogenic microbes owing to their silica frustules. In the present study, Chaetoceros sp., Skeletonema sp., and Thalassiosira sp were used for synthesis of AgNP. The average particle size of AgNP synthesized was 149.03 ± 3.0 nm, 186.73 ± 4.9 nm, and 239.46 ± 44.3 nm as reported in DLS whereas 148.3 ± 46.8 nm, 238.0 ± 60.9 nm, and 359.8 ± 92.33 nm in SEM respectively. EDX analysis strongly indicates the confirmation of AgNP displaying a sharp peak of Ag⁺ ions within the spectra. High negative zeta potential values indicate a substantial degree of stabilization even after three months. The antibacterial efficacy of biosynthesized AgNP tested against Aeromonas sp., Escherichia coli, Bacillus subtilis, Staphylococcus aureus, and Streptococcus pneumonia exhibits broad-spectrum antibacterial activity. This study encourages the synthesis of diatom based AgNP for a variety of applications owing least toxicity and biodegradable nature.

Green synthesis of silver nanoparticles using canthaxanthin from Dietzia maris AURCCBT01 and their cytotoxic properties against human keratinocyte cell line

AIM

Nano-biotechnologically synthesizing silver nanoparticles via canthaxanthin pigment extracted from Dietzia maris AURCCBT01 and assessing their cytotoxic therapeutic potential against human keratinocyte cell line (HaCaT) were the key objectives of this study.

METHODS AND RESULTS

The pigment extracted from D. maris AURCCBT01 was identified as canthaxanthin using UV-VIS spectroscopy, FTIR, NMR (¹ H NMR and ¹³ C NMR) and MS. Canthaxanthin, treated with silver nitrate solution, produced canthaxanthin-mediated silver nanoparticles and they were characterized by UV-VIS spectroscopy, FTIR, XRD, FESEM-EDX and TEM-SAED techniques. UV-VIS spectroscopy pointed out an absorption band at 420 nm, relating to the surface plasmon resonance of silver nanoparticles. FTIR findings suggested that the diverse functional groups of canthaxanthin bio-molecules played a significant task in capping the silver nanoparticles. XRD analysis exhibited 40·20 nm for the crystal size of nanoparticles. FESEM and TEM exhibited that the biosynthesized silver nanoparticles were spherical in shape with crystalline nature and the particle size was 40-50 nm. Moreover, the cytotoxicity assessment of the synthesized nanoparticles in HaCaT revealed significant cytotoxicity in the cultured cells with an IC₅₀ value of 43 µg ml^-1 .

CONCLUSION

Stable silver nanoparticles synthesized using canthaxanthin from D. maris AURCCBT01 were found effective for application in wound healing activity.

SIGNIFICANCE AND IMPACT OF THE STUDY

Biosynthesized silver nanoparticles via canthaxanthin bacterial pigment exhibited their cytotoxicity effect in HaCaT and testified their eventual therapeutic potential in the wound healing activity with no side effects in a cost effective and eco-friendly process.

Microbial Nanotechnology: Challenges and Prospects for Green Biocatalytic Synthesis of Nanoscale Materials for Sensoristic and Biomedical Applications

Nanomaterials are increasingly being used in new products and devices with a great impact on different fields from sensoristics to biomedicine. Biosynthesis of nanomaterials by microorganisms is recently attracting interest as a new, exciting approach towards the development of 'greener' nanomanufacturing compared to traditional chemical and physical approaches. This review provides an insight about microbial biosynthesis of nanomaterials by bacteria, yeast, molds, and microalgae for the manufacturing of sensoristic devices and therapeutic/diagnostic applications. The last ten-year literature was selected, focusing on scientific works where aspects like biosynthesis features, characterization, and applications have been described. The knowledge, challenges, and potentiality of microbial-mediated biosynthesis was also described. Bacteria and microalgae are the main microorganism used for nanobiosynthesis, principally for biomedical applications. Some bacteria and microalgae have showed the ability to synthetize unique nanostructures: bacterial nanocellulose, exopolysaccharides, bacterial nanowires, and biomineralized nanoscale materials (magnetosomes, frustules, and coccoliths). Yeasts and molds are characterized by extracellular synthesis, advantageous for possible reuse of cell cultures and reduced purification processes of nanomaterials. The intrinsic variability of the microbiological systems requires a greater protocols standardization to obtain nanomaterials with increasingly uniform and reproducible chemical-physical characteristics. A deeper knowledge about biosynthetic pathways and the opportunities from genetic engineering are stimulating the research towards a breakthrough development of microbial-based nanosynthesis for the future scaling-up and possible industrial exploitation of these promising 'nanofactories'.

New avenues of controlling microbial infections through anti-microbial and anti-biofilm potentials of green mono-and multi-metallic nanoparticles: A review

Nanoparticles synthesized through the green route deserve special mention because this green technology is not only energy-efficient and cost-effective but also amenable to the environment. Various biological resources have been used for the generation of these 'green nanoparticles'. Biological wastes have also been focused in this direction thereby promoting the value of waste. Reports indicate that green nanoparticles exhibit remarkable antimicrobial activitiesboth singly as well as in combination with standard antibiotics. The current phenomenon of multi-drug resistance has resulted due to indiscriminate administration of high-doses of antibiotics followed by significant toxicity. In the face of this emergence of drug-resistant microbesthe efficacy of green nanoparticles might prove greatly beneficial. Microbial biofilm is another hurdle in the effective treatment of diseases as the microorganismsbeing embedded in the meshwork of the biofilmevade the antimicrobial agents. Nanoparticles may act as a ray of hope on the face of this challenge tooas they not only destroy the biofilms but also lessen the doses of antibiotics requiredwhen administered in combination with the nanoparticles. It should be further noted that the resistance mechanisms exhibited by the microorganisms seem not that relevant for nanoparticles. The current review, to the best of our knowledgefocuses on the structures of these green nanoparticles along with their biomedical potentials. It is interesting to note how a variety of structures are generated by using resources like microbes or plants or plant products and how the structure affects their activities. This study might pave the way for further development in this arena and future work may be taken up in identifying the detailed mechanism by which 'green' synthesis empowers nanoparticles to kill pathogenic microbes.

Advances in biosynthesis of noble metal nanoparticles mediated by photosynthetic organisms-A review

The last decade has witnessed significant developments in the biosynthesis of noble metal nanoparticles (NMNPs) due to their distinct advantages in various practical applications. Many photosynthetic organisms, including plants, microalgae, and photosynthetic bacteria, have been explored for NMNP synthesis in an eco-friendly and cost-effective manner. These biomasses were used for NMNP biosynthesis as growing cells, non-growing cells, whole cells extract, disrupted cell extract, residual biomasses, gum solutions, etc. Different mechanisms might be involved to reduce noble metal ions to NMNP. These mechanisms include reduction of metal ions catalysed by reductases using NADH as electron donors, reduction of metal ions using biochemical molecules such as polysaccharides and proteins as electron donators, and light-dependant biosynthesis of NMNP involving pigments for light capture and water-splitting for electron supplementation. NMNP may be applied as catalyst, antibacterial, anticancer, and drug delivery vehicle.

A method to increase the survival of probiotic bacteria Lactobacillus brevis at a lowered pH

Lactobacillus brevis PCM 2570 is a strain of lactic acid bacteria, i.e. probiotic bacteria whose major fermentation product is lactic acid. The efficiency of lactic acid production is limited by the value of ambient pH. This study aimed to increase the survival of this bacterial strain at a reduced pH (3.9), which would result in an increased yield of lactic acid fermentation. In our experiment the survival rate of probiotic bacteria L. brevis PCM 2570 was increased 1.2-fold to 6.96-fold due to the presence of Fe3O4 magnetic nanoparticles, as compared to the control. The minimum concentration of nanoparticles with a positive effect was 8 mg/ml, but the optimum concentration was 20 mg/ml.

Individual and Combined Effects of Extracellular Polymeric Substances and Whole Cell Components of Chlamydomonas reinhardtii on Silver Nanoparticle Synthesis and Stability

The fresh water microalga Chlamydomonas reinhardtii bioreduced Ag⁺ to silver nanoparticles (AgNPs) via three biosynthetic routes in a process that could be a more sustainable alternative to conventionally produced AgNPs. The AgNPs were synthesized in either the presence of whole cell cultures, an exopolysaccharide (EPS)-containing cell culture supernatant, or living cells that had been separated from the EPS-containing supernatant and then washed before being suspended again in fresh media. While AgNPs were produced by all three methods, the washed cultures had no supernatant-derived EPS and produced only unstable AgNPs, thus the supernatant-EPS was shown to be necessary to cap and stabilize the biogenic AgNPs. TEM images showed stable AgNPs were mostly spherical and showed a bimodal size distribution about the size ranges of 3.0 ± 1.3 nm and 19.2 ± 5.0 nm for whole cultures and 3.5 ± 0.6 nm and 17.4 ± 2.6 nm for EPS only. Moreover, selected area electron diffraction pattern of these AgNPs confirmed their polycrystalline nature. FTIR of the as-produced AgNPs identified polysaccharides, polyphenols and proteins were responsible for the observed differences in the AgNP stability, size and shape. Additionally, Raman spectroscopy indicated carboxylate and amine groups were bound to the AgNP surface.

Heavy metal resistance in algae and its application for metal nanoparticle synthesis

The ungenerous release of metals from different industrial, agricultural, and anthropogenic sources has resulted in heavy metal pollution. Metals with a density larger than 5 g cm^-3 have been termed as heavy metals and have been stated to be potentially toxic to human and animals. Algae are known to be pioneer organisms with the potential to grow under extreme conditions including heavy metal-polluted sites. They have evolved efficient defense strategies to combat the toxic effects exerted by heavy metal ions. Most of the algal strains are reported to accumulate elevated metal ion concentration in cellular organelles. With respect to that, this review focuses on understanding the various strategies used by algal system for heavy metal resistance. Additionally, the application of this metal resistance in biosynthesis of metal nanoparticles and metal oxide nanoparticles has been investigated in details. We thereby conclude that algae serve as an excellent system for understanding metal uptake and accumulation. This thereby assists in the design and development of low-cost approaches for large-scale synthesis of nanoparticles and bioremediation approach, providing ample opportunities for future work.

Effects of reaction conditions on light-dependent silver nanoparticle biosynthesis mediated by cell extract of green alga Neochloris oleoabundans

Silver nanoparticles (AgNPs) were synthesized by incubating the mixture of AgNO₃ solution and whole-cell aqueous extracts (WCAEs) of Neochloris oleoabundans under light conditions. By conducting single-factor and multi-factor optimization, the effects of parameters including AgNO₃ concentration, pH, and extraction time were quantitatively evaluated. The optimal conditions in terms of AgNP yield were found to be 0.8 mM AgNO₃, pH 5, and 9-h extraction. The AgNPs thus synthesized were quasi-spherical with a mean particle diameter of 16.63 nm and exhibited decent uniformity as well as antibacterial activities, which may facilitate AgNP biosynthesis's application in the near future.

Biosynthetic Conversion of Ag⁺ to highly Stable Ag⁰ Nanoparticles by Wild Type and Cell Wall Deficient Strains of Chlamydomonas reinhardtii

In the current study, two different strains of the green, freshwater microalga Chlamydomonas reinhardtii bioreduced Ag⁺ to silver nanoparticles (AgNPs), which have applications in biosensors, biomaterials, and therapeutic and diagnostic tools. The bioreduction takes place in cell cultures of C. reinhardtii at ambient temperature and atmospheric pressure, thus eliminating the need for specialized equipment, harmful reducing agents or the generation of toxic byproducts. In addition to the visual changes in the cell culture, the production of AgNPs was confirmed by the characteristic surface plasmon resonance (SPR) band in the range of 415–425 nm using UV-Vis spectrophotometry and further evolution of the SPR peaks were studied by comparing the peak intensity at maximum absorbance over time. X-ray diffraction (XRD) determined that the NPs were Ag⁰. Micrographs from transmission electron microscopy (TEM) revealed that 97 ± 2% AgNPs were <10 nm in diameter. Ag⁺ to AgNP conversion was determined by inductively coupled plasma atomic emission spectroscopy (ICP-AES). The AgNPs were stable over time in the cell culture media, acetone, NaCl and reagent alcohol solutions. This was verified by a negligible change in the features of the SPR band after t > 300 days of storage at 4 °C.

Diatoms – A “Green” Way to Biosynthesize Gold-Silica Nanocomposites?

Biosynthesis by diatoms provides a green approach for nanoparticle (NP) production. However, reproducible and homogeneous shapes are essential for their application. To improve these characteristics during biosynthesis, the underlying synthesis mechanisms as well as involved substances need to be understood. The first essential step for suitable analyses is the purification of Au-silica-nanocomposites from organic biomass. Succesfully cleaned nanocomposites could, for example, be useful as catalysts. In combination with the biosynthesized NPs, this material presents a “green” catalyst and could contribute to the currently thriving green nanochemistry. In this work, we compare different purification agents with respect to their ability to purify cells of the diatom Stephanopyxis turris without separating the biosynthesized Au-silica-nanocomposites from the diatom cell walls. Scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX) are used to localize and identify Au-silica-nanocomposites around the cells. The amount of remaining organic compounds on the purified cell is detected by attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy. Furthermore, inductively coupled plasma optical emission spectrometry (ICP-OES) is used to track the “gold path” during cell growth and the different purifications steps.

Amine-functionalized diatom frustules: a platform for specific and sensitive detection of nitroaromatic explosive derivative

In the present study, an attempt was made to develop a proof of concept for the detection of nitroaromatic explosive derivatives through the photoluminescence (PL) quenching process using functionalized diatom frustules as a sensing platform. The diatom frustules are composed of nanostructured, highly porous biogenic silica material and emit strong, visible blue PL upon UV excitation. PL-active biosilica was isolated from the marine diatom Nitzschia sp. and was amine-functionalized to develop a sensing platform. Functionalized diatom frustules were further characterized using field emission scanning electron microscope and a series of spectroscopic methods. When nitroaromatic compounds were bound to the functionalized diatom frustules biosilica, the PL intensity from the functionalized biosilica was partially quenched due to the electrophilic nature of the nitro (-NO) groups. The quenching process confirmed the Meisenheimer complex formation and was investigated by using Fourier transform infrared spectroscopy and time-resolved photoluminescence studies. The developed platform was further evaluated for its sensitivity and specificity, and the limit of detection (LOD) of the assay was determined as 1 μM for a series of nitroaromatic explosive compounds. In conclusion, the developed sensing platform will have great utility in the development of on-site detection platforms for sensitive detection of warfare explosive nitroaromatic compounds from the environment.

Mechanism of light-dependent biosynthesis of silver nanoparticles mediated by cell extract of Neochloris oleoabundans

This study investigated the role of chlorophyll and light in the biosynthesis of silver nanoparticles (AgNPs) using disrupted cell aqueous extract of Neochloris oleoabundans. It was found that, while increasing sonication time increased the percentage of disrupted cells and efficiency of aqueous cell extraction, over-sonication reduced AgNPs production. AgNPs biosynthesis required illumination of white, blue, or purple light while AgNPs formation was undetectable under dark condition or illumination of orange or red light, indicating only photons of high energy levels among the photosynthetic active radiations are capable of exciting the electrons of chlorophylls to a state that is sufficient for Ag⁺ reduction. Chlorophylls were demonstrated to be an essential component mediating the reduction of Ag⁺ and results of mass balance suggest that chlorophylls need to be recycled for the reaction to complete. The ultimate electron donor was hypothesized to be water, which supplemented electrons through water splitting catalyzed by photosynthetic enzyme complexes such as photosystem II. A hypothetical reaction mechanism is proposed for the light-dependent biosynthesis of AgNPs based on systematic experimental results and literature data for the first time.

Phytochemical-assisted synthetic approaches for silver nanoparticles antimicrobial applications: A review

Silver nanoparticles (Ag NPs) have recently emerged as promising materials in the biomedical sciences because of their antimicrobial activities towards a wide variety of microorganisms. Nanomaterial-based drug delivery systems with antimicrobial activity are critical as they may lead to novel treatments for cutaneous pathogens. In this review, we explore the recent progress on phytochemical-mediated synthesis of Ag NPs for antimicrobial treatment and associated infectious diseases. We discuss the biological activity of Ag NPs including mechanisms, antimicrobial activity, and antifungal/antiviral effects towards various microorganisms. The advent of Ag NP-based nanocarriers and nano-vehicles is also described for treatment of different diseases, along with the mechanisms of microbial inhibition. Overall, this review will provide a rational vision of the main achievements of Ag NPs as nanocarriers for inhibition of various microbial agents (bacteria, fungus, and virus).

Limonia acidissima L. leaf mediated synthesis of silver and zinc oxide nanoparticles and their antibacterial activities

Green chemistry is a novel method for the synthesis of silver and zinc oxide nanoparticles. The present investigation focused on synthesis of biogenic silver and zinc oxide nanoparticles. They were assayed for their antibacterial activities against test bacterial species. The results revealed that the silver nanoparticles showed the maximum zone of inhibition 15.16, 15.5 and 13.33 mm at 400 μg/mL to S. aureus, S. typhi and P. aeruginosa respectively, when compared to the Erythromycin. While zinc oxide nanoparticles showed less activity in comparison to silver nanoparticles owing to the agglomeration of nanoparticles. It is evident from our investigation that silver nanoparticles could be used as an antimicrobial due to their intrinsic properties in biomedical application and food packing industries.

Marinobacter lipolyticus from Red Sea for lipase production and modulation of silver nanomaterials for anti-candidal activities

In this study, the bacterial strain CEES 33 was isolated from the coastal area of the Red Sea, Jeddah, Kingdom of Saudi Arabia. The bacterium isolate was identified and characterized by using biochemical and molecular methods. The isolate CEES 33 has been identified as Gram-negative rod shaped and cream pigmented spherical colonies. It also demonstrated a positive result for nitrate reduction, oxidase, catalase, citrate utilization, lipase and exopolysaccharide production. Strain CEES 33 was characterized at the molecular level by partial 16S rRNA sequencing and it has been identified as Marinobacter lipolyticus (EMBL|LN835275.1). The lipolytic activity of the isolate was also observed 2.105 nkatml-1. Furthermore, the bacterial aqueous extract was used for green synthesis of silver nanoparticles (AgNPs), which was further confirmed by UV-visible spectra (430 nm), XRD and SEM analysis. Moreover, the biological functional group that involved in AgNPs synthesis was confirmed by FTIR spectra. The biological activities of AgNPs were also investigated, which showed a significant growth inhibition of Candida albicans with 16 ± 2 mm zone of inhibition at 10 μg dose/wells. Therefore, bacterium Marinobacter lipolyticus might be used in future for lipase production and nanoparticles fabrication for biomedical application, to control fungal diseases caused by C. albicans.

Phytochemical constituents of fucoidan (Padina tetrastromatica) and its assisted AgNPs for enhanced antibacterial activity

Biological synthesis of nanomaterials is a growing innovative approach and it was broadly utilised in the field of nanotechnology and nanomedicine. This study illustrates that biosynthesis of silver nanoparticles (AgNPs) using fucoidan extracted from seaweed Padina tetrastromatica. The functional groups of extracted fucoidan were characterised by Fourier transform infrared spectroscopy (FTIR) and used to NPs synthesis. Synthesised AgNPs were characterised by ultraviolet-visible spectra, scanning electron microscope, energy dispersive X-ray, transmission electron microscope, selected area electron diffraction and FTIR. In this study, their main focus is enhancement antibacterial activity of AgNPs coated antibiotics against antibiotic resistant bacteria. Among the microorganisms, Serratia nematodiphila was resistant to novobiocin and penicillin, but it was sensitive to AgNPs impregnated antibiotic discs. The zone of inhibition was 12 and 15 mm. The synergistic effect of combined antibiotics and AgNPs resulted in increased fold area which was greater than the sum of their separate effects. It reveals that AgNPs are highly sought in the medicinal field due to their broad spectrum of antibacterial activity and relatively cheaper. This enhanced synergistic effect potentially superior to control the growth of bacteria and it is the budding process for the development of new remedial agents for severe diseases.