Biogenic Nanomaterials Research Articles

Recent advances in the use of biogenic nanomaterials and photocatalysts for wastewater treatment: challenges and future prospects

Recent advances in the use of biogenic nanomaterials and photocatalysts for wastewater treatment: challenges and future prospects

Enhanced photocatalytic degradation of methylene blue and methyl orange using biogenic ZnO NPs synthesized via Vachellia nilotica (Babool) leaves extract

Biogenic zinc oxide (b-ZnO) NPs were synthesized via the leaf extract of Vachellia nilotica (Babool) due to their rich source of bioactive complexes, which have great potential as a reliable, sustainable, and eco-friendly system. Sharp peaks in the XRD pattern of b-ZnO NPs confirmed the hexagonal wurtzite crystal structure. The crystallite size, D, of b-ZnO, decreased from 22.22 nm to 10.13 nm, and the lattice strain (τ) increased from 5.22 × 10−3 to 11.47 × 10−3 as the material changed from synthetic to biogenic, respectively. The Eg of b-ZnO was observed to be 3.37 eV. The specific surface area, total pore volume and average pore diameter of ZnO and b-ZnO NPs were increased from 9.5 to 34 m2/g, 0.3536–0.3854 cm3/g, and 17.24–19.56 nm, respectively. The photocatalytic degradation of b-ZnO increased from 72% to 80% for MO dye, from 87% to 93% for MB dye and completely degraded MB within 2 h. This work presents an essential advancement towards achieving enhanced photocatalytic performance to reduce water pollutants using b-ZnO and will guide the use of biogenic nanomaterials for photocatalytic applications.

Facile green synthesis of Phyllanthus emblica extract based Ag-NPs for antimicrobial and response surface methodology based catalytic reduction applications

Silver nanostructures were synthesized by utilizing facile and simple green methodology based on the usage of biogenic Phyllanthus emblica fruit extract. The Fourier transform infrared spectroscopy revealed that the numerous phytochemicals were found to be present in the extract that were responsible for reducing the precursor salt into nanoparticles. After 10 min, the silver nanoparticles were formed in the system while the further nucleation for 30 min resulted in the generation of the silver nanostructures with dual morphology (spherical & rod-like morphology). The reaction time/nucleation time was found to be the major factor responsible for the modulation of the morphology of the biogenic nanomaterials. The crystalline nature with the cubic crystal system was observed in the case of the silver nanostructure via X-ray diffraction analysis. The antimicrobial efficacy investigated for these nanostructures revealed that the silver nanostructures possess comparable or greater efficacy than the selected control. The excellent efficacy is attributed to the smaller size and the peculiar morphological characteristics of the silver nanostructures. The catalytic reduction of 4-nitrophenol via silver nanostructures was also investigated by using the response surface methodology as an optimization tool. An extremely high percentage reduction value of 96.491 % with the rate constant value of 0.277 min−1 was documented in the case of Ag-NSs. The prepared silver nanostructures were found to be extremely stable till six reuse cycles. Our findings affirm that the efficient synthesis of nanostructures is achieved by using P. emblica fruit extract and the synthesized material further presents excellent viability for antimicrobial and catalytic applications.

Colorimetric sensor based on biogenic nanomaterials for high sensitive detection of hydrogen peroxide and multi-metals

Hydrogen peroxide (H2O2) and heavy metals, which are among the wastes of the industrial sector, become a threat to living things and the environment above certain concentrations. Therefore, the detection of both H2O2 and heavy metals with simple, low-cost, and fast analytical methods has gained great importance. The use of nanoparticles in colorimetric sensor technology for the detection of these analytes provides great advantages. In recent years, green synthesis of nanomaterials with products that can be considered biowaste is among the popular topics. In this study, silver/silver chloride nanoparticles (Ag@AgCl NPs) were synthesized using the green synthesis method as an eco-friendly and cheap method, the green algae extract was used as a reducing agent. The characterization of Ag@AgCl nanoparticles and green algae extract was carried out with several techniques such as Transmission Electron Microscopy (TEM), UV–Visible spectrometry (UV–Vis), Fourier-transform infrared spectroscopy (FTIR), and X-ray diffraction patterns (XRD) methods were used for characterization. According to TEM analysis, the Ag@AgCl NPs typically spherical in form and range in size from 4 to 10 nm, and UV–vis showed the formation of surface plasmon resonance (SPR) of the Ag@AgCl between 400 and 450 nm. In addition, its activity as a colorimetric sensor for hydrogen peroxide (H2O2) and multi-metal detection was evaluated. Interestingly, Ag/AgCl NPs caused different color formations for 3 metals simultaneously in the sensor study for heavy metal detection, and Fe3+, Cu2+, and Cr6+ ions were detected. The R2 values for H2O2, Fe3+, Cu2+, and Cr6+ were 0.9360, 0.9961, 0.9787, and 0.9625 the limit of detection (LOD) was 43.75, 1.69, 3.18, and 5.05 ppb (ng/mL), respectively. It was determined that Ag@AgCl NPs have the potential to be used as a colorimetric sensor for the detection of H2O2 and heavy metals from wastewater.

Impact of Biogenic and Chemogenic Selenium Nanoparticles on Model Eukaryotic Lipid Membranes.

Microbial nanotechnology is an expanding research area devoted to producing biogenic metal and metalloid nanomaterials (NMs) using microorganisms. Often, biogenic NMs are explored as antimicrobial, anticancer, or antioxidant agents. Yet, most studies focus on their applications rather than the underlying mechanism of action or toxicity. Here, we evaluate the toxicity of our well-characterized biogenic selenium nanoparticles (bSeNPs) produced by the Stenotrophomonas maltophilia strain SeITE02 against the model yeast Saccharomyces cerevisiae comparing it with chemogenic SeNPs (cSeNPs). Knowing from previous studies that the biogenic extract contained bSeNPs in an organic material (OM) and supported here by Fourier transform infrared spectroscopy, we removed and incubated it with cSeNPs (cSeNPs_OM) to assess its influence on the toxicity of these formulations. Specifically, we focused on the first stages of the eukaryotic cell exposure to these samples─i.e., their interaction with the cell lipid membrane, which was mimicked by preparing vesicles from yeast polar lipid extract or phosphatidylcholine lipids. Fluidity changes derived from biogenic and chemogenic samples revealed that the bSeNP extract mediated the overall rigidification of lipid vesicles, while cSeNPs showed negligible effects. The OM and cSeNPs_OM induced similar modifications to the bSeNP extract, reiterating the need to consider the OM influence on the physical-chemical and biological properties of bSeNP extracts.

Biogenic Copper Selenide Nanoparticles for Near-Infrared Photothermal Therapy Application.

Near-infrared (NIR) photothermal therapy (PTT) is attractive for cancer treatment but is currently restricted by limited availability and insufficient NIR-II photoactivity of photothermal agents, for which artificial nanomaterials are usually used. Here, we report the first use of biogenic nanomaterials for PTT application. A fine-controlled extracellular biosynthesis of copper selenide nanoparticles (bio-Cu2-xSe) by Shewanella oneidensis MR-1 was realized. The resulting bio-Cu2-xSe, with fine sizes (∼35.5 nm) and high product purity, exhibited 76.9% photothermal conversion efficiency under 1064 nm laser irradiation, outperforming almost all the existing counterparts. The protein capping also imparted good biocompatibility to bio-Cu2-xSe to favor a safe PTT application. The in vivo PTT with injected bio-Cu2-xSe in mice (without extraction nor further modification) showed 87% tumor ablation without impairing the normal organisms. Our work not only opens a green route to synthesize the NIR-II photothermal nanomaterial but may also lay a basis for the development of bacteria-nanomaterial hybrid therapy technologies.

Biogenic Nanomaterials: A Way Forward in Preventing Bacterial Infections

Antibiotic resistance puts a tremendous strain on the healthcare system. Bacteria such as Staphylococcus aureus, Klebsiella pneumoniae, and Pseudomonas aeruginosa that cause diseases like endocarditis, pneumonia, and Urinary tract infections have now become resistant to many previously used antibiotics. Antibiotic overuse must be reduced as it has become a public health threat paving the way to pandemics. Instead of creating new antibiotics, repurposing existing medicines that have faced resistance is one way forward. Plant-based antimicrobials have been explored as antibiotics to boost or augment the capability of existing antibiotics. It has been proposed that conjugates of plant-based products and antibiotics have increased activity and that the conjugated groups could help circumvent the beta-lactam antibiotic resistance mechanisms. Antibiotics have been combined with plant-based substances like Berberine, and a considerable synergy has been reported among them. Nanomaterials also promise a powerful environment-friendly strategy for weaponizing antibiotics with plant compounds. Nanoparticles could attach with many biological molecules such as DNA, enzymes, ribosomes, and lysosomes, further affecting the permeability of the cell membrane. The interaction of nanoparticles with many biological targets makes it hard for bacteria to develop resistance against them. Low molecular weight nanomaterial based on antibiotics could be very effective against multidrug-resistant gram-negative pathogens. Our study aims to analyze the progress done at the front of nanomaterials and nano-antibiotics against infectious diseases.

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.

Bioinspired Green Synthesis of Silver Nanoparticles Using Three Plant Extracts and Their Antibacterial Activity against Rice Bacterial Leaf Blight Pathogen Xanthomonas oryzae pv. oryzae.

Rice bacterial leaf blight caused by Xanthomonas oryzae pv. oryzae (Xoo) is responsible for a significant reduction in rice production. Due to the small impact on the environment, biogenic nanomaterials are regarded as a new type of antibacterial agent. In this research, three colloids of silver nanoparticles (AgNPs) were synthesized with different biological materials such as Arctium lappa fruit, Solanum melongena leaves, and Taraxacum mongolicum leaves, and called Al-AgNPs, Sm-AgNPs and Tm-AgNPs, respectively. The appearance of brown colloids and the UV-Visible spectroscopy analysis proved the successful synthesis of the three colloids of AgNPs. Moreover, FTIR and XRD analysis revealed the formation of AgNPs structure. The SEM and TEM analysis indicated that the average diameters of the three synthesized spherical AgNPs were 20.18 nm, 21.00 nm, and 40.08 nm, respectively. The three botanical AgNPs had the strongest bacteriostatic against Xoo strain C2 at 20 μg/mL with the inhibition zone of 16.5 mm, 14.5 mm, and 12.4 mm, while bacterial numbers in a liquid broth (measured by OD600) decreased by 72.10%, 68.19%, and 65.60%, respectively. Results showed that the three AgNPs could inhibit biofilm formation and swarming motility of Xoo. The ultrastructural observation showed that Al-AgNPs adhered to the surface of bacteria and broke the bacteria. Overall, the three synthetic AgNPs could be used to inhibit the pathogen Xoo of rice bacterial leaf blight.

Antibiotic Resistance in the Drinking Water: Old and New Strategies to Remove Antibiotics, Resistant Bacteria, and Resistance Genes.

Bacterial resistance is a naturally occurring process. However, bacterial antibiotic resistance has emerged as a major public health problem in recent years. The accumulation of antibiotics in the environment, including in wastewaters and drinking water, has contributed to the development of antibiotic resistant bacteria and the dissemination of antibiotic resistance genes (ARGs). Such can be justified by the growing consumption of antibiotics and their inadequate elimination. The conventional water treatments are ineffective in promoting the complete elimination of antibiotics and bacteria, mainly in removing ARGs. Therefore, ARGs can be horizontally transferred to other microorganisms within the aquatic environment, thus promoting the dissemination of antibiotic resistance. In this review, we discuss the efficiency of conventional water treatment processes in removing agents that can spread/stimulate the development of antibiotic resistance and the promising strategies for water remediation, mainly those based on nanotechnology and microalgae. Despite the potential of some of these approaches, the elimination of ARGs remains a challenge that requires further research. Moreover, the development of new processes must avoid the release of new contaminants for the environment, such as the chemicals resulting from nanomaterials synthesis, and consider the utilization of green and eco-friendly alternatives such as biogenic nanomaterials and microalgae-based technologies.

DAT and PRX1 gene expression modulates vincristine production in Catharanthus roseus L. propagates using Cu, Fe and Zn nano structures

Underlying mechanism of nanostructures upon monoterpene induction in Catharanthus roseus has not been explored yet. In the current study, Copper, Iron and Zinc nanoparticles were biosynthesized by Eriobotrya japonica seed extract and capped with reduced glutathione. Biosynthesized nanoparticles and their capped analogues were characterized by UV–visible spectrophotometer, FTIR, XRD and SEM. Selected concentration of nanostructures were used in plant tissue culture media which instigated the production of alkaloids, tannins and flavonoids without significantly affecting the growth index of propagated calli and shoots cultures of C. roseus. Accelerated vincristine production was noticed in propagated calli and shoots under copper and zinc nanostress (1645–1865 μg/ml respectively) with the least effect by iron nanostructure. Highest concentration of calcium was recorded in in vitro shoots under capped (3.42 mg/ml ± 7.16) and uncapped (4.41 mg/ml ± 20.44) Zn nanoparticles compared to control (2.82 mg/ml ± 13.41). Real time PCR depicts nano-zinc mediated increased expression of DAT and PRX1 genes of TIA pathway. Significant correlation among PRX1/DAT gene expression with vincristine production and calcium accumulation in the presence of nanostress validate by PCA. This study paved way the opportunities of metal biogenic nanomaterials as an ideal drug modulator in plant tissue culture studies.

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.

Zetaproteobacteria Pan-Genome Reveals Candidate Gene Cluster for Twisted Stalk Biosynthesis and Export

Twisted stalks are morphologically unique bacterial extracellular organo-metallic structures containing Fe(III) oxyhydroxides that are produced by microaerophilic Fe(II)-oxidizers belonging to the Betaproteobacteria and Zetaproteobacteria. Understanding the underlying genetic and physiological mechanisms of stalk formation is of great interest based on their potential as novel biogenic nanomaterials and their relevance as putative biomarkers for microbial Fe(II) oxidation on ancient Earth. Despite the recognition of these special biominerals for over 150 years, the genetic foundation for the stalk phenotype has remained unresolved. Here we present a candidate gene cluster for the biosynthesis and secretion of the stalk organic matrix that we identified with a trait-based analyses of a pan-genome comprising 16 Zetaproteobacteria isolate genomes. The “stalk formation in Zetaproteobacteria” (sfz) cluster comprises six genes (sfz1-sfz6), of which sfz1 and sfz2 were predicted with functions in exopolysaccharide synthesis, regulation, and export, sfz4 and sfz6 with functions in cell wall synthesis manipulation and carbohydrate hydrolysis, and sfz3 and sfz5 with unknown functions. The stalk-forming Betaproteobacteria Ferriphaselus R-1 and OYT-1, as well as dread-forming Zetaproteobacteria Mariprofundus aestuarium CP-5 and Mariprofundus ferrinatatus CP-8 contain distant sfz gene homologs, whereas stalk-less Zetaproteobacteria and Betaproteobacteria lack the entire gene cluster. Our pan-genome analysis further revealed a significant enrichment of clusters of orthologous groups (COGs) across all Zetaproteobacteria isolate genomes that are associated with the regulation of a switch between sessile and motile growth controlled by the intracellular signaling molecule c-di-GMP. Potential interactions between stalk-former unique transcription factor genes, sfz genes, and c-di-GMP point toward a c-di-GMP regulated surface attachment function of stalks during sessile growth.

Biosynthesis, Characterization and Evaluation of Biological Properties of Biogenic Gold Nanoparticles Synthesized Using Nothapodytes foetida Leaf Extract

Background and Objectives: Biogenic nanomaterials are recently being researched in biomedicine for their antioxidant, antimicrobial, anti-inflammatory and antitumor performance. In this study, gold nanoparticles (AuNPs) were biologically synthesized using Nothapodytes foetida (N. foetida), a camptothecin producing plant, to evaluate its potent cytotoxic activity against cancer cells and antimicrobial activities against human pathogenic bacteria. Methods: The AuNPs were characterized by UV-visible spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and dynamic light scattering (DLS). The antimicrobial activity of AuNPs was determined by conducting the minimum inhibitory concentration (MIC) assay on gram positive and gram negative bacteria, whereas cytotoxicity against cancer cells was assessed through the MTT assay and genotoxicity was assayed by DNA fragmentation. Results: TEM and DLS results showed the synthesis of 20-200 nm sized M. foetida AuNPs (NFAuNPs). The NFAuNPs exerted growth inhibitory effects on gram negative bacteria with the MIC for the inhibition of Eschericia coli, Pseudomonas aeruginosa being 0.15 mg/mL and 0.25 mg/mL respectively. The cytotoxicity results indicated that the sublethal concentrations of NFAuNPs for inhibiting 50% of cell growth (IC50) of cancer cells including HeLa, MCF-7 and HCT-15 after 48 h of exposure were 7.2, 9.67 and 5.28 μg/mL respectively. DNA fragmentation in cells exposed to 10-75 μg/mL of NFAuNP concentrations revealed their genotoxic effects. Conclusion: The study revealed the biogenic synthesis of AuNPs using the N. foetida plant extract and its biological potential as an antimicrobial and anticancer agent.

Magnetic properties of biogenic selenium nanomaterials.

Bioreduction of selenium oxyanions to elemental selenium is ubiquitous; elucidating the properties of this biogenic elemental selenium (BioSe) is thus important to understand its environmental fate. In this study, the magnetic properties of biogenic elemental selenium nanospheres (BioSe-Nanospheres) and nanorods (BioSe-Nanorods) obtained via the reduction of selenium(IV) using anaerobic granular sludge taken from an upflow anaerobic sludge blanket (UASB) reactor treating paper and pulp wastewater were investigated. The study indicated that the BioSe nanomaterials have a strong paramagnetic contribution with some ferromagnetic component due to the incorporation of Fe(III) (high-spin and low-spin species) as indicated by electron paramagnetic resonance (EPR). The paramagnetism did not saturate up to 50,000 Oe at 5 K, and the hysteresis curve showed the coercivity of 100 Oe and magnetic moment saturation around 10 emu. X-ray photoelectron spectroscopy (XPS) and EPR evidenced the presence of Fe(III) in the nanomaterial. Signals for Fe(II) were observed neither in EPR nor in XPS ruling out its presence in the BioSe nanoparticles. Fe(III) being abundantly present in the sludge likely got entrapped in the extracellular polymeric substances (EPS) coating the biogenic nanomaterials. The presence of Fe(III) in BioSe nanomaterial increases the mobility of Fe(III) and may have an effect on phytoplankton growth in the environment. Furthermore, as supported by the literature, there is a potential to exploit the magnetic properties of BioSe nanomaterials in drug delivery systems as well as in space refrigeration.

Biogenic zinc oxide, copper oxide and selenium nanoparticles: preparation, characterization and their anti-bacterial activity against Vibrio parahaemolyticus

The present study investigates biogenic preparation of zinc oxide (ZnO), copper oxide (CuO) and selenium (Se) nanoparticles using the marine brown alga Sargassum swartzii. The prepared nanomaterials were characterized using X-ray diffraction pattern (XRD), scanning electron microscopy (SEM) equipped with energy dispersive X-ray analysis (EDAX), transmission electron microscopy (TEM) and UV–Vis diffuse reflectance spectroscopy (DRS-UV) analysis. The particle size of biogenic ZnO, CuO and Se nanoparticles was ca. 32, 32 and 21 nm, respectively. The isolation of bacterial pathogenic strain Vibrio parahaemolyticus (V. parahaemolyticus) from the diseased shrimp and virulent genes (toxR and tlh) confirmed by PCR technique. Further, the molecular characterized using 16S ribosomal RNA gene sequences and identified new strain V. parahaemolyticus strain (GRCORNICRA001). Anti-bacterial activity of biogenic nanomaterials (ZnO, CuO and Se) was investigated against isolated V. parahaemolyticus using well diffusion method and growth inhibitory assay. The minimum inhibitory concentration (MIC) was 25, 25 and 10 µg mL−1 of ZnO, CuO and Se nanoparticles, respectively. The results show that there is a strong bacterial inhibition in a dose-dependent manner. Further, SEM analysis revealed that the interaction of nanomaterials with V. parahaemolyticus, resulted in a surface tension change that leads to membrane depolarization, formation of abnormal textures such as membrane rupture, membrane blebs, membrane clumping, and also caused cell death. Results of this effort highlighted the way for the future that these nanomaterials incorporated with shrimp feed for the management of aquatic diseases.

Fungal Nanophase Particles Catalyze Iron Transformation for Oxidative Stress Removal and Iron Acquisition

Microbe-mineral interactions have shaped the surface of the Earth and impacted the evolution of plants and animals. Although more than two-thirds of known mineral species have biological imprints, how the biotransformation of minerals may have benefited microbial development, beyond nutritional and energetic use, remains enigmatic. In this research, we have shown that biogenic ferrihydrite nanoparticles are extensively formed at the interface between an actively growing fungus and an iron-containing mineral, hematite. These biogenic nanoparticles formed through the fungus-hematite interactions can behave as mimetic catalysts, similar to nanozymes that imitate peroxidase, which scavenges hydrogen peroxide for the mitigation of potential cytotoxicity. Evidence from various X-ray spectroscopic analyses indicated that non-lattice oxygen in the nanomaterials was chiefly responsible for this catalytic activity, rather than through the conventional mechanisms of iron redox chemistry. Cryo-scanning electron microscopy, high-resolution (∼30nm) 3D volume rendering, and biomass analyses further confirmed that the organism was active and capable of mediating the catalytic reactions. We therefore hypothesize that this confers an advantage to the organism in terms of protection from oxidative stress and ensuring the acquisition of essential iron. This work raises new questions about the roles of biogenic nanomaterials in the coevolution of the lithosphere and biosphere and provides a step toward understanding the feedback pathways controlling the evolution of biogenic mineral formation.

Biogenic nanoparticles as immunomodulator for tumor treatment.

In the past few decades, cancer immunotherapy has developed rapidly. Cancer immunotherapy, either used alone or in combination with a variety of immunotherapies (such as cancer therapeutic vaccines, adoptive cell therapy, or immune checkpoint blocking therapy), is a very attractive class of cancer therapy. However, so far, the clinical effect of most cancer immunotherapy is not satisfactory. It has been widely recognized that nanotechnology can enhance the efficacy of cancer immunotherapy. A variety of biogenic nanoparticles have been developed, which have excellent immunogenicity and modifiability, and can carry tumor therapeutic drugs to achieve combined therapy, so as to improve the effectiveness and durability of antitumor immunity while reducing adverse side effects. In this review, we summarized the key parameters and futures of three kinds of biogenic nanomaterials in cancer immunotherapy; we highlighted the progress of cancer immunotherapy based on outer membrane vesicles, virus-like particles, and exosomes. This article is categorized under: Therapeutic Approaches and Drug Discovery > Nanomedicine for Oncologic Disease Nanotechnology Approaches to Biology > Nanoscale Systems in Biology.

Insight on thermal stability of magnetite magnetosomes: implications for the fossil record and biotechnology

Magnetosomes are intracellular magnetic nanocrystals composed of magnetite (Fe3O4) or greigite (Fe3S4), enveloped by a lipid bilayer membrane, produced by magnetotactic bacteria. Because of the stability of these structures in certain environments after cell death and lysis, magnetosome magnetite crystals contribute to the magnetization of sediments as well as providing a fossil record of ancient microbial ecosystems. The persistence or changes of the chemical and magnetic features of magnetosomes under certain conditions in different environments are important factors in biotechnology and paleomagnetism. Here we evaluated the thermal stability of magnetosomes in a temperature range between 150 and 500 °C subjected to oxidizing conditions by using in situ scanning transmission electron microscopy. Results showed that magnetosomes are stable and structurally and chemically unaffected at temperatures up to 300 °C. Interestingly, the membrane of magnetosomes was still observable after heating the samples to 300 °C. When heated between 300 °C and 500 °C cavity formation in the crystals was observed most probably associated to the partial transformation of magnetite into maghemite due to the Kirkendall effect at the nanoscale. This study provides some insight into the stability of magnetosomes in specific environments over geological periods and offers novel tools to investigate biogenic nanomaterials.

Studies on Antioxidant and Antimicrobial Potential of Biogenic Silver Nanoparticles Synthesized Using Nothapodytes foetida Leaf Extract (Wight) Sleumer

Introduction In recent years biogenic nanomaterials have emerged with an immense scope in biomedicine as these nanostructures are proved to combat against deadly communicable and non-communicable diseases. Intensifying application of antibiotics in therapeutics endorsed multidrug resistance (MDR)