Mitochondria are a cell's powerhouse and also have a vital part in cellular processes. The emerging role of mitochondria in several crucial processes highlights their cellular and physiological importance. Mitochondrial homeostasis mechanisms, including proteostasis pathways, are vital for mitochondrial health. Failure of these processes has an important role in establishment of numerous complex disease conditions, such as neurodegeneration and imperfect ageing. However, details of mitochondrial impairments and their contribution to the pathology of neurodegeneration are poorly understood. This review systematically discusses the involvement of mitochondrial homeostasis mechanisms and their role in rejuvenating cellular health and fitness. We also focus on various cellular protein quality control mechanisms essential for mitochondrial proteostasis and how their failure leads to mitochondrial functional disturbances observed in disease conditions. We discuss recent findings based on mitostasis-associated chaperones, mitoproteases, and autophagy responses, which can lead to emergence of new possible therapeutic interventions against complex diseases. (Figure presented.).

We highlight the importance of plastic waste management in research laboratories for practicing sustainable development goals.

Nanomedicine is increasingly being utilized in addressing various eye ailments and holds immense potential in rectifying ocular diseases; however, the interactions between nanomedicines and their route of administration via tear fluid remain poorly understood. When nanoparticles are introduced into the tear fluid, a layer of protein corona is formed on their surface that not only influences the properties and biological fate of nanoparticles but also potentially interferes with the function of endogenous proteins. To investigate the interactions between gold nanoaprticles (AuNPs) and tear fluid, focusing on the physicochemical changes of the particles, and to quantitatively and qualitatively identify the key proteins involved in the corona formation, we employed label-free techniques for material and biophysical characterizations along with proteomic analyses and mass spectrometry. The AuNPs remained stable without forming aggregates, showing only an ∼31 nm increase in hydrodynamic diameter after interacting with tear fluid. Notably, their overall zeta potential increased significantly from −12 to −23 eV due to the supplemented charge by the adsorbed proteins. Proteomic analysis and liquid chromatography/mass spectrometry (LC-MS/MS) identified 31 proteins that were bound with the nanoparticles from a total of 174 proteins that were detected in the tear fluid. Bioinformatic classification revealed an enrichment of specific proteins essential for ocular health; proteins such as clusterin, lactotransferrin, adenosine triphosphate (ATP) synthase, lysozyme, alpha enolase, keratin, apolipoprotein, and epidermal growth factor receptor (EGFR) with pivotal roles in anti-inflammatory, immune response, cell adhesion, cellular organization, plasminogen activation, cell signaling, stress response, and corneal epithelial homeostasis. Overall, our study provides an unresolved comprehensive map of the tear protein corona landscape and its impact on nanoparticle behavior in the tear fluid. These insights must be considered and are valuable for designing safer and more effective nanomedicines for the treatment of various eye diseases.

Persistent organic pollutants (POPs) pose significant environmental and biological risks due to their stability and bioaccumulation in the food chain, often facilitated by contamination from sewage water. Monitoring POPs is crucial for assessing their detrimental environmental impacts and preventing related health issues. Conventional analytical techniques for detecting POPs typically require labeling, energy-intensive, and cost-effective equipment, can be time-consuming, and may alter the properties of analytes. In this study, we demonstrate a label-free biosensing approach utilizing spoof surface plasmon polaritons (SSPP) for the rapid and sensitive detection of commonly encountered POPs (including textile and paper dyes, worn-out antibiotics, and herbicides) in sewage water. Inspired by plasmonic, our results show that SSPP biosensors exhibit excellent sensitivity and selectivity for POPs in sewage water samples as small as 0.634 mL. Additionally, we validate the performance of our biosensors using real-time sewage water samples spiked with widely prevalent and harmful POPs, showcasing their practical utility in complex environmental matrices. This study underscores the potential of SSPP-based biosensing as a powerful tool for the label-free detection of POPs in sewage water, offering a rapid, sensitive, and cost-effective solution for monitoring environmental pollutants. Our findings contribute to water quality assessment efforts and the development of effective pollution mitigation strategies.

Natural materials with anomalous molecular machinery and hierarchies are gaining tremendous recognition in the pursuit of environmentally friendly, sustainable supports via noble metal anchoring for the analysis of organic pollutants. Herein, for the first time, we demonstrate the in situ biofabrication of AuNPs stringently tethered within snipped human nails, materialised by the hydroxy amino acids structured within the collagenous nail, which exhibit high reductive potential and Au affinity. Material characterization revealed a firm assemblage of large truncated AuNPs, including triangles, pentagons, hexagons and octagons of sizes between ∼80 and 150 nm, embedded within the highly rigid and compact three-dimensional nail, ensuring durability, shelf-life and stability against diverse physicochemical environments. Furthermore, large truncated AuNPs with sharp edges can intensify localized electromagnetic fields as “hotspots” for the direct SERS detection of organic analytes. This is validated by exposing real dye adulterants at nanomolar regimes, detecting acid orange at concentrations of 0.173-0.206 ppm in red chillies (spice) and 0.087-0.140 ppm of malachite green in green peas (pulse) collected from three distantly far vegetable markets in a radius of ∼37.28 miles. Overall, we present a highly stable, human nail waste biofabricated Au bio-substrate as a sustainable and generalized sensing technique for the identification and quantification of unsafe molecular adulterants in food samples using SERS.

Despite a decade of research and exploitation of fish scales for several applications, there is no report on fabricating supported catalysts for catalysis. Herein, simply by exploiting the metal binding and reductive potential of fish scales we autogenically bioengineered golden supported catalysts of ∼1.5 ± 0.4 cm2, sustainably. Providentially, the catalyst acquired mechanical sturdiness (∼65 ± 9 MPa), durability, flexibility, absorbency, and stability against diverse physicochemical barriers. Uniquely, these remarkable characteristics enabled the catalyst for reaction suitable fixative-batch or continuous flow catalysis, a rare compatibility. This was validated by performing large-volume (5 L) degradation of the textile sewage dye 4-nitrophenol (30 mg/L) at a (k) of 0.07 min-1, parallelly generating gram-scale quantities of 4-AP with a turnover frequency of 108 h-1. The continuous flow reactor was operable at a high flow rate of 1.5 mL/min, accommodating a high reduction of 4-NP of over 94%. Most importantly, the wide area of our catalyst made it feasible to hand-retrieve or exchange the catalyst for recycling and monitoring the reaction kinetics without the need for energy intensive processes. Finally, the collagenous biological nature of the support permitted ∼74 ± 5% recovery of gold by etching in Aqua-Regia. Overall, our biowaste-valued, cost-efficient, hand-retrievable, mechanically sturdy, and resilient catalyst with a highly flexible and durable nature can be generalized for reactor specific practical implementation of large scale heterogeneous catalysis.

The development of efficient and reusable supported catalysts is key to promoting eco-friendly catalytic processes in both research and industry. In this work, we present a bioengineered golden sponge catalyst, created by leveraging the natural metal-binding and reducing abilities of dried loofah (Luffa aegyptiaca) sponge. This sustainable, sponge-like catalyst can be easily cut into various sizes (up to 15 × 4 cm2), making it convenient for use, removal, and reuse. Thanks to its high absorptivity (~ 4.29 mL/g) and open fibrous structure (~ 0.5 ± 0.1 cm2), a single piece of this catalyst can rapidly process up to 2 L of 4-nitrophenol solution (15 mg/L), achieving a high reaction rate of 0.41 min⁻1. The gold nanoparticles (AuNPs) are strongly anchored to the loofah fibers, combining with their natural mechanical strength to provide excellent chemical stability, efficient adsorption, and compatibility with real-time reaction monitoring and intermediate analysis. Even after use, the loofah's carbon-rich nature allows for effective gold recovery (~ 85.5 ± 8%) using Aqua Regia, making the system both cost-effective and sustainable. This study demonstrates the promise of natural, bio-derived materials as resilient, scalable, and hand-exchangeable catalysts for detoxifying harmful effluents.

Ultra-stable and biocompatible gold nanoparticles (AuNPs) are essential for targeted nanomedicine, facilitating extended circulation, minimal immunogenicity, and efficient cellular uptake. Despite its status as a gold standard for attaining biocompatibility and stability, polyethylene glycol (PEG) faces increasing scrutiny due to its physiology-associated accelerated blood clearance, immunogenicity, and restricted nuclear access, prompting an urgent shift toward alternative surface engineering strategies. This is an extension of our previous study where we fabricated ultra-stable AuNPs using base-etched fish scales, exhibiting PEG-Au comparable physicochemical, mechanical and biofluidic stability. Herein, through integrated surface characterization studies, MALDI-TOF, LC-MS/MS and bioinformatics profiling, we elucidate the shielding oligopeptide consortium that modulates the particles’ biomolecular interactions while preserving biofluidic integrity and colloidal stability. Cytotoxicity assays and mechanistic studies of cellular uptake confirmed that the oligopeptylated-AuNPs are non-toxic and are endocytosed via clathrin- and scavenger-mediated receptors. Remarkably, ultra-microtome-assisted HR-TEM revealed that our nanocargos could successfully get imported into the nucleus, a rare and highly significant phenomenon, for such non-viral delivery systems. Collectively, our findings position our sustainably bioengineered oligopeptylated-AuNPs as next-generation nanocargos that uniquely integrate biocompatibility, stealth properties and nuclear-targeting capability, offering a versatile and promising platform to enable precision delivery of therapeutic payloads at subcellular resolutions.

The stability and dispersity of gold nanoparticles (AuNPs) against diverse biological, physicochemical, and physiological transformations while retaining biocompatibility are fundamental for their myriad utilization in various theragnostic applications. This comprehensive review provides a comprehensive analysis of the principles governing the colloidal stability of AuNPs and the factors influencing their physicochemical, chemical, and biological stability. Key parameters such as resistance to aggregation in aqueous and biological medium, stability under physiological pH and ionic conditions, and the impact of protein corona formation on nanoparticle functionality are illustrated in detail. Diverse surface engineering strategies that are employed for achieving ultra-stable AuNPs, including electrostatic and steric stabilization methods are explored. Attention is also given to the widely used polymers like polyethylene glycol, polyvinylpyrrolidone, polyethylenimine, poly(lactic-co-glycolic acid), and polydopamine, which have demonstrated significant efficacy in enhancing nanoparticle stability under physiological conditions along with their controversies and negative impacts. Alternatively, the emergence of safe bioconjugation strategies using proteins, peptides, and nucleic acids that offer promising pathways to improve biocompatibility and facilitate targeted applications are discussed. We also highlight the emerging sustainable approaches for AuNP stabilization using resilient biomolecules such as glycans, lipids, and plant-derived phytochemicals. Innovations like fish-scale-derived proteins and glycan-based coatings showcase the potential of biogenic methodologies to provide ultra-stable nanoparticles with minimal environmental impact. By advancing sustainable and innovative surface engineering strategies, this review underscores the potential for ultra-stable, biocompatible AuNPs to drive safer, more effective solutions in nanomedicine while reducing the ecological footprint of their production. The objective of this review is to systematically present both conventional and emerging strategies for stabilizing AuNPs, with a particular focus on sustainable, biocompatible, and high-performance approaches that support safer and more effective applications in nanomedicine. Unlike existing reviews that primarily focus on classical polymer-based stabilization or biomedical applications alone, this work uniquely integrates a critical evaluation of conventional polymers with a comprehensive overview of innovative, eco-friendly biogenic alternatives. It emphasizes the dual imperative of performance and sustainability, offering a forward-looking framework for designing next-generation AuNPs with minimal ecological impact.

Surface Enhanced Raman Scattering (SERS) is emerging as a potent analytical tool for the detection of various pollutants in complex environments due to its distinctive vibrational fingerprint ability and pronounced detection sensitivity. Precautious of adverse blue-green economies and ecological impacts, sustainable generation of SERS active substrates and analyte casting matrices are getting prioritized. Herein, gold nanoflowers (AuNFs) of ∼75 ± 15 nm were initially biofabricated using an expended cell culture medium as a one-step synthesis cum stabilization strategy. Then the heavy architecture of multi-faceted AuNFs with deep pits and edges, that acted as hotspots for enhancing the localized electromagnetic fields, was utilized for the direct SERS detection of commonly used carcinogenic herbicides collected from agro-farms at nanomolar regimes with 0.44 ppm and 0.27 ppm for Glyphosate and amino methyl phosphonic acid, respectively. Such a low level detection is superior by 8.33% when compared to the reported values. Computational finite-difference time-domain (FDTD) simulations affirmed the enhanced SERS effect from the multi-faceted nanostructure of AuNFs with structural heterogeneities that provide numerous hotspots to amplify the localized electromagnetic field. More eminently, fish scale derived biotemplate through AuNF-analyte drop casting contributed to the exceptional intensities, attributed to the naturally grooved hierarchically porous hydrophilic lamellar structures contact angle of 73°. Overall, the adapted bioengineering of SERS substrate is safe, robust, affordable and reproducible, fostered by bioderived durable biomatrix offering potent sustainable SERS detection of various biomedically and environmentally relevant molecules.

Glyphosate (Gly) is a massively utilized toxic herbicide exceeding its statutory restrictions, causing adverse environmental and health impacts. Engineered nanomaterials, even though are integral to remediate Gly, their practical use is limited due to time and energy driven purifications, and negative environmental impacts. Here, a 3D wide area (~1.6 ± 0.4 cm2) Cu2O nanoparticle supported biotemplate is designed using fish-scale wastes as a sustainable approach for the ultra-efficient and selective hand-remediation of Gly from real-time samples from agro-farms. While the innate metal binding and reducing ability of collagenous scales aided self-synthesis cum grafting of Cu2O, the selective binding potential of Cu2O to Gly facilitated its hand-retrieval; as assessed using optical characterizations, Fourier transform infrared spectroscopy, thermogravimetric analysis and liquid chromatography mass spectrometry. Optimization studies revealed extractions of diverse pay-loads of Gly between 0.1 μg/mL to 40 μg/mL per 80 mg biotemplate grafted with ~6.354 μg of sub-5 nm Cu2O and was exponential to the number of Cu2O@biotemplates. Even though pH and surfactant didn't have any impact on the adsorption of Gly to the Cu2O@biotemplates, increase in the ionic strength led to a drastic increase in the adsorption. Density function theory simulations unveiled the involvement of phosphonic and carboxylic groups of Gly for interaction with Cu2O with a bond length of 1.826 Å and 1.833 Å, respectively. Overall, our sustainably generated, cost-efficient, hand-retrievable Cu2O supported biotemplate can be generalized to extract diverse organophosphorus toxins from agro-farms and other sewage embodiments. Synopsis: Glyphosate is an excessively applied herbicide with potent health hazards and carcinogenicity. Thus, a hand removable Cu2O-supported biotemplate to selectively and efficiently remediate glyphosate from irrigation water is developed.

Nanocatalysts are extremely crucial for the expedited synthesis of various chemicals, fuels, and pharmaceutical molecules both in academia and industry. To overcome the limitations of nanocatalysts and or microstructure supported catalysts such as agglomeration (due to inter-particle dipolar forces preventing longer shelf-lives), compromised catalytic activity (e.g., nickel-titanium dioxide bimetallic catalyst, showed high selectivity to hydrogenate 3-nitrostyrene into 3-vinylaniline (90.2 %) compared to unmodified nickel (55.3 %), due to metal-plane formation by titanium dioxide), cytotoxicity (with over 90 % cell killing in the presence of the nanocatalysts above ∼ 0.2 mg/mL), catalyst retrieval (demanding energy intensive procedures such as centrifugation (∼10,000 g and above), membrane filtrations (∼0.2 µm), magnetic separations (0.9–1.1 T) and absurd practical implementation there is a tremendous development of 3-dimensional wide-area supported catalysts. This review update the readers on the evolution of highly catalytic nanoparticles for various heterogeneous catalysis. Uniquely, wide-area supported catalysts wherein the nanoparticles are grafted to 3-dimensional nature-inspired or pristine natural materials as sustainable strategies are discussed. The role of wide-area of the support in overcoming the limitations of nanocatalysts and microstructures by enabling bidirectional reactant access, catalyst efficiency, reusability, stability and sustainability are highlighted. Next, we focus on the metal-affinity and redox-potential of the natural support that aid autogenic biosynthesis and self-assembly of nanocatalysts. Followed by discussions on supplementary properties of the support such as type, structural-hierarchy, surface-area, absorption, porosity and rigidity in tuning the stability, biodegradability, compatibility, functionality and performance of the catalyst. Accentuated, with the impact of support in dictating the choice of fixed batch vs continuous flow reactors, co-relative to modulating the catalytic efficiency and turnover frequencies. Finally, the exclusive role of wide-area of the support and its biological nature in allowing the extraction of noble precursor off the support after catalyst poisoning is emphasized. These discussions, for the first time, spotlight the versatility, resilient nature of the emerging ultra-efficient wide-area supported catalysts that are generated using sustainable procedures for diverse large-volume heterogeneous catalysis.

Treating sewage waters contaminated with persistent organic pollutants (POPs) presents a pressing environmental concern, mandating, affordable, implementable and sustainable remediations. Supported catalysts, wherein metal nanoparticles are grafted onto inert supports to endow porosity, reactant access, performance and catalyst re-use are emerging as sustainable catalytic platforms. Herein, size-controllable, mechanically recyclable 3D-Cu2O@megacatalyst of ∼81 ± 5 cm2, ∼37 ± 3 cm2 and ∼1 ± 0.6 cm2 were biofabricated by exploiting the innate metal binding feature of pristine eggshells. The as-fabricated Cu2O@megacatalyst was utilized for the Fenton-like treatment of POPs, with exceptional activities against diverse molecules: antibiotic (tetracycline (TC)), textile dye (methylene blue) and pharmaceutical precursor (4-nitrophenol) with the degradation efficiencies of 95.6 %, 96.8 % and 93.4 %, respectively. Optimization studies revealed that our megacatalyst can function consistently in the presence of various oxidising agents, free radical scavengers, wide pH, temperatures and inorganic and organic contaminants. The catalyst demonstrated stability and catalytic efficiency in different real-time water matrices: ultrapure water-95.6 %, tap water-84 %, lake water-86 %, and river water-91 %. Furthermore, plausible reaction mechanism and decomposition pathways for TC degradation were assessed using GC-MS, while evaluating the toxicity using ECOSAR and oxygen uptake assay, which revealed less toxic reaction intermediates and end products. Overall, our results provide new insight into the sustainable development of a generalized highly stable, scalable, ultra-efficient and mechanically recyclable Fenton-like supported catalyst for the detoxification of POPs in sewage waters.

Biological materials with unique surface properties provide a new avenue for fabricating green and sensitive SERS-active substrates. Herein, we present a simple but efficient method to prepare surface-enhanced Raman scattering (SERS) substrates by depositing silver nanoparticles (AgNPs) on fish scale substrates using an evaporation-induced self-assembly method (EISA). Characterization of the formed flexible Ag-impregnated substrate proved outstanding SERS sensitivity, uniformity, and reproducibility properties, with a Raman enhancement factor of 1.3 × 106 and a relative standard deviation of 6.4 %. Using this powerful fish scale substrate, a toxic environmental pollutant perfluorooctane sulfonamide (PFOSA) was indirectly detected in lake water, soil, and human urine samples. Due to its chemical structure, it is difficult to detect low concentrations of PFOSA in real samples. Interestingly, malachite green (MG) was smartly used as the Raman label for PFOSA detection in real samples. One of the main appeals is that the concentration of PFOSA can be correlated with a decrease in the SERS signal of MG in real samples. In conclusion, the strategy employed and reproducible SERS substrates may have diverse applications in clinical and environmental analyses.

The stability and dispersity of gold nanoparticles (AuNPs) against various biological, physicochemical, and physiological transformations while retaining biocompatibility are fundamental for their myriad utilization in various theragnostic applications. Besides, it would be highly imperative if the AuNPs could be generated using environmentally sustainable procedures. Remarkably stable, monodispersed AuNPs with robustness against centrifugation, freeze-thawing, lyophilization, acids, bases, electrolytes, and polar solvents are generated by utilizing fish scale wastes. The AuNPs inherited self-integrity and dispersity across various clinically significant biological fluids including phosphate buffer saline, growth mediums, human blood serum, saliva, and urine. Human blood serum interactions revealed negligible protein corona consortium and biocompatibility with no hemolysis or cytotoxicity toward peripheral blood mononuclear cells. Astonishingly, endurance to all these biological, physicochemical, and physiological discrepancies was comparable to that of universal stabilizer thiolated polyethylene glycol (PEG) sorbed AuNPs. Such high stability and wide dispersity are attributed to the firm shielding of AuNPs by the oligopeptide fragments excreted from the scales, which also endowed AuNP functionalization to diverse drugs. Notably, our results develop a biogenic production of monodispersed AuNPs with natural sturdiness against harsh laboratory and clinical environments to substitute the plunged biocompatibility of PEG-Au sulfur chemisorption and PEG-Au physisorption approaches for various imaging and drug delivery applications.

A prolonged healthy life is based on the optimal activity of an organism's organ systems, and healthy cells are at the core of this proper functioning. Cellular homeostasis is of utmost importance, and a cell deploys several cytoprotective mechanisms to maintain this balance. One such mechanism is protein quality control (PQC) to preserve proteostasis and maintain functionality of proteins. In PQC, the chaperone system and proteolytic pathways like autophagy and ubiquitin-proteasome system (UPS) are primary cell devices preventing misfolding/aggregation of proteins and clearing out toxic protein aggregates and dysfunctional organelles. Aging is an unavoidable biological phenomenon observed in many organisms that negatively affects the functionality of multiple organs systems, thus reducing the life span. It constitutes a significant risk factor for impairment of PQC elements and proteostasis disruption, linked with physiological dysfunction of organelles along with other anomalies. Aging presents various medicinal challenges as it affects multiple physiological processes at once. In aging, declined PQC capacity can lead to increased incidence of several age-associated diseases, including neurodegenerative disorders. Proper maintenance and modulation of these PQC elements present an attractive therapeutic intervention opportunity for such disorders. Here, we present PQC and its components as a system affected in imperfect aging, its potential for modulation to improve healthspan and counter aging associated disorders, along with challenges linked with inherent complex nature of aging biology.

Automated classification of blood cells from microscopic images is an interesting research area owing to advancements of efficient neural network models. The existing deep learning methods rely on large data for network training and generating such large data could be time-consuming. Further, explainability is required via class activation mapping for better understanding of the model predictions. Therefore, we developed a Siamese twin network (STN) model based on contrastive learning that trains on relatively few images for the classification of healthy peripheral blood cells using EfficientNet-B3 as the base model. Hence, in this study, a total of 17,092 publicly accessible cell histology images were analyzed from which 6% were used for STN training, 6% for few-shot validation, and the rest 88% for few-shot testing. The proposed architecture demonstrates percent accuracies of 97.00, 98.78, 94.59, 95.70, 98.86, 97.09, 99.71, and 96.30 during 8-way 5-shot testing for the classification of basophils, eosinophils, immature granulocytes, erythroblasts, lymphocytes, monocytes, platelets, and neutrophils, respectively. Further, we propose a novel class activation mapping scheme that highlights the important regions in the test image for the STN model interpretability. Overall, the proposed framework could be used for a fully automated self-exploratory classification of healthy peripheral blood cells. Graphical abstract: The whole proposed framework demonstrates the Siamese twin network training and 8-way k-shot testing. The values indicate the amount of dissimilarity. [Figure not available: see fulltext.]

Advent in nanoscience and nanotechnology has opened new avenues in terms of nanoparticle utilization as novel drug delivery cargos to fight various pathogens. The essential salient features of these nano-cargos along with the surface chemistries that are involved to accommodate drug modalities are described. Emerging aspects of selective targeting mechanisms including pH trigger, systemic responses, overexpression of relevant biomolecules and controlled release are highlighted illustrating suitable examples. Finally, limitations on the use of nano-carriers for drug delivery and various strategies that are implemented to overcome the bio-hurdles are presented.

Antimicrobial resistance threatens the effective treatment of ever increasing infections caused by various microorganisms. Antimicrobial potential of silver nanoparticles opened up a new frontier for better therapeutic interventions over the emerging multidrug-resistant pathogens and short shelf life of various drugs. This chapter provides a robust strategy for targeting various multidrug-resistant microorganisms with least nonspecific reactivity. The mechanisms by which silver nanoparticles induce microbicidal activity in terms of DNA damage, membrane rupture, interference with the cellular biomolecules, generation of free radicals induced reactive oxygen species, and dissolution of ions are discussed. Finally, the defence responses of these microbes toward silver nanoparticles are illustrated.

Blood group analysis has evolved from conventional “test-tube” to ingenious “lab-on-a-chip” micro/paper-fluidic devices for identifying blood phenotypes. Despite the rapid and economical fabrication of these devices, they require Whatman paper that is obtained by cutting down trees and plastic usage involving complex and sophisticated facilities, making scalable manufacturing laborious and expensive. Most importantly, deforestation and plastic incineration pose great threats to the biotic and abiotic environments. Here, we have developed a blood grouping strip utilizing fish-scale waste and household cardboard-waste generated origami as an affordable and sustainable strategy. The naturally inherited hydrophilicity of fish scale with a contact angle of 89° could succinctly auto-stabilize low-volume antisera without the aid of additives. Moreover, unlike paperfluidics, antisera absorption, as well as RBC-antisera agglutination upon blood introduction, happens on the spot with no capillary wicking. The merits of our technique are: it requires a low amount of blood (3 μL), eliminates additional image processing and assays, is equipment-free, and aids accurate blood typing as a visual hemagglutination readout. Additionally, a high tensile strength of ∼85 ± 5 MPa and the shelf-endurance of the bio-disc allowed us to use the simplest cardboard origami as a shield, obviating plastic and fiber generated fancy shields, making our device portable and simultaneously biodegradable. Our novel bio-disc blood analysis was tested with anonymous blood samples (n = 200), with an accuracy comparable to a standard blood group assay. This zero-cost paper, plastic-free eco-friendly blood group analyser derived from biodegradable food and cardboard waste as a resourceful technique has huge potential in various sensors and point-of-care diagnostics, especially in impoverished areas with limited or no lab facilities.

Cancer therapy is a fast-emerging biomedical paradigm that elevates the diagnostic and therapeutic potential of a nanovector for identification, monitoring, targeting, and post-treatment response analysis. Nanovectors of superparamagnetic iron oxide nanoparticles (SPION) are of tremendous significance in cancer therapy because of their inherited high surface area, high reactivity, biocompatibility, superior contrast, and magnetic and photo-inducibility properties. In addition to a brief introduction, we summarize various progressive aspects of nanomagnets pertaining to their production with an emphasis on sustainable biomimetic approaches. Post-synthesis particulate and surface alterations in terms of pharmaco-affinity, liquid accessibility, and biocompatibility to facilitate cancer therapy are highlighted. SPION parameters including particle contrast, core-fusions, surface area, reactivity, photosensitivity, photodynamics, and photothermal properties, which facilitate diverse cancer diagnostics, are discussed. We also elaborate on the concept of magnetism to selectively focus chemotherapeutics on tumors, cell sorting, purification of bioentities, and elimination of toxins. Finally, while addressing the toxicity of nanomaterials, the advent of ultrasmall nanomagnets as a healthier alternative with superior properties and compatible cellular interactions is reviewed. In summary, these discussions spotlight the versatility and integration of multi-tasking nanomagnets and ultrasmall nanomagnets for diverse cancer theragnostics.

Metal nanoparticles grafted within inert and porous wide-area supports are emerging as recyclable, sustainable catalysts for modern industry applications. Here, we bioengineered gold nanoparticle-based supported catalysts by utilizing the innate metal binding and reductive potential of eggshell as a sustainable strategy. Variable hand-recyclable wide-area three-dimensional catalysts between ∼80 ± 7 and 0.5 ± 0.1 cm2 are generated simply by controlling the size of the support. The catalyst possessed high-temperature stability (300 °C) and compatibility toward polar and nonpolar solvents, electrolytes, acids, and bases facilitating ultra-efficient catalysis of accordingly suspended substrates. Validation was done by large-volume (2.8 liters) dye detoxification, gram-scale hydrogenation of nitroarene, and the synthesis of propargylamine. Moreover, persistent recyclability, monitoring of reaction kinetics, and product intermediates are possible due to physical retrievability and interchangeability of the catalyst. Finally, the bionature of the support permits ∼76.9 ± 8% recovery of noble gold simply by immersing in a royal solution. Our naturally created, low-cost, scalable, hand-recyclable, and resilient supported mega-catalyst dwarfs most challenges for large-scale metal-based heterogeneous catalysis.

UV-Vis spectroscopy is a versatile analytical tool used to examine the nature of various synthetic, biological and clinical molecules for pharmaceutical and environmental applications. The analysis is typically performed in a "cuvette or microplate"that is made of either high-priced quartz or eco-unfriendly plastic materials. Besides, cuvettes and microplates require a plethora of analyte volumes between 100 μL-5 mL that is unfeasible for expensive, rare and high-risk analytes. Herein, we have developed a low-cost sustainable biotemplate derived from fish scales for analysing the absorbance of various sub-10 μL analytes. Naturally acquired transparency enabled optical transmittance above ∼80% in the broad visible and near IR spectrum of 350-900 nm permitted accurate measurements. Most importantly, droplet retention over 30 minutes against gravity with the vertically aligned biotemplate supported such ultra-low volume measurements as well as monitoring of chemical reactions in situ. Moreover, the non-impregnated analyte droplets could be retrieved post-analysis due to the marginally porous hierarchically layered hydrophilic biotemplate with a contact angle of 79°. A customized reusable low-cost 3D-printed adapter was fabricated to position the biotemplate inside the cuvette slot. The biotemplate exhibited excellent compatibility to detect diverse chromophores such as organic dyes, bacteria, nanoparticles, quantum dots, proteins and metallic suspensions by revealing their corresponding absorbances. As a proof-of-concept, we demonstrated the on-biotemplate catalytic dye degradation analysis with an R2 value of 0.98, and the BSA standard assay to quantify as low as 50 μg mL-1 proteins with comparable sensitivities to that of microplate and quartz cuvettes. Finally, large-scale production has been demonstrated by generating ∼3000 biotemplates at an economical price of only Rs. 106 ($1.44). This ultralow-cost, plastic-free, use-and-throw biodegradable transparent biotemplate prepared from food waste as a bioresource stratagem has huge potential in routine scientific and pharmaceutical UV-Vis analytics.

A generalized method for sorting nanoparticles based on their cores does not exist; it is an immediate necessity, and an approach incorporating cost-effectiveness and biocompatibility is in demand. Therefore, an efficient method for the separation of various mixed core-compositions or dissimilar metallic nanoparticles to their pure forms at the nano-bio interface was developed. Various simple core-combinations of monodispersed nanoparticles with dual cores, including silver plus gold, iron oxide plus gold and platinum plus gold, to the complex three-set core-combinations of platinum plus gold plus silver and platinum plus iron plus gold were sorted using step-gradient centrifugation in a sucrose suspension. Viscosity mediated differential terminal velocities of the nanoparticles permitted diversified dragging at different gradients allowing separation. Stability, purity and properties of the nanoparticles during separation were evaluated based on visual confirmation and by employing advanced instrumentations. Moreover, theoretical studies validated our experimental observations, revealing the roles of various parameters, such as the viscosity of sucrose, the density of the particles and the velocity and duration of centrifugation, involved during the separation process. This remarkably rapid, cost-efficient and sustainable strategy can be adapted to separate other cores of nanoparticles for various biomedical research purposes, primarily to understand nanoparticle induced toxicity and particle fate and transformations in natural biotic environments.

Silver nanoparticle-aided enhancement in the anti-corrosion potential and stability of plant extract as ecologically benign alternative for microbially induced corrosion treatment is demonstrated. Bioengineered silver nanoparticles (AgNPs) surface functionalized with plant extract material (proteinacious) was generated in vitro in a test tube by treating ionic AgNO3 with the leaf extract of Azadirachta indica that acted as dual reducing as well as stabilizing agent. Purity and crystallinity of the AgNPs, along with physical and surface characterizations, were evaluated by performing transmission electron microscopy, Fourier transform infrared spectroscopy, energy dispersive x-ray spectra, single-area electron diffractions, zeta potential, and dynamic light scattering measurements. Anti-corrosion studies against mild steel (MS1010) by corrosion-inducive bacterium, Bacillus thuringiensis EN2 isolated from cooling towers, were evaluated by performing electrochemical impedance spectroscopy (EIS), weight loss analysis, and surface analysis by infrared spectroscopy. Our studies revealed that AgNPs profoundly inhibited the biofilm on MS1010 surface and reduced the corrosion rates with the CR of 0.5 mm/y and an inhibition efficiency of 77% when compared to plant extract alone with a CR of 2.2 mm/y and an inhibition efficiency of 52%. Further surface analysis by infrared spectra revealed that AgNPs formed a protective layer of self-assembled film on the surface of MS1010. Additionally, EIS and surface analysis revealed that the AgNPs have inhibited the bacterial biofilm and reduced the pit on MS1010. This is the first report disclosing the application of bioengineered AgNP formulations as potent anti-corrosive inhibitor upon forming a protective layer over mild steel in cooling water towers.

Chromatography is emerging as an efficient technique for the separation of engineered nanoparticles (NPs) and has been gaining tremendous attention due to its ease, facile, and cost-effective nature. This chapter puts together the various chromatography techniques so far implemented to separate or fractionate various NPs in detail. The influence of morphological features of the NPs along with overall surface properties that can aid their separation using chromatography will be highlighted. Finally, this chapter also provides an overview of the various analytical and advanced physical characterization techniques often used to evaluate the successful separation of nanoparticles.

The first intermolecular ring-expansion cascade of azirines with alkynes for the synthesis of pyridines, enabled by a copper/triethylamine catalytic system via simultaneous generation and utilization of yne-enamine and skipped-yne-imine intermediates, is reported. Experimental as well as computational mechanistic studies revealed that the role of triethylamine is crucial in deciding the reaction pathway toward the pyridine products. This process offers a novel, one-step, direct, and practical strategy for the rapid construction of highly substituted pyridines under exceedingly mild conditions, and an installed alkyne functionality.

Production of AgNPs with desired morphologies and surface characteristics using facile, economic and non-laborious processes is highly imperative. Cell extract based syntheses are emerging as a novel technique for the production of diverse forms of NPs, and is assured to meet the requirements. Therefore, in order to have a better understanding, and to improvise and gain control over the NPs morphological and surface characteristics, the present investigation systematically evaluates the influence of various major physico-cultural parameters including diverse growth media, concentrations of precursor salts; pH and temperature on the biotransformation of ionic silver (Ag+) to nanopariculate silver nanoparticles (AgNPs), utilizing the cell free extract of the bacterium, P. plecoglossicida. The synthesis, purity, morphology and surface characteristics of the AgNPs during optimization studies were measured. The bactericidal effect of these AgNPs was assessed using multi-drug resistant human pathogens; Acinetobacter baumannii, Escherichia coli, Pseudomonas aeruginosa and Salmonella enterica based on the diameter of inhibition zone in disk diffusion tests. The nanoparticles were found to be of higher toxicity to E. coli and S. enterica than A. baumannii and P. aeruginosa. The results demonstrate that the chosen parameters in whole or in part could have a significant influence on the morphology, surface characteristics, duration of production, overall yield and production of AgNPs.

The current investigation introduces the utilization of cell culture mediums as a novel source for the one-plot synthesis as well as stabilization of metal nanoparticles. By varying the medium constituents we could control the size and shape distributions of the gold nanoparticles. Nanospheres of diameter 24 ± 6 nm and 19 ± 5 nm were produced using DMEM and M199 mediums respectively, nanoneedles of 150 ± 50 nm using RPMI medium and nanoflowers of 60 ± 25 nm using IMDM medium, with an overall yield of 91 ± 2%. A remarkable decrease in the reaction duration (<3 min) was noted, irrespective of the growth mediums used. Fourier transform infrared spectroscopy and zeta potential measurements revealed them to have a common protenacious encapping agent with different overall surface charges of −23 ± 3, −21 ± 1, −24 ± 2, and −20 ± 1 mV for Au@DMEM, Au@RPMI, Au@IMDM and Au@M199 respectively. X-ray diffraction confirmed the purity and crystallinity of the particles with Bragg peaks at (111), (200), (220) and (311) for gold nanocrystals. This approach could lead to the creative utilization of novel eco-friendly sources for the production and size/shape control of nanoparticles. Moreover, the adopted methodology is absolutely green, robust and facile, offering new insights for sustainable synthesis for various biomedical and engineering applications.

Implementation of engineered nanoparticles as efficient catalysts for the degradation of hazardous dyes is being explored drastically. However, with predominant focus on correlating the catalytic activity with nanoparticle size and one particular shape (spheres), but other factors such as shape or morphology that can likely have a significant role in determining the catalytic reactivity remains elusive. In the present study we for the first time comparatively evaluate the influence of nearly uniform size-distributions of gold nanoparticles but with different crystallographic shapes; nano-cubes vs nano-rods vs nano-spheres, imparting overall diverse packing, density, electronic state, surface area and surface chemistry that can essentially determine the catalytic performances, on the catalysis of commonly used organic dyes; Methylene Blue and Safranin O as models. Our results highlighted that shape-influenced surface nano-chemistry had a drastic influence on the dye-degradation efficiencies. Relatively, at constant experimental parameters; nano-cubes possessing multi-flat-faceted surfaces were found to be highly efficient with instant degradation, followed by nano-rods with bilateral flat surface, that took up to 10 min for Methylene Blue and 16 min for Safranin O, whereas non-flat structured nano-spheres were least catalytic and took up to 90 min for Methylene Blue, and showed only partial degradation against Safranin O, even after several hours. Nanoparticles shape assessments, quantitative and qualitative analysis of the dye-degradation, along with kinetic parameters were evaluated based on visual confirmation, capturing images using a digital camera, and advanced physical characterization techniques including UV-Vis Spectroscopy, Fourier Transform Infrared Spectroscopy and Transmission Electron Microscopy measurements.

Metallic nanocomposites are gaining considerable attention and are widely being implemented in several biomedical and engineering applications due to their potent physicochemical properties. To ease wide application of nanoparticles, research is focused on novel and better synthesis strategies. This brief chapter details on the biofabrication of diverse forms of metallic nanoparticles using various bacterial systems, and the cellular impact, illustrated using suitable examples. Demonstration on the biosynthesis of silver nanoparticles using the cell-free extract of P. plecoglossicida is presented. This chapter will also describe the influence of various physicocultural parameters such as the growth medium, concentration of precursor salt; pH and temperature on the biotransformation, so as to attain desirable morphological and surface characteristics of nanoparticles. Overall, this chapter aims to discuss the recent progress in relation to bacterial-based biosynthesis so as to have a better understanding on their safe use for various biomedical and engineering applications.

Immunotherapy is currently being investigated for the treatment of many diseases, including cancer. The ability to control the location of immune cells during or following activation would represent a powerful new technique for this field. Targeted magnetic delivery is emerging as a technique for controlling cell movement and localization. Here we show that this technique can be extended to microglia, the primary phagocytic immune cells in the central nervous system. The magnetized microglia were generated by loading the cells with iron oxide nanoparticles functionalized with CpG oligonucleotides, serving as a proof of principle that nanoparticles can be used to both deliver an immunostimulatory cargo to cells and to control the movement of the cells. The nanoparticle-oligonucleotide conjugates are efficiently internalized, non-toxic, and immunostimulatory. We demonstrate that the in vitro migration of the adherent, loaded microglia can be controlled by an external magnetic field and that magnetically-induced migration is non-cytotoxic. In order to capture video of this magnetically-induced migration of loaded cells, a novel 3D-printed "cell box" was designed to facilitate our imaging application. Analysis of cell movement velocities clearly demonstrate increased cell velocities toward the magnet. These studies represent the initial step towards our final goal of using nanoparticles to both activate immune cells and to control their trafficking within the diseased brain.

Engineered nanoparticles have been gaining tremendous recognition in the pursuit of several biomedical applications, including drug and gene delivery, imaging, detection and targeted therapeutics. This chapter illustrates some important aspects of the use of metal nanoparticlepolymer nanoconstructs demonstrated for targeted cancer therapeutics, with an emphasis on the most commonly used and Food and Drug Administration (FDA) approved metallic nanoparticle (gold and iron oxide) based polymer constituents. Also provided is a brief overview of the various analytical and physical characterization techniques that are used to assess the interactions of nanoparticle-polymer constructs with cancer cells, with an emphasis on their biomedical applications.

Engineered nanoparticles of diverse forms are being profoundly used for various applications and demand ecologically benign synthesis processes. Conventional chemical methods employed for the syntheses of nanoparticles are environmentally unfriendly and energy intensive. Biologically inspired biofabrication approaches that utilize naturally existing microorganisms or plant extracts or biomaterials might overcome these issues. The present investigation for the first time shows the synthesis of small and monodispersed cadmium selenide nanoparticles utilizing the plant pathogenic fungus, Helminthosporum solani upon incubating with an aqueous solution of CdCl 2 and SeCl4 under ambient conditions. Multiple physical characterizations involving ultraviolet-visible and photoluminescence spectroscopy, transmission electron microscopy, selected area electron diffraction and X-ray photoelectron spectroscopy confirmed the production, purity, optical and surface characteristics, crystalline nature, size and shape distributions, and elemental composition of the nanoparticles. Pluralities of the particles are monodisperse spheres with a mean diameter of 5.5 ± 2 nm, are hydrophilic, highly stable with a broad photoluminescence and 1% quantum yield. This approach provides an alternative facile route for the biofabrication of quantum dot that is reliable, environmentally friendly, and lends itself directly for the creation of fluorescent biological labels. © 2014 Elsevier B.V. All rights reserved.

Metal and metal oxide nanoparticles are among the most commonly used nanomaterials and their potential for adversely affecting environmental systems raises concern. Complex microbial consortia underlie environmental processes, and the potential toxicity of nanoparticles to microbial systems, and the consequent impacts on trophic balances, is particularly worrisome. The diverse array of metal and metal oxides, the different sizes and shapes that can be prepared and the variety of possible surface coatings complicate assessments of toxicity. Further muddling biocidal interpretations are the diversity of microbes and their intrinsic tolerances to stresses. Here, we review a range of studies focused on nanoparticle-microbial interactions in an effort to correlate the physical-chemical properties of engineered metal and metal oxide nanoparticles to their biological response. General conclusions regarding the parent material of the nanoparticle and the nanoparticle's size and shape on potential toxicity can be made. However, the surface coating of the material, which can be altered significantly by environmental conditions, can ameliorate or promote microbial toxicity. Understanding nanoparticle transformations and how the nanoparticle surface can be designed to control toxicity represents a key area for further study. Additionally, the vast array of microbial species and the structuring of these species within communities complicate extrapolations of nanoparticle toxicity in real world settings. Ultimately, to interpret the effect and eventual fate of engineered materials in the environment, an understanding of the relationship between nanoparticle properties and responses at the molecular, cellular and community levels will be essential. © The Royal Society of Chemistry.

Naturally existing biological materials have been garning considerable attention as environmentally benign green-nanofactories for the fabrication of diverse nanomaterials, and with desired size and shape distributions. In the present investigation, we report the size and shape controllable biofabrication of silver nanocrystallites using the growth extract of the fungus, Rhizoctonia solani. Influence of various factors such as growth medium; radiation, in the form of sun light; and seeding duration on the production of silver nanoparticles using aqueous 1 mm silver nitrate solution under ambient conditions is presented. Our results demonstrate that these factors can significantly influence the production, size and shape transformation, and the rate of nanoparticles formation. Multiple characterization techniques involving UV-visible and Fourier transform infrared spectroscopy, X-ray diffraction, energy dispersive X-ray spectroscopy and transmission electron microscopy measurements confirmed the production, surface and structural characteristics, purity and crystalline nature of the biosynthesized silver nanoparticles. Our biogenic synthesis process provides a simple, ecologically friendly, cost-effective synthesis route, and most importantly the ability to have control over the size and shape distributions that lends itself for various biomedical and opto-electronic applications. Copyright © 2013 American Scientific Publishers All rights reserved.

Targeted delivery of therapeutic agents to tumor sites increases efficacy and limits off-target toxicity. Nanoparticles are an emerging class of targeted drug delivery systems. Commonly, nanoparticles are coated with poly(ethylene glycol) (PEG) to reduce off-target uptake by cells of the mononuclear phagocyte system (MPS) and a targeting moiety to promote uptake at the desired location. This approach holds great promise, but such constructs still predominantly accumulate in the liver. Here we demonstrate a different approach to tumor targeting using nanoparticles functionalized with a PEG coating that is shed in the presence of matrix metalloproteinase-2 (MMP-2), which is overexpressed in many tumor microenvironments. There was very little uptake of intact particles by human breast adenocarcinoma cells, whereas, when the same cells were treated with particles in the presence of MMP-2, the resulting denuded particles were rapidly taken up by the cells. This system is remarkably simple as the core nanoparticles revealed by PEG cleavage are not modified; uptake is driven simply by revealing the nanoparticle surface. The cleavable linker is a modular component that, in the future, can be designed to respond to other stimuli. This approach could lead to improved imaging and targeted drug delivery for solid tumors. © 2013 The Royal Society of Chemistry.

We report microbially facilitated synthesis of cadmium sulfide (CdS) nanostructured particles (NP) using anaerobic, metal-reducing Thermoanaerobacter sp. The extracellular CdS crystallites were <10 nm in size with yields of ~3 g/L of growth medium/month with demonstrated reproducibility and scalability up to 24 L. During synthesis, Thermoanaerobacter cultures reduced thiosulfate and sulfite salts to H2S, which reacted with Cd2+ cations to produce thermodynamically favored NP in a single step at 65 C with catalytic nucleation on the cell surfaces. Photoluminescence (PL) analysis of dry CdS NP revealed an exciton-dominated PL peak at 440 nm, having a narrow full width at half maximum of 10 nm. A PL spectrum of CdS NP produced by dissimilatory sulfur reducing bacteria was dominated by features associated with radiative exciton relaxation at the surface. High reproducibility of CdS NP PL features important for scale-up conditions was confirmed from test tubes to 24 L batches at a small fraction of the manufacturing cost associated with conventional inorganic NP production processes. © 2013 Society for Industrial Microbiology and Biotechnology (Outside the USA).

Due to their unique antimicrobial properties silver nanocrystallites have garnered substantial attention and are used extensively for biomedical applications as an additive to wound dressings, surgical instruments and bone substitute materials. They are also released into unintended locations such as the environment or biosphere. Therefore it is imperative to understand the potential interactions, fate and transport of nanoparticles with environmental biotic systems. Numerous factors including the composition, size, shape, surface charge, and capping molecule of nanoparticles are known to influence cell cytotoxicity. Our results demonstrate that the physical/chemical properties of the silver nanoparticles including surface charge, differential binding and aggregation potential, which are influenced by the surface coatings, are a major determining factor in eliciting cytotoxicity and in dictating potential cellular interactions. In the present investigation, silver nanocrystallites with nearly uniform size and shape distribution but with different surface coatings, imparting overall high negativity to high positivity, were synthesized. These nanoparticles included poly(diallyldimethylammonium) chloride-Ag, biogenic-Ag, colloidal-Ag (uncoated), and oleate-Ag with zeta potentials +45 ± 5, -12 ± 2, -42 ± 5, and -45 ± 5 mV, respectively; the particles were purified and thoroughly characterized so as to avoid false cytotoxicity interpretations. A systematic investigation on the cytotoxic effects, cellular response, and membrane damage caused by these four different silver nanoparticles was carried out using multiple toxicity measurements on mouse macrophage (RAW-264.7) and lung epithelial (C-10) cell lines. Our results clearly indicate that the cytotoxicity was dependent on various factors such as surface charge and coating materials used in the synthesis, particle aggregation, and the cell-type for the different silver nanoparticles that were investigated. Poly(diallyldimethylammonium)-coated Ag nanoparticles were found to be the most toxic, followed by biogenic-Ag and oleate-Ag nanoparticles, whereas uncoated or colloidal silver nanoparticles were found to be the least toxic to both macrophage and lung epithelial cells. Also, based on our cytotoxicity interpretations, lung epithelial cells were found to be more resistant to the silver nanoparticles than the macrophage cells, regardless of the surface coating. © 2012 American Chemical Society.

Shewanella oneidensis is a metal reducing bacterium, which is of interest for bioremediation and clean energy applications. S. oneidensis biofilms play a critical role in several situations such as in microbial energy harvesting devices. Here, we use a microfluidic device to quantify the effects of hydrodynamics on the biofilm morphology of S. oneidensis. For different rates of fluid flow through a complex microfluidic device, we studied the spatiotemporal dynamics of biofilms, and we quantified several morphological features such as spatial distribution, cluster formation and surface coverage. We found that hydrodynamics resulted in significant differences in biofilm dynamics. The baffles in the device created regions of low and high flow in the same device. At higher flow rates, a nonuniform biofilm develops, due to unequal advection in different regions of the microchannel. However, at lower flow rates, a more uniform biofilm evolved. This depicts competition between adhesion events, growth and fluid advection. Atomic force microscopy (AFM) revealed that higher production of extra-cellular polymeric substances (EPS) occurred at higher flow velocities. Copyright © 2012 by ASME.

Nanocrystallites have garnered substantial interest due to their various applications, including catalysis and medical research. Consequently important aspects of synthesis related to control of shape and size through economical and non-hazardous means are desirable. Highly efficient bioreduction-based fabrication approaches that utilize microbes and/or plant extracts are poised to meet these needs. Here we show that the γ-proteobacterium Shewanella oneidensis can reduce tetrachloroaurate (III) ions to produce discrete extracellular spherical gold nanocrystallites. The particles were homogeneously shaped with multiple size distributions and produced under ambient conditions at high yield, 88% theoretical maximum. Further characterization revealed that the particles consist of spheres in the size range of ∼2-50 nm, with an average size of 12 ± 5 nm. The nanoparticles were hydrophilic and resisted aggregation even after several months. Based on our experiments, the particles are likely fabricated by the aid of reducing agents present in the bacterial cell membrane and are capped by a detachable protein/peptide coat. Ultraviolet-visible and Fourier transform infrared spectroscopy, X-ray diffraction, energy dispersive X-ray spectra and transmission electron microscopy measurements confirmed the formation, surface characteristics and crystalline nature of the nanoparticles. The antibacterial activity of these gold nanoparticles was assessed using Gram-negative (Escherichia coli and S. oneidensis) and Gram-positive (Bacillus subtilis) bacterial species. Toxicity assessments showed that the particles were neither toxic nor inhibitory to any of these bacteria. © 2011 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Interest in engineered metal and semiconductor nanocrystallites continues to grow due to their unique size- and shape-dependent optoelectronic, physicochemical and biological properties. Therefore identifying novel non-hazardous nanoparticle synthesis routes that address hydrophilicity, size and shape control and production costs has become a priority. In the present article we report for the first time on the efficient generation of extracellular silver sulfide (Ag2S) nanoparticles by the metal-reducing bacterium Shewanella oneidensis. The particles are reasonably monodispersed and homogeneously shaped. They are produced under ambient temperatures and pressures at high yield, 85% theoretical maximum. UV-visible and Fourier transform infrared spectroscopy, dynamic light scattering, X-ray diffraction, transmission electron microscopy and X-ray photoelectron spectroscopy measurements confirmed the formation, optical and surface properties, purity and crystallinity of the synthesized particles. Further characterization revealed that the particles consist of spheres with a mean diameter of 9 ± 3.5 nm, and are capped by a detachable protein/peptide surface coat. Toxicity assessments of these biogenic Ag2S nanoparticles on Gram-negative (Escherichia coli and S. oneidensis) and Gram-positive (Bacillus subtilis) bacterial systems, as well as eukaryotic cell lines including mouse lung epithelial (C 10) and macrophage (RAW-264.7) cells, showed that the particles were non-inhibitory and non-cytotoxic to any of these systems. Our results provide a facile, eco-friendly and economical route for the fabrication of technologically important semiconducting Ag2S nanoparticles. These particles are dispersible and biocompatible, thus providing excellent potential for use in optical imaging, electronic devices and solar cell applications. © 2011 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Microorganisms have long been known to develop resistance to metal ions either by sequestering metals inside the cell or by effluxing them into the extracellular media. Here we report the biosynthesis of extracellular silver-based single nanocrystallites of well-defined composition and homogeneous morphology utilizing the γ-proteobacterium, Shewanella oneidensis MR-1, upon incubation with aqueous silver nitrate solution. Further characterization of these particles revealed that the crystals consist of small, reasonably monodispersed spheres in the 2-11 nm size range (average of 4 ± 1.5 nm). The bactericidal effect of these nanoparticles (biogenic-Ag) is compared to chemically synthesized silver nanoparticles (colloidal-Ag and oleate capped silver nanoparticles, oleate-Ag) and assessed using Gram-negative (E. coli and S. oneidensis) and Gram-positive (B. subtilis) bacteria. Relative toxicity was based on the diameter of inhibition zone in disk diffusion tests, minimum inhibitory concentrations, live/dead assays, and atomic force microscopy. From a toxicity perspective, strain-dependent inhibition depended on the synthesis procedure and the surface coat. Biogenic-Ag was found to be of higher toxicity compared to colloidal-Ag for all three strains tested, whereas E. coli and S. oneidensis were found to be more resistant to either of these nanoparticles than B. subtilis. In contrast, oleate-Ag was not toxic to any of the bacteria. These findings have implications for the potential uses of Ag nanomaterials and for their fate in biological and environmental systems. © 2010 American Chemical Society.

Interest in engineered nanostructures has risen in recent years due to their use in energy conservation strategies and biomedicine. To ensure prudent development and use of nanomaterials, the fate and effects of such engineered structures on the environment should be understood. Interactions of nanomaterials with environmental microorganisms are inevitable, but the general consequences of such interactions remain unclear, due to a lack of standard methods for assessing such interactions. Therefore, we have initiated a multianalytical approach to understand the interactions of synthesized nanoparticles with bacterial systems. These efforts are focused initially on cerium oxide nanoparticles and model bacteria in order to evaluate characterization procedures and the possible fate of such materials in the environment. The growth and viability of the Gram-negative species Escherichia coli and Shewanella oneidensis, a metal-reducing bacterium, and the Gram-positive species Bacillus subtilis were examined relative to cerium oxide particle size, growth media, pH, and dosage. A hydrothermal synthesis approach was used to prepare cerium oxide nanoparticles of defined sizes in order to eliminate complications originating from the use of organic solvents and surfactants. Bactericidal effects were determined from MIC and CFU measurements, disk diffusion tests, and live/dead assays. For E. coli and B. subtilis, clear strain- and size-dependent inhibition was observed, whereas S. oneidensis appeared to be unaffected by the particles. Transmission electron microscopy along with microarray- based transcriptional profiling was used to understand the response mechanism of the bacteria. Use of multiple analytical approaches adds confidence to toxicity assessments, while the use of different bacterial systems highlights the potential wide-ranging effects of nanomaterial interactions in the environment.

In this work, we demonstrate the application of quantum dots (QDs) to several biologically relevant applications. QDs are synthesized by biological and organometallic routes and the relative merits of these methods are identified. Our results indicate that QDs can be functionalized and specifically targeted to both mammalian and bacterial cells. In the case of mammalian cells, they can be targeted to an engineered sodium channel for the purpose of sensing. In both mammalian and bacterial cells, the interaction with bioconjugated QDs can lead to phototoxicity due to the generation of reactive oxygen species (ROS).