Ion mediated monolayer deposition of gold nanoparticles on microorganisms: discrimination by age

In situ silver nanoparticle coating of virions for quantification at single virus level

In situ labelling and encapsulation of biological entities, such as of single viruses, may provide a versatile approach to modulate their functionality and facilitate their detection at single particle level. Here, we introduce a novel virus metallization approach based on in situ coating of viruses in solution with silver nanoparticles (AgNP) in a two-step synthetic process, i.e. surface activation with a tannic acid - Sn(II) coordination complex, which subsequently induces silver ion (I) reduction. The metalic coating on the virus surface opens the opportunity for electrochemical quantification of the AgNP-tagged viruses by nano-impact electrochemistry on a microelectrode with single particle sensitivity, i.e. enable the detection of particles oherwise undetectable. We show that the silver coating of the virus particles impacting the electrode can be oxidized to produce distinct current peaks the frequency of which show a linear correlation with the virus count. The proof of the concept was done with inactivated Influenza A (H3N2) viruses resulting in their quantitation down to the femtomolar concentrations (ca. 5 × 10⁷ particles per mL) using 50 s counting sequences.

Influences of petroleum hydrocarbon pyrene on the formation, stability and antibacterial activity of natural Au nanoparticles

The effect of pyrene on the formation of naturally Au nanoparticles (AuNPs) in the presence of humic acid (HA) under UV irradiation is described. TEM, EDS, FTIR and XPS were carried out to prove the formation of AuNPs and display their morphologies and formation mechanism. There are little differences between size, morphology and function groups of surface coated materials of AuNPs formed with and without pyrene. With the presence of HA, pyrene showed an inhibiting effect on the reduction of Au ion via competition for O₂^•-, thereby decreasing the production of AuNPs. However, AuNPs formed by HA-pyrene showed higher stability than AuNPs formed by HA with the sedimentation rates of 4.13% and 13.68% respectively after 30-d standing. As for the antibacterial activities against Staphylococcus aureus and Escherichia coli, AuNPs formed by HA-pyrene were more toxic than AuNPs formed by HA. Meanwhile, changes of environmental factors such as temperature, pH and ionic strength exhibited similar influence trend on the formation of AuNPs in the presence and absence of pyrene. The results suggest that the typical petroleum hydrocarbon pyrene contained in spilled oil could influence the formation, fate and ecotoxicity of AuNPs.

Novel nanomaterial-organism hybrids with biomedical potential

Instinctive hierarchically biomineralized structures of various organisms, such as eggs, algae, and magnetotactic bacteria, afford extra protection and distinct performance, which endow fragile organisms with a tenacious ability to adapt and survive. However, spontaneous formation of hybrid materials is difficult for most organisms in nature. Rapid development of chemistry and materials science successfully obtained the combinations of organisms with nanomaterials by biomimetic mineralization thus demonstrating the reproduction of the structures and functions and generation of novel functions that organisms do not possess. The rational design of biomaterial-organism hybridization can control biological recognition, interactions, and metabolism of the organisms. Thus, nanomaterial-organism hybrids represent a next generation of organism engineering with great potential biomedical applications. This review summarizes recent advances in material-directed organism engineering and is mainly focused on biomimetic mineralization technologies and their outstanding biomedical applications. Three representative types of biomimetic mineralization are systematically introduced, including external mineralization, internal mineralization, and genetic engineering mineralization. The methods involving hybridization of nanomaterials and organisms based on biomimetic mineralization strategies are described. These strategies resulted in applications of various nanomaterial-organism hybrids with multiplex functions in cell engineering, cancer treatment, and vaccine improvement. Unlike classical biological approaches, this material-based bioregulation is universal, effective, and inexpensive. In particular, instead of traditional medical solutions, the integration of nanomaterials and organisms may exploit novel strategies to solve current biomedical problems. This article is categorized under: Implantable Materials and Surgical Technologies > Nanomaterials and Implants Therapeutic Approaches and Drug Discovery > Nanomedicine for Oncologic Disease Therapeutic Approaches and Drug Discovery > Nanomedicine for Infectious Disease.

Halloysite nanotubes - the nano-bio interface

The numerous biological applications of nanoparticles in general and nano-clays in particular are rooted in understanding and harnessing their dynamic nano-bio interface. Among clays, the intrinsically-mesoporous halloysite nanotubes (HNTs) have emerged in recent years as promising nanomaterials. The diverse interactions of these nanotubes with living cells, encompassing electrostatic, van der Waals, and ion exchange, along with cellular response, are crucial in determining the behaviour of HNTs in biological systems. Thus, rational engineering of the nanotube properties allows for vast applications ranging from bacteria encapsulation for bioremediation, through algae flocculation for aquaculture, to intracellular drug delivery. This review summarizes the many aspects of the nano-bio interface of HNTs with different cell types (bacteria, algae and fungi, and mammalian cells), highlighting biocompatibility/bio-adverse properties, interaction mechanisms, and the latest cutting-edge technologies.

Nanobiohybrids: Materials approaches for bioaugmentation

Nanobiohybrids, synthesized by integrating functional nanomaterials with living systems, have emerged as an exciting branch of research at the interface of materials engineering and biological science. Nanobiohybrids use synthetic nanomaterials to impart organisms with emergent properties outside their scope of evolution. Consequently, they endow new or augmented properties that are either innate or exogenous, such as enhanced tolerance against stress, programmed metabolism and proliferation, artificial photosynthesis, or conductivity. Advances in new materials design and processing technologies made it possible to tailor the physicochemical properties of the nanomaterials coupled with the biological systems. To date, many different types of nanomaterials have been integrated with various biological systems from simple biomolecules to complex multicellular organisms. Here, we provide a critical overview of recent developments of nanobiohybrids that enable new or augmented biological functions that show promise in high-tech applications across many disciplines, including energy harvesting, biocatalysis, biosensing, medicine, and robotics.

Ca2+-Mediated Surface Polydopamine Engineering to Program Dendritic Cell Maturation

Engineering of cell surfaces holds promise in manipulating cellular activities in a physicochemical route as a complement to the biological approach. Mediated by Ca²⁺, a quick and convenient yet cytocompatible method is used to achieve surface engineering, by which polydopamine nanostructures can be in situ grown onto dendritic cell (DC) surfaces within 10 min. Ca²⁺, as the physical bridge between the negative cell surface and polydopamine, avoids the direct chemical polymerization of polydopamine onto the cell surface, critically important to maintain the cell viability. As a proof of concept in potential applications, this cell surface engineering shows a good control toward DC maturation. Upon surface polydopamine engineering, bone-marrow-derived DC exhibits a unique bidirectional control of maturation. The polydopamine structure enables effective suppression of DC activation by acting as an efficient scavenger of reactive oxygen species, a key signal during maturation. Conversely, an 808 nm laser irradiation can remotely relieve the suppressed state and effectively activate DC maturation by the photoheat effect of polydopamine (39 °C). The work provides an easily implemented, straightforward approach to achieve cell surface engineering, through which the DC maturation can be controlled.

Nanoarchitectonics meets cell surface engineering: shape recognition of human cells by halloysite-doped silica cell imprints

Cell surface engineering, as a practical manifestation of nanoarchitectonics, is a powerful tool to modify and enhance properties of live cells. In turn, cells may serve as sacrificial templates to fabricate cell-mimicking materials. Herein we report a facile method to produce cell-recognising silica imprints capable of the selective detection of human cells. We used HeLa cells to template silica inorganic shells doped with halloysite clay nanotubes. The shells were destroyed by sonication resulting in the formation of polydisperse hybrid imprints that were used to recognise HeLa cells in liquid media supplemented with yeast. We believe that methodology reported here will find applications in biomedical and clinical research.

Strategic Advances in Formation of Cell-in-Shell Structures: From Syntheses to Applications

Single-cell nanoencapsulation, forming cell-in-shell structures, provides chemical tools for endowing living cells, in a programmed fashion, with exogenous properties that are neither innate nor naturally achievable, such as cascade organic-catalysis, UV filtration, immunogenic shielding, and enhanced tolerance in vitro against lethal factors in real-life settings. Recent advances in the field make it possible to further fine-tune the physicochemical properties of the artificial shells encasing individual living cells, including on-demand degradability and reconfigurability. Many different materials, other than polyelectrolytes, have been utilized as a cell-coating material with proper choice of synthetic strategies to broaden the potential applications of cell-in-shell structures to whole-cell catalysis and sensors, cell therapy, tissue engineering, probiotics packaging, and others. In addition to the conventional "one-time-only" chemical formation of cytoprotective, durable shells, an approach of autonomous, dynamic shellation has also recently been attempted to mimic the naturally occurring sporulation process and to make the artificial shell actively responsive and dynamic. Here, the recent development of synthetic strategies for formation of cell-in-shell structures along with the advanced shell properties acquired is reviewed. Demonstrated applications, such as whole-cell biocatalysis and cell therapy, are discussed, followed by perspectives on the field of single-cell nanoencapsulation.

"Self-repairing" nanoshell for cell protection

Self-repair is nature's way of protecting living organisms. However, most single cells are inherently less capable of self-repairing, which greatly limits their wide applications. Here, we present a self-assembly approach to create a nanoshell around the cell surface using nanoporous biohybrid aggregates. The biohybrid shells present self-repairing behaviour, resulting in high activity and extended viability of the encapsulated cells (eukaryotic and prokaryotic cells) in harsh micro-environments, such as under UV radiation, natural toxin invasion, high-light radiation and abrupt pH-value changes. Furthermore, an interaction mechanism is proposed and studied, which is successful to guide design and synthesis of self-repairing biohybrid shells using different bioactive molecules.

Electrochemical synthesis on nanoparticle chains to couple semiconducting rods: coulomb blockade modulation using photoexcitation

Hybrid nanostructures are made by coupling a room temperature coulomb blockade device with photoexcitable nano-rods. Direct electrochemical synthesis on nanoparticle chain arrays leads to the formation of semiconducting rods that are in direct contact with the nanoparticles and also spatial confined by them. This direct interfacing leads to mutual intermodulation between the two systems.

Nanocoating of single cells: from maintenance of cell viability to manipulation of cellular activities

The chronological progresses in single-cell nanocoating are described. The historical developments in the field are divided into biotemplating, cytocompatible nanocoating, and cells in nano-nutshells, depending on the main research focuses. Each subfield is discussed in conjunction with the others, regarding how and why to manipulate living cells by nanocoating at the single-cell level.

Size- and age-dependent neurotoxicity of engineered metal nanoparticles in rats

Earlier we showed that chronic administration of engineered nanoparticles (NPs) from metals, e.g., Cu, Ag, or Al (50-60 nm, 50 mg/kg, i.p. daily for 1 week) alter blood-brain barrier (BBB) disruption and induce brain pathology in adult rats (age 18 to 22 weeks). However, effects of size-dependent neurotoxicity of NPs in vivo are still largely unknown. In present investigation, we examined the effects of different size ranges of the above-engineered NPs on brain pathology in rats. Furthermore, the fact that age is also an important factor in brain pathology was also investigated in our rat model. Our results showed that small-sized NPs induced the most pronounced BBB breakdown (EBA +480 to 680 %; radioiodine +850 to 1025 %), brain edema formation (+4 to 6 %) and neuronal injuries (+30 to 40 %), glial fibrillary acidic protein upregulation (+40 to 56 % increase), and myelin vesiculation (+30 to 35 % damage) in young animals as compared to controls. Interestingly, the oldest animals (30 to 35 weeks of age) also showed massive brain pathology as compared to young adults (18 to 20 weeks old). The Ag and Cu exhibited greater brain damage compared with Al NPs in all age groups regardless of their size. This suggests that apart from the size, the composition of NPs is also important in neurotoxicity. The very young and elderly age groups exhibited greater neurotoxicity to NPs suggests that children and elderly are more vulnerable to NPs-induced brain damage. The NPs-induced brain damage correlated well with the upregulation of neuronal nitric oxide synthase activity in the brain indicating that NPs-induced neurotoxicity may be mediated via increased production of nitric oxide, not reported earlier.

Identification of gold nanoparticle-resistant mutants of Saccharomyces cerevisiae suggests a role for respiratory metabolism in mediating toxicity

Positively charged gold nanoparticles (0.8-nm core diameter) reduced yeast survival, but not growth, at a concentration of 10 to 100 μg/ml. Among 17 resistant deletion mutants isolated in a genome-wide screen, highly significant enrichment was observed for respiration-deficient mutants lacking genes encoding proteins associated with the mitochondrion.

Graphene as membrane for encapsulation of yeast cells: protective and electrically conducting

Graphene sheets (chemically reduced), a high modulus and high thermal and electrically conductive material are coupled with yeast cells to form an encapsulating inorganic functional layer. The coupling of the high modulus sheets with the cells increases their stability to osmotic stresses. The sheets also allow the direct visualization of the cells in an electron microscope.

Graphene as cellular interface: electromechanical coupling with cells

Interfacing cells with nanomaterials such as graphene, nanowires, and carbon nanotubes is useful for the integration of cellular physiology with electrical read outs. Here we show the interfacing of graphene sheets on the surface of yeast cells, leading to electromechanical coupling between the sheets and the cells. The cells are viable after the interfacing. The response caused by physiologically stressing the cells by exposure to alcohols, which causes a change in cell volume, can be observed in the electrical signal through graphene. The change in the cell volume leads to straining of the sheets, forming wrinkles which reduce the electrical conductivity. As the dynamic response of the cell can be observed, it is possible to differentiate between ethanol, 2-propanol, and water. We believe this will lead to further development of cell-based electrical devices and sensors.

Bionanotechnology: small can have a big impact in the medical sciences: a WIN-win situation. Part 2

Bionanotechnology blends the areas of nanotechnology and biological sciences. This article surveys the area of nanoscale biosensor development and the application of state-of-the-art biophysical techniques to elucidate fundamental membrane and surfactant biochemistry undertaken at the University of Waterloo (Canada). The Waterloo Institute for Nanotechnology (WIN), coordinates various cutting-edge nanotechnology research areas at the University of Waterloo. One focus is the area of biosensor research and fundamental biophysics in bionanotechnology. This is Part 2 of a contribution from the WIN initiative.

Interfacing living unicellular algae cells with biocompatible polyelectrolyte-stabilised magnetic nanoparticles

Green algae are a promising platform for the development of biosensors and bioelectronic devices. Here we report a reliable single-step technique for the functionalisation of living unicellular green algae Chlorella pyrenoidosa with biocompatible 15 nm superparamagnetic nanoparticles stabilised with poly(allylamine hydrochloride). The magnetised algae cells can be manipulated and immobilised using external permanent magnets. The distribution of the nanoparticles on the cell walls of C. pyrenoidosa was studied by optical and fluorescence microscopy, TEM, SEM and EDX spectroscopy. The viability and the magnetic properties of the magnetised algae are studied in comparison with the native cells. The technique may find a number of potential applications in biotechnology and bioelectronics.

Gold nanoparticles delivery in mammalian live cells: a critical review

Functional nanomaterials have recently attracted strong interest from the biology community, not only as potential drug delivery vehicles or diagnostic tools, but also as optical nanomaterials. This is illustrated by the explosion of publications in the field with more than 2,000 publications in the last 2 years (4,000 papers since 2000; from ISI Web of Knowledge, 'nanoparticle and cell' hit). Such a publication boom in this novel interdisciplinary field has resulted in papers of unequal standard, partly because it is challenging to assemble the required expertise in chemistry, physics, and biology in a single team. As an extreme example, several papers published in physical chemistry journals claim intracellular delivery of nanoparticles, but show pictures of cells that are, to the expert biologist, evidently dead (and therefore permeable). To attain proper cellular applications using nanomaterials, it is critical not only to achieve efficient delivery in healthy cells, but also to control the intracellular availability and the fate of the nanomaterial. This is still an open challenge that will only be met by innovative delivery methods combined with rigorous and quantitative characterization of the uptake and the fate of the nanoparticles. This review mainly focuses on gold nanoparticles and discusses the various approaches to nanoparticle delivery, including surface chemical modifications and several methods used to facilitate cellular uptake and endosomal escape. We will also review the main detection methods and how their optimum use can inform about intracellular localization, efficiency of delivery, and integrity of the surface capping.