Getting Hold of the Tobamovirus Particle-Why and How? Purification Routes over Time and a New Customizable Approach

This article develops a multi-perspective view on motivations and methods for tobamovirus purification through the ages and presents a novel, efficient, easy-to-use approach that can be well-adapted to different species of native and functionalized virions. We survey the various driving forces prompting researchers to enrich tobamoviruses, from the search for the causative agents of mosaic diseases in plants to their increasing recognition as versatile nanocarriers in biomedical and engineering applications. The best practices and rarely applied options for the serial processing steps required for successful isolation of tobamoviruses are then reviewed. Adaptations for distinct particle species, pitfalls, and 'forgotten' or underrepresented technologies are considered as well. The article is topped off with our own development of a method for virion preparation, rooted in historical protocols. It combines selective re-solubilization of polyethylene glycol (PEG) virion raw precipitates with density step gradient centrifugation in biocompatible iodixanol formulations, yielding ready-to-use particle suspensions. This newly established protocol and some considerations for perhaps worthwhile further developments could serve as putative stepping stones towards preparation procedures appropriate for routine practical uses of these multivalent soft-matter nanorods.

Sensor development for multiple simultaneous classifications using genetically engineered M13 bacteriophages

Sensors for detecting infinitesimal amounts of chemicals in air have been widely developed because they can identify the origin of chemicals. These sensing technologies are also used to determine the variety and freshness of fresh food and detect explosives, hazardous chemicals, environmental hormones, and diseases using exhaled gases. However, there is still a need to rapidly develop portable and highly sensitive sensors that respond to complex environments. Here, we show an efficient method for optimising an M13 bacteriophage-based multi-array colourimetric sensor for multiple simultaneous classifications. Apples, which are difficult to classify due to many varieties in distribution, were selected for classifying targets. M13 was adopted to fabricate a multi-array colourimetric sensor using the self-templating process since a chemical property of major coat protein p8 consisting of the M13 body can be manipulated by genetic engineering to respond to various target substances. The twenty sensor units, which consisted of different types of manipulated M13, exhibited colour changes because of the change of photonic crystal-like nanostructure when they were exposed to target substances associated with apples. The classification success rate of the optimal sensor combinations was achieved with high accuracy for the apple variety (100%), four standard fragrances (100%), and aging (84.5%) simultaneously. We expect that this optimisation technique can be used for rapid sensor development capable of multiple simultaneous classifications in various fields, such as medical diagnosis, hazardous environment monitoring, and the food industry, where sensors need to be developed in response to complex environments consisting of various targets.

The development progress of multi-array colourimetric sensors based on the M13 bacteriophage

Techniques for detecting chemicals dispersed at low concentrations in air continue to evolve. These techniques can be applied not only to manage the quality of agricultural products using a post-ripening process but also to establish a safety prevention system by detecting harmful gases and diagnosing diseases. Recently, techniques for rapid response to various chemicals and detection in complex and noisy environments have been developed using M13 bacteriophage-based sensors. In this review, M13 bacteriophage-based multi-array colourimetric sensors for the development of an electronic nose is discussed. The self-templating process was adapted to fabricate a colour band structure consisting of an M13 bacteriophage. To detect diverse target chemicals, the colour band was utilised with wild and genetically engineered M13 bacteriophages to enhance their sensing abilities. Multi-array colourimetric sensors were optimised for application in complex and noisy environments based on simulation and deep learning analysis. The development of a multi-array colourimetric sensor platform based on the M13 bacteriophage is likely to result in significant advances in the detection of various harmful gases and the diagnosis of various diseases based on exhaled gas in the future.

In vitro biological activities of the flexible and virus nanoparticle-decorated silk fibroin-based films

Flexible films were prepared from silk fibroin (SF) and gelatin (GA) with a presence of glycerol (Gly), followed by water vapor annealing to achieve water-insoluble matrices. The blended SF/GA/Gly films were chemically conjugated with tobacco mosaic virus (TMV), either native (TMV-wt) or genetically modified with Arg-Gly-Asp (RGD) sequences (TMV-rgd), to improve cellular responses. The attachment and proliferation of L929 cells on TMV-decorated films were improved, possibly due to enhanced surface roughness. The cellular responses were pronounced with TMV-rgd, due to the proper decoration of RGD, which is an integrin recognition motif supporting cell binding. However, the biological results were inconclusive for human primary cells because of an innate slow growth kinetic of the cells. Additionally, the cells on SF/GA/Gly films were greater populated in S and G2/M phase, and the cell cycle arrest was notably increased in the TMV-conjugated group. Our findings revealed that the films modified with TMV were cytocompatible and the cellular responses were significantly enhanced when conjugated with its RGD mutants. The biological analysis on the cellular mechanisms in response to TMV is further required to ensure the safety concern of the biomaterials toward clinical translation.

Anticoagulant Hydrogel Tubes with Poly(ɛ-Caprolactone) Sheaths for Small-Diameter Vascular Grafts

Small-diameter vascular grafts (inner diameter < 6 mm) are useful in treating cardiovascular diseases. The off-the-shelf small-diameter vascular grafts for clinical applications remain a great limitation owing to their thrombogenicity or intimal hyperplasia. Herein, bilayer anticoagulant hydrogel tubes with poly(ε-caprolactone) (PCL) sheaths are prepared by freeze-thawing and electrospinning, which contain nanofibrillated cellulose (NFC)/poly(vinyl alcohol) (PVA)-heparin/poly-L-lysine nanoparticles tube as an inner layer and PCL sheath as an outer layer. The structure, anticoagulant property, and biocompatibility of the inner layer are studied. The effects of thickness of the outer layer on perfusion performance and mechanical property of hydrogel tubes with PCL sheaths (PCL-NFC/PVA-NPs tubes) are investigated. The effect of compliance of PCL-NFC/PVA-NPs tubes on their blood flow is studied by numerical simulation. The tissue compatibility and the patency of PCL-NFC/PVA-NPs tubes are evaluated by implantation in subcutaneous tissue of rats and carotid artery of rabbits. PCL-NFC/PVA-NPs tubes have prominent anticoagulation, sufficient burst pressure and good compliance similar to native arteries. PCL-NFC/PVA-NPs tubes facilitate infiltration of host cells and achieve active proliferation of recruited cells, which will be a promising candidate for small-diameter vascular grafts.

Application of Plant Viruses in Biotechnology, Medicine, and Human Health

Plant-based nanotechnology programs using virus-like particles (VLPs) and virus nanoparticles (VNPs) are emerging platforms that are increasingly used for a variety of applications in biotechnology and medicine. Tobacco mosaic virus (TMV) and potato virus X (PVX), by virtue of having high aspect ratios, make ideal platforms for drug delivery. TMV and PVX both possess rod-shaped structures and single-stranded RNA genomes encapsidated by their respective capsid proteins and have shown great promise as drug delivery systems. Cowpea mosaic virus (CPMV) has an icosahedral structure, and thus brings unique benefits as a nanoparticle. The uses of these three plant viruses as either nanostructures or expression vectors for high value pharmaceutical proteins such as vaccines and antibodies are discussed extensively in the following review. In addition, the potential uses of geminiviruses in medical biotechnology are explored. The uses of these expression vectors in plant biotechnology applications are also discussed. Finally, in this review, we project future prospects for plant viruses in the fields of medicine, human health, prophylaxis, and therapy of human diseases.

Application of Advanced Nanomaterials for Kidney Failure Treatment and Regeneration

The implementation of nanomedicine not only provides enhanced drug solubility and reduced off-target adverse effects, but also offers novel theranostic approaches in clinical practice. The increasing number of studies on the application of nanomaterials in kidney therapies has provided hope in a more efficient strategy for the treatment of renal diseases. The combination of biotechnology, material science and nanotechnology has rapidly gained momentum in the realm of therapeutic medicine. The establishment of the bedrock of this emerging field has been initiated and an exponential progress is observed which might significantly improve the quality of human life. In this context, several approaches based on nanomaterials have been applied in the treatment and regeneration of renal tissue. The presented review article in detail describes novel strategies for renal failure treatment with the use of various nanomaterials (including carbon nanotubes, nanofibrous membranes), mesenchymal stem cells-derived nanovesicles, and nanomaterial-based adsorbents and membranes that are used in wearable blood purification systems and synthetic kidneys.

From infection to healing: The use of plant viruses in bioactive hydrogels

Plant viruses show great diversity in shape and size, but each species forms unique nucleoprotein particles that are symmetrical and monodisperse. The genetically programed structure of plant viruses allows them to be modified by genetic engineering, bioconjugation, or encapsulation to form virus nanoparticles (VNPs) that are suitable for a broad range of applications. Plant VNPs can be used to present foreign proteins or epitopes, to construct inorganic hybrid materials, or to carry molecular cargos, allowing their utilization as imaging reagents, immunomodulators, therapeutics, nanoreactors, and biosensors. The medical applications of plant viruses benefit from their inability to infect and replicate in human cells. The structural properties of plant viruses also make them useful as components of hydrogels for tissue engineering. Hydrogels are three-dimensional networks composed of hydrophilic polymers that can absorb large amounts of water. They are used as supports for tissue regeneration, as reservoirs for controlled drug release, and are found in contact lenses, many wound healing materials, and hygiene products. They are also useful in ecological applications such as wastewater treatment. Hydrogel-based matrices are structurally similar to the native extracellular matrix (ECM) and provide a scaffold for the attachment of cells. To fully replicate the functions of the ECM it is necessary to augment hydrogels with biological cues that regulate cellular interactions. This can be achieved by incorporating functionalized VNPs displaying ligands that influence the mechanical characteristics of hydrogels and their biological properties, promoting the survival, proliferation, migration, and differentiation of embedded cells. This article is categorized under: Implantable Materials and Surgical Technologies > Nanomaterials and Implants Biology-Inspired Nanomaterials > Protein and Virus-Based Structures Implantable Materials and Surgical Technologies > Nanotechnology in Tissue Repair and Replacement.

Bacteriophage nanofiber fabrication using near field electrospinning

M13 bacteriophage (phage) nano- and microfibers were fabricated using electrospinning. Using liquid crystalline suspension of the phage, we successfully fabricated nano- and microscale pure phage fibers. Through a near field electrospinning process, we fabricated the desired phage fiber pattern with tunable direction and spacing. In addition, we demonstrated that the resulting phage fibers could be utilized as an electrostatic-stimulus responsive actuator. The near field electrospinning would be a very useful tool to design phage-based chemical sensors, tissue regenerative materials, energy generators, metallic and semiconductor nanowires in the future.

From stars to stripes: RNA-directed shaping of plant viral protein templates-structural synthetic virology for smart biohybrid nanostructures

The self-assembly of viral building blocks bears exciting prospects for fabricating new types of bionanoparticles with multivalent protein shells. These enable a spatially controlled immobilization of functionalities at highest surface densities-an increasing demand worldwide for applications from vaccination to tissue engineering, biocatalysis, and sensing. Certain plant viruses hold particular promise because they are sustainably available, biodegradable, nonpathogenic for mammals, and amenable to in vitro self-organization of virus-like particles. This offers great opportunities for their redesign into novel "green" carrier systems by spatial and structural synthetic biology approaches, as worked out here for the robust nanotubular tobacco mosaic virus (TMV) as prime example. Natural TMV of 300 x 18 nm is built from more than 2,100 identical coat proteins (CPs) helically arranged around a 6,395 nucleotides ssRNA. In vitro, TMV-like particles (TLPs) may self-assemble also from modified CPs and RNAs if the latter contain an Origin of Assembly structure, which initiates a bidirectional encapsidation. By way of tailored RNA, the process can be reprogrammed to yield uncommon shapes such as branched nanoobjects. The nonsymmetric mechanism also proceeds on 3'-terminally immobilized RNA and can integrate distinct CP types in blends or serially. Other emerging plant virus-deduced systems include the usually isometric cowpea chlorotic mottle virus (CCMV) with further strikingly altered structures up to "cherrybombs" with protruding nucleic acids. Cartoon strips and pictorial descriptions of major RNA-based strategies induct the reader into a rare field of nanoconstruction that can give rise to utile soft-matter architectures for complex tasks. This article is categorized under: Biology-Inspired Nanomaterials > Protein and Virus-Based Structures Nanotechnology Approaches to Biology > Nanoscale Systems in Biology Biology-Inspired Nanomaterials > Nucleic Acid-Based Structures.

Plant virus-based materials for biomedical applications: Trends and prospects

Nanomaterials composed of plant viral components are finding their way into medical technology and health care, as they offer singular properties. Precisely shaped, tailored virus nanoparticles (VNPs) with multivalent protein surfaces are efficiently loaded with functional compounds such as contrast agents and drugs, and serve as carrier templates and targeting vehicles displaying e.g. peptides and synthetic molecules. Multiple modifications enable uses including vaccination, biosensing, tissue engineering, intravital delivery and theranostics. Novel concepts exploit self-organization capacities of viral building blocks into hierarchical 2D and 3D structures, and their conversion into biocompatible, biodegradable units. High yields of VNPs and proteins can be harvested from plants after a few days so that various products have reached or are close to commercialization. The article delineates potentials and limitations of biomedical plant VNP uses, integrating perspectives of chemistry, biomaterials sciences, molecular plant virology and process engineering.

TMV Particles: The Journey From Fundamental Studies to Bionanotechnology Applications

Ever since its initial characterization in the 19th century, tobacco mosaic virus (TMV) has played a prominent role in the development of modern virology and molecular biology. In particular, research on the three-dimensional structure of the virus particles and the mechanism by which these assemble from their constituent protein and RNA components has made TMV a paradigm for our current view of the morphogenesis of self-assembling structures, including viral particles. More recently, this knowledge has been applied to the development of novel reagents and structures for applications in biomedicine and bionanotechnology. In this article, we review how fundamental science has led to TMV being at the vanguard of these new technologies.

Dual Functionalization of Rod-Shaped Viruses on Single Coat Protein Subunits

Plant viruses are emerging as versatile tools for nanotechnology applications since it is possible to modify their multivalent protein surfaces and thereby introduce and display new functionalities. In this chapter, we describe a tobacco mosaic virus (TMV) variant that exposes two selectively addressable amino acid moieties on each of its 2130 coat protein (CP) subunits. A lysine as well as a cysteine introduced at accessible sites of every CP can be modified with amino- and/or thiol-reactive chemistry such as N-hydroxysuccinimide esters (NHS ester) and maleimide containing reagents alone or simultaneously. This enables the pairwise immobilization of distinct molecules in close vicinity to each other on the TMV surface by simple standard conjugation protocols. We describe the generation of the mutations, the virus propagation and isolation as well as the dual functionalization of the TMV variant with two fluorescent dyes. The labeling is evaluated by SDS-PAGE and spectrophotometry and the degree of labeling (DOL) calculated.

A New Label-Free Technique for Analysing Evaporation Induced Self-Assembly of Viral Nanoparticles Based on Enhanced Dark-Field Optical Imaging

Nanoparticle self-assembly is a complex phenomenon, the control of which is complicated by the lack of appropriate tools and techniques for monitoring the phenomenon with adequate resolution in real-time. In this work, a label-free technique based on dark-field microscopy was developed to investigate the self-assembly of nanoparticles. A bio-nanoparticle with complex shape (T4 bacteriophage) that self-assembles on glass substrates upon drying was developed. The fluid flow regime during the drying process, as well as the final self-assembled structures, were studied using dark-field microscopy, while phage diffusion was analysed by tracking of the phage nanoparticles in the bulk solutions. The concentrations of T4 phage nanoparticles and salt ions were identified as the main parameters influencing the fluid flow, particle motion and, consequently, the resulting self-assembled structure. This work demonstrates the utility of enhanced dark-field microscopy as a label-free technique for the observation of drying-induced self-assembly of bacteriophage T4. This technique provides the ability to track the nano-sized particles in different matrices and serves as a strong tool for monitoring self-assembled structures and bottom-up assembly of nano-sized building blocks in real-time.

Combining Protein Cages and Polymers: from Understanding Self-Assembly to Functional Materials

Protein cages, such as viruses, are well-defined biological nanostructures which are highly symmetrical and monodisperse. They are found in various shapes and sizes and can encapsulate or template non-native materials. Furthermore, the proteins can be chemically or genetically modified giving them new properties. For these reasons, these protein structures have received increasing attention in the field of polymer-protein hybrid materials over the past years, however, advances are still to be made. This Viewpoint highlights the different ways polymers and protein cages or their subunits have been combined to understand self-assembly and create functional materials.

Design of virus-based nanomaterials for medicine, biotechnology, and energy

This review provides an overview of recent developments in "chemical virology." Viruses, as materials, provide unique nanoscale scaffolds that have relevance in chemical biology and nanotechnology, with diverse areas of applications. Some fundamental advantages of viruses, compared to synthetically programmed materials, include the highly precise spatial arrangement of their subunits into a diverse array of shapes and sizes and many available avenues for easy and reproducible modification. Here, we will first survey the broad distribution of viruses and various methods for producing virus-based nanoparticles, as well as engineering principles used to impart new functionalities. We will then examine the broad range of applications and implications of virus-based materials, focusing on the medical, biotechnology, and energy sectors. We anticipate that this field will continue to evolve and grow, with exciting new possibilities stemming from advancements in the rational design of virus-based nanomaterials.

Influence of Surface Topographical Cues on the Differentiation of Mesenchymal Stem Cells in Vitro

Adult stem cell research has been advanced in recent years because of the cells' attractive abilities of self-renewal and differentiation. Topography of materials is one of the key features that can be harnessed to regulate stem cell behaviors. Stem cells can interact with underlying material through nanosized integrin receptors. Therefore, the manipulation of topographical cues at a nanoscale level can be employed to modulate the cell fate. In this review, we focus our discussion on the different surface topographical cues, especially, with an emphasis on the viral nanoparticle-coated materials, and their effects on stem cell differentiation.

Facile fabrication of a 3D electrospun fibrous mat by ice-templating for a tumor spheroid culture

A 3D polycaprolactone fibrous mat was fabricated by using spherical ice as a template during electrospinning for stabilizing droplets in a spheroid culture.

Viral nano-hybrids for innovative energy conversion and storage schemes

Typical rod-like viruses (the Tobacco Mosaic Virus (TMV) and the Bacteriophage M13) are biological nanostructures that couple a 1D mono-dispersed morphology with a precisely defined topology of surface spaced and orthogonal reactive domains. These biogenic scaffolds offer a unique alternative to synthetic nano-platforms for the assembly of functional molecules and materials. Spatially resolved 1D arrays of inorganic-organic hybrid domains can thus be obtained on viral nano-templates resulting in the functional arrangement of photo-triggers and catalytic sites with applications in light energy conversion and storage. Different synthetic strategies are herein highlighted depending on the building blocks and with a particular emphasis on the molecular design of viral-templated nano-interfaces holding great potential for the dream-goal of artificial photosynthesis.

Development of large-scale size-controlled adult pancreatic progenitor cell clusters by an inkjet-printing technique

The generation of transplantable β-cells from pancreatic progenitor cells (PPCs) could serve as an ideal cell-based therapy for diabetes. Because the transplant efficiency depends on the size of islet-like clusters, it becomes one of the key research topics to produce PPCs with controlled cluster sizes in a scalable manner. In this study, we used inkjet printing to pattern biogenic nanoparticles, i.e., mutant tobacco mosaic virus (TMV), with different spot sizes to support the formation of multicellular clusters by PPCs. We successfully achieved TMV particle patterns with variable features and sizes by adjusting the surface wettability and printing speed. The spot sizes of cell-adhesive TMV mutant arrays were in the range of 50-150 μm diameter. Mouse PPCs were seeded on the TMV-RGD (arginine-glycine-aspartate)-patterned polystyrene (PS) substrate, which consists of areas that either favor (TMV-RGD) or prohibit (bare PS) cell adhesion. The PPCs stably attached, proliferated on top of the TMV-RGD support, thus resulting in the formation of uniform and confluent PPC clusters. Furthermore, the aggregated PPCs also maintained their multipotency and were positive for E-cadherin, indicating that the formation of cell-cell junctions is critical for enhanced cell-cell contact.

Confined chromophores in tobacco mosaic virus to mimic green fluorescent protein

Grafting green fluorescent protein-like chromophores in the 4 nm channel of tobacco mosaic virus greatly enhances its fluorescence emission.

Transient viscoelasticity study of tobacco mosaic virus/Ba(2+) superlattice

Recently, we reported a new method to synthesize the rod-like tobacco mosaic virus (TMV) superlattice. To explore its potentials in nanolattice templating and tissue scaffolding, this work focused the viscoelasticity of the superlattice with a novel transient method via atomic force microscopy (AFM). For measuring viscoelasticity, in contrast to previous methods that assessed the oscillating response, the method proposed in this work enabled us to determine the transient response (creep or relaxation) of micro/nanobiomaterials. The mathematical model and numerical process were elaborated to extract the viscoelastic properties from the indentation data. The adhesion between the AFM tip and the sample was included in the indentation model. Through the functional equation method, the elastic solution for the indentation model was extended to the viscoelastic solution so that the time dependent force vs. displacement relation could be attained. To simplify the solving of the differential equation, a standard solid model was modified to obtain the elastic and viscoelastic components of the sample. The viscoelastic responses with different mechanical stimuli and the dynamic properties were also investigated.

Formation of Core–Shell Structures in Emulsion Electrospun Fibres: A Comparative Study

Electrospinning has attracted great attention in recent years from different industries including biomedical engineering. Owing to the relative ease of fabricating ultrafine fibres with core–shell structures, emulsion electrospinning has been investigated intensively for making nanofibrous delivery vehicles for local and sustained release of bioactive or therapeutic substances, especially biomolecules such as growth factors. In preparing emulsions for electrospinning, different surfactants, ionic or non-ionic, can be used, which may subsequently influence the evolution of the core–shell structure in the electrospun emulsion jet or fibre. In this investigation, emulsions consisting of deionized water or phosphate buffer saline as the water phase, a poly(lactic-co-glycolic acid) solution as the oil phase and Span 80 (a non-ionic surfactant) or sodium dodecyl sulfate (an ionic surfactant) were electrospun into fibres for studying the core–shell structure and its evolution in emulsion electrospun fibres. Different microscopies were employed to study the morphological changes of the water phase in fibre samples collected at different locations along the jet (or fibre) trajectory during emulsion electrospinning. It was found that the evolution of the fibre core–shell structure was significantly different when different surfactants were used. If Span 80 was the surfactant, the water phase within the thick emulsion jet (or fibre) close to the Taylor cone existed in a discrete state whereas in ultrafine fibres collected beyond a certain distance from the Taylor cone, a mostly continuous water-phase core was observed. If sodium dodecyl sulfate was the surfactant, the core–shell structure in the thick jet (or fibre) was irregular but relatively continuous. A single core core–shell structure was eventually developed in ultrafine fibres. The core–shell structure in electrospun fibres and its evolution were also affected by the emulsion composition (e.g. polymer solution concentration, water-phase volume, and ion addition in the water phase).

Chemical modification of the inner and outer surfaces of Tobacco Mosaic Virus (TMV)

Viral nanoparticles derived from tobacco mosaic virus (TMV) find applications in various fields. We report the purification and chemical modification of TMV which is a hollow rod-shaped plant viral nanoparticle with modifiable interior and exterior surfaces. We describe methods to isolate TMV from its tobacco plant host for spatially controlled interior and exterior chemical modification and to characterize the resulting TMV hybrid materials.

Facile method for large scale alignment of one dimensional nanoparticles and control over myoblast orientation and differentiation

A facile and robust method to align one-dimensional (1D) nanoparticles (NPs) in large scale has been developed. Using flow assembly, representative rod-like nanoparticles, including tobacco mosaic virus (TMV), gold nanorods, and bacteriophage M13, have been aligned inside glass tubes by controlling flow rate and substrate surface properties. The properties of 1D NPs, such as stiffness and aspect ratio, play a critical role in the alignment. Furthermore, these hierarchically organized structures can be used to support cell growth and control the cell orientation and morphology. When C2C12 myoblasts were cultured on surfaces coated with aligned TMV, we found that nanoscale topographic features were critical to guide the cell orientation and myogenic differentiation. This method can therefore be used in the fabrication of complex assemblies with 1D NPs and have wide applications in tissue engineering, sensing, electronics, and optical fields.

Tobacco mosaic virus rods and spheres as supramolecular high-relaxivity MRI contrast agents

To compensate for the low sensitivity of magnetic resonance imaging (MRI), nanoparticles have been developed to deliver high payloads of contrast agents to sites of disease. Here, we report the development of supramolecular MRI contrast agents using the plant viral nanoparticle tobacco mosaic virus (TMV). Rod-shaped TMV nanoparticles measuring 300×18 nm were loaded with up to 3,500 or 2,000 chelated paramagnetic gadolinium (III) ions selectively at the interior (iGd-TMV) or exterior (eGd-TMV) surface, respectively. Spatial control is achieved through targeting either tyrosine or carboxylic acid side chains on the solvent exposed exterior or interior TMV surface. The ionic T₁ relaxivity per Gd ion (at 60 MHz) increases from 4.9 mM^-1s^-1 for free Gd(DOTA) to 18.4 mM^-1s^-1 for eGd-TMV and 10.7 mM^-1s^-1 for iGd-TMV. This equates to T₁ values of ~ 30,000 mM^-1s^-1 and ~ 35,000 mM^-1s^-1 per eGd-TMV and iGd-TMV nanoparticle. Further, we show that interior-labeled TMV rods can undergo thermal transition to form 170 nm-sized spherical nanoparticles containing ~ 25,000 Gd chelates and a per particle relaxivity of almost 400,000 mM^-1s^-1 (15.2 mM^-1s^-1 per Gd). This work lays the foundation for the use of TMV as a contrast agent for MRI.

Construction of GPx active centers on natural protein nanodisk/nanotube: a new way to develop artificial nanoenzyme

Construction of catalytic centers on natural protein aggregates is a challenging topic in biomaterial and biomedicine research. Here we report a novel construction of artificial nanoenzyme with glutathione peroxidase (GPx)-like function. By engineering the surface of tobacco mosaic virus (TMV) coat protein, the main catalytic components of GPx were fabricated on TMV protein monomers. Through direct self-assembly of the functionalized viral coat proteins, the multi-GPx centers were installed on these well-defined nanodisks or nanotubes. With the help of muti-selenoenzyme centers, the resulting organized nanoenzyme exhibited remarkable GPx activity, even approaching the level of natural GPx. The antioxidation study on subcell mitochondrial level demonstrated that virus-based nanoenzyme exerted excellent capacity for protecting cell from oxidative damage. This strategy represents a new way to develop artificial nanoenzymes.

Polyvalent display of RGD motifs on turnip yellow mosaic virus for enhanced stem cell adhesion and spreading

Turnip yellow mosaic virus (TYMV) is a stable 28 nm icosahedral plant virus that can be isolated in gram quantities. In order to study the polyvalent effect of Arg-Gly-Asp (RGD) clustering on the response of bone marrow stem cells (BMSCs), an RGD motif was genetically displayed on the coat protein of the TYMV capsid. Composite films composed of either wild-type TYMV or TYMV-RGD44, in combination with poly(allylamine hydrochloride) (PAH), were fabricated by a layer-by-layer adsorption of virus and PAH. The deposition process was studied by quartz crystal microbalance, UV-visible spectroscopy and atomic force microscopy. BMSC adhesion assays showed enhanced cell adhesion and spreading on TYMV-RGD44 coated substrates compared to native TYMV. These results demonstrate the potential of TYMV as a viable scaffold for bioactive peptide display and cell culturing studies.

Targeted binding of the M13 bacteriophage to thiamethoxam organic crystals

Phage display screening with a combinatorial library was used to identify M13-type bacteriophages that express peptides with selective binding to organic crystals of thiamethoxam. The six most strongly binding phages exhibit at least 1000 times the binding affinity of wild-type M13 and express heptapeptide sequences that are rich in hydrophobic, hydrogen-bonding amino acids and proline. Among the peptide sequences identified, M13 displaying the pIII domain heptapeptide ASTLPKA exhibits the strongest binding to thiamethoxam in competitive binding assays. Electron and confocal microscopy confirm the specific binding affinity of ASTLPKA to thiamethoxam. Using atomic force microscope (AFM) probes functionalized with ASTLPKA expressing phage, we found that the average adhesion force between the bacteriophage and a thiamethoxam surface is 1.47 ± 0.80 nN whereas the adhesion force of wild-type M13KE phage is 0.18 ± 0.07 nN. Such a strongly binding bacteriophage could be used to modify the surface chemistry of thiamethoxam crystals and other organic solids with a high degree of specificity.

Electrospun fibrous scaffolds promote breast cancer cell alignment and epithelial-mesenchymal transition

In this work we created electrospun fibrous scaffolds with random and aligned fiber orientations in order to mimic the three-dimensional structure of the natural extracellular matrix (ECM). The rigidity and topography of the ECM environment have been reported to alter cancer cell behavior. However, the complexity of the in vivo system makes it difficult to isolate and study such extracellular topographical cues that trigger cancer cells' response. Breast cancer cells were cultured on these fibrous scaffolds for 3-5 days. The cells showed elongated spindle-like morphology in the aligned fibers, whereas they maintained a mostly flat stellar shape in the random fibers. Gene expression profiling of these cells post seeding showed up-regulation of transforming growth factor β-1 (TGFβ-1) along with other mesenchymal biomarkers, suggesting that these cells undergo epithelial-mesenchymal transitions in response to the polymer scaffold. The results of this study indicate that the topographical cue may play a significant role in tumor progression.

Electron beam irradiation stiffens zinc tin oxide nanowires

We report a remarkable phenomenon that electron beam irradiation (EBI) significantly enhances the Young's modulus of zinc tin oxide (ZTO) nanowires (NWs), up to a 40% increase compared with the pristine NWs. In situ uniaxial buckling tests on individual NWs were conducted using a nanomanipulator inside a scanning electron microscope. We propose that EBI results in substantial atomic bond contraction in ZTO NWs, accounting for the observed mechanically stiffening. This argument is supported by our experimental results that EBI also reduces the electrical conductivity of ZTO NWs.

Biomimetic self-templating supramolecular structures

In nature, helical macromolecules such as collagen, chitin and cellulose are critical to the morphogenesis and functionality of various hierarchically structured materials. During tissue formation, these chiral macromolecules are secreted and undergo self-templating assembly, a process whereby multiple kinetic factors influence the assembly of the incoming building blocks to produce non-equilibrium structures. A single macromolecule can form diverse functional structures when self-templated under different conditions. Collagen type I, for instance, forms transparent corneal tissues from orthogonally aligned nematic fibres, distinctively coloured skin tissues from cholesteric phase fibre bundles, and mineralized tissues from hierarchically organized fibres. Nature's self-templated materials surpass the functional and structural complexity achievable by current top-down and bottom-up fabrication methods. However, self-templating has not been thoroughly explored for engineering synthetic materials. Here we demonstrate the biomimetic, self-templating assembly of chiral colloidal particles (M13 phage) into functional materials. A single-step process produces long-range-ordered, supramolecular films showing multiple levels of hierarchical organization and helical twist. Three distinct supramolecular structures are created by this approach: nematic orthogonal twists, cholesteric helical ribbons and smectic helicolidal nanofilaments. Both chiral liquid crystalline phase transitions and competing interfacial forces at the interface are found to be critical factors in determining the morphology of the templated structures during assembly. The resulting materials show distinctive optical and photonic properties, functioning as chiral reflector/filters and structural colour matrices. In addition, M13 phages with genetically incorporated bioactive peptide ligands direct both soft and hard tissue growth in a hierarchically organized manner. Our assembly approach provides insight into the complexities of hierarchical assembly in nature and could be expanded to other chiral molecules to engineer sophisticated functional helical-twisted structures.

Altering the landscape of viruses and bionanoparticles

In recent years, protein-based nanoparticles or bionanoparticles (BNPs), have been used as primary building blocks to generate ornate nanomaterials for a wide-range of applications. Over the past fifty years, numerous BNPs have been chemically modified or genetically engineered to function as smart drug/gene delivery vehicles, advanced vaccine vehicles, and isolated reaction vessels for inorganic, metallic, and semi-conductive depositions. These studies have contributed invaluable insights to the expansive capabilities of these simple, yet highly robust, nanosized building materials. Here we highlight some of the recent progress in the chemical modifications of BNPs and hopefully inspire the development of many new materials in the near future.