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.

Conformation-Stabilized Amorphous Nanocoating for Rational Design of Long-Term Thermostable Viral Vaccines

Despite the great potency of vaccines to combat infectious diseases, their global use is hindered by a lack of thermostability, which leads to a constant need for cold-chain storage. Here, aiming at long-term thermostability and eliminating cold-chain requirements of bioactive vaccines, we propose that efforts should focus on tailoring the conformational stability of vaccines. Accordingly, we design a nanocoating composed of histidine (His)-coordinated amorphous Zn and 2-methylimidazolate complex (His-aZn-mIM) on single nanoparticles of viral vaccines to introduce intramolecular coordinated linkage between viruses and the nanocoatings. The coordinated nanocoating enhances the rigidity of proteins and preserves the vaccine's activity. Importantly, integrating His into the original Zn-N coordinative environment symbiotically reinforces its tolerance to biological and hydrothermal solutions, resulting in the augmented thermostability following the Hofmeister effect. Thus, even after storage of His-aZn-mIM encapsulated Human adenovirus type 5 (Ad5@His-aZn-mIM) at 25 °C for 90 d, the potency loss of the coated Ad5 is less than 10%, while the native Ad5 becomes 100% ineffective within one month. Such a nanocoating gains thermostability by forming an ultrastable hydration shell, which prevents viral proteins from unfolding under the attack of hydration ions, providing a conformational stabilizer upon heat exposure. Our findings represent an easy-access biomimetic platform to address the long-term vaccine storage without the requirement of a cold chain.

The biomedical and bioengineering potential of protein nanocompartments

Protein nanocompartments (PNCs) are self-assembling biological nanocages that can be harnessed as platforms for a wide range of nanobiotechnology applications. The most widely studied examples of PNCs include virus-like particles, bacterial microcompartments, encapsulin nanocompartments, enzyme-derived nanocages (such as lumazine synthase and the E2 component of the pyruvate dehydrogenase complex), ferritins and ferritin homologues, small heat shock proteins, and vault ribonucleoproteins. Structural PNC shell proteins are stable, biocompatible, and tolerant of both interior and exterior chemical or genetic functionalization for use as vaccines, therapeutic delivery vehicles, medical imaging aids, bioreactors, biological control agents, emulsion stabilizers, or scaffolds for biomimetic materials synthesis. This review provides an overview of the recent biomedical and bioengineering advances achieved with PNCs with a particular focus on recombinant PNC derivatives.

Beyond biotemplating: multiscale porous inorganic materials with high catalytic efficiency

Biotemplating makes it possible to prepare materials with complex structures by taking advantage of nature's ability to generate unique morphologies.

Miranda B, Lodoso-Torrecilla I, van Nisselroy CAJ, Hoogenberg BJ, Dantuma S, Hollmann F, de Vries JW, Warszawik EM, Fischer R, Commandeur U, van Rijn P. Biocatalytically induced surface modification of the tobacco mosaic virus and the bacteriophage M13

A one-step laccase induced free radical oxidation of the tobacco mosaic virus and bacteriophage M13 led to acrylate-functionalized viruses with customizable properties.

Construction of Artificial Enzymes on a Virus Surface

Combination of artificial enzyme design and self-assembly strategies leads to a novel way to construct supramolecular enzymes. To address this challenge, auxotrophic expression systems show great potential because they can introduce nonnatural catalytic groups into the subunits of protein assemblies. Among nonnatural amino acids, selenocysteine is the catalytic group of glutathione peroxidase (GPx). With the aid of computer simulation, we have incorporated selenocysteine into natural protein assemblies such as tobacco mosaic virus (TMV) and ferritin by cysteine auxotrophic technology, resulting in the conversion of TMV and ferritin into supramolecular enzymes.

TMV-Templated Formation of Metal and Polymer Nanotubes

Metals and polymers are probably the most important construction materials, but also have many more functions, e.g., for electronics. The interaction of metal ions with tobacco mosaic virus (TMV) was originally used for the preparation of heavy metal isomorphic replacement for structural analysis. Metal ions can also be the precursors for metal clusters, particles, and layers. Various strategies have been developed, which allow the creation of metal layers on the external surface of TMV. Such layers can be made as metal tubes, enveloping a complete virion. An alternative strategy is adsorption of metal nanoparticles. If a dense coating of TMV is achieved, again a tube results. Nanoscale tubes have various physical properties that depend on size, crystallinity, uniformity, but especially on the nature of the metal. Polymer coatings are as yet rarely investigated, though they can be prepared quite easily.Here, a series of exemplary protocols is provided, which covers all of these different concepts.

Imaging Protein Fibers at the Nanoscale and In Situ

Protein self-assembly offers a rich repertoire of tools and technologies. However, despite significant progress in this area, a deterministic measure of the phenomenon, which might lead to predictable relationships between protein components, assembly mechanisms, and ultimately function, is lacking. Often the challenge relates to the choice of the most informative and precise measurements that can link the chemistry of the building blocks with the resulting assembly, ideally in situ and in real time. Using the example of protein fibrillogenesis-a self-assembly process fundamental to nearly every aspect of biological organization, from viral assembly to tissue restoration-this chapter demonstrates how protein self-assembly can be visually and precisely measured while providing measurement protocols applicable to other self-assembly systems.

Helical plant viral nanoparticles-bioinspired synthesis of nanomaterials and nanostructures

Viral nanotechnology is revolutionizing the biomimetic and bioinspired synthesis of novel nanomaterials. Bottom-up nanofabrication by self-assembly of individual molecular components of elongated viral nanoparticles (VNPs) and virus-like particles (VLPs) has resulted in the production of superior materials and structures in the nano(bio)technological fields. Viral capsids are attractive materials, because of their symmetry, monodispersity, and polyvalency. Helical VNPs/VLPs are unique prefabricated nanoscaffolds with large surface area to volume ratios and high aspect ratios, and enable the construction of exquisite supramolecular nanostructures. This review discusses the genetic and chemical modifications of outer, inner, and interface surfaces of a viral protein cage that will almost certainly lead to the development of superior next-generation targeted drug delivery and imaging systems, biosensors, energy storage and optoelectronic devices, therapeutics, and catalysts.

Tailoring the Self-Assembly Behaviors of Recombinant Tobacco Mosaic Virus by Rationally Introducing Covalent Bonding at the Protein-Protein Interface

Understanding the self-assembly mechanism of protein building blocks is important to realize the control of protein structures and functionalities. Here, for the first time, four different self-assembly behaviors of tobacco mosaic virus coat protein are reported from 2D disk arrays, disk stacks to 3D tube stacks, and tube bundles, respectively, with rationally mutated cysteines at 1, 3, and 103 sites.

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.

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.

Peptide-equipped tobacco mosaic virus templates for selective and controllable biomineral deposition

The coating of regular-shaped, readily available nanorod biotemplates with inorganic compounds has attracted increasing interest during recent years. The goal is an effective, bioinspired fabrication of fiber-reinforced composites and robust, miniaturized technical devices. Major challenges in the synthesis of applicable mineralized nanorods lie in selectivity and adjustability of the inorganic material deposited on the biological, rod-shaped backbones, with respect to thickness and surface profile of the resulting coating, as well as the avoidance of aggregation into extended superstructures. Nanotubular tobacco mosaic virus (TMV) templates have proved particularly suitable towards this goal: Their multivalent protein coating can be modified by high-surface-density conjugation of peptides, inducing and governing silica deposition from precursor solutions in vitro. In this study, TMV has been equipped with mineralization-directing peptides designed to yield silica coatings in a reliable and predictable manner via precipitation from tetraethoxysilane (TEOS) precursors. Three peptide groups were compared regarding their influence on silica polymerization: (i) two peptide variants with alternating basic and acidic residues, i.e. lysine-aspartic acid (KD) x motifs expected to act as charge-relay systems promoting TEOS hydrolysis and silica polymerization; (ii) a tetrahistidine-exposing polypeptide (CA4H4) known to induce silicification due to the positive charge of its clustered imidazole side chains; and (iii) two peptides with high ZnO binding affinity. Differential effects on the mineralization of the TMV surface were demonstrated, where a (KD) x charge-relay peptide (designed in this study) led to the most reproducible and selective silica deposition. A homogenous coating of the biotemplate and tight control of shell thickness were achieved.

Directed Growth of Virus Nanofilaments on a Superhydrophobic Surface

The evaporation of single droplets of colloidal tobacco mosaic virus (TMV) nanoparticles on a superhydrophobic surface with a hexagonal pillar-pattern results in the formation of coffee-ring type residues. We imaged surface features by optical, scanning electron, and atomic force microscopies. Bulk features were probed by raster-scan X-ray nanodiffraction. At ∼100 pg/μL nanoparticle concentration, the rim of the residue connects to neighboring pillars via fibrous extensions containing flow-aligned crystalline domains. At ∼1 pg/μL nanoparticle concentration, nanofilaments of ≥80 nm diameter and ∼20 μm length are formed, extending normal to the residue-rim across a range of pillars. X-ray scattering is dominated by the nanofilament form-factor but some evidence for crystallinity has been obtained. The observation of sheets composed of stacks of self-assembled nanoparticles deposited on pillars suggests that the nanofilaments are drawn from a structured droplet interface.

Genetically improved monolayer-forming tobacco mosaic viruses to generate nanostructured semiconducting bio/inorganic hybrids

The genetically determined design of structured functional bio/inorganic materials was investigated by applying a convective assembly approach. Wildtype tobacco mosaic virus (wt TMV) as well as several TMV mutants were organized on substrates over macroscopic-length scales. Depending on the virus type, the self-organization behavior showed pronounced differences in the surface arrangement under the same convective assembly conditions. Additionally, under varying assembly parameters, the virus particles generated structures encompassing morphologies emerging from single micrometer long fibers aligned parallel to the triple-contact line through disordered but dense films to smooth and uniform monolayers. Monolayers with diverse packing densities were used as templates to form TMV/ZnO hybrid materials. The semiconducting properties can be directly designed and tuned by the variation of the template architecture which are reflected in the transistor performance.

Different dimensional silica materials prepared using shaped block copolymer nanoobjects as catalytic templates

A general approach for fabrication of inorganic nanoobjects of different shapes was developed by using shaped core–shell block copolymer nanoobjects as catalytic templates.

Synthesis of comb-like poly(ethyleneimine)s and their application in biomimetic silicification

In this paper, we firstly synthesized comb polymers with crystallizable poly(ethyleneimine) (PEI) side chains, and further investigated their self-assembly behavior and catalytic templating role for silicification.

Production and applications of engineered viral capsids

As biological agents, viruses come in an astounding range of sizes, with varied shapes and surface morphologies. The structures of viral capsids are generally assemblies of hundreds of copies of one or a few proteins which can be harnessed for use in a wide variety of applications in biotechnology, nanotechnology, and medicine. Despite their complexity, many capsid types form as homogenous populations of precise geometrical assemblies. This is important in both medicine, where well-defined therapeutics are critical for drug performance and federal approval, and nanotechnology, where precise placement affects the properties of the desired material. Here we review the production of viruses and virus-like particles with methods for selecting and manipulating the size, surface chemistry, assembly state, and interior cargo of capsid. We then discuss many of the applications used in research today and the potential commercial and therapeutic products from engineered viral capsids.

Fabrication of nanoarchitectures templated by virus-based nanoparticles: strategies and applications

Biomolecular nanostructures in nature are drawing increasing interests in the field of materials sciences. As a typical group of them, virus-based nanoparticles (VNPs), which are nanocages or nanorods assembled from capsid proteins of viruses, have been widely exploited as templates to guide the fabrication of complex nanoarchitectures (NAs), because of their appropriate sizes (ca. 20-200 nm), homogeneity, addressable functionalization, facile modification via chemical and genetic routes, and convenient preparation. Foreign materials can be positioned in the inner cavity or on the outer surface of VNPs, through either direct synthesis or assembling preformed nanomaterials. Simultaneous use of the inner and outer space of VNPs facilitates integration of multiple functionalities in a single NA. This review briefly summarizes the strategies for fabrication of NAs templated by VNPs and wide applications of these NAs in fields of catalysis, energy, biomedicine, and nanophotonics, etc.

The use of tobacco mosaic virus and cowpea mosaic virus for the production of novel metal nanomaterials

Due to the nanoscale size and the strictly controlled and consistent morphologies of viruses, there has been a recent interest in utilizing them in nanotechnology. The structure, surface chemistries and physical properties of many viruses have been well elucidated, which have allowed identification of regions of their capsids which can be modified either chemically or genetically for nanotechnological uses. In this review we focus on the use of such modifications for the functionalization and production of viruses and empty viral capsids that can be readily decorated with metals in a highly tuned manner. In particular, we discuss the use of two plant viruses (Cowpea mosaic virus and Tobacco mosaic virus) which have been extensively used for production of novel metal nanoparticles (<100nm), composites and building blocks for 2D and 3D materials, and illustrate their applications.

Insights into biogenic and chemical production of inorganic nanomaterials and nanostructures

The synthesis of inorganic nanomaterials and nanostructures by the means of diverse physical, chemical, and biological principles has been developed in recent decades. The nanoscale materials and structures creation continue to be an active area of researches due to the exciting properties of the resulting nanomaterials and their innovative applications. Despite physical and chemical approaches which have been used for a long time to produce nanomaterials, biological resources as green candidates that can replace old production methods have been focused in recent years to generate various inorganic nanoparticles (NPs) or other nanoscale structures. Cost-effective, eco-friendly, energy efficient, and nontoxic produced nanomaterials using diverse biological entities have been received increasing attention in the last two decades in contrast to physical and chemical methods owe using toxic solvents, generate unwanted by-products, and high energy consumption which restrict the popularity of these ways employed in nanometric science and engineering. In this review, the biosynthesis of gold, silver, gold-silver alloy, magnetic, semiconductor nanocrystals, silica, zirconia, titania, palladium, bismuth, selenium, antimony sulfide, and platinum NPs, using bacteria, actinomycetes, fungi, yeasts, plant extracts and also informational bio-macromolecules including proteins, polypeptides, DNA, and RNA have been reported extensively to mention the current status of the biological inorganic nanomaterial production. In other hand, two well-known wet chemical techniques, namely chemical reduction and sol-gel methods, used to produce various types of nanocrystalline powders, metal oxides, and hybrid organic-inorganic nanomaterials have presented.

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.

Hybrid macroscopic fibers from the synergistic assembly between silica and filamentous viruses

In this work, we report the elaboration of macroscopic hybrid virus-silica fibers. By using a silicate sol as inorganic precursor combined with the filamentous fd virus, well-dispersed hybrid fibers are obtained in solution. These macroscopic fd-silica fibers exhibit a narrow distribution of their diameter, while their length is at the millimeter scale. A scenario of the morphosynthesis is proposed to account for the formation of these high aspect ratio hybrid fibers.

Engineered Tobacco mosaic virus mutants with distinct physical characteristics in planta and enhanced metallization properties

Tobacco mosaic virus mutants were engineered to alter either the stability or surface chemistry of the virion: within the coat protein, glutamic acid was exchanged for glutamine in a buried portion to enhance the inter-subunit binding stability (E50Q), or a hexahistidine tract was fused to the surface-exposed carboxy terminus of the coat protein (6xHis). Both mutant viruses were expected to possess specific metal ion affinities. They accumulated to high titers in plants, induced distinct phenotypes, and their physical properties during purification differed from each other and from wild type (wt) virus. Whereas 6xHis and wt virions contained RNA, the majority of E50Q protein assembled essentially without RNA into rods which frequently exceeded 2 μm in length. Electroless deposition of nickel metallized the outer surface of 6xHis virions, but the central channel of E50Q rods, with significantly more nanowires of increased length in comparison to those formed in wtTMV.