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

The de novo strategy for bifunctional peptides coating to enhance osteointegration capacity of the implant

Bone implants represent a significant global market; however, they are plagued by a high long-term failure rate, with approximately 19.2 % of implants failing within 10 years. This leads to considerable physical pain, mental distress for patients, and a substantial financial burden on public healthcare systems. Herein, we propose a novel strategy that using the interactions between positively charged hexa-arginine (R6) and polyphenols in EGC/Fe MPN to present the bifunctional peptides, cellular adhesive peptide (RGD) and osteogenic growth peptide (OGP), onto implant coatings. To thoroughly investigate the preparation process and the physical and chemical properties of the dual-peptide functionalized coatings, several techniques were employed, including dissipation-quartz crystal microbalance (DQCM), ellipsometry, photoelectron spectroscopy (XPS), and atomic force microscopy (AFM). These methods provided insights into the coating's composition, stability, mechanical properties, and surface roughness. In comparison to single-peptide functionalized coatings, the dual-peptide coatings demonstrated significantly improved performance in cellular adhesion at early stages, long-term cell proliferation, migration, antioxidant activity, osteogenic differentiation, inhibition of osteoclastogenesis, and enhanced in vivo osteointegration. This study contributes to the development of multifunctional coatings tailored to the complex biological processes involved in osteointegration.

The generation of empty Turnip yellow mosaic virus capsids through depletion of virion-associated divalent cations

Turnip yellow mosaic virus (TYMV) is a well-studied icosahedral plant virus that has attractive properties for nanoscience applications. Stable empty particles devoid of viral genomic RNA have historically been generated from virions by: 1. high pressure; 2. extreme alkaline pH; and 3. freeze-thaw using liquid nitrogen. Herein we report a fourth and more convenient avenue for empty particle formation through EDTA treatment, implicating chelation of virion-associated cations. We present findings that confirm TYMV virions purified in an EDTA-based buffer are converted to 94 % empty on average during purification. Additional experimentation revealed TYMV virions purified through CsCl vs. sucrose gradients are more readily converted to empty particles after freeze thaw. These studies are novel as they show a purification method through EDTA-treatment that can generate stable empty particles devoid of viral genome. The convenience of this method should prove suitable for scientists seeking to use TYMV capsids in nanoscience-inspired applications. Importantly, these findings provide insight into historical discrepancies in creating empty particles after freeze-thaw, as the method in which TYMV virions are purified influences the downstream virion-to-empty conversion process.

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.

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.

Application of Plant Viruses as a Biotemplate for Nanomaterial Fabrication

Viruses are widely used to fabricate nanomaterials in the field of nanotechnology. Plant viruses are of great interest to the nanotechnology field because of their symmetry, polyvalency, homogeneous size distribution, and ability to self-assemble. This homogeneity can be used to obtain the high uniformity of the templated material and its related properties. In this paper, the variety of nanomaterials generated in rod-like and spherical plant viruses is highlighted for the cowpea chlorotic mottle virus (CCMV), cowpea mosaic virus (CPMV), brome mosaic virus (BMV), and tobacco mosaic virus (TMV). Their recent studies on developing nanomaterials in a wide range of applications from biomedicine and catalysts to biosensors are reviewed.

Upregulation of osteogenesis of mesenchymal stem cells with virus-based thin films

A major aim of tissue engineering is to develop biomimetic scaffolding materials that can guide the proliferation, self-renewal and differentiation of multipotent stem cells into specific lineages. Cellular functions can be controlled by the interactions between cells and biomaterials. Therefore, the surface chemistry and topography of support materials play a pivotal role in modulating cell behaviors at many stages of cell growth and development. Due to their highly ordered structure and programmable surface chemistries, which provide unique topography as biomaterials, viral nanoparticles have been utilized as building blocks for targeted cell growth and differentiation. This review article discusses the fabrication of two-dimensional virus-based thin film on substrates and highlights the study of the effect of chemical and physical cues introduced by plant virus nanoparticle thin films on the promotion of osteogenic differentiation of BMSCs.

Engineered Potato virus X nanoparticles support hydroxyapatite nucleation for improved bone tissue replacement

Bionanoparticles based on filamentous phages or flexuous viruses are interesting candidates for meeting the challenges of tailoring biomineralization in hydrogel-based bone tissue substitutes. We hypothesized that hydroxyapatite crystal nucleation and matrix mineralization can be significantly increased by mineralization-inducing (MIP) and integrin binding motif (RGD) peptides presented on biomimetic nanoparticles. In this study, Potato virus X (PVX), a flexible rod-shaped plant virus was genetically engineered to present these functional peptides on its particle surface. Recombinant PVX-MIP/RGD particles were isolated from infected Nicotiana benthamiana plants and characterized by western blot, SEM, TEM, and TPLSM in MSC cultures. The presence of RGD was proven by cell attachment, spreading, and vinculin cluster analysis, and MIP by in vitro mineralization and osteogenic differentiation assays. Thus the tailored surface of genetically engineered PVX forms fibril-like nanostructures which enables enhanced focal adhesion-dependent cell adhesion, and matrix mineralization verified by Alizarin. Hydroxyapatite crystal nucleation is supported on recombinant PVX particles leading to a biomimetic network and bundle-like structures similar to mineralized collagen fibrils. In conclusion, the recombinant flexuous PVX nanoparticles exhibit properties with great potential for bone tissue substitutes.

STATEMENT OF SIGNIFICANCE

A suitable biomaterial for tissue engineering should be able to mimic the endogenous extracellular matrix by presenting biochemical and biophysical cues. Novel hydrogel-based materials seek to meet the criteria of cytocompatibility, biodegradability, printability, and crosslinkability under mild conditions. However, a majority of existing hydrogels lack cell-interactive motifs, which are crucial to modulate cellular responses. The incorporation of the plant virus PVX to the hydrogel could improve functions like integrin-binding and mineralization due to peptide-presentation on the particle surface. The tailored surface of genetically engineered PVX forms fibril-like nanostructures which enables enhanced focal adhesion-dependent cell adhesion and matrix mineralization and offers great potential for the development of new hydrogel compositions for bone tissue substitutes.

Icosahedral plant viral nanoparticles - bioinspired synthesis of nanomaterials/nanostructures

Viral nanotechnology utilizes virus nanoparticles (VNPs) and virus-like nanoparticles (VLPs) of plant viruses as highly versatile platforms for materials synthesis and molecular entrapment that can be used in the nanotechnological fields, such as in next-generation nanoelectronics, nanocatalysis, biosensing and optics, and biomedical applications, such as for targeting, therapeutic delivery, and non-invasive in vivo imaging with high specificity and selectivity. In particular, plant virus capsids provide biotemplates for the production of novel nanostructured materials with organic/inorganic moieties incorporated in a very precise and controlled manner. Interestingly, capsid proteins of spherical plant viruses can self-assemble into well-organized icosahedral three-dimensional (3D) nanoscale multivalent architectures with high monodispersity and structural symmetry. Using viral genetic and protein engineering of icosahedral viruses with a variety of sizes, the interior, exterior and the interfaces between coat protein (CP) subunits can be manipulated to fabricate materials with a wide range of desirable properties allowing for biomineralization, encapsulation, infusion, controlled self-assembly, and multivalent ligand display of nanoparticles or molecules for varied applications. In this review, we discuss the various functional nanomaterials/nanostructures developed using the VNPs and VLPs of different icosahedral plant viruses and their nano(bio)technological and nanomedical applications.

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.

Cartilage oligomeric matrix protein gene multilayers inhibit osteogenic differentiation and promote chondrogenic differentiation of mesenchymal stem cells

There are still many challenges to acquire the optimal integration of biomedical materials with the surrounding tissues. Gene coatings on the surface of biomaterials may offer an effective approach to solve the problem. In order to investigate the gene multilayers mediated differentiation of mesenchymal stem cells (MSCs), gene functionalized films of hyaluronic acid (HA) and lipid-DNA complex (LDc) encoding cartilage oligomeric matrix protein (COMP) were constructed in this study via the layer-by-layer self-assembly technique. Characterizations of the HA/DNA multilayered films indicated the successful build-up process. Cells could be directly transfected by gene films and a higher expression could be obtained with the increasing bilayer number. The multilayered films were stable for a long period and DNA could be easily released in an enzymatic condition. Real-time polymerase chain reaction (RT-PCR) assay presented significantly higher (p < 0.01) COMP expression of MSCs cultured with HA/COMP multilayered films. Compared with control groups, the osteogenic gene expression levels of MSCs with HA/COMP multilayered films were down-regulated while the chondrogenic gene expression levels were up-regulated. Similarly, the alkaline phosphatase (ALP) staining and Alizarin red S staining of MSCs with HA/COMP films were weakened while the alcian blue staining was enhanced. These results demonstrated that HA/COMP multilayered films could inhibit osteogenic differentiation and promote chondrogenic differentiation of MSCs, which might provide new insight for physiological ligament-bone healing.

Application of Nanoscaffolds in Mesenchymal Stem Cell-Based Therapy

Regenerative medicine is an alternative solution for organ transplantation. Stem cells and nanoscaffolds are two essential components in regenerative medicine. Mesenchymal stem cells (MSCs) are considered as primary adult stem cells with high proliferation capacity, wide differentiation potential, and immunosuppression properties which make them unique for regenerative medicine and cell therapy. Scaffolds are engineered nanofibers that provide suitable microenvironment for cell signalling which has a great influence on cell proliferation, differentiation, and biology. Recently, application of scaffolds and MSCs is being utilized in obtaining more homogenous population of MSCs with higher cell proliferation rate and greater differentiation potential, which are crucial factors in regenerative medicine. In this review, the definition, biology, source, characterization, and isolation of MSCs and current report of application of nanofibers in regenerative medicine in different lesions are discussed.

Plant virus incorporated hydrogels as scaffolds for tissue engineering possess low immunogenicity in vivo

Viruses are no longer recognized purely for being ubiquitous pathogens, but have served as building blocks for material chemistry and nanotechnology. Thousands of coat protein subunits of a viral particle can be modified chemically and/or genetically. We have previously shown that the three-dimensional porous hydrogels can easily be functionalized by Tobacco mosaic virus (TMV), a rod-like plant virus, using its mutant, RGD-TMV. RGD-TMV hosted bioadhesive peptide (RGD) in the hydrogel, which was shown to enhance cell attachment and promote osteogenic differentiation of cultured stem cell. To translate this technology to potential clinical applications, we sought to study the biocompatibility of the hydrogel. In this paper, the hydrogels were implanted in vivo and assessed for their immunogenicity, toxicity, and biodegradability. Immune response for TMV substantially decreased when incorporated in the hydrogel implants. The implanted TMV hydrogels exhibited no apparent toxicity and were degradable in mice. The results highlighted the feasibility of using TMV incorporated hydrogels as scaffolding materials for regenerative medicine in terms of biocompatibility and biodegradability.

RGD-conjugated rod-like viral nanoparticles on 2D scaffold improve bone differentiation of mesenchymal stem cells

Viral nanoparticles have uniform and well-defined nano-structures and can be produced in large quantities. Several plant viral nanoparticles have been tested in biomedical applications due to the lack of mammalian cell infectivity. We are particularly interested in using Tobacco mosaic virus (TMV), which has been demonstrated to enhance bone tissue regeneration, as a tunable nanoscale building block for biomaterials development. Unmodified TMV particles have been shown to accelerate osteogenic differentiation of adult stem cells by synergistically upregulating bone morphogenetic protein 2 (BMP2) and integrin-binding bone sialoprotein (IBSP) expression with dexamethasone. However, their lack of affinity to mammalian cell surface resulted in low initial cell adhesion. In this study, to increase cell binding capacity of TMV based material the chemical functionalization of TMV with arginine-glycine-aspartic acid (RGD) peptide was explored. An azide-derivatized RGD peptide was "clicked" to tyrosine residues on TMV outer surface via an efficient copper(I) catalyzed azide-alkyne cycloaddition (CuAAC) reaction. The ligand spacing is calculated to be 2-4 nm, which could offer a polyvalent ligand clustering effect for enhanced cell receptor signaling, further promoting the proliferation and osteogenic differentiation of bone marrow-derived mesenchymal stem cells (BMSCs).

Phage-based nanomaterials for biomedical applications

Recent advances in nanotechnology enable us to manipulate and produce materials with molecular level control. In the newly emerging field of bionanomedicine, it is essential to precisely control the physical, chemical and biological properties of materials. Among other biological building blocks, viruses are a promising nanomaterial that can be functionalized with great precision. Since the production of viral particles is directed by the genetic information encapsulated in their protein shells, the viral particles create precisely defined sizes and shapes. In addition, the composition and surface properties of the particles can be controlled through genetic engineering and chemical modification. In this manuscript, we review the advances of virus-based nanomaterials for biomedical applications in three different areas: phage therapy, drug delivery and tissue engineering. By exploiting and manipulating the original functions of viruses, viral particles hold great possibilities in these biomedical applications to improve human health.

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.

Cucumber mosaic virus as drug delivery vehicle for doxorubicin

Taking advantage of the unique structure feature of cucumber mosaic virus (CMV), we have anchored folic acid (FA) as targeting moiety on the rigid CMV capsid and loaded significant amount of doxorubicin (Dox) into the interior cavity of CMV through the formation of Dox-RNA conjugate to provide a nanosized control delivery system for cancer therapy. The FA-CMV-Dox assemblies were characterized using transmission electron microscopy and size exclusion chromatography, which disclose that they have comparable size and morphology to the native CMV particles. The Dox-loaded viral particles exhibit sustained in vitro Dox release profile over 5 days at physiological pH but can be liberated from the conjugates with the presence of elevated level of RNase. The in vitro effects of folate receptor (FR)-targeted CMV-Dox nanoconjugates on cellular internalization and cell proliferation were evaluated by live-cell imaging, MTT and TUNEL assay, respectively, in mouse cardiomyocytes and FR over expression OVCAR-3 tumor cells. The in vivo efficacy was also investigated in the OVCAR-3 BALB/c nude mouse xenograft model through histological alterations and TUNEL assessment. The FA-CMV-Dox particles significantly decrease the accumulation of Dox in the nuclei of mouse myocardial cells and improve the uptake of Dox in the ovarian cancer, leading to less cardiotoxicity and enhanced antitumor effect. We believe that CMV offers a new way to fabricate nanosized drug delivery vehicles.

Tools from viruses: bacteriophage successes and beyond

Viruses are ubiquitous and can infect any of the three existing cellular lineages (Archaea, Bacteria and Eukarya). Despite the persisting negative public perception of these entities, scientists learnt how to domesticate some of them. The study of molecular mechanisms essential to the completion of viral cycles has greatly contributed to deciphering fundamental processes in biology. Nowadays, viruses have entered the biotechnological era and numerous applications have already been developed. Viral-derived tools are used to manipulate genetic information, detect, diagnose, control and cure infectious diseases, or even design new structural assemblies. With the recent advances in the field of metagenomics, an overwhelming amount of information on novel viruses has become available. As current tools have been historically developed from a limited number of viruses, the potential of discoveries from new archaeal, bacterial and eukaryotic viruses may be limited only by our understanding of the multiple facets of viral cycles.