Tobacco Mosaic Virus-Based 1D Nanorod-Drug Carrier via the Integrin-Mediated Endocytosis Pathway

Cell-penetrating peptides in the intracellular delivery of viral nanoparticles

Cell-penetrating peptides (CPPs) are a promising tool for the intracellular delivery of cargo. Due to their ability to cross membranes while also cotransporting various cargoes, they offer great potential for biomedical applications. Several CPPs have been derived from viral proteins with natural roles in the viral replication cycle that require them to breach or fuse to cellular membranes. Additionally, the ability of viruses to cross membranes makes viruses and virus-based particles a convenient model for research on nanoparticle delivery and nanoparticle-mediated gene therapy. In this chapter, we aim to characterize CPPs derived from both structural and nonstructural viral proteins. Their function as enhancers of viral infection and transduction by viral nanoparticles as well as the main features of viral CPPs employed in intracellular cargo delivery are summarized to emphasize their potential use in nanomedicine.

The pharmacology of plant virus nanoparticles

The application of nanoparticles for medical purposes has made enormous strides in providing new solutions to health problems. The observation that plant virus-based nanoparticles (VNPs) can be repurposed and engineered as smart bio-vehicles for targeted drug delivery and imaging has launched extensive research for improving the therapeutic and diagnostic management of various diseases. There is evidence that VNPs are promising high value nanocarriers with potential for translational development. This is mainly due to their unique features, encompassing structural uniformity, ease of manufacture and functionalization by means of expression, chemical biology and self-assembly. While the development pipeline is moving rapidly, with many reports focusing on engineering and manufacturing aspects to tailor the properties and efficacy of VNPs, fewer studies have focused on gaining insights into the nanotoxicity of this novel platform nanotechnology. Herein, we discuss the pharmacology of VNPs as a function of formulation and route of administration. VNPs are reviewed in the context of their application as therapeutic adjuvants or nanocarrier excipients to initiate, enhance, attenuate or impede the formulation's toxicity. The summary of the data however also underlines the need for meticulous VNP structure-nanotoxicity studies to improve our understanding of their in vivo fates and pharmacological profiles to pave the way for translation of VNP-based formulations into the clinical setting.

Inorganic-organic Nanomaterials for Therapeutics and Molecular Imaging Applications

Background::

Surface modification of nanoparticles with targeting moieties can be achieved through bioconjugation chemistries to impart new Functionalities. Various polymeric nanoparticles have been used for the formulation of nanoparticles such as naturally-occurring protein cages, virus-like particles, polymeric saccharides, and liposomes. These polymers have been proven to be biocompatible, side effects free and degradable with no toxicity.

Objectives::

This paper reviews available literature on the nanoparticles pharmaceutical and medical applications. The review highlights and updates the customized solutions for selective drug delivery systems that allow high-affinity binding between nanoparticles and the target receptors.

Methods::

Bibliographic databases and web-search engines were used to retrieve studies that assessed the usability of nanoparticles in the pharmaceutical and medical fields. Data were extracted on each system in vivo and in vitro applications, its advantages and disadvantages, and its ability to be chemically and genetically modified to impart new functionalities. Finally, a comparison between naturally occurring and their synthetic counterparts was carried out.

Results::

The results showed that nanoparticles-based systems could have promising applications in diagnostics, cell labeling, contrast agents (Magnetic Resonance Imaging and Computed Tomography), antimicrobial agents, and as drug delivery systems. However, precautions should be taken to avoid or minimize toxic effect or incompatibility of nanoparticles-based systems with the biological systems in case of pharmaceutical or medical applications.

Conclusion::

This review presented a summary of recent developments in the field of pharmaceutical nanotechnology and highlighted the challenges and the merits that some of the nanoparticles- based systems both in vivo and in vitro systems.

Attachment of Ultralow Amount of Engineered Plant Viral Nanoparticles to Mesenchymal Stem Cells Enhances Osteogenesis and Mineralization

Hydrogel-based materials are widely used to mimic the extracellular matrix in bone tissue engineering, although they often lack biofunctional cues. In the authors' previous work, Potato virus X (PVX), a flexible rod-shaped biocompatible plant virus nanoparticle (VNP) with 1270 coat protein subunits, is genetically modified to present functional peptides for generating a bone substitute. Here, PVX is engineered to present mineralization- and osteogenesis-associated peptides and laden in hydrogels at a concentration lower by two orders of magnitude. Its competence in mineralization is demonstrated both on 2D surfaces and in hydrogels and the superiority of enriched peptides on VNPs is verified and compared with free peptides and VNPs presenting fewer functional peptides. Alkaline phosphatase activity and Alizarin red staining of human mesenchymal stem cells increase 1.2-1.7 times when stimulate by VNPs. Engineered PVX adheres to cells, exhibiting a stimulation of biomimetic peptides in close proximity to the cells. The retention of VNPs in hydrogels is monitored and more than 80% of VNPs remain inside after several washing steps. The mechanical properties of VNP-laden hydrogels are investigated, including viscosity, gelling temperature, and compressive tangent modulus. This study demonstrates that recombinant PVX nanoparticles are excellent candidates for hydrogel nanocomposites in bone tissue engineering.

Plant viral nanoparticles for packaging and in vivo delivery of bioactive cargos

Nanoparticles have unique capabilities and considerable promise for many different biological uses. One capability is delivering bioactive cargos to specific cells, tissues, or organisms. Depending on the task, there are multiple variables to consider including nanoparticle selection, targeting strategies, and incorporating cargo so it can be delivered in a biologically active form. One nanoparticle option, genetically controlled plant viral nanoparticles (PVNPs), is highly uniform within a given virus but quite variable between viruses with a broad range of useful properties. PVNPs are flexible and versatile tools for incorporating and delivering a wide range of small or large molecule cargos. Furthermore, PVNPs can be modified to create nanostructures that can solve problems in medical, environmental, and basic research. This review discusses the currently available techniques for delivering bioactive cargos with PVNPs and potential cargos that can be delivered with these strategies. This article is categorized under: Implantable Materials and Surgical Technologies > Nanomaterials and Implants Biology-Inspired Nanomaterials > Protein and Virus-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.

Cancer Theranostic Applications of Albumin-Coated Tobacco Mosaic Virus Nanoparticles

Nanotechnology holds great promise in cancer drug delivery, and of particular interest are theranostic approaches in which drug delivery and imaging are integrated. In this work, we studied and developed the plant virus tobacco mosaic virus (TMV) as a platform nanotechnology for drug delivery and imaging. Specifically, a serum albumin (SA)-coated TMV formulation was produced. The SA coating fulfils two functions: SA provides a stealth coating for enhanced biocompatibility; it also acts as a targeting ligand enabling efficient tumor accumulation of SA-TMV versus TMV in mouse models of breast and prostate cancer. We demonstrate drug delivery of the chemotherapy doxorubicin (DOX); TMV-delivered DOX outperformed free DOX, resulting in significant delayed tumor growth and increased survival. Furthermore, we demonstrated the ability of SA-coated TMV loaded with chelated Gd(DOTA) for magnetic resonance imaging detection of tumors. In the future, we envision the application of such probes as theranostic, where first imaging is performed to assess whether the nanoparticles are effective at targeting a particular patient tumor. If targeting is confirmed, the therapeutic would be added and treatment can begin. The combination of imaging and therapy would allow to monitor disease progression and therefore inform about the effectiveness of the drug delivery approach.

Integration of Cell-Penetrating Peptides with Rod-like Bionanoparticles: Virus-Inspired Gene-Silencing Technology

Inspired by the high gene transfer efficiency of viral vectors and to avoid side effects, we present here a 1D rod-like gene-silencing vector based on a plant virus. By decorating the transacting activator of transduction (TAT) peptide on the exterior surface, the TAT-modified tobacco mosaic virus (TMV) achieves a tunable isoelectric point (from ∼3.5 to ∼9.6) depending on the TAT dose. In addition to enhanced cell internalization, this plant virus-based vector (TMV-TAT) acquired endo/lysosomal escape capacity without inducing lysosomal damage, resulting in both high efficiency and low cytotoxicity. By loading silencer green fluorescent protein (GFP) siRNA onto the TMV-TAT vector (siRNA@TMV-TAT) and interfering with GFP-expressing mouse epidermal stem cells (ESCs/GFP) in vitro, the proportion of GFP-positive cells could be knocked down to levels even lower than 15% at a concentration of ∼100% cell viability. Moreover, by interfering with GFP-expressing highly metastatic hepatocellular carcinoma (MHCC97-H/GFP) tumors in vivo, treatment with siRNA@TMV-TAT complexes for 10 days achieved a GFP-negative rate as high as 80.8%. This work combines the high efficiency of viral vectors and the safety of nonviral vectors and may provide a promising strategy for gene-silencing technology.

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.

Fluorous interaction induced self-assembly of tobacco mosaic virus coat protein for cisplatin delivery

Tobacco mosaic virus coat protein was modified with a small molecular fluorous ponytail at specific sites, and self-assembled into spherical nanoparticles through fluorous interaction induced self-assembly. By loading the anti-cancer drug cisplatin through metal-ligand coordination, this spherical assembly with high stability has potential as a drug carrier.

Speciation of Phenanthriplatin and Its Analogs in the Core of Tobacco Mosaic Virus

Efficient loading of drugs in novel delivery agents has the potential to substantially improve therapy by targeting the diseased tissue while avoiding unwanted side effects. Here we report the first systematic study of the loading mechanism of phenanthriplatin and its analogs into tobacco mosaic virus (TMV), previously used by our group as an efficient carrier for anticancer drug delivery. A detailed investigation of the preferential uptake of phenanthriplatin in its aquated form (∼2000 molecules per TMV particle versus ∼1000 for the chlorido form) is provided. Whereas the net charge of phenanthriplatin analogs and their ionic mobilities have no effect on loading, the reactivity of aqua phenanthriplatin with the glutamates, lining the interior walls of the channel of TMV, has a pronounced effect on its loading. MALDI-MS analysis along with NMR spectroscopic studies of a model reaction of hydroxy-phenanthriplatin with acetate establish the formation of stable covalent adducts. The increased number of heteroaromatic rings on the platinum ligand appears to enhance loading, possibly by stabilizing hydrophobic stacking interactions with TMV core components, specifically Pro102 and Thr103 residues neighboring Glu97 and Glu106 in the channel. Electron transfer dissociation MS/MS fragmentation, a technique that can prevent mass-condition-vulnerable modification of proteins, reveals that Glu97 preferentially participates over Glu106 in covalent bond formation to the platinum center.

TMV Disk Scaffolds for Making sub-30 nm Silver Nanorings

Nanosized bioscaffolds can be utilized to tackle the challenge of size reduction of metallic rings owing to their miniature features as well as their well-known biomineralization capacity. The tobacco mosaic virus coat protein is used as a command surface to grow and assemble silver nanoparticles into sub-30 nm rings. The versatility of TMV allows the formation of both solid silver rings and rings consisting of discrete silver nanoparticles. The pH-dependent coulombic surface map along with the annular geometry of the protein aggregate allow the generation of rings with or without a central nanoparticle. Our silver rings are believed to be the smallest to date, and they can offer a test material for existing theories on metallic nanorings of this heretofore unreached size scale.

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.

Pt-Ni nanoframes functionalized with carbon dots: an emerging class of bio-nanoplatforms

We designed a unique and novel bio-nanoplatform based on Pt-Ni nanoframes (PNnf) functionalized with carbon dots via the EDC/NHS coupling chemistry. The PNnf with open three-dimensional surfaces exhibited excellent water solubility after polyethylenimine modification. Due to low cytotoxicity and excellent biocompatibility, the bio-nanoplatforms were firstly used for MCF-7 cell imaging in vitro. More importantly, the design strategy can be readily generalized to facilitate other multi-functional bio-nanoplatforms for biological and biomedical applications.

Plant viruses and bacteriophages for drug delivery in medicine and biotechnology

There are a wide variety of synthetic and naturally occurring nanomaterials under development for nanoscale cargo-delivery applications. Viruses play a special role in these developments, because they can be regarded as naturally occurring nanomaterials evolved to package and deliver cargos. While any nanomaterial has its advantage and disadvantages, viral nanoparticles (VNPs), in particular the ones derived from plant viruses and bacteriophages, are attractive options for cargo-delivery as they are biocompatible, biodegradable, and non-infectious to mammals. Their protein-based structures are often understood at atomic resolution and are amenable to modification with atomic-level precision through chemical and genetic engineering. Here we present a focused review of the emerging technology development of plant viruses and bacteriophages targeting human health and agricultural applications. Key target areas of development are their use in chemotherapy, photodynamic therapy, pesticide-delivery, gene therapy, vaccine carriers, and immunotherapy.

Glyco-decorated tobacco mosaic virus as a vector for cisplatin delivery

Plant viruses have been applied broadly in nanomedical applications profiting from their monodisperse structure, biocompatibility, easy modification, and non-pathogenicity in animals. Here we report a tobacco mosaic virus (TMV) based drug delivery system bearing carbohydrates as targeting ligands. Mannose (Man) and lactose (Lac) moieties were separately conjugated to the exterior surface of TMV (TMV-Man and TMV-Lac) through an efficient copper(i)-catalyzed azide-alkyne cycloaddition. Cisplatin (CDDP), an anticancer drug, was directly loaded into the TMV cavity (CDDP@TMV, CDDP@TMV-Man and CDDP@TMV-Lac) via a metal coordination bond. Through the specific recognition between carbohydrates and glycoproteins in cell membranes, these TMV based vectors show specificity in different cell lines: in the galectin-rich MCF-7 cell line, CDDP@TMV-Man shows enhanced endocytosis and apoptosis efficiency; in the asialoglycoprotein receptor (ASGPR)-overexpressing HepG2 cell line, CDDP@TMV-Lac shows superiority in endocytosis and apoptosis. This research provides a new strategy for tumor-targeted cisplatin delivery.

Potato virus X, a filamentous plant viral nanoparticle for doxorubicin delivery in cancer therapy

Plant viral nanoparticles (VNPs) are a novel class of nanocarriers with implications for drug delivery in cancer therapy. VNPs are characterized by their highly symmetrical nanoscale structures. Furthermore, plant VNPs are biocompatible, biodegradable, and non-infectious in mammals. VNPs provide a proteinaceous platform technology that can be readily engineered to carry contrast agents and therapies using chemical and genetic modifications. Of particular interest are high aspect ratio, elongated filaments such as the ones formed by potato virus X (PVX, measuring 515 × 13 nm). PVX has demonstrated enhanced tumor homing and penetration properties compared to spherical counterparts. Here, we sought to investigate the potential of PVX as a drug carrier delivering doxorubicin (DOX), a commonly used cancer chemotherapy. We synthesized therapeutic PVX nanoparticles using a simple in-solution mixing protocol; after 5 days of mixing of DOX and PVX and ultra-centrifugal purification, ∼1000 DOX per PVX were stably associated with the carrier, most likely based on hydrophobic interaction. Efficacy and drug activity of PVX-DOX were confirmed using a panel of cancer cell lines including ovarian cancer, breast cancer, and cervical cancer. Lastly, we demonstrated treatment of athymic mice bearing human MDA-MB-231 breast cancer xenografts: PVX-DOX treatment resulted in reduced tumor growth in this model. Our results open the door for further development of PVX and other high aspect ratio plant VNPs for applications in cancer therapy.

Integrins in the Spotlight of Cancer

Integrins are heterodimeric cell surface receptors that bind to different extracellular ligands depending on their composition and regulate all processes which enable multicellular life. In cancer, integrins trigger and play key roles in all the features that were once described as the Hallmarks of Cancer. In this review, we will discuss the contribution of integrins to these hallmarks, including uncontrolled and limitless proliferation, invasion of tumor cells, promotion of tumor angiogenesis and evasion of apoptosis and resistance to growth suppressors, by highlighting the latest findings. Further on, given the paramount role of integrins in cancer, we will present novel strategies for integrin inhibition that are starting to emerge, promising a hopeful future regarding cancer treatment.