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

Advanced Fusion Strategies for the Production of Functionalized Potato Virus X Virions

Plant virions are ideal for nanotechnology applications because they are structurally diverse and can self-assemble naturally, allowing for large-scale production in plants by molecular farming. Potato virus X (PVX) is particularly amenable due to the unique properties of its filamentous and flexible capsid, but efficient strategies are required to adapt the surface properties of PVX, such as the attachment of proteins and peptides. This chapter describes the selection and utilization of 2A ribosomal skip sequences, allowing the presentation of heterologous proteins and peptides as N-terminal fusions to the PVX coat protein at different densities. Another strategy for the rapid modification of PVX capsids is the plug-and-display module of the SpyTag/SpyCatcher system. The SpyTag can be presented on the PVX surface, allowing for the attachment of any protein fused to the SpyCatcher sequence.

Bioconjugation of Active Ingredients to Plant Viral Nanoparticles Is Enhanced by Preincubation with a Pluronic F127 Polymer Scaffold

Proteinaceous nanoparticles can be used to deliver large payloads of active ingredients, which is advantageous in medicine and agriculture. However, the conjugation of hydrophobic ligands to hydrophilic nanocarriers such as plant viral nanoparticles (plant VNPs) can result in aggregation by reducing overall solubility. Given the benefits of hydrophilic nanocarrier platforms for targeted delivery and multivalent ligand display, coupled with the versatility of hydrophobic drugs, contrast agents, and peptides, this is an issue that must be addressed to realize their full potential. Here, we report two preincubation strategies that use a Pluronic F127 polymer scaffold to prevent the aggregation of conjugated plant VNPs: a plant VNP-polymer precoat (COAT) and an active ingredient formulation combined with a plant VNP-polymer precoat (FORMCOAT). The broad applications of these modified conjugation strategies were highlighted by testing their compatibility with three types of bioconjugation chemistry: N-hydroxysuccinimide ester-amine coupling, maleimide-thiol coupling, and copper(I)-catalyzed azide-alkyne cycloaddition (click chemistry). The COAT and FORMCOAT strategies promoted efficient bioconjugation and prevented the aggregation that accompanies conventional bioconjugation methods, thus improving the stability, homogeneity, and translational potential of plant VNP conjugates in medicine and agriculture.

Tetrahedral DNA nanostructures for effective treatment of cancer: advances and prospects

Recently, DNA nanostructures with vast application potential in the field of biomedicine, especially in drug delivery. Among these, tetrahedral DNA nanostructures (TDN) have attracted interest worldwide due to their high stability, excellent biocompatibility, and simplicity of modification. TDN could be synthesized easily and reproducibly to serve as carriers for, chemotherapeutic drugs, nucleic acid drugs and imaging probes. Therefore, their applications include, but are not restricted to, drug delivery, molecular diagnostics, and biological imaging. In this review, we summarize the methods of functional modification and application of TDN in cancer treatment. Also, we discuss the pressing questions that should be targeted to increase the applicability of TDN in the future.

Customized materials-assisted microorganisms in tumor therapeutics

Microorganisms have been extensively applied as active biotherapeutic agents or drug delivery vehicles for antitumor treatment because of their unparalleled bio-functionalities. Taking advantage of the living attributes of microorganisms, a new avenue has been opened in anticancer research. The integration of customized functional materials with living microorganisms has demonstrated unprecedented potential in solving existing questions and even conferring microorganisms with updated antitumor abilities and has also provided an innovative train of thought for enhancing the efficacy of microorganism-based tumor therapy. In this review, we have summarized the emerging development of customized materials-assisted microorganisms (MAMO) (including bacteria, viruses, fungi, microalgae, as well as their components) in tumor therapeutics with an emphasis on the rational utilization of chosen microorganisms and tailored materials, the ingenious design of biohybrid systems, and the efficacious antitumor mechanisms. The future perspectives and challenges in this field are also discussed.

Tumor Microenvironment Responsive Pepper Mild Mottle Virus-Based Nanotubes for Targeted Delivery and Controlled Release of Paclitaxel

Plant virus nanoparticles (PVNPs) have been widely used for drug delivery, antibody development and medical imaging because of their good biodegradation and biocompatibility. Particles of pepper mild mottle virus (PMMoV) are elongated and may be useful as drug carriers because their shape favours long circulation, preferential distribution and increased cellular uptake. Moreover, its effective degradation in an acidic microenvironment enables a pH-responsive release of the encapsulated drug. In this study, genetic engineering techniques were used to form rod-shaped structures of nanoparticles (PMMoV) and folated-modified PMMoV nanotubes were prepared by polyethylene glycol (PEG) to provide targeted delivery of paclitaxel (PTX). FA@PMMoV@PTX nanotubes were designed to selectively target tumor cells and to release the encapsulated PTX in response to pH. Efficient cell uptake of FA@PMMoV@PTX nanotubes was observed when incubated with tumor cells, and FA@PMMoV@PTX nanotubes had superior cytotoxicity to free PTX, as reflected by cell survival and apoptosis. This system is a strong candidate for use in developing improved strategies for targeted treatment of tumors.

Use of lentiviral vectors in vaccination

INTRODUCTION

Lentiviral vectors have emerged as powerful vectors for vaccination, due to their high efficiency to transduce dendritic cells and to induce long-lasting humoral immunity, CD8⁺ T cells, and effective protection in numerous preclinical animal models of infection and oncology.

AREAS COVERED

Here, we reviewed the literature, highlighting the relevance of lentiviral vectors in vaccinology. We recapitulated both their virological and immunological aspects of lentiviral vectors. We compared lentiviral vectors to the gold standard viral vaccine vectors, i.e. adenoviral vectors, and updated the latest results in lentiviral vector-based vaccination in preclinical models.

EXPERT OPINION

Lentiviral vectors are non-replicative, negligibly inflammatory, and not targets of preexisting immunity in human populations. These are major characteristics to consider in vaccine development. The potential of lentiviral vectors to transduce non-dividing cells, including dendritic cells, is determinant in their strong immunogenicity. Notably, lentiviral vectors can be engineered to target antigen expression to specific host cells. The very weak inflammatory properties of these vectors allow their use in mucosal vaccination, with particular interest in infectious diseases that affect the lungs or brain, including COVID-19. Recent results in various preclinical models have reinforced the interest of these vectors in prophylaxis against infectious diseases and in onco-immunotherapy.

An Ultrastable Virus-Like Particle with a Carbon Dot Core and Expanded Sequence Plasticity

Ordered bio-inorganic hybridization has evolved for the generation of high-performance materials in living organisms and inspires novel strategies to design artificial hybrid materials. Virus-like particles (VLPs) are attracting extensive interest as self-assembling systems and platforms in the fields of biotechnology and nanotechnology. However, as soft nanomaterials, their structural stability remains a general and fundamental problem in various applications. Here, an ultrastable VLP assembled from the major capsid protein (VP1) of simian virus 40 is reported, which contains a carbon dot (C-dot) core. Co-assembly of VP1 with C-dots led to homogeneous T = 1 VLPs with a fourfold increase in VLP yields. The resultant hybrid VLPs showed markedly enhanced structural stability and sequence plasticity. C-dots and a polyhistidine tag fused to the inner-protruding N-terminus of VP1 contributed synergistically to these enhancements, where extensive and strong noncovalent interactions on the C-dot/VP1 interfaces are responsible according to cryo-EM 3D reconstruction, molecular simulation, and affinity measurements. C-dot-enhanced ultrastable VLPs can serve as a new platform, enabling the fabrication of new architectures for bioimaging, theranostics, nanovaccines, etc. The hybridization strategy is simple and can easily be extended to other VLPs and protein nanoparticle systems.

Protein interface redesign facilitates the transformation of nanocage building blocks to 1D and 2D nanomaterials

Although various artificial protein nanoarchitectures have been constructed, controlling the transformation between different protein assemblies has largely been unexplored. Here, we describe an approach to realize the self-assembly transformation of dimeric building blocks by adjusting their geometric arrangement. Thermotoga maritima ferritin (TmFtn) naturally occurs as a dimer; twelve of these dimers interact with each other in a head-to-side manner to generate 24-meric hollow protein nanocage in the presence of Ca²⁺ or PEG. By tuning two contiguous dimeric proteins to interact in a fully or partially side-by-side fashion through protein interface redesign, we can render the self-assembly transformation of such dimeric building blocks from the protein nanocage to filament, nanorod and nanoribbon in response to multiple external stimuli. We show similar dimeric protein building blocks can generate three kinds of protein materials in a manner that highly resembles natural pentamer building blocks from viral capsids that form different protein assemblies.

Analysis of Engineered Tobacco Mosaic Virus and Potato Virus X Nanoparticles as Carriers for Biocatalysts

Plant virus nanoparticles are promising candidates for the development of novel materials, including nanocomposites and scaffolds/carriers for functional molecules such as enzymes. Their advantages for enzyme immobilization include a modular organization, a robust and programmable structure, and a simple, cost-effective production. However, the activity of many enzymes relies on posttranslational modification and most plant viruses replicate in the cytoplasm, so functional enzymes cannot be displayed on the virus surface by direct coat protein fusions. An alternative display system to present the Trichoderma reesei endoglucanase Cel12A on potato virus X (PVX) using SpyTag/SpyCatcher (ST/SC) technology was recently developed by the authors, which allows the carrier and enzyme to be produced separately before isopeptide conjugation. Although kinetic analysis clearly indicated efficient biocatalyst activity, the PVX carrier interfered with substrate binding. To overcome this, the suitability of tobacco mosaic virus (TMV) was tested, which can also accommodate a larger number of ST peptides. We produced TMV particles displaying ST as a new platform for the immobilization of enzymes such as Cel12A, and compared its performance to the established PVX-ST platform in terms of catalytic efficiency. Although more enzyme molecules were immobilized on the TMV-ST particles, we found that the rigid scaffold and helical spacing significantly affected enzyme activity.

Thermal-triggered packing of lipophilic NIR dye IR780 in hepatitis B core at critical ionic strength and cargo-host ratio for improved stability and enhanced cancer phototherapy

Virus-like particles (VLPs) holding internal cavity with diameter from tens up to one hundred nanometers are attractive platform for drug delivery. Nevertheless, the packing of drugs in the nanocage mainly relies on complicated disassembly-reassembly process. In this study, hepatitis B core protein (HBc) VLPs which can withstand temperature up to 90 °C was employed as carrier to load a lipophilic near infrared dye IR780. It was found that an attaching-dis-atching-diffusing process was involved for the entering of IR780 in the cavity of HBc. The first two steps were associated with the electrostatic interactions between oppositely charged HBc and IR780, which was critically manipulated by ionic strength and HBc/IR780 mass ratio at which they were mixed; while the diffusion of IR780 across the shell of HBc showed a temperature-dependent manner that can be triggered by thermal induced pore-opening of the HBc capsid. At optimized condition, about 1055 IR780 molecules were encapsulated in each HBc by simply mixing them for 10 min at 60 °C. Compared with free IR780, the HBc-IR780 particles showed significantly improved aqueous and photostability, as well as enhanced photothermal and photodynamic performance for cancer therapy. This study provides a novel drug loading strategy and nanomemedicine for cancer phototherapies.

New generation of viral nanoparticles for targeted drug delivery in cancer therapy

Nanoscale engineering is one of the novel methods to cure multitudes of diseases, such as types of cancers, neurological disorders, and infectious illnesses. Viruses can play a vital role in nanoscale engineering due to their specific properties like minuscule size, high stability in different body conditions, and large-scale production. Viral-like particles (VLPs) as specific nanoscale scaffolds can encapsulate a wide range of cargos, including nucleic acids, proteins, peptides, and drugs. The Exterior portion of VLPs can be changed by genetical or chemical conjugation as well as targeting ligands or peptides. The aforementioned features of VLPs can be used in several applications, such as drug delivery, bioimaging, tissue engineering, vaccine production, and disease detection. This review article attempts to investigate appearance characteristics, modification strategies, and manufacturing methods of VLPs. Additionally, drug delivery to cancer cells as one of the VLPs applications along with different cellular uptake mechanisms of VLPs by cancer cells are chosen for investigation. This review also tries to gather most of the recent studies of drug delivery to cancer cells by VLPs.

Load and Display: Engineering Encapsulin as a Modular Nanoplatform for Protein-Cargo Encapsulation and Protein-Ligand Decoration Using Split Intein and SpyTag/SpyCatcher

Protein cage nanoparticles have a unique spherical hollow structure that provides a modifiable interior space and an exterior surface. For full application, it is desirable to utilize both the interior space and the exterior surface simultaneously with two different functionalities in a well-combined way. Here, we genetically engineered encapsulin protein cage nanoparticles (Encap) as modular nanoplatforms by introducing a split-C-intein (Int^C) fragment and SpyTag into the interior and exterior surfaces, respectively. A complementary split-N-intein (Int^N) was fused to various protein cargoes, such as NanoLuc luciferase (Nluc), enhanced green fluorescent protein (eGFP), and Nluc-miniSOG, individually, which led to their successful encapsulation into Encaps to form Cargo@Encap through split intein-mediated protein ligation during protein coexpression and cage assembly in bacteria. Conversely, the SpyCatcher protein was fused to various protein ligands, such as a glutathione binder (GST-SC), dimerizing ligands (FKBP12-SC and FRB-SC), and a cancer-targeting affibody (SC-EGFRAfb); subsequently, they were displayed on Cargo@Encaps through SpyTag/SpyCatcher ligation to form Cargo@Encap/Ligands in a mix-and-match manner. Nluc@Encap/glutathione-S-transferase (GST) was effectively immobilized on glutathione (GSH)-coated solid supports exhibiting repetitive and long-term usage of the encapsulated luciferases. We also established luciferase-embedded layer-by-layer (LbL) nanostructures by alternately depositing Nluc@Encap/FKBP12 and Nluc@Encap/FRB in the presence of rapamycin and applied enhanced green fluorescent protein (eGFP)@Encap/EGFRAfb as a target-specific fluorescent imaging probe to visualize specific cancer cells selectively. Modular functionalization of the interior space and the exterior surface of a protein cage nanoparticle may offer the opportunity to develop new protein-based nanostructured devices and nanomedical tools.

Fusogenic Viral Protein-Based Near-Infrared Active Nanocarriers for Biomedical Imaging

An effective drug delivery system (DDS) relies on an efficient cellular uptake and faster intracellular delivery of theranostic agents, bypassing the endosomal mediated degradation of the payload. The use of viral nanoparticles (VNPs) permits such advancement, as the viruses are naturally evolved to infiltrate the host cells to deliver their genetic material. As a proof of concept, we bioengineered the vesicular stomatitis virus glycoprotein (VSV-G)-based near-infrared (NIR) active viral nanoconstructs (NAVNs) encapsulating indocyanine green dye (ICG) for NIR bioimaging. NAVNs are spherical in size and have the intrinsic cellular-fusogenic properties of VSV-G. Further, the NIR imaging displaying higher fluorescence intensity in NAVNs treated cells suggests enhanced cellular uptake and delivery of ICG by NAVNs compared to the free form of ICG. The overall study highlights the effectiveness of VSV-G-based VNPs as an efficient delivery system for NIR fluorescence imaging.

Nanomedicine: A Diagnostic and Therapeutic Approach to COVID-19

The SARS-CoV-2 virus is causing devastating morbidity and mortality worldwide. Nanomedicine approaches have a high potential to enhance conventional diagnostics, drugs and vaccines. In fact, lipid nanoparticle/mRNA vaccines are already widely used to protect from COVID-19. In this review, we present an overview of the taxonomy, structure, variants of concern, epidemiology, pathophysiology and detection methods of SARS-CoV-2. The efforts of repurposing, tailoring, and adapting pre-existing medications to battle COVID-19 and the state of vaccine developments are presented. Next, we discuss the broad concepts and limitations of how nanomedicine could address the COVID-19 threat. Nanomaterials are particles in the nanometer scale (10-100 nm) which possess unique properties related to their size, polarity, structural and chemical composition. Nanoparticles can be composed of precious metals (copper, silver, gold), inorganic materials (graphene, silicon), proteins, carbohydrates, lipids, RNA/DNA, or conjugates, combinations and polymers of all of the aforementioned. The advanced biochemical features of these nanoscale particles allow them to directly interact with virions and irreversibly disrupt their structure, which can render a virus incapable of replicating within the host. Virus-neutralizing coats and surfaces impregnated with nanomaterials can enhance personal protective equipment, hand sanitizers and air filter systems. Nanoparticles can enhance drug-based therapies by optimizing uptake, stability, target cell-specific delivery, and magnetic properties. In fact, recent studies have highlighted the potential of nanoparticles in different aspects of the fight against SARS-CoV-2, such as enhancing biosensors and diagnostic tests, drug therapies, designing new delivery mechanisms, and optimizing vaccines. This article summarizes the ongoing research on diagnostic strategies, treatments, and vaccines for COVID-19, while emphasizing the potential of nanoparticle-based pharmaceuticals and vaccines.

Designing S100A9-Targeted Plant Virus Nanoparticles to Target Deep Vein Thrombosis

Thromboembolic conditions are a leading cause of death worldwide, and deep vein thrombosis (DVT), or occlusive venous clot formation, is a critical and rising problem that contributes to damage of vital organs, long-term complications, and life-threatening conditions such as pulmonary embolism. Early diagnosis and treatment are correlated to better prognosis. However, current technologies in these areas, such as ultrasonography for diagnostics and anticoagulants for treatment, are limited in terms of their accuracy and therapeutic windows. In this work, we investigated targeting myeloid related protein 14 (MRP-14, also known as S100A9) using plant virus-based nanoparticle carriers as a means to achieve tissue specificity aiding prognosis and therapeutic intervention. We used a combinatorial peptide library screen to identify peptide ligands that bind MRP-14. Candidates were selected and formulated as nanoparticles by using cowpea mosaic virus (CPMV) and tobacco mosaic virus (TMV). Intravascular delivery of our MRP-14-targeted nanoparticles in a murine model of DVT resulted in enhanced accumulation in the thrombi and reduced thrombus size, suggesting application of nanoparticles for molecular targeting of MRP-14 could be a promising direction for improving DVT diagnostics, therapeutics, and therefore prognosis.

Polymer Coatings on Virus-like Particle Nanoreactors at Low Ionic Strength-Charge Reversal and Substrate Access

Virus-like particles (VLPs) are a class of biomaterials which serve as platforms for achieving the desired functionality through interior and exterior modifications. Through ionic strength-mediated electrostatic interactions, VLPs have been assembled into hierarchically ordered materials. This work builds on predictive models to prepare polymer-coated VLP clusters at very low ionic strength. Zeta potential measurements showed that the clusters carried a strongly positive charge, a complete charge reversal from the VLP building block. SAXS analysis confirmed polymer adsorption onto the VLP exterior. We then studied the activity of an encapsulated enzyme toward small molecular and macromolecular substrates to determine the effect of each component of the hierarchically assembled material. We found that while encapsulation and polymer coating did not have a large effect on access to the enzyme by its native, small molecular substrate, substrate modification with a macromolecule caused the polymer coating and encapsulation to affect the access to the enzyme.

Fluorescence Correlation Spectroscopy Analysis of Effect of Molecular Crowding on Self-Assembly of β-Annulus Peptide into Artificial Viral Capsid

Recent progress in the de novo design of self-assembling peptides has enabled the construction of peptide-based viral capsids. Previously, we demonstrated that 24-mer β-annulus peptides from tomato bushy stunt virus spontaneously self-assemble into an artificial viral capsid. Here we propose to use the artificial viral capsid through the self-assembly of β-annulus peptide as a simple model to analyze the effect of molecular crowding environment on the formation process of viral capsid. Artificial viral capsids formed by co-assembly of fluorescent-labelled and unmodified β-annulus peptides in dilute aqueous solutions and under molecular crowding conditions were analyzed using fluorescence correlation spectroscopy (FCS). The apparent particle size and the dissociation constant (K_d) of the assemblies decreased with increasing concentration of the molecular crowding agent, i.e., polyethylene glycol (PEG). This is the first successful in situ analysis of self-assembling process of artificial viral capsid under molecular crowding conditions.

Synthesis and Photobehavior of a NewDehydrobenzoannulene-Based HOF with Fluorine Atoms: From Solution to Single Crystals Observation

Hydrogen-bonded organic frameworks (HOFs) are the focus of intense scientific research due their potential applications in science and technology. Here, we report on the synthesis, characterization, and photobehavior of a new HOF (T12F-1(124TCB)) based on a dehydrobenzoannulene derivative containing fluorine atoms (T12F-COOH). This HOF exhibits a 2D porous sheet, which is hexagonally networked via H-bonds between the carboxylic groups, and has an interlayers distance (4.3 Å) that is longer than that of a typical π–π interaction. The presence of the fluorine atoms in the DBA molecular units largely increases the emission quantum yield in DMF (0.33, T12F-COOH) when compared to the parent compound (0.02, T12-COOH). The time-resolved dynamics of T12F-COOH in DMF is governed by the emission from a locally excited state (S1, ~0.4 ns), a charge-transfer state (S1(CT), ~2 ns), and a room temperature emissive triplet state (T1, ~20 ns), in addition to a non-emissive triplet structure with a charge-transfer character (T1(CT), τ = 0.75 µs). We also report on the results using T12F-ester. Interestingly, FLIM experiments on single crystals unravel that the emission lifetimes of the crystalline HOF are almost twice those of the amorphous ones or the solid T12F-ester sample. This shows the relevance of the H-bonds in the photodynamics of the HOF and provides a strong basis for further development and study of HOFs based on DBAs for potential applications in photonics.

Cargo encapsulated hepatitis E virus-like particles for anti-HEV antibody detection

Viral capsid-nanoparticle hybrid structures incorporating quantum dots (QDs) into virus-like particles (VLPs) constitute an emerging bioinspired type of nanoarchitecture paradigm used for various applications. In the present study, we packed inorganic QDs in vitro into the hepatitis E virus-like particle (HEV-LP) and developed a fluorometric biosensor for HEV antibody detection. Firstly, for the preparation of QDs-encapsulated HEV-LPs (QDs@HEV-LP), the HEV-LPs produced by a recombinant baculovirus expression system were disassembled and reassembled in the presence of QDs using the self-assembly approach. Thus, the prepared QDs@HEV-LP exhibited excellent fluorescence properties similar to QDs. Further, in the presence of HEV antibodies in the serum samples, when mixed with QDs@HEV-LP, bind together and further bind to anti-IgG-conjugated magnetic nanoparticles (MNPs). The target-specific anti-IgG-MNPs and QDs@HEV-LP enrich the HEV antibodies by magnetic separation, and the separated QDs@HEV-LP-bound HEV antibodies are quantified by fluorescence measurement. This developed method was applied to detect the HEV antibody from sera of HEV-infected monkey from 0 to 68 days-post-infection and successfully diagnosed for HEV antibodies. The viral RNA copies number from monkey fecal samples by RT-qPCR was compared to the HEV antibody generation. This study first used QDs-encapsulated VLPs as useful fluorescence emitters for biosensing platform construction. It provides an efficient route for highly sensitive and specific antibody detection in clinical diagnosis research.

Reprogramming Virus Coat Protein Carboxylate Interactions for the Patterned Assembly of Hierarchical Nanorods

The self-assembly system of the rod-shaped tobacco mosaic virus (TMV) has been studied extensively for nanoscale applications. TMV coat protein assembly is modulated by intersubunit carboxylate groups whose electrostatic repulsion limits the assembly of virus rods without incorporating genomic RNA. To engineer assembly control into this system, we reprogrammed intersubunit carboxylate interactions to produce self-assembling coat proteins in the absence of RNA and in response to unique pH and ionic environmental conditions. Specifically, engineering a charge attraction at the intersubunit E50-D77 carboxylate group through a D77K substitution stabilized the coat proteins assembly into virus-like rods. In contrast, the reciprocal E50K modification alone did not confer virus-like rod assembly. However, a combination of R46G/E50K/E97G substitutions enabled virus-like rod assembly. Interestingly, the D77K substitution displays a unique pH-dependent assembly-disassembly profile, while the R46G/E50K/E97G substitutions confer a novel salt concentration dependency for assembly control. In addition, these unique environmentally controlled coat proteins allow for the directed assembly and disassembly of chimeric virus-like rods both in solution and on substrate-attached seed rods. Combined, these findings provide a controllable means to assemble functionally discrete virus-like rods for use in nanotechnology applications.

Efficient construction of a stable linear gene based on a TNA loop modified primer pair for gene delivery

A terminal-closed linear gene with strong exonuclease resistance and serum stability was successfully constructed by polymerase chain reaction (PCR) with an α-l-threose nucleic acid (TNA) loop modified primer pair, which can be used as an efficient gene expression system in eukaryotic cells for gene delivery.

A Photoresponsive Artificial Viral Capsid Self-Assembled from an Azobenzene-Containing β-Annulus Peptide

Photoinduced structural changes in peptides can dynamically control the formation and dissociation of supramolecular peptide materials. However, the existence of photoresponsive viral capsids in nature remains unknown. In this study, we constructed an artificial viral capsid possessing a photochromic azobenzene moiety on the peptide backbone. An azobenzene-containing β-annulus peptide derived from the tomato bushy stunt virus was prepared through solid-phase synthesis using Fmoc-3-[(3-aminomethyl)-phenylazo]phenylacetic acid. The azobenzene-containing β-annulus (β-Annulus-Azo) peptide showed a reversible trans/cis isomerization property. The β-annulus-azo peptide self-assembled at 25 μM into capsids with the diameters of 30–50 nm before UV irradiation (trans-form rich), whereas micrometer-sized aggregates were formed after UV irradiation (cis-form rich). The artificial viral capsid possessing azobenzene facilitated the encapsulation of fluorescent-labeled dextrans and their photoinduced release from the capsid.

Microparticles and Nanoparticles from Plants-The Benefits of Bioencapsulation

The efficacy of drugs and vaccines depends on their stability and ability to interact with their targets in vivo. Many drugs benefit from encapsulation, which protects them from harsh conditions and allows targeted delivery and controlled release. Although many encapsulation methods are inexpensive, such as the formulation of tablets for oral delivery, others require complex procedures that add significantly to production costs and require low-temperature transport and storage, making them inaccessible in developing countries. In this review we consider the benefits of encapsulation technologies based on plants. Plant-derived biopolymers such as starch and the maize storage protein zein are already used as protective coatings, but plant cells used as production host provide natural in vivo bioencapsulation that survives passage through the stomach and releases drugs in the intestine, due to the presence of microbes that can digest the cell wall. Proteins can also be encapsulated in subcellular compartments such as protein bodies, which ensure stability and activity while often conferring additional immunomodulatory effects. Finally, we consider the incorporation of drugs and vaccines into plant-derived nanoparticles assembled from the components of viruses. These are extremely versatile, allowing the display of epitopes and targeting peptides as well as carrying cargoes of drugs and imaging molecules.

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.

Virus-Like Particles Produced Using the Brome Mosaic Virus Recombinant Capsid Protein Expressed in a Bacterial System

Virus-like particles (VLPs), due to their nanoscale dimensions, presence of interior cavities, self-organization abilities and responsiveness to environmental changes, are of interest in the field of nanotechnology. Nevertheless, comprehensive knowledge of VLP self-assembly principles is incomplete. VLP formation is governed by two types of interactions: protein–cargo and protein–protein. These interactions can be modulated by the physicochemical properties of the surroundings. Here, we used brome mosaic virus (BMV) capsid protein produced in an E. coli expression system to study the impact of ionic strength, pH and encapsulated cargo on the assembly of VLPs and their features. We showed that empty VLP assembly strongly depends on pH whereas ionic strength of the buffer plays secondary but significant role. Comparison of VLPs containing tRNA and polystyrene sulfonic acid (PSS) revealed that the structured tRNA profoundly increases VLPs stability. We also designed and produced mutated BMV capsid proteins that formed VLPs showing altered diameters and stability compared to VLPs composed of unmodified proteins. We also observed that VLPs containing unstructured polyelectrolyte (PSS) adopt compact but not necessarily more stable structures. Thus, our methodology of VLP production allows for obtaining different VLP variants and their adjustment to the incorporated cargo.

De Novo Designed Peptide and Protein Hairpins Self-Assemble into Sheets and Nanoparticles

The design and assembly of peptide-based materials has advanced considerably, leading to a variety of fibrous, sheet, and nanoparticle structures. A remaining challenge is to account for and control different possible supramolecular outcomes accessible to the same or similar peptide building blocks. Here a de novo peptide system is presented that forms nanoparticles or sheets depending on the strategic placement of a "disulfide pin" between two elements of secondary structure that drive self-assembly. Specifically, homodimerizing and homotrimerizing de novo coiled-coil α-helices are joined with a flexible linker to generate a series of linear peptides. The helices are pinned back-to-back, constraining them as hairpins by a disulfide bond placed either proximal or distal to the linker. Computational modeling indicates, and advanced microscopy shows, that the proximally pinned hairpins self-assemble into nanoparticles, whereas the distally pinned constructs form sheets. These peptides can be made synthetically or recombinantly to allow both chemical modifications and the introduction of whole protein cargoes as required.

P22 virus-like particles as an effective antigen delivery nanoplatform for cancer immunotherapy

As a new strategy for cancer immunotherapy, therapeutic cancer vaccines have been greatly improved in recent years. However, addressing the needs to quickly and efficiently elicit a high-intensity immune response against neoantigen peptides, especially to induce an effective cytotoxic lymphocyte (CTL) reaction, remain challenges in this field. In this study, virus-like particles (VLPs) derived from the phage P22 were adopted to load peptide antigens on the surface, to test whether VLP technology can be used as a platform for efficient peptide antigen delivery by therapeutic cancer vaccines. The B and T epitopes (OVA_B peptide and OVA_T peptide) of ovalbumin (OVA) were used here as model antigens and fused individually at the C terminus of the coat protein (CP), which allowed display on the surface of P22 particles to form two types of vaccine particles (VLP-OVA_B and VLP-OVA_T). Subsequent experiments showed that VLP-OVA_B induced an antibody titer against the peptide antigen as high as 5.0 × 10⁵ and that VLP-OVA_T induced highly effective cross-presentation and then strongly activated a T epitope-specific CTL response. Mouse tumor model experiments showed that VLP-OVA_T could significantly inhibit tumor growth by increasing the proportions of CD4⁺ T cells, CD8⁺ T cells and effector memory T cells (T_EM cells) and lowering the proportion of myeloid-derived suppressor cells (MDSCs) among tumor-infiltrating lymphocytes and splenocytes. Compared with other chemically synthesized nanomaterials, VLPs have obvious advantages as vaccine carriers due to their clear chemical composition, fixed spatial structure, excellent biocompatibility, and relatively high potential for clinical translation. Therefore, this platform may lay a solid foundation for the design and preparation of personalized therapeutic vaccines based on neoantigen peptides.

Synthesis of New Naphthyl Aceto Hydrazone-Based Metal Complexes: Micellar Interactions, DNA Binding, Antimicrobial, and Cancer Inhibition Studies

In the present study, naphthyl acetohydrazide (HL) ligand was prepared and used for the synthesis of new six amorphous transition metal (Co(II), Ni(II), Cu(II), Zn(II), Pb(II), Cd(II)) complexes. All the compounds were characterized by elemental analysis, UV-vis, FT-IR, ¹H- and ¹³C-NMR, and Matrix-Assisted Laser Desorption Ionization (MALDI). The solubilization study was carried out by estimating the interaction between the metal complexes with surfactants viz. sodium stearate (SS) and Cetyltrimethylammonium bromide (CTAB). UV-Visible spectroscopy was employed to determine partitioning and binding parameters, whereas electrical conductivity measurements were employed to estimate critical micellar concentration (CMC), the extent of dissociation, and free energy of micellization. The CT-DNA interaction of synthesized compounds with DNA represents the major groove binding. The synthesized ligand and metal complexes were also tested against bacterial and fungal strains and it has been observed that Cu(II) complex is active against all the strains except Candida albicans, while Cd(II) complex is active against all bacterial and fungal strains except Pseudomonas. Among all compounds, only the Pd(II) complex shows reasonable activity against cervical cancer HeLa cell lines, representing 97% inhibition.

Recent Advances in Bio-Templated Metallic Nanomaterial Synthesis and Electrocatalytic Applications

Developing metallic nanocatalysts with high reaction activity, selectivity and practical durability is a promising and active subfield in electrocatalysis. In the classical "bottom-up" approach to synthesize stable nanomaterials by chemical reduction, stabilizing additives such as polymers or organic surfactants must be present to cap the nanoparticle to prevent material bulk aggregation. In recent years, biological systems have emerged as green alternatives to support the uncoated inorganic components. One key advantage of biological templates is their inherent ability to produce nanostructures with controllable composition, facet, size and morphology under ecologically friendly synthetic conditions, which are difficult to achieve with traditional inorganic synthesis. In addition, through genetic engineering or bioconjugation, bio-templates can provide numerous possibilities for surface functionalization to incorporate specific binding sites for the target metals. Therefore, in bio-templated systems, the electrocatalytic performance of the formed nanocatalyst can be tuned by precisely controlling the material surface chemistry. With controlled improvements in size, morphology, facet exposure, surface area and electron conductivity, bio-inspired nanomaterials often exhibit enhanced catalytic activity towards electrode reactions. In this Review, recent research developments are presented in bio-approaches for metallic nanomaterial synthesis and their applications in electrocatalysis for sustainable energy storage and conversion systems.

Nano-targeting lessons from the SARS-CoV-2

The lack of targeting efficacy has frequently led functionalized nanoparticles to accumulate in unwanted cells and tissues while boosting toxicity-related effects. Conversely, viruses are natural nanoparticles that precisely and responsively interact with the biological machinery through an effective-driven fashion. This interaction is enhanced by a meticulous spatial arrangement which results in a quasi-crystalline distribution of proteins on the viruses' surface. Amidst the COVID-19 pandemic, we propose to look at the SARS-CoV-2 nanoscale viral scaffold as an example of a highly-ordered architecture that must inspire and tailor the production of targeted synthetic nanoparticles.

Biomimetic Virus-Like Particles as Severe Acute Respiratory Syndrome Coronavirus 2 Diagnostic Tools

Coronavirus disease 2019 (COVID-19) is a highly transmissible disease that has affected more than 90% of the countries worldwide. At least 17 million individuals have been infected, and some countries are still battling first or second waves of the pandemic. Nucleic acid tests, especially reverse transcription polymerase chain reaction (RT-PCR), have become the workhorse for early detection of COVID-19 infection. Positive controls for the molecular assays have been developed to validate each test and to provide high accuracy. However, most available positive controls require cold-chain distribution and cannot serve as full-process control. To overcome these shortcomings, we report the production of biomimetic virus-like particles (VLPs) as SARS-CoV-2 positive controls. A SARS-CoV-2 detection module for RT-PCR was encapsidated into VLPs from a bacteriophage and a plant virus. The chimeric VLPs were obtained either by in vivo reconstitution and coexpression of the target detection module and coat proteins or by in vitro assembly of purified detection module RNA sequences and coat proteins. These VLP-based positive controls mimic SARS-CoV-2 packaged ribonucleic acid (RNA) while being noninfectious. Most importantly, we demonstrated that the positive controls are scalable, stable, and can serve broadly as controls, from RNA extraction to PCR in clinical settings.

Asymmetrizing an icosahedral virus capsid by hierarchical assembly of subunits with designed asymmetry

Symmetrical protein complexes are ubiquitous in biology. Many have been re-engineered for chemical and medical applications. Viral capsids and their assembly are frequent platforms for these investigations. A means to create asymmetric capsids may expand applications. Here, starting with homodimeric Hepatitis B Virus capsid protein, we develop a heterodimer, design a hierarchical assembly pathway, and produce asymmetric capsids. In the heterodimer, the two halves have different growth potentials and assemble into hexamers. These preformed hexamers can nucleate co-assembly with other dimers, leading to Janus-like capsids with a small discrete hexamer patch. We can remove the patch specifically and observe asymmetric holey capsids by cryo-EM reconstruction. The resulting hole in the surface can be refilled with fluorescently labeled dimers to regenerate an intact capsid. In this study, we show how an asymmetric subunit can be used to generate an asymmetric particle, creating the potential for a capsid with different surface chemistries.

Smart materials-integrated sensor technologies for COVID-19 diagnosis

After the first case has appeared in China, the COVID-19 pandemic continues to pose an omnipresent threat to global health, affecting more than 70 million patients and leading to around 1.6 million deaths. To implement rapid and effective clinical management, early diagnosis is the mainstay. Today, real-time reverse transcriptase (RT)-PCR test is the major diagnostic practice as a gold standard method for accurate diagnosis of this disease. On the other side, serological assays are easy to be implemented for the disease screening. Considering the limitations of today's tests including lengthy assay time, cost, the need for skilled personnel, and specialized infrastructure, both strategies, however, have impediments to be applied to the resource-scarce settings. Therefore, there is an urgent need to democratize all these practices to be applicable across the globe, specifically to the locations comprising of very limited infrastructure. In this regard, sensor systems have been utilized in clinical diagnostics largely, holding great potential to have pivotal roles as an alternative or complementary options to these current tests, providing crucial fashions such as being suitable for point-of-care settings, cost-effective, and having short turnover time. In particular, the integration of smart materials into sensor technologies leverages their analytical performances, including sensitivity, linear dynamic range, and specificity. Herein, we comprehensively review major smart materials such as nanomaterials, photosensitive materials, electrically sensitive materials, their integration with sensor platforms, and applications as wearable tools within the scope of the COVID-19 diagnosis.

Capacitive Field-Effect Biosensor Studying Adsorption of Tobacco Mosaic Virus Particles

Plant virus-like particles, and in particular, tobacco mosaic virus (TMV) particles, are increasingly being used in nano- and biotechnology as well as for biochemical sensing purposes as nanoscaffolds for the high-density immobilization of receptor molecules. The sensitive parameters of TMV-assisted biosensors depend, among others, on the density of adsorbed TMV particles on the sensor surface, which is affected by both the adsorption conditions and surface properties of the sensor. In this work, Ta₂O₅-gate field-effect capacitive sensors have been applied for the label-free electrical detection of TMV adsorption. The impact of the TMV concentration on both the sensor signal and the density of TMV particles adsorbed onto the Ta₂O₅-gate surface has been studied systematically by means of field-effect and scanning electron microscopy methods. In addition, the surface density of TMV particles loaded under different incubation times has been investigated. Finally, the field-effect sensor also demonstrates the label-free detection of penicillinase immobilization as model bioreceptor on TMV particles.

Biomechanical Features of Graphene-Augmented Inorganic Nanofibrous Scaffolds and Their Physical Interaction with Viruses

Nanofibrous substrates and scaffolds are widely being studied as matrices for 3D cell cultures, and disease models as well as for analytics and diagnostic purposes. These scaffolds usually comprise randomly oriented fibers. Much less common are nanofibrous scaffolds made of stiff inorganic materials such as alumina. Well-aligned matrices are a promising tool for evaluation of behavior of biological objects affected by micro/nano-topologies as well as anisotropy. In this work, for the first time, we report a joint analysis of biomechanical properties of new ultra-anisotropic, self-aligned ceramic nanofibers augmented with two modifications of graphene shells (GAIN scaffolds) and their interaction of three different viral types (influenza virus A, picornavirus (human parechovirus) and potato virus). It was discovered that nano-topology and structure of the graphene layers have a significant implication on mechanical properties of GAIN scaffolds resulting in non-linear behavior. It was demonstrated that the viral adhesion to GAIN scaffolds is likely to be guided by physical cues in dependence on mutual steric factors, as the scaffolds lack common cell membrane proteins and receptors which viruses usually deploy for transfection. The study may have implications for selective viral adsorption, infected cells analysis, and potentially opening new tools for anti-viral drugs development.

One-dimensional micro/nanomotors for biomedicine: delivery, sensing and surgery

The rapid development of artificial micro/nanomachines brings promising strategies to overcome challenges in biomedicine, including delivery, sensing and surgery. One-dimensional (1D) micro/nanomotors are one of the most attractive micro/nanomachines due to their high specific surface area, powerful impetus and weak rotation diffusion. In this review, different propulsion mechanisms and motion control strategies of 1D micro/nanomotors are summarized, and recent efforts towards their fabrication methods and biomedical applications are discussed. We envision the multidisciplinary research efforts in the field of 1D micro/nanomotors will pave their way to practical applications in bioimaging and biomedicine.

Doxorubicin-Loaded Physalis Mottle Virus Particles Function as a pH-Responsive Prodrug Enabling Cancer Therapy

The controlled release of drugs using nanoparticle-based delivery vehicles is a promising strategy to improve the safety and efficacy of chemotherapy. A simple, scalable, and reproducible strategy is developed to synthesize a drug delivery system (DDS) by loading 6-maleimidocaproyl-hydrazone doxorubicin (DOX-EMCH) into the empty core of virus-like particles (VLPs) derived from Physalis mottle virus (PhMV) via a combination of chemical conjugation to cysteine residues and π-π stacking interactions with the anchored doxorubicin molecule. The DOX-EMCH prodrug features an acid-sensitive hydrazine linker that triggers the release of doxorubicin in the slightly acidic extracellular tumor microenvironment or acidic endosomal or lysosomal compartments following cellular uptake. The VLP external surface is coated with polyethylene glycol (PEG) to prevent non-specific uptake and improve biocompatibility. The DOX-PhMV-PEG particles are stable in vitro and show greater efficacy in vivo compared to free doxorubicin in a breast tumor mouse model (using MDA-MB-231 cells and nude mice): 92% of the tumor-bearing mice treated with DOX-PhMV-PEG are completely cured compared to 27% of those treated with free doxorubicin under the same conditions, representing a 3.4-fold improvement. These results lay a foundation for the further development of this biological drug delivery system for a new generation of chemotherapy products.

Antiviral nanoagents: More attention and effort needed?

The recent COVID-19 outbreak has increasingly engaged researchers in the search for effective antiviral drugs as well as therapeutic treatment options. The shortcomings of existing antiviral agents such as narrow spectrum and low bioavailability, can be overcome through the use of engineered nanomaterials, which, therefore, are considered as a significant next-generation therapeutic option. Thus, the development of novel antiviral nanoagents will certainly help address several future challenges and knowledge gaps.

Analysis of the virome associated to grapevine downy mildew lesions reveals new mycovirus lineages

The obligatory biotrophic oomycetes Plasmopara viticola is the causal agent of downy mildew, a destructive disease of grapevine worldwide. So far, chemical fungicides are widely employed to limit this pathogen, but their adverse effects are stimulating the quest for environmentally friendly alternative approaches. Here, we report on the search for mycoviruses that might be later developed as biocontrol agents for this pathogen. Symptomatic leaves were collected from various regions in Spain and Italy and mycelia associated to leaf lesions was harvested. Total RNA extractions were depleted of rRNA and metatranscriptomes were generated using a high-throughput sequencing approach. The virome associated to leaf lesions was then characterized through a bioinformatic pipeline relying on blast searches against current viral databases. Here, we present an inventory of 283 new RNA viruses: 222 positive strand RNA viruses, 29 negative strand RNA viruses, 27 double-stranded RNA viruses and 5 ORFan virus RdRP segments, which could not be reliably assigned to any existing group in the Riboviria. In addition to ORFan viruses, we found other surprising new evolutionary trajectories in this wide inventory of viruses. The most represented viruses in our collection are those in phylum Lenarviricota, and, among them, a group of mycovirus segments distantly related to narnaviruses, but characterized by a polymerase palm domain lacking subdomain C, with the putative GDD catalytic triad. We also provided evidence of a strict association between two RNA segments that form a new mycovirus clade of positive strand RNA in the phylum Kitrinoviricota, order Martellivirales. In the phylum Negarnaviricota, we report for the first time in the order Mononegavirales a clade of viruses that is ambisense, a feature that so far was present only in the order Bunyavirales. Furthermore, in the same phylum we detected the widespread occurrence and abundant accumulation in our libraries of a distinct mycovirus clade distantly related to the Muvirales and Goujanvirales orders, which so far include only viruses infecting invertebrates. Possible new oomycetes-specific virus clades are also described in the phylum Duplornaviricota. These data greatly expand the evolutionary history of mycoviruses adding new layers of diversity to the realm Riboviria.

Branched Antisense and siRNA Co-Assembled Nanoplatform for Combined Gene Silencing and Tumor Therapy

Chemically modified DNA has been widely developed to fabricate various nucleic acid nanostructures for biomedical applications. Herein, we report a facile strategy for construction of branched antisense DNA and small interfering RNA (siRNA) co-assembled nanoplatform for combined gene silencing in vitro and in vivo. In our design, the branched antisense can efficiently capture siRNA with 3' overhangs through DNA-RNA hybridization. After being equipped with an active targeting group and an endosomal escape peptide by host-guest interaction, the tailored nucleic acid nanostructure functions efficiently as both delivery carrier and therapeutic cargo, which is released by endogenous RNase H digestion. The multifunctional nucleic acid nanosystem elicits an efficient inhibition of tumor growth based on the combined gene silencing of the tumor-associated gene polo-like kinase 1 (PLK1). This biocompatible nucleic acid nanoplatform presents a new strategy for the development of gene therapy.

Horseradish Peroxidase-Decorated Artificial Viral Capsid Constructed from β-Annulus Peptide via Interaction between His-Tag and Ni-NTA

Artificial construction of spherical protein assemblies has attracted considerable attention due to its potential use in nanocontainers, nanocarriers, and nanoreactors. In this work, we demonstrate a novel strategy to construct peptide nanocapsules (artificial viral capsids) decorated with enzymes via interactions between His-tag and Ni-NTA. A β-annulus peptide derived from the tomato bushy stunt virus was modified with Ni-NTA at the C-terminus, which is directed toward the exterior surface of the artificial viral capsid. The β-annulus peptide bearing Ni-NTA at the C-terminus self-assembled into capsids of about 50 nm in diameter. The Ni-NTA-displayed capsids were complexed with recombinant horseradish peroxidase (HRP) with a C-terminal His-tag which was expressed in Escherichia coli. The β-annulus peptide-HRP complex formed spherical assemblies whose sizes were 30–90 nm, with the ζ-potential revealing that the HRP was decorated on the outer surface of the capsid.

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.