Delivery of siRNA therapeutics using cowpea chlorotic mottle virus-like particles

Molecular Engineering of Functional SiRNA Agents

Synthetic biology constitutes a scientific domain focused on intentional redesign of organisms to confer novel functionalities or create new products through strategic engineering of their genetic makeup. Leveraging the inherent capabilities of nature, one may address challenges across diverse sectors including medicine. Inspired by this concept, we have developed an innovative bioengineering platform, enabling high-yield and large-scale production of biological small interfering RNA (BioRNA/siRNA) agents via bacterial fermentation. Herein, we show that with the use of a new tRNA fused pre-miRNA carrier, we can produce various forms of BioRNA/siRNA agents within living host cells. We report a high-level overexpression of nine target BioRNA/siRNA molecules at 100% success rate, yielding 3-10 mg of BioRNA/siRNA per 0.25 L of bacterial culture with high purity (>98%) and low endotoxin (<5 EU/μg RNA). Furthermore, we demonstrate that three representative BioRNA/siRNAs against GFP, BCL2, and PD-L1 are biologically active and can specifically and efficiently silence their respective targets with the potential to effectively produce downstream antiproliferation effects by PD-L1-siRNA. With these promising results, we aim to advance the field of synthetic biology by offering a novel platform to bioengineer functional siRNA agents for research and drug development.

Plant Virus Nanoparticles Combat Cancer

Plant virus nanoparticles (PVNPs) have garnered considerable interest as a promising nanotechnology approach to combat cancer. Owing to their biocompatibility, stability, and adjustable surface functionality, PVNPs hold tremendous potential for both therapeutic and imaging applications. The versatility of PVNPs is evident from their ability to be tailored to transport a range of therapeutic agents, including chemotherapy drugs, siRNA, and immunomodulators, thereby facilitating targeted delivery to the tumor microenvironment (TME). Furthermore, PVNPs may be customized with targeting ligands to selectively bind to cancer cell receptors, reducing off-target effects. Additionally, PVNPs possess immunogenic properties and can be engineered to exhibit tumor-associated antigens, thereby stimulating anti-tumor immune responses. In conclusion, the potential of PVNPs as a versatile platform for fighting cancer is immense, and further research is required to fully explore their potential and translate them into clinical applications.

Tailoring the Inherent Properties of Biobased Nanoparticles for Nanomedicine

Biobased nanoparticles are at the leading edge of the rapidly developing field of nanomedicine and biotherapeutics. Their unique size, shape, and biophysical properties make them attractive tools for biomedical research, including vaccination, targeted drug delivery, and immune therapy. These nanoparticles are engineered to present native cell receptors and proteins on their surfaces, providing a biomimicking camouflage for therapeutic cargo to evade rapid degradation, immune rejection, inflammation, and clearance. Despite showing promising clinical relevance, commercial implementation of these biobased nanoparticles is yet to be fully realized. In this perspective, we discuss advanced biobased nanoparticle designs used in medical applications, such as cell membrane nanoparticles, exosomes, and synthetic lipid-derived nanoparticles, and highlight their benefits and potential challenges. Moreover, we critically assess the future of preparing such particles using artificial intelligence and machine learning. These advanced computational tools will be able to predict the functional composition and behavior of the proteins and cell receptors present on the nanoparticle surfaces. With more advancement in designing new biobased nanoparticles, this field of research could play a key role in dictating the future rational design of drug transporters, thereby ultimately improving overall therapeutic outcomes.

Nanostructures for prevention, diagnosis, and treatment of viral respiratory infections: from influenza virus to SARS-CoV-2 variants

Viruses are a major cause of mortality and socio-economic downfall despite the plethora of biopharmaceuticals designed for their eradication. Conventional antiviral therapies are often ineffective. Live-attenuated vaccines can pose a safety risk due to the possibility of pathogen reversion, whereas inactivated viral vaccines and subunit vaccines do not generate robust and sustained immune responses. Recent studies have demonstrated the potential of strategies that combine nanotechnology concepts with the diagnosis, prevention, and treatment of viral infectious diseases. The present review provides a comprehensive introduction to the different strains of viruses involved in respiratory diseases and presents an overview of recent advances in the diagnosis and treatment of viral infections based on nanotechnology concepts and applications. Discussions in diagnostic/therapeutic nanotechnology-based approaches will be focused on H1N1 influenza, respiratory syncytial virus, human parainfluenza virus type 3 infections, as well as COVID-19 infections caused by the SARS-CoV-2 virus Delta variant and new emerging Omicron variant.

Bioengineered Bacteriophage-Like Nanoparticles as RNAi Therapeutics to Enhance Radiotherapy against Glioblastomas

Since glioblastomas (GBMs) are radioresistant malignancies and most GBM recurrences occur in radiotherapy, increasing the effectiveness of radiotherapy by gene-silencing has recently attracted attention. However, the difficulty in precisely tuning the composition and RNA loading in nanoparticles leads to batch-to-batch variations of the RNA therapeutics, thus significantly restricting their clinical translation. Here, we bioengineer bacteriophage Qβ particles with a designed broccoli light-up three-way junction (b-3WJ) RNA scaffold (contains two siRNA/miRNA sequences and one light-up aptamer) packaging for the silencing of genes in radioresistant GBM cells. The in vitro results demonstrate that the cleavage of de novo designed b-3WJ RNA by Dicer enzyme can be easily monitored in real-time using fluorescence microscopy, and the TrQβ@b-3WJ_Let-7g^siEGFR successfully knocks down EGFR and IKKα simultaneously and thereby inactivates NF-κB signaling to inhibit DNA repair. Delivery of TrQβ@b-3WJ_Let-7g^siEGFR through convection-enhanced delivery (CED) infusion followed by 2Gy X-ray irradiation demonstrated that the median survival was prolonged to over 60 days compared with the 2Gy X-ray irradiated group (median survival: 31 days). Altogether, the results of this study could be critical for the design of RNAi-based genetic therapeutics, and CED infusion serves as a powerful delivery system for promoting radiotherapy against GBMs without evidence of systemic toxicity.

Self-assembly of a fluorescent virus-like particle for imaging in tissues with high autofluorescence

Virus-like particles (VLPs) are engineered nanoparticles that mimic the properties of viruses-like high tolerance to heat and proteases-but lack a viral genome, making them non-infectious. They are easily modified chemically and genetically, making them useful in drug delivery, enhancing vaccine efficacy, gene delivery, and cancer immunotherapy. One such VLP is Qβ, which has an affinity towards an RNA hairpin structure found in its viral RNA that drives the self-assembly of the capsid. It is possible to usurp the native way infectious Qβ self-assembles to encapsidate its RNA to place enzymes inside the VLP's lumen as a protease-resistant cage. Further, using RNA templates that mimic the natural self-assembly of the native capsid, fluorescent proteins (FPs) have been placed inside VLPs in a "one pot" expression system. Autofluorescence in tissues can lead to misinterpretation of results and unreliable science, so we created a single-pot expression system that uses the fluorescent protein smURFP, which avoids autofluorescence and has spectral properties compatible with standard commercial filter sets on confocal microscopes. In this work, we were able to simplify the existing "one-pot" expression system while creating high-yielding fluorescent VLP nanoparticles that could easily be imaged inside lung epithelial tissue.

Efficient Purification of Cowpea Chlorotic Mottle Virus by a Novel Peptide Aptamer

The cowpea chlorotic mottle virus (CCMV) is a plant virus explored as a nanotechnological platform. The robust self-assembly mechanism of its capsid protein allows for drug encapsulation and targeted delivery. Additionally, the capsid nanoparticle can be used as a programmable platform to display different molecular moieties. In view of future applications, efficient production and purification of plant viruses are key steps. In established protocols, the need for ultracentrifugation is a significant limitation due to cost, difficult scalability, and safety issues. In addition, the purity of the final virus isolate often remains unclear. Here, an advanced protocol for the purification of the CCMV from infected plant tissue was developed, focusing on efficiency, economy, and final purity. The protocol involves precipitation with PEG 8000, followed by affinity extraction using a novel peptide aptamer. The efficiency of the protocol was validated using size exclusion chromatography, MALDI-TOF mass spectrometry, reversed-phase HPLC, and sandwich immunoassay. Furthermore, it was demonstrated that the final eluate of the affinity column is of exceptional purity (98.4%) determined by HPLC and detection at 220 nm. The scale-up of our proposed method seems to be straightforward, which opens the way to the large-scale production of such nanomaterials. This highly improved protocol may facilitate the use and implementation of plant viruses as nanotechnological platforms for in vitro and in vivo applications.

A co-formulated vaccine of irradiated cancer cells and cowpea mosaic virus improves ovarian cancer rejection

Ovarian cancer ranks fifth in cancer deaths amongst women, and most patients are diagnosed with late-stage and disseminated diseases. Surgical debulking and chemotherapy remove most of the tumor burden and provide a short period of remission; however, most patients experience cancer relapse and eventually succumb to the disease. Therefore, there is an urgent need for the development of vaccines to prime anti-tumor immunity and prevent its recurrence. Here we developed vaccine formulations composed of a mixture of irradiated cancer cells (ICCs, providing the antigen) and cowpea mosaic virus (CPMV) adjuvants. More specifically we compared the efficacy of co-formulated vs. mixtures of ICCs and CPMV. Specifically, we compared co-formulations where the ICCs and CPMV are bonded through natural CPMV-cell interactions or chemical coupling vs. mixtures of PEGylated CPMV and ICCs, where PEGylation of CPMV prevents ICC interactions. Flow cytometry and confocal imaging provided insights into the composition of the vaccines and their efficacy was tested using a mouse model of disseminated ovarian cancer. 67% of the mice receiving the co-formulated CPMV-ICCs survived the initial tumor challenge, and 60% of the surviving mice rejected tumors in a re-challenge experiment. In stark contrast, simple mixtures of the ICCs and (PEGylated) CPMV adjuvants were ineffective. Overall, this study highlights the importance of the co-delivery of cancer antigens and adjuvants in ovarian cancer vaccine development.

microRNA-181a silencing by antisense oligonucleotides delivered by virus-like particles

Cowpea chlorotic mottle virus (CCMV) is a positive-sense RNA virus that can be repurposed for gene delivery applications. Understanding the self-assembly process of the virus enabled to remove its genome and replace it with desired nucleic acids, and we and others have previously reported using CCMV virus-like particle (VLP) to encapsulate siRNA, mRNA, as well as CpG oligodeoxynucleotides. In this study, the CCMV VLP was applied to encapsulate two different formats of anti-miR-181a oligonucleotides: naked RNA and chemically stabilized RNA to knockdown highly regulated miR-181a in ovarian cancer cells. miR-181a expression in ovarian tumors is associated with high aggressiveness, invasiveness, resistance to chemotherapy, and overall poor prognosis. Therefore, miR-181a is an important target for ovarian cancer therapy. qPCR data and cancer cell migration assays demonstrated higher knockdown efficacy when anti-miR-181a oligonucleotides were encapsulated and delivered using the VLPs resulting in reduced cancer cell invasiveness. Importantly, delivery of anti-miR-181a oligonucleotide into cells could be achieved without the aid of a transfection agent or surface modification. These results highlight the opportunity of plant-derived VLPs as nucleic acid carriers.

The Plant Viruses and Molecular Farming: How Beneficial They Might Be for Human and Animal Health?

Plant viruses have traditionally been studied as pathogens in the context of understanding the molecular and cellular mechanisms of a particular disease affecting crops. In recent years, viruses have emerged as a new alternative for producing biological nanomaterials and chimeric vaccines. Plant viruses were also used to generate highly efficient expression vectors, revolutionizing plant molecular farming (PMF). Several biological products, including recombinant vaccines, monoclonal antibodies, diagnostic reagents, and other pharmaceutical products produced in plants, have passed their clinical trials and are in their market implementation stage. PMF offers opportunities for fast, adaptive, and low-cost technology to meet ever-growing and critical global health needs. In this review, we summarized the advancements in the virus-like particles-based (VLPs-based) nanotechnologies and the role they played in the production of advanced vaccines, drugs, diagnostic bio-nanomaterials, and other bioactive cargos. We also highlighted various applications and advantages plant-produced vaccines have and their relevance for treating human and animal illnesses. Furthermore, we summarized the plant-based biologics that have passed through clinical trials, the unique challenges they faced, and the challenges they will face to qualify, become available, and succeed on the market.

Virus-like nanoparticles as a theranostic platform for cancer

Virus-like nanoparticles (VLPs) are natural polymer-based nanomaterials that mimic viral structures through the hierarchical assembly of viral coat proteins, while lacking viral genomes. VLPs have received enormous attention in a wide range of nanotechnology-based medical diagnostics and therapies, including cancer therapy, imaging, and theranostics. VLPs are biocompatible and biodegradable and have a uniform structure and controllable assembly. They can encapsulate a wide range of therapeutic and diagnostic agents, and can be genetically or chemically modified. These properties have led to sophisticated multifunctional theranostic platforms. This article reviews the current progress in developing and applying engineered VLPs for molecular imaging, drug delivery, and multifunctional theranostics in cancer research.

Self-Adaptive Antibacterial Scaffold with Programmed Delivery of Osteogenic Peptide and Lysozyme for Infected Bone Defect Treatment

Bone defects caused by disease or trauma are often accompanied by infection, which severely disrupts the normal function of bone tissue at the defect site. Biomaterials that can simultaneously reduce inflammation and promote osteogenesis are effective tools for addressing this problem. In this study, we set up a programmed delivery platform based on a chitosan scaffold to enhance its osteogenic activity and prevent implant-related infections. In brief, the osteogenic peptide sequence (YGFGG) was modified onto the surface of cowpea chlorotic mottle virus (CCMV) to form CCMV-YGFGG nanoparticles. CCMV-YGFGG exhibited good biocompatibility and osteogenic ability in vitro. Then, CCMV-YGFGG and lysozyme were loaded on the chitosan scaffold, which exhibited a good antibacterial effect and promoted bone regeneration for infected bone defect treatment. As a delivery platform, the scaffold showed staged release of lysozyme and CCMV-YGFGG, which facilitates the regeneration of infected bone defects. Our study provides a novel and promising strategy for the treatment of infected bone defects.

Virus-like particles for drug delivery: a review of methods and applications

Virus-like particles (VLPs) are self-assembling protein nanoparticles that have great promise as vectors for drug delivery. VLPs are derived from viruses but retain none of their infection or replication capabilities. These protein particles have defined surface chemistries, uniform sizes, and stability properties that make them attractive starting points for drug-delivery scaffolds. Here, we review recent advances in tailoring VLPs for drug-delivery applications, including VLP platform engineering approaches as well as methods for cargo loading, activation, and release. Finally, we highlight several successes using VLPs for drug delivery in model systems.

Rip it, stitch it, click it: A Chemist's guide to VLP manipulation

Viruses are some of nature's most ubiquitous self-assembled molecular containers. Evolutionary pressures have created some incredibly robust, thermally, and enzymatically resistant carriers to transport delicate genetic information safely. Virus-like particles (VLPs) are human-engineered non-infectious systems that inherit the parent virus' ability to self-assemble under controlled conditions while being non-infectious. VLPs and plant-based viral nanoparticles are becoming increasingly popular in medicine as their self-assembly properties are exploitable for applications ranging from diagnostic tools to targeted drug delivery. Understanding the basic structure and principles underlying the assembly of higher-order structures has allowed researchers to disassemble (rip it), reassemble (stitch it), and functionalize (click it) these systems on demand. This review focuses on the current toolbox of strategies developed to manipulate these systems by ripping, stitching, and clicking to create new technologies in the biomedical space.

Assembly of Protein Cages for Drug Delivery

Nanoparticles (NPs) have been widely used as target delivery vehicles for therapeutic goods; however, compared with inorganic and organic nanomaterials, protein nanomaterials have better biocompatibility and can self-assemble into highly ordered cage-like structures, which are more favorable for applications in targeted drug delivery. In this review, we concentrate on the typical protein cage nanoparticles drugs encapsulation processes, such as drug fusion expression, diffusion, electrostatic contact, covalent binding, and protein cage disassembly/recombination. The usage of protein cage nanoparticles in biomedicine is also briefly discussed. These materials can be utilized to transport small molecules, peptides, siRNA, and other medications for anti-tumor, contrast, etc.

Fusogenic peptide modification to enhance gene delivery by peptide-DNA nano-coassemblies

Endosomal escape is a major obstacle for non-viral nucleic acids delivery. Here, we attached by click reaction a fusogenic peptide (L17E) onto peptide self-assembled disks (∼17 nm), which mimicked the functional subunits of the virus capsid. These peptide disks then spontaneously co-assembled with DNA to form patterned nanostructures (∼100 nm) as viral mimics. This modification did not affect the cellular uptake but enhanced endosomal escape and led to improved transfection in cell culture.

Multifunctional Plant Virus Nanoparticles for Targeting Breast Cancer Tumors

Breast cancer treatment using plant-virus-based nanoparticles (PVNPs) has achieved considerable success in preclinical studies. PVNP-based breast cancer therapies include non-targeted and targeted nanoplatforms for delivery of anticancer therapeutic chemo and immune agents and cancer vaccines for activation of local and systemic antitumor immunity. Interestingly, PVNP platforms combined with other tumor immunotherapeutic options and other modalities of oncotherapy can improve tumor efficacy treatment. These applications can be achieved by encapsulation of a wide range of active ingredients and conjugating ligands for targeting immune and tumor cells. This review presents the current breast cancer treatments based on PVNP platforms.

Production and characterization of chimeric SARS-CoV-2 antigens based on the capsid protein of cowpea chlorotic mottle virus

The COVID-19 pandemic has highlighted the need for new vaccine platforms to rapidly develop solutions against emerging pathogens. In particular, some plant viruses offer several advantages for developing subunit vaccines, such as high expression rates in E. coli, high immunogenicity and safety, and absence of pre-immunity that could interfere with the vaccine's efficacy. Cowpea chlorotic mottle virus (CCMV) is a model system that has been extensively characterized, with key advantages for its use as an epitope carrier. In the present study, three relevant epitopes from the SARS-CoV-2 Spike protein were genetically inserted into the CCMV CP and expressed in E. coli cultures, resulting in the CCMV1, CCMV2, and CCMV3 chimeras. The recombinant CP mutants were purified from the formed inclusion bodies and refolded, and their immunogenicity as a subunit vaccine was assessed in BALB/c mice. The three mutants are immunogenic as they induce high IgG antibody titers that recognize the recombinant full-length S protein. This study supports the application of CCMV CP as an attractive carrier for the clinical evaluation of vaccine candidates against SARS-CoV-2. Furthermore, it suggests that VLPs assembled from these chimeric proteins could result in antigens with better immunogenicity.

Protein Cages: From Fundamentals to Advanced Applications

Proteins that self-assemble into polyhedral shell-like structures are useful molecular containers both in nature and in the laboratory. Here we review efforts to repurpose diverse protein cages, including viral capsids, ferritins, bacterial microcompartments, and designed capsules, as vaccines, drug delivery vehicles, targeted imaging agents, nanoreactors, templates for controlled materials synthesis, building blocks for higher-order architectures, and more. A deep understanding of the principles underlying the construction, function, and evolution of natural systems has been key to tailoring selective cargo encapsulation and interactions with both biological systems and synthetic materials through protein engineering and directed evolution. The ability to adapt and design increasingly sophisticated capsid structures and functions stands to benefit the fields of catalysis, materials science, and medicine.

Incorporation of Endosomolytic Peptides with Varying Disruption Mechanisms into EGFR-Targeted Protein Conjugates: The Effect on Intracellular Protein Delivery and EGFR Specificity in Breast Cancer Cells

Intracellular delivery of protein therapeutics remains a significant challenge limiting the majority of clinically available protein drugs to extracellular targets. Strategies to deliver proteins to subcellular compartments have traditionally relied on cell-penetrating peptides, which can drive enhanced internalization but exhibit unreliable activity and are rarely able to target specific cells, leading to off-target effects. Moreover, few design rules exist regarding the relative efficacy of various endosomal escape strategies in proteins. Accordingly, we developed a simple fusion modification approach to incorporate endosomolytic peptides onto epidermal growth factor receptor (EGFR)-targeted protein conjugates and performed a systematic comparison of the endosomal escape efficacy, mechanism of action, and capacity to maintain EGFR-targeting specificity of conjugates modified with four different endosomolytic sequences of varying modes of action (Aurein 1.2, GALA, HA2, and L17E). Use of the recently developed Gal8-YFP assay indicated that the fusion of each endosomolytic peptide led to enhanced endosomal disruption. Additionally, the incorporation of each endosomolytic peptide increased the half-life of the internalized protein and lowered lysosomal colocalization, further supporting the membrane-disruptive capacity. Despite this, only EGFR-targeted conjugates modified with Aurein 1.2 or GALA maintained EGFR specificity. These results thus demonstrated that the choice of endosomal escape moiety can substantially affect targeting capability, cytotoxicity, and bioactivity and provided important new insights into endosomolytic peptide selection for the design of targeted protein delivery systems.

Emerging prospects of protein/peptide-based nanoassemblies for drug delivery and vaccine development

Proteins have been widely used in the biomedical field because of their well-defined architecture, accurate molecular weight, excellent biocompatibility and biodegradability, and easy-to-functionalization. Inspired by the wisdom of nature, increasing proteins/peptides that possess self-assembling capabilities have been explored and designed to generate nanoassemblies with unique structure and function, including spatially organized conformation, passive and active targeting, stimuli-responsiveness, and high stability. These characteristics make protein/peptide-based nanoassembly an ideal platform for drug delivery and vaccine development. In this review, we focus on recent advances in subsistent protein/peptide-based nanoassemblies, including protein nanocages, virus-like particles, self-assemblable natural proteins, and self-assemblable artificial peptides. The origin and characteristics of various protein/peptide-based assemblies and their applications in drug delivery and vaccine development are summarized. In the end, the prospects and challenges are discussed for the further development of protein/peptide-based nanoassemblies.

Emerging landscape of cell-penetrating peptide-mediated nucleic acid delivery and their utility in imaging, gene-editing, and RNA-sequencing

The safety issues like immunogenicity and unacceptable cancer risk of viral vectors for DNA/mRNA vaccine delivery necessitate the development of non-viral vectors with no toxicity. Among the non-viral strategies, cell-penetrating peptides (CPPs) have been a topic of interest recently because of their ability to cross plasma membranes and facilitate nucleic acids delivery both in vivo and in vitro. In addition to the application in the field of gene vaccine and gene therapy, CPPs based nucleic acids delivery have been proved by its potential application like gene editing, RNA-sequencing, and imaging. Here, we focus on summarizing the recent applications and progress of CPPs-mediated nucleic acids delivery and discuss the current problems and solutions in this field.

RNA Secondary Structures Regulate Adsorption of Fragments onto Flat Substrates

RNA is a functionally rich molecule with multilevel, hierarchical structures whose role in the adsorption to molecular substrates is only beginning to be elucidated. Here, we introduce a multiscale simulation approach that combines a tractable coarse-grained RNA structural model with an interaction potential of a structureless flat adsorbing substrate. Within this approach, we study the specific role of stem-hairpin and multibranch RNA secondary structure motifs on its adsorption phenomenology. Our findings identify a dual regime of adsorption for short RNA fragments with and without the secondary structure and underline the adsorption efficiency in both cases as a function of the surface interaction strength. The observed behavior results from an interplay between the number of contacts formed at the surface and the conformational entropy of the RNA molecule. The adsorption phenomenology of RNA seems to persist also for much longer RNAs as qualitatively observed by comparing the trends of our simulations with a theoretical approach based on an ideal semiflexible polymer chain.

VLP-Based COVID-19 Vaccines: An Adaptable Technology against the Threat of New Variants

Virus-like particles (VLPs) are a versatile, safe, and highly immunogenic vaccine platform. Recently, there are developmental vaccines targeting SARS-CoV-2, the causative agent of COVID-19. The COVID-19 pandemic affected humanity worldwide, bringing out incomputable human and financial losses. The race for better, more efficacious vaccines is happening almost simultaneously as the virus increasingly produces variants of concern (VOCs). The VOCs Alpha, Beta, Gamma, and Delta share common mutations mainly in the spike receptor-binding domain (RBD), demonstrating convergent evolution, associated with increased transmissibility and immune evasion. Thus, the identification and understanding of these mutations is crucial for the production of new, optimized vaccines. The use of a very flexible vaccine platform in COVID-19 vaccine development is an important feature that cannot be ignored. Incorporating the spike protein and its variations into VLP vaccines is a desirable strategy as the morphology and size of VLPs allows for better presentation of several different antigens. Furthermore, VLPs elicit robust humoral and cellular immune responses, which are safe, and have been studied not only against SARS-CoV-2 but against other coronaviruses as well. Here, we describe the recent advances and improvements in vaccine development using VLP technology.

Enzymatic ligation of an antibody and arginine 9 peptide for efficient and cell-specific siRNA delivery

A fusion protein comprising an antibody and a cationic peptide, such as arginine-9 (R9), is a candidate molecule for efficient and cell-specific delivery of siRNA into cells in order to reduce the side effects of nucleic acid drugs. However, their expression in bacterial hosts, required for their development, often fails, impeding research progress. In this study, we separately prepared anti-EGFR nanobodies with the K-tag sequence MRHKGS at the C-terminus and R9 with the Q-tag sequence LLQG at the N-terminus, and enzymatically ligated them in vitro by microbial transglutaminase to generate Nanobody-R9, which is not expressed as a fused protein in E. coli. Nanobody-R9 was synthesized at a maximum binding efficiency of 85.1%, without changing the binding affinity of the nanobody for the antigen. Nanobody-R9 successfully delivered siRNA into the cells, and the cellular influx of siRNA increased with increase in the ratio of Nanobody-R9 to siRNA. We further demonstrated that the Nanobody-R9-siRNA complex, at a 30:1 ratio, induced an approximately 58.6% reduction in the amount of target protein due to RNAi in mRNA compared to lipofectamine.

S100A9-Targeted Cowpea Mosaic Virus as a Prophylactic and Therapeutic Immunotherapy against Metastatic Breast Cancer and Melanoma

Prognosis and treatment of metastatic cancer continues to be one of the most difficult and challenging areas of oncology. Treatment usually consists of chemotherapeutics, which may be ineffective due to drug resistance, adverse effects, and dose-limiting toxicity. Therefore, novel approaches such as immunotherapy have been investigated to improve patient outcomes and minimize side effects. S100A9 is a calcium-binding protein implicated in tumor metastasis, progression, and aggressiveness that modulates the tumor microenvironment into an immunosuppressive state. S100A9 is expressed in and secreted by immune cells in the pre-metastatic niche, as well as, post-tumor development, therefore making it a suitable targeted for prophylaxis and therapy. In previous work, it is demonstrated that cowpea mosaic virus (CPMV) acts as an adjuvant when administered intratumorally. Here, it is demonstrated that systemically administered, S100A9-targeted CPMV homes to the lungs leading to recruitment of innate immune cells. This approach is efficacious both prophylactically and therapeutically against lung metastasis from melanoma and breast cancer. The current research will facilitate and accelerate the development of next-generation targeted immunotherapies administered as prophylaxis, that is, after surgery of a primary breast tumor to prevent outgrowth of metastasis, as well as, therapy to treat established metastatic disease.

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.

Recent progress in targeted delivery vectors based on biomimetic nanoparticles

Over the past decades, great interest has been given to biomimetic nanoparticles (BNPs) since the rise of targeted drug delivery systems and biomimetic nanotechnology. Biological vectors including cell membranes, extracellular vesicles (EVs), and viruses are considered promising candidates for targeted delivery owing to their biocompatibility and biodegradability. BNPs, the integration of biological vectors and functional agents, are anticipated to load cargos or camouflage synthetic nanoparticles to achieve targeted delivery. Despite their excellent intrinsic properties, natural vectors are deliberately modified to endow multiple functions such as good permeability, improved loading capability, and high specificity. Through structural modification and transformation of the vectors, they are pervasively utilized as more effective vehicles that can deliver contrast agents, chemotherapy drugs, nucleic acids, and genes to target sites for refractory disease therapy. This review summarizes recent advances in targeted delivery vectors based on cell membranes, EVs, and viruses, highlighting the potential applications of BNPs in the fields of biomedical imaging and therapy industry, as well as discussing the possibility of clinical translation and exploitation trend of these BNPs.

Cell-penetrating Peptide-mediated Nanovaccine Delivery

Vaccination with small antigens, such as proteins, peptides, or nucleic acids, is used to activate the immune system and trigger the protective immune responses against a pathogen. Currently, nanovaccines are undergoing development instead of conventional vaccines. The size of nanovaccines is in the range of 10-500 nm, which enables them to be readily taken up by cells and exhibit improved safety profiles. However, low-level immune responses, as the removal of redundant pathogens, trigger counter-effective activation of the immune system invalidly and present a challenging obstacle to antigen recognition and its uptake via antigen-presenting cells (APCs). In addition, toxicity can be substantial. To overcome these problems, a variety of cell-penetrating peptide (CPP)-mediated vaccine delivery systems based on nanotechnology have been proposed, most of which are designed to improve the stability of antigens in vivo and their delivery into immune cells. CPPs are particularly attractive components of antigen delivery. Thus, the unique translocation property of CPPs ensures that they remain an attractive carrier with the capacity to deliver cargo in an efficient manner for the application of drugs, gene transfer, protein, and DNA/RNA vaccination delivery. CPP-mediated nanovaccines can enhance antigen uptake, processing, and presentation by APCs, which are the fundamental steps in initiating an immune response. This review describes the different types of CPP-based nanovaccines delivery strategies.

Cowpea Chlorotic Mottle Virus-Like Particles as Potential Platform for Antisense Oligonucleotide Delivery in Posterior Segment Ocular Diseases

Due to its small size, easy accessibility and immune privileged environment, the eye represents an ideal target for therapeutic nucleic acids in the treatment of posterior segment ocular diseases, such as age-related macular degeneration (AMD). Among nanocarriers that can be used to achieve nucleic acid delivery, virus-like particles (VLPs) obtained from the Cowpea chlorotic mottle virus (CCMV) are an appealing platform, because of their loading capacity, ease of manufacture and amenability for functionalization. Herein, antisense oligonucleotide-loaded CCMV nanoparticles, intended for intravitreal injection, are evaluated for selective silencing of miR-23, an important target in AMD. CCMV nanoparticles loaded with anti-miR-23 locked nucleic acid and stabilized using the 3,3'-dithiobis(sulfosuccinimidyl propionate) (DTSSP) cross-linker, are assembled in vitro with a loading efficiency up to 80%. VLPs are found to be stable at 37 °C in the vitreous humor up to 24 hours. Nanoparticle cytotoxicity, cellular uptake and transfection efficacy are evaluated in endothelial cells. Selective miRNA down-regulation is achieved by the loaded CCMV VLPs both in absence and presence of Lipofectamine, with efficacies of ≈40% and more than 80%, respectively. The authors' findings pave the way for the future development of CCMV nanoparticles as oligonucleotide delivery platform to treat posterior segment ocular diseases.

Lignin, lipid, protein, hyaluronic acid, starch, cellulose, gum, pectin, alginate and chitosan-based nanomaterials for cancer nanotherapy: Challenges and opportunities

Although nanotechnology-driven drug delivery systems are relatively new, they are rapidly evolving since the nanomaterials are deployed as effective means of diagnosis and delivery of assorted therapeutic agents to targeted intracellular sites in a controlled release manner. Nanomedicine and nanoparticulate drug delivery systems are rapidly developing as they play crucial roles in the development of therapeutic strategies for various types of cancer and malignancy. Nevertheless, high costs, associated toxicity and production of complexities are some of the critical barriers for their applications. Green nanomedicines have continually been improved as one of the viable approaches towards tumor drug delivery, thus making a notable impact on which considerably affect cancer treatment. In this regard, the utilization of natural and renewable feedstocks as a starting point for the fabrication of nanosystems can considerably contribute to the development of green nanomedicines. Nanostructures and biopolymers derived from natural and biorenewable resources such as proteins, lipids, lignin, hyaluronic acid, starch, cellulose, gum, pectin, alginate, and chitosan play vital roles in the development of cancer nanotherapy, imaging and management. This review uncovers recent investigations on diverse nanoarchitectures fabricated from natural and renewable feedstocks for the controlled/sustained and targeted drug/gene delivery systems against cancers including an outlook on some of the scientific challenges and opportunities in this field. Various important natural biopolymers and nanomaterials for cancer nanotherapy are covered and the scientific challenges and opportunities in this field are reviewed.

In Vitro Assembly of Virus-Like Particles and Their Applications

Virus-like particles (VLPs) are increasingly used for vaccine development and drug delivery. Assembly of VLPs from purified monomers in a chemically defined reaction is advantageous compared to in vivo assembly, because it avoids encapsidation of host-derived components and enables loading with added cargoes. This review provides an overview of ex cella VLP production methods focusing on capsid protein production, factors that impact the in vitro assembly, and approaches to characterize in vitro VLPs. The uses of in vitro produced VLPs as vaccines and for therapeutic delivery are also reported.

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.

Viral Mimicry as a Design Template for Nucleic Acid Nanocarriers

Therapeutic nucleic acids hold immense potential in combating undruggable, gene-based diseases owing to their high programmability and relative ease of synthesis. While the delivery of this class of therapeutics has successfully entered the clinical setting, extrahepatic targeting, endosomal escape efficiency, and subcellular localization. On the other hand, viruses serve as natural carriers of nucleic acids and have acquired a plethora of structures and mechanisms that confer remarkable transfection efficiency. Thus, understanding the structure and mechanism of viruses can guide the design of synthetic nucleic acid vectors. This review revisits relevant structural and mechanistic features of viruses as design considerations for efficient nucleic acid delivery systems. This article explores how viral ligand display and a metastable structure are central to the molecular mechanisms of attachment, entry, and viral genome release. For comparison, accounted for are details on the design and intracellular fate of existing nucleic acid carriers and nanostructures that share similar and essential features to viruses. The review, thus, highlights unifying themes of viruses and nucleic acid delivery systems such as genome protection, target specificity, and controlled release. Sophisticated viral mechanisms that are yet to be exploited in oligonucleotide delivery are also identified as they could further the development of next-generation nonviral nucleic acid vectors.

Virus-Based Nanoreactors with GALT Activity for Classic Galactosemia Therapy

Enzymatic nanoreactors were obtained by galactose-1-phosphate uridylyl-transferase (GALT) encapsulation into plant virus capsids by a molecular self-assembly strategy. The aim of this work was to produce virus-like nanoparticles containing GALT for an enzyme-replacement therapy for classic galactosemia. The encapsulation efficiency and the catalytic constants of bio-nanoreactors were determined by using different GALT and virus coat protein ratios. The substrate affinity of nanoreactors was slightly lower than that of the free enzyme; the activity rate was 16 % of the GALT free enzyme. The enzymatic nanoreactors without functionalization were internalized into different cell lines including fibroblast and kidney cells, but especially into hepatocytes. The enzymatic nanoreactors are an innovative enzyme preparation with potential use for the treatment of classic galactosemia.

Biomimetic bacterial and viral-based nanovesicles for drug delivery, theranostics, and vaccine applications

Smart nanocarriers obtained from bacteria and viruses offer excellent biomimetic properties which has led to significant research into the creation of advanced biomimetic materials. Their versatile biomimicry has application as biosensors, biomedical scaffolds, immobilization, diagnostics, and targeted or personalized treatments. The inherent natural traits of biomimetic and bioinspired bacteria- and virus-derived nanovesicles show potential for their use in clinical vaccines and novel therapeutic drug delivery systems. The past few decades have seen significant progress in the bioengineering of bacteria and viruses to manipulate and enhance their therapeutic benefits. From a pharmaceutical perspective, biomimetics enable the safe integration of naturally occurring bacteria and virus particles to achieve high, stable rates of cellular transfection/infection and prolonged circulation times. In addition, biomimetic technologies can overcome safety concerns associated with live-attenuated and inactivated whole bacteria or viruses. In this review, we provide an update on the utilization of bacterial and viral particles as drug delivery systems, theranostic carriers, and vaccine/immunomodulation modalities.

The Role of Virus-Like Particles in Medical Biotechnology

Virus-like particles (VLPs) are protein-based, nanoscale, self-assembling, cage architectures, which have relevant applications in biomedicine. They can be used for the development of vaccines, imaging approaches, drug and gene therapy delivery systems, and in vitro diagnostic methods. Today, three relevant viruses are targeted using VLP-based recombinant vaccines. VLP-based drug delivery, nanoreactors for therapy, and imaging systems are approaches under development with promising outcomes. Several VLP-based vaccines are under clinical evaluation. Herein, an updated view on the VLP-based biomedical applications is provided; advanced methods for the production, functionalization, and drug loading of VLPs are described, and perspectives for the field are identified.

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.

Plant Viruses and Bacteriophage-Based Reagents for Diagnosis and Therapy

Viral nanotechnology exploits the prefabricated nanostructures of viruses, which are already abundant in nature. With well-defined molecular architectures, viral nanocarriers offer unprecedented opportunities for precise structural and functional manipulation using genetic engineering and/or bio-orthogonal chemistries. In this manner, they can be loaded with diverse molecular payloads for targeted delivery. Mammalian viruses are already established in the clinic for gene therapy and immunotherapy, and inactivated viruses or virus-like particles have long been used as vaccines. More recently, plant viruses and bacteriophages have been developed as nanocarriers for diagnostic imaging, vaccine and drug delivery, and combined diagnosis/therapy (theranostics). The first wave of these novel virus-based tools has completed clinical development and is poised to make an impact on clinical practice.

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.

Viral nanoparticles for drug delivery, imaging, immunotherapy, and theranostic applications

Viral nanoparticles (VNPs) encompass a diverse array of naturally occurring nanomaterials derived from plant viruses, bacteriophages, and mammalian viruses. The application and development of VNPs and their genome-free versions, the virus-like particles (VLPs), for nanomedicine is a rapidly growing. VLPs can encapsulate a wide range of active ingredients as well as be genetically or chemically conjugated to targeting ligands to achieve tissue specificity. VLPs are manufactured through scalable fermentation or molecular farming, and the materials are biocompatible and biodegradable. These properties have led to a wide range of applications, including cancer therapies, immunotherapies, vaccines, antimicrobial therapies, cardiovascular therapies, gene therapies, as well as imaging and theranostics. The use of VLPs as drug delivery agents is evolving, and sufficient research must continuously be undertaken to translate these therapies to the clinic. This review highlights some of the novel research efforts currently underway in the VNP drug delivery field in achieving this greater goal.

Protein cages and virus-like particles: from fundamental insight to biomimetic therapeutics

Protein cages (viral and non-viral) found in nature have evolved for a variety of purposes and are found in all kingdoms of life. The main functions of these nanoscale compartments are the protection and delivery of nucleic acids e.g. virus capsids, or the enrichment and sequestration of metabolons e.g. bacterial microcompartments. This review focuses on recent developments of protein cages for use in immunotherapy and therapeutic delivery. In doing so, we highlight the unique ways in which protein cages have informed on fundamental principles governing bio-nano interactions. With the enormous existing design space among naturally occurring protein cages, there is still much to learn from studying them as biomimetic particles.

The Antitumor Efficacy of CpG Oligonucleotides is Improved by Encapsulation in Plant Virus-Like Particles

Oligodeoxynucleotides (ODNs) with CpG motifs have potent immunostimulatory effects on many subsets of immune cells. For example, Class B CpG-ODNs, such as ODN1826 induce the phagocytic activity of macrophages by activating the Toll-like receptor 9 signaling pathway. Systemic ODN delivery results in unfavorable pharmacokinetic profiles and can trigger adverse effects. To address this issue, plant virus-like particles (VLPs) are developed for the targeted delivery of ODN1826 to tumor-associated macrophages (TAMs). ODN1826 is encapsulated by the in vitro disassembly and reassembly of Cowpea chlorotic mottle virus (CCMV), producing VLPs that are structurally analogous to the native virus. The encapsulation of ODN1826 in CCMV-derived VLPs promotes ODN uptake by TAMs ex vivo and significantly enhance their phagocytic activity. The antitumor activity of the VLPs in vivo is also evaluated, revealing that the direct injection of ODN1826 VLPs into established tumors induces a robust antitumor response by increasing the phagocytic activity of TAMs in the tumor microenvironment. CCMV encapsulation significantly enhances the efficacy of ODN1826 compared to the free drug, slowing tumor growth and prolonging survival in mouse models of colon cancer and melanoma.

Nanocarriers for the Delivery of Medical, Veterinary, and Agricultural Active Ingredients

Nanocarrier-based delivery systems can be used to increase the safety and efficacy of active ingredients in medical, veterinary, or agricultural applications, particularly when such ingredients are unstable, sparingly soluble, or cause off-target effects. In this review, we highlight the diversity of nanocarrier materials and their key advantages compared to free active ingredients. We discuss current trends based on peer-reviewed research articles, patent applications, clinical trials, and the nanocarrier formulations already approved by regulatory bodies. Although most nanocarriers have been engineered to combat cancer, the number of formulations developed for other purposes is growing rapidly, especially those for the treatment of infectious diseases and parasites affecting humans, livestock, and companion animals. The regulation and prohibition of many pesticides have also fueled research to develop targeted pesticide delivery systems based on nanocarriers, which maximize efficacy while minimizing the environmental impact of agrochemicals.

Disassembly Intermediates of the Brome Mosaic Virus Identified by Charge Detection Mass Spectrometry

Capsid disassembly and genome release are critical steps in the lifecycle of a virus. However, their mechanisms are poorly understood, both in vivo and in vitro. Here, we have identified two in vitro disassembly pathways of the brome mosaic virus (BMV) by charge detection mass spectrometry and transmission electron microscopy. When subjected to a pH jump to a basic environment at low ionic strength, protein-RNA interactions are disrupted. Under these conditions, BMV appears to disassemble mainly through a global cleavage event into two main fragments: a near complete capsid that has released the RNA and the released RNA complexed to a small number of the capsid proteins. Upon slow buffer exchange to remove divalent cations at neutral pH, capsid protein interactions are disrupted. The BMV virions swell but there is no measurable loss of the RNA. Some of the virions break into small fragments, leading to an increase in the abundance of species with masses less than 1 MDa. The peak attributed to the BMV virion shifts to a higher mass with time. The mass increase is attributed to additional capsid proteins associating with the disrupted capsid protein-RNA complex, where the RNA is presumably partially exposed. It is likely that this pathway is more closely related to how the capsid disassembles in vivo, as it offers the advantage of protecting the RNA with the capsid protein until translation begins.

Insight into N-terminal localization and dynamics of engineered virus-like particles

The N-terminal localization and dynamic intermixing of engineered cowpea chlorotic mottle virus-like particles were studied independently from each other.

Brome mosaic virus-like particles as siRNA nanocarriers for biomedical purposes

There is an increasing interest in the use of plant viruses as vehicles for anti-cancer therapy. In particular, the plant virus brome mosaic virus (BMV) and cowpea chlorotic mottle virus (CCMV) are novel potential nanocarriers for different therapies in nanomedicine. In this work, BMV and CCMV were loaded with a fluorophore and assayed on breast tumor cells. The viruses BMV and CCMV were internalized into breast tumor cells. Both viruses, BMV and CCMV, did not show cytotoxic effects on tumor cells in vitro. However, only BMV did not activate macrophages in vitro. This suggests that BMV is less immunogenic and may be a potential carrier for therapy delivery in tumor cells. Furthermore, BMV virus-like particles (VLPs) were efficiently loaded with small interfering RNA (siRNA) without packaging signal. The gene silencing was demonstrated by VLPs loaded with siGFP and tested on breast tumor cells that constitutively express the green fluorescent protein (GPF). After VLP-siGFP treatment, GFP expression was efficiently inhibited corroborating the cargo release inside tumor cells and the gene silencing. In addition, BMV VLP carring siAkt1 inhibited the tumor growth in mice. These results show the attractive potential of plant virus VLPs to deliver molecular therapy to tumor cells with low immunogenic response.