Folic Acid-Conjugated Protein Cages of a Plant Virus: A Novel Delivery Platform for Doxorubicin

Exploring the Potential of Plant-Based Nanotechnology in Cancer Immunotherapy: Benefits, Limitations, and Future Perspectives

Reconceptualizing cancer immunotherapy can be improved if combined with plant production systems and nanotechnology. This review aims to contribute to the knowledge of plant use in nanomedicine and cancer immunotherapy. In the foreground, we outlined each of these approaches; nanomedicine, green synthesis, and immunotherapy. The benefits of plant-based nanoparticles in mending the immune systems were subsequently analyzed, with reference to the literature. The combining effects of biological and therapeutic properties of some phytochemicals and their derivatives, with targeted nanoparticles and selective immunotherapy, can enhance the delivery of drugs and antibodies, and induce antitumor immune responses, via activation of functions of neutrophils, lymphocyte cells, and natural killer cells, and macrophages, resulting in induced apoptosis and phagocytosis of tumor cells, which can improve designing immunotherapeutic strategies targeting cancer, with a larger spectrum compared to the current cytotoxic anticancer drugs commonly used in clinics. This study uncovers the mechanistic drivers of cancer immunoengineering in cancer therapy using plant-based nanomaterials, enhancing therapeutic benefits while minimizing toxic and side effects.

Artificial viruses: A nanotechnology based approach

OBJECTIVES

The main objective of this work was to review and summarise the detailed literature available on viral nanoparticle and the strategies utilised for their manufacture along with their applications as therapeutic agents.

DATA ACQUISITION

The reported literature related to development and application of virus nanoparticles have been collected from electronic data bases like ScienceDirect, google scholar, PubMed by using key words like "viral nanoparticles", "targeted drug delivery" and "vaccines" and related combinations.

RESULT

From the detailed literature survey, virus nanoparticles were identified as carriers for the targeted delivery. Due to the presence of nanostructures in virus nanoparticles, these protect the drugs from the degradation in the gastrointestinal tract and in case of the delivery of gene medicine, they carry the nucleic acids to the target/susceptible host cells. Thus, artificial viruses are utilised for targeted delivery to specific organ in biomedical and biotechnological areas.

CONCLUSION

Thus, virus nanoparticles can be considered as viable option as drug/gene carrier in various healthcare sectors especially drug delivery and vaccine and can be explored further in future for the development of better drug delivery techniques.

Overcoming biological barriers by virus-like drug particles for drug delivery

Virus-like particles (VLPs) have natural structural antigens similar to those found in viruses, making them valuable in vaccine immunization. Furthermore, VLPs have demonstrated significant potential in drug delivery, and emerged as promising vectors for transporting chemical drug, genetic drug, peptide/protein, and even nanoparticle drug. With virus-like permeability and strong retention, they can effectively target specific organs, tissues or cells, facilitating efficient intracellular drug release. Further modifications allow VLPs to transfer across various physiological barriers, thus acting the purpose of efficient drug delivery and accurate therapy. This article provides an overview of VLPs, covering their structural classifications, deliverable drugs, potential physiological barriers in drug delivery, strategies for overcoming these barriers, and future prospects.

Multifunctional plant virus nanoparticles: An emerging strategy for therapy of cancer

Cancer therapy requires sophisticated treatment strategies to obtain the highest success. Nanotechnology is enabling, revolutionizing, and multidisciplinary concepts to improve conventional cancer treatment modalities. Nanomaterials have a central role in this scenario, explaining why various nanomaterials are currently being developed for cancer therapy. Viral nanoparticles (VNPs) have shown promising performance in cancer therapy due to their unique features. VNPs possess morphological homogeneity, ease of functionalization, biocompatibility, biodegradability, water solubility, and high absorption efficiency that are beneficial for cancer therapy applications. In the current review paper, we highlight state-of-the-art properties and potentials of plant viruses, strategies for multifunctional plant VNPs formulations, potential applications and challenges in VNPs-based cancer therapy, and finally practical solutions to bring potential cancer therapy one step closer to real applications. This article is categorized under: Therapeutic Approaches and Drug Discovery > Nanomedicine for Oncologic Disease Nanotechnology Approaches to Biology > Nanoscale Systems in Biology Biology-Inspired Nanomaterials > Protein and Virus-Based Structures.

Therapeutic Potential of Engineered Virus-like Particles of Parvovirus B19

Virus-like particles (VLPs) comprise one or many structural components of virions, except their genetic material. Thus, VLPs keep their structural properties of cellular recognition while being non-infectious. VLPs of Parvovirus B19 (B19V) can be produced by the heterologous expression of their structural proteins VP1 and VP2 in bacteria. These proteins are purified under denaturing conditions, refolded, and assembled into VLPs. Moreover, chimeric forms of VP2 have been constructed to harbor peptides or functional proteins on the surface of the particles without dropping their competence to form VLPs, serving as presenting nanoparticles. The in-vitro assembly approach offers exciting possibilities for the composition of VLPs, as more than one chimeric form of VP2 can be included in the assembly stage, producing multifunctional VLPs. Here, the heterologous expression and in-vitro assembly of B19V structural proteins and their chimeras are reviewed. Considerations for the engineering of the structural proteins of B19V are also discussed. Finally, the construction of multifunctional VLPs and their future potential as innovative medical tools are examined.

Next-generation viral nanoparticles for targeted delivery of therapeutics: Fundamentals, methods, biomedical applications, and challenges

INTRODUCTION

Viral nanoparticles (VNPs) are virus-based nanocarriers that have been studied extensively and intensively for biomedical applications. However, their clinical translation is relatively low compared to the predominating lipid-based nanoparticles. Therefore, this article describes the fundamentals, challenges, and solutions of the VNP-based platform, which will leverage the development of next-generation VNPs.

AREAS COVERED

Different types of VNPs and their biomedical applications are reviewed comprehensively. Strategies and approaches for cargo loading and targeted delivery of VNPs are examined thoroughly. The latest developments in controlled release of cargoes from VNPs and their mechanisms are highlighted too. The challenges faced by VNPs in biomedical applications are identified, and solutions are provided to overcome them.

EXPERT OPINION

In the development of next-generation VNPs for gene therapy, bioimaging and therapeutic deliveries, focus must be given to reduce their immunogenicity, and increase their stability in the circulatory system. Modular virus-like particles (VLPs) which are produced separately from their cargoes or ligands before all the components are coupled can speed up clinical trials and commercialization. In addition, removal of contaminants from VNPs, cargo delivery across the blood brain barrier (BBB), and targeting of VNPs to organelles intracellularly are challenges that will preoccupy researchers in this decade.

Virus-like particle-based nanocarriers as an emerging platform for drug delivery

New nanocarrier technologies are emerging, and they have great potential for improving drug delivery, targeting efficiency, and bioavailability. Virus-like particles (VLPs) are natural nanoparticles from animal and plant viruses and bacteriophages. Hence, VLPs present several great advantages, such as morphological uniformity, biocompatibility, reduced toxicity, and easy functionalisation. VLPs can deliver many active ingredients to the target tissue and have great potential as a nanocarrier to overcome the limitations associated with other nanoparticles. This review will focus primarily on the construction and applications of VLPs, particularly as a novel nanocarrier to deliver active ingredients. Herein, the main methods for the construction, purification, and characterisation of VLPs, as well as various VLP-based materials used in delivery systems are summarised. The biological distribution of VLPs in drug delivery, phagocyte-mediated clearance, and toxicity are also discussed.

Production of cytoplasmic type citrus leprosis virus-like particles by plant molecular farming

Many plant virus-like particles (VLPs) utilized in nanotechnology are 30-nm icosahedrons. To expand the VLP platforms, we produced VLPs of Cytoplasmic type citrus leprosis virus (CiLV-C) in Nicotiana benthamiana. We were interested in CiLV-C because of its unique bacilliform shape (60-70 nm × 110-120 nm). The CiLV-C capsid protein (p29) gene was transferred to the pTRBO expression vector transiently expressed in leaves. Stable VLPs were formed, as confirmed by agarose gel electrophoresis, transmission electron microscopy and size exclusion chromatography. Interestingly, the morphology of the VLPs (15.8 ± 1.3 nm icosahedral particles) differed from that of the native bacilliform particles indicating that the assembly of native virions is influenced by other viral proteins and/or the packaged viral genome. The smaller CiLV-C VLPs will also be useful for structure-function studies to compare with the 30-nm icosahedrons of other VLPs.

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.

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.

Bi-Functional Gold Nanorod-Protein Conjugates with Biomimetic BSA@Folic Acid Corona for Improved Tumor Targeting and Intracellular Delivery of Therapeutic Proteins in Colon Cancer 3D Spheroids

Gold nanorods (AuNRs) remain well-developed inorganic nanocarriers of small molecules for a plethora of biomedical and therapeutic applications. However, the delivery of therapeutic proteins using AuNRs with high protein loading capacity (LC), serum stability, excellent target specificity, and minimal off-target protein release is not known. Herein, we report two bi-functional AuNR-protein nanoconjugates, AuNR@EGFP-BSA_FA and AuNR@RNaseA-BSA_FA, supramolecularly coated with folic acid-modified BSA (BSA_FA) acting as biomimetic protein corona to demonstrate targeted cytosolic delivery of enhanced green fluorescent protein (EGFP) and therapeutic ribonuclease A enzyme (RNase A) in their functional forms. AuNR@EGFP-BSA_FA and AuNR@RNaseA-BSA_FA exhibit high LCs of ∼42 and ∼54%, respectively, increased colloidal stability, and rapid protein release in the presence of biological thiols. As a nanocarrier, AuNR@EGFP-BSA_FA and AuNR@RNaseA-BSA_FA show resistance to corona formation in high-serum media even after 24 h, guaranteeing a greater circulation lifetime. Folate receptor-targeting BSA_FA on the AuNR surface facilitates the receptor-mediated internalization, followed by the release of EGFP and RNase A in HT29 cells. The green fluorescence dispersed throughout the cell's cytoplasm indicates successful cytosolic delivery of EGFP by AuNR@EGFP-BSA_FA. AuNR@RNaseA-BSA_FA-mediated therapeutic RNase A delivery in multicellular 3D spheroids of HT29 cells exhibits a radical reduction in the cellular RNA fluorescence intensity to 38%, signifying RNA degradation and subsequent cell death. The versatile nanoformulation strategy in terms of the anisotropic particle morphology, protein type, and ability for targeted delivery in the functional form makes the present AuNR-protein nanoconjugates a promising platform for potential application in cancer management.

Cryo-EM reconstructions of BMV-derived virus-like particles reveal assembly defects in the icosahedral lattice structure

The increasing interest in virus-like particles (VLPs) has been reflected by the growing number of studies on their assembly and application. However, the formation of complete VLPs is a complex phenomenon, making it difficult to rationally design VLPs with desired features de novo. In this paper, we describe VLPs assembled in vitro from the recombinant capsid protein of brome mosaic virus (BMV). The analysis of VLPs was performed by Cryo-EM reconstructions and allowed us to visualize a few classes of VLPs, giving insight into the VLP self-assembly process. Apart from the mature icosahedral VLP practically identical with native virions, we describe putative VLP intermediates displaying non-icosahedral arrangements of capsomers, proposed to occur before the final disorder-order transition stage of icosahedral VLP assembly. Some of the described VLP classes show a lack of protein shell continuity, possibly resulting from too strong interaction with the cargo (in this case tRNA) with the capsid protein. We believe that our results are a useful prerequisite for the rational design of VLPs in the future and lead the way to the effective production of modified VLPs.

EGFR Ligand Clustering on E2 Bionanoparticles for Targeted Delivery of Chemotherapeutics to Breast Cancer Cells

Naturally occurring protein nanocages are promising drug carriers because of their uniform size and biocompatibility. Engineering efforts have enhanced the delivery properties of nanocages, but cell specificity and high drug loading remain major challenges. Herein, we fused the SpyTag peptide to the surface of engineered E2 nanocages to enable tunable nanocage decoration and effective E2 cell targeting using a variety of SpyCatcher (SC) fusion proteins. Additionally, the core of the E2 nanocage incorporated four phenylalanine mutations previously shown to allow hydrophobic loading of doxorubicin and pH-responsive release in acidic environments. We functionalized the surface of the nanocage with a highly cell-specific epidermal growth factor receptor (EGFR)-targeting protein conjugate, 4GE11-mCherry-SC, developed previously in our laboratories by employing unnatural amino acid (UAA) protein engineering chemistries. Herein, we demonstrated the benefits of this engineered protein nanocage construct for efficient drug loading, with a straightforward method for removal of the unloaded drug through elastin-like polypeptide-mediated inverse transition cycling. Additionally, we demonstrated approximately 3-fold higher doxorubicin internalization in inflammatory breast cancer cells compared to healthy breast epithelial cells, leading to targeted cell death at concentrations below the IC50 of free doxorubicin. Collectively, these results demonstrated the versatility of our UAA-based EGFR-targeting protein construct to deliver a variety of cargoes efficiently, including engineered E2 nanocages capable of site-specific functionalization and doxorubicin loading.

Bioengineering of virus-like particles as dynamic nanocarriers for in vivo delivery and targeting to solid tumours

Virus-like particles (VLPs) are known as self-assembled, non-replicative and non-infectious protein particles, which imitate the formation and structure of original wild type viruses, however, lack the viral genome and/or their fragments. The capacity of VLPs to encompass small molecules like nucleic acids and others has made them as novel vessels of nanocarriers for drug delivery applications. In addition, VLPs surface have the capacity to achieve variation of the surface display via several modification strategies including genetic modification, chemical modification, and non-covalent modification. Among the VLPs nanocarriers, Hepatitis B virus core (HBc) particles have been the most encouraging candidate. HBc particles are hollow nanoparticles in the range of 30-34 nm in diameter and 7 nm thick envelopes, consisting of 180 or 240 copies of identical polypeptide monomer. They also employ a distinctive position among the VLPs carriers due to the high-level synthesis, which serves as a strong protective capsid shell and efficient self-assembly properties. This review highlights on the bioengineering of HBc particles as dynamic nanocarriers for in vivo delivery and specific targeting to solid tumours.

The viral capsid as novel nanomaterials for drug delivery

The purpose of this review is to highlight recent scientific developments and provide an overview of virus self-assembly and viral particle dynamics. Viruses are organized supramolecular structures with distinct yet related features and functions. Plant viruses are extensively used in biotechnology, and virus-like particulate matter is generated by genetic modification. Both provide a material-based means for selective distribution and delivery of drug molecules. Through surface engineering of their capsids, virus-derived nanomaterials facilitate various potential applications for selective drug delivery. Viruses have significant implications in chemotherapy, gene transfer, vaccine production, immunotherapy and molecular imaging.

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.

A promising dual-drug targeted delivery system in cancer therapy: nanocomplexes of folate-apoferritin-conjugated cationic solid lipid nanoparticles

Various nano-sized protein and lipid complexes are being investigated as drug delivery systems. The encapsulation of more than one drug in a single nanocomplex carrier could enhance the therapeutic potency and afford synergistic therapeutic effects. In this study, we developed a novel protein-lipid nanocomplex as a controlled drug delivery system for two important cancer drugs, doxorubicin (DOX) and mitoxantrone (MTO). Apoferritin (AFr) functionalized with folic acid (FA) was used to encapsulate DOX to create the targeted protein nanocomplexes (TPNs). The second drug, MTO, was loaded into the cationic solid lipid nanoparticles (cSLN) to form the liposomal drug nanocomplex particles (MTO-cSLNs). Two complexes were then assembled by tight coupling through ionic interactions to obtain the final drug delivery system, the dual-targeted protein-lipid nanocomplexes (DTPLNs). UV-Vis and fluorescence spectroscopy were used for structural characterization of TPNs and DTPLNs. Transmission electron microscopy (TEM) was used for comprehensive analysis of the final DTPLNs. We confirmed that the DTPLNs display desired time-dependent and pH-dependent drug release behaviors. We also demonstrated the improved anti-cancer efficacy of DOX and MTO in their encapsulated DTPLNs as compared to their free forms. Our results provide promising prospects for the application of the DTPLNs as efficient drug delivery systems.

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.

The pharmacology of plant virus nanoparticles

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

Inorganic-organic Nanomaterials for Therapeutics and Molecular Imaging Applications

Background::

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

Objectives::

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

Methods::

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

Results::

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

Conclusion::

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

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.

The biomedical and bioengineering potential of protein nanocompartments

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

Design and biosynthesis of functional protein nanostructures

Proteins are one of the major classes of biomolecules that execute biological functions for maintenance of life. Various kinds of nanostructures self-assembled from proteins have been created in nature over millions of years of evolution, including protein nanowires, layers and nanocages. These protein nanostructures can be reconstructed and equipped with desired new functions. Learning from and manipulating the self-assembly of protein nanostructures not only help to deepen our understanding of the nature of life but also offer new routes to fabricate novel nanomaterials for diverse applications. This review summarizes the recent research progress in this field, focusing on the characteristics, functionalization strategies, and applications of protein nanostructures.

Virus-based pharmaceutical production in plants: an opportunity to reduce health problems in Africa

BACKGROUND

Developing African countries face health problems that they struggle to solve. The major causes of this situation are high therapeutic and logistical costs. Plant-made therapeutics are easy to produce due to the lack of the safety considerations associated with traditional fermenter-based expression platforms, such as mammalian cells. Plant biosystems are easy to scale up and inexpensive, and they do not require refrigeration or a sophisticated medical infrastructure. These advantages provide an opportunity for plant-made pharmaceuticals to counteract diseases for which medicines were previously inaccessible to people in countries with few resources.

MAIN BODY

The techniques needed for plant-based therapeutic production are currently available. Viral expression vectors based on plant viruses have greatly enhanced plant-made therapeutic production and have been exploited to produce a variety of proteins of industrial, pharmaceutical and agribusiness interest. Some neglected tropical diseases occurring exclusively in the developing world have found solutions through plant bioreactor technology. Plant viral expression vectors have been reported in the production of therapeutics against these diseases occurring exclusively in the third world, and some virus-derived antigens produced in plants exhibit appropriate antigenicity and immunogenicity. However, all advances in the use of plants as bioreactors have been made by companies in Europe and America. The developing world is still far from acquiring this technology, although plant viral expression vectors may provide crucial help to overcome neglected diseases.

CONCLUSION

Today, interest in these tools is rising, and viral amplicons made in and for Africa are in progress. This review describes the biotechnological advances in the field of plant bioreactors, highlights factors restricting access to this technology by those who need it most and proposes a solution to overcome these limitations.

Cholesterol-modified lignin: A new avenue for green nanoparticles, meltable materials, and drug delivery

Two fractions of kraft lignin of low and high molecular weight were reacted with cholesteryl chloroformate (Chol.Cl) to produce a modified lignin that demonstrated very high hydrophobicity. Surprisingly, both fractions displayed discernible melting points as opposed to the starting lignin. The suspension in water also gave rise to nanoparticles that displayed sizes in the range of 200-500 nm that were shown to satisfactorily load and release folic acid, a representative hydrophobic molecule, within the context of drug delivery.

Nano-and Micromotors Designed for Cancer Therapy

Research on nano- and micromotors has evolved into a frequently cited research area with innovative technology envisioned for one of current humanities' most deadly problems: cancer. The development of cancer targeting drug delivery strategies involving nano-and micromotors has been a vibrant field of study over the past few years. This review aims at categorizing recent significant results, classifying them according to the employed propulsion mechanisms starting from chemically driven micromotors, to field driven and biohybrid approaches. In concluding remarks of section 2, we give an insight into shape changing micromotors that are envisioned to have a significant contribution. Finally, we critically discuss which important aspects still have to be addressed and which challenges still lie ahead of us.

Implications of nanotechnology for the treatment of cancer: Recent advances

The use of nanoparticles dramatically increases the safety and efficacy of the most common anticancer drugs. The main advantages of nano-drugs and delivery systems based on nano-technology are effective targeting, delayed release, increased half-life, and less systemic toxicity. The use of nano-carriers has led to significant improvements in drug delivery to targets compared with traditional administration of these drugs. In this review, the main tendencies in nano-drug formulations as well as factors limiting their use in clinical settings are discussed. Additionally, the current status of approved nano-drugs for cancer treatment is reviewed.

Future of cancer immunotherapy using plant virus-based nanoparticles

Immunotherapy potentiates a patient’s immune response against some forms of cancer, including malignant tumors. In this Special Report, we have summarized the use of nanoparticles that have been designed for use in cancer immunotherapy with particular emphasis on plant viruses. Plant virus-based nanoparticles are an ideal choice for therapeutic applications, as these nanoparticles are not only capable of targeting the desired cells but also of being safely delivered to the body without posing any threat of infection. Plant viruses can be taken up by tumor cells and can be functionalized as drug delivery vehicles. This Special Report describes how the future of cancer immunotherapy could be a success through the merger of computer-based technology using plant-virus nanoparticles.

The nonpathogenic nature of plant viral nanoparticles makes them an ideal choice for therapeutic applications such as cancer. Understanding the molecular mechanisms behind the immune response to cancer has facilitated the use of nanotechnology as an effective cancer therapy. Biologically active self-replicating plant virus particles can be introduced to the bloodstream of the human body and used as effective drug delivery vehicles. This Special Report describes how a combination of computer-based technology and plant-virus nanoparticles can assist in cancer immunotherapy.

Artificial Viral Capsid Dressed Up with Human Serum Albumin

Capsid of tomato bushy stunt virus consists of an outer coat protein shell decorated on an internal skeleton comprising a β-annulus motif. We mimicked this capsid structure with our artificial viral capsid dressed up with protein. We synthesized the β-annulus peptide bearing a Cys at the C-terminal side and linked it with Cys34 of the human serum albumin (HSA) via a bismaleimide linker. The β-annulus peptide-HSA conjugate self-assembled into spherical structures of a 50-70 nm size range in the Tris-HCl buffer, with the ζ-potential of assemblies of such conjugate revealing that HSA proteins were displayed on the outer surface of the artificial viral capsid. Interestingly, the critical aggregation concentration (CAC) of the conjugate in the Tris-HCl buffer at 25 °C was approximately 0.01 μM, or 1/2500 lower than that of the unmodified β-annulus peptides, suggesting that the artificial viral capsids were stabilized via HSA modification. The present strategy of constructing protein nanocapsule by self-assembly of a β-annulus peptide-protein conjugate is simpler than that of previously reported protein nanocapsules.

Plant/Bacterial Virus-Based Drug Discovery, Drug Delivery, and Therapeutics

Viruses have recently emerged as promising nanomaterials for biotechnological applications. One of the most important applications of viruses is phage display, which has already been employed to identify a broad range of potential therapeutic peptides and antibodies, as well as other biotechnologically relevant polypeptides (including protease inhibitors, minimizing proteins, and cell/organ targeting peptides). Additionally, their high stability, easily modifiable surface, and enormous diversity in shape and size, distinguish viruses from synthetic nanocarriers used for drug delivery. Indeed, several plant and bacterial viruses (e.g., phages) have been investigated and applied as drug carriers. The ability to remove the genetic material within the capsids of some plant viruses and phages produces empty viral-like particles that are replication-deficient and can be loaded with therapeutic agents. This review summarizes the current applications of plant viruses and phages in drug discovery and as drug delivery systems and includes a discussion of the present status of virus-based materials in clinical research, alongside the observed challenges and opportunities.

Physical, chemical, and synthetic virology: Reprogramming viruses as controllable nanodevices

The fields of physical, chemical, and synthetic virology work in partnership to reprogram viruses as controllable nanodevices. Physical virology provides the fundamental biophysical understanding of how virus capsids assemble, disassemble, display metastability, and assume various configurations. Chemical virology considers the virus capsid as a chemically addressable structure, providing chemical pathways to modify the capsid exterior, interior, and subunit interfaces. Synthetic virology takes an engineering approach, modifying the virus capsid through rational, combinatorial, and bioinformatics-driven design strategies. Advances in these three subfields of virology aim to develop virus-based materials and tools that can be applied to solve critical problems in biomedicine and biotechnology, including applications in gene therapy and drug delivery, diagnostics, and immunotherapy. Examples discussed include mammalian viruses, such as adeno-associated virus (AAV), plant viruses, such as cowpea mosaic virus (CPMV), and bacterial viruses, such as Qβ bacteriophage. Importantly, research efforts in physical, chemical, and synthetic virology have further unraveled the design principles foundational to the form and function of viruses. This article is categorized under: Diagnostic Tools > Diagnostic Nanodevices Biology-Inspired Nanomaterials > Protein and Virus-Based Structures.

Small, Smaller, Nano: New Applications for Potato Virus X in Nanotechnology

Nanotechnology is an expanding interdisciplinary field concerning the development and application of nanostructured materials derived from inorganic compounds or organic polymers and peptides. Among these latter materials, proteinaceous plant virus nanoparticles have emerged as a key platform for the introduction of tailored functionalities by genetic engineering and conjugation chemistry. Tobacco mosaic virus and Cowpea mosaic virus have already been developed for bioimaging, vaccination and electronics applications, but the flexible and filamentous Potato virus X (PVX) has received comparatively little attention. The filamentous structure of PVX particles allows them to carry large payloads, which are advantageous for applications such as biomedical imaging in which multi-functional scaffolds with a high aspect ratio are required. In this context, PVX achieves superior tumor homing and retention properties compared to spherical nanoparticles. Because PVX is a protein-based nanoparticle, its unique functional properties are combined with enhanced biocompatibility, making it much more suitable for biomedical applications than synthetic nanomaterials. Moreover, PVX nanoparticles have very low toxicity in vivo, and superior pharmacokinetic profiles. This review focuses on the production of PVX nanoparticles engineered using chemical and/or biological techniques, and describes current and future opportunities and challenges for the application of PVX nanoparticles in medicine, diagnostics, materials science, and biocatalysis.

A protein nanocontainer targeting epithelial cancers: rational engineering, biochemical characterization, drug loading and cell delivery

The development of drug delivery and imaging tools is a major challenge in human health, in particular in cancer pathologies. This work describes the optimization of a protein nanocontainer, belonging to the lectin protein family, for its use in epithelial cancer diagnosis and treatment. Indeed, it specifically targets a glycosidic marker, the T antigen, which is known to be characteristic of epithelial cancers. Its quaternary structure reveals a large hydrated inner cavity able to transport small therapeutic molecules. Optimization of the nanocontainer by site directed mutagenesis allowed controlling loading and release of confined drugs. Doxorubicin confinement was followed, both theoretically and experimentally, and provided a proof of concept for the use of this nanocontainer as a vectorization system. In OVCAR-3 cells, a human ovarian adenocarcinoma cell line that expresses the T antigen, the drug was observed to be delivered inside late endosomes/lysosomes. These results show that this new type of vectorization and imaging device opens new exciting perspectives in nano-theranostic approaches.

Plant Viruses in Plant Molecular Pharming: Toward the Use of Enveloped Viruses

Plant molecular pharming has emerged as a reliable platform for recombinant protein expression providing a safe and low-cost alternative to bacterial and mammalian cells-based systems. Simultaneously, plant viruses have evolved from pathogens to molecular tools for recombinant protein expression, chimaeric viral vaccine production, and lately, as nanoagents for drug delivery. This review summarizes the genesis of viral vectors and agroinfection, the development of non-enveloped viruses for various biotechnological applications, and the on-going research on enveloped plant viruses.

Development and characterization of folic acid-functionalized apoferritin as a delivery vehicle for epirubicin against MCF-7 breast cancer cells

Epirubicin (Epr) is an effective chemotherapeutic drug; however, the clinical amenability of Epr is limited by its highly toxic interaction with normal cells. This toxicity can be decreased by utilizing nanocarriers and targeted drug delivery systems. This work describes an approach for the delivery of Epr via encapsulation in the horse spleen apoferritin (HsAFr) cavity. The encapsulation was achieved by the disassembling of apoferritin into subunits at pH 2 followed by its reformation at pH 7.4 in the presence of Epr. The surface of HsAFr-encapsulated Epr was modified with folic acid (FA) for optimal targeting of breast cancer cells (MCF-7). The use of FA to functionalize HsAFr could enhance the cellular uptake efficiency via FA-receptor-mediated endocytosis. UV-vis spectroscopy, fluorescence spectroscopy, circular dichroism (CD) and transmission electron microscopy (TEM) were utilized for structural characterization of the HsAFr-Epr and HsAFr-Epr-FA complexes. The comparison of the anti-cancer activities across the HsAFr-Epr-FA complex and the free Epr drug was performed using the MTT viability assay on MCF-7.

Virus-like nanoparticles as a novel delivery tool in gene therapy

Viruses are considered as natural nanomaterials as they are in the size range of 20-500 nm with a genetical material either DNA or RNA, which is surrounded by a protein coat capsid. Recently, the field of virus nanotechnology is gaining significant attention from researchers. Attention is given to the utilization of viruses as nanomaterials for medical, biotechnology and energy applications. Removal of genetic material from the viral capsid creates empty capsid for drug incorporation and coating the capsid protein crystals with antibodies, enzymes or aptamers will enhance their targeted drug deliver efficiency. Studies reported that these virus-like nanoparticles have been used in delivering drugs for cancer. It is also used in imaging and sensory applications for various diseases. However, there is reservation among researchers to utilize virus-like nanoparticles in targeted delivery of genes in gene therapy, as there is a possibility of using virus-like nanoparticles for targeted gene delivery. In addition, other biomedical applications that are explored using virus-like nanoparticles and the probable mechanism of delivering genes.

Application of Plant Viruses as a Biotemplate for Nanomaterial Fabrication

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

Bioengineering Strategies for Protein-Based Nanoparticles

In recent years, the practical application of protein-based nanoparticles (PNPs) has expanded rapidly into areas like drug delivery, vaccine development, and biocatalysis. PNPs possess unique features that make them attractive as potential platforms for a variety of nanobiotechnological applications. They self-assemble from multiple protein subunits into hollow monodisperse structures; they are highly stable, biocompatible, and biodegradable; and their external components and encapsulation properties can be readily manipulated by chemical or genetic strategies. Moreover, their complex and perfect symmetry have motivated researchers to mimic their properties in order to create de novo protein assemblies. This review focuses on recent advances in the bioengineering and bioconjugation of PNPs and the implementation of synthetic biology concepts to exploit and enhance PNP's intrinsic properties and to impart them with novel functionalities.

Bioengineered cellular and cell membrane-derived vehicles for actively targeted drug delivery: So near and yet so far

Cellular carriers for drug delivery are attractive alternatives to synthetic nanoparticles owing to their innate homing/targeting abilities. Here, we review molecular interactions involved in the homing of Mesenchymal stem cells (MSCs) and other cell types to understand the process of designing and engineering highly efficient, actively targeting cellular vehicles. In addition, we comprehensively discuss various genetic and non-genetic strategies and propose futuristic approaches of engineering MSC homing using micro/nanotechnology and high throughput small molecule screening. Most of the targeting abilities of a cell come from its plasma membrane, thus, efforts to harness cell membranes as drug delivery vehicles are gaining importance and are highlighted here. We also recognize and report the lack of detailed characterization of cell membranes in terms of safety, structural integrity, targeting functionality, and drug transport. Finally, we provide insights on future development of bioengineered cellular and cell membrane-derived vesicles for successful clinical translation.

A Dual Bioconjugated Virus-Like Nanoparticle as a Drug Delivery System and Comparison with a pH-Responsive Delivery System

Modifications of virus-like nanoparticles (VLNPs) using chemical conjugation techniques have brought the field of virology closer to nanotechnology. The huge surface area to volume ratio of VLNPs permits multiple copies of a targeting ligand and drugs to be attached per nanoparticle. By exploring the chemistry of truncated hepatitis B core antigen (tHBcAg) VLNPs, doxorubicin (DOX) was coupled covalently to the external surface of these nanoparticles via carboxylate groups. About 1600 DOX molecules were conjugated on each tHBcAg VLNP. Then, folic acid (FA) was conjugated to lysine residues of tHBcAg VLNPs to target the nanoparticles to cancer cells over-expressing folic acid receptor (FR). The result demonstrated that the dual bioconjugated tHBcAg VLNPs increased the accumulation and uptake of DOX in the human cervical and colorectal cancer cell lines compared with free DOX, resulting in enhanced cytotoxicity of DOX towards these cells. The fabrication of these dual bioconjugated nanoparticles is simple, and drugs can be easily conjugated with a high coupling efficacy to the VLNPs without any limitation with respect to the cargo’s size or charge, as compared with the pH-responsive system based on tHBcAg VLNPs. These dual bioconjugated nanoparticles also have the potential to be modified for other combinatorial drug deliveries.

Plant virus nanoparticles: Novel and robust nanocarriers for drug delivery and imaging

Nanoparticles have been gained much attention for biomedical applications. A promising type of nanocarriers is viral nanoparticles (VNPs) which are natural bio-nanomaterials derived from different type of viruses. Amongst VNPs, plant VNPs present several pros over general nanoparticles such as liposomes, dendrimers or quantum dots. Some of these advantages include: degradability, safety for human, known structures to atomic level, possibility of attaching ligand with vigorous control on structure, availability for genetic and chemical manipulations and very flexible methods to prepare them. Variety of plant viruses have been modified by chemical and genetic modification of their inner cavities and their outer-surfaces. These modifications provide suitable sites for attachment of markers and drug molecules for vascular imaging and tumor targeting. In this review a brief description of plant virus nanoparticles and their biomedical applications especially in drug delivery is provided. The methods of loading cargos in these VNPs and their final biofate are also reviewed.

Repurposing Plant Virus Nanoparticles

Plants have been explored for many years as inexpensive and versatile platforms for the generation of vaccines and other biopharmaceuticals. Plant viruses have also been engineered to either express subunit vaccines or act as epitope presentation systems. Both icosahedral and helical, filamentous-shaped plant viruses have been used for these purposes. More recently, plant viruses have been utilized as nanoparticles to transport drugs and active molecules into cancer cells. The following review describes the use of both icosahedral and helical plant viruses in a variety of new functions against cancer. The review illustrates the breadth of variation among different plant virus nanoparticles and how this impacts the immune response.

In Vitro-Reassembled Plant Virus-Like Particles of Hibiscus Chlorotic Ringspot Virus (HCRSV) as Nano-Protein Cages for Drugs

Spherical shaped plant viruses require a precise quantity, size, and shape of their coat protein subunits to assemble into virions of identical dimensions. The capsid of spherical plant virus particles typically consists of a precisely shaped protein cage, which in many cases is assembled from identical coat protein subunits. In addition to packaging the viral genome, such protein cages may have the capacity to load foreign compounds, either large molecules (e.g., polymers) or small molecules (e.g., anticancer chemotherapy drugs). Therefore, reassembled protein cages of suitable viruses can serve as carriers for cargo loading, which is what makes them an attractive platform for drug delivery. Here we describe methods to reassemble plant virus-like particles of hibiscus chlorotic ringspot virus (HCRSV) as nano-protein cages including the techniques to purify coat protein, prepare virus-like particles, and load them with foreign compounds.

Physalis Mottle Virus-Like Particles as Nanocarriers for Imaging Reagents and Drugs

Platform technologies based on plant virus nanoparticles (VNPs) and virus-like particles (VLPs) are attracting the attention of researchers and clinicians because the particles are biocompatible, biodegradable, noninfectious in mammals, and can readily be chemically and genetically engineered to carry imaging agents and drugs. When the Physalis mottle virus (PhMV) coat protein is expressed in Escherichia coli, the resulting VLPs are nearly identical to the viruses formed in vivo. Here, we isolated PhMV-derived VLPs from ClearColi cells and carried out external and internal surface modification with fluorophores using reactive lysine-N-hydroxysuccinimide ester and cysteine-maleimide chemistries, respectively. The uptake of dye-labeled particles was tested in a range of cancer cells and monitored by confocal microscopy and flow cytometry. VLPs labeled internally on cysteine residues were taken up with high efficiency by several cancer cell lines and were colocalized with the endolysosomal marker LAMP-1 within 6 h, whereas VLPs labeled externally on lysine residues were taken up with lower efficiency, probably reflecting differences in surface charge and the propensity to bind to the cell surface. The infusion of dye and drug molecules into the cavity of the VLPs revealed that the photosensitizer (PS), Zn-EpPor, and the drugs crystal violet, mitoxantrone (MTX), and doxorubicin (DOX) associated stably with the carrier via noncovalent interactions. We confirmed the cytotoxicity of the PS-PhMV and DOX-PhMV particles against prostate cancer, ovarian and breast cancer cell lines, respectively. Our results show that PhMV-derived VLPs provide a new platform technology for the delivery of imaging agents and drugs, with preferential uptake into cancer cells. These particles could therefore be developed as multifunctional tools for cancer diagnosis and therapy.