Nanoengineering artificial lipid envelopes around adenovirus by self-assembly

Joining Forces: The Combined Application of Therapeutic Viruses and Nanomaterials in Cancer Therapy

Cancer, on a global scale, presents a monumental challenge to our healthcare systems, posing a significant threat to human health. Despite the considerable progress we have made in the diagnosis and treatment of cancer, realizing precision cancer therapy, reducing side effects, and enhancing efficacy remain daunting tasks. Fortunately, the emergence of therapeutic viruses and nanomaterials provides new possibilities for tackling these issues. Therapeutic viruses possess the ability to accurately locate and attack tumor cells, while nanomaterials serve as efficient drug carriers, delivering medication precisely to tumor tissues. The synergy of these two elements has led to a novel approach to cancer treatment-the combination of therapeutic viruses and nanomaterials. This advantageous combination has overcome the limitations associated with the side effects of oncolytic viruses and the insufficient tumoricidal capacity of nanomedicines, enabling the oncolytic viruses to more effectively breach the tumor's immune barrier. It focuses on the lesion site and even allows for real-time monitoring of the distribution of therapeutic viruses and drug release, achieving a synergistic effect. This article comprehensively explores the application of therapeutic viruses and nanomaterials in tumor treatment, dissecting their working mechanisms, and integrating the latest scientific advancements to predict future development trends. This approach, which combines viral therapy with the application of nanomaterials, represents an innovative and more effective treatment strategy, offering new perspectives in the field of tumor therapy.

Lung-Targeted Transgene Expression of Nanocomplexed Ad5 Enhances Immune Response in the Presence of Preexisting Immunity

Recombinant adenovirus serotype 5 (Ad5) vector has been widely applied in vaccine development targeting infectious diseases, such as Ebola virus disease and coronavirus disease 2019 (COVID-19). However, the high prevalence of preexisting anti-vector immunity compromises the immunogenicity of Ad5-based vaccines. Thus, there is a substantial unmet need to minimize preexisting immunity while improving the insert-induced immunity of Ad5 vectors. Herein, we address this need by utilizing biocompatible nanoparticles to modulate Ad5-host interactions. We show that positively charged human serum albumin nanoparticles ((+)HSAnp), which are capable of forming a complex with Ad5, significantly increase the transgene expression of Ad5 in both coxsackievirus-adenovirus receptor-positive and -negative cells. Furthermore, in charge- and dose-dependent manners, Ad5/(+)HSAnp complexes achieve robust (up to 227-fold higher) and long-term (up to 60 days) transgene expression in the lungs of mice following intranasal instillation. Importantly, in the presence of preexisting anti-Ad5 immunity, complexed Ad5-based Ebola and COVID-19 vaccines significantly enhance antigen-specific humoral response and mucosal immunity. These findings suggest that viral aggregation and charge modification could be leveraged to engineer enhanced viral vectors for vaccines and gene therapies.

Controlling the surface charge of simple viruses

The vast majority of plant viruses are unenveloped, i.e., they lack a lipid bilayer that is characteristic of most animal viruses. The interactions between plant viruses, and between viruses and surfaces, properties that are essential for understanding their infectivity and to their use as bionanomaterials, are largely controlled by their surface charge, which depends on pH and ionic strength. They may also depend on the charge of their contents, i.e., of their genes or-in the instance of virus-like particles-encapsidated cargo such as nucleic acid molecules, nanoparticles or drugs. In the case of enveloped viruses, the surface charge of the capsid is equally important for controlling its interaction with the lipid bilayer that it acquires and loses upon leaving and entering host cells. We have previously investigated the charge on the unenveloped plant virus Cowpea Chlorotic Mottle Virus (CCMV) by measurements of its electrophoretic mobility. Here we examine the electrophoretic properties of a structurally and genetically closely related bromovirus, Brome Mosaic Virus (BMV), of its capsid protein, and of its empty viral shells, as functions of pH and ionic strength, and compare them with those of CCMV. From measurements of both solution and gel electrophoretic mobilities (EMs) we find that the isoelectric point (pI) of BMV (5.2) is significantly higher than that of CCMV (3.7), that virion EMs are essentially the same as those of the corresponding empty capsids, and that the same is true for the pIs of the virions and of their cleaved protein subunits. We discuss these results in terms of current theories of charged colloidal particles and relate them to biological processes and the role of surface charge in the design of new classes of drug and gene delivery systems.

Materials promoting viral gene delivery

Therapeutic viral gene delivery is an emerging technology which aims to correct genetic mutations by introducing new genetic information to cells either to correct a faulty gene or to initiate cell death in oncolytic treatments. In recent years, significant scientific progress has led to several clinical trials resulting in the approval of gene therapies for human treatment. However, successful therapies remain limited due to a number of challenges such as inefficient cell uptake, low transduction efficiency (TE), limited tropism, liver toxicity and immune response. To adress these issues and increase the number of available therapies, additives from a broad range of materials like polymers, peptides, lipids, nanoparticles, and small molecules have been applied so far. The scope of this review is to highlight these selected delivery systems from a materials perspective.

Biosilicified oncolytic adenovirus for cancer viral gene therapy

Oncolytic adenoviruses (OAs) have shown great potential for cancer viral gene therapy in clinical studies. To date, clinical trials have shown that the curative efficacy of OAs is still limited by hepatic sequestration and preexisting neutralizing antibodies (nAbs), which decrease the accumulation of the OAs in tumors. Herein, with the biosilicification method, we encapsulated an OA encoding the anticancer gene Trail (OA-Trail) with silica, which significantly improved virus distribution and tumor inhibition. In vitro and in vivo results indicated that compared with the native OA, biosilicified OA-Trail (OA-Trail@SiO₂) showed significantly reduced viral clearance in the liver and evaded nAb degradation, inducing an efficacious anticancer effect under the premise of biocompatibility. These achievements present an alternative strategy involving biosilicification for enhanced OA-based cancer gene therapy.

Enveloped artificial viral capsids self-assembled from anionic β-annulus peptide and cationic lipid bilayer

Anionic artificial viral capsids were self-assembled from β-annulus-EE peptide, then complexed with lipid-bilayer-containing cationic lipids via electrostatic interaction to form enveloped artificial viral capsids. The critical aggregation concentration of the enveloped artificial viral capsid was significantly lower than that of the uncomplexed artificial viral capsid, indicating that the lipid bilayer stabilised the capsid structure.

Strategies for enhancing intratumoral spread of oncolytic adenoviruses

Oncolytic viruses, effectively replicate viruses within malignant cells to lyse them without affecting normal ones, have recently shown great promise in developing therapeutic options for cancer. Adenoviruses (Ads) are one of the candidates in oncolytic virotheraoy due to its easily manipulated genomic DNA and expression of wide rane of its receptors on the various cancers. Although systematic delivery of oncolytic adenoviruses can target both primary and metastatic tumors, there are some drawbacks in the effective systematic delivery of oncolytic adenoviruses, including pre-existing antibodies and liver tropism. To overcome these limitations, intratumural (IT) administration of oncolytic viruses have been proposed. However, IT injection of Ads leaves much of the tumor mass unaffected and Ads are not able to disperse more in the tumor microenvironment (TME). To this end, various strategies have been developed to enhance the IT spread of oncolytic adenoviruses, such as using extracellular matrix degradation enzymes, junction opening peptides, and fusogenic proteins. In the present paper, we reviewed different oncolytic adenoviruses, their application in the clinical trials, and strategies for enhancing their IT spread.

Osmotic stress and pore nucleation in charged biological nanoshells and capsids

A model system is proposed to investigate the chemical equilibrium and mechanical stability of biological spherical-like nanoshells in contact with an aqueous solution with added dissociated electrolyte of a given concentration. The ionic chemical equilibrium across the permeable shell is investigated in the framework of an accurate Density Functional Theory (DFT) that incorporates electrostatic and hardcore correlations beyond the traditional mean-field (e.g., Poisson-Boltzmann) limit. The accuracy of the theory is tested by a direct comparison with Monte Carlo (MC) simulations. A simple analytical expression is then deduced which clearly highlights the entropic, electrostatic, and self-energy contributions to the osmotic stress over the shell in terms of the calculated ionic profiles. By invoking a continuum mean-field elastic approach to account for the shell surface stress upon osmotic stretching, the mechanical equilibrium properties of the shell under a wide variety of ionic strengths and surface charges are investigated. The model is further coupled to a continuum mechanical approach similar in structure to a Classical Nucleation Theory (CNT) to address the question of mechanical stability of the shells against a pore nucleation. This allows us to construct a phase diagram which delimits the mechanical stability of capsids for different ionic strengths and shell surface charges.

The practical self-targeted oncolytic adenoviral nanosphere based on immuno-obstruction method via polyprotein surface precipitation technique enhances transfection efficiency for virotherapy

Recent developments in tumour treatment had focused on virotherapies that were currently revolutionising new innovated treatment pathways. This study focused on the fabrication of oncolytic adenoviral vector (Ad) nanosphere that self-targeted at lung tumour cells (A549), utilising the immune response for upper respiratory tract infection, caused by the Ad infection. This system was dependent upon T-cell immune response, surface charge and blood metabolism. Oncolytic Ad attacked lung A549 tumour cells by incorporated its own DNA to replace A549's, the triggered immune response generated T-cells also further attack A549. Direct Ad injection was demonstrated to be lethal and prohibited in vivo. In this research a multifunctional principal using polyprotein surface precipitation technique (PSP) whist maintaining biological controls for self-assembly polyprotein Ad nanosphere both biocompatible and reproducible, was demonstrated as a result of the enhanced transfection efficiency and a successful multifunctional drug delivery system for virotherapy.

Designer Oncolytic Adenovirus: Coming of Age

The licensing of talimogene laherparepvec (T-Vec) represented a landmark moment for oncolytic virotherapy, since it provided unequivocal evidence for the long-touted potential of genetically modified replicating viruses as anti-cancer agents. Whilst T-Vec is promising as a locally delivered virotherapy, especially in combination with immune-checkpoint inhibitors, the quest continues for a virus capable of specific tumour cell killing via systemic administration. One candidate is oncolytic adenovirus (Ad); it’s double stranded DNA genome is easily manipulated and a wide range of strategies and technologies have been employed to empower the vector with improved pharmacokinetics and tumour targeting ability. As well characterised clinical and experimental agents, we have detailed knowledge of adenoviruses’ mechanisms of pathogenicity, supported by detailed virological studies and in vivo interactions. In this review we highlight the strides made in the engineering of bespoke adenoviral vectors to specifically infect, replicate within, and destroy tumour cells. We discuss how mutations in genes regulating adenoviral replication after cell entry can be used to restrict replication to the tumour, and summarise how detailed knowledge of viral capsid interactions enable rational modification to eliminate native tropisms, and simultaneously promote active uptake by cancerous tissues. We argue that these designer-viruses, exploiting the viruses natural mechanisms and regulated at every level of replication, represent the ideal platforms for local overexpression of therapeutic transgenes such as immunomodulatory agents. Where T-Vec has paved the way, Ad-based vectors now follow. The era of designer oncolytic virotherapies looks decidedly as though it will soon become a reality.

Nano/Micro Formulations for Bacteriophage Delivery

Encapsulation methodologies allow the protection of bacteriophages for overcoming critical environmental conditions. Moreover, they improve the stability and the controlled delivery of bacteriophages which is of great innovative value in bacteriophage therapy. Here, two different encapsulation methodologies of bacteriophages are described using two biocompatible materials: a lipid cationic mixture and a combination of alginate with the antacid CaCO₃. To perform bacteriophage encapsulation, a purified lysate highly concentrated (around 10¹⁰-10¹¹ pfu/mL) is necessary, and to dispose of a specific equipment. Both methodologies have been successfully applied for encapsulating Salmonella bacteriophages with different morphologies. Also, the material employed does not modify the antibacterial action of bacteriophages. Moreover, both technologies can also be adapted to any bacteriophage and possibly to any delivery route for bacteriophage therapy.

A multi-responsive biomimetic nano-complex platform for enhanced gene delivery

RNA interference (RNAi) is widely regarded as a promising technology for disease treatment, yet one major obstacle for its clinical application is the lack of enhanced siRNA delivery vehicles to circumvent complex extra- and intracellular barriers.

Optimization and physicochemical characterization of a cationic lipid-phosphatidylcholine mixed emulsion formulated as a highly efficient vehicle that facilitates adenoviral gene transfer

Cationic lipid-based nanoparticles enhance viral gene transfer by forming electrostatic complexes with adenoviral vectors. We recently demonstrated the superior complexation capabilities of 1,2-dioleoyl-3-trimethylammonium propane (DOTAP) emulsion compared with a liposomal counterpart but the cytotoxicity of DOTAP emulsions remained a challenge. The present study is aimed at formulating an emulsion capable of acting as a highly effective viral gene transfer vehicle with reduced cytotoxicity and to physicochemically characterize the structures of virus-emulsion complexes in comparison with virus-liposome complexes when the only difference between emulsions and liposomes was the presence or absence of inner oil core. The emulsion formulation was performed by 1) reducing the content of DOTAP while increasing the content of zwitterionic lipid 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC), and 2) optimizing the oil content. The complexation capability of formulated DOTAP:DMPC mixed emulsions was similar to those of emulsions containing DOTAP alone while displaying significantly lower cytotoxicity. The complexation capabilities of the DOTAP:DMPC mixed emulsion were serum-compatible and were monitored in a variety of cell types, whereas its liposomal counterpart was totally ineffective. Characterization by scanning electron microscopy, transmission electron microscopy, atomic force microscopy, and dynamic light scattering studies indicated that the optimized emulsions spontaneously surrounded the virus particles to generate emulsions that encapsulated the viral particles, whereas viral particles merely attached to the surfaces of the counterpart liposomes to form multiviral aggregates. Overall, these studies demonstrated that optimized DOTAP:DMPC mixed emulsions are potentially useful for adenoviral gene delivery due to less cytotoxicity and the unique ability to encapsulate the viral particle, highlighting the importance of nanoparticle formulation.

Aminoclay as a highly effective cationic vehicle for enhancing adenovirus-mediated gene transfer through nanobiohybrid complex formation

Electrostatic complexation of adenovirus (Ad) with cationic lipids or polymers has been shown to be an effective means for overcoming the limitations of adenoviral vectors and enhancing gene-transfer efficacy. However, such complexation causes cytotoxicity, limiting the use of this strategy. The present study explored the potential of 3-aminopropyl functionalized magnesium phyllosilicate (aminoclay) as a cationic vehicle for improving Ad-mediated gene transfer without inducing cytotoxicity. Aminoclay complexation produced a dose-dependent increase in Ad-mediated transgene expression in both Ad infection-sensitive and -refractory cells, thereby greatly lowering the Ad dose required for transgene expression. Unlike the case for cationic lipids (Lipofectamine) or polymers (Polybrene), the enhancement effect of aminoclay was not accompanied by significant cytotoxicity regardless of cell lines and it was not observed for nonviral plasmid vectors. Physical characterization studies revealed that nanobiohybrid complexes formed between aminoclay and Ad particles through electrostatic interactions, creating aggregates of Ad particles whose surface was shielded with aminoclay nanosheet oligomers. It appears that aminoclay complexation changes the surface charge of Ad particles from a negative to a highly positive value and thus increases Ad binding to cellular membranes, thereby providing an additional cellular entry mechanism, namely caveolae-dependent endocytosis. Aminoclay-Ad nanobiohybrids may serve as a next-generation efficient, versatile and biocompatible gene-delivery carrier.

STATEMENT OF SIGNIFICANCE

Electrostatic complexation of adenovirus with cationic materials has been shown to be an effective means for enhancing gene-transfer efficacy in vitro. However, such complexation causes cytotoxicity, limiting the use of this strategy. The present study explored the potential of a synthesized organoclay 3-aminopropyl functionalized magnesium phyllosilicate (aminoclay) as a cationic vehicle for improving Ad-mediated gene transfer. Our data indicate that nanobiohybrid complexes form between aminoclay and Ad particles through electrostatic interactions, thereby greatly enhancing Ad-mediated gene transfer. Unlike the case for either cationic lipids or cationic polymers, the enhancement effect of aminoclay was not accompanied by significant cytotoxicity regardless of cell lines. Our findings in this work highlight that aminoclay-Ad nanobiohybrids may serve as a next-generation efficient and biocompatible gene-delivery carrier.

Oncolytic Adenovirus Complexes Coated with Lipids and Calcium Phosphate for Cancer Gene Therapy

Oncolytic adenovirus (Onco^Ad) is a promising therapeutic agent for treating cancer. However, the therapeutic potential of Onco^Ad is hindered by hepatic sequestration and the host immune response in vivo. Here, we constructed a PEG/Lipids/calcium phosphate (CaP)-Onco^Ad (PLC-Onco^Ad) delivery system for ZD55-IL-24, an oncolytic adenovirus that carries the IL-24 gene. The negatively charged PLC-ZD55-IL-24 were disperse and resisted serum-induced aggregation. Compared to naked ZD55-IL-24, the systemic administration of PLC-ZD55-IL-24 in BALB/c mice resulted in reduced liver sequestration and systemic toxicity and evaded the innate immune response. In addition, masking the surface of Onco^Ad protected it from neutralization by pre-existing neutralizing antibody. PLC-Onco^Ad achieved efficient targeted delivery in Huh-7-bearing nude mice, and intravenous administration of a high dose of PLC-ZD55-IL-24 increased therapeutic efficacy without inducing toxicity. The developed PLC-Onco^Ad delivery system represents a promising improvement for oncolytic adenovirus-based cancer gene therapy in vivo.

Evolving lessons on nanomaterial-coated viral vectors for local and systemic gene therapy

Viral vectors are promising gene carriers for cancer therapy. However, virus-mediated gene therapies have demonstrated insufficient therapeutic efficacy in clinical trials due to rapid dissemination to nontarget tissues and to the immunogenicity of viral vectors, resulting in poor retention at the disease locus and induction of adverse inflammatory responses in patients. Further, the limited tropism of viral vectors prevents efficient gene delivery to target tissues. In this regard, modification of the viral surface with nanomaterials is a promising strategy to augment vector accumulation at the target tissue, circumvent the host immune response, and avoid nonspecific interactions with the reticuloendothelial system or serum complement. In the present review, we discuss various chemical modification strategies to enhance the therapeutic efficacy of viral vectors delivered either locally or systemically. We conclude by highlighting the salient features of various nanomaterial-coated viral vectors and their prospects and directions for future research.

Viral nanoparticles, noble metal decorated viruses and their nanoconjugates

Virus-based nanotechnology has generated interest in a number of applications due to the specificity of virus interaction with inorganic and organic nanoparticles. A well-defined structure of virus due to its multifunctional proteinaceous shell (capsid) surrounding genomic material is a promising approach to obtain nanostructured materials. Viruses hold great promise in assembling and interconnecting novel nanosized components, allowing to develop organized nanoparticle assemblies. Due to their size, monodispersity, and variety of chemical groups available for modification, they make a good scaffold for molecular assembly into nanoscale devices. Virus based nanocomposites are useful as an engineering material for the construction of smart nanoobjects because of their ability to associate into desired structures including a number of morphologies. Viruses exhibit the characteristics of an ideal template for the formation of nanoconjugates with noble metal nanoparticles. These bioinspired systems form monodispersed units that are highly amenable through genetic and chemical modifications. As nanoscale assemblies, viruses have sophisticated yet highly ordered structural features, which, in many cases, have been carefully characterized by modern structural biological methods. Plant viruses are increasingly being used for nanobiotechnology purposes because of their relative structural and chemical stability, ease of production, multifunctionality and lack of toxicity and pathogenicity in animals or humans. The multifunctional viruses interact with nanoparticles and other functional additives to the generation of bioconjugates with different properties – possible antiviral and antibacterial activities.

Nanoparticles incorporating pH-responsive surfactants as a viable approach to improve the intracellular drug delivery

The pH-responsive delivery systems have brought new advances in the field of functional nanodevices and might allow more accurate and controllable delivery of specific cargoes, which is expected to result in promising applications in different clinical therapies. Here we describe a family of chitosan-TPP (tripolyphosphate) nanoparticles (NPs) for intracellular drug delivery, which were designed using two pH-sensitive amino acid-based surfactants from the family N(α),N(ε)-dioctanoyl lysine as bioactive compounds. Low and medium molecular weight chitosan (LMW-CS and MMW-CS, respectively) were used for NP preparation, and it was observed that the size distribution for NPs with LMW-CS were smaller (~168 nm) than that for NPs prepared with MMW-CS (~310 nm). Hemolysis assay demonstrated the pH-dependent biomembrane disruptional capability of the constructed NPs. The nanostructures incorporating the surfactants cause negligible membrane permeabilization at pH7.4. However, at acidic pH, prevailing in endosomes, membrane-destabilizing activity in an erythrocyte lysis assay became evident. When pH decreased to 6.6 and 5.4, hemolytic capability of chitosan NPs increased along with the raise of concentration. Furthermore, studies with cell culture showed that these pH-responsive NPs displayed low cytotoxic effects against 3T3 fibroblasts. The influence of chitosan molecular weight, chitosan to TPP weight ratio, nanoparticle size and nature of the surfactant counterion on the membrane-disruptive properties of nanoparticles was discussed in detail. Altogether, the results achieved here showed that by inserting the lysine-based amphiphiles into chitosan NPs, pH-sensitive membranolytic and potentially endosomolytic nanocarriers were developed, which, therefore, demonstrated ideal feasibility for intracellular drug delivery.

Liposome-Encapsulated Bacteriophages for Enhanced Oral Phage Therapy against Salmonella spp

Bacteriophages UAB_Phi20, UAB_Phi78, and UAB_Phi87 were encapsulated in liposomes, and their efficacy in reducing Salmonella in poultry was then studied. The encapsulated phages had a mean diameter of 309 to 326 nm and a positive charge between +31.6 and +35.1 mV (pH 6.1). In simulated gastric fluid (pH 2.8), the titer of nonencapsulated phages decreased by 5.7 to 7.8 log units, whereas encapsulated phages were significantly more stable, with losses of 3.7 to 5.4 log units. The liposome coating also improved the retention of bacteriophages in the chicken intestinal tract. When cocktails of the encapsulated and nonencapsulated phages were administered to broilers, after 72 h the encapsulated phages were detected in 38.1% of the animals, whereas the nonencapsulated phages were present in only 9.5%. The difference was significant. In addition, in an in vitro experiment, the cecal contents of broilers promoted the release of the phages from the liposomes. In broilers experimentally infected with Salmonella, the daily administration of the two cocktails for 6 days postinfection conferred similar levels of protection against Salmonella colonization. However, once treatment was stopped, protection by the nonencapsulated phages disappeared, whereas that provided by the encapsulated phages persisted for at least 1 week, showing the enhanced efficacy of the encapsulated phages in protecting poultry against Salmonella over time. The methodology described here allows the liposome encapsulation of phages of different morphologies. The preparations can be stored for at least 3 months at 4°C and could be added to the drinking water and feed of animals.

Anionic Lipid, pH-Sensitive Liposome-Gold Nanoparticle Hybrids for Gene Delivery - Quantitative Research of the Mechanism

Gene therapy is a potential method for treating a large range of diseases. Gene vectors are widely used in gene therapy for promoting the gene delivery efficiency to the target cells. Here, gold nanoparticles (AuNPs) coated with dimethyldioctadecylammonium bromide (DODAB)/dioleoylphosphatidylethanolamine (DOPE) are synthesized using a facile method for a new gene vector (DODAB/DOPE-AuNPs), which possess 3- and 1.5-fold higher transfection efficiency than those of DODAB-AuNPs and a commercial transfection agent, respectively. Meanwhile, it is nontoxic with concentrations required for effective gene delivery. Imaging and quantification studies of cellular uptake reveal that DOPE increases gene copies in cells, which may be attributed to the smaller size of AuNPs/DNA complexes. The dissociation efficiency of DNA from the endocytic pathway is quantified by incubating with different buffers and investigated directly in the cells. The results suggest that DOPE increases the internalization of AuNPs/DNA complexes and promotes DNA release from early endosomes for the vector is sensitive to the anionic lipid membrane and the decreasing pH along the endocytic pathway. The new vector contains the potential to be the new alternative as gene delivery vector for biomedical applications.

Tumor-targeting and pH-sensitive lipoprotein-mimic nanocarrier for targeted intracellular delivery of paclitaxel

In the present study, we constructed a tumor-targeting and pH-sensitive lipoprotein-mimic nanocarrier containing paclitaxel (FA-BSA-LC/DOPE-PTX), by adding 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine (DOPE) and oleic acid as pH-sensitive components into the formulation of lipid core and then coating with folic acid modified bovine serum albumin (FA-BSA) for tumor targeting activity. In vitro drug release study demonstrated that paclitaxel (PTX) was released from FA-BSA-LC/DOPE in a pH-dependent manner. The vitro cytotoxicity assays showed that all the blank nanocarriers were nontoxic. However, MTT assay showed that FA-BSA-LC/DOPE-PTX was highly cytotoxic. Cellular uptake experiments analyzed with flow cytometry and laser scan confocal microscope (LSCM) revealed that FA-BSA-LC/DOPE was taken up in great amount via folate receptor-mediated endocytosis and pH-sensitive release of drug to cytoplasm. Furthermore, the study of intracellular drug release behavior demonstrated that the FA-BSA-LC/DOPE escaped from lysosomes and released drug into cytoplasm. The in vivo targeting activity showed that the nanocarrier selectively targeted tumor and had long residence time for BSA layer increased the stability in blood. Moreover, FA-BSA-LC/DOPE-PTX produced very marked anti-tumor activity in tumor-bearing mice in vivo. Therefore, FA-BSA-LC/DOPE as biocompatible, tumor-targeting and pH-sensitive lipoprotein-mimic nanocarrier is a promising system for effective intracellular delivery of PTX to tumor.

Preparation of adenovirus-templated gold nanoshells and a study of their photothermal therapy efficacy

Adenovirus-templated gold nanoshells not only show good biocompatibility but also have excellent photothermal therapy efficacy against tumors.

Development of dual-activity vectors by co-envelopment of adenovirus and SiRNA in artificial lipid bilayers

Gene therapy with human adenovirus type 5 (Ad5) has been extensively explored for the treatment of diseases resistant to traditional therapies. Intravenous administration leads to rapid clearance from blood circulation and high liver accumulation, which restrict the use of Ad-based vectors in clinical gene therapy protocols that involve systemic administration. We have previously proposed that such limitations can be improved by engineering artificial lipid envelopes around Ad and designed a variety of artificial lipid bilayer envelopes around the viral capsid. In this study, we sought to explore further opportunities that the artificially enveloped virus constructs could offer, by designing a previously unreported gene therapy vector by simultaneous envelopment of Ad and siRNA within the same lipid bilayer. Such a dual-activity vector can offer efficacious therapy for different genetic disorders where both turning on and switching off genes would be needed. Dynamic light scattering, transmission electron microscopy and atomic force microscopy were used to characterize these vectors. Agarose gel electrophoresis, Ribo green and dot blot assays showed that siRNA and Ad virions can be enveloped together within lipid bilayers at high envelopment efficiency. Cellular uptake and in vitro transfection experiments were carried out to show the feasibility of combining siRNA-mediated gene silencing with viral gene transfer using these newly designed dual-activity vectors.

The evolution of adenoviral vectors through genetic and chemical surface modifications

A long time has passed since the first clinical trial with adenoviral (Ad) vectors. Despite being very promising, Ad vectors soon revealed their limitations in human clinical trials. The pre-existing immunity, the marked liver tropism and the high toxicity of first generation Ad (FG-Ad) vectors have been the main challenges for the development of new approaches. Significant effort toward the development of genetically and chemically modified adenoviral vectors has enabled researchers to create more sophisticated vectors for gene therapy, with an improved safety profile and a higher transduction ability of different tissues. In this review, we will describe the latest findings in the high-speed, evolving field of genetic and chemical modifications of adenoviral vectors, a field in which different disciplines, such as biomaterial research, virology and immunology, co-operate synergistically to create better gene therapy tools for modern challenges.

Beyond Gene Delivery: Strategies to Engineer the Surfaces of Viral Vectors

Viral vectors have been extensively studied due to their great transduction efficiency compared to non-viral vectors. These vectors have been used extensively in gene therapy, enabling the comprehension of, not only the advantages of these vectors, but also the limitations, such as the activation of the immune system after vector administration. Moreover, the need to control the target of the vector has led to the development of chemical and non-chemical modifications of the vector surface, allowing researchers to modify the tropism and biodistribution profile of the vector, leading to the production of viral vectors able to target different tissues and organs. This review describes recent non-genetic modifications of the surfaces of viral vectors to decrease immune system activation and to control tissue targeting. The developments described herein provide opportunities for applications of gene therapy to treat acquired disorders and genetic diseases and to become useful tools in regenerative medicine.

Controlling the actuation of therapeutic nanomaterials: enabling nanoparticle-mediated drug delivery

The implementation of biofunctionalized nanoparticles (NPs) as potential therapeutic materials has seen exponential growth in recent years due to their unique ability to overcome the constraints of current medicine. This has been largely driven by significant advances on a number of basic research fronts including high-quality NP synthesis, bioconjugation, cellular delivery and the controlled release or ‘actuation’ of NP-associated cargos. Cumulatively, these are the key enabling tools for the full realization of NP-mediated drug delivery. In this review, the authors’ focus is on recent developments in methodologies for the controlled actuation of therapeutic NPs. The authors discuss the critical requirements for their integration into biological systems and highlight examples from the recent literature where controlled NP actuation has been successfully demonstrated. The current state of therapeutic NPs in the clinical setting is summarized and the article concludes with a brief perspective of how we can expect to see this emerging field develop in the coming years.

Design of hybrid lipid/retroviral-like particle gene delivery vectors

Recombinant retroviruses provide highly efficient gene delivery and the potential for stable gene expression. The retroviral envelope protein, however, is the source of significant disadvantages such as immunogenicity, poor stability (half-life of transduction activity of 5-7 h at 37 °C for amphotropic murine leukemia virus), and difficult production and purification. To address these problems, we report the construction of efficient hybrid vectors through the association of murine leukemia virus (MLV)-like particles (M-VLP) with synthetic liposomes comprising DOTAP, DOPE, and cholesterol (φ/M-VLP). We conclude that the lipid composition is a significant determinant of the transfection efficiency and uptake of φ/M-VLP in HEK293 cells with favorable compositions for transfections being those with low DOTAP, low DOPE, and high cholesterol content. Cellular uptake, however, was dependent on DOTAP content alone. By extrusion of liposomes prior to vector assembly, the size of these hybrid vectors could also be decreased to ≈300 nm, as confirmed via DLS and TEM. φ/M-VLP were also robust on storage in terms of vector size and transfection efficiency and provided stable transgene expression over a period of three weeks. We conclude that the noncovalent combination of biocompatible synthetic lipids with inactive retroviral particles to form a highly efficient hybrid vector is a significant extension to the development of novel gene delivery platforms.

The effect of artificial lipid envelopment of Adenovirus 5 (Ad5) on liver de-targeting and hepatotoxicity

Human Adenovirus type 5 (Ad5) has been extensively explored in clinical gene therapy, but its immunogenicity dramatically affects the kinetics and toxicity profile of the vector. We previously designed a variety of artificial lipid bilayer envelopes around the viral capsid to develop safer hybrid vectors. Here, we studied the interaction of enveloped Ad in cationic (DOTAP:Chol) or anionic (DOPE:CHEMS) lipid bilayers with different blood components. When Ad was enveloped by cationic lipids, significantly high levels of viral uptake in HepG2 cultured cells were achieved, independent of blood coagulation factors present. In vitro experiments also showed that artificial envelopment of Ad completely altered the affinity towards both human and murine red blood cells. After intravenous administration in BALB/c mice, real-time PCR and transgene expression studies indicated that cationic lipid envelopes significantly reduced hepatocyte transduction significantly increasing virus lung accumulation compared to DOPE:CHEMS enveloped or naked Ad. ALT/AST serum levels and liver histology showed that envelopment also improved hepatotoxicity profiles compared to naked Ad. This study suggests that artificial envelopes for Ad significantly alter the interactions with blood components and can divert viral particles from their natural liver tropism resulting in reduced hepatotoxicity.

Simultaneous gene transduction and silencing using stimuli-responsive viral/nonviral chimeric nanoparticles

Despite viral vectors' predominant use in clinical trials, due to higher gene delivery efficiency than nonviral counterparts, intrinsic immunogenicity and limited tunability for multi-modal effects are major concerns for their usage in gene therapy. An adeno-associated viral (AAV) particle was shielded with acid-degradable, siRNA-encapsulating polyketal (PK) shell, resulting in core-shell viral/nonviral chimeric nanoparticles (ChNPs). The AAV core of a ChNP is protected from immune responses by the PK shell which also facilitates the intracellular trafficking of the AAV core and efficiently releases the encapsulated siRNA into the cytoplasm. ChNPs led to significantly enhanced gene transduction, compared to unmodified free AAVs, and simultaneous silencing of a target gene, while avoiding inactivation by recognition from the immune system. Furthermore, conjugation of sialic acid (SA) on the surface of ChNPs enabled receptor-mediated targeted gene delivery to CD22-expressing cells. The ChNPs developed in this study combine the advantages of both viral and nonviral vectors and are a promising platform for targeted co-delivery of DNA and siRNA in inducing synergistic therapeutic effects by simultaneous expression and silencing of multiple genes.

Magnetically enhanced nucleic acid delivery. Ten years of magnetofection-progress and prospects

Nucleic acids carry the building plans of living systems. As such, they can be exploited to make cells produce a desired protein, or to shut down the expression of endogenous genes or even to repair defective genes. Hence, nucleic acids are unique substances for research and therapy. To exploit their potential, they need to be delivered into cells which can be a challenging task in many respects. During the last decade, nanomagnetic methods for delivering and targeting nucleic acids have been developed, methods which are often referred to as magnetofection. In this review we summarize the progress and achievements in this field of research. We discuss magnetic formulations of vectors for nucleic acid delivery and their characterization, mechanisms of magnetofection, and the application of magnetofection in viral and nonviral nucleic acid delivery in cell culture and in animal models. We summarize results that have been obtained with using magnetofection in basic research and in preclinical animal models. Finally, we describe some of our recent work and end with some conclusions and perspectives.

Liposomes: from a clinically established drug delivery system to a nanoparticle platform for theranostic nanomedicine

For decades, clinicians have used liposomes, self-assembled lipid vesicles, as nanoscale systems to deliver encapsulated anthracycline molecules for cancer treatment. The more recent proposition to combine liposomes with nanoparticles remains at the preclinical development stages; however, such hybrid constructs present great opportunities to engineer theranostic nanoscale delivery systems, which can combine simultaneous therapeutic and imaging functions. Many novel nanoparticles of varying chemical compositions are being developed in nanotechnology laboratories, but further chemical modification is often required to make these structures compatible with the biological milieu in vitro and in vivo. Such nanoparticles have shown promise as diagnostic and therapeutic tools and generally offer a large surface area that allows covalent and non-covalent surface functionalization with hydrophilic polymers, therapeutic moieties, and targeting ligands. In most cases, such surface manipulation diminishes the theranostic properties of nanoparticles and makes them less stable. From our perspective, liposomes offer structural features that can make nanoparticles biocompatible and present a clinically proven, versatile platform for further enhancement of the pharmacological and diagnostic efficacy of nanoparticles. In this Account, we describe two examples of liposome-nanoparticle hybrids developed as theranostics: liposome-quantum dot hybrids loaded with a cytotoxic drug (doxorubicin) and artificially enveloped adenoviruses. We incorporated quantum dots into lipid bilayers, which rendered them dispersible in physiological conditions. This overall vesicular structure allowed them to be loaded with doxorubicin molecules. These structures exhibited cytotoxic activity and labeled cells both in vitro and in vivo. In an alternative design, lipid bilayers assembled around non-enveloped viral nanoparticles and altered their infection tropism in vitro and in vivo with no chemical or genetic capsid modifications. Overall, we have attempted to illustrate how alternative strategies to incorporate nanoparticles into liposomal nanostructures can overcome some of the shortcomings of nanoparticles. Such hybrid structures could offer diagnostic and therapeutic combinations suitable for biomedical and even clinical applications.

Engineering biomaterial systems to enhance viral vector gene delivery

Integrating viral gene delivery with engineered biomaterials is a promising strategy to overcome a number of challenges associated with virus-mediated gene delivery, including inefficient delivery to specific cell types, limited tropism, spread of vectors to distant sites, and immune responses. Viral vectors can be combined with biomaterials either through encapsulation within the material or immobilization onto a material surface. Subsequent biomaterial-based delivery can increase the vector's residence time within the target site, thereby potentially providing localized delivery, enhancing transduction, and extending the duration of gene expression. Alternatively, physical or chemical modification of viral vectors with biomaterials can be employed to modulate the tropism of viruses or reduce inflammatory and immune responses, both of which may benefit transduction. This review describes strategies to promote viral gene delivery technologies using biomaterials, potentially providing opportunities for numerous applications of gene therapy to inherited or acquired disorders, infectious disease, and regenerative medicine.

Applications of viral nanoparticles in medicine

Several nanoparticle platforms are currently being developed for applications in medicine, including both synthetic materials and naturally occurring bionanomaterials such as viral nanoparticles (VNPs) and their genome-free counterparts, virus-like particles (VLPs). A broad range of genetic and chemical engineering methods have been established that allow VNP/VLP formulations to carry large payloads of imaging reagents or drugs. Furthermore, targeted VNPs and VLPs can be generated by including peptide ligands on the particle surface. In this article, we highlight state-of-the-art virus engineering principles and discuss recent advances that bring potential biomedical applications a step closer. Viral nanotechnology has now come of age and it will not be long before these formulations assume a prominent role in the clinic.

Nanotechnology and human health: risks and benefits

Nanotechnology is expected to be promising in many fields of medical applications, mainly in cancer treatment. While a large number of very attractive exploitations open up for the clinics, regulatory agencies are very careful in admitting new nanomaterials for human use because of their potential toxicity. The very active research on new nanomaterials that are potentially useful in medicine has not been counterbalanced by an adequate knowledge of their pharmacokinetics and toxicity. The different nanocarriers used to transport and release the active molecules to the target tissues should be treated as additives, with potential side effects of themselves or by virtue of their dissolution or aggregation inside the body. Only recently has a systematic classification of nanomaterials been proposed, posing the basis for dedicated modeling at the nanoscale level. The use of in silico methods, such as nano-QSAR and PSAR, while highly desirable to expedite and rationalize the following stages of toxicological research, are not an alternative, but an introduction to mandatory experimental work.

Intracellular trafficking and gene expression of pH-sensitive, artificially enveloped adenoviruses in vitro and in vivo

Recombinant adenovirus (Ad) has shown great promise in gene therapy. Artificial envelopment of adenovirus within lipid bilayers has previously been shown to decrease the immunogenicity and hepatic affinity of naked Ad in vivo. Unfortunately, this also resulted in a significant reduction of gene expression, which we attributed to poor endosomal release of the Ad from its artificial lipid envelope. In this work, we explored the artificial envelopment of Ad within pH-sensitive DOPE:CHEMS bilayers and characterized this vector by TEM, AFM, dot blot, dynamic light scattering and zeta potential measurements. The artificially enveloped viral vectors exhibited good stability at physiological pH but immediately collapsed and released naked Ad virions at pH 5.5. Intracellular trafficking using confocal laser scanning microscopy (CLSM) revealed that Cy3-labelled Ad enveloped in DOPE:CHEMS bilayers exhibited the characteristic Ad distribution within the cytoplasm that led to virion accumulation around the nuclear membrane, indicating endosomal release of Ad. We obtained equivalent levels of gene expression as those of naked Ad in a series of CAR-positive (CAR+) and CAR-negative (CAR-) cell lines. This suggested that the mechanism of infection for the artificially enveloped Ad remained dependent on the presence of CAR receptors. Finally, the pH-sensitive enveloped Ad were injected intratumorally in human cervical carcinoma xenograft-bearing nude mice, also illustrating their capacity for efficient in vivo marker gene expression. This study is a step forward toward the engineering of functional, artificially enveloped adenovirus vectors for gene transfer applications.

Virus hybrids as nanomaterials for biotechnology

The current review describes advances in the field of bionanotechnology in which viruses are used to fabricate nanomaterials. Viruses are introduced as protein cages, scaffolds, and templates for the production of biohybrid nanostructured materials where organic and inorganic molecules are incorporated in a precise and a controlled fashion. Genetic engineering enables the insertion or replacement of selected amino acids on virus capsids for uses from bioconjugation to crystal growth. The variety of nanomaterials generated in rod-like and spherical viruses is highlighted for tobacco mosaic virus (TMV), M13 bacteriophage, cowpea chlorotic mottle virus (CCMV), and cowpea mosaic virus (CPMV). Functional biohybrid nanomaterials find applications in biosensing, memory devices, nanocircuits, light-harvesting systems, and nanobatteries.

Biomimetic silica microspheres in biosensing

Lipid vesicles spontaneously fuse and assemble into a lipid bilayer on planar or spherical silica surfaces and other substrates. The supported lipid bilayers (SLBs) maintain characteristics of biological membranes, and are thus considered to be biomembrane mimetic systems that are stable because of the underlying substrate. Examples of their shared characteristics with biomembranes include lateral fluidity, barrier formation to ions and molecules, and their ability to incorporate membrane proteins into them. Biomimetic silica microspheres consisting of SLBs on solid or porous silica microspheres have been utilized for different biosensing applications. The advantages of such biomimetic microspheres for biosensing include their increased surface area to volume ratio which improves the detection limits of analytes, and their amenability for miniaturization, multiplexing and high throughput screening. This review presents examples and formats of using such biomimetic solid or porous silica microspheres in biosensing.

Adenovirus in a synthetic membrane wrapper: an example of hybrid vigor?

Nucleic acid delivery applications require the development of carrier systems that are effective, selective, and non-toxic. Many different viral and non-viral approaches, including the use of retroviruses, adenoviruses, liposomes, and dendrimers, have been investigated. Unfortunately, issues still remain with regard to the safety and efficiency of these delivery vehicles. In this Perspective, the challenges of designing a stable vector that is capable of effective gene therapy are highlighted. Progress in the area is also presented, including the work of Kostarelos and co-workers appearing in this issue of ACS Nano, in which they describe a novel delivery vehicle that consists of lipid envelopes encasing viral nanoparticles.