Release of cationic polymer-DNA complexes from the endosome: A theoretical investigation of the proton sponge hypothesis

Enhancing Endosomal Escape and Gene Regulation Activity for Spherical Nucleic Acids

The therapeutic potential of small interfering RNAs (siRNAs) is limited by their poor stability and low cellular uptake. When formulated as spherical nucleic acids (SNAs), siRNAs are resistant to nuclease degradation and enter cells without transfection agents with enhanced activity compared to their linear counterparts; however, the gene silencing activity of SNAs is limited by endosomal entrapment, a problem that impacts many siRNA-based nanoparticle constructs. To increase cytosolic delivery, SNAs are formulated using calcium chloride (CaCl2 ) instead of the conventionally used sodium chloride (NaCl). The divalent calcium (Ca2+ ) ions remain associated with the multivalent SNA and have a higher affinity for SNAs compared to their linear counterparts. Importantly, confocal microscopy studies show a 22% decrease in the accumulation of CaCl2 -salted SNAs within the late endosomes compared to NaCl-salted SNAs, indicating increased cytosolic delivery. Consistent with this finding, CaCl2 -salted SNAs comprised of siRNA and antisense DNA all exhibit enhanced gene silencing activity (up to 20-fold), compared to NaCl-salted SNAs regardless of sequence or cell line (U87-MG and SK-OV-3) studied. Moreover, CaCl2 -salted SNA-based forced intercalation probes show improved cytosolic mRNA detection.

Cinchona Alkaloid Polymers Demonstrate Highly Efficient Gene Delivery Dependent on Stereochemistry, Methoxy Substitution, and Length

Nucleic acid delivery with cationic polymers is a promising alternative to expensive viral-based methods; however, it often suffers from a lower performance. Herein, we present a highly efficient delivery system based on cinchona alkaloid natural products copolymerized with 2-hydroxyethyl acrylate. Cinchona alkaloids are an attractive monomer class for gene delivery applications, given their ability to bind to DNA via both electrostatics and intercalation. To uncover the structure-activity profile of the system, four structurally similar cinchona alkaloids were incorporated into polymers: quinine, quinidine, cinchonine, and cinchonidine. These polymers differed in the chain length, the presence or absence of a pendant methoxy group, and stereochemistry, all of which were found to alter gene delivery performance and the ways in which the polymers overcome biological barriers to transfection. Longer polymers that contained the methoxy-bearing cinchona alkaloids (i.e., quinine and quinidine) were found to have the best performance. These polymers exhibited the tightest DNA binding, largest and most abundant DNA-polymer complexes, and best endosomal escape thanks to their increased buffering capacity and closest nuclear proximity of the payload. Overall, this work highlights the remarkable efficiency of polymer systems that incorporate cinchona alkaloid natural products while demonstrating the profound impact that small structural changes can have on overcoming biological hurdles associated with gene delivery.

Dually Modified Cellulose as a Non-Viral Vector for the Delivery and Uptake of HDAC3 siRNA

RNA interference can be applied to different target genes for treating a variety of diseases, but an appropriate delivery system is necessary to ensure the transport of intact siRNAs to the site of action. In this study, cellulose was dually modified to create a non-viral vector for HDAC3 short interfering RNA (siRNA) transfer into cells. A guanidinium group introduced positive charges into the cellulose to allow complexation of negatively charged genetic material. Furthermore, a biotin group fixed by a polyethylene glycol (PEG) spacer was attached to the polymer to allow, if required, the binding of targeting ligands. The resulting polyplexes with HDAC3 siRNA had a size below 200 nm and a positive zeta potential of up to 15 mV. For N/P ratio 2 and higher, the polymer could efficiently complex siRNA. Nanoparticles, based on this dually modified derivative, revealed a low cytotoxicity. Only minor effects on the endothelial barrier integrity and a transfection efficiency in HEK293 cells higher than Lipofectamine 2000TM were found. The uptake and release of the polyplexes were confirmed by immunofluorescence imaging. This study indicates that the modified biopolymer is an auspicious biocompatible non-viral vector with biotin as a promising moiety.

Engineered macromolecular Toll-like receptor agents and assemblies

Macromolecular Toll-like receptor (TLR) agents have been utilized as agonists and inhibitors in preclinical and clinical settings. These agents interface with the TLR class of innate immune receptors which recognize macromolecular ligands that are characteristic of pathogenic material. As such, many agents that have been historically investigated are derived from the natural macromolecules which activate or inhibit TLRs. This review covers recent research and clinically available TLR agents that are macromolecular or polymeric. Synthetic materials that have been found to interface with TLRs are also discussed. Assemblies of these materials are investigated in the context of improving stability or efficacy of ligands. Attention is given to strategies which modify or enhance the current agents and to future outlooks on the development of these agents.

Engineering poly- and micelleplexes for nucleic acid delivery - A reflection on their endosomal escape

For the longest time, the field of nucleic acid delivery has remained skeptical whether or not polycationic drug carrier systems would ever make it into clinical practice. Yet, with the disclosure of patents on polyethyleneimine-based RNA carriers through leading companies in the field of nucleic acid therapeutics such as BioNTech SE and the progress in clinical studies beyond phase I trials, this aloofness seems to regress. As one of the most striking characteristics of polymer-based vectors, the extraordinary tunability can be both a blessing and a curse. Yet, knowing about the adjustment screws and how they impact the performance of the drug carrier provides the formulation scientist committed to its development with a head start. Here, we equip the reader with a toolbox - a toolbox that should advise and support the developer to conceptualize a cutting-edge poly- or micelleplex system for the delivery of therapeutic nucleic acids; to be specific, to engineer the vector towards maximum endosomal escape performance at minimum toxicity. Therefore, after briefly sketching the boundary conditions of polymeric vector design, we will dive into the topic of endosomal trafficking. We will not only discuss the most recent knowledge of the endo-lysosomal compartment but further depict different hypotheses and mechanisms that facilitate the endosomal escape of polyplex systems. Finally, we will combine the different facets introduced in the previous chapters with the fundamental building blocks of polymer vector design and evaluate the advantages and drawbacks. Throughout the article, a particular focus will be placed on cellular peculiarities, not only as an additional barrier, but also to give inspiration to how such cell-specific traits might be capitalized on.

Could artificial intelligence revolutionize the development of nanovectors for gene therapy and mRNA vaccines?

Gene therapy enables the introduction of nucleic acids like DNA and RNA into host cells, and is expected to revolutionize the treatment of a wide range of diseases. This growth has been further accelerated by the discovery of CRISPR/Cas technology, which allows accurate genomic editing in a broad range of cells and organisms in vitro and in vivo. Despite many advances in gene delivery and the development of various viral and non-viral gene delivery vectors, the lack of highly efficient non-viral systems with low cellular toxicity remains a challenge. The application of cutting-edge technologies such as artificial intelligence (AI) has great potential to find new paradigms to solve this issue. Herein, we review AI and its major subfields including machine learning (ML), neural networks (NNs), expert systems, deep learning (DL), computer vision and robotics. We discuss the potential of AI-based models and algorithms in the design of targeted gene delivery vehicles capable of crossing extracellular and intracellular barriers by viral mimicry strategies. We finally discuss the role of AI in improving the function of CRISPR/Cas systems, developing novel nanobots, and mRNA vaccine carriers.

Polyethylenimine-DNA Nanoparticles under Endosomal Acidification and Implication to Gene Delivery

Non-viral gene delivery using polyethylenimine (PEI) has shown tremendous promise as a therapeutic technique. Through the formation of nanoparticles (NPs), PEIs protect genetic material such as DNA from degradation. Escape of the NPs from endosomes and lysosomes is facilitated by PEI's buffering capacity over a wide range of pH. However, little is known about the effects of endosomal acidification on the morphology of the NPs. In this work, large-scale coarse-grained simulations performed to mimic endosomal acidification reveal that NPs undergo a resizing process that is highly dependent on the N/P ratio (ratio of PEI nitrogen to DNA phosphate) at which they are prepared. With a low N/P ratio, NPs further aggregate after endosomal acidification, whereas with a high N/P ratio they dissociate. The mechanisms behind such NP resizing and its consequences on endosomal escape and nuclear trafficking are discussed. Based on the findings, suggestions are made on the PEI architecture that may enhance NP dissociation driven by endosomal acidification.

Ionizable Lipid Nanoparticle-Mediated Delivery of Plasmid DNA in Cardiomyocytes

Introduction

Gene therapy is a promising approach to be applied in cardiac regeneration after myocardial infarction and gene correction for inherited cardiomyopathies. However, cardiomyocytes are crucial cell types that are considered hard-to-transfect. The entrapment of nucleic acids in non-viral vectors, such as lipid nanoparticles (LNPs), is an attractive approach for safe and effective delivery.

Methods

Here, a mini-library of engineered LNPs was developed for pDNA delivery in cardiomyocytes. LNPs were characterized and screened for pDNA delivery in cardiomyocytes and identified a lead LNP formulation with enhanced transfection efficiency.

Results

By varying lipid molar ratios, the LNP formulation was optimized to deliver pDNA in cardiomyocytes with enhanced gene expression in vitro and in vivo, with negligible toxicity. In vitro, our lead LNP was able to reach a gene expression greater than 80%. The in vivo treatment with lead LNPs induced a twofold increase in GFP expression in heart tissue compared to control. In addition, levels of circulating myeloid cells and inflammatory cytokines remained without significant changes in the heart after LNP treatment. It was also demonstrated that cardiac cell function was not affected after LNP treatment.

Conclusion

Collectively, our results highlight the potential of LNPs as an efficient delivery vector for pDNA to cardiomyocytes. This study suggests that LNPs hold promise to improve gene therapy for treatment of cardiovascular disease.

Enzyme Therapeutic for Ischemia and Reperfusion Injury in Organ Transplantation

Ischemia-reperfusion injury (IRI) remains as a critical challenge for organ transplantation. Herein, an enzyme therapeutic based on superoxide dismutase and catalase for effective mitigation of IRI and pathogen-induced liver injury is reported, providing a therapeutic for organ transplantation and other diseases.

Polycation-Mediated Transfection: Mechanisms of Internalization and Intracellular Trafficking

Polyplex-mediated gene transfection is now in its' fourth decade of serious research, but the promise of polyplex-mediated gene therapy has yet to fully materialize. Only approximately one in a million applied plasmids actually expresses. A large part of this is due to an incomplete understanding of the mechanism of polyplex transfection. There is an assumption that internalization must follow a canonical mechanism of receptor mediated endocytosis. Herein, we present arguments that untargeted (and most targeted) polyplexes do not utilize these routes. By incorporating knowledge of syndecan-polyplex interactions, we can show that syndecans are the "target" for polyplexes. Further, it is known that free polycations (which disrupt cell-membranes by acid-catalyzed hydrolysis of phospholipid esters) are necessary for (untargeted) endocytosis. This can be incorporated into the model to produce a novel mechanism of endocytosis, which fits the observed phenomenology. After membrane translocation, polyplex containing vesicles reach the endosome after diffusing through the actin mesh below the cell membrane. From there, they are acidified and trafficked toward the lysosome. Some polyplexes are capable of escaping the endosome and unpacking, while others are not. Herein, it is argued that for some polycations, as acidification proceeds the polyplexes excluding free polycations, which disrupt the endosomal membrane by acid-catalyzed hydrolysis, allowing the polyplex to escape. The polyplex's internal charge ratio is now insufficient for stability and it releases plasmids which diffuse to the nucleus. A small proportion of these plasmids diffuse through the nuclear pore complex (NPC), with aggregation being the major cause of loss. Those plasmids that have diffused through the NPC will also aggregate, and this appears to be the reason such a small proportion of nuclear plasmids express mRNA. Thus, the structural features which promote unpacking in the endosome and allow for endosomal escape can be determined, and better polycations can be designed.

Polymeric Delivery of Therapeutic Nucleic Acids

The advent of genome editing has transformed the therapeutic landscape for several debilitating diseases, and the clinical outlook for gene therapeutics has never been more promising. The therapeutic potential of nucleic acids has been limited by a reliance on engineered viral vectors for delivery. Chemically defined polymers can remediate technological, regulatory, and clinical challenges associated with viral modes of gene delivery. Because of their scalability, versatility, and exquisite tunability, polymers are ideal biomaterial platforms for delivering nucleic acid payloads efficiently while minimizing immune response and cellular toxicity. While polymeric gene delivery has progressed significantly in the past four decades, clinical translation of polymeric vehicles faces several formidable challenges. The aim of our Account is to illustrate diverse concepts in designing polymeric vectors towards meeting therapeutic goals of in vivo and ex vivo gene therapy. Here, we highlight several classes of polymers employed in gene delivery and summarize the recent work on understanding the contributions of chemical and architectural design parameters. We touch upon characterization methods used to visualize and understand events transpiring at the interfaces between polymer, nucleic acids, and the physiological environment. We conclude that interdisciplinary approaches and methodologies motivated by fundamental questions are key to designing high-performing polymeric vehicles for gene therapy.

Bacterium-mimicking sequentially targeted therapeutic nanocomplexes based on O-carboxymethyl chitosan and their cooperative therapy by dual-modality light manipulation

An integrated gene nanovector capable of overcoming complicated physiological barriers in one vector is desirable to circumvent the challenges imposed by the intricate tumor microenvironment. Herein, a nuclear localization signals (NLS)-decorated element and an iRGD-functionalized element based on O-carboxymethyl chitosan were synthesized, mixed, and coated onto PEI/DNA to fabricate bacterium-mimicking sequentially targeted therapeutic nanocomplexes (STNPs) which were internalized through receptor-mediated endocytosis and other pathways and achieved nuclear translocation of DNA. The endo/lysosomal membrane disruption triggered by reactive oxygen species (ROS) after short-time illumination, together with the DNA nuclear translocation, evoked an enhanced gene expression. Alternatively, the excessive ROS from long-time irradiation induced apoptosis in tumor cells, bringing about greater anti-tumor efficacy owing to the integration of gene and photodynamic therapy. Overall, these results demonstrated bacterium-mimicking STNPs could be a potential candidate for tumor treatments.

Ornithine-derived oligomers and dendrimers for in vitro delivery of DNA and ex vivo transfection of skin cells via saRNA

Gene therapies are undergoing a renaissance, primarily due to their potential for applications in vaccination for infectious diseases and cancers. Although the biology of these technologies is rapidly evolving, delivery strategies need to be improved to overcome the poor pharmacokinetics and cellular transport of nucleic acids whilst maintaining patient safety. In this work, we describe the divergent synthesis of biodegradable cationic dendrimers based on the amino acid ornithine as non-viral gene delivery vectors and evaluate their potential as delivery vectors for DNA and RNA. The dendrimers effectively complexed model nucleic acids at lower N/P ratios than polyethyleneimine and outperformed it in DNA transfection experiments with ratios above 5. Remarkably, all dendrimer polyplexes at N/P = 2 achieved up to 7-fold higher protein content over an optimized PEI formulation when used for transfections with self-amplifying RNA (saRNA). Finally, transfection studies utilizing human skin explants revealed an increase of cells producing protein from 2% with RNA alone to 12% with dendrimer polyplexes, attributed to expression enrichment predominantly in epithelial cells, fibroblasts and leukocytes, with minor enrichment in NK cells, T cells, monocytes, and B cells. Overall, this study indicates the clear potential of ornithine dendrimers as safe and effective delivery vectors for both DNA and RNA therapeutics.

Modularly Programmable Nanoparticle Vaccine Based on Polyethyleneimine for Personalized Cancer Immunotherapy

Nanoparticles (NPs) can serve as a promising vaccine delivery platform for improving pharmacological property and codelivery of antigens and adjuvants. However, NP-based vaccines are generally associated with complex synthesis and postmodification procedures, which pose technical and manufacturing challenges for tailor-made vaccine production. Here, modularly programmed, polyethyleneimine (PEI)-based NP vaccines are reported for simple production of personalized cancer vaccines. Briefly, PEI is conjugated with neoantigens by facile coupling chemistry, followed by electrostatic assembly with CpG adjuvants, leading to the self-assembly of nontoxic, sub-50 nm PEI NPs. Importantly, PEI NPs promote activation and antigen cross-presentation of antigen-presenting cells and cross-priming of neoantigen-specific CD8+ T cells. Surprisingly, after only a single intratumoral injection, PEI NPs with optimal PEGylation elicit as high as ≈30% neoantigen-specific CD8+ T cell response in the systemic circulation and sustain elevated CD8+ T cell response over 3 weeks. PEI-based nanovaccines exert potent antitumor efficacy against pre-established local tumors as well as highly aggressive metastatic tumors. PEI engineering for modular incorporation of neoantigens and adjuvants offers a promising strategy for rapid and facile production of personalized cancer vaccines.

On Complex Coacervate Core Micelles: Structure-Function Perspectives

The co-assembly of ionic-neutral block copolymers with oppositely charged species produces nanometric colloidal complexes, known, among other names, as complex coacervates core micelles (C3Ms). C3Ms are of widespread interest in nanomedicine for controlled delivery and release, whilst research activity into other application areas, such as gelation, catalysis, nanoparticle synthesis, and sensing, is increasing. In this review, we discuss recent studies on the functional roles that C3Ms can fulfil in these and other fields, focusing on emerging structure-function relations and remaining knowledge gaps.

Non-cationic Material Design for Nucleic Acid Delivery

Nucleic acid delivery provides effective options to control intracellular gene expression and protein production. Efficient delivery of nucleic acid typically requires delivery vehicles to facilitate the entry of nucleic acid into cells. Among non-viral delivery vehicles, cationic materials are favored because of their high loading capacity of nucleic acids and prominent cellular uptake efficiency through electrostatic interaction. However, cationic moieties at high dosage tend to induce severe cytotoxicity due to the interference on cell membrane integrity. In contrast, non-cationic materials present alternative delivery approaches with less safety concerns than cationic materials. In this Progress Report, principles of non-cationic material design for nucleic acid delivery are discussed. Examples of such non-cationic platforms are highlighted, including complexation or conjugation with nucleic acids and self-assembled nucleic acid structures.

Drug Delivery for Cancer Immunotherapy and Vaccines

Cancer cells are able to avoid immune surveillance and exploit the immune system to grow and metastasize. With the development of nano- and micro-particles, there has been a growing number of immunotherapy delivery systems developed to elicit innate and adaptive immune responses to eradicate cancer cells. This can be accomplished by training resident immune cells to recognize and eliminate cells with tumor-associated antigens or by providing external stimuli to enhance tumor cell apoptosis in the immunosuppressive tumor microenvironment (TME). In this review we will focus on nano- and micro-particle (NP and MP) based immunotherapies and vaccines used to elicit a potent and sustained antitumor immune response.

Block Copolymer Micelles in Nanomedicine Applications

Polymeric micelles are demonstrating high potential as nanomedicines capable of controlling the distribution and function of loaded bioactive agents in the body, effectively overcoming biological barriers, and various formulations are engaged in intensive preclinical and clinical testing. This Review focuses on polymeric micelles assembled through multimolecular interactions between block copolymers and the loaded drugs, proteins, or nucleic acids as translationable nanomedicines. The aspects involved in the design of successful micellar carriers are described in detail on the basis of the type of polymer/payload interaction, as well as the interplay of micelles with the biological interface, emphasizing on the chemistry and engineering of the block copolymers. By shaping these features, polymeric micelles have been propitious for delivering a wide range of therapeutics through effective sensing of targets in the body and adjustment of their properties in response to particular stimuli, modulating the activity of the loaded drugs at the targeted sites, even at the subcellular level. Finally, the future perspectives and imminent challenges for polymeric micelles as nanomedicines are discussed, anticipating to spur further innovations.

Dual-responsive polyplexes with enhanced disassembly and endosomal escape for efficient delivery of siRNA

Despite the extracellular barriers for siRNA delivery have been overcome by utilizing advanced nanoparticle delivery systems, the key intracellular barriers after internalization including efficient disassembly of siRNA and endosomal escape still remains challenging. To address the issues, we developed a unique pH- and redox potential-responsive polyplex delivery system based on the copolymer of mPEG-b-PLA-PHis-ssPEI1.8 k, which is composed of a pH-responsive copolymer of PEG-b-PLA-PHis (Mw 5 k) and a branched PEI (Mw1.8 k) linked with redox cleavable disulfide bond. The copolymer showed excellent siRNA complexation and protection abilities against endogenous substances at the relatively low N/P ratio of 6. The siRNA release from the polyplexes (N/P 6) was markedly increased from 13.62% to 58.67% under conditions simulating the endosomal microenvironment. Fluorescence resonance energy transfer (FRET) test also indicated a higher disassembly extent of siRNA from the copolymer. The accelerated siRNA release from the polyplexes was markedly restrained when the N/P ratio was raised above 10 due to the increasing of electrostatic interactions. The efficient endosomal escape of siRNA after internalization was confirmed by confocal microscopy, which was attributed to the cleavaged PEI chains inducing membrane destabilization, the "proton sponge effect" of PHis and PEI as well as the relative small size of after disassembly. The enhanced disassembly and endosomal escape were elucidated as the leading cause for polyplexes (N/P 6) showed more efficient Bcl-2 silencing (85.45%) than those polyplexes with higher N/P ratios (N/P 10 and 15). In vivo results further demonstrated that polyplexes (N/P 6) delivery of siBcl-2 significantly inhibited the MCF-7 breast tumor growth as compared to its counterparts. The incorporation of convertible non-electrical interactions at a balance with electrostatic interactions in complexation siRNA has been demonstrated as an effective strategy to achieve efficient disassembly from stable polyplexes. Moreover, polyplexes equipped with the enhanced disassembly and endosomal escape provides a new potential way to tackle the intracellular delivery bottleneck for siRNA delivery.

The great escape: how cationic polyplexes overcome the endosomal barrier

Endo-lysosomal escape strategies of cationic polymer-mediated gene delivery at a glance.

Adjuvant-Loaded Spiky Gold Nanoparticles for Activation of Innate Immune Cells

INTRODUCTION

Gold nanoparticles are versatile carriers for delivery of biomacromolecules. Here, we have developed spiky gold nanoparticles (SGNPs) that can efficiently deliver immunostimulatory agents.

OBJECTIVES

Our goal was to develop a platform technology for co-delivery of multiple adjuvant molecules for synergistic stimulation and maturation of innate immune cells.

METHODS

SGNPs were synthesized by a seed-mediated, surfactant-free synthesis method and incorporated with polyinosinic-polycytidylic acid (pIC) and DNA oligonucleotide containing unmethylated CpG motif (CpG) by an electrostatic layer-by-layer approach. Adjuvant-loaded SGNP nano-complexes were examined for their biophysical and biochemical properties and studied for immune activation using bone marrow-derived dendritic cells (BMDCs).

RESULTS

We have synthesized SGNPs with branched nano-spikes layered with pIC and/or CpG. Adjuvant-loaded SGNP nano-complexes promoted cellular uptake of the adjuvants. Importantly, we achieved spatio-temporal control over co-delivery of pIC and CpG via SGNPs, which produced synergistic enhancement in cytokine release (IL-6, TNF-α) and upregulation of co-stimulatory markers (CD40, CD80, CD86) in BMDCs, compared with pIC, CpG, or their admixtures.

CONCLUSION

SGNPs serve as a versatile delivery platform that allows flexible and on-demand cargo fabrication for strong activation of innate immune cells.

A Triple-Fluorophore-Labeled Nucleic Acid pH Nanosensor to Investigate Non-viral Gene Delivery

There is a need for new tools to better quantify intracellular delivery barriers in high-throughput and high-content ways. Here, we synthesized a triple-fluorophore-labeled nucleic acid pH nanosensor for measuring intracellular pH of exogenous DNA at specific time points in a high-throughput manner by flow cytometry following non-viral transfection. By including two pH-sensitive fluorophores and one pH-insensitive fluorophore in the nanosensor, detection of pH was possible over the full physiological range. We further assessed possible correlation between intracellular pH of delivered DNA, cellular uptake of DNA, and DNA reporter gene expression at 24 hr post-transfection for poly-L-lysine and branched polyethylenimine polyplex nanoparticles. While successful transfection was shown to clearly depend on median cellular pH of delivered DNA at the cell population level, surprisingly, on an individual cell basis, there was no significant correlation between intracellular pH and transfection efficacy. To our knowledge, this is the first reported instance of high-throughput single-cell analysis between cellular uptake of DNA, intracellular pH of delivered DNA, and gene expression of the delivered DNA. Using the nanosensor, we demonstrate that the ability of polymeric nanoparticles to avoid an acidic environment is necessary, but not sufficient, for successful transfection.

Cancer Nanotechnology: Opportunities for Prevention, Diagnosis, and Therapy

Nanotechnological innovations over the last 16 years have brought about the potential to revolutionize specific therapeutic drug delivery to cancer tissue without affecting normal tissues. In addition, there are new nanotechnology-based platforms for diagnosis of cancers and for theranostics, i.e., integrating diagnosis with therapy and follow-up of effectiveness of therapy. This chapter presents an overview of these nanotechnology-based advancements in the areas of prevention, diagnosis, therapy, and theranostics for cancer. In addition, we stress the need to educate bio- and medical students in the field of nanotechnology.

Chitosan DNA nanoparticles for oral gene delivery

Gene therapy is a promising technology with potential applications in the treatment of medical conditions, both congenital and acquired. Despite its label as breakthrough technology for the 21^st century, the simple concept of gene therapy - the introduction of a functional copy of desired genes in affected individuals - is proving to be more challenging than expected. Oral gene delivery has shown intriguing results and warrants further exploration. In particular, oral administration of chitosan DNA nanoparticles, one the most commonly used formulations of therapeutic DNA, has repeatedly demonstrated successful in vitro and in vivo gene transfection. While oral gene therapy has shown immense promise as treatment options in a variety of diseases, there are still significant barriers to overcome before it can be considered for clinical applications. In this review we provide an overview of the physiologic challenges facing the use of chitosan DNA nanoparticles for oral gene delivery at both the extracellular and intracellular level. From administration at the oral cavity, chitosan nanoparticles must traverse the gastrointestinal tract and protect its DNA contents from significant jumps in pH levels, various intestinal digestive enzymes, thick mucus layers with high turnover, and a proteinaceous glycocalyx meshwork. Once these extracellular barriers are overcome, chitosan DNA nanoparticles must enter intestinal cells, escape endolysosomes, and disassociate from genetic material at the appropriate time allowing transport of genetic material into the nucleus to deliver a therapeutic effect. The properties of chitosan nanoparticles and modified nanoparticles are discussed in this review. An understanding of the barriers to oral gene delivery and how to overcome them would be invaluable for future gene therapy development.

Intracellular Availability of pDNA and mRNA after Transfection: A Comparative Study among Polyplexes, Lipoplexes, and Lipopolyplexes

Intracellular availability of nucleic acids from synthetic vectors is critical and directly influences the transfection efficiency (TE). Herein, we evaluated the TE of polymer- and lipid-based nanoplexes (polyplexes, lipoplexes and lipopolyplexes) of EGFP-encoding mRNA and pDNA. To determine the translation and transcription efficiency of each nucleic acid nanoplex, in vitro expression was measured in HEK293T7 cells that permit gene expression in the cytoplasmic region. Globally, mRNA transfection profile was well corroborative with cytoplasmic transfection of pT7-pDNA as well as with nuclear transfection of pCMV-DNA. Irrespective of the nucleic acid, high TE was observed with histidinylated l-polyethylenimine (His-lPEI) polyplexes and dioleyl succinyl paromomycin/O,O-dioleyl-N-histamine phosphoramidate (DOPS/MM27) lipoplexes. Moreover, His-lPEI polyplexes yielded higher in vitro expression of EGFP for pDNA than for mRNA. Furthermore, a significant enhancement in the TE in the presence of an excess of His-lPEI was observed indicating that this polymer promotes cytosolic delivery. Compared to other nanoplexes, His-lPEI polyplex showed high intracellular availability of DNA and mRNA along with low cytotoxicity, owing to its rapid (complete or partial) unpacking in the cytosol and/or endosomes. This study gives an insight that, whether with mRNA or pDNA, enhancing nanoplex unpacking in the endosomes and cytosol would improve the delivery of nucleic acid in the cytosol and particularly in the case of pDNA where a sufficient available amount of pDNA in the cytoplasm would definitely improve its transport toward the nucleus.

Polyion complex (PIC) particles: Preparation and biomedical applications

Oppositely charged polyions can self-assemble in solution to form colloidal polyion complex (PIC) particles. Such nanomaterials can be loaded with charged therapeutics such as DNA, drugs or probes for application as novel nanomedicines and chemical sensors to detect disease markers. A comprehensive discussion of the factors affecting PIC particle self-assembly and their response to physical and chemical stimuli in solution is described herein. Finally, a collection of key examples of polyionic nanoparticles for biomedical applications is discussed to illustrate their behaviour and demonstrate the potential of PIC nanoparticles in medicine.

Monodispersed calcium carbonate nanoparticles modulate local pH and inhibit tumor growth in vivo

The acidic extracellular environment of tumors potentiates their aggressiveness and metastasis, but few methods exist to selectively modulate the extracellular pH (pHe) environment of tumors. Transient flushing of biological systems with alkaline fluids or proton pump inhibitors is impractical and nonselective. Here we report a nanoparticles-based strategy to intentionally modulate the pHe in tumors. Biochemical simulations indicate that the dissolution of calcium carbonate nanoparticles (nano-CaCO3) in vivo increases pH asymptotically to 7.4. We developed two independent facile methods to synthesize monodisperse non-doped vaterite nano-CaCO3 with distinct size range between 20 and 300 nm. Using murine models of cancer, we demonstrate that the selective accumulation of nano-CaCO3 in tumors increases tumor pH over time. The associated induction of tumor growth stasis is putatively interpreted as a pHe increase. This study establishes an approach to prepare nano-CaCO3 over a wide particle size range, a formulation that stabilizes the nanomaterials in aqueous solutions, and a pH-sensitive nano-platform capable of modulating the acidic environment of cancer for potential therapeutic benefits.

Cardiac gene therapy: Recent advances and future directions

Gene therapy has the potential to serve as an adaptable platform technology for treating various diseases. Cardiovascular disease is a major cause of mortality in the developed world and genetic modification is steadily becoming a more plausible method to repair and regenerate heart tissue. Recently, new gene targets to treat cardiovascular disease have been identified and developed into therapies that have shown promise in animal models. Some of these therapies have advanced to clinical testing. Despite these recent successes, several barriers must be overcome for gene therapy to become a widely used treatment of cardiovascular diseases. In this review, we evaluate specific genetic targets that can be exploited to treat cardiovascular diseases, list the important delivery barriers for the gene carriers, assess the most promising methods of delivering the genetic information, and discuss the current status of clinical trials involving gene therapies targeted to the heart.

Polyetherimide-grafted Fe₃O₄@SiO2₂ nanoparticles as theranostic agents for simultaneous VEGF siRNA delivery and magnetic resonance cell imaging

Engineering a safe and high-efficiency delivery system for efficient RNA interference is critical for successful gene therapy. In this study, we designed a novel nanocarrier system of polyethyleneimine (PEI)-modified Fe₃O₄@SiO₂, which allows high efficient loading of VEGF small hairpin (sh)RNA to form Fe₃O₄@SiO₂/PEI/VEGF shRNA nanocomposites for VEGF gene silencing as well as magnetic resonance (MR) imaging. The size, morphology, particle stability, magnetic properties, and gene-binding capacity and protection were determined. Low cytotoxicity and hemolyticity against human red blood cells showed the excellent biocompatibility of the multifunctional nanocomposites, and also no significant coagulation was observed. The nanocomposites maintain their superparamagnetic property at room temperature and no appreciable change in magnetism, even after PEI modification. The qualitative and quantitative analysis of cellular internalization into MCF-7 human breast cancer cells by Prussian blue staining and inductively coupled plasma atomic emission spectroscopy analysis, respectively, demonstrated that the Fe₃O₄@SiO₂/PEI/VEGF shRNA nanocomposites could be easily internalized by MCF-7 cells, and they exhibited significant inhibition of VEGF gene expression. Furthermore, the MR cellular images showed that the superparamagnetic iron oxide core of our Fe₃O₄@SiO₂/PEI/VEGF shRNA nanocomposites could also act as a T₂-weighted contrast agent for cancer MR imaging. Our data highlight multifunctional Fe₃O₄@SiO₂/PEI/VEGF shRNA nanocomposites as a potential platform for simultaneous gene delivery and MR cell imaging, which are promising as theranostic agents for cancer treatment and diagnosis in the future.

Nanocarrier mediated delivery of siRNA/miRNA in combination with chemotherapeutic agents for cancer therapy: current progress and advances

Chemotherapeutic agents have certain limitations when it comes to treating cancer, the most important being severe side effects along with multidrug resistance developed against them. Tumor cells exhibit drug resistance due to activation of various cellular level processes viz. activation of drug efflux pumps, anti-apoptotic defense mechanisms, etc. Currently, RNA interference (RNAi) based therapeutic approaches are under vibrant scrutinization to seek cancer cure. Especially small interfering RNA (siRNA) and micro RNA (miRNA), are able to knock down the carcinogenic genes by targeting the mRNA expression, which underlies the uniqueness of this therapeutic approach. Recent research focus in the regime of cancer therapy involves the engagement of targeted delivery of siRNA/miRNA in combinations with other therapeutic agents (such as gene, DNA or chemotherapeutic drug) for targeting permeability glycoprotein (P-gp), multidrug resistant protein 1 (MRP-1), B-cell lymphoma (BCL-2) and other targets that are mainly responsible for resistance in cancer therapy. RNAi-chemotherapeutic drug combinations have also been found to be effective against different molecular targets as well and can increase the sensitization of cancer cells to therapy several folds. However, due to stability issues associated with siRNA/miRNA suitable protective carrier is needed and nanotechnology based approaches have been widely explored to overcome these drawbacks. Furthermore, it has been univocally advocated that the co-delivery of siRNA/miRNA with other chemodrugs significantly enhances their capability to overcome cancer resistance compared to naked counterparts. The objective of this article is to review recent nanocarrier based approaches adopted for the delivery of siRNA/miRNA combinations with other anticancer agents (siRNA/miRNA/pDNA/chemodrugs) to treat cancer.

Cationic amphiphilic macromolecule (CAM)-lipid complexes for efficient siRNA gene silencing

The accumulated evidence has shown that lipids and polymers each have distinct advantages as carriers for siRNA delivery. Composite materials comprising both lipids and polymers may present improved properties that combine the advantage of each. Cationic amphiphilic macromolecules (CAMs) containing a hydrophobic alkylated mucic acid segment and a hydrophilic poly(ethylene glycol) (PEG) tail were non-covalently complexed with two lipids, 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine (DOPE) and 1,2-dioleoyl-3-trimethylammonium-propane (DOTAP), to serve as a siRNA delivery vehicle. By varying the weight ratio of CAM to lipid, cationic complexes with varying compositions were obtained in aqueous media and their properties evaluated. CAM-lipid complex sizes were relatively independent of composition, ranging from 100 to 200nm, and zeta potentials varied from 10 to 30mV. Transmission electron microscopy confirmed the spherical morphology of the complexes. The optimal N/P ratio was 50 as determined by electrophoretic mobility shift assay. The ability to achieve gene silencing was evaluated by anti-luciferase siRNA delivery to a U87-luciferase cell line. Several weight ratios of CAM-lipid complexes were found to have similar delivery efficiency compared to the gold standard, Lipofectamine. Isothermal titration calorimetry revealed that siRNA binds more tightly at pH=7.4 than pH=5 to CAM-lipid (1:10 w/w). Further intracellular trafficking studies monitored the siRNA escape from the endosomes at 24h following transfection of cells. The findings in the paper indicate that CAM-lipid complexes can serve as a novel and efficient siRNA delivery vehicle.

Gold nanoparticles for nucleic acid delivery

Gold nanoparticles provide an attractive and applicable scaffold for delivery of nucleic acids. In this review, we focus on the use of covalent and noncovalent gold nanoparticle conjugates for applications in gene delivery and RNA-interference technologies. We also discuss challenges in nucleic acid delivery, including endosomal entrapment/escape and active delivery/presentation of nucleic acids in the cell.

Photochemical internalization-mediated nonviral gene transfection: polyamine core-shell nanoparticles as gene carrier

The overall objective of the research was to investigate the utility of photochemical internalization (PCI) for the enhanced nonviral transfection of genes into glioma cells. The PCI-mediated introduction of the tumor suppressor gene phosphatase and tensin homolog (PTEN) or the cytosine deaminase (CD) pro-drug activating gene into U87 or U251 glioma cell monolayers and multicell tumor spheroids were evaluated. In the study reported here, polyamine-DNA gene polyplexes were encapsulated in a nanoparticle (NP) with an acid degradable polyketal outer shell. These NP synthetically mimic the roles of viral capsid and envelope, which transport and release the gene, respectively. The effects of PCI-mediated suppressor and suicide genes transfection efficiency employing either “naked” polyplex cores alone or as NP-shelled cores were compared. PCI was performed with the photosensitizer AlPcS 2a and λ=670-nm laser irradiance. The results clearly demonstrated that the PCI can enhance the delivery of both the PTEN or CD genes in human glioma cell monolayers and multicell tumor spheroids. The transfection efficiency, as measured by cell survival and inhibition of spheroid growth, was found to be significantly greater at suboptimal light and DNA levels for shelled NPs compared with polyamine-DNA polyplexes alone.

Recent developments in nucleic acid delivery with polyethylenimines

Polyethylenimines (PEIs) have proven to be highly efficient and versatile agents for nucleic acid delivery in vitro and in vivo. Despite the low biodegradability of these polymers, they have been used in several clinical trials and the results suggest that the nucleic acid/PEI complexes have a good safety profile. The high transfection efficiency of PEIs probably relies on the fact that these polymers possess a stock of amines that can undergo protonation during the acidification of endosomes. This buffering capacity likely enhances endosomal escape of the polyplexes through the "proton sponge" effect. PEIs have also attracted great interest because the presence of many amino groups allow for easy chemical modifications or conjugation of targeting moieties and hydrophilic polymers. In the present chapter, we summarize and discuss the mechanism of PEI-mediated transfection, as well as the recent developments in PEI-mediated DNA, antisense oligonucleotide, and siRNA delivery.

Single vehicular delivery of siRNA and small molecules to control stem cell differentiation

Achieving a controlled and reproducible means to direct stem cell differentiation is the single most critical concern scientists have been trying to address since the discovery of stem cells. In this regard, the use of small molecules and RNA interference offers unique advantages by targeting different cellular mechanisms. Our cyclodextrin-modified dendritic polyamine construct (termed DexAM) combines the unique properties of two distinct chemical moieties in a single delivery vehicle. DexAM is a single vehicle that not only solubilizes hydrophobic small molecules in physiological solutions but also forms complexes with siRNA molecules, making it an attractive delivery system for controlling stem cell differentiation. Herein, we report the synthesis and application of DexAM to simultaneously deliver hydrophobic small molecules and siRNA into neural stem cells to significantly enhance their neuronal differentiation.

Improved transfection in human mesenchymal stem cells: effective intracellular release of pDNA by magnetic polyplexes

AIM

Magnetically guided transfection has been shown as a promising approach for the genetic modification of cells. We observed that polyethylenimine (PEI)-condensed pDNA, combined with magnetic nanoparticles (MNPs) via biotin-streptavidin interactions could provide higher transfection efficiency than pDNA/PEI alone, even without the application of a magnetic force. Therefore, we intended to investigate the beneficial properties of MNP-based transfection.

MATERIALS & METHODS

We performed three-color fluorescent labeling of magnetic transfection complexes and traced them inside human mesenchymal stem cells over time using confocal microscopy in order to study pDNA release kinetics by colocalization studies.

RESULTS

We demonstrated that MNP-combined pDNA/PEI complexes provide more rapid and efficient release of pDNA than pDNA/PEI alone, which could be explained by the retention of PEI on the surface of the MNPs due to strong biotin-streptavidin interactions.

CONCLUSION

The process of pDNA liberation may significantly influence the efficiency of the transfection vector. Therefore, it should be carefully considered when creating novel gene delivery agents.

Recent developments and perspectives on gene therapy using synthetic vectors

Nonviral vector technology is attracting increasing importance in the biomedical community owing to unique advantages and prospects for the treatment of severe diseases by gene therapy. In this review, synthetic vectors that allow the controlled design of efficient and biocompatible carriers are highlighted. The current benefits, potentials, problems and unmet needs of synthetic gene delivery systems, as well as the strategies to overcome the obstacles are also discussed. Common design principles and structure–activity trends have been established that are important for stable and targeted transport to regions of interest in the body, efficient uptake into cells as well as controlled release of drugs inside the cells, for example, in specialized compartments. The status quo of the use of these systems in preclinical and clinical trials is also considered.

Application of ferriferous oxide modified by chitosan in gene delivery

New approaches to improve the traditional gene carriers are still required. Here we explore Fe₃O₄ modified with degradable polymers that enhances gene delivery and target delivery using permanent magnetic field. Two magnetic Fe₃O₄ nanoparticles coated with chitosan (CTS) and polyethylene glycol (PEG) were synthesized by means of controlled chemical coprecipitation. Plasmid pEGFP was encapsulated as a reported gene. The ferriferous oxide complexes were approximately spherical; surface charge of CTS-Fe₃O₄ and PEG-Fe₃O₄ was about 20 mv and 0 mv, respectively. The controlled release of DNA from the CTS-Fe₃O₄ nanoparticles was observed. Concurrently, a desired Fe₃O₄ concentration of less than 2 mM was verified as safe by means of a cytotoxicity test in vitro. Presence of the permanent magnetic field significantly increased the transfection efficiency. Furthermore, the passive target property and safety of magnetic nanoparticles were also demonstrated in an in vivo test. The novel gene delivery system was proved to be an effective tool required for future target expression and gene therapy in vivo.

Smart nanocarriers for pH-triggered targeting and release of hydrophobic drugs

The use of hybrid pH-sensitive micelles based mainly on the (PEO)(129)(P2VP)(43)(PCL)(17) ABC miktoarm star copolymer as potential triggered drug delivery systems was investigated. Co-micellization of this star copolymer with a second copolymer labeled by a targeting ligand, i.e. biotin, on the pH sensitive block (poly-2-vinylpyridine) is considered here in order to impart possible active targeting of the tumor cells. Two architectures were studied for these labeled copolymers, i.e. a miktoarm star or a linear ABC terpolymer, and the respective hybrid micelles are compared in terms of cytotoxicity (cells viability) and cellular uptake (using fluorescent dye loaded micelles). Finally, the triggered drug release in the cytosol of tumor cells was investigated by studying, on the one hand, the lysosomal integrity after internalization and, on the other hand, the release profile in function of the pH.

Facile preparation of cationic gold nanoparticle-bioconjugates for cell penetration and nuclear targeting

The present work faces the rising demand of cationic particles of different sizes for biological applications, especially in gene therapies and nanotoxicology studies. A simple phase-transfer methodology has been developed for the functionalization of gold nanoparticles (Au NPs) with a variety of ligands, both cationic and anionic in aqueous solution, employing different nanocrystal sizes with narrow size distributions. Successful functionalization has been demonstrated by UV-vis spectroscopy, DLS, ζ-potential, and FTIR spectroscopy characterization of the particles before and after the phase transfer. The intracellular uptake of the differently charged Au NPs functionalized with peptidic biomolecules was investigated with human fibroblasts (1BR3G) by ICP-MS analysis of the digested cells and confocal fluorescence microscopy, which showed increased internalization of the cationic bioconjugates. Nuclear targeting could be observed by TEM, suggesting that the cationic peptidic biomolecule is acting as a nuclear localization signal.

Modeling the proton sponge hypothesis: examining proton sponge effectiveness for enhancing intracellular gene delivery through multiscale modeling

Dendrimers have been proposed as therapeutic gene delivery platforms. Their superior transfection efficiency is attributed to their ability to buffer the acidification of the endosome and attach to the nucleic acids. For effective transfection, the strategy is to synthesize novel dendrimers that optimize both of these traits, but the prediction of the buffering behavior in the endosome remains elusive. It is suggested that buffering dendrimers induce an osmotic pressure sufficient to rupture the endosome and release nucleic acids, which forms to sequestrate most internalized exogenous materials. Presented here are the results of a computational study modeling osmotically driven endosome burst or the 'proton sponge effect.' The approach builds on previous cellular simulation efforts by linking the previous model with a sponge protonation model, then observing the impact on endosomal swelling and acidification. Calibrated and validated using reported experimental data, the simulations offer insights into defining the properties of suitable dendrimers for enhancing gene delivery as a function of polymer structure.