Arginine-rich polyplexes for gene delivery to neuronal cells

GalNAc- or Mannose-PEG-Functionalized Polyplexes Enable Effective Lectin-Mediated DNA Delivery

A cationic, dendrimer-like oligo(aminoamide) carrier with four-arm topology based on succinoyl tetraethylene pentamine and histidines, cysteines, and N-terminal azido-lysines was screened for plasmid DNA delivery on various cell lines. The incorporated azides allow modification with various shielding agents of different polyethylene glycol (PEG) lengths and/or different ligands by copper-free click reaction, either before or after polyplex formation. Prefunctionalization was found to be advantageous over postfunctionalization in terms of nanoparticle formation, stability, and efficacy. A length of 24 ethylene oxide repetition units and prefunctionalization of ≥50% of azides per carrier promoted optimal polyplex shielding. PEG shielding resulted in drastically reduced DNA transfer, which could be successfully restored by active lectin targeting via novel GalNAc or mannose ligands, enabling enhanced receptor-mediated endocytosis of the carrier system. The involvement of the asialoglycoprotein receptor (ASGPR) in the uptake of GalNAc-functionalized polyplexes was confirmed in the ASGPR-positive hepatocarcinoma cell lines HepG2 and Huh7. Mannose-modified polyplexes showed superior cellular uptake and transfection efficacy compared to unmodified and shielded polyplexes in mannose-receptor-expressing dendritic cell-like DC2.4 cells.

Effect of zwitterionic sulfobetaine incorporation on blood behaviours, phagocytosis, and in vivo biodistribution of pH-responsive micelles with positive charges

pH-responsive micelles with positive charges are challenged by their significant effect on the cells/proteins and compromise their final fate due to electrostatic interactions. As one of the promising strategies, zwitterion incorporation in micelles has attracted considerable attention and displayed improved protein adsorption and blood circulation performances. However, previous reports in this field have been mostly limited in hemolysis for studying blood behaviour and lack a comprehensive understanding of their interactions with blood components. Herein, we present a prelimilary study on the effect of zwitterionic sulfobetaine incorporation on blood behaviour, phagocytosis, and in vivo biodistribution of pH-responsive micelles with positive charges. Amphiphilic triblock copolymers, namely poly(ε-caprolactone)-b-poly(N,N-diethylaminoethyl methacrylate)-(N-(3-sulfopropyl-N-methacryloxyethy-N,N-diethylammonium betaine)) (PCL-PDEAPSx, x = 2, 6, 10), containing different numbers of sulfobetaine groups were synthesized through four steps to prepare the pH-responsive micelles with positive charges. The effect of the sulfobetaine incorporation displayed different profiles, e.g., the micelles had no effect on RBC aggregation, thrombin time (TT), and platelet aggregation, while the cytotoxicity, hemolysis, RBC deformability, activated partial thromboplastin time (APTT), prothrombin time (PT), platelet activation, protein (albumin, fibrinogen, plasma) adsorption, phagocytosis, and in vivo biodistribution decreased with the increase in the sulfobetaine number, in which the transition mainly occurred at a sulfobetaine/tertiary amine group ratio of 3/7-1/1 compared to that of the mPEG control. In addition, the micelles displayed a strong inhibitory effect on the intrinsic coagulation pathway, which was associated with a significant decrease in the coagulation factor activity. Based on these findings, the related mechanism is discussed and proposed, which can aid the rational design of pH-responsive micelles for improved therapeutics.

Polyplex designs for improving the stability and safety of RNA therapeutics

Nanoparticle-based delivery systems have contributed to the recent clinical success of RNA therapeutics, including siRNA and mRNA. RNA delivery using polymers has several distinct properties, such as enabling RNA delivery into extra-hepatic organs, modulation of immune responses to RNA, and regulation of intracellular RNA release. However, delivery systems should overcome safety and stability issues to achieve widespread therapeutic applications. Safety concerns include direct damage to cellular components, innate and adaptive immune responses, complement activation, and interaction with surrounding molecules and cells in the blood circulation. The stability of the delivery systems should balance extracellular RNA protection and controlled intracellular RNA release, which requires optimization for each RNA species. Further, polymer designs for improving safety and stability often conflict with each other. This review covers advances in polymer-based approaches to address these issues over several years, focusing on biological understanding and design concepts for delivery systems rather than material chemistry.

Non-viral gene therapy using RNA interference with PDGFR-α mediated epithelial-mesenchymal transformation for proliferative vitreoretinopathy

Fibrotic eye diseases, a series of severe oculopathy, that will destroy normal ocular refractive media and imaging structures. It is characterized by the transformation of the epithelial cells into mesenchyme cells. Proliferative vitreoretinopathy (PVR) is one of these representative diseases. In this investigation, polyethylene glycol grafted branched Polyethyleneimine (PEI-g-PEG) was used as a non-viral gene vector in gene therapy of PVR to achieve anti-fibroblastic effects in vitro and in vivo by interfering with platelet-derived growth factor alpha receptor (PDGFR-α) in the epithelial-mesenchymal transition (EMT) of retinal pigment epithelium (RPE) cells. The plasmid was wrapped by electrostatic conjugation. Physical characterization of the complexes indicated that the gene complexes were successfully prepared. In vitro, cellular experiments showed excellent biocompatibility of PEI-g-PEG, efficient cellular uptake of the gene complexes, and successful expression of the corresponding fragments. Through gene silencing technique, PEI-g-PEG/PDGFR-α shRNA successfully inhibited the process of EMT in vitro. Furthermore, in vivo animal experiments suggested that this method could effectively inhibit the progression of fibroproliferative membranes of PVR. Herein, a feasible and promising clinical idea was provided for developing non-viral gene vectors and preventing fibroblastic eye diseases by RNA interference (RNAi) technology.

Nanosystems for gene therapy targeting brain damage caused by viral infections

Several human pathogens can cause long-lasting neurological damage. Despite the increasing clinical knowledge about these conditions, most still lack efficient therapeutic interventions. Gene therapy (GT) approaches comprise strategies to modify or adjust the expression or function of a gene, thus providing therapy for human diseases. Since recombinant nucleic acids used in GT have physicochemical limitations and can fail to reach the desired tissue, viral and non-viral vectors are applied to mediate gene delivery. Although viral vectors are associated to high levels of transfection, non-viral vectors are safer and have been further explored. Different types of nanosystems consisting of lipids, polymeric and inorganic materials are applied as non-viral vectors. In this review, we discuss potential targets for GT intervention in order to prevent neurological damage associated to infectious diseases as well as the role of nanosized non-viral vectors as agents to help the selective delivery of these gene-modifying molecules. Application of non-viral vectors for delivery of GT effectors comprise a promising alternative to treat brain inflammation induced by viral infections.

Poly(allylguanidine)-Coated Surfaces Regulate TGF-β in Glioblastoma Cells to Induce Apoptosis via NF-κB Pathway Activation

Polycationic biomaterials are currently widely applied in neuronal cell cultures to promote cell adhesion and viability. However, polycations generally have cytotoxic properties that limit their application in the field of biomaterials. In this study, we examined the use of a novel polycation poly(allylguanidine) (PAG), which contains a guanidine group in the side chain and a structure similar to poly(allylamine hydrochloride) (PAH), an example of another commonly used polycation. Our findings showed that exposure to PAG induced apoptosis in glioblastoma (GBM) cells, while exposure to PAH induced necrosis. Compared to control groups, the PAG coating significantly limited the proliferation of GBM8901 in vitro and in vivo. Furthermore, GBM8901 cells exposed to the PAG coating exhibited increased levels of phospho-p65 and phosphor-IκB, implying that GBM8901 cells underwent apoptotic cell death via the NF-κB pathway by the regulation of TGF-β. This result was further confirmed to be consistent with the experimental results from western blot protein analysis and apoptosis/necrosis assays. These findings indicate that the polycation PAG has the potential to not only suppress the proliferation of GBM8901 cancer cells but also improve the neural viability and promote the differentiation of neural stem/precursor cells into mature neurons. In conclusion, biomaterials such as PAG act as extremely potent options for applications in the treatment of pathological conditions such as brain cancer.

Smart arginine-equipped polycationic nanoparticles for p/CRISPR delivery into cells

An efficient and safe delivery system for the transfection of CRISPR plasmid (p/CRISPR) into target cells can open new avenues for the treatment of various diseases. Herein, we design a novel nonvehicle by integrating an arginine-disulfide linker with low-molecular-weight PEI (PEI_1.8k) for the delivery of p/CRISPR. These PEI_1.8k-Arg nanoparticles facilitate the plasmid release and improve both membrane permeability and nuclear localization, thereby exhibiting higher transfection efficiency compared to native PEI_1.8kin the delivery of nanocomplexes composed of PEI_1.8k-Arg and p/CRISPR into conventional cells (HEK 293T). This nanovehicle is also able to transfect p/CRISPR in a wide variety of cells, including hard-to-transfect primary cells (HUVECs), cancer cells (HeLa), and neuronal cells (PC-12) with nearly 5-10 times higher efficiency compared to the polymeric gold standard transfection agent. Furthermore, the PEI_1.8k-Arg nanoparticles can edit the GFP gene in the HEK 293T-GFP reporter cell line by delivering all possible forms of CRISPR/Cas9 system (e.g. plasmid encoding Cas9 and sgRNA targeting GFP, and Cas9/sgRNA ribonucleoproteins (RNPs) as well as Cas9 expression plasmid andin vitro-prepared sgRNA) into HEK 293T-GFP cells. The successful delivery of p/CRISPR into local brain tissue is also another remarkable capability of these nanoparticles. In view of all the exceptional benefits of this safe nanocarrier, it is expected to break new ground in the field of gene editing, particularly for therapeutic purposes.

Gene Therapy for Huntington's Disease: The Final Strategy for a Cure?

Huntington's disease (HD) has become a target of the first clinical trials for gene therapy among movement disorders with a genetic origin. More than 100 clinical trials regarding HD have been tried, but all failed, although there were some improvements limited to symptomatic support. Compared to other neurogenetic disorders, HD is known to have a single genetic target. Thus, this is an advantage and its cure is more feasible than any other movement disorder with heterogeneous genetic causes. In this review paper, the authors attempt to cover the characteristics of HD itself while providing an overview of the gene transfer methods currently being researched, and will introduce an experimental trial with a preclinical model of HD followed by an update on the ongoing clinical trials for patients with HD.

New Perspectives of Gene Therapy on Polyglutamine Spinocerebellar Ataxias: From Molecular Targets to Novel Nanovectors

Seven of the most frequent spinocerebellar ataxias (SCAs) are caused by a pathological expansion of a cytosine, adenine and guanine (CAG) trinucleotide repeat located in exonic regions of unrelated genes, which in turn leads to the synthesis of polyglutamine (polyQ) proteins. PolyQ proteins are prone to aggregate and form intracellular inclusions, which alter diverse cellular pathways, including transcriptional regulation, protein clearance, calcium homeostasis and apoptosis, ultimately leading to neurodegeneration. At present, treatment for SCAs is limited to symptomatic intervention, and there is no therapeutic approach to prevent or reverse disease progression. This review provides a compilation of the experimental advances obtained in cell-based and animal models toward the development of gene therapy strategies against polyQ SCAs, providing a discussion of their potential application in clinical trials. In the second part, we describe the promising potential of nanotechnology developments to treat polyQ SCA diseases. We describe, in detail, how the design of nanoparticle (NP) systems with different physicochemical and functionalization characteristics has been approached, in order to determine their ability to evade the immune system response and to enhance brain delivery of molecular tools. In the final part of this review, the imminent application of NP-based strategies in clinical trials for the treatment of polyQ SCA diseases is discussed.

Amphipathic design dictates self-assembly, cytotoxicity and cell uptake of arginine-rich surfactant-like peptides

Amphiphilicity is the most critical parameter in the self-assembly of surfactant-like peptides (SLPs), regulating the way by which hydrophobic attraction holds peptides together. Its effects go beyond supramolecular assembly and may also trigger different cell responses of bioactive peptide-based nanostructures. Herein, we investigate the self-assembly and cellular effects of nanostructures based on isomeric SLPs composed by arginine (R) and phenylalanine (F). Two amphipathic designs were studied: a diblock construct F4R4 and its bolaamphiphile analog R2F4R2. A strong sequence-dependent polymorphism emerges with appearance of globules and vesicle-like assemblies, or flat nanotapes and cylindrical micelles. The diblock construct possesses good cell penetrating capabilities and effectiveness to kill SK-MEL-28 melanoma tumor cells, in contrast to reduced intracellular uptake and low cytotoxicity exhibited by the bolaamphiphilic form. Our findings demonstrate that amphipathic design is a relevant variable for self-assembling SLPs to modulate different cellular responses and may assist in optimizing the production of nanostructures based on arginine-enriched sequences in cell penetrating and antimicrobial peptides.

Folic Acid/Peptides Modified PLGA-PEI-PEG Polymeric Vectors as Efficient Gene Delivery Vehicles: Synthesis, Characterization and Their Biological Performance

Polymeric vectors are safer alternatives for gene delivery owing to their advantages as compared to viral vectors. To improve the stability and transfection efficiency of poly(lactic-co-glycolic acid) (PLGA)- and poly(ethylenimine) (PEI)-based vectors, poly(ethylene glycol) (PEG), folic acid (FA), arginylglycylaspartic acid (RGD) peptides and isoleucine-lysine-valine-alanine-valine (IKVAV) peptides were employed and PLGA-PEI-PEG-FA and PLGA-PEI-PEG-RGD copolymers were synthesized. PLGA-PEI-PEG-FA/DNA, PLGA-PEI-PEG-RGD/DNA and PLGA-PEI-PEG-RGD/IKVAV/DNA nanocomplexes (NCs) were formed through bulk mixing. The structure and properties, including morphology, particle size, surface charge and DNA encapsulation, of NCs were studied. Robust NCs with spherical shape, uniform size distribution and slightly positive charge were able to completely bind DNA above their respective N/P ratios. The critical N/P ratio for PLGA-PEI-PEG-FA/DNA, PLGA-PEI-PEG-RGD/DNA and PLGA-PEI-PEG-RGD/IKVAV/DNA NCs was identified to be 12:1, 8:1 and 10:1, respectively. The covalent modification of PEI through a combination of biodegradable PLGA, hydrophilic PEG and targeting motifs significantly decreased the cytotoxicity of PEI. The developed NCs showed both N/P ratio and cell type-dependent transfection efficiency. An increase in N/P ratio resulted in increased transfection efficiency, and much improved transfection efficiency of NCs was observed above their respective critical N/P ratios. This study provides a promising means to produce polymeric vectors for gene delivery.

Gene therapy for neurodegenerative disorders: advances, insights and prospects

Gene therapy is rapidly emerging as a powerful therapeutic strategy for a wide range of neurodegenerative disorders, including Alzheimer's disease (AD), Parkinson's disease (PD) and Huntington's disease (HD). Some early clinical trials have failed to achieve satisfactory therapeutic effects. Efforts to enhance effectiveness are now concentrating on three major fields: identification of new vectors, novel therapeutic targets, and reliable of delivery routes for transgenes. These approaches are being assessed closely in preclinical and clinical trials, which may ultimately provide powerful treatments for patients. Here, we discuss advances and challenges of gene therapy for neurodegenerative disorders, highlighting promising technologies, targets, and future prospects.

Arginine-Modified Polymers Facilitate Poly (Lactide-Co-Glycolide)-Based Nanoparticle Gene Delivery to Primary Human Astrocytes

PURPOSE

Astrocyte dysfunction is a hallmark of central nervous system injury or infection. As a primary contributor to neurodegeneration, astrocytes are an ideal therapeutic target to combat neurodegenerative conditions. Gene therapy has arisen as an innovative technique that provides excellent prospect for disease intervention. Poly (lactide-co-glycolide) (PLGA) and polyethylenimine (PEI) are polymeric nanoparticles commonly used in gene delivery, each manifesting their own set of advantages and disadvantages. As a clinically approved polymer by the Federal Drug Administration, well characterized for its biodegradability and biocompatibility, PLGA-based nanoparticles (PLGA-NPs) are appealing for translational gene delivery systems. However, our investigations revealed PLGA-NPs were ineffective at facilitating exogenous gene expression in primary human astrocytes, despite their success in other cell lines. Furthermore, PEI polymers illustrate high delivery efficiency but induce cytotoxicity. The purpose of this study is to develop viable and biocompatible NPsystem for astrocyte-targeted gene therapy.

MATERIALS AND METHODS

Successful gene expression by PLGA-NPs alone or in combination with arginine-modified PEI polymers (A_nP_n) was assessed by a luciferase reporter gene encapsulated in PLGA-NPs. Cytoplasmic release and nuclear localization of DNA were investigated using fluorescent confocal imaging with YOYO-labeled plasmid DNA (pDNA). NP-mediated cytotoxicity was assessed via lactate dehydrogenase in primary human astrocytes and neurons.

RESULTS

Confocal imaging of YOYO-labeled pDNA confirmed PLGA-NPs delivered pDNA to the cytoplasm in a dose and time-dependent manner. However, co-staining revealed pDNA delivered by PLGA-NPs did not localize to the nucleus. The addition of A_nP_n significantly improved nuclear localization of pDNA and successfully achieved gene expression in primary human astrocytes. Moreover, these formulations were biocompatible with both astrocytes and neurons.

CONCLUSION

By co-transfecting two polymeric NPs, we developed an improved system for gene delivery and expression in primary human astrocytes. These findings provide a basis for a biocompatible and clinically translatable method to regulate astrocyte function during neurodegenerative diseases and disorders.

Progress in arginine-based gene delivery systems

Arginine based gene delivery systems with enhanced membrane penetration and lower cytotoxicity greatly enrich the gene vectors library and outline a new development direction of gene delivery.

Selective Regulation of Neurons, Glial Cells, and Neural Stem/Precursor Cells by Poly(allylguanidine)-Coated Surfaces

Poly(allylguanidine) (PAG) was synthesized and characterized as a polycationic coating material for culturing neurons, glial cells, and neural stem/precursor cells (NSPCs) to apply PAG for neural tissue engineering. For comparison, poly-d-lysine (PDL), the golden benchmark of the neuron cell culture system, was also used in this study. When PAG was subjected to a mixed culture of neurons and glial cells, cell adhesion and neurite extension of neuronal cells were clearly observed but only few glial cells could be found alongside the neurons. Compared to PDL, the significantly lower density of the glial fibrillary acidic protein-positive cells implied that PAG suppressed the glial cell development. Likewise, PAG was demonstrated to dominate the differentiation of NSPCs principally into neurons. To investigate whether the different effects of PAG and PDL on neuron and glial cell behaviors resulted from the difference of guanidinium cations and ammonium cations, poly-l-arginine (PLA) was included and compared in this study. Similar to PDL, PLA supported high neuron and glial cell viability simultaneously. Consequently, glial cell growth and viability restrained on PAG was not only affected by the side-chain guanidino groups but also by the backbone structure property. The absence of the peptide structure in the backbone of PAG and the conformation of coated PAG on tissue culture polystyrene possibly determined the polycationic biomaterial to limit the growth of glial cells.

Biodegradable Polymers for Gene Delivery

The cellular transport process of DNA is hampered by cell membrane barriers, and hence, a delivery vehicle is essential for realizing the potential benefits of gene therapy to combat a variety of genetic diseases. Virus-based vehicles are effective, although immunogenicity, toxicity and cancer formation are among the major limitations of this approach. Cationic polymers, such as polyethyleneimine are capable of condensing DNA to nanoparticles and facilitate gene delivery. Lack of biodegradation of polymeric gene delivery vehicles poses significant toxicity because of the accumulation of polymers in the tissue. Many attempts have been made to develop biodegradable polymers for gene delivery by modifying existing polymers and/or using natural biodegradable polymers. This review summarizes mechanistic aspects of gene delivery and the development of biodegradable polymers for gene delivery.

Effect of PEGylated Magnetic PLGA-PEI Nanoparticles on Primary Hippocampal Neurons: Reduced Nanoneurotoxicity and Enhanced Transfection Efficiency with Magnetofection

Despite broad application of nanotechnology in neuroscience, the nanoneurotoxicity of magnetic nanoparticles in primary hippocampal neurons remains poorly characterized. In particular, understanding how magnetic nanoparticles perturb neuronal calcium homeostasis is critical when considering magnetic nanoparticles as a nonviral vector for effective gene therapy in neuronal diseases. Here, we address the pressing need to systematically investigate the neurotoxicity of magnetic nanoparticles with different surface charges in primary hippocampal neurons. We found that unlike negative and neutral nanoparticles, positively charged magnetic nanoparticles (magnetic poly(lactic-co-glycolic acid) (PLGA)-polyethylenimine (PEI) nanoparticles, MNP-PLGA-PEI NPs) rapidly elevated cytoplasmic calcium levels in primary hippocampal neurons, mainly via extracellular calcium influx regulated by voltage-gated calcium channels. We went on to show that this perturbation of intracellular calcium homeostasis elicited serious cytotoxicity in primary hippocampal neurons. However, our next experiment demonstrated that PEGylation on the surface of MNP-PLGA-PEI NPs shielded the surface charge, thereby preventing the perturbation of intracellular calcium homeostasis. That is, PEGylated MNP-PLGA-PEI NPs reduced nanoneurotoxicity. Importantly, biocompatible PEGylated MNP-PLGA-PEI NPs under an external magnetic field enhanced transfection efficiency (>7%) of plasmid DNA encoding GFP in primary hippocampal neurons compared to NPs without external magnetic field mediation. Moreover, under an external magnetic field, this system achieved gene transfection in the hippocampus of the C57 mouse. Overall, this study is the first to successfully employ biocompatible PEGylated MNP-PLGA-PEI NPs for transfection using a magnetofection strategy in primary hippocampal neurons, thereby providing a nanoplatform as a new perspective for treating neuronal diseases or modulating neuron activities.

Nucleic Acids Delivery Into the Cells Using Pro-Apoptotic Protein Lactaptin

Cell penetrating peptides (CPP) are promising agents for transporting diverse cargo into the cells. The amino acid sequence and the mechanism of lactaptin entry into the cells allow it to be included into CPP group. Lactaptin, the fragment of human milk kappa-casein, and recombinant lactaptin (RL2) were initially discovered as molecules that induced apoptosis of cultured cancer cells and did not affect non-malignant cells. Here, we analyzed the recombinant lactaptin potency to form complexes with nucleic acids and to act as a gene delivery system. To study RL2-dependent delivery, three type of nucleic acid were used as a models: plasmid DNA (pDNA), siRNA, and non-coding RNA which allow to detect intracellular localization through their functional activity. We have demonstrated that RL2 formed positively charged noncovalent 110-nm-sized complexes with enhanced green fluorescent protein (EGFP)-expressing plasmid DNA. Ca²⁺ ions stabilized these complexes, whereas polyanion heparin displaced DNA from the complexes. The functional activity of delivered nucleic acids were assessed by fluorescent microscopy using A549 lung adenocarcinoma cells and A431 epidermoid carcinoma cells. We observed that RL2:pDNA complexes provided EGFP expression in the treated cells and that strongly confirmed the entering pDNA into the cells. The efficiency of cell transformation by these complexes increased when RL2:pDNA ratio increased. Pre-treatment of the cells with anti-RL2 antibodies partly inhibited the entry of pDNA into the cells. RL2-mediated delivery of siRNA against EGFP was analyzed when A549 cells were co-transfected with EGFP-pDNA and RL2:siRNA complexes. siRNA against EGFP efficiently inhibited the expression of EGFP being delivered as RL2:siRNA complexes. We have previously demonstrated that non-coding U25 small nucleolar RNA (snoRNA) can decrease cell viability. Cancer cell transfection with RL2-snoRNA U25 complexes lead to a substantial decrease of cell viability, confirming the efficiency of snoRNA U25 delivery. Collectively, these findings indicate that recombinant lactaptin is able to deliver noncovalently associated nucleic acids into cancer cells in vitro.

Recent advances in polymeric materials for the delivery of RNA therapeutics

Introduction: The delivery of nucleic acid therapeutics through non-viral carriers face multiple biological barriers that reduce their therapeutic efficiency. Despite great progress, there remains a significant technological gap that continues to limit clinical translation of these nanocarriers. A number of polymeric materials are being exploited to efficiently deliver nucleic acids and achieve therapeutic effects. Areas covered: We discuss the recent advances in the polymeric materials for the delivery of nucleic acid therapeutics. We examine the use of common polymer architectures and highlight the challenges that exist for their development from bench side to clinic. We also provide an overview of the most notable improvements made to circumvent such challenges, including structural modification and stimuli-responsive approaches, for safe and effective nucleic acid delivery. Expert opinion: It has become apparent that a universal carrier that follows 'one-size' fits all model cannot be expected for delivery of all nucleic acid therapeutics. Carriers need to be designed to exhibit sensitivity and specificity toward individual targets diseases/indications, and relevant subcellular compartments, each of which possess their own unique challenges. The ability to devise synthetic methods that control the molecular architecture enables the future development that allow for the construction of 'intelligent' designs.

Effectiveness of Small Interfering RNA Delivery via Arginine-Rich Polyethylenimine-Based Polyplex in Metastatic and Doxorubicin-Resistant Breast Cancer Cells

Poor cellular uptake, rapid degradation in the presence of serum, and inefficient transfection are some of the major barriers in achieving therapeutic efficacy of naked small interfering RNAs (siRNAs). We investigated the efficacy of the polyplex formulated using our synthesized polymer, polyethylene glycol (PEG)-modified l-arginine oligo(-alkylaminosiloxane) that is grafted with poly(ethyleneimine) (PEI) for siRNA delivery. We hypothesized that the polyplex formulated using the polymer with a balanced composition of PEI for siRNA condensation and its protection, PEG for polyplex stability and to minimize the PEI-associated toxicity, and with arginine facilitating cellular uptake would overcome the aforementioned issues with siRNA delivery. We tested our hypothesis using antiluciferase siRNA in luciferase-expressing metastatic breast cancer cells (MDA-MB-231-Luc-D3H2LN) and anti-ABCB1 siRNA against an efflux membrane protein, ABCB1, in doxorubicin (DOX)-resistant breast cancer cells (MCF-7/Adr). The results demonstrated that the polyplex at an optimal nucleotide/polymer ratio is stable in the presence of excess polyanions, has no cellular toxicity, and protects siRNA from RNase degradation. Transfection of MDA-MB-231-Luc-D3H2LN cells with antiluciferase siRNA polyplex showed almost complete knockdown of luciferase expression. In MCF-7/Adr cells, transfection with anti-ABCB1 siRNA effectively downregulated its target efflux protein, ABCB1; increased cellular uptake of DOX; and enhanced its cytotoxic effect. However, the cotreatment did not completely overcome drug resistance, suggesting that further optimization is needed and/or a mechanism(s) other than the efflux protein ABCB1 may be involved in drug resistance. In conclusion, our polyplex is effective for siRNA delivery and can be explored for different therapeutic applications.

Structure optimization of dendritic lipopeptide based gene vectors with the assistance from molecular dynamic simulation

Disulfide modified lipopeptide assemblies with an arginine-rich dendritic periphery provide a promising platform for effective gene transfer. Dendritic arginine peptides that mimic the cell-penetrating peptides of a virus envelope are vital for complexation, interaction with physical barriers, and final gene release. Here, we report three lipopeptides with different-generation dendritic peripheries (R₁LS, R₂LS and R₃LS), each of which contains a dioleoyl-l-lysinate hydrophobic tail. Such molecules were proven to self-assemble in aqueous solution with different morphologies, sizes, and surface zeta potentials. R₂LS and R₃LS assemblies showed spherical and spindle shapes with zeta potentials of 27.2 and 32.8 mV, respectively. They exhibited complete condensation of pDNA at a low N/P ratio, while R₁LS assemblies displayed a fiber pattern with a relatively low electric potential of 10.9 mV with poor DNA binding ability. In a cellular viability experiment, R₁LS and R₂LS have no significant cytotoxicity even at high dosage, while R₃LS showed conspicuous toxicity. As a gene vector, R₂LS presented high gene transfection efficiency either in the presence or the absence of serum, which was 58.7% greater than liposome 2000 and PEI in the condition of 10% fetal bovine serum for HeLa cells. While R₃LS showed good results just without serum and R₁LS was unserviceable in all situations. Moreover, molecular dynamic simulation was exploited to analyze the kinestate of the signal molecule and the interactions of multiple molecules, which could assist us in better understanding the experimental phenomena. The simulation results indicated that the R₂LS molecule has better flexibility, which was favorable for interaction with the cell membrane. And it could generate tight integration in self-assembly while R₁LS and R₃LS assemblies have a large molecular interval, which led to a controllable release of cargos for R₂LS in a reductive environment. In summary, the generation of the dendrimer in lipopeptides is vital for the gene transfer effect. For optimization, it is necessary to study the structure-function relationship, and molecular dynamic simulation is an effective strategy for screening the molecular structure and even for predicting experimental results.

Application of dextran as nanoscale drug carriers

Dextran is a kind of biocompatible, nontoxic and nonimmunogenic biological substance that has been widely used in drug-delivery systems. With further research and understanding of dextran and its derivatives, people can more precisely control the sequence of dextran by chemical and biosynthetic methods as needed, and modify various structures to improve the properties of dextran, such as hydrophilicity, hydrophobicity, temperature sensitivity, pH sensitivity and ionic strength sensitivity, which will further expand the application of dextran and its derivatives in drug-delivery systems. Herein, the application of dextran and its derivatives in gene transfection and drug delivery was summarized and analyzed, and the problems were studied. At the same time, its application prospects are forecasted.

Reaching for the Stars in the Brain: Polymer-Mediated Gene Delivery to Human Astrocytes

Astrocytes, the "star-shaped" glial cells, are appealing gene-delivery targets to treat neurological diseases due to their diverse roles in brain homeostasis and disease. Cationic polymers have successfully delivered genes to mammalian cells and hence present a viable, non-immunogenic alternative to widely used viral vectors. In this study, we investigated the gene delivery potential of a series of arginine- and polyethylene glycol-modified, siloxane-based polyethylenimine analogs in primary cultured human neural cells (neurons and astrocytes) and in mice. Plasmid DNAs encoding luciferase reporter were used to measure gene expression. We hypothesized that polyplexes with arginine would help in cellular transport of the DNA, including across the blood-brain barrier; polyethylene glycol will stabilize polyethylenimine and reduce its toxicity while maintaining its DNA-condensing ability. Polyplexes were non-toxic to human neural cells and red blood cells. Cellular uptake of polyplexes and sustained gene expression were seen in human astrocytes as well as in mouse brains post-intravenous-injections. The polyplexes also delivered and expressed genes driven by astrocyte-restricted glial fibrillary acidic protein promoters, which are weaker than viral promoters. To our knowledge, the presented work validates a biocompatible and effective polymer-facilitated gene-delivery system for both human brain cells and mice for the first time.

Neuroprotective Effect of Tetrahedral DNA Nanostructures in a Cell Model of Alzheimer's Disease

Accumulating evidence supports the abnormal deposition of amyloid β-peptide (Aβ) as the main cause of Alzheimer's disease (AD). Therefore, fighting against the formation, deposition, and toxicity of Aβ is a basic strategy for the treatment of AD. In the process of in vitro nerve cell culture, screening out drugs that can antagonize a series of toxic reactions caused by β-amyloid deposition has become an effective method for the follow-up treatment of AD. Our previous studies showed that tetrahedral DNA nanostructures (TDNs) had good biocompatibility and had some positive effects on the biological behavior of cells. In this study, the main aim of our work was to explore the effects and potential mechanism of TDNs in protecting neuronal PC12 cells from the toxicity of Aβ. Our study demonstrated that TDNs can protect and rescue PC12 cell death through Aβ25-35-induced PC12 cell apoptosis. Further studies showed that TDNs significantly improved the apoptosis by affecting the abnormal cell cycle, restoring abnormal nuclear morphology and caspase activity. Western blot analysis showed that TDNs could prevent the damage caused by Aβ deposition by activating the ERK1/2 pathway and thus be a potential therapeutic agent with a neuroprotective effect in Alzheimer's disease. Our finding provides a potential application of TDNs in the prevention and treatment of AD.

Effects of sucrose ester structures on liposome-mediated gene delivery

Sucrose esters (SEs) have great potential applications in gene delivery because of their low toxicity, excellent biocompatibility, and biodegradability. By using tripeptide-based lipid (CDO) as a model lipid and SEs as helper lipids, a series of liposomes were prepared. The SEs with hydrophilic-lipophilic balance (HLB) values of 1, 6, 11, or 16 and the fatty acids of laurate, stearate, or oleate were used in the liposomes. We investigated the effect of HLB values of SEs and fatty acid types on gene transfection efficiency and toxicity of liposomes. The results showed that transfection efficiencies of the liposomes containing SEs with HLB value of 6 were superior to other liposomes in HeLa, MCF-7, NCI-H460, and A549 tumor cells. For the same HLB value, liposomes of laurate SEs were preferable to transfect cells compared to SEs of stearate and oleate. The liposomes with SEs showed higher cellular uptake than liposome without SEs (LipoCDO). LipoL12-6/Luc-siRNA treatment on tumor-bearing mice exhibited about 60% in vivo gene silencing of luciferase, and LipoL12-6 could mediate IGF-1R siRNA to greatly inhibit tumor growth. Moreover, liposomes with SEs revealed remarkably low toxicity in vitro and in vivo. The illustration of SE structures on gene delivery will promote the use of SEs for clinical trials of liposomes.

STATEMENT OF SIGNIFICANCE

This article is the first to study the effects of various chain lengths and hydrophilic-lipophilic balance (HLB) of sucrose esters (SEs) on gene transfection efficiency and safety of liposomes for gene delivery. The in vitro delivery of pDNA and siRNA by lipoplexes against HeLa, MCF-7, NCI-H460, and A549 tumor cells showed that the lipoplexes could lead to better transfection and lower cytotoxicity after the addition of SEs. SEs with shorter chain and a median HLB value could provide the liposomes with much higher gene transfection efficiency than others. The in vivo delivery of siRNA to tumor-bearing mice further confirmed that liposome containing laurate SE (LipoL12-6) could be a potential therapeutic vector, as it delivered siRNA to silence nearly 60% of the luciferase in tumors and also greatly inhibited the tumor growth. Therefore, the addition of SEs to liposomes proved to be relatively safe in vitro and in vivo. These preliminary results demonstrated that SEs show great potential for constructing controlled-release systems for gene delivery. The readers will get insights into a series of gene vectors and deepen their understanding about gene delivery.

Tau peptides and tau mutant protein aggregation inhibition by cationic polyethyleneimine and polyarginine

Tau protein plays a major role in Alzheimer's disease. The tau protein loses its functionality by self-aggregation due to the two six-amino acid sequences VQIVYK and VQIINK of the protein. Hence it is imperative to find therapeutics that could inhibit the self-aggregation of this tau peptide fragments. Here, we study the inhibitory potential of a cationic polymer polyethyleneimine (PEI) and a cationic polypeptide arginine (Arg) on the aggregation of VQIVYK, and GKVQIINKLDL peptides, and tau mutant protein (P301L), found frequently in taupathy. Various characterization methods are employed including thioflavin S, transmission electron microscopy, and dynamic light scattering to study the aggregation/inhibition process in vitro. Results show that PEI and Arg significantly inhibit tau peptides and protein aggregation. The study could be applied to understand tau protein aggregation mechanism in the presence of cationic polymers.

Effect of tetrahedral DNA nanostructures on proliferation and osteo/odontogenic differentiation of dental pulp stem cells via activation of the notch signaling pathway

Dental pulp stem cells (DPSCs) derived from the human dental pulp tissue have multiple differentiation capabilities, such as osteo/odontogenic differentiation. Therefore, DPSCs are deemed as ideal stem cell sources for tissue regeneration. As new nanomaterials based on DNA, tetrahedral DNA nanostructures (TDNs) have tremendous potential for biomedical applications. Here, the authors aimed to explore the part played by TDNs in proliferation and osteo/odontogenic differentiation of DPSCs, and attempted to investigate if these cellular responses could be driven by activating the canonical Notch signaling pathway. Upon exposure to TDNs, proliferation and osteo/odontogenic differentiation of DPSCs were dramatically enhanced, accompanied by up regulation of Notch signaling. In general, our study suggested that TDNs can significantly promote proliferation and osteo/odontogenic differentiation of DPSCs, and this remarkable discovery can be applied in tissue engineering and regenerative medicine to develop a significant and novel method for bone and dental tissue regeneration.

Effects of tetrahedral DNA nanostructures on autophagy in chondrocytes

Tetrahedral DNA nanostructures (TDNs) have gathered great attention and are being widely used in biomedicine.

Collapse of DNA in packaging and cellular transport

The dawn of molecular biology and recombinant DNA technology arose from our ability to manipulate DNA, including the process of collapse of long extended DNA molecules into nanoparticles of approximately 100 nm diameter. This condensation process is important for the packaging of DNA in the cell and for transporting DNA through the cell membrane for gene therapy. Multivalent cations, such as natural polyamines (spermidine and spermine), were initially recognized for their ability to provoke DNA condensation. Current research is targeted on molecules such as linear and branched polymers, oligopeptides, polypeptides and dendrimers that promote collapse of DNA to nanometric particles for gene therapy and on the energetics of DNA packaging.

Enhanced antitumor efficacy of arginine modified amphiphilic nanoparticles co-delivering doxorubicin and iSur-pDNA via the multiple synergistic effect

Arginine and α-tocopherol succinate (α-TOS) double grafted N-trimethyl chitosan chloride (TMC) nanoparticles (TAS NPs) were designed and developed for effective co-delivery of doxorubicin (DOX) and Survivin shRNA-expressing pDNA (iSur-pDNA). With DOX loading into the hydrophobic core and iSur-pDNA combining to the hydrophilic shell, TAS/DOX/pDNA NPs demonstrated favorable structural stability and sustained release properties in vitro. With the special non-clathrin-dependent endocytosis, TAS/DOX/pDNA NPs presented higher cellular uptake and mainly distributed in ER and Golgi rather than lysosomes following internalization. The in vitro nuclear localization, gene silencing efficiency, cell apoptosis, and growth inhibition of tumor cells were significantly promoted by arginine modification. In the tumor-bearing mice model, TAS/DOX/pDNA NPs possessed the maximum antitumor efficiency as compared with single delivery of DOX or iSur-pDNA. Particularly, blank TAS NPs were selectively be toxic to tumor cells as evidenced by their capabilities to inhibit proliferation and induce apoptosis of tumor cells. The promising tumor treatment of TAS/DOX/pDNA NPs via a multiple synergistic manner arising from DOX and pDNA as well as the vectors would provide a potential strategy for a dual-delivery system to improve their therapeutic efficacies.

Polyethylenimine Nanoparticle-Mediated siRNA Delivery to Reduce α-Synuclein Expression in a Model of Parkinson's Disease

RNA interference (RNAi)-based strategies that mediate the specific knockdown of target genes by administration of small interfering RNAs (siRNAs) could be applied for treatment of presently incurable neurodegenerative diseases such as Parkinson’s disease. However, inefficient delivery of siRNA into neurons hampers in vivo application of RNAi. We have previously established the 4–12 kDa branched polyethylenimine (PEI) F25-LMW with superior transfection efficacy for delivery of siRNA in vivo. Here, we present that siRNA complexed with this PEI extensively distributes across the CNS down to the lumbar spinal cord after a single intracerebroventricular infusion. siRNA against α-synuclein (SNCA), a pre-synaptic protein that aggregates in Parkinson’s disease, was complexed with PEI F25-LMW and injected into the lateral ventricle of mice overexpressing human wild-type SNCA (Thy1-aSyn mice). Five days after the single injection of 0.75 μg PEI/siRNA, SNCA mRNA expression in the striatum was reduced by 65%, accompanied by reduction of SNCA protein by ∼50%. Mice did not show signs of toxicity or adverse effects. Moreover, ependymocytes and brain parenchyma were completely preserved and free of immune cell invasion, astrogliosis, or microglial activation. Our results support the efficacy and safety of PEI nanoparticle-mediated delivery of siRNA to the brain for therapeutic intervention.

Enhanced non-viral gene delivery by coordinated endosomal release and inhibition of β-tubulin deactylase

Efficient non-viral gene delivery is highly desirable but often unattainable with some cell-types. We report here that non-viral DNA polyplexes can efficiently transfect differentiated neuronal and stem cells. Polyplex transfection centrifugation protocols was enhanced by including a simultaneous treatment with a DOPE/CHEMS lipid suspension and a microtubule inhibitor, Tubastatin A. Lipoplex transfection protocols were not improved by this treatment. This mechanism of action was unravelled by systematically identifying and rationally mitigating barriers limiting high transfection efficiency, allowing unexpected improvements in the transfection of mesenchymal stem cells (MSC), primary neuron and several hard-to-transfect cell types beyond what are currently achievable using cationic polymers. The optimized formulation and method achieved high transfection efficiency with no adverse effects on cell viability, cell proliferation or differentiation. High efficiency modification of MSC for cytokine overexpression, efficient generation of dopaminergic neuron using neural stem cells and enhanced genome editing with CRISPR-Cas9 were demonstrated. In summary, this study described a cost-effective method for efficient, rapid and scalable workflow for ex vivo gene delivery using a myriad of nucleic acids including plasmid DNA, mRNA, siRNA and shRNA.

Effect of tetrahedral DNA nanostructures on osteogenic differentiation of mesenchymal stem cells via activation of the Wnt/β-catenin signaling pathway

Adipose-derived stem cells (ADSCs) are considered to be ideal stem cell sources for bone regeneration owing to their ability to differentiate into osteo-like cells. Therefore, they have attracted increasing attention in recent years. Tetrahedral DNA nanostructures (TDNs), a new type of DNA-based biomaterials, have shown great potential for biomedical applications. In the present work, we aimed to investigate the role played by TDNs in osteogenic differentiation and proliferation of ADSCs and tried to explore if the canonical Wnt signal pathway could be the vital biological mechanism driving these cellular responses. Upon exposure to TDNs, ADSCs proliferation and osteogenic differentiation were significantly enhanced, accompanied by the up-regulation of genes correlated with the Wnt/β-catenin pathway. In conclusion, our results indicate that TDNs are crucial regulators of the increase in osteogenic potential and ADSCs proliferation, and this noteworthy discovery could provide a promising novel approach toward ADSCs-based bone defect regeneration.

Destination Brain: the Past, Present, and Future of Therapeutic Gene Delivery

Neurological diseases and disorders (NDDs) present a significant societal burden and currently available drug- and biological-based therapeutic strategies have proven inadequate to alleviate it. Gene therapy is a suitable alternative to treat NDDs compared to conventional systems since it can be tailored to specifically alter select gene expression, reverse disease phenotype and restore normal function. The scope of gene therapy has broadened over the years with the advent of RNA interference and genome editing technologies. Consequently, encouraging results from central nervous system (CNS)-targeted gene delivery studies have led to their transition from preclinical to clinical trials. As we shift to an exciting gene therapy era, a retrospective of available literature on CNS-associated gene delivery is in order. This review is timely in this regard, since it analyzes key challenges and major findings from the last two decades and evaluates future prospects of brain gene delivery. We emphasize major areas consisting of physiological and pharmacological challenges in gene therapy, function-based selection of a ideal cellular target(s), available therapy modalities, and diversity of viral vectors and nanoparticles as vehicle systems. Further, we present plausible answers to key questions such as strategies to circumvent low blood-brain barrier permeability and most suitable CNS cell types for targeting. We compare and contrast pros and cons of the tested viral vectors in the context of delivery systems used in past and current clinical trials. Gene vector design challenges are also evaluated in the context of cell-specific promoters. Key challenges and findings reported for recent gene therapy clinical trials, assessing viral vectors and nanoparticles are discussed from the perspective of bench to bedside gene therapy translation. We conclude this review by tying together gene delivery challenges, available vehicle systems and comprehensive analyses of neuropathogenesis to outline future prospects of CNS-targeted gene therapies.

Nanoparticulate strategies for the treatment of polyglutamine diseases by halting the protein aggregation process

Polyglutamine (polyQ) diseases are a class of neurodegenerative disorders that cause cellular dysfunction and, eventually, neuronal death in specific regions of the brain. Neurodegeneration is linked to the misfolding and aggregation of expanded polyQ-containing proteins, and their inhibition is one of major therapeutic strategies used commonly. However, successful treatment has been limited to date because of the intrinsic properties of therapeutic agents (poor water solubility, low bioavailability, poor pharmacokinetic properties), and difficulty in crossing physiological barriers, including the blood-brain barrier (BBB). In order to solve these problems, nanoparticulate systems with dimensions of 1-1000 nm able to incorporate small and macromolecules with therapeutic value, to protect and deliver them directly to the brain, have recently been developed, but their use for targeting polyQ disease-mediated protein misfolding and aggregation remains scarce. This review provides an update of the polyQ protein aggregation process and the development of therapeutic strategies for halting it. The main features that a nanoparticulate system should possess in order to enhance brain delivery are discussed, as well as the different types of materials utilized to produce them. The final part of this review focuses on the potential application of nanoparticulate system strategies to improve the specific and efficient delivery of therapeutic agents to the brain for the treatment of polyQ diseases.

Peptides, polypeptides and peptide–polymer hybrids as nucleic acid carriers

Peptide, polypeptide and polymer–peptide hybrid based nucleic acid therapeutics (NAT).

Effect of inserted spacer in hepatic cell-penetrating multifunctional peptide component on the DNA intracellular delivery of quaternary complexes based on modular design

A safe and efficient quaternary gene delivery system (named Q-complexes) was constructed based on self-assembly of molecules through noncovalent bonds. This system was formulated through the cooperation and competing interactions of cationic liposomes, multifunctional peptides, and DNA, followed by coating hyaluronic acid on the surface of the ternary complexes. The multifunctional peptide was composed of two functional domains: penetrating hepatic tumor-targeted cell moiety (KRPTMRFRYTWNPMK) and a wrapping gene sequence (polyarginine 16). The effect of spacer insertion between the two domains of multifunctional peptide on the intracellular transfection of Q-complexes was further studied. Experimental results showed that the formulations assembled with various peptides in the spacer elements possessed different intercellular pathways and transfection efficiencies. The Q-complexes containing peptide in the absence of spacer element (P_a) showed the highest gene expression among all samples. The Q-complexes containing peptides with a noncleavable spacer GA (P_c) had no ability of intracellular nucleic acid delivery, whereas those with a cleavable spacer RVRR (P_d) showed moderate transfection activity. These results demonstrated that the different spacers inserted in the multifunctional peptide played an important role in in vitro DNA transfection efficiency. Atomic force microscopy images showed that the morphologies of ternary complexes (LP_cD) and Q-complexes (HL_cPD) were crystal lamellas, whereas those of other nanocomplexes were spheres. Circular dichroism showed the changed configuration of peptide with spacer GA in nanocomplexes compared with that of its free state, whereas the P_a configuration without spacer in nanocomplexes was consistent with that of its free state. The present study contributed to the structural understanding of Q-complexes, and further effective modification is in progress.

Lipoic acid functionalized amino acids cationic lipids as gene vectors

A series of reducible cationic lipids 4a-4f with different amino acid polar-head groups were prepared. The novel lipid contains a hydrophobic lipoic acid (LA) moiety, which can be reduced under reductive conditions to release of the encapsulated plasmid DNA. The particle size, zeta potential and cellular uptake of lipoplexes formed with DNA, as well as the transfection efficacy (TE) were characterized. The TE of the cationic lipid based on arginine was especially high, and was 2.5times higher than that of a branched polyethylenimine in the presence of 10% serum.

A block copolymer containing PEG and histamine-like segments: well-defined functions for gene delivery

PEG-b-PAMPImB with well-defined functions, including high colloidal stability, effective DNA condensation and buffering capacity, self-assembles with pDNA for lower toxicity and higher efficient gene transfection.

Establishment of Lipofection Protocol for Efficient miR-21 Transfection into Cortical Neurons In Vitro

Dysregulated microRNAs in neurons could cause many nervous system diseases. The therapeutic manipulation of these pathogenic microRNAs necessitates novel, efficient delivery systems to facilitate microRNA modulators targeting neurons with minimal off-target effects. The study aimed to establish a lipofection protocol to upregulate expression levels of miR-21 in neurons under different conditions, including different serum-free medium, transfection conditions, and reagent concentration, by evaluating the expression levels of miR-21 and neuron injury. The expression levels of miR-21 were higher in neurons transfected by Neurobasal-A than by DMEM. Expression levels of miR-21 were already the highest at the ratio RNAiMAX:miR-21 = 3:5, but the increase of RNAiMAX's concentration had not caused the further upregulation of expression level of miR-21. Neuron injury was condition dependent and dose dependent after transfection. Compared to S-Neurobasal groups, neurons have a smaller injury in N-Neurobasal groups, and compared to ratios RNAiMAX:miR-21 = 4:5, 5:5, neuron injury was smaller at ratios of RNAiMAX:miR-21 = 1:5, 2:5, 3:5. Without the pretreatment of starvation in vitro, the lipofection protocol was that RNAiMAX/miR-21 agomir complexes were diluted in Neurobasal-A at the ratio of RNAiMAX:miR-21 = 3:5.