Synergistic effect of amino acids modified on dendrimer surface in gene delivery

Delivery of mRNA with Histidine-Lysine Peptides

Transfection with mRNA has been considered superior to that with plasmids since the mRNA can be translated to a protein in the cytosol without entering the nucleus. One disadvantage of using mRNA is its susceptibility to enzymatic biodegradability, and consequently, significant research has occurred to determine nonviral carriers that will sufficiently stabilize this nucleic acid for cellular transport. Histidine-lysine peptides (HK) are one such class of mRNA carriers, which we think serves as a model for other peptides and polymeric carrier systems. When the HK peptide and mRNA are mixed and interact through ionic and nonionic bonds, mRNA polyplexes are formed, which can transfect cells. In contrast to linear HK peptides, branched HK peptides protected and efficiently transfected mRNA into cells. After describing the preparation and biophysical characterization of these polyplexes, we will provide protocols for in vitro and in vivo transfection for these mRNA polyplexes.

Cationic Materials for Gene Therapy: A Look Back to the Birth and Development of 2,2-Bis-(hydroxymethyl)Propanoic Acid-Based Dendrimer Scaffolds

Gene therapy is extensively studied as a realistic and promising therapeutic approach for treating inherited and acquired diseases by repairing defective genes through introducing (transfection) the "healthy" genetic material in the diseased cells. To succeed, the proper DNA or RNA fragments need efficient vectors, and viruses are endowed with excellent transfection efficiency and have been extensively exploited. Due to several drawbacks related to their use, nonviral cationic materials, including lipidic, polymeric, and dendrimer vectors capable of electrostatically interacting with anionic phosphate groups of genetic material, represent appealing alternative options to viral carriers. Particularly, dendrimers are highly branched, nanosized synthetic polymers characterized by a globular structure, low polydispersity index, presence of internal cavities, and a large number of peripheral functional groups exploitable to bind cationic moieties. Dendrimers are successful in several biomedical applications and are currently extensively studied for nonviral gene delivery. Among dendrimers, those derived by 2,2-bis(hydroxymethyl)propanoic acid (b-HMPA), having, unlike PAMAMs, a neutral polyester-based scaffold, could be particularly good-looking due to their degradability in vivo. Here, an overview of gene therapy, its objectives and challenges, and the main cationic materials studied for transporting and delivering genetic materials have been reported. Subsequently, due to their high potential for application in vivo, we have focused on the biodegradable dendrimer scaffolds, telling the history of the birth and development of b-HMPA-derived dendrimers. Finally, thanks to a personal experience in the synthesis of b-HMPA-based dendrimers, our contribution to this field has been described. In particular, we have enriched this work by reporting about the b-HMPA-based derivatives peripherally functionalized with amino acids prepared by us in recent years, thus rendering this paper original and different from the existing reviews.

MicroRNA-224-5p nanoparticles balance homeostasis via inhibiting cartilage degeneration and synovial inflammation for synergistic alleviation of osteoarthritis

MicroRNAs play a crucial role in regulating cartilage extracellular matrix (ECM) metabolism and are being explored as potential therapeutic targets for osteoarthritis (OA). The present study indicated that microRNA-224-5p (miR-224-5p) could balance the homeostasis of OA via regulating cartilage degradation and synovium inflammatory simultaneously. Multifunctional polyamidoamine dendrimer with amino acids used as efficient vector to deliver miR-224-5p. The vector could condense miR-224-5p into transfected nanoparticles, which showed higher cellular uptake and transfection efficiency compared to lipofectamine 3000, and also protected miR-224-5p from RNase degradation. After treatment with the nanoparticles, the chondrocytes showed an increase in autophagy rate and ECM anabolic components, as evidenced by the upregulation of autophagy-related proteins and OA-related anabolic mediators. This led to a corresponding inhibition of cell apoptosis and ECM catabolic proteases, ultimately resulting in the alleviation of ECM degradation. In addition, miR-224-5p also inhibited human umbilical vein endothelial cells angiogenesis and fibroblast-like synoviocytes inflammatory hyperplasia. Integrating the above synergistic effects of miR-224-5p in regulating homeostasis, intra-articular injection of nanoparticles performed outstanding therapeutic effect by reducing articular space width narrowing, osteophyte formation, subchondral bone sclerosis and inhibiting synovial hypertrophy and proliferation in the established mouse OA model. The present study provides a new therapy target and an efficient intra-articular delivery method for improving OA therapy. STATEMENT OF SIGNIFICANCE: Osteoarthritis (OA) is the most prevalent joint disease worldwide. Gene therapy, which involves delivering microRNAs, has the potential to treat OA. In this study, we demonstrated that miR-224-5p can simultaneously regulate cartilage degradation and synovium inflammation, thereby restoring homeostasis in OA gene therapy. Moreover, compared to traditional transfection reagents such as lipofectamine 3000, G5-AHP showed better efficacy in both microRNA transfection and protection against degradation due to its specific surface structure. In summary, G5-AHP/miR-224-5p was developed to meet the clinical needs of OA patients and the high requirement of gene transfection efficiency, providing a promising paradigm for the future application and development of gene therapy.

Precise and systematic end group chemistry modifications on PAMAM and poly(l-lysine) dendrimers to improve cytosolic delivery of mRNA

Here, we aimed to chemically modify PAMAM dendrimers using lysine as a site-selective anchor for successfully delivering mRNA while maintaining a low toxicity profile. PAMAM dendrimers were multi-functionalised by amidation reactions in a regioselective, quantitative and stepwise manner with carefully selected property-modifying surface groups. Alternatively, novel lysine-based dendrimers were prepared in the same manner with the aim to unlock their potential in gene delivery. The modified dendrimers were then formulated with Cy5-EGFP mRNA by bulk mixing via liquid handling robotics across different nitrogen to phosphate ratios. The resulting dendriplexes were characterised by size, charge, mRNA encapsulation, and mRNA binding affinity. Finally, their in-vitro delivery activity was systematically investigated across key cellular trafficking stages to relate chemical design to cellular effect. We demonstrate our findings in different cell lines and benchmarked relative to a commercially available transfection agent, jetPEI®. We demonstrate that specific surface modifications are required to generate small, reliable and well-encapsulated positively charged dendriplex complexes. Furthermore, we show that introduction of fusogenic groups is essential for driving endosomal escape and achieving cellular delivery and translation of mRNA in these cell lines.

Functionalized PAMAM constructed nanosystems for biomacromolecule delivery

Polyamidoamines (PAMAMs) are a class of dendrimer with monodispersity and controlled topology, which can deliver biologically active macromolecules (e.g., genes and proteins) to specific regions with high efficiency and minimum side effects. In detail, PAMAMs can be functionalized easily by core modification or surface amendment to encapsulate a wide range of biomacromolecules. Besides, self-assembled, cross-linked and hybrid PAMAMs with customized therapeutic purposes are developed as delivery vehicles, which makes PAMAMs promising for biomacromolecule therapy. In this review, we comprehensively summarize the application of PAMAMs in biomacromolecule delivery from the synthesis of functionalized PAMAM carriers to the development of PAMAM-based drug delivery systems. The underlying strategies for PAMAM functionalization and assembly are first systematically discussed, and then the current applications of PAMAMs for biomacromolecule delivery are reviewed. Finally, a brief perspective on the further applications of PAMAMs concludes, aiming to provide insights into developing PAMAM-based biomacromolecule delivery systems.

NMR Studies of Two Lysine Based Dendrimers with Insertion of Similar Histidine-Arginine and Arginine-Histidine Spacers Having Different Properties for Application in Drug Delivery

In this paper we study two lysine-based peptide dendrimers with Lys-His-Arg and Lys-Arg-His repeating units and terminal lysine groups. Combination of His and Arg properties in a dendrimer could be important for biomedical applications, especially for prevention of dendrimer aggregation and for penetration of dendrimers through various cell membranes. We describe the synthesis of these dendrimers and the confirmation of their structure using 1D and 2D Nuclear Magnetic Resonance (NMR) spectroscopy. NMR spectroscopy and relaxation are used to study the structural and dynamic properties of these macromolecules and to compare them with properties of previously studied dendrimers with Lys-2Arg and Lys-2His repeating units. Our results demonstrate that both Lys-His-Arg and Lys-Arg-His dendrimers have pH sensitive conformation and dynamics. However, properties of Lys-His-Arg at normal pH are more similar to those of the more hydrophobic Lys-2His dendrimer, which has tendency towards aggregation, while the Lys-Arg-His dendrimer is more hydrophilic. Thus, the conformation with the same amino acid composition of Lys-His-Arg is more pH sensitive than Lys-Arg-His, while the presence of Arg groups undoubtedly increases its hydrophilicity compared to Lys-2His. Hence, the Lys-His-Arg dendrimer could be a more suitable (in comparison with Lys-2His and Lys-Arg-His) candidate as a pH sensitive nanocontainer for drug delivery.

Multifunctional amphiphilic peptide dendrimer as nonviral gene vectors for effective cancer therapy via combined gene/photodynamic therapies

Gene therapy holds great promise for treatment of gene-associated diseases. However, safe and successful clinical application urgently requires further advancement of constructing efficient delivery systems. Herein, three amphiphilic peptide dendrimers (TTC-L-KRR/KKK/KHH), containing the natural amino acid residues (lysine K, arginine R, and histidine H) and AIE-based photosensitizer (tetraphenylethenethiophene modified cyanoacrylate, TTC) modified with alkyl chain (L), have been designed and prepared for improving therapeutic potency via the combination of gene therapy (GT) and photodynamic therapy (PDT). All three compounds possessed typical aggregation-induced emission (AIE) characteristics and ultralow critical micelle concentrations (CMCs). The liposomes consisting of amphiphilic peptide dendrimers and dioleoylphosphatidylethanolamine (DOPE) can effectively bind DNA into nanoparticles with appropriate sizes, regular morphology and good biocompatibility. Among them, liposomes TTC-L-KKK/DOPE exhibited the highest transfection efficiency up to 5.7-fold as compared with Lipo2000 in HeLa cells. Meanwhile, rapid endocytosis, successful endo/lysosomal escape, gene release and rapid nuclear delivery of DNA revealed the superiority of liposomes TTC-L-KKK/DOPE during gene delivery process. More importantly, efficient reactive oxygen species (ROS) generation by TTC-L-KKK/DOPE led to effective PDT, thus improving therapeutic potency via combining with p53 mediated-gene therapy. Our work brought novel insight and direction for the construction of bio-safe and bio-imaging liposome as the multifunctional nonviral gene vectors for the effective combined gene/photodynamic therapies.

Dendrimers as nanoscale vectors: Unlocking the bars of cancer therapy

Chemotherapy is the first choice in the treatment of cancer and is always preferred to other approaches such as radiation and surgery, but it has never met the need of patients for a safe and effective drug. Therefore, new advances in cancer treatment are now needed to reduce the side effects and burdens associated with chemotherapy for cancer patients. Targeted treatment using nanotechnology are now being actively explored as they could effectively deliver therapeutic agents to tumor cells without affecting normal cells. Dendrimers are promising nanocarriers with distinct physiochemical properties that have received considerable attention in cancer therapy studies, which is partly due to the numerous functional groups on their surface. In this review, we discuss the progress of different types of dendrimers as delivery systems in cancer therapy, focusing on the challenges, opportunities, and functionalities of the polymeric molecules. The paper also reviews the various role of dendrimers in their entry into cells via endocytosis, as well as the molecular and inflammatory pathways in cancer. In addition, various dendrimers-based drug delivery (e.g., pH-responsive, enzyme-responsive, redox-responsive, thermo-responsive, etc.) and lipid-, amino acid-, polymer- and nanoparticle-based modifications for gene delivery, as well as co-delivery of drugs and genes in cancer therapy with dendrimers, are presented. Finally, biosafety concerns and issues hindering the transition of dendrimers from research to the clinic are discussed to shed light on their clinical applications.

Unmodified and tyrosine-modified polyethylenimines as potential carriers for siRNA: Biophysical characterization and toxicity

Polyethylenimines (PEIs) are being explored as efficient non-viral nanocarriers for nucleic acid delivery in vitro and in vivo. To address limitations regarding PEI efficacy and biocompatibility, modifications of the chemical structure of linear and branched PEIs have been introduced, including grafting with tyrosine. The aim has been to compare linear and branched polyethylenimines of a wider range of different molecular mass with their tyrosine-modified derivatives. To do so, physico-chemical and biological properties of the polymers were investigated. Even in the absence of a negatively charged nucleic acid counterpart, PEIs form particle structures with defined size and surface potential. Tyrosine modification of PEI led to significantly reduced toxicity, while simultaneously increasing interaction with cellular membranes. All the effects were also dependent on the PEI molecular weight and structure (i.e., linear vs. branched). Especially in the case of linear PEIs, the improved membrane interaction also translated into slightly enhanced hemolysis, whereas their genotoxic potential was essentially abolished. Due to the improvement of properties critical for nano-vector efficacy and biocompatibility, our data demonstrate that tyrosine-modified PEIs are very promising and safe nanocarriers for the delivery of small RNAs, like siRNAs and miRNAs.

A core-shell nanoplatform as a nonviral vector for targeted delivery of genes to the retina

Retinal diseases, including age-related macular degeneration (AMD), are a major cause of blindness. Efficient delivery of therapeutic genes to retinal cells to treat retinal disease is a formidable challenge. In this study, we developed a core-shell nanoplatform composed of a core and two external layers for targeted delivery of the gene to the retina. The inner core was composed of amino acid-functionalized dendrimers and a nuclear localization signal (NLS) for DNA complexation, nuclear transport and efficient transfection. The inner core was coated in a lipid bilayer that comprised pH-sensitive lipids as the inner shell layer. Hyaluronic acid (HA)-1,2-dioleoylphosphatidylethanolamine (DOPE) as the outermost shell layer was used for retinal cell targeting. This core-shell nanoplatform was developed so that the mobility in the vitreous body of these negatively charged carriers would not be affected by their surface charge, allowing diffusion into the retina, uptake into the retinal cells via CD44-mediated internalization, and finally transport into the nucleus by the NLS. The designed nanoparticles showed safety both in vitro and in vivo and inhibited the expression of VEGF under hypoxia-mimicking conditions. In vitro angiogenesis assays exhibited significant inhibitory effects on cell migration and tube formation. The in vivo assays indicated that this nanoplatform could be delivered to the retina. Taken together, this nanoplatform has the potential to transfer gene material into the retina for the treatment of retinal diseases, including AMD. STATEMENT OF SIGNIFICANCE: It remains a challenge to develop an efficient nonviral vector for gene therapy, especially retinal gene therapy. Various barriers exist in gene delivery and the unique ocular environment, making gene delivery to the retina difficult. In this study, we designed a negatively charged core-shell nanoplatform (HD-NP_PND) for the targeted delivery of gene to the retina. The developed nanoplatform possessed excellent transfection efficiency and safety both in vitro and in vivo. It efficiently delivered a gene to the retina. The results of this study suggested that this core-shell nanoplatform has the potential to deliver genes to the retina to treat retinal diseases, including age-related macular degeneration (AMD).

Considerable Improvement of Ursolic Acid Water Solubility by Its Encapsulation in Dendrimer Nanoparticles: Design, Synthesis and Physicochemical Characterization

Ursolic acid (UA) is a pentacyclic triterpenoid found in many medicinal plants and aromas endowed with numerous in vitro pharmacological activities, including antibacterial effects. Unfortunately, UA is poorly administered in vivo, due to its water insolubility, low bioavailability, and residual systemic toxicity, thus making urgent the development of water-soluble UA formulations. Dendrimers are nonpareil macromolecules possessing highly controlled size, shape, and architecture. In dendrimers with cationic surface, the contemporary presence of inner cavities and of hydrophilic peripheral functions, allows to encapsulate hydrophobic non-water-soluble drugs as UA, to enhance their water-solubility and stability, and to promote their protracted release, thus decreasing their systemic toxicity. In this paper, aiming at developing a new UA-based antibacterial agent administrable in vivo, we reported the physical entrapment of UA in a biodegradable not cytotoxic cationic dendrimer (G4K). UA-loaded dendrimer nanoparticles (UA-G4K) were obtained, which showed a drug loading (DL%) much higher than those previously reported, a protracted release profile governed by diffusion mechanisms, and no cytotoxicity. Also, UA-G4K was characterized by principal components analysis (PCA)-processed FTIR spectroscopy, by NMR and elemental analyses, and by dynamic light scattering experiments (DLS). The water solubility of UA-G4K was found to be 1868-fold times higher than that of pristine UA, thus making its clinical application feasible.

Preparation and in vitro characterization of histidine trimethyl chitosan conjugated nanocomplex incorporated into injectable thermosensitive hydrogels for localized gene delivery

Localized and sustained delivery of DNA using biomaterial scaffolds would increase the applicability of gene therapy in cancer treatment and tissue engineering. The most promising approach is the application of hydrogel scaffolds to encapsulate and deliver DNA in the form of nanocomplex to the target sites. In the present work, histidine conjugated trimethylated chitosan (HTMC) was synthesized and nanocomplexes fabricated with pDNA at different N/P ratios. The zeta potential and size of the HTMC/pDNA nanoparticles were determined using dynamic light scattering technique and the results were confirmed by scanning electron microscopy (SEM). The morphology of the nanoparticles was found spherical in shape having core-shell nanostructure. Based on gel retardation assay, polyplex dissociation following incubation with heparin, protection against DNase Ι, cytotoxicity and transfection experiments, HTMC/pDNA at N/P 15 was selected as an optimized formulation and loaded into CTS/PF127 and HA/PF127 hydrogel. The optimized HTMC/pDNA nanocomplex was homogenously distributed in the CTS/PF127 hydrogel. Transfection experiments were carried out on HEK293T cell lines and the results revealed that HTMC/pDNA complexes are stable and active inside the hydrogel, however, the transfection efficacy was decreased after incorporation into the hydrogel.

Nonviral gene delivery using PAMAM dendrimer conjugated with the nuclear localization signal peptide derived from human papillomavirus type 11 E2 protein

Polyamidoamine (PAMAM) dendrimers are biocompatible polymers utilized in multiple biomedical applications including tissue engineering, medical diagnosis, drug and gene delivery systems, and biosensors. Normally, high-generation PAMAM dendrimers are advantageous for use in gene therapy research because they have a relatively high transfection efficiency. A high-generation PAMAM dendrimer has a high charge density, which induces greater damage to the membranous organelles than that induced by a low-generation PAMAM dendrimer. In this study, we added NLS sequences derived from the human papillomavirus (HPV) type 11 E2 protein to the low-generation PAMAM generation 2 (PAMAM G2) dendrimer and simultaneously introduced histidine residues to reduce cytotoxicity. RKRARH-PAMAM G2 showed similar and high transfection efficiencies in Neuro-2A and NIH3T3 cell lines and relatively low cytotoxicities relative to that of polyethylenimine 25 kDa (PEI 25 kDa).

Overcoming the barriers to optimization of adenovirus delivery using biomaterials: Current status and future perspective

Adenovirus (Ad) is emerging as a promising modality for cancer gene therapy due to its ability to induce high level of therapeutic transgene expression with no risk of insertional mutagenesis, ability to be facilely produced at a high titer, and capacity to induce robust antitumor immune response. Despite these excellent attributes of human serotype 5 Ad, poor systemic administration capability, coxsackie and adenovirus receptor (CAR)-dependent endocytic mechanism limiting potentially targetable cell types, nonspecific shedding to normal organs, and poor viral persistence in tumor tissues are major hindrances toward maximizing the therapeutic benefit of Ad in clinical setting. To address the abovementioned shortcomings, various non-immunogenic nanomaterials have been explored to modify Ad surface via physical or chemical interactions. In this review, we summarize the recent developments of different types of nanomaterials that had been utilized for modification of Ad and how tumor-targeted local and system delivery can be achieved with these nanocomplexes. Finally, we conclude by highlighting the key features of various nanomaterials-coated Ads and their prospects to optimize the delivery of virus.

Fluoropolymers in biomedical applications: state-of-the-art and future perspectives

Biomedical applications of fluoropolymers in gene delivery, protein delivery, drug delivery, ¹⁹F MRI, PDT, anti-fouling, anti-bacterial, cell culture, and tissue engineering.

Location of a single histidine within peptide carriers increases mRNA delivery

BACKGROUND

Previously, we determined that four-branched histidine-lysine (HK) peptides were effective carriers of plasmids and small interfering RNA. In the present study, we compared several branched HK carriers and, in particular, two closely-related H3K4b and H3K(+H)4b peptides for their ability as carriers of mRNA. The H3K(+H)4b peptide differed from its parent analogue, H3K4b, by only a single histidine in each branch.

METHODS

A series of four-branched HK peptides with varied sequences was synthesized on a solid-phase peptide synthesizer. The ability of these peptides to carry mRNA expressing luciferase to MDA-MB-231 cells was investigated. With gel retardation and heparin displacement assays, the stability of HK polyplexes was examined. We determined the intracellular uptake of HK polyplexes by flow cytometry and fluorescence microscopy. The size and polydispersity index of the polyplexes in several media were measured by dynamic light scattering.

RESULTS

MDA-MB-231 cells transfected by H3K(+H)4b-mRNA polyplexes expressed 10-fold greater levels of luciferase than H3K4b polyplexes. With gel retardation and heparin displacement assays, the H3K(+H)4b polyplexes showed greater stability than H3K4b. Intracellular uptake and co-localization of H3K(+H)4b polyplexes within acidic endosomes were also significantly increased compared to H3K4b. Similar to H3K(+H)4b, several HK analogues with an additional histidine in the second domain of their branches were effective carriers of mRNA. When combined with DOTAP liposomes, H3K(+H)4b was synergistic in delivery of mRNA.

CONCLUSIONS

H3K(+H)4b was a more effective carrier of mRNA than H3K4b. Mechanistic studies suggest that H3K(+H)4b polyplexes were more stable than H3K4b polyplexes. Lipopolyplexes formed with H3K(+H)4b markedly increased mRNA transfection.

Biodegradable and biocompatible spherical dendrimer nanoparticles with a gallic acid shell and a double-acting strong antioxidant activity as potential device to fight diseases from "oxidative stress"

Gallic acid (GA) is a natural polyphenol with remarkable antioxidant power present in several vegetables and fruits. A normal feeding regime leads to a daily intake of GA which is reasonably regarded as "natural" and "safe" for humans. It owns strong potentials as alternative to traditional drugs to treat several diseases triggered by oxidative stress (OS), but poor gastrointestinal absorbability, pharmacokinetic drawbacks, and fast metabolism limit its clinical application. In this work, a fifth-generation polyester-based dendrimer was firstly prepared as a better absorbable carrier to protect and deliver GA. Then, by its peripheral esterification with GA units, a GA-enriched delivering system (GAD) with remarkable antioxidant power and high potential against diseases from OS was achieved. Scanning electron microscopy results and dynamic light scattering analysis revealed particles with an average size around 387 and 375 nm, respectively, and an extraordinarily spherical morphology. These properties, by determining a large particles surface area, typically favour higher systemic residence time and bio-efficiency. Z-potential of - 25 mV suggests satisfactory stability in solution with tendency to form megamers and low polydispersity index. GAD showed intrinsic antioxidant power, higher than GA by 4 times and like prodrugs, and it can carry contemporary several bioactive GA units versus cells. In physiological condition, the action of pig liver esterase (PLE), selected as a model of cells esterase, hydrolyses GAD to non-cytotoxic small molecules, thus setting free the bioactive GA units, for further antioxidant effects. Cytotoxicity studies performed on two cell lines demonstrated a high cell viability. Graphical Abstract Graphical Abstract.

Targeting nanoparticles for diagnosis and therapy of bone tumors: Opportunities and challenges

A variety of targeted nanoparticles were developed for the diagnosis and therapy of orthotopic and metastatic bone tumors during the past decade. This critical review will focus on principles and methods in the design of these bone-targeted nanoparticles. Ligands including bisphosphonates, aspartic acid-rich peptides and synthetic polymers were grafted on nanoparticles such as PLGA nanoparticles, liposomes, dendrimers and inorganic nanoparticles for bone targeting. Besides, other ligands such as monoclonal antibodies, peptides and aptamers targeting biomarkers on tumor/bone cells were identified for targeted diagnosis and therapy. Examples of targeted nanoparticles for the early detection of bone metastatic tumors and the ablation of cancer via chemotherapy, photothermal therapy, gene therapy and combination therapy will be intensively reviewed. The development of multifunctional nanoparticles to break down the "vicious" cycle between tumor cell proliferation and bone resorption, and the challenges and perspectives in this area will be discussed.

Protein Expression Knockdown in Cancer Cells Induced by a Gemini Cationic Lipid Nanovector with Histidine-Based Polar Heads

A histidine-based gemini cationic lipid, which had already demonstrated its efficiency as a plasmid DNA (pDNA) nanocarrier, has been used in this work to transfect a small interfering RNA (siRNA) into cancer cells. In combination with the helper lipid monoolein glycerol (MOG), the cationic lipid was used as an antiGFP-siRNA nanovector in a multidisciplinary study. Initially, a biophysical characterization by zeta potential (ζ) and agarose gel electrophoresis experiments was performed to determine the lipid effective charge and confirm siRNA compaction. The lipoplexes formed were arranged in Lα lamellar lyotropic liquid crystal phases with a cluster-type morphology, as cryo-transmission electron microscopy (cryo-TEM) and small-angle X-ray scattering (SAXS) studies revealed. Additionally, in vitro experiments confirmed the high gene knockdown efficiency of the lipid-based nanovehicle as detected by flow cytometry (FC) and epifluorescence microscopy, even better than that of Lipofectamine2000*, the transfecting reagent commonly used as a positive control. Cytotoxicity assays indicated that the nanovector is non-toxic to cells. Finally, using nano-liquid chromatography tandem mass spectrometry (nanoLC-MS/MS), apolipoprotein A-I and A-II followed by serum albumin were identified as the proteins with higher affinity for the surface of the lipoplexes. This fact could be beyond the remarkable silencing activity of the histidine-based lipid nanocarrier herein presented.

Nuclear-Targeting Delivery of CRISPRa System for Upregulation of β-Defensin against Virus Infection by Dexamethasone and Phenylalanine Dual-Modified Dendrimer

The dual-modified dendrimer containing dexamethasone (DET) and phenylalanine (Phe) was prepared to deliver plasmid DNA encoding dCas9 and single-guide RNA (sgRNA) for specific upregulation of β-defensin. DET and Phe moieties synergistically enhanced the transfection efficiency and reduced cytotoxicity of dendrimers. Combination of three sgRNAs targeting β-defensin gene demonstrated higher activation efficacy of β-defensin than any single sgRNA and combinations of any two sgRNAs, showing an efficient inhibition of virus infection and replication. The titer of vesicular stomatitis virus (VSV) in the cells treated with dCas9-sgRNA targeting β-defensin was reduced by about 100-fold compared to that of cells treated with dCas9-scramble sgRNA (dCas9-scr sgRNA). In vivo experiments demonstrated that the DET- and Phe-modified dendrimer effectively delivered plasmid DNA encoding dCas9 protein into the airway epithelium, inducing β-defensin expression. Delivery of the CRISPR activation system by a dendrimer modified with DET and Phe was a promising approach against viral disease.

Dendrimers as efficient nanocarriers for the protection and delivery of bioactive phytochemicals

The genesis of dendrimers can be considered as a revolution in nano-scaled bioactive delivery systems. These structures possess a unique potential in encapsulating/entrapping bioactive ingredients due to their tree-like nature. Therefore, they could swiftly obtain a valuable statue in nutraceutical, pharmaceutical and medical sciences. Phytochemicals, as a large proportion of bioactives, have been studied and used by scholars in several fields of pharmacology, medical, food, and cosmetic for many years. But, the solubility, stability, and bioavailability issues have always been recognized as limiting factors in their application. Therefore, the main aim of this study is representing the use of dendrimers as novel nanocarriers for phytochemical bioactive compounds to deal with these problems. Hence, after a brief review of phytochemical ingredients, the text is commenced with a detailed explanation of dendrimers, including definitions, types, generations, synthesizing methods, and safety issues; then is continued with demonstration of their applications in encapsulation of phytochemical bioactive compounds and their active/passive delivery by dendrimers. Dendrimers provide a vast and appropriate surface to entrap the targeted phytochemical bioactive ingredients. Several parameters can affect the yield of nanoencapsulation by dendrimers, including their generation, type of end groups, surface charge, core structure, pH, and ambient factors. Another important issue of dendrimers is related to their toxicity. Cationic dendrimers, particularly PAMAM can be toxic to body cells through attaching to the cell membranes and disturbing their functions. However, a number of solutions have been suggested to decrease their toxicity.

Effective Cellular Delivery of Antisense Peptide Nucleic Acid by Conjugation to Guanidinylated Diaminobutanoic Acid-Based Peptide Dendrons

A series of amino- and guanidino-terminating 3- and 4-generation 2,4-diaminobutanoic acid (Dab) dendrons have been robustly synthesized on a solid phase and characterized as cellular delivery agents in antisense peptide nucleic acid (PNA) conjugates in the pLuc705 HeLa cell splice switching system. The dendron-PNA conjugates exhibited splice correction activity at one digit micromolar concentrations, and guanidino-terminating dendrons were significantly more effective than analogous amine terminating ones. Furthermore, introduction of lipophilic groups such as phenyl, alkyl, or fatty acids increased efficacy, but also increased cellular toxicity. Fluorescence microscopy analyses supported an endosomal uptake mechanism and furthermore predominantly showed colocalization with late endosomes and lysosomes. The robust solid phase synthesis should make such Dab-dendrons a useful platform for further in vitro as well as in vivo optimization.

Polymeric Nanoparticles Based on Tyrosine-Modified, Low Molecular Weight Polyethylenimines for siRNA Delivery

A major hurdle for exploring RNA interference (RNAi) in a therapeutic setting is still the issue of in vivo delivery of small RNA molecules (siRNAs). The chemical modification of polyethylenimines (PEIs) offers a particularly attractive avenue towards the development of more efficient non-viral delivery systems. Here, we explore tyrosine-modified polyethylenimines with low or very low molecular weight (P2Y, P5Y, P10Y) for siRNA delivery. In comparison to their respective parent PEI, they reveal considerably increased knockdown efficacies and very low cytotoxicity upon tyrosine modification, as determined in different reporter and wildtype cell lines. The delivery of siRNAs targeting the anti-apoptotic oncogene survivin or the serine/threonine-protein kinase PLK1 (polo-like kinase 1; PLK-1) oncogene reveals strong inhibitory effects in vitro. In a therapeutic in vivo setting, profound anti-tumor effects in a prostate carcinoma xenograft mouse model are observed upon systemic application of complexes for survivin or PLK1 knockdown, in the absence of in vivo toxicity. We thus demonstrate the tyrosine-modification of (very) low molecular weight PEIs for generating efficient nanocarriers for siRNA delivery in vitro and in vivo, present data on their physicochemical and biological properties, and show their efficacy as siRNA therapeutic in vivo, in the absence of adverse effects.

Cocktail Strategy Based on NK Cell-Derived Exosomes and Their Biomimetic Nanoparticles for Dual Tumor Therapy

Successful cancer therapy requires drugs being precisely delivered to tumors. Nanosized drugs have attracted considerable recent attention, but their toxicity and high immunogenicity are important obstacles hampering their clinical translation. Here we report a novel “cocktail therapy” strategy based on excess natural killer cell-derived exosomes (NKEXOs) in combination with their biomimetic core–shell nanoparticles (NNs) for tumor-targeted therapy. The NNs were self- assembled with a dendrimer core loading therapeutic miRNA and a hydrophilic NKEXOs shell. Their successful fabrication was confirmed by transmission electron microscopy (TEM) and confocal laser scanning microscopy (CLSM). The resulting NN/NKEXO cocktail showed highly efficient targeting and therapeutic miRNA delivery to neuroblastoma cells in vivo, as demonstrated by two-photon excited scanning fluorescence imaging (TPEFI) and with an IVIS Spectrum in vivo imaging system (IVIS), leading to dual inhibition of tumor growth. With unique biocompatibility, we propose this NN/NKEXO cocktail as a new avenue for tumor therapy, with potential prospects for clinical applications.

Structure-activity relationship of novel low-generation dendrimers for gene delivery

Structure-activity relationship (SAR) studies are very critical to design ideal gene vectors for gene delivery. However, It is difficult to obtain SAR information of low-generation dendrimers due to the lack of easy structural modification ways. Here, we synthesized a novel family of rigid aromatic backbone-based low-generation polyamidoamine (PAMAM) dendrimers. According to the number of primary amines, they were divided into two types: four-amine-containing PAMAM (DL1-DL5) and eight-amine-containing PAMAM (DL6-DL10). Due to the introduction of a rigid aromatic backbone, the low-generation PAMAM could be modified easier by different hydrophobic aliphatic chains. Several assays were used to study the interactions of the PAMAM dendrimers with plasmid DNA, and the results revealed that they not only had good DNA binding ability but also could efficiently condense DNA into spherical-shaped nanoparticles with suitable sizes and zeta potentials. The SAR studies indicated that the gene-transfection efficiency of the synthesized materials depended on not only the structure of their hydrophobic chains but also the number of primary amines. It was found that four-amine-containing PAMAM prepared from oleylamine (DL5) gave the best transfection efficiency, which was 3 times higher than that of lipofectamine 2000 in HEK293 cells. The cellular uptake mechanism mediated by DL5 was further investigated, and the results indicated that DL5/DNA complexes entered the cells mainly via caveolae and clathrin-mediated endocytosis. In addition, these low-generation PAMAMs modified with a single hydrophobic tail showed lower toxicity than lipofectamine 2000 in MC3T3-E1, MG63, HeLa, and HEK293 cells. These results reveal that such a type of low-generation polyamidoamines might be promising non-viral gene vectors, and also give us clues for the design of safe and high-efficiency gene vectors.

Stable Deuterium Labeling of Histidine-Rich Lysine-Based Dendrimers

Peptide dendrimers, due to their biocompatibility and low toxicity, are highly promising candidates as nanocarriers for drugs and genes. The development of this kind of delivery system requires reliable monitoring of their metabolic and biological pathways. In this respect, hydrogen isotope labeling has tremendous importance, being a safe tool for detection of the labeled nanocarriers. In this work, we have synthesized new histidine-rich lysine-based dendrimers (Lys-2His dendrimer) with two linear histidine (His) residues in every inner segment. The presence of His residues has enabled us to perform controlled deuteration of Lys-2His dendrimers. The high deuteration degree (around 70%) does not practically change after redissolving the samples in H2O and heating them at 40 °C, which indicates the isotopic label stability.

Nanovaccine based on a protein-delivering dendrimer for effective antigen cross-presentation and cancer immunotherapy

Cancer vaccines for prevention and treatment of tumors have attracted tremendous interests as a type of cancer immunotherapy strategy. A major challenge in achieving robust T-cell responses to destruct tumor cells after vaccination is the abilities of antigen cross-presentation for antigen-presenting cells (APCs) such as dendritic cells (DCs). Herein, we demonstrate that a polyamidoamine dendrimer modified with guanidinobenzoic acid (DGBA) could serve as an effective protein carrier to enable delivery of protein antigen, thereby leading to effective antigen cross-presentation by DCs. With ovalbumin (OVA) as the model antigen and unmethylated cytosine-guanine dinucleotides (CpG) as the adjuvant, a unique type of tumor vaccine is formulated. Importantly, such DGBA-OVA-CpG nanovaccine can induce robust antigen-specific cellular immunities and further demonstrates outstanding prophylactic efficacy against B16-OVA melanoma. More significantly, the nanovaccine shows excellent therapeutic effect to treat established B16-OVA melanoma when used in combination with the programmed cell death protein 1 (PD-1) checkpoint-blockade immunotherapy. This study presents the great promises of employing rationally engineered cytosolic protein carriers for the development of tumor vaccines to achieve effective cancer immunotherapy.

Shedding light on gene therapy: Carbon dots for the minimally invasive image-guided delivery of plasmids and noncoding RNAs - A review

Recently, carbon dots (CDs) have attracted great attention due to their superior properties, such as biocompatibility, fluorescence, high quantum yield, and uniform distribution. These characteristics make CDs interesting for bioimaging, therapeutic delivery, optogenetics, and theranostics. Photoluminescence (PL) properties enable CDs to act as imaging-trackable gene nanocarriers, while cationic CDs with high transfection efficiency have been applied for plasmid DNA and siRNA delivery. In this review, we have highlighted the precursors, structure and properties of positively charged CDs to demonstrate the various applications of these materials for nucleic acid delivery. Additionally, the potential of CDs as trackable gene delivery systems has been discussed. Although there are several reports on cellular and animal approaches to investigating the potential clinical applications of these nanomaterials, further systematic multidisciplinary approaches are required to examine the pharmacokinetic and biodistribution patterns of CDs for potential clinical applications.

Preparation of ellagic acid micro and nano formulations with amazingly increased water solubility by its entrapment in pectin or non-PAMAM dendrimers suitable for clinical applications

Innovative antioxidant ellagic acid (EA) formulations suitable for oral and parenteral EA administration were achieved avoiding the use of harmful additives.

A Gemini Cationic Lipid with Histidine Residues as a Novel Lipid-Based Gene Nanocarrier: A Biophysical and Biochemical Study

This work reports the synthesis of a novel gemini cationic lipid that incorporates two histidine-type head groups (C₃(C16His)₂). Mixed with a helper lipid 1,2-dioleoyl-sn-glycero-3-phosphatidyl ethanol amine (DOPE), it was used to transfect three different types of plasmid DNA: one encoding the green fluorescence protein (pEGFP-C3), one encoding a luciferase (pCMV-Luc), and a therapeutic anti-tumoral agent encoding interleukin-12 (pCMV-IL12). Complementary biophysical experiments (zeta potential, gel electrophoresis, small-angle X-ray scattering (SAXS), and fluorescence anisotropy) and biological studies (FACS, luminometry, and cytotoxicity) of these C₃(C16His)₂/DOPE-pDNA lipoplexes provided vast insight into their outcomes as gene carriers. They were found to efficiently compact and protect pDNA against DNase I degradation by forming nanoaggregates of 120⁻290 nm in size, which were further characterized as very fluidic lamellar structures based in a sandwich-type phase, with alternating layers of mixed lipids and an aqueous monolayer where the pDNA and counterions are located. The optimum formulations of these nanoaggregates were able to transfect the pDNAs into COS-7 and HeLa cells with high cell viability, comparable or superior to that of the standard Lipo2000*. The vast amount of information collected from the in vitro studies points to this histidine-based lipid nanocarrier as a potentially interesting candidate for future in vivo studies investigating specific gene therapies.

Hydrophilic and amphiphilic water-soluble dendrimer prodrugs suitable for parenteral administration of a non-soluble non-nucleoside HIV-1 reverse transcriptase inhibitor thiocarbamate derivative

Drugs delivered by proper carriers enter into the cells much more rapidly and carry out their action much more promptly than in the free forms. A high drug concentration can be sustained for longer periods of time at the target site in the cell. In in vivo conditions, this would translate into a reduction of systemic toxicity, dosage and frequency of dosing. Dendritic polymers significantly affect drug delivery in terms of reaching the target site, modifying the bio-distribution of the drug, and enhancing the efficacy of different drugs including anticancer compounds. 2-({[2-({[(2-tolyl)amino]carbonothioyl}oxy)ethyl]amino}carbo-nyl)benzoic acid 1 is a thiocarbamate derivative belonging to an already reported class of non-nucleoside HIV-1 reverse transcriptase inhibitors. In in vitro assay it showed no cytotoxic effects but was endowed with very low solubility and poor activity against wild-type HIV-1 (EC₅₀ = 27 μM). With the aim at improving its water solubility, 1 has been successfully incorporated inside non-toxic amino acids-modified core-shell hetero dendrimers. IR, NMR, zeta potential, mean size of particles, buffer capacity and in vitro release profile of prepared materials were reported. All dendriplexes were evaluated in cell-based assays to assess their cytotoxic profile. The obtained complexes, which harmonize a peripheral polycationic character and a buffer capacity which presuppose efficient cells penetration and increased residence time with a not PAMAM structured biodegradable scaffold, were well water-soluble and could rationally appear as a promising set of prodrugs for safe in vivo administrations.

Surface functionalized dendrimers as controlled-release delivery nanosystems for tumor targeting

Dendrimers are nano-sized and three-dimensional macromolecules with well-defined globular architecture and are widely used in various aspects such as drug and gene delivery owing to multivalent and host-guest entrapment properties. However, dendrimers like other nanomaterials have some disadvantages for example rapid clearance by reticuloendothelial system, toxicity due to interaction of amine terminated group with cell membrane, low transfection efficiency and lack of controlled release behavior, which reduce their therapeutic efficiency. To solve these problems, surface functionalization of dendrimers can be carried out. Surface functionalization not only mitigates this obstacle but also renders excessive specificity to dendrimer to improve efficiency of cancer therapy. Specific properties in cancer cell compared to normal cells such as overexpression of various receptors and difference in biological condition like pH, temperature and redox of tumor environment can be an appropriate strategy to increase site-specific targeting efficiency. Therefore, in this article we focus on numerous functionalization strategies, which are used in the modification of dendrimers through attachment of lipid, amino acid, protein/peptide, aptamer, vitamin, antibody. Moreover, increased biocompatibility, site-specific delivery based on various ligands, enhanced transfection efficiency, sustained and controlled release behavior based on stimuli responsiveness are benefits of functionalized dendrimer which we discuss in this review. Overall, these functionalized dendrimers can open a new horizon in the field of targeted drug and gene delivery.

Inhibition of cell proliferation and migration through nucleobase-modified polyamidoamine-mediated p53 delivery

Introduction

The nucleobase 2-amino-6-chloropurine-modified polyamidoamine (AP-PAMAM) was used as a carrier for p53 gene delivery to achieve the antitumor effects.

Methods and materials

The condensation of p53 plasmid was studied through gel retardation assay, and the transfection efficiency was evaluated through the transfection assay of pEGFP-N3 and pGL-3 plasmids. Using human cervical carcinoma cell line HeLa as a model, the inhibition of cell proliferation and migration was studied through flow cytometry, wound healing and Transwell migration assays, respectively. The p53 expression level was detected through quantitative polymerase chain reaction and Western blotting analyses.

Results

The carrier could condense p53 plasmid into stable nanoparticles at N/P ratios of 2.0, and higher transfection efficiency than polyamidoamine (PAMAM) could be obtained at all the N/P ratios studied. AP-PAMAM-mediated p53 delivery could achieve stronger antiproliferative effect than PAMAM/p53. The antiproliferative effect was identified to be triggered by the induction of cell apoptosis (apoptotic ratio of 26.17%) and cell cycle arrest at S phase. Additionally, AP-PAMAM/p53 transfection has been found to suppress the cell migration and invasion of cancer cells. Finally, the enhanced p53 expression level could be detected after p53 transfection at mRNA and protein levels.

Conclusion

The PAMAM derivative-mediated p53 delivery could be a promising strategy for achieving tumor gene therapy.

Functionalized Asymmetric Bola-Type Amphiphiles for Efficient Gene and Drug Delivery

The studies of bolaamphiphile-based nanoparticles as delivery vectors are still rudimentary and under development. In this study, several asymmetric bolaamphiphiles containing lysine and another moiety with special functions, such as pH-sensitive or cell-targeting property, were designed and synthesized. The potentials of these bolaamphiphile-based nanoparticles as versatile vectors for both nucleic acids and chemical drugs were studied. With the presence of 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine (DOPE), these amphiphiles could be prepared into bolasomes, which showed good DNA binding ability and could condense plasmid DNA into nanoparticles with appropriate size and surface potential. Lys-His, which has a pH-sensitive histidine on one head, exhibited higher transfection efficiency than the symmetric counterpart and comparable efficiency to commercially available transfection reagent. Mechanism studies confirmed that the bolaplexes formed from Lys-His might induce the highest cellular uptake and the best endosomal escape ability. On the other hand, these bolaamphiphiles also exhibited good drug loading ability. The self-assembly vesicles could efficiently encapsulate the hydrophobic anti-cancer drug doxorubicin (DOX) in aqueous solution with high drug loading content and encapsulation efficiency. Confocal laser scanning microscopy (CLSM) experiment and cell viability assay exhibited a controlled release of the drug with the assistance of bolasomes. It was shown that such bolaamphiphiles have great potential as nano-vectors for both drug and gene or their co-delivery.

Statistical versus block fluoropolymers in gene delivery

A statistical fluorocopolymer shows dramatically higher transfection efficiency in gene delivery than a block one.

Versatile Supermolecular Inclusion Complex Based on Host-Guest Interaction for Targeted Gene Delivery

A facile and targeted gene delivery system was prepared by conjugating β-cyclodextrin modified polyethylenimine (PEI-CD) and adamantyl peptide (AdGRGDS) based on host-guest interaction. With the rational design between PEI-CD and AdGRGDS, the PEI-CD/AdGRGDS gene delivery system showed excellent DNA binding capability and exhibited good ability to compact DNA into uniform spherical nanoparticles. In vitro luciferase assay showed that gene expression transfected by PEI-CD/AdGRGDS was stronger than that by PEI-CD in HeLa cells, whereas gene expression transfected by PEI-CD/AdGRGDS and PEI-CD was similar to each other in COS7 cells. Internalization of complexes was qualitatively studied using a confocal laser scanning microscope (CLSM) and quantitatively analyzed by flow cytometry, respectively, and targeting specificity was also evaluated by CLSM. Results of CLSM and flow cytometry indicated that PEI-CD/AdGRGDS had good targeting specificity to tumor cells with integrin αvβ3 overexpression. To further evaluate the targeting specificity and transfection efficiency in vivo, a rat model with murine hepatic carcinoma cell line H22 was used. PEI-CD/AdGRGDS showed stronger gene expression efficiency than PEI-CD via in vivo transfection of pORF-LacZ and pGL-3 plasmids after subcutaneous injection. Interestingly, PEI-CD/AdGRGDS also showed high targeting specificity and transfection distribution to tumor xenograft after tail-vein injection. In vitro and in vivo assays highlighted the importance of GRGDS targeting specificity to tumor cells with integrin αvβ3 overexpression and demonstrated that the PEI-CD/AdGRGDS gene delivery system would have great potential for targeted tumor therapy.

Chondroitin sulfate-functionalized polyamidoamine as a tumor-targeted carrier for miR-34a delivery

Chondroitin sulfate (CS) was modified on a polyamidoamine dendrimer (PAMAM) through Michael addition to construct a tumor-targeted carrier CS-PAMAM for miR-34a delivery. The derivative CS-PAMAM was demonstrated to achieve an efficient cellular uptake of miR-34a in a CD44-dependent endocytosis way and further facilitate the endosomal escape of miR-34a after 4h. Through the miR-34a delivery, obvious inhibition of cell proliferation could be detected which was attributed to the enhancement of cell apoptosis and cell cycle arrest, and meanwhile the cell migration and invasion has been observed to be inhibited. Finally, the intravenous injection of CS-PAMAM/miR-34a formulation into mice bearing human lung adenocarcinoma cell A549 xenografts could efficiently inhibit the tumor growth and induce the tumor apoptosis owing to the enhanced accumulation of miR-34a in tumor tissue. Overall, CS-PAMAM is potential to be used as a tumor-targeted oligonucleotide carrier for achieving tumor gene therapy.

STATEMENT OF SIGNIFICANCE

The cationic dendrimer PAMAM was modified by chondroitin sulfate (CS) through Michael addition to construct a tumor-targeted carrier CS-PAMAM for miR-34a delivery. The introduction of CS could achieve an efficient cellular uptake and intracellular transfection of miR-34a in a CD44-dependent endocytosis manner. The miR-34a delivery could execute the anti-proliferation activity by simultaneously inducing cell apoptosis and cell cycle arrest, and also the anti-migration activity. The CS-PAMAM-mediated systemic delivery of miR-34a showed significant inhibition of tumor growth and induction of tumor apoptosis using a mice model of subcutaneously implanted tumors.

Synthesis and evaluation of L-arabinose-based cationic glycolipids as effective vectors for pDNA and siRNA in vitro

Glycolipids might become a new type of promising non-viral gene delivery systems because of their low cytotoxicity, structural diversity, controllable aqua- and lipo-solubility, appropriate density and distribution of positive charges, high transfer efficiency and potential targeting function. In this study, four kinds of L-arabinose-based cationic glycolipids (Ara-DiC12MA, Ara-DiC14MA, Ara-DiC16MA and Ara-DiC18MA) containing quaternary ammonium as hydrophilic headgroup and two alkane chains as hydrophobic domain were synthesized and characterized. They were observed to have strong affinities for plasmid DNA (pDNA) and siRNA, the pDNA can be completely condensed at N/P ratio less than 2, and the siRNA can be completely retarded at N/P ratio less than 3. The dynamic light scattering (DLS) experiment and atomic force microscopy (AFM) experiment demonstrated that cationic lipids and their lipoplexes possessed suitable particle sizes with near-spherical shape and proper ζ-potentials for cell transfection. The Ara-DiC16MA liposome was found to have good transfection efficacy in HEK293, PC-3 and Mat cells compared with other three kinds of liposomes, and also maintain low cytotoxicity and better uptake capability in vitro. Furthermore, the gene silencing assay showed that Ara-DiC14MA and Ara-DiC16MA liposomes have demonstrated effective delivery and higher gene knockdown activity (>80%) in the above mentioned cells than Lipofectamine 2000. These results indicated Ara-DiC16MA can be developed for efficient and low toxic gene delivery.

Polymer-Nucleic Acid Interactions

Gene therapy is an important therapeutic strategy in the treatment of a wide range of genetic disorders. Polymers forming stable complexes with nucleic acids (NAs) are non-viral gene carriers. The self-assembly of polymers and nucleic acids is typically a complex process that involves many types of interaction at different scales. Electrostatic interaction, hydrophobic interaction, and hydrogen bonds are three important and prevalent interactions in the polymer/nucleic acid system. Electrostatic interactions and hydrogen bonds are the main driving forces for the condensation of nucleic acids, while hydrophobic interactions play a significant role in the cellular uptake and endosomal escape of polymer-nucleic acid complexes. To design high-efficiency polymer candidates for the DNA and siRNA delivery, it is necessary to have a detailed understanding of the interactions between them in solution. In this chapter, we survey the roles of the three important interactions between polymers and nucleic acids during the formation of polyplexes and summarize recent understandings of the linear polyelectrolyte-NA interactions and dendrimer-NA interactions. We also review recent progress optimizing the gene delivery system by tuning these interactions.