Association and dissociation characteristics of polymer/DNA complexes used for gene delivery

Spectroscopic characterization of the interactions between poly(2-(trimethylamino)ethyl methacrylate) chloride and the xanthene dyes, 2', 7'-difluorofluorescein and 2, 4, 5, 7-tetraiodofluorescein

Intermolecular interactions in buffered aqueous solution between the polycation, poly(2-(trimethylamino)ethyl methacrylate) chloride (pTMAEMC) and two anionic xanthene dyes, 2', 7'-difluorofluorescein (Oregon Green 488) and 2, 4, 5, 7-tetraiodofluorescein (Erythrosin B), are characterized using multiple optical spectroscopic methods. Visible absorption spectroscopy indicates the formation of ground-state pTMAEMC-dye complexes. Benesi-Hildebrand binding isotherm analysis of visible absorption spectra for pTMAEMC-dye mixtures quantifies the strength of binding interactions producing the complexes. For both Oregon Green 488 (OG) and Erythrosin B (EB) in mixtures with pTMAEMC, the concentration of the solution's sodium acetate buffer at a fixed pH alters the binding constants, K_b, suggesting that ionic strength plays a key role in determining the binding affinity of pTMAEMC for the dyes. Comparison of K_b, for the dyes indicates stronger binding of EB under all solution conditions. Steady-state fluorescence emission spectroscopy, fluorescence quenching, excited-state fluorescence lifetime measurements and fluorescence correlation spectroscopy provide complementary data for the interactions between pTMAEMC and the dyes. Mixtures of pTMAEMC with the dyes produce fluorescence enhancements and fluorescence quenching which exhibit a dependence on the buffer concentration used in the mixture. Excited-state lifetime analysis indicates that OG interacts with pTMAEMC through ground-state interactions while EB exhibits both ground-state and excited-state interactions with pTMAEMC. The spectroscopic measurements suggest that a polyelectrolyte effect for pTMAEMC due to ionic strength variation produced by the buffer concentration affects the dye binding profile of the polycation. This conclusion is supported by fluorescence correlation spectroscopy (FCS) analyses of the hydrodynamic diameter changes in pTMAEMC-OG binding in low buffer concentration (low ionic strength) solution. FCS analyses of pTMAEMC-OG mixtures also reveal diversity in the complexes formed in low ionic strength solution suggesting that other xanthene dyes will exhibit similar binding behaviors in mixtures with pTMAEMC as a function of solution ionic strength.

Development of a cancer cells self‑activating and miR‑125a‑5p expressing poly‑pharmacological nanodrug for cancer treatment

Cancer cells can acquire resistance to targeted therapeutic agents when the designated targets or their downstream signaling molecules develop protein conformational or activity changes. There is an increasing interest in developing poly-pharmacologic anticancer agents to target multiple oncoproteins or signaling pathways in cancer cells. The microRNA 125a-5p (miR-125a-5p) is a tumor suppressor, and its expression has frequently been downregulated in tumors. By contrast, the anti-apoptotic molecule BIRC5/SURVIVIN is highly expressed in tumors but not in the differentiated normal tissues. In the present study, the development of a BIRC5 gene promoter-driven, miR-125a-5p expressing, poly-L-lysine-conjugated magnetite iron poly-pharmacologic nanodrug (pL-MNP-pSur-125a) was reported. The cancer cells self-activating property and the anticancer effects of this nanodrug were examined in both the multidrug efflux protein ABCB1/MDR1-expressing/-non-expressing cancer cells in vitro and in vivo. It was demonstrated that pL-MNP-pSur-125a decreased the expression of ERBB2/HER2, HDAC5, BIRC5, and SP1, which are hot therapeutic targets for cancer in vitro. Notably, pL-MNP-pSur-125a also downregulated the expression of TDO2 in the human KB cervical carcinoma cells. PL-MNP-pSur-125a decreased the viability of various BIRC5-expressing cancer cells, regardless of the tissue origin or the expression of ABCB1, but not of the human BIRC5-non-expressing HMEC-1 endothelial cells. In vivo, pL-MNP-pSur-125a exhibited potent antitumor growth effects, but without inducing liver toxicity, in various zebrafish human-ABCB1-expressing and ABCB1-non-expressing tumor xenograft models. In conclusion, pL-MNP-pSur-125a is an easy-to-prepare and a promising poly-pharmacological anticancer nanodrug that has the potential to manage numerous malignancies, particularly for patients with BIRC5/ABCB1-related drug resistance after prolonged chemotherapeutic treatments.

Ultrasound-Enhanced Reactive Oxygen Species Responsive Charge-Reversal Polymeric Nanocarriers for Efficient Pancreatic Cancer Gene Delivery

Inefficient intracellular gene release and transfection limit nonviral gene delivery applications in cancer therapy. Reactive oxygen species (ROS) responsive nonviral gene delivery is the most widely explored strategy for such applications, yet the development of fast and safe ROS responsive nanocarriers proves to be a challenge because of the intracellular chemical equilibrium of high ROS and glutathione levels. Here, we report an ultrasound-enhanced ROS responsive charge-reversal polymeric nanocarrier (BTIL) for fast and efficient pancreatic cancer gene delivery. The BTIL is composed of B-PDEAEA/DNA polyplex-based cores and IR780-loaded liposome coatings. The IR780 is able to produce an excess of ROS under low intensity ultrasound irradiation, thus disequilibrating the chemical equilibrium of ROS and glutathione, and promoting the ROS-responsive positive-to-negative charge-reversal of the B-PDEAEA polymer. This charge conversion results in fast polyplex dissociation and intracellular gene release, inducing efficient gene transfection and cancer cell apoptosis. Moreover, following the intravenous administration, BTIL maintains a stable and long circulation in the bloodstream, achieves orthotopic pancreatic ductal adenocarcinoma distribution, and exhibits potent antitumor activity with negligible side effects. Our results reveal the proposed strategy to be both promising and universal for the development of fast and safe ROS responsive nonviral gene delivery in cancer therapy.

Polymeric Delivery of Therapeutic Nucleic Acids

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

A novel method for DNA delivery into bacteria using cationic copolymers

Amphiphilic copolymers have a wide variety of medical and biotechnological applications, including DNA transfection in eukaryotic cells. Still, no polymer-primed transfection of prokaryotic cells has been described. The reversible addition-fragmentation chain transfer (RAFT) polymer synthesis technique and the reversible deactivation radical polymerization variants allow the design of polymers with well-controlled molar mass, morphology, and hydrophilicity/hydrophobicity ratios. RAFT was used to synthesize two amphiphilic copolymers containing different ratios of the amphiphilic poly[2-(dimethyl-amino) ethyl methacrylate] and the hydrophobic poly [methyl methacrylate]. These copolymers bound to pUC-19 DNA and successfully transfected non-competent Escherichia coli DH5α, with transformation efficiency in the range of 103 colony-forming units per µg of plasmid DNA. These results demonstrate prokaryote transformation using polymers with controlled amphiphilic/hydrophobic ratios.

Polymeric delivery systems for nucleic acid therapeutics: Approaching the clinic

Gene therapy using nucleic acids has many clinical applications for the treatment of diseases with a genetic origin as well as for the development of innovative vaccine formulations. Since nucleic acids in their free form are rapidly degraded by nucleases present in extracellular matrices, have poor pharmacokinetics and hardly pass cellular membranes, carrier systems are required. Suitable carriers that protect the nucleic acid payload against enzymatic attack, prolong circulation time after systemic administration and assist in cellular binding and internalization are needed to develop nucleic acid based drug products. Viral vectors have been investigated and are also clinically used as delivery vehicles. However, some major drawbacks are associated with their use. Therefore there has been substantial attention on the use of non-viral carrier systems based on cationic lipids and polymers. This review focuses on the properties of polymer-based nucleic acid formulations, also referred as polyplexes. Different polymeric systems are summarized, and the cellular barriers polyplexes encounter and ways to tackle these are discussed. Finally attention is given to the clinical status of non-viral nucleic acid formulations.

Effects of Decomplexation Rates on Ternary Gene Complex Transfection with α-Poly(l-Lysine) or ε-Poly(l-Lysine) as a Decomplexation Controller in An Easy-To-Transfect Cell or A Hard-To-Transfect Cell

The tight binding of pDNA with a cationic polymer is the crucial requirement that prevents DNA degradation from undesired DNase attack to safely deliver the pDNA to its target site. However, cationic polymer-mediated strong gene holding limits pDNA dissociation from the gene complex, resulting in a reduction in transfection efficiency. In this study, to control the decomplexation rate of pDNA from the gene complex in a hard-to-transfect cell or an easy-to-transfect cell, either α-poly(l-lysine) (APL) or ε-poly(l-lysine) (EPL) was incorporated into branched polyethylenimine (bPEI)-based nanocomplexes (NCs). Compared to bPEI/pDNA NCs, the addition of APL or EPL formed smaller bPEI-APL/pDNA NCs with similar zeta potentials or larger bPEI-EPL/pDNA NCs with reduced zeta potentials, respectively, due to the different characteristics of the primary amines in the two poly(l-lysine)s (PLs). Interestingly, although both bPEI-APL/pDNA NCs and bPEI-EPL/pDNA NCs showed similar pDNA compactness to bPEI/pDNA NCs, the addition of APL or EPL resulted in slower or faster pDNA release, respectively, from the bPEI-PL/pDNA NCs than from the bPEI/pDNA NCs. bPEI-EPL/pDNA NCs with a decomplexation enhancer (i.e., EPL) improved the transfection efficiency (TE) in both a hard-to-transfect HepG2 cell and an easy-to-transfect HEK293 cell. However, although a decomplexation inhibitor (i.e., APL) reduced the TE of bPEI-APL/pDNA NCs in both cells, the degree of reduction in the TE could be compensated by PL-mediated enhanced nuclear delivery, particularly in HepG2 cells but not HEK293 cells, because both PLs facilitate nuclear localization of the gene complex per its cellular uptake. In conclusion, a decomplexation rate controller could be a potential factor to establish a high TE and design clinically available gene complex systems.

Tuning of endosomal escape and gene expression by functional groups, molecular weight and transfection medium: a structure-activity relationship study

The use of genetic material by non-viral transfer systems is still in its initial stages, but there are high expectations for the development of targeted therapies. However, nucleic acids cannot enter cells without help, they must be well protected to prevent degradation and overcome a variety of biological barriers, the endosomal barrier being one of the greatest cellular challenges. Herein, the structure-property-relationship was investigated in detail, using well-defined polymers. Polyacrylamides were synthesized via RAFT polymerization resulting in a polymer library of (i) different cationic groups as aminoethyl acrylamide (AEAm), dimethylaminoethyl acrylamide (DMAEAm), dimethylaminopropyl acrylamide (DMAPAm) and guanidinopropyl acrylamide (GPAm); (ii) different degree of polymerization; and investigated (iii) in different cell culture settings. The influence of molar mass and cationic moiety on complex formation with pDNA, cytotoxicity and transfection efficiency of the polymers were investigated. The systematic approach identified a pH-independent guanidinium-containing homopolymer (PGPAm₈₉) as the polymer with the highest transfection efficiency and superior endosomal release under optimal conditions. Since PGPAm₈₉ is not further protonated inside endosomes, common escape theories appear unsuitable. Therefore, the interaction with bis(monoacryloylglycerol)phosphate, a lipid specific for endosomal vesicles, was investigated. Our research suggests that the interactions between amines and lipids may be more relevant than anticipated.

Structure and Dynamics of Thermosensitive pDNA Polyplexes Studied by Time-Resolved Fluorescence Spectroscopy

Combining multiple stimuli-responsive functionalities into the polymer design is an attractive approach to improve nucleic acid delivery. However, more in-depth fundamental understanding how the multiple functionalities in the polymer structures are influencing polyplex formation and stability is essential for the rational development of such delivery systems. Therefore, in this study the structure and dynamics of thermosensitive polyplexes were investigated by tracking the behavior of labeled plasmid DNA (pDNA) and polymer with time-resolved fluorescence spectroscopy using fluorescence resonance energy transfer (FRET). The successful synthesis of a heterofunctional poly(ethylene glycol) (PEG) macroinitiator containing both an atom transfer radical polymerization (ATRP) and reversible addition-fragmentation chain-transfer (RAFT) initiator is reported. The use of this novel PEG macroinitiator allows for the controlled polymerization of cationic and thermosensitive linear triblock copolymers and labeling of the chain-end with a fluorescent dye by maleimide-thiol chemistry. The polymers consisted of a thermosensitive poly(N-isopropylacrylamide) (PNIPAM, N), hydrophilic PEG (P), and cationic poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA, D) block, further referred to as NPD. Polymer block D chain-ends were labeled with Cy3, while pDNA was labeled with FITC. The thermosensitive NPD polymers were used to prepare pDNA polyplexes, and the effect of the N/P charge ratio, temperature, and composition of the triblock copolymer on the polyplex properties were investigated, taking nonthermosensitive PD polymers as the control. FRET was observed both at 4 and 37 °C, indicating that the introduction of the thermosensitive PNIPAM block did not compromise the polyplex structure even above the polymer's cloud point. Furthermore, FRET results showed that the NPD- and PD-based polyplexes have a less dense core compared to polyplexes based on cationic homopolymers (such as PEI) as reported before. The polyplexes showed to have a dynamic character meaning that the polymer chains can exchange between the polyplex core and shell. Mobility of the polymers allow their uniform redistribution within the polyplex and this feature has been reported to be favorable in the context of pDNA release and subsequent improved transfection efficiency, compared to nondynamic formulations.

Precisely targeted gene delivery in human skin using supramolecular cationic glycopolymers

Gene delivery has become the focus of clinical treatments, thus motivating delivery strategies that are capable of targeting certain cell types in the context of both vaccines and therapeutics.

Enhancing the In Vitro and In Vivo Stabilities of Polymeric Nucleic Acid Delivery Nanosystems

Gene therapy holds great promise for various medical and biomedical applications. Nonviral gene delivery systems formed by cationic polymer and nucleic acids (e.g., polyplexes) have been extensively investigated for targeted gene therapy; however, their in vitro and in vivo stability is affected by both their intrinsic properties such as chemical compositions (e.g., polymer molecular weight and structure, and N/P ratio) and a number of environmental factors (e.g., shear stress during circulation in the bloodstream, interaction with the serum proteins, and physiological ionic strength). In this review, we surveyed the effects of a number of important intrinsic and environmental factors on the stability of polymeric gene delivery systems, and discussed various strategies to enhance the stability of polymeric gene delivery systems, thereby enabling efficient gene delivery into target cells. Future opportunities and challenges of polymeric nucleic acid delivery nanosystems were also briefly discussed.

Insights on the intracellular trafficking of PDMAEMA gene therapy vectors

It is known that an efficient gene therapy vector must overcome several steps to be able to express the gene of interest: (I) enter the cell by crossing the cell membrane; (II) escape the endo-lysosomal degradation pathway; (III) release the genetic material; (IV) traffic through the cytoplasm and enter the nucleus; and last (V), enable gene expression to synthetize the protein of interest. In recent years, we and others have demonstrated the potential of poly(2‑(N,N'‑dimethylamino)ethylmethacrylate) (PDMAEMA) as a gene therapy vehicle. Further optimization of gene transfer efficiency requires the understanding of the intracellular pathway of PDMAEMA. Therefore the goal of this study was to determine the cellular entry and intracellular trafficking mechanisms of our PDMAEMA vectors and determine the gene transfer bottleneck. For this, we have produced rhodamine-labeled PDMAEMA polyplexes that were used to transfect retinal cells and the cellular localization determined by co-localization with cellular markers. Our vectors quickly and efficiently cross the cell membrane, and escape the endo-lysosomal system by 24 h. We have observed the PDMAEMA vectors to concentrate around the nucleus, and the DNA load to be released in the first 24 h after transfection. These results allow us to conclude that although the endo-lysosomal system is an important obstacle, PDMAEMA gene vectors can overcome it. The nuclear membrane, however, constitutes the bottleneck to PDMAEMA gene transfer ability.

Self-assembling HA/PEI/dsRNA-p21 ternary complexes for CD44 mediated small active RNA delivery to colorectal cancer

Our previous work proved that sequence specific double strand RNA (dsRNA-p21) effectively activated p21 gene expression of colorectal cancer (CRC) cells and consequently suppressed CRC growth. However, efficient delivery system is a significant challenge to achieve sufficient therapy. In this study, a self-assembled HA/PEI/dsRNA-p21 ternary complex (TC-dsRNA-p21) was developed for the tumor-target delivery of dsRNA-p21 into CRC cells. Hyaluronic acid (HA) was introduced to shield the PEI/dsRNA-p21 binary complexes (BC-dsRNA-p21) for reducing the cytotoxicity of PEI and for increasing the tumor-targeted intracellular uptake by cancer cells through HA-CD44 mediated endocytosis. Comparing to the BC-dsRNA-p21, the TC-dsRNA-p21 showed increase in size, decrease in zeta potential, low cytotoxicity as well as high stability in physiological conditions due to the anionic shielding. Confocal microscopy analysis and flow cytometry confirmed that TC-dsRNA-p21 had high transfection efficiency in the CD44-abundant Lovo cells, as compared with binary complex. In vitro physiological experiment showed that, comparing to the control group, the TC-dsRNA-p21 effectively activated the expression of p21 mRNA and P21 protein, causing blockage of cell cycle at G0/G1 phase and suppression of cancer cell proliferation as well as colony formation. Furthermore, in vivo distribution experiment demonstrated that the TC-dsRNA-p21 could effectively accumulate at rectal wall for up to 10 h, following in situ application. These findings indicated that TC-dsRNA-p21 might hold great potential for delivering dsRNA-p21 to treat CRC.

Rational Design of Cancer Nanomedicine: Nanoproperty Integration and Synchronization

Current cancer nanomedicines can only mitigate adverse effects but fail to enhance therapeutic efficacies of anticancer drugs. Rational design of next-generation cancer nanomedicines should aim to enhance their therapeutic efficacies. Taking this into account, this review first analyzes the typical cancer-drug-delivery process of an intravenously administered nanomedicine and concludes that the delivery involves a five-step CAPIR cascade and that high efficiency at every step is critical to guarantee high overall therapeutic efficiency. Further analysis shows that the nanoproperties needed in each step for a nanomedicine to maximize its efficiency are different and even opposing in different steps, particularly what the authors call the PEG, surface-charge, size and stability dilemmas. To resolve those dilemmas in order to integrate all needed nanoproperties into one nanomedicine, stability, surface and size nanoproperty transitions (3S transitions for short) are proposed and the reported strategies to realize these transitions are comprehensively summarized. Examples of nanomedicines capable of the 3S transitions are discussed, as are future research directions to design high-performance cancer nanomedicines and their clinical translations.

Fusogenic Reactive Oxygen Species Triggered Charge-Reversal Vector for Effective Gene Delivery

A novel fusogenic lipidic polyplex (FLPP) vector is designed to fuse with cell membranes, mimicking viropexis, and eject the polyplex into the cytosol, where the cationic polymer is subsequently oxidized by intracellular reactive oxygen species and converts to being negatively charged, efficiently releasing the DNA. The vector delivering suicide gene achieves significantly better inhibition of tumor growth than doxorubicin.

Hydrolytic charge-reversal of PEGylated polyplexes enhances intracellular un-packaging and activity of siRNA

Hydrolytically degrading nano-polyplexes (HDG-NPs) that reverse charge through conversion of tertiary amines to carboxylic acids were investigated to improve intracellular un-packaging of siRNA and target gene silencing compared to a non-degradable analog (non-HDG-NPs). Both NP types comprised reversible addition-fragmentation chain-transfer (RAFT) synthesized diblock copolymers of a poly(ethylene glycol) (PEG) corona-forming block and a cationic block for nucleic acid packaging that incorporated butyl methacrylate (BMA) and either dimethylaminoethyl methacrylate (DMAEMA, non-HDG-NPs) or dimethylaminoethyl acrylate (DMAEA, HDG-NPs). HDG-NPs decreased significantly in size and released significantly more siRNA (∼40%) than non-HDG-NPs after 24 h in aqueous solution. While both HDG-NPs and non-HDG-NPs had comparable uptake and cytotoxicity up to 150 nM siRNA doses, HDG-NPs achieved significantly higher target gene silencing of the model gene luciferase in vitro. High resolution FRET confocal microscopy was used to monitor the intracellular un-packaging of siRNA. Non-HDG-NPs had significantly higher FRET efficiency than HDG-NPs, indicating that siRNA delivered from HDG-NPs was more fully un-packaged and therefore had improved intracellular bioavailability.

Coarse-Grained Simulation of Polycation/DNA-Like Complexes: Role of Neutral Block

Complexes formed by polycations and DNA are of great research interest because of their prospective application in gene therapy. Whereas the applications of multiblock based polycation generally exhibit promising features, a thorough understanding on the effect of neutral block incorporated in polycation is still lacking. By using coarse-grained dynamics simulation with the help of a simple model for solvent mediated interaction, we perform a theoretical study on the physicochemical properties of various polyplexes composed of a single DNA-like polyanion chain and numbers of linear polycationic chains with different modifications. By analyzing various properties, we find the hydrophobic/hydrophilic modifications of linear polycations may bring an improvement on one aspect of the properties as gene carrier but also involve a trade-off with another one. In particular, polycation with a hydrophobic middle block and a hydrophilic tail block display distinct advantages among di- and triblock linear polycations as gene carrier, while careful design of the hydrophobic block should be made to reduce the zeta potential. The simulation results are compared with available experimental data displaying good agreements.

Cationic triblock copolymer micelles enhance antioxidant activity, intracellular uptake and cytotoxicity of curcumin

The aim of the present study was to develop curcumin loaded cationic polymeric micelles and to evaluate their loading, preservation of curcumin antioxidant activity and intracellular uptake ability. The micelles were prepared from a triblock copolymer consisting of poly(ϵ-caprolactone) and very short poly(2-(dimethylamino) ethyl methacrylate) segments (PDMAEMA9-PCL70-PDMAEMA9). The micelles showed monomodal size distribution, mean diameter of 145 nm, positive charge (+72 mV), critical micellar concentration around 0.05 g/l and encapsulation efficiency of 87%. The ability of the micellar curcumin to scavenge the ABTS radical and hypochlorite ions was higher than that of the free curcumin. Confocal microscopy revealed that the uptake of curcumin by chronic myeloid leukemia derived K-562 cells and human multiple myeloma cells U-266 was more intensive when curcumin was loaded into the micelles. These results correlated with the higher cytotoxicity of the micellar curcumin compared to free curcumin. Intraperitoneal treatment of Wistar rats indicated that PDMAEMA-PCL-PDMAEMA copolymer, comprising very short cationic chains, did not change the levels of malondialdehyde and glutathione in livers indicating an absence of oxidative stress. Thus, PDMAEMA-PCL-PDMAEMA triblock micelles could be considered efficient and safe platform for curcumin delivery.

Enhanced DNA release from disulfide-containing layered nanocomplexes by heparin-electrostatic competition

Polycationic vectors are often used to deliver DNA for cancer therapies, but their inefficiency in releasing DNA from the polyplexes after endosomal escape limits DNA transcription and their efficient application in vivo. In this study, DNA/PEI polyplexes were cross-linked by a reduction-sensitive disulfide bond and then further complexed with electrostatic competitive heparin (HP) and hyaluronidase (HAase)-sensitive hyaluronate (HA) to obtain DNA/PEIS/HA-HP (DPSHA-HP). DPSHA-HP was stable in an extracellular environment (pH = 7.4) and degraded by HAase after targeted HA receptor CD44-mediated cell endocytosis, causing the outer shielding of the nanocomplex to loosen. The resulting partially exposed disulfide-linked DNA/PEI nanocomplexes efficiently ruptured the endosome, facilitating the cleavage of disulfide bonds and the release of DNA/PEI polyplexes into the cytoplasm, where DNA release from the polyplexes was remarkably enhanced due to strong electrostatic competition of HP with PEI. Consequently, DPSHA-HP exhibited excellent DNA transfection of the target cells, better than disulfide cross-linked DNA/PEI (25 kDa) and DNA/PEIS/HA. Moreover, these novel layered nanocomplexes have high efficiency in down-regulating B-cell-specific Moloney murine leukemia virus insertion site 1 (Bmi-1) and exhibit significant inhibition of tumor formation with minimal toxicity in a mouse tumor model.

Retracted Article: A multifunctional self-dissociative polyethyleneimine derivative coating polymer for enhancing the gene transfection efficiency of DNA/polyethyleneimine polyplexes in vitro and in vivo

A novel coating polymer LPHF is developed for the first time to elevate the transfection efficiency of DP binary polyplexes in vitro and in vivo.

Intracellular redox potential-responsive micelles based on polyethylenimine-cystamine-poly(ε-caprolactone) block copolymer for enhanced miR-34a delivery

A novel polymer polyethylenimine-cystamine-poly(ε-caprolactone) with intracellular redox potential-responsive cleavable ability was synthesized and fabricated the micelles as smart gene vectors.

Efficient targeted gene delivery by a novel PAMAM/DNA dendriplex coated with hyaluronic acid

Aim: To design and develop a novel target-specific DNA-delivery system using hyaluronic acid (HA)–polyamidoamine (PAMAM) conjugates (P–HA). Materials & methods: The coupling of HA to the PAMAM dendrimer was analyzed by 1H-NMR and elemental analysis (CHN). Their properties were characterized in terms of size and zeta-potential and evaluated for in vitro and in vivo transfection efficiency. Results: The designed covalent HA-dendriplexes enhanced gene transfection of pCMV-Luc reporter gene in overexpressing CD44-receptor cancer cells. They were also more efficient in transfecting MDA-MB231 cells than conventional PEI-polyplexes. The cytotoxicity of the covalent HA-dendriplexes was lower than when using conventional polyethylenimine-polyplexes. In vivo studies showed that these targeted complexes were also efficient for delivering pCMVLuc in different organs of healthy mice, as well as in tumors of C57BL/6 animals. Conclusions: The HA-dendriplexes developed in this work may offer an advantageous alternative to conventional cationic polymer-based formulations for DNA delivery into cancer cells in an efficient and safe manner.

Polyethyleneimine/DNA polyplexes with reduction-sensitive hyaluronic acid derivatives shielding for targeted gene delivery

The natural anionic polysaccharide hyaluronic acid (HA) was modified by introducing reduction-sensitive disulfide bond between the carboxyl groups and the backbone of HA (HA-SS-COOH). HA-SS-COOH and its corresponding unmodified stable analog HA were used to shield DNA/PEI polyplexes (DP) to form ternary complexes (DPS and DPH complexes). The shielding/deshielding effect was tested along with size, zeta potential, cell viability and transfection. Both DPS and DPH complexes showed increase in size, decrease in zeta potential and low cytotoxicity in physiological conditions due to the anionic shielding. In the reductive environment, only HA-SS-COOH coated ternary complexes (DPS) demonstrated the size increase and recovered high positive zeta potential. DPS complexes showed an up to 14-fold higher transfection than the stable coated one, indicating the efficiency of the reduction-responsive deshielding design. Moreover, the presence of extra free HA inhibited the transfection of DPS on HepG2 and B16F10 cells with HA receptor expression, while displaying no effect on non-targeted NIH3T3 cells. More rapid cellular association of DPS with HepG2 was observed, thus confirming the targeting reservation of disulfide bond modified HA. Intratumoral injection of DPS complexes resulted in much higher accumulation and luciferase expression in the tumor bearing C57BL/6 mice. Both in vitro and in vivo results demonstrated the successful combination of deshielding and target functions in HA derivatives for gene delivery.

Preparation of cationic nanogels for nucleic acid delivery

Cationic nanogels with site-selected functionality were designed for the delivery of nucleic acid payloads targeting numerous therapeutic applications. Functional cationic nanogels containing quaternized 2-(dimethylamino)ethyl methacrylate and a cross-linker with reducible disulfide moieties (qNG) were prepared by activators generated by electron transfer (AGET) atom transfer radical polymerization (ATRP) in an inverse miniemulsion. Polyplex formation between the qNG and nucleic acid exemplified by plasmid DNA (pDNA) and short interfering RNA (siRNA duplexes) were evaluated. The delivery of polyplexes was optimized for the delivery of pDNA and siRNA to the Drosophila Schneider 2 (S2) cell-line. The qNG/nucleic acid (i.e., siRNA and pDNA) polyplexes were found to be highly effective in their capabilities to deliver their respective payloads.

A review of RGD-functionalized nonviral gene delivery vectors for cancer therapy

The development of effective treatments that enable many patients suffering from cancer to be successfully cured is highly demanded. Angiogenesis, which is a process for the formation of new capillary blood vessels, has a crucial role in solid tumor progression and the development of metastasis. Antiangiogenic therapy designed to prevent tumor angiogenesis, thereby arresting the growth or spread of tumors, has emerged as a non-invasive and safe option for cancer treatment. Due to the fact that integrin receptors are overexpressed on the surface of angiogenic endothelial cells, various strategies have been made to develop targeted delivery systems for cancer gene therapy utilizing integrin-targeting peptides with an exposed arginine-glycine-aspartate (RGD) sequence. The aim of this review is to summarize the progress and prospect of RGD-functionalized nonviral vectors toward targeted delivery of genetic materials in order to achieve an efficient therapeutic outcome for cancer gene therapy, including antiangiogenic therapy.

Effects of branched or linear architecture of bioreducible poly(amido amine)s on their in vitro gene delivery properties

In this study, the gene delivery properties of new hyperbranched poly(amido amine)s (PAAs) with disulfide linkages in the main chain were investigated in comparison with their linear analogs. Eight different bioreducible PAAs were prepared by Michael addition of N,N'-bisacryloylpiperazine (BP) with cystamine (CYST) or N,N'-dimethylcystamine (DMC) and of N,N'-cystaminebisacrylamide (CBA) with N,N'-ethylenediamine (EDA) or N,N'-dimethylethylenediamine (DMEDA). In order to study the effect of terminal groups on the transfection efficiency, each polymer was terminated with 4-aminobutanol (ABOL) or with 2-aminoethanol (ETA). The hyperbranched and the linear PAAs generally formed polyplexes with plasmid DNA with sizes around 200nm and positive zeta potentials ranging from +10 to +22mV at polymer/DNA weight ratios equal or higher than 3/1. Remarkably low or no cytotoxicity was observed for both hyperbranched and linear PAAs. Hyperbranched CBA-containing PAAs showed higher gene expression in DNA transfection tests with COS-7 cells than their linear analogs and up to two times higher than linear PEI that was used as the reference polymer. Transfection efficiencies of the branched PAAs were generally enhanced by the presence of serum, which is a promising property for future in vivo studies with these hyperbranched PAAs. In this study the ease of synthetic modification of both linear and hyperbranched poly(amido amide)s and the versatility of hyperbranched PAAs in regulating DNA transfection and cytotoxicity are demonstrated. The results show the large possibilities for this class of polymers to provide polymeric vectors with controllable properties for gene therapy applications.

Design and biophysical characterization of bioresponsive degradable poly(dimethylaminoethyl methacrylate) based polymers for in vitro DNA transfection

Water-soluble, degradable polymers based on poly(N,N-dimethylaminoethyl methacrylate) (PDMAEMA) with low cytotoxicity and good p-DNA transfection efficiency are highlighted in this article. To solve the nondegradability issue of PDMAEMA, new polymers based on DMAEMA and 5,6-benzo-2-methylene-1,3-dioxepane (BMDO) for gene transfection were synthesized. A poly(ethylene oxide) (PEO) azo-initiator was used as free-radical initiator. PEGylation was performed to improve water solubility and to reduce cytotoxicity of the polymers. The resulting polymers contain hydrolyzable ester linkages in the backbone and were soluble in water even with very high amounts of ester linkages. These degradable copolymers showed significantly less toxicity with a MTT assay using L929 cell lines and demonstrated promising DNA transfection efficiency when compared with the gold standard poly(ethyleneimine). Bioresponsive properties of the corresponding quaternized DMAEMA based degradable polymers were also studied. Although the quaternized DMAEMA copolymers showed enhanced water solubility, they were inferior in gene transfection and toxicity as compared to the unquaternized copolymers.

RGD targeting hyaluronic acid coating system for PEI-PBLG polycation gene carriers

Hyaluronic acid (HA), a natural anionic mucopolysaccharide, was used to coat polyethylenimine-poly(γ-benzyl L-glutamate)/DNA (PEI-PBLG/DNA) complexes. HA was further modified by introducing RGD peptide with grafting density of one RGD in every 1.9 HA repeating units. HA can coat the cationic surface of PEI-PBLG/DNA complexes without destroying them even at high weight ratio of HA/PEI-PBLG/DNA=40/10/1. Coating the complexes by HA and HA-RGD caused lower surface charges and little bigger size than the naked PEI-PBLG/DNA. HA/PEI-PBLG/DNA has little lower transfection efficiency compared with naked PEI-PBLG/DNA, while the transfection efficiency of HA-RGD/PEI-PBLG/DNA is 9.7 times of HA/PEI-PBLG/DNA for the RGD target bonding affinity to the receptors on the cell surface. HA coating on PEI-PBLG/DNA reduced the electrostatic binding affinity to the cells while the RGD binding affinity for integrin on HeLa cells can not only compensate the reduced binding affinity but also enhance the affinity for HA-RGD/PEI-PBLG/DNA. RGD and RDG competition assay and lactate dehydrogenase (LDH) release studies further confirmed the specific target functions of RGD on HA. Cell viability measurements confirmed the high viability (above 70% viability) of the cells treated with HA-RGD and HA coated complex particles. These results would show that HA-RGD coated PEI-PBLG/DNA complexes have an attractive feature to a targeting in vivo non-viral gene delivery system.

Efficient siRNA delivery based on PEGylated and partially quaternized polyamine nanogels: enhanced gene silencing activity by the cooperative effect of tertiary and quaternary amino groups in the core

For the development of an siRNA delivery system using polyion complexes (PICs) based on PEGylated nanogel consisting of a cross-linked poly[2-(N,N-diethylaminoethyl) methacrylate] (PEAMA) gel core and tethered poly(ethylene glycol) (PEG) chains, quaternary ammonium groups were introduced in the polyamine gel core to enhance the binding ability with siRNA and the stability of the PICs. Consequently, the quaternization of the polyamine core of the nanogel facilitated the binding ability with siRNA at a low N/P ratio, and the stability against polyanion displacement was enhanced as the degree of quaternization (DQ) of the nanogel increased. Although the installation of the positively charged quaternary ammonium moieties in the core of the nanogel resulted in the increment of the xi-potential of the PICs (e.g. + 23 mV for DQ=100%), the cytotoxicity was reduced with the increase of DQ presumably due to the hydrophilic character of the quaternary ammonium groups. The installation of quaternary ammonium groups in the core of the nanogel enhanced the endogenous gene silencing activity against the survivin gene in human hepatocarcinoma (HuH-7 cells), especially, the partly quaternized polyamine nanogel (DQ=10%) showed the highest gene silencing ability among the quaternized polyamine nanogels, including the tertiary amine nanogel. The cellular uptake analysis of the Rhodamine B-labeled Q-nanogel/fluorescein-labeled siRNA complex revealed that the quaternization of PEAMA moieties enhanced the cellular uptake level of fluorescein-labeled siRNA with the increase in DQ, whereas the cellular uptake of the Rhodamine B-labeled Q-nanogels was almost of the same level regardless of the DQ value, indicating that significant cellular uptake of the fluorescein-labeled siRNA is most likely due to the enhancement of the binding ability with siRNA in the serum-containing medium. Note that the endosomal escape efficiency was reduced with increase in the DQ value due to the decrease in the buffering capacity (tertiary amino groups) of the PEAMA core. On the basis of these results, the ratio of quaternary ammonium groups to tertiary amino groups in the core of the nanogel plays a pivotal role in the achievement of significant gene silencing through enhanced cellular uptake (quaternary ammonium groups) and subsequent endosomal escape (tertiary amino groups).

Folate conjugated phosphorylcholine-based polycations for specific targeting in nucleic acids delivery

Folic acid has been investigated as a targeting ligand for imaging and therapeutic agent for over a decade; however, studies on its use in targeting of nonviral gene or nucleic acids delivery systems are sparse. This study assesses potential application of a new folic acid conjugate with aminomethacrylate-phosphoryl-choline based copolymer (DMAEMA-MPC-FA) as a targeting gene delivery vector. The folate-conjugated polymers produce colloidally stable polyplexes with a particle size <200 nm and demonstrate the ability to protect DNA from enzymatic degradation to a certain extent. In cells that overexpress folate receptors (MCF-7 and KB cultures), the conjugated systems show a folate-specific association and achieved significantly enhanced transfection efficiency, compared to the nonconjugated control, with a dramatically reduced nonspecific cellular association. The transfection enhancement is achieved without a corresponding increase in cellular association, suggesting that an internal cellular trafficking of folate-conjugated system may be altered, resulting in an increased transfection efficacy. In summary, a new folate-conjugated aminomethacrylate-phosphorylcholine copolymer is capable of forming colloidal complexes with DNA, modulating their specific cell uptake and improving the level of cell transfection in folate expressing cells.

Characterization of complexation of poly (N-isopropylacrylamide-co-2-(dimethylamino) ethyl methacrylate) thermoresponsive cationic nanogels with salmon sperm DNA

Thermoresponsive cationic nanogel (TCNG) networks based on N-isopropylacrylamide (NIPAM), 2-(dimethylamino)ethyl methacrylate (DMAEMA), and quaternary alkyl ammonium halide salts of DMAEMA (DMAEMAQ) were synthesized by dispersion polymerization technique. The thermoresponsive properties of TCNGs and TCNG-salmon sperm DNA (sasDNA) polyplexes were characterized in aqueous media of various pH and ionic strength. P[NIPAM] and P[NIPAM/DMAEMA] TCNGs exhibited sharp volume phase transition (VPT) in water at critical temperatures (T_c) of 32 °C and 36 °C, respectively. Quaternized P[NIPAM/DMAEMAQ] TCNGs did not undergo sharp VPT up to 50 °C. The VPT of uncomplexed TCNGs were sensitive to the ionic composition and ionic strength of salts in solution, but were insensitive to pH in the range 5.0 to 7.4. The VPT of P[NIPAM/DMAEMAQ]/sasDNA diminished in magnitude with increasing W_p/W_d suggesting greater compaction of the polyplexes. The distinct phase-transition properties of P[NIPAM/DMAEMA]/sasDNA and P[NIPAM/DMAEMAQ]/sasDNA polyplexes were attributed to the condensing capability of polycations and to differences in the spatial distribution of structural charges in quaternized and nonquaternized networks. The findings demonstrate that stable TCNGs can be prepared with controllable responsive properties determined by the nature of the cationic charge incorporated and may have potential as vehicles for DNA delivery.