Characterization of a multifunctional PEG-based gene delivery system containing nuclear localization signals and endosomal escape peptides

Evaluation of Poly(N-Ethyl Pyrrolidine Methacrylamide) (EPA) and Derivatives as Polymeric Vehicles for miRNA Delivery to Neural Cells

MicroRNAs (miRNAs) are endogenous, short RNA oligonucleotides that regulate the expression of hundreds of proteins to control cells' function in physiological and pathological conditions. miRNA therapeutics are highly specific, reducing the toxicity associated with off-target effects, and require low doses to achieve therapeutic effects. Despite their potential, applying miRNA-based therapies is limited by difficulties in delivery due to their poor stability, fast clearance, poor efficiency, and off-target effects. To overcome these challenges, polymeric vehicles have attracted a lot of attention due to their ease of production with low costs, large payload, safety profiles, and minimal induction of the immune response. Poly(N-ethyl pyrrolidine methacrylamide) (EPA) copolymers have shown optimal DNA transfection efficiencies in fibroblasts. The present study aims to evaluate the potential of EPA polymers as miRNA carriers for neural cell lines and primary neuron cultures when they are copolymerized with different compounds. To achieve this aim, we synthesized and characterized different copolymers and evaluated their miRNA condensation ability, size, charge, cytotoxicity, cell binding and internalization ability, and endosomal escape capacity. Finally, we evaluated their miRNA transfection capability and efficacy in Neuro-2a cells and rat primary hippocampal neurons. The results indicate that EPA and its copolymers, incorporating β-cyclodextrins with or without polyethylene glycol acrylate derivatives, can be promising vehicles for miRNA administration to neural cells when all experiments on Neuro-2a cells and primary hippocampal neurons are considered together.

The Reduced-Charge Melittin Analogue MelP5 Improves the Transfection of Non-Viral DNA Nanoparticles

Melittin is a 26 amino acid amphiphilic alpha-helical peptide derived from honeybee venom. Prior studies have incorporated melittin into non-viral delivery systems to effect endosomal escape of DNA nanoparticles and improve transfection efficiency. Recent advances have led to the development of two newer melittin analogues, MelP5 and Macrolittin 70, with improved pore formation in lipid bilayers while possessing fewer positive charges relative to natural melittin. Consequently, MelP5 and Macrolittin 70 were conjugated through a disulfide bond to a DNA binding polyacridine peptide. The resulting peptide conjugates were used to prepare DNA nanoparticles to compare their relative endosomolytic potency by transfection of HepG2 cells. Melittin and MelP5 conjugates were equally potent at mediating in vitro gene transfer, whereas PEGylation of DNA nanoparticles revealed improved transfection with MelP5 relative to melittin. The results demonstrate the ability to substitute a potent, reduced charge analogue of melittin to improve overall DNA nanoparticle biocompatibility needed for in vivo testing.

Uniform iron oxide nanoparticles reduce the required amount of polyethylenimine in the gene delivery to mesenchymal stem cells

Cationic polyethylenimine (PEI) is regarded as the 'golden standard' of non-viral gene vectors. However, the superiority of PEI with high positive charge density also induces its major drawback of cytotoxicity, which restricts its application for an effective and safe gene delivery to stem cells. To redress this shortcoming, herein, a magnetic gene complex containing uniform iron oxide nanoparticles (UIONPs), plasmid DNA, and free PEI is prepared through electrostatic interactions for the gene delivery to bone marrow-derived mesenchymal stem cells (BM-MSCs). Results show that UIONPs dramatically promote the gene delivery to BM-MSCs using the assistance of magnetic force. In addition, decreasing the free PEI nitrogen to DNA phosphate (N/P) ratio from 10 to 6 has little adverse impact on the transgene expression levels (over 300 times than that of PEI alone at the N/P ratio of 6) and significantly reduces the cytotoxicity to BM-MSCs. Further investigations confirmed that the decrease of free PEI has little influence on the cellular uptake after applying external magnetic forces, but that the reduced positive charge density decreases the cytotoxicity. The present study demonstrates that magnetic gene delivery not only contributes to the enhanced gene expression but also helps to reduce the required amount of PEI, providing a potential strategy for an efficient and safe gene delivery to stem cells.

AZD9291 Resistance Reversal Activity of a pH-Sensitive Nanocarrier Dual-Loaded with Chloroquine and FGFR1 Inhibitor in NSCLC

AZD9291 can effectively prolong survival of non-small cell lung cancer (NSCLC) patients. Unfortunately, the mechanism of its acquired drug resistance is largely unknown. This study shows that autophagy and fibroblast growth factor receptor 1 signaling pathways are both activated in AZD9291 resistant NSCLC, and inhibition of them, respectively, by chloroquine (CQ) and PD173074 can synergistically reverse AZD9291 resistance. Herein, a coloaded CQ and PD173074 pH-sensitive shell-core nanoparticles CP@NP-cRGD is developed to reverse AZD9291 resistance in NSCLC. CP@NP-cRGD has a high encapsulation rate and stability, and can effectively prevent the degradation of drugs in circulation process. CP@NP-cRGD can target tumor cells by enhanced permeability and retention effect and the cRGD peptide. The pH-sensitive CaP shell can realize lysosome escape and then release drugs successively. The combination of CP@NP-cRGD and AZD9291 significantly induces a higher rate of apoptosis, more G0/G1 phase arrest, and reduces proliferation of resistant cell lines by downregulation of p-ERK1/2 in vitro. CQ in CP@NP-cRGD can block protective autophagy induced by both AZD9291 and PD173074. CP@NP-cRGD combined with AZD9291 shows adequate tumor enrichment, low toxicity, and excellent antitumor effect in nude mice. It provides a novel multifunctional nanoparticle to overcome AZD9291 resistance for potential clinical applications.

Gene transfer to plants by electroporation: methods and applications

Developing gene transfer technologies enables the genetic manipulation of the living organisms more efficiently. The methods used for gene transfer fall into two main categories; natural and artificial transformation. The natural methods include the conjugation, transposition, bacterial transformation as well as phage and retroviral transductions, contain the physical methods whereas the artificial methods can physically alter and transfer genes from one to another organisms' cell using, for instance, biolistic transformation, micro- and macroinjection, and protoplast fusion etc. The artificial gene transformation can also be conducted through chemical methods which include calcium phosphate-mediated, polyethylene glycol-mediated, DEAE-Dextran, and liposome-mediated transfers. Electrical methods are also artificial ways to transfer genes that can be done by electroporation and electrofusion. Comparatively, among all the above-mentioned methods, electroporation is being widely used owing to its high efficiency and broader applicability. Electroporation is an electrical transformation method by which transient electropores are produced in the cell membranes. Based on the applications, process can be either reversible where electropores in membrane are resealable and cells preserve the vitality or irreversible where membrane is not able to reseal, and cell eventually dies. This problem can be minimized by developing numerical models to iteratively optimize the field homogeneity considering the cell size, shape, number, and electrode positions supplemented by real-time measurements. In modern biotechnology, numerical methods have been used in electrotransformation, electroporation-based inactivation, electroextraction, and electroporative biomass drying. Moreover, current applications of electroporation also point to some other uncovered potentials for various exploitations in future.

Chloroquine in combination with aptamer-modified nanocomplexes for tumor vessel normalization and efficient erlotinib/Survivin shRNA co-delivery to overcome drug resistance in EGFR-mutated non-small cell lung cancer

Although novel molecular targeted drugs have been recognized as an effective therapy for non-small cell lung cancer (NSCLC) harboring epidermal growth factor receptor (EGFR) activating mutations, their efficacy fails to meet the expectation due to the acquired resistance in tumors. Up-regulation of the anti-apoptotic protein Survivin was shown to contribute to the resistance to EGFR tyrosine kinase inhibitors (TKI) in EGFR mutation-positive NSCLC. However, the unorganized tumor blood vessels impeded drug penetration into tumor tissue. The resulting insufficient intracellular drug/gene delivery in drug-resistant cancer cells remarkably weakened the drug efficacy in NSCLC. In this work, a multi-functional drug delivery system AP/ES was developed by using anti-EGFR aptamer (Apt)-modified polyamidoamine to co-deliver erlotinib and Survivin-shRNA. Chloroquine (CQ) was used in combination with AP/ES to normalize tumor vessels for sufficient drug/gene delivery to overcome drug resistance in NSCLC cells. The obtained AP/ES possessed desired physicochemical properties, good biostability, controlled drug release profiles, and strong selectivity to EGFR-mutated NSCLC mediated by Apt. CQ not only enhanced endosomal escape ability of AP/ES for efficient gene transfection to inhibit Survivin, but also showed strong vessel-normalization ability to improve tumor microcirculation, which further promoted drug delivery and enhanced drug efficacy in erlotinib-resistant NSCLC cells. Our innovative gene/drug co-delivery system in combination with CQ showed a promising outcome in fighting against erlotinib resistance both in vitro and in vivo. This work indicates that normalization of tumor vessels could help intracellular erlotinib/Survivin-shRNA delivery and the down-regulation of Survivin could act synergistically with erlotinib for reversal of erlotinib resistance in EGFR mutation-positive NSCLC.

STATEMENT OF SIGNIFICANCE

NSCLC patients who benefited from EGFR-TKIs inevitably developed acquired resistance. Previous research focused on synthesis of new generation of molecular targeted drugs that could irreversibly inhibit EGFR with a particular gene mutation to overcome drug resistance. However, they failed to inhibit EGFR with other gene mutations. Activation of bypass signaling pathway and the changes of tumor microenvironment are identified as two of the mechanisms of acquired resistance to EGFR-TKIs. We therefore constructed multifunctional gene/drug co-delivery nanocomplexes AP/ES co-formulated with chloroquine that could target the both two mechanisms. We found that chloroquine not only enhanced endosomal escape ability of AP/ES for efficient gene transfection to inhibit Survivin, but also showed strong vessel-normalization ability to improve tumor microcirculation, which further promoted drug delivery into tumor tissue and enhanced drug efficacy in erlotinib-resistant NSCLC.

Exploring the role of peptides in polymer-based gene delivery

Polymers are widely studied as non-viral gene vectors because of their strong DNA binding ability, capacity to carry large payload, flexibility of chemical modifications, low immunogenicity, and facile processes for manufacturing. However, high cytotoxicity and low transfection efficiency substantially restrict their application in clinical trials. Incorporating functional peptides is a promising approach to address these issues. Peptides demonstrate various functions in polymer-based gene delivery systems, such as targeting to specific cells, breaching membrane barriers, facilitating DNA condensation and release, and lowering cytotoxicity. In this review, we systematically summarize the role of peptides in polymer-based gene delivery, and elaborate how to rationally design polymer-peptide based gene delivery vectors.

STATEMENT OF SIGNIFICANCE

Polymers are widely studied as non-viral gene vectors, but suffer from high cytotoxicity and low transfection efficiency. Incorporating short, bioactive peptides into polymer-based gene delivery systems can address this issue. Peptides demonstrate various functions in polymer-based gene delivery systems, such as targeting to specific cells, breaching membrane barriers, facilitating DNA condensation and release, and lowering cytotoxicity. In this review, we highlight the peptides' roles in polymer-based gene delivery, and elaborate how to utilize various functional peptides to enhance the transfection efficiency of polymers. The optimized peptide-polymer vectors should be able to alter their structures and functions according to biological microenvironments and utilize inherent intracellular pathways of cells, and consequently overcome the barriers during gene delivery to enhance transfection efficiency.

Delivery of the autofluorescent protein R-phycoerythrin by calcium phosphate nanoparticles into four different eukaryotic cell lines (HeLa, HEK293T, MG-63, MC3T3): Highly efficient, but leading to endolysosomal proteolysis in HeLa and MC3T3 cells

Nanoparticles can be used as carriers to transport biomolecules like proteins and synthetic molecules across the cell membrane because many molecules are not able to cross the cell membrane on their own. The uptake of nanoparticles together with their cargo typically occurs via endocytosis, raising concerns about the possible degradation of the cargo in the endolysosomal system. As the tracking of a dye-labelled protein during cellular uptake and processing is not indicative of the presence of the protein itself but only for the fluorescent label, a label-free tracking was performed with the red-fluorescing model protein R-phycoerythrin (R-PE). Four different eukaryotic cell lines were investigated: HeLa, HEK293T, MG-63, and MC3T3. Alone, the protein was not taken up by any cell line; only with the help of calcium phosphate nanoparticles, an efficient uptake occurred. After the uptake into HeLa cells, the protein was found in early endosomes (shown by the marker EEA1) and lysosomes (shown by the marker Lamp1). There, it was still intact and functional (i.e. properly folded) as its red fluorescence was detected. However, a few hours after the uptake, proteolysis started as indicated by the decreasing red fluorescence intensity in the case of HeLa and MC3T3 cells. 12 h after the uptake, the protein was almost completely degraded in HeLa cells and MC3T3 cells. In HEK293T cells and MG-63 cells, no degradation of the protein was observed. In the presence of Bafilomycin A1, an inhibitor of acidification and protein degradation in lysosomes, the fluorescence of R-PE remained intact over the whole observation period in the four cell lines. These results indicate that despite an efficient nanoparticle-mediated uptake of proteins by cells, a rapid endolysosomal degradation may prevent the desired (e.g. therapeutic) effect of a protein inside a cell.

Carbon dioxide-modified polyethylenimine as a novel gene delivery vector and its in vitro validation

In this work, the CO₂-modified polyethylenimine, as a novel delivery vector, has been validated by combining with the plasmid DNA to form plasmid DNA/CO₂-modified polyethylenimine complexes. We have modified polyethylenimine using CO₂ to partially convert amine groups to carbamic acid groups. The buffering capacity and the plasmid DNA binding ability of the CO₂-modified polyethylenimine and PEI-25 (polyethylenimine with Mw = 25 kDa) were characterized by acid-base titration and agarose gel electrophoresis, respectively. The particle size and zeta potential of the complexes were determined using a Zetasizer Nano ZS. Resistance to nuclease digestion was determined via DNase I protection assay. The cytotoxicity was measured by the MTT assay. The transfection efficiency of the complexes has been evaluated by flow cytometry. It is observed that the condensation capacity of CO₂-modified polyethylenimine is still comparable to polyethylenimine and the CO₂-modified polyethylenimine can protect plasmid DNA from degradation by DNase I. The diameter of the plasmid DNA/CO₂-modified polyethylenimine complex is around 140 nm and the zeta potential decreases. MTT assays confirm that the cytotoxicity is much lower for plasmid DNA/CO₂-modified polyethylenimine than for plasmid DNA/PEI-25. The flow cytometry found that in serum-free medium the transfection efficiency can reach a value of ∼60% for plasmid DNA/CO₂-modified polyethylenimine, and in 10% fetal bovine serum medium, the transfection efficiency is still as high as ∼40%, which is much higher than that of plasmid DNA/PEI-25. CO₂-modified polyethylenimine could be a novel and promising nonviral gene vector for gene therapy.

Multifunctional oligomer incorporation: a potent strategy to enhance the transfection activity of poly(l-lysine)

The multifunctional oligomer incorporation strategy is used for the first time to evaluate target effects by the ligand modified oligomer assembly, forming complexes with DNA and polycations.

A novel multifunctional biomimetic Au@BSA nanocarrier as a potential siRNA theranostic nanoplatform

A novel siRNA nanocarrier based on biomimetic Au@BSA nanoflowers is fabricated which could serve as a potential theranostic nanoplatform.

Preparation and evaluation of polyethylenimine-functionalized carbon nanotubes tagged with 5TR1 aptamer for targeted delivery of Bcl-xL shRNA into breast cancer cells

In this study, single-walled carbon nanotubes (SWCNTs) were covalently attached to poly(ethylene glycol) (PEG) and polyethylenimine (PEI) 10 kDa, or its derivatives, to fabricate efficient carriers for gene delivery. PEI 10 kDa was modified by alkylcarboxylation of its primary amines with a series of ω-bromo-alkylcarboxylic acids to provide a range of vectors with increased lipophilicity. PEI 10 kDa or its alkylcarboxylate derivatives were conjugated to SWCNT-PEG to develop vectors possessing effective DNA condensation ability which can interact with cell membrane via both nano-needle mechanism and electrostatic interactions produced by SWCNT and PEI, respectively. The results demonstrated that SWCNT-PEG-PEI and SWCNT-PEG-derivatives of PEI could condense DNA into particle size less than 150 nm with positive surface charges between 6.3-30.8 mV. To improve the antitumor efficacy, we developed a targeted gene delivery system using a 5 TR1 aptamer. The most efficient vector, which was prepared by attachment of SWCNT-PEG to modified PEI 10 kDa with 10-bromodecanoic acid (10%), showed 8.5-10 folds enhancement in transfection activity at C/P ratio 6 as compared to the gold standard PEI 25 kDa at C/P ratio of 0.8. We also showed that the selected polyplex could efficiently and selectively transfer plasmid shRNA to MUC1 positive cells.

The role of ligand density and size in mediating quantum dot nuclear transport

Studying the effects of the physicochemical properties of nanomaterials on cellular uptake, toxicity, and exocytosis can provide the foundation for designing safer and more effective nanoparticles for clinical applications. However, an understanding of the effects of these properties on subcellular transport, accumulation, and distribution remains limited. The present study investigates the effects of surface density and particle size of semiconductor quantum dots on cellular uptake as well as nuclear transport kinetics, retention, and accumulation. The current work illustrates that cellular uptake and nuclear accumulation of nanoparticles depend on surface density of the nuclear localization signal (NLS) peptides with nuclear transport reaching a plateau at 20% surface NLS density in as little as 30 min. These intracellular nanoparticles have no effects on cell viability up to 72 h post treatment. These findings will set a foundation for engineering more sophisticated nanoparticle systems for imaging and manipulating genetic targets in the nucleus.

Multifunctional non-viral gene vectors with enhanced stability, improved cellular and nuclear uptake capability, and increased transfection efficiency

We have developed a new multifunctional, non-viral gene delivery platform consisting of cationic poly(amine-co-ester) (PPMS) for DNA condensation, PEG shell for nanoparticle stabilization, poly(γ-glutamic acid) (γ-PGA) and mTAT (a cell-penetrating peptide) for accelerated cellular uptake, and a nuclear localization signal peptide (NLS) for enhanced intracellular transport of DNA to the nucleus. In vitro study showed that coating of the binary PPMS/DNA polyplex with γ-PGA promotes cellular uptake of the polyplex particles, particularly by γ-glutamyl transpeptidase (GGT)-positive cells through the GGT-mediated endocytosis pathway. Conjugating PEG to the γ-PGA led to the formation of a ternary PPMS/DNA/PGA-g-PEG polyplex with decreased positive charges on the surface of the polyplex particles and substantially higher stability in serum-containing aqueous medium. The cellular uptake rate was further improved by incorporating mTAT into the ternary polyplex system. Addition of the NLS peptide was designed to facilitate intracellular delivery of the plasmid to the nucleus--a rate-limiting step in the gene transfection process. As a result, compared with the binary PPMS/LucDNA polyplex, the new mTAT-quaternary PPMS/LucDNA/NLS/PGA-g-PEG-mTAT system exhibited reduced cytotoxicity, remarkably faster cellular uptake rate, and enhanced transport of DNA to the nucleus. All these advantageous functionalities contribute to the remarkable gene transfection efficiency of the mTAT-quaternary polyplex both in vitro and in vivo, which exceeds that of the binary polyplex and commercial Lipofectamine™ 2000/DNA lipoplex. The multifunctional mTAT-quaternary polyplex system with improved efficiency and reduced cytotoxicity represents a new type of promising non-viral vectors for the delivery of therapeutic genes to treat tumors.

Fabrication of novel reduction-sensitive gene vectors based on three-armed peptides

To address the inherent barriers of gene transfection, two reduction-sensitive branched polypeptides (RBPs) are synthesized and explored as novel non-viral gene vectors. The introduced disulfide linkages in RBPs facilitate glutathione-triggered intracellular gene release and reduce polymer degradation-induced cytotoxicity. Furthermore, the highly branched architecture concurrently realizes multivalency for strong DNA binding and elicits conformational flexibility for tight DNA compacting, which are beneficial for cellular entry. To increase the endosomal escape of plasmid DNA, pH-sensitive histidyl residues are incorporated into RBPs to improve buffer capacity in an acidic environment. In vitro study demonstrates that RBPs can efficiently mediate the DNA transfection and avoid apparent cytotoxicity in HeLa and COS7. The present gene delivery system offers a simple and flexible approach to fabricate microenvironment-specific branched gene vectors for gene therapy.

Cationic lipid nanosystems as carriers for nucleic acids

Solid lipid nanoparticles (SLNs) consisting of tristearin or tribehenin, and monoolein aqueous dispersions (MADs) consisting of glyceryl-monoolein have been studied as potential nanocarriers for nucleic acids. The cationic character of nanocarriers was obtained by adding cationic surfactants, such as diisobutylphenoxyethyl-dimethylbenzyl ammonium chloride (DEBDA) or PEG-15 Cocopolyamine (PCPA), to the lipid composition. The products were characterised in terms of size and morphology by Cryo-TEM and PCS. The charge properties were determined by measuring the zeta potential. Our experimental protocol enabled us to obtain homogeneous and stable cationic nanosystems within 3-6 months of production. Assessment of cytotoxicity on HepG2 cells by MTT assays indicated that MAD preparations were less toxic than SLN, and in general PCPA-containing formulations are less cytotoxic than DEBDA-containing ones. The formation of electrostatic complexes with salmon sperm or plasmid DNA, used as model nucleic acids, was evaluated by electrophoresis on agarose gel. The results confirmed that all the formulations studied are able to form the complex. Finally, we investigated the ability of SLN and MAD to deliver DNA into HepG2 cells, and to this purpose we exploited expression plasmids for green fluorescent protein or firefly luciferase. Although with reduced efficiency, the results showed that the produced nanocarriers are able to convey plasmids into cells. The data obtained encourage further study aimed at improving these new formulations and proposing them as novel in vitro transfection reagents with potential application to in vivo delivery of nucleic acids.

Strategies on the nuclear-targeted delivery of genes

To improve the nuclear-targeted delivery of non-viral vectors, extensive effort has been carried out on the development of smart vectors which could overcome multiple barriers. The nuclear envelope presents a major barrier to transgene delivery. Viruses are capable of crossing the nuclear envelope to efficiently deliver their genome into the nucleus through the specialized protein components. However, non-viral vectors are preferred over viral ones because of the safety concerns associated with the latter. Non-viral delivery systems have been designed to include various types of components to enable nuclear translocation at the periphery of the nucleus. This review summarizes the progress of research regarding nuclear transport mechanisms. "Smart" non-viral vectors that have been modified by peptides and other small molecules are able to facilitate the nuclear translocation and enhance the efficacy of gene expression. The resulting technology may also enhance delivery of other macromolecules to the nucleus.

The pharmacology of regenerative medicine

Regenerative medicine is a rapidly evolving multidisciplinary, translational research enterprise whose explicit purpose is to advance technologies for the repair and replacement of damaged cells, tissues, and organs. Scientific progress in the field has been steady and expectations for its robust clinical application continue to rise. The major thesis of this review is that the pharmacological sciences will contribute critically to the accelerated translational progress and clinical utility of regenerative medicine technologies. In 2007, we coined the phrase "regenerative pharmacology" to describe the enormous possibilities that could occur at the interface between pharmacology, regenerative medicine, and tissue engineering. The operational definition of regenerative pharmacology is "the application of pharmacological sciences to accelerate, optimize, and characterize (either in vitro or in vivo) the development, maturation, and function of bioengineered and regenerating tissues." As such, regenerative pharmacology seeks to cure disease through restoration of tissue/organ function. This strategy is distinct from standard pharmacotherapy, which is often limited to the amelioration of symptoms. Our goal here is to get pharmacologists more involved in this field of research by exposing them to the tools, opportunities, challenges, and interdisciplinary expertise that will be required to ensure awareness and galvanize involvement. To this end, we illustrate ways in which the pharmacological sciences can drive future innovations in regenerative medicine and tissue engineering and thus help to revolutionize the discovery of curative therapeutics. Hopefully, the broad foundational knowledge provided herein will spark sustained conversations among experts in diverse fields of scientific research to the benefit of all.

PEGylated peptide based reductive polycations as efficient nonviral gene vectors

To overcome the critical barriers in gene delivery, a series of reducible polycations (RPCs) based on low molecular weight (LMW) peptides, i.e. PolyHK6 H, PolyHK6 H-mPEG1 , PolyHK6 H-mPEG2 , and PolyHK6 H-mPEG3 , with different poly(ethylene glycol) (PEG) contents, are synthesized and evaluated as nonviral gene vectors. All the RPCs exhibit lower cytotoxicity compared with 25 kDa polyethyleneimine (PEI) and PEGylated PEI (PEI-mPEG: PEI-mPEG1 , PEI-mPEG2 , and PEI-mPEG3 ). PolyHK6 H-mPEG1 and PolyHK6 H-mPEG2 can bind and condense plasmid deoxyribonucleic acid (pDNA) efficiently with a particle size of about 200 nm. Moreover, they display much higher transfection efficiency than that of 25 kDa PEI especially in serum-supplemented medium. Moreover, PolyHK6 H-mPEG1 has equal transfection efficiency with PEI-mPEG1 which is optimal in the PEI-mPEG, but PolyHK6 H-mPEG1 exhibits significantly lower cytotoxicity than PEI-mPEG1 . This is attributed to the fact that inter-peptide disulfide bonds can increase the stability of RPCs/pDNA complexes in extracellular environment and thereafter cleave in cytoplasm to facilitate the release of pDNA in intracellular environment. The PEGylated RPCs demonstrate here improved intracellular gene transfer performance and will have great potential applications in vivo.

Gene delivery of PEI incorporating with functional block copolymer via non-covalent assembly strategy

A novel functional diblock polymer P(PEGMA-b-MAH) is prepared and incorporated to improve the gene delivery efficiency of poly(ethyleneimine) PEI via non-covalent assembly strategy. First, P(PEGMA-b-MAH) is prepared from l-methacrylamidohistidine methyl ester (MAH) by reversible addition fragmentation chain transfer polymerization, with poly[poly(ethylene glycol) methyl ether methacrylate] (P(PEGMA)) as the macroinitiator. Then P(PEGMA-b-MAH) is assembled with plasmid DNA (pDNA) and PEI (M(w)=10kDa) to form PEI/P(PEGMA-b-MAH)/pDNA ternary complexes. The agarose gel retardation assay shows that the presence of P(PEGMA-b-MAH) does not interfere with DNA condensation by the PEI. Dynamic light scattering tests show that PEI/P(PEGMA-b-MAH)/pDNA ternary complexes have excellent serum stability. In vitro transfection indicates that, compared to the P(PEGMA-b-MAH) free PEI-25k/pDNA binary complexes, PEI-10k/P(PEGMA-b-MAH)/pDNA ternary complexes have lower cytotoxicity and higher gene transfection efficiency, especially under serum conditions. The ternary complexes proposed here can inspire a new strategy for the development of gene and drug delivery vectors.

Multifunctional hyperbranched glycoconjugated polymers based on natural aminoglycosides

Multifunctional gene vectors with high transfection, low cytotoxicity, and good antitumor and antibacterial activities were prepared from natural aminoglycosides. Through the Michael-addition polymerization of gentamycin and N,N'-methylenebisacrylamide, cationic hyperbranched glycoconjugated polymers were synthesized, and their physical and chemical properties were analyzed by FTIR, (1)H NMR, (13)C NMR, GPC, ζ-potential, and acid-base titration techniques. The cytotoxicity of these hyperbranched glycoconjugated polycations was low because of the hydrolysis of degradable glycosidic and amide linkages in acid conditions. Owing to the presence of various primary, secondary, and tertiary amines in the polymers, hyperbranched glycoconjugated polymers showed high buffering capacity and strong DNA condensation ability, resulting in the high transfection efficiency. In the meantime, due to the introduction of natural aminoglycosides into the polymeric backbone, the resultant hyperbranched glycoconjugated polymers inhibited the growth of cancer cells and bacteria efficiently. Combining the gene transfection, antitumor, and antibacterial abilities together, the multifunctional hyperbranched glycoconjugated polymers based on natural aminoglycosides may play an important role in protecting cancer patients from bacterial infections.

Design of multifunctional non-viral gene vectors to overcome physiological barriers: dilemmas and strategies

Gene-based therapeutics hold great promise for medical advancement and have been used to treat various human diseases with mixed success. However, their therapeutic application in vivo is limited due largely to several physiological barriers. The design of non-viral gene vectors with the ability to overcome delivery obstacles is currently under extensive investigation. These efforts have placed an emphasis on the development of multifunctional vectors able to execute multiple tasks to simultaneously overcome both extracellular and intracellular obstacles. However, the assembly of these different functionalities into a single system to create multifunctional gene vectors faces many conflicts that largely limit the safe and efficient application of lipoplexes and polyplexes in a systemic delivery. In the review, we have described the dilemmas inherent in the design of a viable, non-viral gene vector equipped with multiple functionalities. The strategies directed towards individual delivery barriers are first summarized, followed by a focus on the design of so-called smart multifunctional vectors with the capability to overcome the delivery difficulties of gene medicines, including the so-called the "polycation dilemma", the "PEG dilemma" and the "package and release dilemma".

Optimize nuclear localization and intra-nucleus disassociation of the exogene for facilitating transfection efficacy of the chitosan

Previously, we had reported improving transfection efficiency of the chitosan-plasmid DNA (CS/pDNA)complex via enhancing intracellular unpacking of the exogene by the utilization of phosphorylatable short peptide conjugated chitosan (pSP-CS). In this article, we addressed a novel strategy of nucleus localization signal linked nucleic kinase substrate short peptide (NNS) modification for further optimization of the transfection efficiency. NNS, consisting of "PKKRKVREEAIKFSEEQRFRR", contained a SV40 nucleus localization signal and a potentially phosphorylatable serine residue. The short peptide could be selectively phosphorylated in the nucleus in various mammalian cells. This phosphorylatable NNS (pNNS) was conjugated to chitosan and combined with Cy3 fluorescence labeled plasmid DNA to form a pNNS-CS/pDNA complex. In vitro phosphorylation and DNA releasing assays verified that pNNS could be effectively and selectively phosphorylated by nucleic lysate, hence promoting pDNA unpacking from the complex. Thereafter, C2C12 myoblast cells were transfected. Nuclear localization of the pDNA was represented by the fluorescence in the nucleus and transfection efficiency was determined by the expression of the luciferase reporter gene, which is carried by the plasmid DNA. The results revealed that, compared with lipofactamine2000 and the previously reported pSP-CS, pNNS-CS could transport more pDNA into the nucleus and intensively augment luciferase reporter gene expression. In conclusion, nucleus localization and unpacking from the delivery vector are both critical factors in influencing exogene expression, and pNNS modification is valuable in improving transfection efficacy of the chitosan.

The mechanism of selective transfection mediated by pentablock copolymers; part I: investigation of cellular uptake

Poly(diethylaminoethylmethacrylate) (PDEAEM) and Pluronic F127 based pentablock copolymer vectors with the ability to transfect cancer cells selectively over normal cells in in vitro cultures were developed, as described in a previous report. Understanding the mechanism of this selectivity will enable better polymeric vectors to be designed, with inherent selectivity for specific cell types based on intracellular differences and not on the use of targeting ligands, which have shown variable success, depending on the system. It is assumed that the selectivity was due to different intracellular barriers to transfection in the different cell types. Part I focuses on investigating whether cellular entry is one of the barriers to transfection, through conjugation of epidermal growth factor (EGF) to the pentablock copolymer vector. Results indicate that EGF conjugation increased transfection efficiency the most when conjugated to the outer surface of polyplexes, with minimal disruption to DNA packaging and maximal accessibility to receptors. The overall resulting enhancement in transfection, however, was a moderate three- to five-fold increase compared with the condition with no EGF involved, implying that the addition of EGF fails to overcome the intracellular barrier to transfection, which probably involves some step other than cellular uptake in pentablock copolymer system. Therefore, the differences observed in the selectivity of transfection between cancer and normal cell lines is probably not controlled by differences in cellular entry, and the intracellular barriers to transfection in this system are likely to be endosomal escape or nuclear entry, as investigated in Part II, the companion paper to this work.

Sensing polymer/DNA polyplex dissociation using quantum dot fluorophores

We characterized the dissociation of polymer/DNA polyplexes designed for gene delivery using water-soluble quantum dots (QDs). A pH-responsive pentablock copolymer was designed to form stable complexes with plasmid DNA via tertiary amine segments. Dissociation of the polyplex was induced using chloroquine where the efficiency of this process was sensed through changes in QD fluorescence. We found that increasing concentrations of pentablock copolymer and DNA led to quenching of QD fluorescence, while chloroquine alone had no measurable effect. The mechanism of quenching was elucidated by modeling the process as the combination of static and dynamic quenching from the pentablock copolymer and DNA, as well as self-quenching due the bridging of QDs. Tertiary amine homopolymers were also used to study the effect of chain length on quenching. Overall, these QDs were found to be highly effective at monitoring the dissociation of pentablock copolymer/DNA polyplexes in vitro and may have potential for studying the release of DNA within cells.

Intracellular delivery of nanoparticles with CPPs

Cell-penetrating peptides (CPPs), in particular TATp, have been widely used for intracellular delivery of various cargoes, both in vitro and in vivo. Modifications of nanoparticles with CPPs require either covalent or noncovalent approach. Here we describe various methods to attach CPP, such as TATp to surface of nanocarriers (such as liposomes and micelles), loading with drug or DNA and characterization of same for in vitro and in vivo applications. Due to nonselectivity of CPPs and wide distribution in nontarget areas, method for preparation of "smart" nanocarrier with hidden TATp function is also described.

Efficient intracellular gene delivery using the formulation composed of poly (L-glutamic acid) grafted polyethylenimine and histone

PURPOSE

Inefficient endosomal escape and poor nuclear import are thought to contribute to low gene transfer efficiency of polycations. To overcome these drawbacks, we prepared multiple gene delivery formulations including low cytotoxic polycation, histone containing NLSs and chloroquine as the endosomolytic agent.

METHODS

Comb-shaped poly (L-glutamic acid) grafted low-molecular-weight polyethylenimine (PLGE) copolymer was synthesized by aminolysis of poly-γ-benzyl-L-glutamate using low-molecular-weight polyethylenimine (800 Da). The formation of DNA/histone/PLGE terplex was observed by atomic force microscope and gel retardation assay. The particle size and zeta potential of DNA complexes with varying content of histone were also measured to confirm the terplex formation. Cytotoxicity of vectors was assayed by MTT. Multiple gene delivery formulations were optimized to their best transfection efficiency that was monitored by fluorescence microscope and flow cytometry. In vivo gene delivery of the optimal formulation was evaluated by the GFP-expression levels in drosophila melanogaster.

RESULTS

The DNA/histone/PLGE terplex was successfully formed. The PLGE and histone together condensed DNA into small, discrete particles (less than 200 nm in diameter) in isotonic solution. Cytotoxicity of PLGE and histone were much lower than that of PEI 25 K. Either histone or chloroquine contributed to enhancing the levels of transfection activity of PLGE polymer. However, chloroquine and histone did not show a synergistic effect on the improvement of transfection efficiency. The optimal formulation was the DNA/histone/PLGE terplex at the N/P ratio of 15 and histone/ DNA weight ratio of 0.8. Compared with Lipofectamine 2000 and PEI 25 K, the optimal formulation showed significantly increased levels of GFP-expression both in vitro and in vivo.

CONCLUSION

This formulation provided a versatile approach for preparing high efficiency of the polycation-based gene vectors. It also reinforced the finding of earlier studies that nuclear import and endosomal escape were rate-limiting steps for nonviral gene delivery.

Multifunctional peptide-PEG intercalating conjugates: programmatic of gene delivery to the blood-brain barrier

PURPOSE

To enhance transfection efficacy of pDNA through the application of multifunctional peptide-PEG-tris-acridine conjugates (pPAC) and the formation of biodegradable core-shell polyplexes for gene delivery to the blood-brain barrier (BBB).

METHODS

pPAC-mediated transfection was compositionally optimized in mouse BBB cells (bEnd.3). Cellular uptake and trafficking, and brain accumulation of pDNA was evaluated by fluorescent imaging and histochemistry. We constructed anti-MRP4 siRNA-producing vectors and evaluated the efficacy of MRP4 down-regulation of MRP4 by Western blot and qPCR, and its effect on the uptake of (3)H-AZT, an MRP4 substrate.

RESULTS

A core-shell gene delivery system (GDS) was assembled from pDNA and pPAC, carrying multifunctional peptides with NLS, TAT, and brain-specific BH, or ApoE sequences, and biodegradable pLPEI polyamine. This GDS demonstrated better cellular and nuclear accumulation, and a 25-fold higher transfection efficacy in slow-dividing bEnd.3 cells compared to ExGen500. Inclusion of brain-targeting pPAC enhanced in vivo accumulation of functional pDNA in brain capillaries. Treatment by encapsulated anti-MRP4 siRNA-producing pDNA caused transient down-regulation of MRP4, and, after intravenous injection in Balb/c mice, enhanced AZT uptake in the brain by 230-270%.

CONCLUSIONS

The pPAC represent novel efficient components of GDS that could find various gene therapy applications, including genetic modulation of the BBB.

Advancing nonviral gene delivery: lipid- and surfactant-based nanoparticle design strategies

Gene therapy is a technique utilized to treat diseases caused by missing, defective or overexpressing genes. Although viral vectors transfect cells efficiently, risks associated with their use limit their clinical applications. Nonviral delivery systems are safer, easier to manufacture, more versatile and cost effective. However, their transfection efficiency lags behind that of viral vectors. Many groups have dedicated considerable effort to improve the efficiency of nonviral gene delivery systems and are investigating complexes composed of DNA and soft materials such as lipids, polymers, peptides, dendrimers and gemini surfactants. The bottom-up approach in the design of these nanoparticles combines components essential for high levels of transfection, biocompatibility and tissue-targeting ability. This article provides an overview of the strategies employed to improve in vitro and in vivo transfection, focusing on the use of cationic lipids and surfactants as building blocks for nonviral gene delivery systems.

Effect of serum on transfection by polyethylenimine/virus-like particle hybrid gene delivery vectors

PURPOSE

Murine leukemia virus-like particles (M-VLP) complexed with polymers to promote cellular uptake and endosomal escape represent a new class of effective gene delivery vectors. Building upon recent studies of viral-synthetic hybrid vectors, we report the effects of serum on the formation, activity and stability of PEI/M-VLP complexes.

METHODS

M-VLP were produced by cells grown in serum-supplemented media (M-VLP-S), serum-free media (M-VLP-SF) or serum-free Opti-MEM® I (M-VLP-OM). PEI/M-VLP stoichiometry was varied to investigate complex formation and optimal transfection conditions. The effects of prolonged storage, freeze-thaw cycles, and ultracentrifugation of M-VLP on the stability of vector transduction efficiency were also observed.

RESULTS

M-VLP-S required more PEI to form infective complexes than M-VLP-SF and M-VLP-OM. The stoichiometry of PEI/M-VLP-S was dependent on total PEI concentration (7-8 μg/100 μL M-VLP supernatant), while optimal infectivity of PEI/M-VLP-SF and PEI/M-VLP-OM depended on PEI/M-VLP ratios (12-17 μg and 10-14 μg PEI/10(9) M-VLP, respectively). PEI/M-VLP-SF and PEI/M-VLP-OM complexes were significantly more efficient than PEI/M-VLP-S. Stability of the hybrid vectors was not significantly affected by serum.

CONCLUSIONS

PEI/M-VLP complexes exhibiting increased efficiency were constructed by producing M-VLP in serum-free media. M-VLP could be stored by freezing or refrigeration and concentrated by ultracentrifugation without unacceptable loss of infectivity.

Polymeric nanoparticles containing conjugated phospholipase A2 for nonviral gene delivery

Polyethylenimine (PEI) was conjugated to phospholipase A(2) (PLA(2)) in an effort to improve transfection efficiency. PLA(2) was conjugated to PEI using EDC as a coupling reagent. The activity of enzyme in the conjugate was measured. DNA condensation ability of the conjugate to polymer was determined. The resultant nanoparticles were characterized by dynamic and electrophoretic light scattering. Two reporter genes were used to evaluate transfection efficiency in human embryonic kidney (HEK293) and human hepatoma (HepG2) cell lines. Conjugate was shown to retain PLA(2) activity and its ability to condense plasmid DNA, resulting in nanoparticles of a similar size to native PEI. The results demonstrated at N/P ratios of 15 and 20 showed 13- and 8-fold increase in transfection efficiency, respectively, compared to the maximum transfection efficiency of PEI (N/P ratio of 5) in the whole range of N/P ratios tested, from 5 to 60 in HepG2 cells. Toxicity studies in HepG2 cells showed uncomplexed conjugate had similar toxicity as PEI, and when complexed with DNA the conjugate had a significantly reduced toxicity. The results clearly indicate the potential for this approach to improve efficiencies of nonviral gene delivery vectors.

SiRNA-loaded multi-shell nanoparticles incorporated into a multilayered film as a reservoir for gene silencing

In this study, we presented a new type of coating based on polyelectrolyte multilayers containing sequentially adsorbed active shRNA calcium phosphate nanoparticles for locally defined and temporarily variable gene silencing. Therefore, we investigated multi-shell calcium phosphate-shRNA nanoparticles embedded into a polyelectrolyte multilayer for gene silencing. As model system, we synthesized triple-shell calcium phosphate-shRNA nanoparticles (NP) and prepared polyelectrolyte multilayers films made of nanoparticles and poly-(L-lysine) (PLL). The biological activities of these polyelectrolyte multilayers films were tested by the production of osteopontin and osteocalcin in the human osteoblasts (HOb) which were cultivated on the PEM films. This new strategy can be used to efficiently control the bone formation and could be applicable in tissue engineering.