Influence of the polyanion on the physico-chemical properties and biological activities of polyanion/DNA/polycation ternary polyplexes

A cationic cyclodextrin derivative-lipid hybrid nanoparticles for gene delivery effectively promotes stability and transfection efficiency

Genetic medicines hold great promise for treatment of a number of diseases, however, the development of effective gene delivery carrier is still a challenge. The commonly used gene carrier liposomes and cationic polymers have limited their clinical application due to their respective disadvantages. Lipid-polymer hybrid nanoparticles (LHNPs) are novel drug delivery system which exhibit complementary characteristics of both polymeric nanoparticles and liposomes. In this account, we developed the α-cyclodextrin conjugated generation-2 polyamidoamine dendrimers-lipids hybrid nanoparticles (CDG2-LHNPs) for gene delivery. The pDNA/CDG2-LHNPs was stable during 15 days storage period both at 4 °C, 25 °C and 37 °C, whereas the particle size of pDNA/CDG2 and pDNA/liposomes dramatically increased after storage at 4 °C for 8 h. CDG2-LHNPs showed significantly superior transfection efficiencies compared to either CDG2 or liposomes. The mechanism of high transfection efficiency of pDNA/CDG2-LHNPs was further explored using pharmacological inhibitors chlorpromazine, filipin and cytochalasion D. The result demonstrated that cell uptake of pDNA/CDG2-LHNPs was mediated by clathrin-mediated endocytosis (CME), caveolae-mediated endocytosis (CvME) and macropinocytosis together. pDNA/CDG2-LHNPs were more likely be taken up by cells through C_VME, which avoided lysosomal degradation to a large extent. Moreover, the liposome component of pDNA/CDG2-LHNPs increased its cell uptake efficiency, and the CDG2 polymer component increased its proton buffer capacity, so the hybrid nanoparticles taken up by CME could also successfully escape from the lysosome. This CDG2-LHNPs with stability and high transfection efficiency overcome the shortcomings of liposomes and polymers applied separately, and has great potential for gene drug delivery.

Reversing the surface charge of MSC-derived small extracellular vesicles by εPL-PEG-DSPE for enhanced osteoarthritis treatment

Mesenchymal stem cell-derived small extracellular vesicles (MSC-sEVs) possess a great therapeutical potential for osteoarthritis (OA) treatment. However, the steric and electrostatic hindrance of cartilage matrix leads to very limited distribution of MSC-sEVs in cartilage and low bioavailability of MSC-sEVs after intra-articular injection. To overcome this, a strategy to reverse the surface charge of MSC-sEVs by modifying the MSC-sEVs with a novel cationic amphiphilic macromolecule namely ε-polylysine-polyethylene-distearyl phosphatidylethanolamine (PPD) was developed in this study. Through incubation with 100 μg/ml PPD, positively charged MSC-sEVs (PPD-sEVs) were obtained, and the modification process showed nearly no disturbance to the integrity and contents of sEVs and exhibited good stability under the interference of anionic macromolecules. A more effective cellular uptake and homeostasis modulation ability of PPD-sEVs than unmodified MSC-sEVs to chondrocytes was demonstrated. More importantly, PPD-sEVs demonstrated significantly enhanced cartilage uptake, cartilage penetration, and joint retention capacity as compared to MSC-sEVs. Intra-articular injection of PPD-sEVs into a mouse OA model showed significantly improved bioavailability than MSC-sEVs, which resulted in enhanced therapeutic efficacy with reduced injection frequency. In general, this study provides a facile and effective strategy to improve the intra-articular bioavailability of MSC-sEVs and has a great potential to accelerate the clinical practice of MSC-sEVs based OA therapy.

Poly-γ-glutamic acid-based GGT-targeting and surface camouflage strategy for improving cervical cancer gene therapy

A γ-PGA-based GGT-targeting and surface camouflage strategy for constructing a ternary layer-by-layer self-assembly gene delivery system.

An Electrostatically Self-Assembled Ternary Nanocomplex as a Non-Viral Vector for the Delivery of Plasmid DNA into Human Adipose-Derived Stem Cells

In this study, we developed electrostatically self-assembled ternary nanocomplexes as a safe and effective non-viral vector for the delivery of plasmid DNA (pDNA) into human adipose-derived stem cells (hASCs). Although polyethylenimine (PEI) polymers initially showed excellent performance as gene delivery carriers, their broad use has been limited by cytotoxicity resulting from their strong positive charge. To reduce the cytotoxicity, we utilized anionic hyaluronic acid (HA) as a corona layer material for pDNA/PEI binary nanocomplexes. HA was also introduced to increase the targeting efficiency of pDNA/PEI nanocomplexes because HA has can bind CD44 that is highly expressed on the surface of hASCs. We confirmed that the addition of HA changed the surface charge of pDNA/PEI nanocomplexes from positive to negative. The pDNA/PEI/HA ternary nanocomplexes showed high transfection efficiency and low cytotoxicity compared with commercially available products. When hASCs were pretreated with HA to passivate CD44, the transfection efficiency of pDNA/PEI/HA nanocomplexes was significantly reduced. These results suggest that HA that can act as a targeting ligand to CD44 contributed to the improved transfection of pDNA into hASCs. Our novel pDNA/PEI/HA nanocomplexes may be used as an effective non-viral pDNA delivery system for hASCs.

Entry of PIP3-containing polyplexes into MDCK epithelial cells by local apical-basal polarity reversal

The polarized architecture of epithelium presents a barrier to therapeutic drug/gene carriers, which is mainly due to a limited (apical) internalization of the carrier systems. The bacterium Pseudomonas aeruginosa invades epithelial cells by inducing production of apical phosphatidylinositol-3, 4, 5-triphosphate (PIP3), which results in the recruitment of basolateral receptors to the apical membrane. Since basolateral receptors are known receptors for gene delivery vectors, apical PIP3 may improve the internalization of such vectors into epithelial cells. PIP3 and nucleic acids were complexed by the cationic polymer polyethylenimine (PEI), forming PEI/PIP3 polyplexes. PEI/PIP3 polyplexes showed enhanced internalization compared to PEI polyplexes in polarized MDCK cells, while basolateral receptors were found to redistribute and colocalize with PEI/PIP3 polyplexes at the apical membrane. Following their uptake via endocytosis, PEI/PIP3 polyplexes showed efficient endosomal escape. The effectiveness of the PIP3-containing delivery system to generate a physiological effect was demonstrated by an essentially complete knock down of GFP expression in 30% of GFP-expressing MDCK cells following anti-GFP siRNA delivery. Here, we demonstrate that polyplexes can be successfully modified to mimic epithelial entry mechanisms used by Pseudomonas aeruginosa. These findings encourage the development of pathogen-inspired drug delivery systems to improve drug/gene delivery into and across tissue barriers.

Self-assembled ternary complexes stabilized with hyaluronic acid-green tea catechin conjugates for targeted gene delivery

Nanosized polyelectrolyte complexes are attractive delivery vehicles for the transfer of therapeutic genes to diseased cells. Here we report the application of self-assembled ternary complexes constructed with plasmid DNA, branched polyethylenimine and hyaluronic acid-green tea catechin conjugates for targeted gene delivery. These conjugates not only stabilize plasmid DNA/polyethylenimine complexes via the strong DNA-binding affinity of green tea catechin, but also facilitate their transport into CD44-overexpressing cells via receptor-mediated endocytosis. The hydrodynamic size, surface charge and physical stability of the complexes are characterized. We demonstrate that the stabilized ternary complexes display enhanced resistance to nuclease attack and polyanion-induced dissociation. Moreover, the ternary complexes can efficiently transfect the difficult-to-transfect HCT-116 colon cancer cell line even in serum-supplemented media due to their enhanced stability and CD44-targeting ability. Confocal microscopic analysis demonstrates that the stabilized ternary complexes are able to promote the nuclear transport of plasmid DNA more effectively than binary complexes and hyaluronic acid-coated ternary complexes. The present study suggests that the ternary complexes stabilized with hyaluronic acid-green tea catechin conjugates can be widely utilized for CD44-targeted delivery of nucleic acid-based therapeutics.

Diol glycidyl ether-bridged low molecular weight PEI as potential gene delivery vehicles

PEI 600-based polymers were synthesized via ring-opening polymerization and exhibited much better transfection efficiency and biocompatibility than PEI 25 kDa.

Efficient gene delivery system mediated by cis-aconitate-modified chitosan-g-stearic acid micelles

Cis-aconitate-modified chitosan-g-stearic acid (CA-CSO-SA) micelles were synthesized in this study to improve the gene transfection efficiency of chitosan-g-stearic acid (CSO-SA). The CA-CSO-SA micelles had a similar size, critical micelle concentration, and morphology, but their zeta potential and cytotoxicity were reduced compared with CSO-SA micelles. After modification with cis-aconitate, the CA-CSO-SA micelles could also compact plasmid DNA (pDNA) to form nanocomplexes. However, the DNA binding ability of CA-CSO-SA was slightly reduced compared with that of CSO-SA. The transfection efficiency mediated by CA-CSO-SA/pDNA against HEK-293 cells reached up to 37%, and was much higher than that of CSO-SA/pDNA (16%). Although the cis-aconitate modification reduced cellular uptake kinetics in the initial stages, the total amount of cellular uptake tended to be the same after 24 hours of incubation. An endocytosis inhibition experiment showed that the internalization mechanism of CA-CSO-SA/pDNA in HEK-293 cells was mainly via clathrin-mediated endocytosis, as well as caveolae-mediated endocytosis and macropinocytosis. Observation of intracellular trafficking indicated that the CSO-SA/pDNA complexes were trapped in endolysosomes, but CA-CSO-SA/pDNA was more widely distributed in the cytosol. This study suggests that modification with cis-aconitate improves the transfection efficiency of CSO-SA/pDNA.

Assessment of cholesterol-derived ionic copolymers as potential vectors for gene delivery

A library of cholesterol-derived ionic copolymers were previously synthesized via reversible addition-fragmentation chain transfer (RAFT) polymerization as 'smart' gene delivery vehicles that hold diverse surface charges. Polyplex systems formed with anionic poly(methacrylic acid-co-cholesteryl methacrylate) (P(MAA-co-CMA)) and cationic poly(dimethylamino ethyl methacrylate-co-cholesteryl methacrylate) (Q-P(DMAEMA-co-CMA)) copolymer series were evaluated for their therapeutic efficiency. Cell viability assays, conducted on SHEP, HepG2, H460, and MRC5 cell lines, revealed that alterations in the copolymer composition (CMA mol %) affected the cytotoxicity profile. Increasing the number of cholesterol moieties in Q-P(DMAEMA-co-CMA) copolymers reduced the overall toxicity (in H460 and HepG2 cells) while P(MAA-co-CMA) series displayed no significant toxicity regardless of the CMA content. Agarose gel electrophoresis was employed to investigate the formation of stable polyplexes and determine their complete conjugation ratios. P(MAA-co-CMA) copolymer series were conjugated to DNA through a cationic linker, oligolysine, while Q-P(DMAEMA-co-CMA)-siRNA complexes were readily formed via electrostatic interactions at conjugation ratios beginning from 6:1:1 (oligolysine-P(MAA-co-CMA)-DNA) and 20:1 (Q-P(DMAEMA-co-CMA)-siRNA), respectively. The hydrodynamic diameter, ζ potential and complex stability of the polyplexes were evaluated in accordance to complexation ratios and copolymer composition by dynamic light scattering (DLS). The therapeutic efficiency of the conjugates was assessed in SHEP cells via transfection and imaging assays using RT-qPCR, Western blotting, flow cytometry, and confocal microscopy. DNA transfection studies revealed P(MAA-co-CMA)-oligolysine-DNA ternary complexes to be ineffective transfection vehicles that mostly adhere to the cell surface as opposed to internalizing and partaking in endosomal disrupting activity. The transfection efficiency of Q-P(DMAEMA-co-CMA)-GFP siRNA complexes were found to be polymer composition and N/P ratio dependent, with Q-2% CMA-GFP siRNA polyplexes at N/P ratio 20:1 showing the highest gene suppression in GFP expressing SHEP cells. Cellular internalization studies suggested that Q-P(DMAEMA-co-CMA)-siRNA conjugates efficiently escaped the endolysosomal pathway and released siRNA into the cytoplasm. The gene delivery profile, reported herein, illuminates the positive and negative attributes of each therapeutic design and strongly suggests Q-P(DMAEMA-co-CMA)-siRNA particles are extremely promising candidates for in vivo applications of siRNA therapy.

A photo-degradable gene delivery system for enhanced nuclear gene transcription

There currently exists a significant gap in our understanding of how the detailed chemical characteristics of polycation gene carriers influence their delivery performances in overcoming an important cellular-level transport barrier, i.e., intranuclear gene transcription. In this study, a UV-degradable gene carrier material (ENE4-1) was synthesized by crosslinking low molecular weight branched polyethylenimine (bPEI-2k) molecules using UV-cleavable o-nitrobenzyl urethane (NBU) as the linker molecule. NBU degrades upon exposure to mild UV irradiation. Therefore, this UV-degradable carrier allows us to control the chemical characteristics of the polymer/DNA complex (polyplex) particles at desired locations within the intracellular environment. By using this photolytic DNA carrier, we found that the exact timing of the UV degradation significantly influences the gene transfection efficiencies of ENE4-1/DNA(pGL2) polyplexes in HeLa cells. Interestingly, even if the polyplexes were UV-degraded at different intracellular locations/times, their nuclear entry efficiency was not influenced by the location/timing of UV degradation. The UV treatment did not influence the size or binding strength of the polyplexes. However, we confirmed that the degradation of the carrier molecules impacts the chemical characteristics of the polyplexes (it produces carbamic acid and nitrosobenzyl aldehyde groups on ENE4-1). We believe that these anionic acid groups enhance the interaction of the polyplexes with nuclear transcription proteins and thus the final gene expression levels; this effect was found to occur, even though UV irradiation itself has a general effect of reducing transfection efficiencies. Excess (uncomplexed) ENE4-1 polymers appear to not play any role in the UV-enhanced gene transcription phenomenon.

Enhanced cellular transfection by ternary non-viral gene vectors coupled with adeno-associated virus-derived peptides

The establishment of efficient and safe gene delivery systems is crucial for biomedical applications. To address this objective, novel, ternary hybrid gene vectors are designed with viral capsid peptides in non-viral gene carriers. The viral peptide, TQVGQKT, is coupled with a membrane active peptide, LK15. Which acts as a linker to tag peptide with plasmid DNA. Additionally, polyethylenimine (PEI) is employed to condense the complexes further, thereby forming ternary DNA/TQVGQKT-LK15/PEI complexes. The ternary complexes result in rapid internalization leading to significantly enhanced cellular transfection. The new moiety, TQVGQKT, as well as enhanced cellular transfection, will certainly provide crucial insights for the design of novel non-viral gene carriers with efficient and safe properties.

Gelatin coating to stabilize the transfection ability of nucleic acid polyplexes

Amphiphilic polymers are effective in complexing and delivering therapeutic nucleic acids, such as plasmid DNA (pDNA) and short interfering RNA (siRNA). However, long-term stability of the complexes is not desirable, as it may have an impact on the transfection efficiency in vivo. To develop a method to preserve complex stability we first showed that pDNA complexes formed with the amphiphilic polymer linoleic acid-substituted polyethylenimine (PEI-LA) and incubated at 37°C lost ~90% of their transfection efficiency after only 24h of complex formation. Polyethyleneglycol modification of complexes to control the increase in complex size and incubation in scaffolds used for implantation did not preserve the transfection ability of the complexes. Among a variety of approaches explored, gelatin coating of complexes was found to be the best at maintaining the original transfection efficiency. Mechanistic studies suggested that improved complex uptake, not size stability, was responsible for retention of the transfection efficiency. Similarly to the results with pDNA, gelatin coating also prevented the decreases in uptake and silencing efficiency of siRNA complexes observed following incubation at 37°C. Gelatin-stabilized complexes were, furthermore, effective in vivo and led to subcutaneous transgene expression with a low pDNA dose that was otherwise ineffective. We conclude that a simple gelatin coating approach offers an efficient means to preserve the transfection efficiency of polyplexes.

Salt-induced stability and serum-resistance of polyglutamate polyelectrolyte brushes/nuclear factor-κB p65 siRNA Polyplex enhance the apoptosis and efficacy of doxorubicin

Short interfering RNAs (siRNAs) as chemotherapeutic RNAi agents hold great promise for a significant improvement in cancer therapy. Despite the promise, effective transport of siRNA with minimal side effects remains a challenge. The common problem associated with the low delivery efficiencies of current polycation-based gene delivery systems is their low stability in the presence of salt and serum. In the present study we developed the polyglutamate derivatives (PGS) polyelectrolyte brushes for NF-κB p65 siRNA delivery. The PGS polyelectrolyte brushes/siRNA polyplex was colloidally stable (150 nm diameter) in physiological saline (150 mM NaCl), likely due to the osmotic brushes of PGS. The size-controlled siRNA/PGS polyplex also showed the serum resistance resulting in their efficient cellular uptake was not negatively influenced by the presence of serum. The endothermic profile of ITC, their low values of Gibbs free energy and binding constants Kb under salt conditions provided the direct evidence that PGS polyelectrolyte brushes had a much lower binding affinity for serum proteins, compared with PEI 25KDa. PGS polyelectrolyte brushes delivering NF-κB p65 siRNA achieved efficient down-regulation of NF-κB p65 protein in HeLa cells. The NF-κB p65 down-regulation mediated by PGS polyelectrolyte brushes was more significant than PEI 25KDa and comparable to Lipofectamine 2000. Furthermore, the combination treatment with PGS polyelectrolyte brushes/NF-κB p65 siRNA polyplex and doxorubicin demonstrated synergistic apoptotic and cytotoxic effects on HeLa cancer cells. The high stability in physiological saline and salt-induced serum resistance of PGS polyelectrolyte brushes/siRNA polyplex has potential applications together with standard chemotherapies such as doxorubicin to be a viable method to improve the clinical outcomes in cancer therapies.