Acid-degradable cationic methacrylamide polymerized in the presence of plasmid DNA as tunable non-viral gene carrier

Chemically Tuned Intracellular Gene Delivery by Core-Shell Nanoparticles: Effects of Proton Buffering, Acid Degradability, and Membrane Disruption

Nanoparticles consisting of a condensed nucleic acid core surrounded by protective layers which aid to overcome extracellular and intracellular hurdles to gene delivery (i. e., core-shell nanoparticles, CSNPs) synthetically mimic viruses. The outer shells shield the core and are particularly designed to enable facilitated release of the gene payload into the cytoplasm, the major limiting step in intracellular gene delivery. The hypothetical proton sponge effect and degradability in response to a stimulus (i. e., mildly acidic pH in the endosome) are two prevailing, although contested, principles in designing effective carriers for intracellular gene delivery via endosomal escape. Utilizing the highly flexible chemical-tuning of the polymeric shell via surface-initiated photo-polymerization of the various monomers at different molecular ratios, the effects of proton buffering capacity, acid-degradability, and endosomal membrane-lysis property on intracellular delivery of plasmid DNA by CSNPs were investigated. This study demonstrated the equivalently critical roles of proton buffering and acid-degradability in achieving efficient intracellular gene delivery, independent of cellular uptake. Extended proton buffering resulted in further improved transfection as long as the core structure was not compromised. The results of the study present a promising synthetic strategy to the development of an efficient, chemically-tunable gene delivery carrier.

Polycation-Mediated Transfection: Mechanisms of Internalization and Intracellular Trafficking

Polyplex-mediated gene transfection is now in its' fourth decade of serious research, but the promise of polyplex-mediated gene therapy has yet to fully materialize. Only approximately one in a million applied plasmids actually expresses. A large part of this is due to an incomplete understanding of the mechanism of polyplex transfection. There is an assumption that internalization must follow a canonical mechanism of receptor mediated endocytosis. Herein, we present arguments that untargeted (and most targeted) polyplexes do not utilize these routes. By incorporating knowledge of syndecan-polyplex interactions, we can show that syndecans are the "target" for polyplexes. Further, it is known that free polycations (which disrupt cell-membranes by acid-catalyzed hydrolysis of phospholipid esters) are necessary for (untargeted) endocytosis. This can be incorporated into the model to produce a novel mechanism of endocytosis, which fits the observed phenomenology. After membrane translocation, polyplex containing vesicles reach the endosome after diffusing through the actin mesh below the cell membrane. From there, they are acidified and trafficked toward the lysosome. Some polyplexes are capable of escaping the endosome and unpacking, while others are not. Herein, it is argued that for some polycations, as acidification proceeds the polyplexes excluding free polycations, which disrupt the endosomal membrane by acid-catalyzed hydrolysis, allowing the polyplex to escape. The polyplex's internal charge ratio is now insufficient for stability and it releases plasmids which diffuse to the nucleus. A small proportion of these plasmids diffuse through the nuclear pore complex (NPC), with aggregation being the major cause of loss. Those plasmids that have diffused through the NPC will also aggregate, and this appears to be the reason such a small proportion of nuclear plasmids express mRNA. Thus, the structural features which promote unpacking in the endosome and allow for endosomal escape can be determined, and better polycations can be designed.

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.

Optimizing synthetic nucleic acid and protein nanocarriers: The chemical evolution approach

Optimizing synthetic nanocarriers is like searching for a needle in a haystack. How to find the most suitable carrier for intracellular delivery of a specified macromolecular nanoagent for a given disease target location? Here, we review different synthetic 'chemical evolution' strategies that have been pursued. Libraries of nanocarriers have been generated either by unbiased combinatorial chemistry or by variation and novel combination of known functional delivery elements. As in natural evolution, definition of nanocarriers as sequences, as barcode or design principle, may fuel chemical evolution. Screening in appropriate test system may not only provide delivery candidates, but also a refined understanding of cellular delivery including novel, unpredictable mechanisms. Combined with rational design and computational algorithms, candidates can be further optimized in subsequent evolution cycles into nanocarriers with improved safety and efficacy. Optimization of nanocarriers differs for various cargos, as illustrated for plasmid DNA, siRNA, mRNA, proteins, or genome-editing nucleases.

Multifunctional Poly(amine-co-ester-co-ortho ester) for Efficient and Safe Gene Delivery

Cationic polymers are used for non-viral gene delivery, but current materials lack the functionality to address the multiple barriers involved in gene delivery. Here we describe the rational design and synthesis of a new family of quaterpolymers with unprecedented multifunctionality: acid sensitivity, low cationic charge, high hydrophobicity, and biodegradability, all of which are essential for efficient and safe gene delivery. The polymers were synthesized via lipase-catalyzed polymerization of ortho ester diester, lactone, dialkyl diester, and amino diol monomers. Polymers containing ortho ester groups exhibited acid-sensitive degradation at endosomal pH (4~5), facilitated efficient endosomal escape and unpackaging of the genes, and were efficient in delivering genetic materials to HEK293 cells, human glioma cells, primary mouse melanoma cells, and human umbilical vein endothelial cells (HUVECs). We also developed a highly efficient lyophilized formulation of the nanoparticles, which could be stored for a month without loss of efficiency.

Efficient and Non-Toxic Biological Response Carrier Delivering TNF-α shRNA for Gene Silencing in a Murine Model of Rheumatoid Arthritis

Small interfering RNA (siRNA) is an effective and specific method for silencing genes. However, an efficient and non-toxic carrier is needed to deliver the siRNA into the target cells. Tumor necrosis factor α (TNF-α) plays a central role in the occurrence and progression of rheumatoid arthritis (RA). In this study, we pre-synthetized a degradable cationic polymer (PDAPEI) from 2,6-pyridinedicarboxaldehyde and low-molecular-weight polyethyleneimine (PEI, Mw = 1.8 kDa) as a gene vector for the delivery of TNF-α shRNA. The PDAPEI/pDNA complex showed a suitable particle size and stable zeta potential for transfection. In vitro study of the PDAPEI/pDNA complex revealed a lower cytotoxicity and higher transfection efficiency when transfecting TNF-α shRNA to macrophages by significantly down-regulating the expression of TNF-α. Moreover, the complex was extremely efficient in decreasing the severity of arthritis in mice with collagen-induced arthritis. PDAPEI delivered TNF-α shRNA has great potential in the treatment of RA.

Gene Delivery Method Using Photo-Responsive Poly(β-Amino Ester) as Vectors

Nonviral vectors show great potential in delivering nucleic acids (NA) into many mammalian cells to achieve efficient gene transfection. Among these, cationic polymer is one of the most widely used nonviral gene delivery vectors, forming the polymer/NA complexes for the intracellular transportation and release of the genetic materials into the target mammalian cells. Here we describe the poly(β-amino ester) (PBAE) with the photo-responsive domain built in the polymers, as a UV-light-responsive nonviral gene delivery vector to deliver and release plasmid DNA (pDNA) into HeLa cells and achieve enhanced transfection efficiency.

Polymers for nucleic acid transfer-an overview

For the last five decades cationic polymers have been used for nucleic acids transfection. Our understanding of polymer-nucleic acid interactions and their rational use in delivery has continuously increased. The great improvements in macromolecular chemistry and the recognition of distinct biological extra- and intracellular delivery hurdles triggered several breakthrough developments, including the discovery of natural and synthetic polycations for compaction of nucleic acids into stable nanoparticles termed polyplexes; the incorporation of targeting ligands and surface-shielding of polyplexes to enable receptor-mediated gene delivery into defined target tissues; and strongly improved intracellular transfer efficacy by better endosomal escape of vesicle-trapped polyplexes into the cytosol. These experiences triggered the development of second-generation polymers with more dynamic properties, such as endosomal pH-responsive release mechanisms, or biodegradable units for improved biocompatibility and intracellular release of the nucleic acid pay load. Despite a better biological understanding, significant challenges such as efficient nuclear delivery and persistence of gene expression persist. The therapeutic perspectives widened from pDNA-based gene therapy to application of novel therapeutic nucleic acids including mRNA, siRNA, and microRNA. The finding that different therapeutic pay loads require different tailor-made carriers complicates preclinical developments. Convincing evidence of medical efficacy still remains to be demonstrated. Bioinspired multifunctional polyplexes resembling "synthetic viruses" appear as attractive opportunity, but provide additional challenges: how to identify optimum combinations of functional delivery units, and how to prepare such polyplexes reproducibly in precise form? Design of sequence-defined polymers, screening of combinatorial polymer and polyplex libraries are tools for further chemical evolution of polyplexes.

Photochemical internalization-mediated nonviral gene transfection: polyamine core-shell nanoparticles as gene carrier

The overall objective of the research was to investigate the utility of photochemical internalization (PCI) for the enhanced nonviral transfection of genes into glioma cells. The PCI-mediated introduction of the tumor suppressor gene phosphatase and tensin homolog (PTEN) or the cytosine deaminase (CD) pro-drug activating gene into U87 or U251 glioma cell monolayers and multicell tumor spheroids were evaluated. In the study reported here, polyamine-DNA gene polyplexes were encapsulated in a nanoparticle (NP) with an acid degradable polyketal outer shell. These NP synthetically mimic the roles of viral capsid and envelope, which transport and release the gene, respectively. The effects of PCI-mediated suppressor and suicide genes transfection efficiency employing either “naked” polyplex cores alone or as NP-shelled cores were compared. PCI was performed with the photosensitizer AlPcS 2a and λ=670-nm laser irradiance. The results clearly demonstrated that the PCI can enhance the delivery of both the PTEN or CD genes in human glioma cell monolayers and multicell tumor spheroids. The transfection efficiency, as measured by cell survival and inhibition of spheroid growth, was found to be significantly greater at suboptimal light and DNA levels for shelled NPs compared with polyamine-DNA polyplexes alone.

Maximizing gene delivery efficiencies of cationic helical polypeptides via balanced membrane penetration and cellular targeting

The application of non-viral gene delivery vectors is often accompanied with the poor correlation between transfection efficiency and the safety profiles of vectors. Vectors with high transfection efficiencies often suffer from high toxicities, making it unlikely to improve their efficiencies by increasing the DNA dosage. In the current study, we developed a ternary complex system which consisted of a highly membrane-active cationic helical polypeptide (PVBLG-8), a low-toxic, membrane-inactive cationic helical polypeptide (PVBLG-7) capable of mediating mannose receptor targeting, and DNA. The PVBLG-7 moiety notably enhanced the cellular uptake and transfection efficiency of PVBLG-8 in a variety of mannose receptor-expressing cell types (HeLa, COS-7, and Raw 264.7), while it did not compromise the membrane permeability of PVBLG-8 or bring additional cytotoxicities. Because of the simplicity and adjustability of the self-assembly approach, optimal formulations of the ternary complexes with a proper balance between membrane activity and targeting capability were easily identified in each specific cell type. The optimal ternary complexes displayed desired cell tolerability and markedly outperformed the PVBLG-8/DNA binary complexes as well as commercial reagent Lipofectamine™ 2000 in terms of transfection efficiency. This study therefore provides an effective and facile strategy to overcome the efficiency-toxicity poor correlation of non-viral vectors, which contributes insights into the design strategy of effective and safe non-viral gene delivery vectors.

A genetically-encoded KillerRed protein as an intrinsically generated photosensitizer for photodynamic therapy

Photodynamic therapy (PDT) has received considerable attention as a therapeutic treatment for cancer and other diseases; however, it is frequently accompanied by prolonged phototoxic reaction of the skin due to slow clearance of synthetic photosensitizers (PSs) administered externally. This study was designed to investigate the genetic use of pKillerRed-mem, delivered using complexes of chitosan (CS) and poly(γ-glutamic acid) (γPGA), to intracellularly express a membrane-targeted KillerRed protein that can be used as a potential PS for PDT. Following transfection with CS/pKillerRed/γPGA complexes, a red fluorescence protein of KillerRed was clearly seen at the cellular membranes. When exposed to green-light irradiation, the KillerRed-positive cells produced an excessive amount of reactive oxygen species (ROS) in a time-dependent manner. Data from viability assays indicate that ROS have an important role in mediating KillerRed-induced cytotoxicity, apoptosis, and anti-proliferation, suggesting that KillerRed can be used as an intrinsically generated PS for PDT treatments. Notably, the phototoxic reaction of KillerRed toward cells gradually became negligible over time, presumably because of its intracellular degradability. These experimental results demonstrate that this genetically encoded KillerRed is biodegradable and has potential for PDT-induced destruction of diseased cells.

Chitosan nanoparticle carrying small interfering RNA to platelet-derived growth factor B mRNA inhibits proliferation of smooth muscle cells in rabbit injured arteries

The purpose of this study was to elucidate the transfection of chitosan nanoparticle carrying small interfering RNA against platelet-derived growth factor B (PDGF-B) to inhibit the expression of PDGF-B mRNA and proliferation of smooth muscle cells. A rabbit iliac artery injury model was constructed. A small interfering RNA (siRNA) against PDGF-B mRNA expression vector was constructed and packaged by chitosan nanoparticle to transfect into the vascular smooth muscle cells (vSMCs) of balloon catheter-injured rabbit iliac artery wall, using a therapeutic ultrasound for the gene delivery. The experiment was divided into two groups: experimental group, denudation and nano-PDGF-B siRNA treated, and only single denudation as control. Effects of the siRNA on the expressions of proliferating cell nuclear antigen (PCNA) and PDGF-B mRNA by vSMCs and the proliferation of vSMCs were observed with the methods of routine pathological, immunohistochemical staining, in situ hybridization and morphometry. The nano siRNA against PDGF-B was successfully transfected. The nano siRNA significantly inhibited the expressions of PCNA and PDGF-B mRNA in intimal vSMCs. The local intimal thickness and area were also reduced remarkably. In conclusion, transfection of chitosan nanoparticle carrying siRNA against PDGF-B mRNA could inhibit proliferation of vSMCs in the rabbit iliac artery injury model.

Bioreducible and acid-labile poly(amido amine)s for efficient gene delivery

Intracellular processes, including endosomal escape and intracellular release, are efficiency-determining steps in achieving successful gene delivery. It has been found that the presence of acid-labile units in polymers can facilitate endosomal escape and that the presence of reducible units in polymers can lead to intracellular release. In this study, poly(amido amine)s with both bioreducible and acid-labile properties were synthesized to improve gene delivery compared with single-responsive carriers. Transfection and cytotoxicity were evaluated in three cell lines. The complexes of DNA with dual-responsive polymers showed higher gene transfection efficiency than single-responsive polymers and polyethylenimine. At the same time, these polymers were tens of times less cytotoxic than polyethylenimine. Therefore, a polymer that is both reducible and acid-labile is a promising material for efficient and biocompatible gene delivery.

Facile functionalization of polyesters through thiol-yne chemistry for the design of degradable, cell-penetrating and gene delivery dual-functional agents

Synthesis of polyesters bearing pendant amine groups with controlled molecular weights and narrow molecular weight distributions was achieved through ring-opening polymerization of 5-(4-(prop-2-yn-1-yloxy)benzyl)-1,3-dioxolane-2,4-dione, an O-carboxyanhydride derived from tyrosine, followed by thiol-yne "click" photochemistry with 2-aminoethanethiol hydrochloride. This class of biodegradable polymers displayed excellent cell penetration and gene delivery properties with low toxicities.

Before and after endosomal escape: roles of stimuli-converting siRNA/polymer interactions in determining gene silencing efficiency

Silencing the expression of a target gene by RNA interference (RNAi) shows promise as a potentially revolutionizing strategy for manipulating biological (pathological) pathways at the translational level. However, the lack of reliable, efficient, versatile, and safe means for the delivery of small interfering RNA (siRNA) molecules, which are large in molecular weight, negatively charged, and subject to degradation, has impeded their use in basic research and therapy. Polyplexes of siRNA and polymers are the predominant mode of siRNA delivery, but innovative synthetic strategies are needed to further evolve them to generate the desired biological and therapeutic effects. This Account focuses on the design of polymeric vehicles for siRNA delivery based on an understanding of the molecular interactions between siRNA and cationic polymers. Ideal siRNA/polymer polyplexes should address an inherent design dilemma for successful gene silencing: (1) Cationic polymers must form tight complexes with siRNA via attractive electrostatic interactions during circulation and cellular internalization and (2) siRNA must dissociate from its cationic carrier in the cytoplasm before they are loaded into RNA-induced silencing complex (RISC) and initiate gene silencing. The physicochemical properties of polymers, which dictate their molecular affinity to siRNA, can be programmed to be altered by intracellular stimuli, such as acidic pH in the endosome and cytosolic reducers, subsequently inducing the siRNA/polymer polyplex to disassemble. Specific design goals include the reduction of the cationic density and the molecular weight, the loss of branched structure, and changes in the hydrophilicity/hydrophobicity of the polymeric siRNA carriers, via acid-responsive degradation and protonation processes within the endosome and glutathione (GSH)-mediated reduction in the cytoplasm, possibly in combination with gradual stimuli-independent hydrolysis. Acetals/ketals are acid-cleavable linkages that have been incorporated into polymeric materials for stimuli-responsive gene and drug delivery. Tailoring the ketalization ratio and the molecular weight of ketalized branched PEI (K-BPEI) offers molecular control of the intracellular trafficking of siRNA/polymer polyplexes and, therefore, the gene silencing efficiency. The ketalization of linear PEI (K-LPEI) enhances gene silencing in vitro and in vivo by improving siRNA complexation with the polymer during circulation and cellular internalization, supplementing proton buffering efficiency of the polymer in the endosome, and facilitating siRNA dissociation from the polymer in the cytoplasm, in a serum-resistant manner. Spermine polymerization via ketalization and esterification for multistep intracellular degradations provides an additional polymeric platform for improved siRNA delivery and highly biocompatible gene silencing. The chemistry presented in this Account will help lay the foundation for the development of innovative and strategic approaches that advance RNAi technology.

Mechanistic study of transfection of chitosan/DNA complexes coated by anionic poly(γ-glutamic acid)

Chitosan (CS) has been investigated as a non-viral carrier for gene delivery, but resulting in a relatively low transfection. To address this concern, we developed a ternary system comprised the core of CS/DNA complex and the outer coating of an anionic polymer, poly(γ-glutamic acid) (γ-PGA). In molecular dynamic (MD) simulations, we found that γ-PGA was entangle tightly with the excess CS emanating from the surface of test complexes, thus making them more compact. With γ-PGA coating, the extent of test complexes internalized and their transfection efficiency were evidently enhanced. Trypsin treatment induced a concentration-dependent decrease in internalization of the γ-PGA-coated complexes, suggesting a specific protein-mediated endocytosis. The endocytosis inhibition study indicates that the γ-glutamyl transpeptidase (GGT) present on cell membranes was responsible for the uptake of test complexes. The amine group in the N-terminal γ-glutamyl unit on γ-PGA played an essential role in the interaction with GGT. When entangled with CS, the free N-terminal γ-glutamyl unit of γ-PGA on test complexes was exposed and might thus be accommodated within the γ-glutamyl binding pocket of the membrane GGT. Above results suggest that the γ-PGA coating on CS/DNA complexes can significantly enhance their cellular uptake via a specific GGT-mediated pathway. Knowledge of the uptake mechanism is crucial for the development of an efficient vector for gene transfection.

Simultaneous gene transduction and silencing using stimuli-responsive viral/nonviral chimeric nanoparticles

Despite viral vectors' predominant use in clinical trials, due to higher gene delivery efficiency than nonviral counterparts, intrinsic immunogenicity and limited tunability for multi-modal effects are major concerns for their usage in gene therapy. An adeno-associated viral (AAV) particle was shielded with acid-degradable, siRNA-encapsulating polyketal (PK) shell, resulting in core-shell viral/nonviral chimeric nanoparticles (ChNPs). The AAV core of a ChNP is protected from immune responses by the PK shell which also facilitates the intracellular trafficking of the AAV core and efficiently releases the encapsulated siRNA into the cytoplasm. ChNPs led to significantly enhanced gene transduction, compared to unmodified free AAVs, and simultaneous silencing of a target gene, while avoiding inactivation by recognition from the immune system. Furthermore, conjugation of sialic acid (SA) on the surface of ChNPs enabled receptor-mediated targeted gene delivery to CD22-expressing cells. The ChNPs developed in this study combine the advantages of both viral and nonviral vectors and are a promising platform for targeted co-delivery of DNA and siRNA in inducing synergistic therapeutic effects by simultaneous expression and silencing of multiple genes.

Effects of poly(lactic-co-glycolic acid) on preparation and characteristics of plasmid DNA-loaded solid lipid nanoparticles

Poly(lactic-co-glycolic acid) (PLGA) was used as a polymeric emulsifier to encapsulate plasmid DNA into hydrogenated castor oil (HCO)-solid lipid nanoparticles (SLN) by w/o/w double emulsion and solvent evaporation techniques. The effects of PLGA on the preparation, characteristics and transfection efficiency of DNA-loaded SLN were studied. The results showed that PLGA was essential to form the primary w/o emulsion and the stability of the emulsion was enhanced with the increase of PLGA content. DNA-loaded SLN were spherical with smooth surfaces. The SLN had a negative charge in weak acid and alkaline environment but acquired a positive charge in acidic pH and the cationisation capacity of the SLN increased with the increase of PLGA/HCO ratio. Agarose gel electrophoresis demonstrated that the majority of the DNA maintained its structural integrity after preparation and being extracted or released from DNA-loaded SLN. When PLGA/HCO ratio increased from 5 to 15%, the encapsulation efficiency, loading capacity and transfection efficiency of the nanoparticles increased significantly, whereas the changes of particle size and polydispersity index were insignificant. Cytotoxicity study in cell culture demonstrated that the SLN was not toxic.

Mechanisms of cellular uptake and intracellular trafficking with chitosan/DNA/poly(γ-glutamic acid) complexes as a gene delivery vector

Chitosan (CS)-based complexes have been considered as a vector for DNA delivery; nonetheless, their transfection efficiency is relatively low. An approach by incorporating poly(γ-glutamic acid) (γ-PGA) in CS/DNA complexes was developed in our previous study to enhance their gene expression level; however, the detailed mechanisms remain to be understood. The study was designed to investigate the mechanisms in cellular uptake and intracellular trafficking of CS/DNA/γ-PGA complexes. The results of our molecular dynamic simulations suggest that after forming complexes with CS, γ-PGA displays a free γ-glutamic acid in its N-terminal end and thus may be recognized by γ-glutamyl transpeptidase in the cell membrane, resulting in a significant increase in their cellular uptake. In the endocytosis inhibition study, we found that the internalization of CS/DNA complexes took place via macropinocytosis and caveolae-mediated pathway; by incorporating γ-PGA in complexes, both uptake pathways were further enhanced but the caveolae-mediated pathway played a major role. TEM was used to gain directly understanding of the internalization mechanism of test complexes and confirmed our findings obtained in the inhibition experiments. After internalization, a less percentage of co-localization of CS/DNA/γ-PGA complexes with lysosomes was observed when compared with their CS/DNA counterparts. A greater cellular uptake together with a less entry into lysosomes might thus explain the promotion of transfection efficiency of CS/DNA/γ-PGA complexes. Knowledge of these mechanisms involving CS-based complexes containing γ-PGA is critical for the development of an efficient vector for DNA transfection.

Chondrogenesis of human mesenchymal stem cells mediated by the combination of SOX trio SOX5, 6, and 9 genes complexed with PEI-modified PLGA nanoparticles

Target gene transfection for desired cell differentiation has recently become a major issue in stem cell therapy. For the safe and stable delivery of genes into human mesenchymal stem cells (hMSCs), we employed a non-viral gene carrier system such as polycataionic polymer, poly(ethyleneimine) (PEI), polyplexed with a combination of SOX5, 6, and 9 fused to green fluorescence protein (GFP), yellow fluorescence protein (YFP), or red fluorescence protein (RFP) coated onto PLGA nanoparticles. The transfection efficiency of PEI-modified PLGA nanoparticle gene carriers was then evaluated to examine the potential for chondrogenic differentiation by carrying the exogenous SOX trio (SOX5, 6, and 9) in hMSCs. Additionally, use of PEI-modified PLGA nanoparticle gene carriers was evaluated to investigate the potential for transfection efficiency to increase the potential ability of chondrogenesis when the trio genes (SOX5, 6, and 9) polyplexed with PEI were delivered into hMSCs. SOX trio complexed with PEI-modified PLGA nanoparticles led to a dramatic increase in the chondrogenesis of hMSCs in in vitro culture systems. For the PEI/GFP and PEI/SOX5, 6, and 9 genes complexed with PLGA nanoparticles, the expressions of GFP as reporter genes and SOX9 genes with PLGA nanoparticles showed 80% and 83% of gene transfection ratios into hMSCs two days after transfection, respectively.

A reliable method for detecting complexed DNA in vitro

Quantification of eluted nucleic acids is a critical parameter in characterizing biomaterial based gene-delivery systems. The most commonly used method is to assay samples with an intercalating fluorescent dye such as PicoGreen®. However, this technique was developed for unbound DNA and the current trend in gene delivery is to condense DNA with transfection reagents, which interfere with intercalation. Here, for the first time, the DNA was permanently labeled with the fluorescent dye Cy5 prior to complexation, an alternative technique hypothesized to allow quantification of both bound and unbound DNA. A comparison of the two methods was performed by quantifying the elution of six different varieties of DNA complexes from a model biomaterial (collagen) scaffold. After seven days of elution, the PicoGreen® assay only allowed detection of three types of complexes (those formed using Lipofectin™ and two synthesised copolymers). However, the Cy5 fluorescent labeling technique enabled detection of all six varieties including those formed via common transfection agents poly(ethylene imine), poly-L-lysine and SuperFect™. This allowed reliable quantification of the elution of all these complexes from the collagen scaffold. Thus, while intercalating dyes may be effective and reliable for detecting double-stranded, unbound DNA, the technique described in this work allowed reliable quantification of DNA independent of complexation state.

Bioresponsive small molecule polyamines as noncytotoxic alternative to polyethylenimine

Nonviral gene therapy continues to require novel synthetic vectors to deliver therapeutic nucleic acids effectively and safely. The majority of synthetic nonviral vectors employed in clinical trials to date have been cationic liposomes; however, cationic polymers are attracting increasing attention. One of the few cationic polymers to enter clinical trials has been polyethylenimine (PEI); however, doubts remain over its cytotoxicity, and in addition it displays lower levels of transfection than viral systems. Herein, we report on the development of a series of small molecule analogues of PEI that are bioresponsive to the presence of pDNA, forming poly(disulfide)s that are capable of efficacious transfection with no associated toxicity. The most effective small molecule developed, a cyclic disulfide based upon a spermine backbone, is shown to form very well-defined polyplexes (100-200 nm in diameter) that mediate murine lung transfection in vivo to within an order of magnitude of in vivo jetPEI, and at the same time display a much improved cytotoxicity profile.

Study on construction of nano tPA plasmid to prevent thrombosis after mechanical valve replacement in dogs

BACKGROUND

Mechanical valve is inclined to induce thrombosis. We intend to elucidate the transfection of nano tissue-type plasminogen activator (tPA) gene plasmid to prevent thrombosis after tricuspid mechanical valve replacement in dogs.

METHODS

A dog model of mechanical tricuspid valve replacement was constructed. A constructed chitosan nano tPA gene plasmid was used to transfect the dog cardiocytes at the same time of tricuspid valve replacement. The effect of this gene on the survival of dogs, anticoagulation (prothrombin time, INR and D-dimer contents, thrombosis in heart), and the expressions of tPA were observed.

RESULTS

Nano tPA gene plasmid was successfully constructed and transfected into cardiocytes. The gene could significantly increase the survival of animals and the contents of D-dimer (P < 0.01), and could prevent thrombus formation on mechanical valves, but there was no significant difference of prothrombin time and INR between two groups (P > 0.05).

CONCLUSION

The constructed nano tPA gene plasmid could prevent thrombus formation after mechanical valve replacement, which provides a clue for clinical use.

Well-defined cationic shell crosslinked nanoparticles for efficient delivery of DNA or peptide nucleic acids

This mini-review highlights developments that have been made over the past year to advance the construction of well-defined nanoscale objects to serve as devices for cell transfection. Design of the nanoscale objects originated from biomimicry concepts, using histones as the model, to afford cationic shell crosslinked knedel-like (cSCK) nanoparticles. Packaging and delivery of plasmid DNA, oligonucleotides, and peptide nucleic acids were studied by dynamic light scattering, transmission electron microscopy, gel electrophoresis, biological activity assays, RT-PCR measurements, flow cytometry, and confocal fluorescence microscopy. With the demonstration of more efficient cell transfection in vitro than that achieved using commercially-available transfection agents, together with the other features offered by the robust nanostructural framework, work continues toward the application of these cSCKs for in vivo molecular recognition of genetic material, for imaging and therapy targeted specifically to pulmonary injury and disease.