Polymeric micelles comprising stearic acid-grafted polyethyleneimine as nonviral gene carriers

Non-viral vectors composed of biodegradable polymers or lipids have been considered as a safer alternative for gene carriers over viral vectors. Among some of the cationic polymers, polyethyleneimine (PEI) possess high pH-buffering capacity that can provide protection to nucleotides from acidic degradation and promotes endosomal and lysosomal release. However, it has been reported that cytotoxicity of PEI depends on the molecular weight of the polymer. Hence modifications of PEI structure for clinical application have been developed in order to reduce the cytotoxicity, or improve the insufficient transfection efficiency of lower molecular weight PEI. In this study, 10 k PEI was modified by grafting stearic acid (SA) and formulated to polymer micelles with positive surface charge and evaluated for pDNA delivery. The amine group on PEI was crosslinked with the carboxylic group of stearic acid by 1-ethyl-3-(3-dimethylamino-propyl) carbodiimide (EDC) as linker. PEI-SA micelles were then prepared using oil in water (o/w) solvent evaporation method. The success of PEI-SA conjugation structure was confirmed with 1H NMR. The average diameter and zeta potential determined by photon correlation spectroscopy was 149.6 +/- 1.2 nm and 64.1 +/- 1.5 mV, respectively. These self-assemble positive charge micelles showed effective binding to pDNA for transfection. PEI-SA micelles exhibited lower cytotoxicity compared to that of PEI only, while flow cytometry analysis revealed PEI-SA/pEGFP complex provided 62% high EGFP expression. Luciferase activity also showed high transfection efficiency of PEI-SA micelles for weight ratio above 4.5 that was comparable to PEI only. These results demonstrated that stearic acid grafted PEI micelles can provide high transfection efficiency comparable to unmodified PEI, and exhibit low cytotoxicity. Stearic acid grafted PEI micelles can be promising polymer carriers in genetic therapy.     

Charge shielding effects on gene delivery of polyethylenimine/DNA complexes: PEGylation and phospholipid coating

Polyethylenimine (PEI) is an efficient cationic polymer for gene delivery, but defective in biocompatibility. In this study, we developed two different strategies to shield the positively charged PEI/DNA complexes: PEGylation and lipid coating. The physicochemical properties, cytotoxicity and transfection efficiency of the two gene delivery systems were investigated. Both PEGylation and lipid coating succeeded in reducing the zeta-potential of the complexes. Lipid-coated PEI/DNA complexes (LPD complexes) and PEI/DNA complexes exhibited similar cytotoxicity, whereas PEG-PEI/DNA complexes showed lower cytotoxicity, especially at high N/P ratios. LPD complexes were less efficient in transfection compared to PEG-PEI/DNA complexes. The transfection efficiency was influenced remarkably by cytotoxicity and surface charge of the complexes. Intracellular processes studies revealed that endosomal release might be one of the rate-limiting steps in cell transfection with PEI as a gene delivery carrier.     

A Highly Emissive Conjugated Polyelectrolyte Vector for Gene Delivery and Transfection

An intrinsically fluorescent cationic polyfluorene ( CCP ) has been designed, synthesized, characterized, and examined as a plasmid DNA (pDNA) delivery vector. This material facilitates nucleic acid binding, encapsulation and efficient cellular uptake. CCP can effectively protect pDNA against nuclease degradation, which is necessary for gene carriers. Green fluorescent protein (GFP) expression experiments reveal that CCP can achieve efficient delivery and transfection of pDNA encoding GFP gene with 92% efficiency, which surpasses that of commercial transfection agents, lipofectamine 2000 (Lipo) and polyethylenimine (PEI). CCP is also highly fluorescent, with 43% quantum yield in water, and exhibits excellent photostability, which allows for real‐time tracking the location of gene delivery and transfection. These features and capabilities represent a major step toward designing and applying conjugated polymers that function in both imaging and therapeutic applications.     

Transfection ability and intracellular DNA pathway of nanostructured gene-delivery systems

Considerable efforts have been devoted to the design of structured materials with functional properties. Polyelectrolyte multilayer films are now a well-established nanostructured concept with numerous potential applications, in particular as biomaterial coatings. This technique allows the preparation of nanostructured architectures exhibiting specific properties for cell-activation control and local drug delivery. In this study, we used a multilayered system made of poly-(l-lysine)/hyaluronic acid (PLL/HA) as a reservoir for active DNA complexes with nonviral gene-delivery vectors, PLL, beta-cyclodextrin (CD), and PLL-CD. When embedded into the multilayered films, the transfection efficiencies of the DNA complexes and the cell viability were improved. The highest transfection efficiency was obtained with the PLL-CD/plasmid DNA (pDNA) complexes. We found that this high transfection efficiency was related to an efficient internalization of the complexes in the cell cytoplasm and selected nuclei domains through a nonendocytotic pathway. For the first time, we report the intracellular pathway of the pDNA in complexes incorporated into the multilayered system.     

Smart Carbon Nanotubes with Laser‐Controlled Behavior in Gene Delivery and Therapy through a Non‐Digestive Trafficking Pathway

Near‐infrared (NIR) laser‐controlled gene delivery presents some benefits in gene therapy, inducing enhanced gene transfection efficiency. In this study, a “photothermal transfection” agent is obtained by wrapping poly(ethylenimine)‐cholesterol derivatives (PEI‐Chol) around single‐walled carbon nanotubes (SWNTs). The PEI‐Chol modified SWNTs (PCS) are effective in compressing DNA molecules and protecting them from DNaseI degradation. Compared to the complexes formed by PEI with DNA (PEI/DNA), complexes of PCS and DNA that are formed (PCS/DNA) exhibit a little lower toxicity to HEK293 and HeLa cells under the same PEI molecule weight and weight ratios. Notably, caveolae‐mediated cellular uptake of PCS/DNA occurs, which results in a safer intracellular transport of the gene due to the decreased lysosomal degradation in comparison with that of PEI/DNA whose internalization mainly depends on clathrin rather than caveolae. Furthermore, unlike PEI/DNA, PCS/DNA exhibits a photothermal conversion ability, which promotes DNA release from PCS under NIR laser irradiation. The NIR laser‐mediated photothermal transfection of PCS_10K/plasmid TP53 (pTP53) results in more apoptosis and necrosis of HeLa cells in vitro than other groups, and achieves a higher tumor‐growth inhibition in vivo than naked pTP53, PEI_25K/pTP53, and PCS_10K/pTP53 alone. The enhanced transfection efficiency of PCS/DNA can be attributed to more efficient DNA internalization into the tumor cells, promotes detachment of DNA from PCS under the mediation of NIR laser and higher DNA stability in the cells due to caveolae‐mediated cellular uptake of the complexes.     

Encapsulation of Plasmid DNA by Nanoscale Metal–Organic Frameworks for Efficient Gene Transportation and Expression

The intracellular delivery and functionalization of genetic molecules play critical roles in gene‐based theranostics. In particular, the delivery of plasmid DNA (pDNA) with safe nonviral vectors for efficient intracellular gene expression has received increasing attention; however, it still has some limitations. A facile one‐pot method is employed to encapsulate pDNA into zeolitic imidazole framework‐8 (ZIF‐8) and ZIF‐8‐polymer vectors via biomimetic mineralization and coprecipitation. The pDNA molecules are found to be well distributed inside both nanostructures and benefit from their protection against enzymatic degradation. Moreover, through the use of a polyethyleneimine (PEI) 25 kD capping agent, the nanostructures exhibit enhanced loading capacity, better pH responsive release, and stronger binding affinity to pDNA. From in vitro experiments, the cellular uptake and endosomal escape of the protected pDNA are greatly improved with the superior ZIF‐8‐PEI 25 kD vector, leading to successful gene expression with high transfection efficacy, comparable to expensive commercial agents. New cost‐effective avenues to develop metal–organic‐framework‐based nonviral vectors for efficient gene delivery and expression are provided.     

Oxidation‐Responsive Nanoassemblies for Light‐Enhanced Gene Therapy

Microenvironment‐responsive supramolecular assemblies have attracted great interest in the biomedical field due to their potential applications in controlled drug release. In this study, oxidation‐responsive supramolecular polycationic assemblies named CPAs are prepared for nucleic acid delivery via the host–guest interaction of β‐cyclodextrin based polycations and a ferrocene‐functionalized zinc tetraaminophthalocyanine core. The reactive oxygen species (ROS) can accelerate the disassembly of CPA/pDNA complexes, which would facilitate the release of pDNA in the complexes and further benefit the subsequent transfection. Such improvement in transfection efficiency is proved in A549 cells with high H₂O₂ concentration. Interestingly, the transfection efficiencies mediated by CPAs are also different in the presence or absence of light in various cell lines such as HEK 293 and 4T1. The single oxygen (¹O₂), produced by photosensitizers in the core of CPAs under light, increases the ROS amount and accelerates the disassembly of CPAs/pDNA complexes. In vitro and in vivo studies further illustrate that suppressor tumor gene p53 delivered by CPAs exhibits great antitumor effects under illumination. This work provides a promising strategy for the design and fabrication of oxidation‐responsive nanoassemblies with light‐enhanced gene transfection performance.     

Enhanced gene transfer with multilayered polyplexes assembled with layer-by-layer technique

Successful gene therapy asks for multifunctional vectors which can not only protect DNA from degradation but also transfer it into nuclear and subsequently express the loaded gene. Here we reported a novel multilayered delivery system constructed with DNA, protamine (Pro) and polyethylenimine (PEI) via lay-by-layer (LbL) technique, which posed multifunctions. DNA was previously condensed into a compact core with Pro which also contained nuclear localisation signals (NLS) domains for nuclear transfer. Then additional DNA was deposited as the first layer onto the cationic core via the electrostatic attraction which would increase the loading dose of DNA. At last, PEI was absorbed as the outmost layer to achieve the endosomal escape. Therefore a quaternary polyplexes which offered high loading of DNA, nuclear transfer ability and endosomal escape capability was constructed with the LbL technique. The obtained quaternary polyplexes showed positive surface charge, spherical morphology, a relatively narrow particle size distribution and strong DNA protection capability. Compared with commercially available PEI/DNA complexes, the novel multifuctional vector exhibited not only lower cytotoxicity (P<0.05) but also higher transfection efficiency in HepG2 and HeLa cells (P<0.05) in vitro test.     

A novel dendrimer based on poly (L-glutamic acid) derivatives as an efficient and biocompatible gene delivery vector

Non-viral gene delivery systems based on cationic polymers have faced limitations related to their relative low gene transfer efficiency, cytotoxicity and system instability in vivo. In this paper, a flexible and pompon-like dendrimer composed of poly (amidoamine) (PAMAM) G4.0 as the inner core and poly (L-glutamic acid) grafted low-molecular-weight polyethylenimine (PLGE) as the surrounding multiple arms was synthesized (MGI dendrimer). The novel MGI dendrimer was designed to combine the merits of size-controlled PAMAM G4.0 and the low toxicity and flexible chains of PLGE. In phosphate-buffered saline dispersions the well-defined DNA/MGI complex above a N/P ratio of 30 showed good stability with particle sizes of approximately 200 nm and a comparatively low polydispersity index. However, the particle size of the DNA/25 kDa polyethylenimine (DNA/PEI 25K) complex was larger than 700 nm under the same salt conditions. The shielding of the compact amino groups at the periphery of flexible PAMAM and biocompatible PLGE chains in MGI resulted in a dramatic decrease of the cytotoxicity compared to native PAMAM G4.0 dendrimer. The in vitro transfection efficiency of DNA/MGI dendrimer complex was higher than that of PAMAM G4.0 dendrimer. Importantly, in serum-containing medium, DNA/MGI complexes at their optimal N/P ratio maintained the same high levels of transfection efficiency as in serum-free medium, while the transfection efficiency of native PAMAM G4.0, PEI 25K and Lipofectamine 2000 were sharply decreased. In vivo gene delivery of pVEGF165/MGI complex into balloon-injured rabbit carotid arteries resulted in significant inhibition of restenosis by increasing VEGF165 expression in local vessels. Therefore, the pompon-like MGI dendrimer may be a promising vector candidate for efficient gene delivery in vivo.     

The influence of physicochemical parameters on the efficacy of non-viral DNA transfection complexes: a comparative study

Various polycationic vehicles have been developed to facilitate the transfer of foreign DNA into mammalian cells. Structure-activity studies suggested that biophysical properties, such as size, charge, and morphology of the resulting DNA complexes determine transfection efficiency within one class of vector. To investigate the general validity of these criteria, we studied the efficacy of a variety of DNA delivery vehicles including liposomes (DOTAP, SAINT2) with and without helper lipid (DOPE), the polymer polyethyleneimine (PEI), and cationic nanoparticles (Si26H, PLGA/chitosan) in a comparative manner. Sizes of the DNA complexes varied between 100 and 500 nm for PEI polyplexes and DOTAP/DOPE lipoplexes, respectively. The zeta potential was positive for PEI, Si26H, and DOTAP based complexes, while it was neutral for SAINT2-DNA complexes and negative for PLGA/chitosan-DNA complexes. The latter finding was elucidated by AFM, showing a layer of DNA adsorbed onto the nanoparticles. Transfection activity was negligible for PLGA/chitosan nanospheres, moderate for Si26H nanospheres and high for all other complexes, PEI being the most active carrier. The liposomal preparations were of low (DOTAP) or moderate (SAINT2) stability in serum, resulting in a pronounced reduction of gene expression, which was partially restored by the addition of chloroquine. In conclusion, transfection efficiency (i) seems to require a positive or neutral zeta potential, (ii) is depending on size, e.g., is higher for smaller particles, and (iii) requires a vector that is stable in serum.     

Polyethylenimine functionalized magnetic nanoparticles as a potential non-viral vector for gene delivery

Polyethylenimine (PEI) functionalized magnetic nanoparticles were synthesized as a potential non-viral vector for gene delivery. The nanoparticles could provide the magnetic-targeting, and the cationic polymer PEI could condense DNA and avoid in vitro barriers. The magnetic nanoparticles were characterized by Fourier transform infrared spectroscopy, X-ray powder diffraction, dynamic light scattering measurements, transmission electron microscopy, vibrating sample magnetometer and atomic force microscopy. Agarose gel electrophoresis was used to asses DNA binding and perform a DNase I protection assay. The Alamar blue assay was used to evaluate negative effects on the metabolic activity of cells incubated with PEI modified magnetic nanoparticles and their complexes with DNA both in the presence or absence of an external magnetic field. Flow cytometry and fluorescent microscopy were also performed to investigate the transfection efficiency of the DNA-loaded magnetic nanoparticles in A549 and B16-F10 tumor cells with (+M) or without (?M) the magnetic field. The in vitro transfection efficiency of magnetic nanoparticles was improved obviously in a permanent magnetic field. Therefore, the magnetic nanoparticles show considerable potential as nanocarriers for gene delivery.     

Evaluation of PEG-transferrin-PEI nanocomplex as a gene delivery agent

Polyethylenimine (PEI) has been shown to be an efficient nonviral delivery vector. To improve its specificity and reduce its cytotoxicity, PEI should be modified. Transferrin (Tf) is a cell-binding ligand and Tf-receptors are expressed in malignant cells. Modification of cationic polymer by polyethylene glycol (PEG) can reduce the protein interaction and cell cytotoxicity of delivery vectors. We have synthesized PEG-Tf-PEI conjugate as an efficient and safe carrier of plasmid DNA (pDNA). Nanocomplexes of conjugates with pDNA were characterized by measuring the particle size and the surface charge. Transfection efficiency of nanocomplexes in Jurkat cells was improved and cytotoxicity was decreased compared with those of PEI complex. This was due to a reduction in the membrane damaging effect via shielding of the positive charge on the nanocomplex surface by PEG.     

Formulation of chitosan-TPP-pDNA nanocapsules for gene therapy applications

The encapsulation of DNA inside nanoparticles meant for gene delivery applications is a challenging process where several parameters need to be modulated in order to design nanocapsules with specific tailored characteristics. The purpose of this study was to investigate and improve the formulation parameters of plasmid DNA (pDNA) loaded in chitosan nanocapsules using tripolyphosphate (TPP) as polyanionic crosslinker. Nanocapsule morphology and encapsulation efficiency were analyzed as a function of chitosan degree of deacetylation and chitosan-TPP ratio. The manipulation of these parameters influenced not only the particle size but also the encapsulation and release of pDNA. Consequently the transfection efficiency of the nanoparticulated systems was also enhanced with the optimization of the particle characteristics. Overall, the differently formulated nanoparticulated systems possess singular properties that can be employed according to the desired gene delivery application.     

The characteristics and transfection efficiency of PEI modified by biodegradable poly(β-amino ester)

To improve the cytotoxicity of PEI25k and the transfection efficiency of poly(β-amino ester) with DNA, we synthesized a poly(β-amino ester), PEDP, bearing ester linkages in the backbone and tertiary amines in the backbone and side chain and prepared a binary mixture, PEDP–PEI25k, using physical blending meyhod. Both poly(β-amino ester) PEDP and binary mixture PEDP–PEI25k, readily self-assembled with plasmid DNA (pCMV-β gal) in a HEPES buffer, were characterized by dynamic light scattering. The results reveal that PEDP–PEI25k was able to self-assemble plasmid DNA into PEDP–PEI25k/DNA nano-complexes small enough to enter a cell through endocytosis. Titration studies were performed to determine the buffering capacities of PEDP and PEDP–PEI25k. The COS-7 cell viabilities in the presence of PEDP and PEDP–PEI25k were studied. At low mass ratio of PEDP/PEI25k (1/1), it is found that the transfection curve of PEDP–PEI25k/DNA bearing a maximum peak is similar to that of PEI25k/DNA. In addition, the PEDP–PEI25k/DNA complexes were able to transfect COS-7 cells in vitro with a high efficiency comparable to a well-known gene carrier PEI25k/DNA. The results indicate that binary mixture PEDP–PEI25k is an attractive cationic carrier for gene delivery and an interesting candidate for further study.     

Hybrid polymer-grafted multiwalled carbon nanotubes for in vitro gene delivery

Carbon nanotubes (CNTs) consist of carbon atoms arranged in sheets of graphene rolled up into cylindrical shapes. This class of nanomaterials has attracted attention because of their extraordinary properties, such as high electrical and thermal conductivity. In addition, development in CNT functionalization chemistry has led to an enhanced dispersibility in aqueous physiological media which indeed broadens the spectrum for their potential biological applications including gene delivery. The aim of this study is to determine the capability of different cationic polymer-grafted multiwalled carbon nanotubes (MWNTs) (polymer-g-MWNTs) to efficiently complex and transfer plasmid DNA (pCMV-βGal) in vitro without promoting cytotoxicity. Carboxylated MWNT is chemically conjugated to the cationic polymers polyethylenimine (PEI), polyallylamine (PAA), or a mixture of the two polymers. In order to explore the potential of these polymer-g-MWNTs as gene delivery systems, we first study their capacity to complex plasmid DNA (pDNA) using agarose gel electrophoresis. Gel migration studies confirm pDNA binding to polymer-g-MWNT with different affinities, highest for PEI-g-MWNT and PEI/PAA-g-CNT constructs. β-galactosidase expression is assessed in human lung epithelial (A549) cells, and the cytotoxicity is determined by modified LDH assay after 24 h incubation period. Additionally, PEI-g-MWNT and/or PEI/PAA-g-MWNT reveal an improvement in gene expression when compared to the naked pDNA or to the equivalent amounts of PEI polymer alone. Mechanistically, pDNA was delivered by the polymer-g-MWNT constructs via a different pathway compared to those used by polyplexes. In conclusion, polymer-g-MWNTs may be considered in the future as a versatile tool for efficient gene transfer in cancer cells in vitro, provided their toxicological profile is established.     

Kidney-specific peptide-conjugated poly(ester amine) for the treatment of kidney fibrosis

Kidney gene therapy using the hepatocyte growth factor (HGF) gene may offer new strategies for the treatment of chronic renal disease such as kidney fibrosis, because HGF has the potential to promote tubular repair and to inhibit tissue fibrosis. As a non-viral vector for gene delivery, polyethylenimine (PEI) exhibits high gene expression due to its buffering capacity with cytotoxicity, although its cytotoxicity depends on its molecular weight. In this study, to minimize the cytotoxicity of PEI with a high transfection efficiency, biodegradable poly(ester amine) (PEA) based on glycerol dimethacrylate (GDM) and low molecular weight PEI (LMW PEI) was synthesized and kidney targeting peptide was conjugated to the PEA (PEP-PEA) to give it kidney cell specificity. The PEP-PEA showed good physicochemical properties as a gene delivery carrier, such as DNA condensation ability, protection of the DNA in the complexes from enzyme degradation, and formation of nanosized complexes with spherical shapes. Higher transfection efficiency in 293T cells was achieved with the PEP-PEA than with the PEA and the PEI 25 kDa with lower cytotoxicity. Also, the HGF gene that was complexed with the PEP-PEA was specifically delivered to the obstructed kidney in the unilateral ureteral obstruction (UUO) model rats. The delivered HGF gene exhibited potency in recovering renal functions, which indicates the potential of the PEP-PEA as a safe and efficient carrier for the treatment of kidney fibrosis.     

An E3‐14.7K Peptide that Promotes Microtubules‐Mediated Transport of Plasmid DNA Increases Polyplexes Transfection Efficiency

Chemical vectors as cationic polymers and cationic lipids are promising alternatives to viral vectors for gene therapy. Beside endosome escape and nuclear import, plasmid DNA (pDNA) migration in the cytosol toward the nuclear envelope is also regarded as a limiting step for efficient DNA transfection with non‐viral vectors. Here, the interaction between E3‐14.7K and FIP‐1 to favor migration of pDNA along microtubules is exploited. E3‐14.7K is an early protein of human adenoviruses that interacts via FIP‐1 (Fourteen.7K Interacting Protein 1) protein with the light‐chain components of the human microtubule motor protein dynein (TCTEL1). This peptide is conjugated with pDNA and mediates interaction of pDNA in vitro with isolated microtubules as well as with microtubules in cellulo. Videomicroscopy and tracking treatment of images clearly demonstrate that P79‐98/pDNA conjugate exhibits a linear transport with large amplitude along microtubules upon 2 h transfection with polyplexes whereas control pDNA conjugate exhibits small non‐directional movements in the cytoplasm. Remarkably, P79‐98/peGFP polyplexes enhance by a factor 2.5 (up to 76%) the number of transfected cells. The results demonstrate, for the first time, that the transfection efficiency of polyplexes can be drastically increased when the microtubules migration of pDNA is facilitated by a peptide allowing pDNA docking to TCTEL1. This is a real breakthrough in the non viral gene delivery field that opens hope to build artificial viruses.     

Transferrin-mediated PEGylated nanoparticles for delivery of DNA/PLL

The purpose of this work was to determine the stability of pDNA/poly(L-lysine) complex (DNA/PLL) during microencapsulation, prepare transferrin (TF) conjugated PEGylated nanoparticles (TF-PEG-NP) loading DNA/PLL, and assess its physicochemical characteristics and in vitro transfection efficiency. The DNA/PLL was prepared by mixing plasmid DNA (pDNA) in deionized water with various amounts of PLL. PEGylated nanoparticles (PEG-NP) loading DNA/PLL were prepared by a water-oil-water double emulsion solvent evaporation technique. TF-PEG-NP was prepared by coupling TF with PEG-NP. The physicochemical characteristics of TF-PEG-NP and in vitro transfection efficiency on K562 cells were measured. The results showed that free pDNA reserved its double supercoiled form (dsDNA) for only on average 25.7% after sonification, but over 70% of dsDNA was reserved after pDNA was contracted with PLL. The particle size range of TF-PEG-NP loading DNA/PLL was 150-450?nm with entrapment efficiency over 70%. TF-PEG-NP exhibited the low burst effect (<10%) within 1 day. After the first phase, DNA/PLL displayed a sustained release. The amount of cumulated DNA/PLL release from TF-PEG-NP with 2% polymer over 7 days was 85.4% for DNA/PLL (1:0.3 mass ratio), 59.8% and 43.1% for DNA/PLL (1:0.6) and DNA/PLL (1:1.0), respectively. To TF-PEG-NP loading DNA/PLL without chloroquine, the percentage of EGFP expressing cells was 28.9% for complexes consisting of DNA/PLL (1:0.3), 38.5% and 39.7% for DNA/PLL (1:0.6) and DNA/PLL (1:1.0), respectively. In TF-PEG-NP loading DNA/PLL with chloroquine, more cells were transfected, the percentage of positive cells was 37.6% (DNA/PLL, 1:0.3), 47.1% (DNA/PLL, 1:0.6) and 45.8% (DNA/PLL, 1:1.0), which meant that the transfection efficiency of pDNA was increased by over 50 times when PLL and TF-PEG-NP were jointly used as a plasmid DNA carrier, in particular, the maximal percentage of positive cells (47.1%) from TF-PEG-NP loading DNA/PLL (1:0.6) was about 70 times the transfection efficiency of free plasmid DNA. The average cell viability of TF-PEG-NP loading DNA/PLL was about 90%, which meant that TF-PEG-NP appeared to be safer than PLL alone. As a result, TF-PEG-NP loading DNA/PLL could be a more effective non-viral vector for the delivery of pDNA.     

In vitro studies of magnetically enhanced transfection in COS-7 cells

In the magnetically enhanced gene delivery technique, DNA complexed with polymer coated aggregated magnetic nanoparticles (AMNPs) is used for effecting transfection. The aim of this study is to examine the relationship between transfection efficiency and the physical characteristics of the polymer coated AMNPs. In vitro studies of transfection efficiency in COS-7 cells were carried out using pEGFP-N1 and pMIR-REPORT complexed polyethylenimine (PEI) coated iron oxide magnetic nanoparticles. PEI coated AMNPs (PEI-AMNPs) with average individual particle diameters in the range of 8 nm to 30 nm were studied and characterized by transmission electron microscopy, vibrating sample magnetometry, X-ray diffractometry, thermal gravimetric analysis and photon correlation spectroscopy methods. PEI-A8MNP and PEI-A30MNP yielded higher transfection efficiency compared to commercial polyMAG particles as well as PEI of equivalent molar ratio of nitrogen/phosphorous (N/P ratio). The transfection efficiency was related to the physical characteristics of the PEI-AMNPs and its complexes: transfection efficiency was strongly positively correlated with saturation magnetization (Ms) and susceptibility (χ), strongly negatively correlated with N/P ratio, moderately positively correlated to zeta potential and moderately negatively correlated to hydrodynamic diameter of the complex. PEI-A8MNP and PEI-A30MNP possessing higher Ms, χ, lower N/P ratio and smaller complex size exhibited higher transfection efficiency compared to PEI-A16MNP which have weaker magnetic properties, higher N/P ratio and larger complex size. We have demonstrated that optimization of the physical properties of PEI-AMNPs is needed to maximize transfection efficiency.     

Preparation of dexamethasone-based cationic liposome and its application to gene delivery in vitro

In this study, dexamethasone was conjugated to PAMAM dendrimer (generation 0) and its gene transfection efficiency was investigated. To make a liposomal solution for gene delivery, DOPE was used as a fusogenic helper lipid. In gel retardation assay, PAMAM-dexamethasone conjugate (PAM-Dex)/DOPE liposome/DNA complex was completely retarded at 8:1 N/P (nitrogen/phosphate) ratio. The physicochemical characteristics are studied by measuring the average size distribution and zeta-potential values of the complexes. In vitro transfection assay showed that the PAM-Dex/DOPE liposome/DNA complex displayed higher gene delivery efficiency compared to PAMAM/DNA complex. In addition, PAM-Dex/DOPE liposome showed the lowest toxicity compared to PAMAM, PEI 25 kD and Lipofectamine. These results indicate that PAM-Dex/DOPE liposome has a potential to be used as an efficient gene carrier for gene therapy.