High Molecular Weight Polyethylenimine Research Articles

A Delicate Balance When Substituting a Small Hydrophobe onto Low Molecular Weight Polyethylenimine to Improve Its Nucleic Acid Delivery Efficiency.

High molecular weight (HMW) polyethylenimine (PEI) is one of the most versatile nonviral gene vectors that was extensively investigated over the past two decades. The cytotoxic profile of HMW PEI, however, encouraged a search for safer alternatives. Because of lack of cytotoxicity of low molecular weight (LMW) PEI, enhancing its performance via hydrophobic modifications has been pursued to this end. Since the performance of modified PEIs depends on the nature and extent of substituents, we systematically investigated the effect of hydrophobic modification of LMW (1.2 kDa) PEI with a short propionic acid (PrA). Moderate enhancements in PEI hydrophobicity resulted in enhanced cellular uptake of polyplexes and siRNA-induced silencing efficacy, whereas further increase in PrA substitution abolished the uptake as well as the silencing. We performed all-atom molecular dynamics simulations to elucidate the mechanistic details behind these observations. A new assembly mechanism was observed by the presence of hydrophobic PrA moieties, where PrA migrated to core of the polyplex. This phenomenon caused higher surface hydrophobicity and surface charge density at low substitutions, and it caused deleterious effects on surface hydrophobicity and cationic charge at higher substitutions. It is evident that an optimal balance of hydrophobicity/hydrophilicity is needed to achieve the desired polyplex properties for an efficient siRNA delivery, and our mechanistic findings should provide valuable insights for the design of improved substituents on nonviral carriers.

Novel glycol chitosan-based polymeric gene carrier synthesized by a Michael addition reaction with low molecular weight polyethylenimine

A glycol chitosan-based polymer that spontaneously assembles with plasmid DNA into nanorods was evaluated as a non-viral vector for gene delivery. Glycol chitosan–methyl acrylate-polyethylenimine (GMP) was synthesized by grafting polyethylenimine onto glycol chitosan via amidation after Michael addition using methyl acrylate. Gel retardation and PicoGreen assay experiments showed complete complex formation with plasmid DNA. GMP/pDNA complexes were characterized using biophysical techniques and were found to be positively charged rod-shape structures with widths in the nanometer scale and lengths in the micrometer scale. Transfection efficiency and cytotoxicity of GMP polymer was evaluated in human epithelial ovary carcinoma (HeLa) cells, human embryonic kidney 293 (HEK293) cells, and human hepatocellular liver carcinoma (HepG2) cells, in comparison to high molecular weight polyethylenimine, a commonly used transfection reagent. Intracellular polymer uptake was compared and confirmed by confocal microscopy. The results demonstrate that GMP, a hybrid polymer of glycol chitosan grafted with branched polyethylenimine, may serve as a promising vehicle for efficient gene delivery.

Grafting Low Contents of Branched Polyethylenimine onto Carbon Fibers to Effectively Improve Their Interfacial Shear Strength with an Epoxy Matrix

The mechanical properties of carbon fiber (CF) reinforced composites are greatly dependent on the interfacial strength between the CFs and matrix. To improve the interfacial adhesion of carbon fiber/epoxy composites, branched polyethylenimine (PEI) is grafted onto the CFs treated in a mixed acid at optimized process time. The chemical compositions and bonds of functionalized CFs are characterized by thermal gravimetric analysis, Fourier‐transform infrared, and X‐ray photoelectron spectroscopy. The surface structures and morphologies of various CFs are analyzed by Raman spectroscopy and scanning electron microscopy, respectively. Microbond test is adopted to evaluate the interfacial shear strength (IFSS) between the CFs and epoxy matrix. The results show that the CFs modified by low molecular weight PEI are better than those modified by high molecular weight PEI. The IFSS of PEI modified CFs can reach a maximum of 107.2 ± 14.3 MPa at a low functionalization degree compared with 78.1 ± 11.6 MPa of unmodified CFs. The branched structure and high density of active amine groups on the PEI chains are responsible for the improved interfacial strength.

Major degradable polycations as carriers for DNA and siRNA

Non-viral gene delivery systems are one of the most potential alternatives to viral vectors because of their less immunogenicity, less toxicity and easy productivity in spite of their low capacity of gene transfection using DNA or silencing using siRNA compared to that of viral vectors. Among non-viral systems, the polycationic derivatives are the most popular gene carriers since they can effectively condense nucleic acids to transfer into the cells, especially the polyethylenimine (PEI) which has been used as a golden standard polymer owing to its high buffering ability for endosomal escape of gene to be expressed. However, PEI has severe problems for its toxicity due to the high positive charge density and non-degradability although the toxicity of PEI depends on its molecular weight (MW) and structure. Therefore, a considerable attention has been paid on synthesis of degradable PEI derivatives using low MW one because low MW PEI is much less toxic than high MW PEI. Other degradable polycationic gene carriers such as polyamidoamines (PAA) and cyclodextrin (CD)-based polycations are also in a significant interest because of their high transfection efficiency with low toxicity. This review in detail explains the recent developments on these three major degradable polycations as promising carriers for deoxyribonucleic acid (DNA) and small interfering RNA (siRNA).

Controlled Synthesis of Water-Soluble NaYF4:Yb3+, Er3+Nanoparticles with Surfactant Dependent Properties

Water-soluble NaYF4:Yb3+, Er3+nanoparticles (NPs) are successfully prepared by a solvothermal reaction using branched polyethylenimine (PEI) with different chain lengths as the surfactants in a water/diethylene glycol (DEG) mixed solution. It is shown that the size of NaYF4NPs prepared with high molecular weight PEI (HPEI) is smaller than that of the NPs prepared with low molecular weight (LPEI), while small-sized NPs exhibit more intense upconversion luminescence intensities than large-sized NPs in the same excitation power of 980 nm. It is found that HPEI is conducive to the formation of smaller NP with high crystallinity. Small-sized NaYF4:Yb3+, Er3+NPs with intense upconversion luminescence and improved crystallinity were related to their growth process. A possible growth mechanism of the samples is proposed. The results of this study can provide new insights into the controlled synthesis of novel NPs.

Effects of physico-chemical properties between poly(ethyleneimine) and silica abrasive on copper chemical mechanical planarization

We investigated the effect of poly (ethyleneimine) (PEI)-modified silica abrasive on the removal rate and the degree of dishing during Cu chemical mechanical planarization (CMP). The PEI-modified silica abrasive was prepared by mutually attractive electrostatic forces between PEI and silica abrasive. The physico-chemical behaviors between PEI and the silica abrasive were evaluated by total organic carbon (TOC), force-separation measurements using atomic force microscopy (AFM) with molecular weight of PEI, which was found to adsorb on silica at pH 7.0 following a Langmuir isotherm. The maximum adsorbed amounts of low and high molecular weight PEI were 0.195mg/m2 and 0.228mg/m2, respectively. AFM results showed the repulsive force of the adsorbed PEI layers on the silica surface and the adsorption thickness of PEI on silica vary with the molecular weight of PEI. A twofold change was observed in the AFM analysis. First, the increased areal density of adsorbed PEI caused a higher zeta-potential and longer reaching repulsive force. Second, the adsorption thickness was also significantly enlarged. High molecular weight showed increased adsorption thickness under similar conditions compared to low molecular weight of PEI. These changes of silica abrasive such as electrostatic forces and steric interaction vary with molecular weight of PEI reduced the dishing of Cu pattern film from 50 to 20nm.

Hepatitis B DNA Vaccine-Polycation Nano-Complexes Enhancing Immune Response by Percutaneous Administration with Microneedle

Percutaneous immune method is becoming an attractive alternative for DNA vaccine as a lot of antigen presenting cells are existed in the viable epidermis. However, due to the barrier function of stratum corneum, it would be hard for DNA vaccine to reach the viable epidermis of the skin. In order to deliver the DNA vaccine successfully cross the stratum corneum, pentagram silicon microneedle array was prepared in this study, and fluorescently labeled nanoparticle was taken as the model to observe the situation inside the skin processed by microneedle. Via microneedle nanoparticles could enter the skin through the micro-channel (diameter about 20-30 µm) and its amount is greatly larger than that enter though the hair follicle of intact skin. A new type of gene vector Pluronic P123-modified polyethyleneimine (P123-PEI) was synthesized by high molecular weight polyethylenimine and Pluronic P123 with the molar ratio of 1 : 1 to take the advantage of P123-PEI as low cytotoxicity and high transfection efficiency. Mice were immunized percutaneously with Hepatitis B DNA vaccine/P123-PEI nano-complexes by microneedle. The humoral and cellular immunity generated in percutaneously immunized mice through microneedle array by Hepatitis B DNA vaccine/P123-PEI nano-complex was significantly higher than that of DNA vaccine intramuscular administration.

Removal of uranium anionic species from aqueous solutions by polyethylenimine–epichlorohydrin resins

The removal of uranium anionic species from aqueous solutions (initial concentration: 10–2,000 mg/L) by a low- and a high molecular weight polyethylenimine–epichlorohydrin resins was studied in the absence of background electrolytes at initial pH (pHinit) 8 to10. The amount of the sorbed U was determined spectrophotometrically using the Arsenazo III method. The maximum uptake was observed at pHinit 8 using both resins. The maximum uptake capacity observed was 221 and 388 mg U/g for the low- and high molecular weight resin respectively. The uptake data were modeled using a number of 2- and 3- parametric isotherm equations (Langmuir, Freundlich, Langmuir–Freundlich, Toth and Redlich–Peterson). The kinetics of the uranium removal was also studied and modeled using the pseudo-first and pseudo-second order equations. The surface and interior of the resin grains were examined after the sorption experiments by scanning electron microscopy/energy dispersive spectroscopy.

Abstract B32: Impact of Lipid-Substitution on Assembly and Delivery of siRNA by Cationic Polymers

Abstract Downregulation of target protein expression by small interfering RNA (siRNA) has been one of the most promising strategies in medicinal therapy since the discovery of this revolutionary process in late 1990s. Many obstacles, however, have to be overcome to achieve safe and efficient siRNA delivery to target cells. Short in vivo half-life of siRNA and safety concerns involved with viral vectors used for DNA transfection are among the main reasons for the necessity of a better delivery system to take full advantage of this strategy. Polycationic polymers have been studied extensively for this purpose and high molecular weight polyethylenimines (PEIs) have led to promising results; however, unacceptable toxicity profile of these polymers has been a hurdle for their clinical application. In this study, we report characterization of a library of polymers synthesized by hydrophobic modification of a low molecular weight (2 kDa) PEI (PEI2) with a wide range of different fatty acids, engineered to enhance their ability to protect and deliver their nucleotide cargo to the cells, while still being water soluble. A general increase in lipid substitution was observed as the lipid:PEI ratio was increased during the synthesis. Among the polymers derived from lipid:PEI ratio of 0.066, caprylic acid-substituted polymer showed a lower binding affinity, while all other polymers performed similarly. Complete siRNA binding was typically achieved at polymer:siRNA ratio of < 0.5. The BC50 (polymer:siRNA ratio needed for 50% binding) was generally increased with the extent of lipid substitution, indicating an adverse effect of lipid substitution on siRNA complexation. Particle size analysis showed a range of 300 to 600 nm for all of the polymer/siRNA complexes, and for all lipid-substituted polymers, a continuous increase in the ζ-potential was observed with increasing polymer:siRNA weight ratio, and all polymers showed positive ζ-potential at the ratio of 10:1. The ζ-potentials of complexes formed with lipid-modified polymers were higher than complexes of PEI2 at all ratios. With the polymer:siRNA ratio of 1:1, all lipid-substituted polymers showed complete protection against degradation, while naked siRNA was readily degraded (<5% intact siRNA remaining) and only ∼68% of siRNA bound with PEI2 remained intact under the experimental conditions. The cytotoxicity of the synthesized polymers was slightly higher than PEI2, but significantly lower than larger MW PEI. Polymer/siRNA complexes formed with lipid-modified polymers increased the cellular uptake of siRNA significantly. Down-regulation of two different target proteins was also evaluated using the modified polymers: a housekeeping enzyme glyceraldehyde-3-phosphate dehydrogenase (GAPDH), and an efflux protein involved in multi-drug resistance (MDR), P-glycoprotein (P-gp). Optimum silencing for the target proteins was achieved by using polymer:siRNA ratio of 4:1 for GAPDH and 8:1 for P-gp. A maximum of 66% and 67% downregulation was observed for GAPDH and P-gp, respectively. Our results indicate that hydrophobic modification of low molecular PEI could render this otherwise ineffective polymer to a safe effective delivery system for intracellular siRNA delivery and silencing of protein expression.

Polyethyleneimine-lipid conjugate-based pH-sensitive micellar carrier for gene delivery

A low molecular weight polyethyleneimine (PEI 1.8 kDa) was modified with dioleoylphosphatidylethanolamine (PE) to form the PEI-PE conjugate investigated as a transfection vector. The optimized PEI-PE/pDNA complexes at an N/P ratio of 16 had a particle size of 225 nm, a surface charge of +31 mV, and protected the pDNA from the action of DNase I. The PEI-PE conjugate had a critical micelle concentration (CMC) of about 34 μg/ml and exhibited no toxicity compared to a high molecular weight PEI (PEI 25 kDa) as tested with B16-F10 melanoma cells. The B16-F10 cells transfected with PEI-PE/pEGFP complexes showed protein expression levels higher than with PEI-1.8 or PEI-25 vectors. Complexes prepared with YOYO 1-labeled pEGFP confirmed the enhanced delivery of the plasmid with PEI-PE compared to PEI-1.8 and PEI-25. The PEI-PE/pDNA complexes were also mixed with various amounts of micelle-forming material, polyethylene glycol (PEG)-PE to improve biocompatibility. The resulting particles exhibited a neutral surface charge, resistance to salt-induced aggregation, and good transfection activity in the presence of serum in complete media. The use of the low-pH-degradable PEG-hydrazone-PE produced particles with transfection activity sensitive to changes in pH consistent with the relatively acidic tumor environment.

Introducing a simple method for toxicity reduction of nanoparticles based on high molecular weight polyethylenimine used as gene delivery vectors

Introducing a simple method for toxicity reduction of nanoparticles based on high molecular weight polyethylenimine used as gene delivery vectors

Investigation of siRNA-Loaded Polyethylenimine-Coated Human Serum Albumin Nanoparticle Complexes for the Treatment of Breast Cancer

Small interfering RNA (siRNA) molecules have great potential for developing into a future therapy for breast cancer. To overcome the issues related to rapid degradation and low transfection of naked siRNA, polyethylenimine (PEI)-coated human serum albumin (HSA) nanoparticles have been characterized and studied here for efficient siRNA delivery to the MCF-7 breast cancer cell line. The optimized nanoparticles were ~90 nm in size, carrying a surface charge of +26 mV and a polydispersity index (PDI) less than 0.25. The shape and morphology of the particles was studied using electron microscopy. A cytotoxicity assessment of the nanoparticles showed no correlation of cytotoxicity with HSA concentration, while using high molecular weight PEI (MW of 70 against 25 kDa) showed higher cytotoxicity. The optimal transfection achieved of fluorescin-tagged siRNA loaded into PEI-coated HSA nanoparticles was 61.66 ± 6.8%, prepared with 6.25 μg of PEI (25 kDa) added per mg of HSA and 20 mg/ml HSA, indicating that this nonviral vector may serve as a promising gene delivery system.

Poly(oligo-D-arginine) With Internal Disulfide Linkages as a Cytoplasm-sensitive Carrier for siRNA Delivery

Small interfering RNA (siRNA) has emerged as a therapeutic strategy for various diseases due to its target-specific gene silencing; however, its relatively high molecular weight, negative charge, and low stability hamper in vitro and in vivo applications. Approaches to overcome those drawbacks have relied on nonviral siRNA carriers based on cationic polymers or peptides. Nevertheless, cationic polymer-based siRNA carriers have yet to resolve intrinsic problems such as cytotoxicity and immunogenicity. An environment-sensitive carrier was recently proposed to enhance siRNA bioactivity and to reduce the carrier safety issues. Only a few studies, however, have shown cytoplasm-sensitive dissociation of the polyplex. In the present study, we clearly demonstrated decondensation of siRNA/poly(oligo-D-arginine) polyplex in the cytoplasm in response to intracellular glutathione (GSH) and the enhanced bioactivity of siRNA against VEGF (siVEGF) used as a model both in vitro and in an animal model. Reducible poly(oligo-D-arginine) (rPOA) rapidly dissociated in the cytoplasm, resulting in fast siRNA release to its target location while maintaining siRNA bioactivity both in vitro and in vivo.

Synthesis and properties of a novel biodegradable poly(ester amine) copolymer based on poly(L-lactide) and low molecular weight polyethylenimine for gene delivery

BackgroundGene therapy is a promising approach to the treatment of a wide range of diseases. The development of efficient and adequate gene delivery systems could be one of the most important factors. Polyethyleneimine, a cationic polymer, is one of the most successful and widely used vectors for nonviral transfection in vitro and in vivo.MethodsA novel biodegradable poly(ester amine) copolymer (PEA) was successfully prepared from low molecular weight polyethylenimine (PEI, 2000 Da) and poly(L-lactide) copolymers.ResultsAccording to the results of agarose gel electrophoresis, particle size and zeta potential measurement, and transfection efficiency, the PEA copolymers showed a good ability to condense plasmid DNA effectively into nanocomplexes with a small particle size (≤150 nm) and moderate zeta potential (≥10 mV) at an appropriate polymeric carrier/DNA weight ratio. Compared with high molecular weight PEI (25kDa), the PEA obtained showed relatively high gene transfection efficiency as well as low cytotoxicity in vitro.ConclusionThese results indicate that such PEA might have potential application as a gene delivery system.

Polycationic Polymers and Drugs: Investigations into Interactions between Acyclovir and Polymers

Interactions between pharmaceutical ingredients play an important role in the development of drug formulations. It was the aim of our present studies to investigate drug-polymer interactions. Interaction of the antiviral drug acyclovir with polyethylenimines, polyvinylamines and the non-ionic PVP was investigated using a modified equilibrium dialysis. The membrane was only permeable to free acyclovir, while polymers and acyclovir-polymer-associates did not pass through. Significant amounts of acyclovir were bound with the polyethylenimines. The formation of associates consisting of acyclovir and either PVP or polyvinylamine could not be demonstrated. In solutions of acyclovir and polyethylenimine (Mr=25,000) the amount of bound drug is increased with increasing concentration of acyclovir. Between 7.9 µg and 31.7 µg take part in the formation of associates. Differences in the osmotic pressure of the solutions do not play an important role in the permeation of acyclovir. In solutions containing acyclovir and high molecular weight polyethylenimine (Mr=750,000) the bound amount of drug increases with increasing acyclovir concentration up to c(0)=400 µg/100 ml. Further addition of free drug to the solution does not change the amount of bound drug significantly, due to possible limitations in the binding capacity. Molecular modeling investigations were performed. According to the calculations, about 85% of the interactions can be attributed to electrostatic interactions.

Cationic copolymers nanoparticles for nonviral gene vectors: Synthesis, characterization, and application in gene delivery

The major aim of nonviral delivery systems for gene therapy is to mediate high levels of gene expression with low toxicity. Nowadays, one of the most successful synthetic polycations used in gene delivery research is poly(ethylenimine) (PEI) in its high-molecular weight (HMW) branched form. However, PEI is not the ideal transfection agent in vivo because of its overwhelming cytotoxicity. To overcome its toxic effects with a minimal impact on transfection efficiency, PEI has been conjugated with several nonionic biocompatible polymers. Here, we describe the synthesis of nanosized particles consisting of HMW PEI (25 kDa) crosslinked with poly(epsilon-caprolactone) (PCL, 50-60 kDa), a biodegradable aliphatic polyester. PCL was modified by the insertion of glycidyl groups able to condense with the amines of PEI to chemically bind PEI onto PCL. The nanoparticles obtained have been characterized in relation to their physicochemical and biological properties, and the results are extremely promising in terms of low cell toxicity and high transfection efficiency. These biological effects might be related to the peculiar DNA binding to covalently connected polymeric nanoparticles, without the formation of entangled DNA/polymer-soluble aggregates.

Poly(ethylene glycol) analogs grafted with low molecular weight poly(ethylene imine) as non-viral gene vectors

A novel class of non-viral gene vectors consisting of low molecular weight poly(ethylene imine) (PEI) (molecular weight 800 Da) grafted onto degradable linear poly(ethylene glycol) (PEG) analogs was synthesized. First, a Michael addition reaction between poly(ethylene glycol) diacrylates (PEGDA) (molecular weight 258 Da) and d, l-dithiothreitol (DTT) was carried out to generate a linear polymer (PEG–DTT) having a terminal thiol, methacrylate and pendant hydroxyl functional groups. Five PEG–DTT analogs were synthesized by varying the molar ratio of diacrylates to thiols from 1.2:1 to 1:1.2. Then PEI (800 Da) was grafted onto the main chain of the PEG–DTTs using 1,1′-carbonyldiimidazole as the linker. The above reaction gave rise to a new class of non-viral gene vectors, (PEG–DTT)–g-PEI copolymers, which can effectively complex DNA to form nanoparticles. The molecular weights and structures of the copolymers were characterized by gel permeation chromatography, 1H nuclear magnetic resonance and Fourier transform infrared spectroscopy. The size of the nanoparticles was <200 nm and the surface charge of the nanoparticles, expressed as the zeta potential, was between +20 and +40 mV. Cytotoxicity assays showed that the copolymers exhibited much lower cytotoxicities than high molecular weight PEI (25 kDa). Transfection was performed in cultured HeLa, HepG2, MCF-7 and COS-7 cells. The copolymers showed higher transfection efficiencies than PEI (25 kDa) tested in four cell lines. The presence of serum (up to 30%) had no inhibitory effect on the transfection efficiency. These results indicate that this new class of non-viral gene vectors may be a promising gene carrier that is worth further investigation.

Immune responses to polyethylenimine delivered plasmid DNA encoding aFasciola giganticafatty acid binding protein in mice and rabbits

Fasciola gigantica fatty acid binding protein (FABP) was evaluated for evoking an effective immune response in mice and rabbits, when delivered as a DNA vaccine in muscle cells. Polyethylenimine (PEI), 25 kDa, branched cationic polymer was used as a delivery vehicle for this DNA in the muscle cells of mice and rabbits. Naked DNA evoked mixed Th1 and Th2 responses in mice. PEI condensed DNA, at amine nitrogen over DNA phosphate (N/P) ratios of 4, 6 and 8 and with various DNA concentrations, failed to evoke a significantly higher antibody response compared to naked DNA in mice. Similarly, the humoral immune response to naked DNA administration in rabbit thigh muscles was poor and no boosting of this antibody response on administration of DNA complexed to PEI was observed. On metacercarial challenge, rabbits failed to show any significant protective immune response in both the naked DNA and PEI-DNA immunized groups. Administration of PEI alone (12.5 mug) in mouse thigh muscles caused significant muscle cytotoxicity but condensation of DNA with PEI had less of a toxic effect on muscle cells, which was inversely related to the N/P ratio. Delivery of plasmid DNA encoding F. gigantica FABP by high molecular weight polyethylenimine (branched, 25 kDa) did not boost the effective immune response in both the animal species, which could either be attributed to cytotoxicity associated with this cationic polymer or muscle cells being unsuitable target cells for PEI condensed DNA delivery.

Layer-by-layer self assembly deposition and characterization of TiO2nanoparticles by using a short chain polycation

Using low molecular weight polyethylenimine (PEI), transparent thin films of TiO2 nanoparticles were prepared by layer-by-layer self assembly method. UV-visible spectrophotometry was employed in a quantitative manner to monitor the adsorbed mass of TiO2 and PEI after each dip cycle. The adsorption of both TiO2 and PEI showed a saturation dip time of 10 min. The effect of dip time on the growth mode and surface morphology was investigated by scanning electron microscopy (SEM) and non-contact atomic force microscopy (AFM). It was found that growth proceeds in the form of laterally broad islands in case of short dip times, and taller but laterally smaller islands in case of longer dip times. A model was proposed which describes the role of dip time on the lateral growth of TiO2 islands. Low molecular weight PEI resulted in around 25% less adsorption of PEI and TiO2 in comparison with high molecular weight PEI, but because of lower remaining ash, could be promising for dye-sensitized solar cell photoelectrode applications, in which removal of polyelectrolyte after the formation of thin film enhances the electrical properties and therefore the efficiency of solar cell.

Controlled cytoplasmic and nuclear localization of plasmid DNA and siRNA by differentially tailored polyethylenimine

To maximize therapeutic effects, targeted delivery of nucleic acids (e.g., DNA and RNA) in their appropriate intracellular targets is highly desirable. In this study, primary amines of a model polymeric nonviral carrier, polyethylenimine (PEI), at two molecular weights (0.8 and 25 kDa) were differentially ketalized (i.e., 17–96%) in order to explore the possibility of precisely modulating intracellular localization of plasmid DNA- and siRNA-containing polyplexes. The size of the polyplexes revealed that the ketalization ratios of 35 to 70% were found to be the most efficient in condensing nucleic acids with the ketalized low molecular weight PEI (LMW PEI), while high molecular weight PEI (HMW PEI) ketalized at the ratio of 23% condensed nucleic acids most efficiently. Ketalization of LMW PEI (up to 70%) enhanced transfection; however, ketalization of HMW PEI reduced its transfection capability. On the contrary, HMW PEI ketalized at 23 and 37% ratios showed significant RNA interference, while LMW PEI could not successfully inhibit gene expression regardless of ketalization ratios. The results were explained by confocal microscopic studies demonstrating that ketalization ratios, molecular weights of ketalized PEI, and types of nucleic acids complexed in the polyplexes play crucial roles in intracellular localization of nucleic acids/ketalized PEI polyplexes and affect DNA transfection and RNA interference efficiencies. All ketalized PEI showed negligible cytotoxicity. This study implies a feasibility of selectively localizing nucleic acids in their intracellular targets by employing differentially tailored polymeric gene carriers.