Nonviral Gene Delivery Carriers Research Articles

Studies on Guanidinated N-3-Aminopropyl Methacrylamide-N-2-Hydroxypropyl Methacrylamide Co-polymers as Gene Delivery Carrier

Guanidinated N-3-aminopropyl methacrylamide (APMA)-N-2-hydroxypropyl methacrylamide (HPMA) co-polymers were prepared and evaluated to develop novel non-viral gene transfection carriers. The co-polymers were synthesized via radical co-polymerization of APMA and HPMA followed by total guanidination of amino groups, which employed guanidinated APMA (GPMA) for increasing cell-penetrating and HPMA as the positive shielding content. The molecular weight of guanidinated APMA–HPMA co-polymers (GPMA–HPMA) was determined by static light scattering. Furthermore, cytotoxicity and transfection experiments of GPMA–HPMA/pDNA complexes were conducted. A significant decrease of their parent cytotoxicity and an efficient transfection at relative low charge ratios were observed. The cellular distribution of most GPMA–HPMA/pDNA complexes was partially localized in the nucleus, as indicated by confocal laser scanning microscopy. The guanidination strategy employed may lead to non-viral gene delivery carriers that combine satisfactory transfection efficiency and cytotoxicity, which contribute to their cell-penetrating ability.

Abstract B90: Nonviral delivery of apoptin for the treatment of brain tumor in a newly established brain tumor xenograft.

Abstract We established a brain tumor xenograft to examine the application of gene therapy utilizing a tumor selectively killing gene together with a nonviral gene delivery carrier to treat brain tumor. To do so, we recombined the therapeutic gene apoptin with the JDK vector and delivered it into human brain tumor cells (U87MG) using PAM-RG4 as the gene delivery carrier. Studies in vitro showed that the PAM-R G4/Apoptin polyplex exhibited particularly high transfection activity of over 40% based on fluorescence-activated cell sorting (FACS) analysis and lower cytotoxicity than other control agents. Also, TUNEL assay and DAPI staining verified that tumor cells had undergone apoptosis, which was induced by the apoptin gene. Caspase-3 activity was about two times higher in the therapeutic group. For in vivo studies, the PAM-R G4/Apoptin polyplex was injected into the tumor, which was induced by injecting U87MG cells into the left flank of nude mice and letting them grow to a certain size. The size of the tumor exponentially grew with time in the control groups whereas the treated group did not exhibit any tumor growth. H&E staining and EGFR immunohistochemistry confirmed the existence of the tumor in the control groups and showed that there was no tumor in the treated group. Furthermore, no specific edema, irritation or other kind of harm to the skin could be observed when the polyplex was injected. After reverse-transcript PCR analysis, to verify the expression of apoptin in vivo, TUNEL assay and DAPI staining were, again, utilized to confirm the event of apoptosis in the therapeutic group. These findings indicate that the PAM-RG4/Apoptin polyplex is a very strong candidate for brain tumor therapeutics, due to the synergistic effect of the carrier's high transfection efficiency in neuron cells and the gene's selective apoptosis-inducing activity in tumor cells. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2011 Nov 12-16; San Francisco, CA. Philadelphia (PA): AACR; Mol Cancer Ther 2011;10(11 Suppl):Abstract nr B90.

Efficient inhibition of an intraperitoneal xenograft model of human ovarian cancer by HSulf-1 gene delivered by biodegradable cationic heparin-polyethyleneimine nanogels

The HSulf-1 (heparan sulfate 6-O-endosulfatase1) gene is an important element that modulates the sulfation status of heparan sulfate proteoglycans (HSPGs), leading to the interference of HSPG-related signal transduction pathways. HSulf-1 plays a key role in regulating cell proliferation, tumorigenesis and angiogenesis. Recently, some studies have reported that HSulf-1 is a down-regulated gene in the majority of examined tumor types. In our present study, a recombinant plasmid DNA carrying HSulf-1-cDNA (pHSulf-1) was constructed. The antitumor effect of pHSulf-1 delivered by heparin-polyethyleneimine (HPEI) nanogels on human ovarian cancer and the possible mechanisms of the antitumor efficacy invivo were further investigated. Heparin-polyethyleneimine (HPEI) nanogels, as a new safe non-viral gene delivery carrier, were prepared to deliver the plasmid expressing HSulf-1 into HSulf-1-deficient SKOV3 human ovarian cancer cells invitro and invivo. pHSulf-1 could be efficiently transfected into SKOV3 ovarian cancer cells by HPEI nanogels invitro and invivo. Stable expression of HSulf-1 invitro and invivo was verified by reverse transcription polymerase chain reaction (RT-PCR) and Western blot analysis. Furthermore, a SKOV3 intraperitoneal ovarian carcinomatosis model was established to investigate the growth inhibition function of pHSulf-1 in nude mice. Tumor weight was measured. An anti-angiogenesis effect of pHSulf-1 invivo was detected by CD31 immunostaining and alginate-encapsulate tumor cell assay. Assessment of apoptotic cells and proliferation index in tumor tissues were performed by TUNEL assay and Ki‑67 immunostaining. Intraperitoneal injection of pHSulf-1/HPEI complexes efficiently reduced tumor weight by approximately 87% compared with control groups (P<0.01). Meanwhile, reduction in angiogenesis, inhibition of cell proliferation, as well as induction of tumor cell apoptosis were observed, without apparent systemic toxic effects. Collectively, these observations provide the first evidence that pHSulf-1 delivered by HPEI nanogels may become a promising therapeutic strategy against human ovarian cancer.

Suicidal gene therapy against tumor using reducible poly (oligo-d-arginine)

Summary Reducible poly(oligo-D-arginine) (rPOA) is a promising non-viral gene delivery carrier, providing lower cytotoxicity and higher gene expression efficiency compare to PEI. rPOA showed a higher level of HSV-TK gene expression in comparison with PEI in brain tumor cells and subsequently induced high cytotoxicity on tumor cells, in the presence of ganciclovir (GCV).

Synthesis and characterization of folate-poly(ethylene glycol) chitosan graft-polyethylenimine as a non-viral carrier for tumor-targeted gene delivery

The use of chitosan and chitosan derivatives for gene delivery is limited due to the low transfection efficiency and difficulty in transfecting into a variety of cell types, including some cancer cells overexpressing folate receptor (FRs). In order to solve this problem, folate (FA) and poly(ethylene glycol) (PEG) was conjugated to chitosan-graft-polyethylenimine (CHI-g-PEI) to enhance water-solubility and the transfection efficiency. In the present study, a cell specific targeting molecule FA was linked on PEG and then grafted the FA-PEG onto CHI-g-PEI. The FA-PEG-grafted CHI-g-PEI (FA-PEG-CHI-g-PEI) effectively condensed the plasmid DNA (pDNA) into nanoparticles with positive surface charge under the suitable nitrogen/phosphorus (N/P) ratio. In vitro , transfection efficiency of the FA-PEG-CHI-g-PEI /pDNA complex in 293T cells and LoVo cells (FRs over-expressing cell lines) increased with increasing N/P ratio under N/P = 15 and was more than 50%, but no significant difference in human lung carcinoma cells (A549) cells (FRs deficient cell lines). Importantly, in vivo luciferase expression showed that the efficiency of FA-PEG-CHI-g-PEI -mediated transfection (50 μg luciferase plasmid (pLuc), N/P ratio = 15) was comparable to that of adenovirus-mediated luciferase transduction (1 × 10 9 pfu) in melanomabearing mice. It was concluded that FA-PEG-CHI-g-PEI, which has improved transfection efficiency and FRs specificity in vitro and in vivo , may be useful in gene therapy. Key words : Folate poly(ethylene glycol)-chitosan-grafted-polyethylenimine (FA-PEG-CHI-g-PEI), gene transfection, non-virus vector, in vitro, in vivo

Synthesis and characterization of degradable multivalent cationic lipids with disulfide-bond spacers for gene delivery

Gene therapy provides powerful new approaches to curing a large variety of diseases, which are being explored in ongoing worldwide clinical trials. To overcome the limitations of viral gene delivery systems, synthetic nonviral vectors such as cationic liposomes (CLs) are desirable. However, improvements of their efficiency at reduced toxicity and a better understanding of their mechanism of action are required. We present the efficient synthesis of a series of degradable multivalent cationic lipids (CMVLn, n=2 to 5) containing a disulfide bond spacer between headgroup and lipophilic tails. This spacer is designed to be cleaved in the reducing milieu of the cytoplasm and thus decrease lipid toxicity. Small angle X-ray scattering demonstrates that the initially formed lamellar phase of CMVLn–DNA complexes completely disappears when reducing agents such as DTT or the biologically relevant reducing peptide glutathione are added to mimic the intracellular milieu. The CMVLs (n=3 to 5) exhibit reduced cytotoxicity and transfect mammalian cells with efficiencies comparable to those of highly efficient non-degradable analogs and benchmark commercial reagents such as Lipofectamine 2000. Thus, our results demonstrate that degradable disulfide spacers may be used to reduce the cytotoxicity of synthetic nonviral gene delivery carriers without compromising their transfection efficiency.

Comparison of ethanolamine/ethylenediamine-functionalized poly(glycidyl methacrylate) for efficient gene delivery

Cationic polymers with low cytotoxicity and high transfection efficiency have attracted considerable attention as non-viral carriers for gene delivery. Recently we reported that ethanolamine (EA)-functionalized poly(glycidyl methacrylate) (PGMA) (termed PGEA) vectors can have excellent transfection efficiency, while exhibiting very low toxicity. Herein different EA- and ethylenediamine (ED)-functionalized PGMA (termed PGEAED) vectors, as well as ED-functionalized PGMA (termed PGED) vectors, are proposed and compared for efficient gene delivery. In addition to the cationic pendant secondary amine and hydroxyl groups of PGEA, PGEAED, and PGED also contain flanking primary amine groups. PGEAED and PGED exhibited a substantially enhanced ability to condense pDNA into complex nanoparticles at the 100nm level with positive zeta potentials of about 30mV at nitrogen/phosphate (N/P) ratios of 10 or higher. More interestingly, no obvious change in the cytotoxicity of PGEAED was observed with a substantial increase in ED content. Moreover, the flanking primary amine groups induced by ED could be readily functionalized by glycyrrhetinic acid or cholic acid to improve the biophysical properties of the gene vectors.

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.

Flotillin-dependent endocytosis and a phagocytosis-like mechanism for cellular internalization of disulfide-based poly(amido amine)/DNA polyplexes

Extensive research is currently performed on designing safe and efficient non-viral carriers for gene delivery. To increase their efficiency, it is essential to have a thorough understanding of the mechanisms involved in cellular attachment, internalization and intracellular processing in target cells. In this work, we studied in vitro the cellular dynamics of polyplexes, composed of a newly developed bioreducible poly(amido amine) carrier, formed by polyaddition of N,N-cystamine bisacrylamide and 1-amino-4-butanol (p(CBA-ABOL)) on retinal pigment epithelium (RPE) cells, which are attractive targets for ocular gene therapy. We show that these net cationic p(CBA-ABOL)/DNA polyplexes require a charge-mediated attachment to the sulfate groups of cell surface heparan sulfate proteoglycans in order to be efficiently internalized. Secondly, we assessed the involvement of defined endocytic pathways in the internalization of the polyplexes in ARPE-19 cells by using a combination of endocytic inhibitors, RNAi depletion of endocytic proteins and live cell fluorescence colocalization microscopy. We found that the p(CBA-ABOL) polyplexes enter RPE cells both via flotillin-dependent endocytosis and a PAK1 dependent phagocytosis-like mechanism. The capacity of polyplexes to transfect cells was, however, primarily dependent on a flotillin-1-dependent endocytosis pathway.

Self-organized nanoparticles prepared by guanidine- and disulfide-modified chitosan as a gene delivery carrier

The use of membrane-permeable and intracellular reducible molecules for drug or gene delivery has gained increasing attention. In this work, chitosan (CS) was modified with extending arms consisting of disulfide spacers and arginine (Arg) residues (CS–SS–Arg) as a novel non-viral carrier for gene delivery. The chemical structure of synthesized CS–SS–Arg was characterized by proton nuclear magnetic resonance (1H-NMR) spectroscopy. Cleavage of disulfide spacers by glutathione (GSH) and dithiothreitol due to thiol-disulfide exchange reactions indicates that CS–SS–Arg is likely reducible in cytoplasm. The CS–SS–Arg was allowed to condense green fluorescent protein (GFP) DNA to form self-organized nanoparticles with a diameter of 130 nm and zeta potential of 35 mV. The DNA was released from CS–SS–Arg/DNA nanoparticles over time in the presence of GSH. Transfection studies by confocal laser scanning microscopy demonstrate that CS–SS–Arg/DNA nanoparticles had a 48-h delay of GFP expression in human embryonic kidney 293 (HEK 293) cells; however, the GFP expression level was higher and more sustainable than that of its unmodified CS counterpart. These analytical results suggest that the Arg-rich bioreducible CS–SS–Arg/DNA nanoparticles are promising as a carrier for gene delivery.

Nonviral gene delivery to human ovarian cancer cells using arginine-grafted PAMAM dendrimer

Background: A specific and effective strategy is in demand to treat ovarian cancer successfully. Epidermal growth factor receptor (EGFR) is highly expressed in ovarian cancer, and thus EGFR antisense gene therapy can be a potential therapeutic strategy. Method: l-Arginine-grafted-polyamidoamine dendrimer (PAMAM-Arg) has been reported to be a novel nonviral gene delivery carrier. Therefore, the ability of PAMAM-Arg in transferring a luciferase gene to ovarian carcinoma SK-OV3 cells has been examined, and the cytotoxicity of the cationic polymer has been investigated. In addition, the suppression of cell proliferation has been evaluated by transferring an EGFR antisense gene to SK-OV3 cells using PAMAM-Arg. Polyethyleneimine (PEI) 25K was used as a positive control. Results: As a result, in vitro gene transfection efficiency of PAMAM-Arg was enhanced with increasing transfection time and N/P ratios. PAMAM-Arg transferred the luciferase gene into cells more efficiently than PEI. In addition, PAMAM-Arg was minimally toxic to the cells whereas PEI 25K was highly toxic. The polyplexes formed by the EGFR antisense gene and PAMAM-Arg significantly reduced thymidine incorporation into the cells suggesting the suppression of cancer cell proliferation. Conclusion: These results suggest that a PAMAM-Arg/EGFR antisense gene complex can be used as a safe and efficient therapeutic agent for cancer gene therapy.

PDNA condensation capacity and in vitro gene delivery properties of cationic solid lipid nanoparticles

Cationic solid lipid nanoparticles (SLN) are promising nonviral gene delivery carriers suitable for systemic administration. The objective of this study was to investigate the relationship between the composition of cationic SLN and their ability to condense plasmid DNA (pDNA) and to transfer it in neuroblastoma cells. The SLN were prepared by using stearic acid and stearylamine as lipid core along with Esterquart 1 (EQ1) or Protamine obtaining two samples (SLN-EQ1 and SLN-Protamine, respectively). The cationic SLN were freeze-dried after preparation and their physical–chemical properties, including the surface composition and the transfection efficiency were investigated. The results showed that the two samples had similar size, zeta potential and pDNA binding properties but SLN-Protamine were able to condense pDNA more efficaciously than SLN-EQ1 forming smaller and less positive complexes. SLN-Protamine:pDNA complexes demonstrated to be less cytotoxic and more efficient in the transfection of Na1300 cell line than SLN-EQ1:pDNA. These findings were attributed to the different surface composition of the two samples and in particular to the localization of the Protamine on the surface of the particle while EQ1 in the lipid core. In conclusion the results here suggest that not only the z-potential but also the surface composition may affect the pDNA condensation proprieties and thus the transfection efficiency of nonviral gene nanocarriers.

Thymine, adenine and lipoamino acid based gene delivery systems

A novel class of thymine, adenine and lipoamino acid based non-viral carriers for gene delivery has been developed. Their ability to bind to DNA by hydrogen bonding was confirmed by NMR diffusion, isothermal titration calorimetry and transmission electron microscopy experiments.

Development of Non-Viral Gene Delivery Carriers for Ischemic Heart Disease (IHD)

Ischemic heart disease (IHD) or coronary artery disease (CAD) is a leading cause of death in the United States resulting in a major financial burden to the health care system and is projected to be one of the main contributors to disability by 2020. The poor prognosis of IHD is directly related to a build-up of atherosclerotic plaque that produces narrowing of the coronary artery lumen. The rupture of the artery and/or narrowing of the artery lumen results in myocardial ischemia, which can lead to myocardial infarction or death of the heart muscle tissue. Current treatments include bypass surgery, angioplasty, stent implantation, and pharmacotherapy but unfortunately many patients with IHD remain refractory to pharmacological treatments and are unsuitable candidates for surgical interventions. Also, restenosis of the vessel lumen due to neointimal hyperplasia is a recurrent problem. Gene therapy is a promising alternative to traditional treatment strategies since the delivery of angiogenic cytokines can stimulate neovascularisation in a process known as therapeutic angiogenesis. To this end, we have designed, synthesized, and characterized novel biodegradable polymeric carrier systems for the delivery of therapeutic angiogenic plasmids. The polymers were found to have a MW of ∼3.2 kDa. A gel retardation assay showed condensation of DNA at N/P ratios higher than 20/1. The particle sizes of the polymer/DNA complexes were 100-231 nm with surface charges of 0.8-20 mV. Preliminary data with the reporter gene luciferase showed that the complexes produced significantly higher transfection efficiencies and lower cytotoxicities in several cell lines as compared to the control. Thus, these novel nonviral carriers are very efficient, versatile, and biocompatible polymers for nonviral gene delivery.

Impact of Molecular Weight in Four-Branched Star Vectors with Narrow Molecular Weight Distribution on Gene Delivery Efficiency

A series of star-shaped cationic polymers, termed star vectors (SVs), has been developed as effective nonviral gene delivery carriers. In this study, we separated SVs into several fractions having different molecular weights with very narrow molecular weight distributions in order to examine in detail the influence of the molecular weight of the SVs on the gene transfection efficiency. As a model compound for several types of SVs, 4-branched poly(N,N-dimethylaminopropyl acrylamide) having a molecular weight (M(n)) of approximately 35 kDa and polydispersity of 1.6 was prepared by iniferter-based radical polymerization. The SVs were separated using size-exclusion chromatography to obtain seven fractions having M(n) ranging from 27 kDa to 73 kDa with polydispersity ranging from 1.1 to 1.2. All the fractionated SVs have similar pH of 10.2-10.4 and were able to interact with and condense luciferase-encoding plasmid deoxyribonucleic acid (DNA) to yield SV/DNA polyplexes. A water-soluble tetrazolium-1 (WST) assay showed that all SVs had minimal cellular cytotoxicity under an N/P charge ratio of 10. The critical micellar concentration decreased with an increase in the M(n) of the fractionated SVs; however, the particle size of the polyplexes, exclusion activity of ethidium bromide, and zeta-potential of the polyplexes increased. An in vitro evaluation using COS-1 cells at an N/P ratio of 10 showed that transfection activity increased almost linearly with M(n). The highest transfection activity was obtained for SVs with the highest M(n) (73 kDa), which was over 7 times that for the SVs with the lowest M(n) (27 kDa), the nonfractionated original SV, or PEI standard. The transfection efficiency was more correlated with the amphiphilicity or hydrophobicity of the SVs and the surface potential and condensate density of the polyplexes than with the particle size.

Synergistic Effect of Low Cytotoxic Linear Polyethylenimine and Multiarm Polyethylene Glycol: Study of Physicochemical Properties and In Vitro Gene Transfection

Novel star-shaped copolymers consisting of multiarm polyethylene glycol and low molecular weight linear polyethylenimines (MAPEG-LPEIs) with a high transfection efficiency and low cytotoxicity were designed and synthesized as nonviral gene delivery carriers. The cationic polymers were prepared by conjugating low molecular weight linear PEI (2.5 kDa) to six-arm PEG-NHS (10 kDa) in two different compositions. Two copolymers, MAPEG-LPEI(3) and MAPEG-LPEI(6) with molecular weights of 17.5 kDa and 25 kDa respectively, were synthesized. The MAPEG-LPEI(3)/pDNA and MAPEG-LPEI(6)/pDNA polyplexes are stably dispersed in aqueous media with a narrowly distributed size range of <200 nm as determined by dynamic light scattering. Furthermore, these polyplexes showed different surface charges depending upon the relative proportion of MAPEG and LPEI. Moreover, these polyplexes can protect pDNA from enzymatic degradation in serum containing media up to 24 h. These polyplexes were able to efficiently transfect luciferase-coded reporter gene into HeLa cancer cells and showed considerable gene transfection efficacy even in 50% serum-conditioned media in vitro. MAPEG-LPEI(6) exhibited higher transfection activity than that of MAPEG-LPEI(3) at the same weight ratios. Furthermore, MAPEG-LPEI/pDNA polyplexes were less toxic than LPEI/pDNA complexes as determined by MTT assay. These favorable results could be attributed to the combined effect of low molecular weight LPEI and multiarm PEG. The special structural features of the multiarm star-shaped central PEG core play an important role in achieving higher transfection efficiency as it imparts higher charge density to polyplexes and prevents the unwanted aggregation of the smaller polyplex particles. These two important factors contributed toward enhanced gene transfection. On the other hand, LPEI provides low cytotoxicity and effective complexation with pDNA in the designed architecture. Therefore it is possible to achieve enhanced gene transfection by using these two components, namely, pivotal multiarm PEG core and LPEI, in optimal ratio as observed in the case of MAPEG-LPEI(6).

Effective Polyethyleneimine-Mediated Gene Transfer into Zebrafish Cells

Polyethyleneimine (PEI) has been broadly studied as a leading nonviral gene delivery carrier because of its relatively high transfection efficiency in a wide range of cell types. Here, we report gene transfer in zebrafish cells (ZF4) using PEI as a gene carrier and lipofectamine as a control. Formations of PEI-DNA complexes were characterized by a series of measurements. The particle size of PEI-DNA complexes decreased from 274 to 132 nm, the surface charge gradually increased from -26 to 29 mV, and the cytotoxicity for zebrafish cells was observed with increasing proportion of PEI. Gel retardation assay showed that DNA was completely bound by PEI with a negative-to-positive charge ratio of 4. It was observed by transmission electron microscopy that the morphology of PEI-DNA complexes was spherical with smooth surfaces. Flow cytometry revealed that the optimum transfection efficiency (27%) mediated by PEI was obtained at an negative-to-positive charge ratio of 8, which was higher than that with lipofectamine. Luciferase activity assay confirmed the increase in reporter gene expression probably due to a more efficient formation of complex between DNA and PEI than DNA and lipofectamine. In conclusion, our study demonstrates that PEI may be applied as an effective gene carrier to mediate gene transfer into zebrafish cells.

Comb-Shaped Copolymers Composed of Hydroxypropyl Cellulose Backbones and Cationic Poly((2-dimethyl amino)ethyl methacrylate) Side Chains for Gene Delivery

Cationic polymers have been of interest and importance as nonviral gene delivery carriers. Herein, well-defined comb-shaped cationic copolymers (HPDs) composed of long biocompatible hydroxypropyl cellulose (or HPC) backbones and short poly((2-dimethyl amino)ethyl methacrylate) (or P(DMAEMA)) side chains were prepared as gene vectors via atom transfer radical polymerization (ATRP) from the bromoisobutyryl-terminated HPC biopolymers. The P(DMAEMA) side chains of HPDs can be further partially quaternized to produce the quaternary ammonium HPDs (QHPDs). HPDs and QHPDs were assessed in vitro for nonviral gene delivery. HPDs exhibit much lower cytotoxicity and better gene transfection yield than high-molecular-weight P(DMAEMA) homopolymers. QHPDs exhibit a stronger ability to complex pDNA, due to increased surface cationic charges. Thus, the approach to well-defined comb-shaped cationic copolymers provides a versatile means for tailoring the functional structure of nonviral gene vectors to meet the requirements of strong DNA-condensing ability and high transfection capability.

Analysis of the Relationship between the Molecular Weight and Transfection Efficiency/Cytotoxicity of Poly-L-arginine on a Mammalian Cell Line

which can control the translation of a specific protein, the development of the method for efficient and safe delivery of DNA and RNA has been one of the main objectives in the biological and medical science. Therefore, many chemists has been concentrated their efforts to synthesize the non-viral gene delivery carriers such as cationic lipids,

Evaluation of the Binding Affinity and RNA Interference of Low-molecular-weight Chitosan/siRNA Complexes Using an Imaging System

Chitosan is one of the attractive non-viral carriers for gene delivery including siRNA. However, common chitosan, which has a relatively high molecular weight, is insoluble in water, which might make it difficult to apply clinically. In this study, we investigated the efficacy of low-molecular-weight chitosan (LMWC), which is soluble in water, as a carrier for siRNA delivery. To evaluate the binding affinity and RNA interference (RNAi) of LMWC/siRNA complexes, a multi-well imaging system (IVIS) was adapted. CT26 cells stably expressing firefly luciferase (CT26/Luc cells) were established to evaluate RNAi. Evaluation of RNAi using lipofectamine(TM) 2000 was carried out by employing a luminometer with cell lysis and IVIS without cell lysis. The results were closely correlated, suggesting the advantages of the multi-well imaging system regarding screening, the visualization of results, and nondestructive evaluation. Fluorescence generated by ethidium bromide intercalated in the double strand of siRNA was markedly quenched at a higher ratio of LMWC to siRNA (N/P) and lower pH. Evaluation of the particle size and zeta potential of LMWC/siRNA complexes also indicated the higher binding affinity of LMWC with siRNA. At N/P=300 and pH 6.5, which satisfied the high-level binding affinity of LMWC with siRNA, significantly lower luminescence was detected in CT26/Luc cells treated with LMWC/siRNA compared with those treated with LMWC alone, suggesting the presence of RNAi. These results suggested that LMWC may be an effective carrier for siRNA delivery, and that the multi-well imaging system may be a powerful tool to evaluate the binding affinity and RNAi.