Galactosylated chitosan-graft-polyethylenimine as a gene carrier for hepatocyte targeting

Suppression of lung cancer progression by biocompatible glycerol triacrylate-spermine-mediated delivery of shAkt1

BACKGROUND

Polyethylenimine (PEI)-based nonviral gene-delivery systems are commonly employed because of their high transfection efficiency. However, the toxic nature of PEI is a significant obstacle in clinical gene therapy. In this study, we developed biocompatible glycerol triacrylate-spermine (GT-SPE) polyspermine as a nanosized gene carrier for potential lung cancer gene therapy.

METHODS

The GT-SPE was synthesized using the Michael addition reaction between GT and SPE. The molecular weight was characterized using gel permeability chromatography multiangle laser light scattering and the composition of the polymer was analyzed using proton nuclear magnetic resonance.

RESULTS

The GT-SPE successfully protected the DNA from nucleases. The average particle size of the GT-SPE was 121 nm with a zeta potential of +23.45 mV. The GT-SPE was found to be less toxic than PEI for various cell lines, as well as for a murine model. Finally, our results showed that the GT-SPE/small hairpin Akt1 (shAkt1) complex suppressed lung tumorigenesis in a K-ras(LA1) lung cancer mice model by inducing apoptosis through the Akt signaling pathway and cell cycle arrest. Aerosol delivered GT-SPE/shAkt1, which reduced matrix metalloproteinase-9 activity and suppressed the expression levels of proliferating cell nuclear antigen, as well as vascular endothelial growth factors and CD31, which are known proliferation and angiogenesis markers, respectively.

CONCLUSION

Our data suggest that GT-SPE may be a candidate for short hairpin-shaped RNA-based aerosol lung cancer gene therapy.

DEGRADABLE POLYETHYLENIMINE DERIVATIVES AS GENE CARRIERS

Gene therapy is a treatment for inborn and acquired diseases, although the development of safe and effective gene delivery system is a great challenge to make a gene therapy a success. Viral vectors have been used in a majority of clinics because of their high transfection efficiency in vitro and in vivo. However, their use has been limited because of several drawbacks, such as induction of immune response, recombination of wild-type viruses, limitation in the size of inserted gene, and difficulty in large-scale production. Nonviral vectors have been widely proposed safe alternatives to viral vectors because they have low immunogenicity, flexibility in the size of gene to be delivered, cell targetibility, and easy scalability of production, although they have low transfection efficiency compared to viral vectors. Among nonviral vectors, polyethylenimine (PEI) has been widely used as a standard gene carriers due to its high pH-buffering capacity for endosomal escape although high-molecular-weight PEI is too toxic owing to non-degradability. Recently, many types of degradable PEI have been studied due to high transfection efficiency with lower cytotoxicity. This review explains recent progress on the development of degradable PEIs as nonviral vectors. The present paper summarizes the transfection efficiency of DNA or silencing efficiency of small interfering RNA (siRNA) based on the kinds of degradable linkage between low PEI and crosslinkers. Degradable linkages, such as ester, disulfide, imines, carbamate, amide and ketal in the degradable PEIs are covered.

Chitosan-graft-branched polyethylenimine copolymers: influence of degree of grafting on transfection behavior

Background

Successful non-viral gene delivery currently requires compromises to achieve useful transfection levels while minimizing toxicity. Despite high molecular weight (MW) branched polyethylenimine (bPEI) is considered the gold standard polymeric transfectant, it suffers from high cytotoxicity. Inversely, its low MW counterpart is less toxic and effective in transfection. Moreover, chitosan is a highly biocompatible and biodegradable polymer but characterized by very low transfection efficiency. In this scenario, a straightforward approach widely exploited to develop effective transfectants relies on the synthesis of chitosan-graft-low MW bPEIs (Chi-g-bPEI_x) but, despite the vast amount of work that has been done in developing promising polymeric assemblies, the possible influence of the degree of grafting on the overall behavior of copolymers for gene delivery has been largely overlooked.

Methodology/Principal Findings

With the aim of providing a comprehensive evaluation of the pivotal role of the degree of grafting in modulating the overall transfection effectiveness of copolymeric vectors, we have synthesized seven Chi-g-bPEI_x derivatives with a variable amount of bPEI grafts (minimum: 0.6%; maximum: 8.8%). Along the Chi-g-bPEI_x series, the higher the degree of grafting, the greater the ζ-potential and the cytotoxicity of the resulting polyplexes. Most important, in all cell lines tested the intermediate degree of grafting of 2.7% conferred low cytotoxicity and higher transfection efficiency compared to other Chi-g-bPEI_x copolymers. We emphasize that, in transfection experiments carried out in primary articular chondrocytes, Chi-g-bPEI_2.7% was as effective as and less cytotoxic than the gold standard 25 kDa bPEI.

Conclusions/Significance

This work underlines for the first time the pivotal role of the degree of grafting in modulating the overall transfection effectiveness of Chi-g-bPEI_x copolymers. Crucially, we have demonstrated that, along the copolymer series, the fine tuning of the degree of grafting directly affected the overall charge of polyplexes and, altogether, had a direct effect on cytotoxicity.

Nucleic-acid based gene therapeutics: delivery challenges and modular design of nonviral gene carriers and expression cassettes to overcome intracellular barriers for sustained targeted expression

The delivery of nucleic acid molecules into cells to alter physiological functions at the genetic level is a powerful approach to treat a wide range of inherited and acquired disorders. Biocompatible materials such as cationic polymers, lipids, and peptides are being explored as safer alternatives to viral gene carriers. However, the comparatively low efficiency of nonviral carriers currently hampers their translation into clinical settings. Controlling the size and stability of carrier/nucleic acid complexes is one of the primary hurdles as the physicochemical properties of the complexes can define the uptake pathways, which dictate intracellular routing, endosomal processing, and nucleocytoplasmic transport. In addition to nuclear import, subnuclear trafficking, posttranscriptional events, and immune responses can further limit transfection efficiency. Chemical moieties, reactive linkers or signal peptide have been conjugated to carriers to prevent aggregation, induce membrane destabilization and localize to subcellular compartments. Genetic elements can be inserted into the expression cassette to facilitate nuclear targeting, delimit expression to targeted tissue, and modulate transgene expression. The modular option afforded by both gene carriers and expression cassettes provides a two-tier multicomponent delivery system that can be optimized for targeted gene delivery in a variety of settings.

Suppression of tumor growth in H-ras12V liver cancer mice by delivery of programmed cell death protein 4 using galactosylated poly(ethylene glycol)-chitosan-graft-spermine

Non-viral gene delivery systems based on polyethyleneimine (PEI) are efficient due to their proton-sponge effect within endosomes, but they have poor physical characteristics such as slow dissociation, cytotoxicity, and non targeted gene delivery. To overcome many of the problems associated with PEI, we synthesized a galactosylated poly(ethylene glycol)-chitosan-graft-spermine (GPCS) copolymer with low cytotoxicity and optimal gene delivery to hepatocytes using an amide bond between galactosylated poly(ethylene glycol) and chitosan-graft-spermine. The GPCS copolymer formed complexes with plasmid DNA, and the GPCS/DNA complexes had well-formed spherical shapes. The GPCS/DNA complexes were nanoscale size with homogenous size distribution and a positive zeta potential by dynamic light scattering (DLS). The GPCS copolymer had lower cytotoxicity than that of PEI 25K in HepG2, HeLa, and A549 cell lines at various concentrations and showed good hepatocyte-targeting ability. Furthermore, GPCS/DNA complexes showed higher levels of GFP expression in the liver in model mice after intravenous injection than naked DNA and metoxy-poly(ethylene glycol)-chitosan-graft-spermine as controls without remarkable fibrosis, inflammation, lipidosis, or necrosis. In a tumor suppression study, an intravenous injection of the GPCS/Pdcd4 complexes significantly suppressed tumor growth, activated apoptosis, and suppressed proliferation and angiogenesis in liver tumor-bearing H-ras12V mice. Our results indicate that the GPCS copolymer has potential as a hepatocyte-targeting gene carrier.

Hepatocyte-targeted psiRNA delivery mediated by galactosylated poly(ethylene glycol)-graft-polyethylenimine in vitro

Gene silencing in liver disease could be achieved by delivering siRNA with nonviral vectors. However, the transfection efficiency of plasmid siRNA (psiRNA) applied through this approach in hepatocytes is generally low. Based on the fact that the asialoglycoprotein receptors present on hepatocytes can recognize galactose, we synthesized galactosylated poly(ethylene glycol)-graft-polyethylenimine (Gal-PEG-PEI) as a nonviral psiRNA carrier for hepatocyte targeting. Our results indicate that 0.2% (molar percentage) of amine groups of PEI was conjugated with PEG having galactose on its distal end. Increasing the molar ratios of Gal-PEG-PEI to psiRNA in complexation led to a decrease in particle size but an increase in zeta potential of complexes. The transfection efficiency of nanocomplexes, that is, Gal-PEG-PEI/psiRNA, in HepG2 cell line depends on the N/P value, which reflects the molar ratio of Gal-PEG-PEI to psiRNA in the complex. The highest transfection efficiency was 37.34%, which was obtained at N/P 8. At the same N/P value, the transfection efficiency with the nontargeting PEG-PEI/psiRNA or Lipofectamine 2000/psiRNA was much lower. The transfection efficiency of Gal-PEG-PEI/psiRNA dropped to 3.60% from 37.34% after an excessive amount of free galactose was added into the medium for HepG2 cell incubation. By contrast, the similar phenomenon was observed neither when using PEG-PEI or Lipofectamine 2000 as a delivery vector nor in human embryonic kidney 293 cell line lacking ASGR. Real-time PCR analysis and western blot assay demonstrate that the knockdown of HLA-E gene expression by psiRNA/Gal-PEG-PEI (N/P 8) can reach about 60% in HepG2 cells after a 48-h transfection.

Spermine grafted galactosylated chitosan for improved nanoparticle mediated gene delivery

Despite multitude of beneficial features, chitosan has poor water solubility and transfection ability which affect its gene delivery efficacy. The two features are improved when certain chemical modifications are incorporated into the chitosan parent backbone. This strategy is adopted here, by coupling galactose and spermine into the chitosan backbone. The conjugation was determined with FTIR and (1)H NMR and nanoparticle morphology was assessed by TEM and AFM techniques. Particle size, zeta potential, buffering capacity and DNA binding ability gave encouraging result of enhanced solubility and stability. In vitro studies of GCSM in HepG2 cell lines displayed low cytotoxicity and improved transfection. We also identified the preference of receptor mediated internalization for nanoparticles cellular uptake by treating with cellular uptake inhibitors. The results evidently led us to comprehend that galactosylated chitosan-g-spermine could be considered as a promising chitosan derivative for conducting nanoparticle mediated gene delivery.

Chitosan-graft-spermine as a gene carrier in vitro and in vivo

Chitosan has been proposed as a non-viral gene carrier because of its biodegradable and biocompatible cationic polymeric properties. However, the transfection efficiency of chitosan-DNA complexes is still too low for clinical trials. To improve transfection efficiency, we prepared a chitosan-graft-spermine (CHI-g-SPE) copolymer by an imine reaction between periodate-oxidized chitosan and spermine. The CHI-g-SPE copolymer was complexed with plasmid DNA in various copolymer-DNA weight ratios, and the complexes were characterized. The CHI-g-SPE copolymer showed good DNA binding ability and high protection of DNA from nuclease attack. The CHI-g-SPE/DNA complexes had well-formed spherical shapes and a nanoscale size with homogenous size distribution. The CHI-g-SPE copolymer had low cytotoxicity and CHI-g-SPE/DNA complexes showed transfection efficiency that was enhanced over that of chitosan-DNA. Furthermore, aerosol delivery of CHI-g-SPE/GFP complexes showed higher GFP expression compared with chitosan/GFP complexes, without toxicity. Our results indicate that the CHI-g-SPE copolymer has potential as a gene carrier.

Surface engineered Poly(lactide-co-glycolide) nanoparticles for intracellular delivery: uptake and cytotoxicity--a confocal raman microscopic study

Confocal Raman Microscopy (CRM) is used to study the cell internalization of poly(lactide-co-glycolide) (PLGA) nanoparticles (NPs) fabricated by emulsion techniques with either poly(ethylene imine) (PEI) or bovine serum albumin (BSA) as surface stabilizers. HepG2 cells were exposed to PEI and BSA stabilized PLGA NPs. Spontaneous Confocal Raman Spectra taken in one and the same spot of exposed cells showed bands arising from the cellular environment as well as bands characteristic for PLGA, proving that the PLGA NPs have been internalized. It was found that PLGA NPs preferentially colocalize with lipid bodies. The results from Raman spectroscopy are compared with flow cytometry and confocal scanning laser microscopy (CLSM) data. The advantages of CRM as a label-free technique over flow cytometry and CLSM are discussed. Additionally, cell viability studies by means of quick cell counting solution and MTT tests in several cell lines show a generally low toxicity for both PEI and BSA stabilized PLGA NPs, with BSA stabilized PLGA NPs having an even lower toxicity than PEI stabilized.

Galactosylated poly(2-(2-aminoethyoxy)ethoxy)phosphazene/DNA complex nanoparticles: in vitro and in vivo evaluation for gene delivery

To achieve efficient gene delivery to the tumor after intravenous administration, biodegradable poly(2-(2-aminoethyoxy)ethoxy)phosphazene (PAEP) was modified by lactobionic acid, bearing a galactose group as a targeting ligand. Galactosylated poly(2-(2-aminoethyoxy)ethoxy)phosphazene (Gal-PAEP) with 4.9% substitution degree of galactose could condense pDNA into nanoparticles with a size around 130 nm at the polymer/DNA ratio (N/P) of 2-40. For BEL-7402 cells, the in vitro transfection efficiency of gal-PAEP/DNA complex nanoparticles (gal-PACNs) was much higher than that of the PAEP/DNA complex nanoparticles (PACNs). MTT assay indicated that the cytotoxicity of PACNs significantly decreased after conjugating with the galactose moiety. Gal-PACNs displayed the selective gene expression in the tumor and liver with relatively low gene expression in the lung or other organs compared with PACNs. These results suggested that gal-PACNs could be a promising targeting gene carrier to deliver a therapeutic gene in future.

Targeted molecular imaging of VEGF receptors overexpressed in ischemic microvasculature using chitosan-DC101 conjugates

Expression of vascular endothelial growth factor receptors (VEGFRs) increases in ischemic muscles, and thus, VEGFR could potentially be used as marker to detect ischemia. Here, we investigated whether (99m)Tc or Cy5.5-labeled chitosan-DC101 conjugates could identify VEGFR-2 overexpressed in ischemia. To this end, chitosan was conjugated with the DC101 antibody and Cy5.5, FITC, or the HYNIC chelator for (99m)Tc-labeling. Targeting of the conjugate was evaluated in vitro and in vivo through cell-binding studies and gamma/optical imaging, respectively. A hindlimb ischemic mouse model was surgically created by femoral artery occlusion. The chitosan-DC101 conjugates exhibited VEGFR-selective cell binding properties as determined by both confocal microscopy and flow cytometry. At postoperative times of 2, 12, and 24 h, (99m)Tc or Cy5.5-labeled chitosan-DC101 conjugates were intravenously injected into the mice, and gamma/optical imaging studies were conducted at 1 or 3 h. Both the gamma and optical imaging results indicated a significantly higher uptake in ischemic muscles when compared with the contralateral nonischemic muscle. Further, semiquantitative analysis of scintigraphic imaging data revealed that the ischemic to contralateral limb ratio was 4.5 +/- 0.25 at 24 h postoperation. Western blotting analysis confirmed VEGFR expression in the ischemic muscle. In conclusion, we believe that (99m)Tc or Cy5.5-labeled chitosan-DC101 conjugates have the potential to be useful as VEGFR-2-targeted imaging agents for monitoring ischemia.

Preparation and evaluation of N-caproyl chitosan nanoparticles surface modified with glycyrrhizin for hepatocyte targeting

BACKGROUND

The development of an efficient targeted drug delivery system into cells is an important subject for the advancement of drug carriers. In this study, a novel hepatocyte-targeted delivery system with glycyrrhizin (GL) surface modification based on N-caproyl chitosan (CCS) has been developed.

METHOD

CCS was synthesized by acylation of amino group of chitosan, and GL was oxidized to be conjugated to the surface of N-caproyl chitosan nanoparticles (CCS-NPs-GL). The synthesized nanoparticles were first characterized for their morphology, particle size, zeta potential, in vitro stability in plasma, tissue distribution, and hepatocyte-targeting uptake in vivo.

RESULTS

The obtained results showed that the spherical and discrete nanoparticles prepared with oxidized GL/CCS ratio of 0.14:1 (w/w) exhibited a positive electrical charge and associated adriamycin quite efficiently (association efficiency: 87.5%). The prepared nanoparticles also possessed dimensional and GL surface-binding stability and slow release property in plasma in vitro. The biodistribution of these particles after intravenous injections in mice revealed accumulating drug concentrations in the liver, spleen, and lungs while decreasing drug concentrations in the heart and kidney. The content of adriamycin-loaded CCS-NPs-GL in the liver was 1.6 times higher than that of non-GL-modified CCS-NPs. Furthermore, in vivo uptake of CCS-NPs-GL by rat hepatocytes showed 2.1 times higher nanoparticle uptake compared with non-GL-modified CCS-NPs, which suggested that CCS-NPs-GL were preferentially distributed in hepatocytes by a ligand-receptor interaction.

CONCLUSION

This article indicated that CCS-NPs-GL was a stable and effective drug delivery vehicle for hepatocyte targeting.

Chitosan-based systems for molecular imaging

Molecular imaging enables the non-invasive assessment of biological and biochemical processes in living subjects. Such technologies therefore have the potential to enhance our understanding of disease and drug activity during preclinical and clinical drug development. Molecular imaging allows a repetitive and non-invasive study of the same living subject using identical or alternative biological imaging assays at different time points, thus harnessing the statistical power of longitudinal studies, and reducing the number of animals required and cost. Chitosan is a hydrophilic and non-antigenic biopolymer and has a low toxicity toward mammalian cells. Hence, it has great potential as a biomaterial because of its excellent biocompatibility. Conjugated to additional materials, chitosan composites result in a new class of biomaterials that possess mechanical, physicochemical and functional properties, which have potential for use in advanced biomedical imaging applications. The present review will discuss the strengths, limitations and challenges of molecular imaging as well as applications of chitosan nanoparticles in the field of molecular imaging.

Carbohydrate polymers for nonviral nucleic acid delivery

Carbohydrates have been investigated and developed as delivery vehicles for shuttling nucleic acids into cells. In this review, we present the state of the art in carbohydrate-based polymeric vehicles for nucleic acid delivery, with the focus on the recent successes in preclinical models, both in vitro and in vivo. Polymeric scaffolds based on the natural polysaccharides chitosan, hyaluronan, pullulan, dextran, and schizophyllan each have unique properties and potential for modification, and these results are discussed with the focus on facile synthetic routes and favorable performance in biological systems. Many of these carbohydrates have been used to develop alternative types of biomaterials for nucleic acid delivery to typical polyplexes, and these novel materials are discussed. Also presented are polymeric vehicles that incorporate copolymerized carbohydrates into polymer backbones based on polyethylenimine and polylysine and their effect on transfection and biocompatibility. Unique scaffolds, such as clusters and polymers based on cyclodextrin (CD), are also discussed, with the focus on recent successes in vivo and in the clinic. These results are presented with the emphasis on the role of carbohydrate and charge on transfection. Use of carbohydrates as molecular recognition ligands for cell-type specific delivery is also briefly reviewed. We contend that carbohydrates have contributed significantly to progress in the field of non-viral DNA delivery, and these new discoveries are impactful for developing new vehicles and materials for treatment of human disease.

Degradable polyethylenimines as DNA and small interfering RNA carriers

Gene therapy is a powerful approach in the treatment of a wide range of both inherited and acquired diseases. Nonviral delivery systems have been proposed as safer alternatives to viral vectors because they avoid the inherent immunogenicity and production problems that are seen when viral systems are used. Many cationic polymers, including high-molecular-weight polyethylenimine (PEI) have been widely studied as gene-delivery carriers, both, in vitro and in vivo. However, interest has recently developed in degradable polymeric systems. The advantage of degradable polymer is its low in-vivo cytotoxicity, which is a result of its easy elimination from the cells and body. Degradable polymer also enhances transfection of DNA or small interfering RNA (siRNA) for efficient gene expression or silencing, respectively. This review paper summarizes and discusses the recent advances with degradable PEIs, such as cross-linked and grafted PEIs for DNA and siRNA delivery.

Biotinylated disulfide containing PEI/avidin bioconjugate shows specific enhanced transfection efficiency in HepG2 cells

Targeting of non-viral gene vectors to liver cells could offer the opportunity to cure liver diseases. In this paper, disulfide-containing polyethylenimine (PEI-SS) was synthesized from low molecular weight branched PEI and cystamine bisacrylamide (CBA), and then grafted with biotin. The obtained biotinylated PEI-SS was bioconjugated with avidin via the biotin-avidin interaction to form a novel gene vector, biotinylated PEI-SS/avidin bioconjugate (ABP-SS). Characteristics of ABP-SS and its pDNA complexes were evaluated in terms of acid-base titration, agarose gel electrophoresis, SEM morphology observation, particle size and zeta-potential measurements, and PEI-SS was used as the control. The acid-base titration results showed that ABP-SS exhibited comparable buffer capability to 25 kDa PEI. The results of gel electrophoresis indicated that ABP-SS was able to condense pDNA efficiently at an N/P ratio of 6 and could be degraded by reducing agent DTT. The ABP-SS/pDNA complexes had a mean particle size of 226 +/- 40 nm and surface charges of 25 mV. The SEM images showed that the complexes had compact structures with spherical or quadrate shapes. In vitro cell viability and transfection of ABP-SS and PEI-SS were compared in HepG2, 293T and H446 cells. Among the three different cell lines, compared with PEI-SS, ABP-SS exhibited much lower cytotoxicity and higher transfection efficacy in HepG2 cells due to the biocompatibility of avidin and the specific interactions between avidin and HepG2 cells. Molecular probes were used to reveal the cellular uptake of complexes, and the results demonstrated that ABP-SS contributes to more cellular uptake of complexes in HepG2 cells, which was consistent with the transfection results.

Mannosylated chitosan-graft-polyethylenimine as a gene carrier for Raw 264.7 cell targeting

Gene transfer using non-viral vectors is a promising approach for the safe delivery of therapeutic genes. Among non-viral vectors, chitosans have been proposed as alternative, biocompatible cationic polymers for non-viral gene delivery. However, the low transfection efficiency and low specificity of chitosan needs to be addressed prior to clinical application. In this study, mannosylated chitosan-graft-polyethylenimine (Man-CHI-g-PEI) copolymer was prepared by thiourea reaction between the isothiocyanate group of mannopyranosylphenylisothiocyanate and the amine groups of chitosan-graft-PEI (CHI-g-PEI) for targeting into antigen presenting cells (APCs) having mannose receptors. The composition and molecular weight were characterized using (1)H NMR and GPC, respectively. The copolymer was complexed with plasmid DNA in various copolymer/DNA (N/P) charge ratios, and the complexes were characterized. Man-CHI-g-PEI showed good DNA binding ability and high protection of DNA from nuclease attack and had low cytotoxicity compared with PEI 25K. The transfection efficiency of Man-CHI-g-PEI/DNA complexes into the Raw 264.7 macrophage cell line, which has mannose receptors, was higher than CHI-g-PEI itself as well as PEI 25K, indicating Man-CHI-g-PEI can be used as an APCs' targeting gene delivery carrier.

Hybrid of baculovirus and galactosylated PEI for efficient gene carrier

Baculovirus, containing an appropriate eukaryotic promoter, is considered an attractive approach for an efficient and safe gene delivery vehicle. However, the drawbacks of baculovirus, such as the lack of specificity and the inactivation of baculovirus by the complement system in human serum, negatively affect efficient gene delivery. Therefore, a hybrid system utilizing the positive aspects of both viral and non-viral vector systems would be useful to overcome the obstacles of either system alone. In this study, we constructed a hybrid system composed of baculovirus (B) and galactosylated polyethylenimine (GP)/DNA complexes through electrostatic interaction. The resulting GP/B hybrid had suitable physicochemical properties and low cytotoxicity for use in gene therapy. Furthermore, the GP/B significantly enhanced transduction efficiency and showed good cell-specificity compared to either viral or non-viral vector systems. These results suggest that the GP/B hybrid system can be used in gene therapy to enhance transduction efficiency and hepatocyte specificity.

SPION-loaded chitosan-linoleic acid nanoparticles to target hepatocytes

The aim of this study was to develop a novel polymeric magnetic nanoprobe as an MRI contrast agent to target hepatocytes, as well as to evaluate the targeting ability of the nanoprobe with MRI in vivo. Superparamagnetic iron oxide nanocrystals (SPIONs) were synthesized by a thermal decomposition and seed growth method. An 1-ethyl-3-(3-(dimethylamino)-propyl) carbodiimide (EDC)-mediated reaction coupled water-soluble chitosan (WSC) to linoleic acid (LA). Twelve-nanometer-sized SPIONs were incorporated into the core of self-assembled WSC-LA nanoparticles. The morphology and size distribution of the SPION-loaded WSC-LA nanoparticles (SCLNs) were determined by transmittance electron microscopy (TEM) and dynamic light scattering (DLS), respectively. The encapsulation of SPIONs in the WSC-LA nanoparticles reduced the cytotoxicity of bare iron particles and enhanced their dispersion ability in water. The clustering of SPIONs into WSC-LA nanoparticles showed ultrasensitive magnetic behavior. After in vivo intravascular SCLN injection, MRI revealed relative signal enhancement in the liver. The localization of SCLN in hepatocytes was confirmed by Prussian blue staining and TEM analysis. We have successfully developed an ultrasensitive SCLN that effectively targets hepatocytes. The SCLN can be used as a contrast agent to aid in the diagnosis of hepatic diseases.

Nucleic acid delivery with chitosan and its derivatives

Chitosan is a naturally occurring cationic mucopolysaccharide. It is generally biocompatible, biodegradable, mucoadhesive, non-immunogenic and non-toxic. Although chitosan is able to condense nucleic acids (NA) (both DNA and RNA) and protect them from nuclease degradation, its poor water solubility and low transfection efficacy have impeded its use as an NA carrier. In order to overcome such limitations, a multitude of strategies for chitosan modification and formulation have been proposed. In this article, we will first give a brief overview of the physical and biological properties of chitosan. Then, with a special focus on plasmid DNA delivery, we will have a detailed discussion of the latest advances in chitosan-mediated NA transfer. For future research, the following three important areas will be discussed: chitosan-mediated therapeutic small RNA transfer, structure-activity relationships (SAR) in chitosan vector design, and chitosan-mediated oral/nasal NA therapy.

Efficient gene delivery using chitosan-polyethylenimine hybrid systems

Chitosan and chitosan derivatives have been investigated as non-viral vectors because they have several advantages, such as biocompatibility, biodegradability, low cytotoxicity and low immunogenicity. However, low transfection efficiency and low cell specificity must be solved for their use in clinical trials. In this paper, chitosan-polyethylenimine (PEI) hybrid systems such as chitosan/PEI blend and chitosan-graft-PEI are described for efficient gene delivery because the PEI has high transfection efficiency owing to a proton sponge effect and chitosan has biocompatibility. Also, hepatocyte specificity of the galactosylated chitosan is explained after combination with PEI.