The use of chitosan as a condensing agent to enhance emulsion-mediated gene transfer

Effect of preparative variables on small interfering RNA loaded Poly(D,L-lactide-co-glycolide)-chitosan submicron particles prepared by emulsification diffusion method

In this study, poly(D,L-lactide-co-glycolide) (PLGA)-chitosan particles were investigated as an effective delivery system for small interfering RNA (siRNA) by emulsification diffusion method. The type, molecular weight and concentration of chitosan, PLGA type as well as centrifugation and freeze-drying process were amongst the investigated variables. PLGA-chitosan particles obtained were positively charged with particle size between approximately 0.4-1 microm depending on type, molecular weight and concentration of chitosan as well as type of PLGA. A better siRNA loading capacity was observed when a higher degree of 'uncapped end groups' were used. The addition of trehalose has also been shown to stabilize these particles from severe aggregation induced by freeze-drying. It was found that physical properties of PLGA-chitosan particles and their siRNA binding capacity were highly influenced by certain preparation parameters. The desired positive charge of submicron size range PLGA-chitosan particles could therefore be obtained by adjusting and optimizing these preparative and formulation parameters.

Surface mediated in situ differentiation of mesenchymal stem cells on gene-functionalized titanium films fabricated by layer-by-layer technique

In this work, multilayered and gene-functionalized titanium films composed of chitosan (Chi) and plasmid DNA (pEGFP-hBMP2, pGB) were employed to investigate the surface mediated in situ differentiation of mesenchymal stem cells (MSCs). The Chi/pGB multilayered structures were fabricated by layer-by-layer (LbL) assembly technique and degraded to release plasmid DNA complexes depending on bilayer numbers over 7 days. Therefore, the differentiation behaviors of MSCs cultured onto Chi/pGB multilayered titanium films surface were investigated. Chi/pGB LbL-modified titanium films show significant higher (p<0.01) transfection efficiency than those of other groups transfected by lipofectamine 2000 regarding the expression of green fluorescent protein (GFP). Reverse transcription-polymerase chain reaction (RT-PCR) assay revealed that MSCs adhered onto Chi/pGB LbL-modified titanium films could still express hBMP2 mRNA over 7 days culture. Compared with control groups, MSCs cultured onto Chi/pGB LbL-modified titanium films display significantly higher (p<0.01 or p<0.05) production levels of alkaline phosphatase (ALP) and osteocalcin over 7 days and 14 days culture, respectively. These results demonstrate that Chi/pGB LbL-modified titanium films are beneficial for sustained in situ inducing osteoprogenitor cells to differentiate into mature osteoblasts over long time. The approach presented here has potential applications in the development of gene-stimulating biomaterials and implant technology.

Selection of optimal sites for TGFB1 gene silencing by chitosan-TPP nanoparticle-mediated delivery of shRNA

Most human tumors produce high levels of TGF-beta1, whose autocrine and paracrine actions promote tumor cell invasiveness and metastasis. Currently, many experimental therapies that target TGFB1 have utilized antisense DNA or RNA interference (RNAi). Despite the great potential of RNAi, the selection of effective target sites and proper delivery systems for short hairpin RNA (shRNA) remains a significant issue. Here, we used chitosan nanoparticle-mediated delivery of a shRNA-expressing vector to inhibit TGFB1 expression in the human rhabdomyosarcoma cell line RD. Knockdown of TGFB1 by shRNA resulted in a decrease in RD cell growth in vitro and tumorigenicity in nude mice. The efficiency of TGFB1 gene silencing varied with the selection of targeting sites. These data suggest that chitosan nanoparticle-mediated delivery of an shRNA produces efficient TGFB1 knockdown in rhabdomyosarcoma cells and may be a method of choice for shRNA delivery for gene therapy.

Synthesis and properties of a novel methoxy poly(ethylene glycol)-modified galactosylated chitosan derivative

Chitosan and its derivatives are attractive non-viral vectors. To produce target-cell specificity and improve the solubility of chitosan, a novel chitosan derivative, modified with galactose and methoxy poly(ethylene glycol) (mPEG) was synthesized, and structure changes of chitosan and its derivatives were characterized. Compared to chitosan, the solution viscosity of the novel chitosan derivative drastically decreased. And, the degree of substitution (DS) of chitosan by galactose and mPEG were calculated as 0.09 and 0.30. The average diameter and zeta potential of mPEGylated galactosylated chitosan (GaC) nanoparticle containing VRMFat plasmid were 178 nm and +2.93 mV, suggesting suitable properties for gene delivery system. The gel electrophoresis confirmed that the plasmid DNA was remained completely by the mPEGylated GaC nanoparticle. And, the cytotoxic effect of mPEGylated GaC nanoparticles on human embryonic kidney (HEK 293) cells was negligible in comparison with that of control chitosans. Therefore, it is expected that the mPEGylated GaC will have the potential as a targeting gene delivery system for a further application.

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.

Accelerated wound healing by smad3 antisense oligonucleotides-impregnated chitosan/alginate polyelectrolyte complex

Smad3 mediates the intracellular signaling of TGF-beta1 superfamily and plays a critical role in the cellular proliferation, differentiation and elaboration of matrix pivotal to cutaneous wound healing. Smad3 antisense oligonucleotides (ASOs) impregnated polyelectrolyte complex (PEC) containing chitosan and sodium alginate was prepared for accelerated wound healing. Physicochemical properties of PEC were characterized by zeta potential, scanning electron microscopy and bioadhesive test. Full-thickness, excisional wounds were made on the dorsum of C57BL6 mice. Then, smad3 ASOs-PEC, PEC alone, smad3 ASOs and gauze dressing were applied to determine concentration of TGF-beta1 and collagen in tissues and observe the wound contraction and histology of tissues. Zeta potentials and bioadhesive strengths of ASOs-PEC were increased as the chitosan ratio in PEC. In smad3 ASOs-PEC, the healing process suggested by wound closure and histological observation was faster than other groups because collagen contents increased and level of TGF-beta1 decreased. These results demonstrate that the smad3 ASOs-PEC composed of chitosan and sodium alginate could be applied for accelerated wound healing.

Oral administration of bacterially expressed VP28dsRNA to protect Penaeus monodon from white spot syndrome virus

We explored the possibility of protecting Penaeus monodon against white spot syndrome virus (WSSV) infection via interference RNA technology by oral administration of bacterially expressed WSSV VP28dsRNA. Shrimp were given dsRNA orally via two methods. In the first method, pellet feed was coated with inactivated bacteria containing overexpressed dsRNA of the WSSV VP28 gene, and in the second method, pellet feed was coated with VP28dsRNA-chitosan complex nanoparticles. The treated shrimp were orally challenged with WSSV by feeding WSSV-infected tissue. The experiment was conducted for 30 days. The dsRNA-treated shrimp challenged with WSSV showed higher survival compared to control shrimp. Sixty-eight percent survival was observed in shrimp fed with feed coated with inactivated bacteria containing dsRNA of the WSSV VP28 gene whereas 37% survival was observed in shrimp fed with VP28dsRNA-chitosan complex nanoparticle-coated feed. The WSSV caused 100% mortality in shrimp fed with pellet feed coated with inactivated bacteria with empty LITMUS38i vector. At the end of the experiment, the tissue samples prepared from randomly selected shrimp that survived were analyzed via reverse transcriptase-polymerase chain reaction and Western blot analysis for WSSV. The samples were negative for WSSV. Based on the present data and the advantages of dsRNA, we believe that oral administration of crude extract of bacterially expressed VP28dsRNA is a potential therapeutic agent against WSSV infection of shrimp.

Synthesis of acyl thiourea derivatives of chitosan and their antimicrobial activities in vitro

Three different acyl thiourea derivatives of chitosan (CS) were synthesized and their structures were characterized by FT-IR spectroscopy and elemental analysis. The antimicrobial behaviors of CS and its derivatives against four species of bacteria (Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus, and Sarcina) and four crop-threatening pathogenic fungi (Alternaria solani, Fusarium oxysporum f. sp. vasinfectum, Colletotrichum gloeosporioides (Penz.) Saec, and Phyllisticta zingiberi) were investigated. The results indicated that the antimicrobial activities of the acyl thiourea derivatives are much better than that of the parent CS. The minimum value of MIC and MBC of the derivatives against E. coli was 15.62 and 62.49 microg/mL, respectively. All of the acyl thiourea derivatives had a significant inhibitory effect on the fungi in concentrations of 50-500 microg/mL; the maximum inhibitory index was 66.67%. The antifungal activities of the chloracetyl thiourea derivatives of CS are noticeably higher than the acetyl and benzoyl thiourea derivatives. The degree of grafting of the acyl thiourea group in the derivatives was related to antifungal activity; higher substitution resulted in stronger antifungal activity.

Cationic lipids and polymers mediated vectors for delivery of siRNA

RNA interference (RNAi) is one of the most importantly protective phenomena forming from the process combating against virus. Since its high efficiency for silencing the expression of proteins at the posttranscriptional level, RNAi shows great prospect in therapeutics for diseases. However, the delivery of siRNA into cells, tissues or organs remains to be a big obstacle for its applications. Many vectors for siRNA delivery have been developed including viral vectors and non-viral vectors, among them non-viral vectors have the advantages of low toxicity, ease of synthesis and low immune response over viral ones. Cationic liposomes and polymer particles, major varieties of non-viral vectors, used for gene delivery, have shown to be suitable for the delivery of siRNA. Based on the concise introduction of RNAi, this article reviews the non-viral delivery systems of siRNA, hoping to provide helpful information for the development of delivery systems of siRNA, and to summarize literatures about siRNA delivery published in recent years.

Enhance immune response to DNA vaccine based on a novel multicomponent supramolecular assembly

DNA vaccination has tremendous potential for treating or preventing numerous diseases for which traditional vaccines are ineffective but the technique can be limited by low immunogenicity. Current synthetic DNA delivery systems are versatile and safe, but substantially less efficient than viruses. Here, a novel multicomponent supramolecular system involving the preparation of mannose-bearing chitosan oligomers microspheres with entrapping complexes of DNA vaccine and polyethylenimine was developed to mimic many of the beneficial properties of the viruses. After delivery by intramuscular immunization in BALB/c mice, the microspheres induced an enhanced serum antibody responses two orders of magnitude greater than naked DNA vaccine. Additionally, in contrast to naked DNA, the microspheres induced potent cytotoxic T lymphocyte responses at a low dose. Consequently, formulation of DNA vaccines into multicomponent vectors is a powerful means of increasing vaccine potency.

Chitosan nanoparticle as gene therapy vector via gastrointestinal mucosa administration: Results of an in vitro and in vivo study

This study was designed to investigate the in vitro and in vivo transfection efficiency of chitosan nanoparticles used as vectors for gene therapy. Three types of chitosan nanoparticles [quaternized chitosan -60% trimethylated chitosan oligomer (TMCO-60%), C(43-45 KDa, 87%), and C(230 KDa, 90%)] were used to encapsulate plasmid DNA (pDNA) encoding green fluorescent protein (GFP) using the complex coacervation technique. The morphology, optimal chitosan-pDNA binding ratio and conditions for maximal in vitro transfection were studied. The in vivo transfection was conducted by feeding the chitosan/pDNA nanoparticles to 12 BALB/C-nu/nu nude mice. Both conventional and TMCO-60% could form stable nanoparticles with pDNA. The in vitro study showed the transfection efficiency to be in the following descending order: TMCO-60%>C(43-45 KDa, 87%)>C(230 KDa, 90%). TMCO-60% proved to be the most efficient and the optimal chitosan/pDNA ratio being 3.2:1. In vivo study showed most prominent GPF expression in the gastric and upper intestinal mucosa. GFP expression in the mucosa of the stomach and duodenum, jejunum, ileum, and large intestine were found, respectively, in 100%, 88.9%, 77.8% and 66.7% of the nude mice examined. TMCO-60%/pDNA nanoparticles had better in vitro and in vivo transfection activity than the other two, and with minimal toxicity, which made it a desirable non-viral vector for gene therapy via oral administration.

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

Poor water solubility and low transfection efficiency of chitosan are major drawbacks for its use as a gene delivery carrier. PEGylation can increase its solubility, and folate conjugation may improve gene transfection efficiency due to promoted uptake of folate receptor-bearing tumor cells. The aim of this study was to synthesize and characterize folate-poly(ethylene glycol)-grafted chitosan (FA-PEG-Chi) for targeted plasmid DNA delivery to tumor cells. Gel electrophoresis study showed strong DNA binding ability of modified chitosan. The pH(50) values, defined as the pH when the transmittance of a polymer solution at 600 nm has reached 50% of the original value, suggested that the water solubility of PEGylated chitosan had improved significantly. Regression analysis of pH(50) value as a function of substitution degree of PEG yielded an almost linear correlation for PEG-Chi and FA-PEG-Chi. The solubility of PEGylated chitosan decreased slightly by further conjugation of folic acid due to the relatively more hydrophobic nature of folic acid when compared to PEG. In addition, the chitosan-based DNA complexes did not induce remarkable cytotoxicity against HEK 293 cells. FA-PEG-Chi can be a promising gene carrier due to its solubility in physiological pH, efficiency in condensing DNA, low cytotoxicity and targeting ability.

Gene therapy for viral hepatitis

Hepatitis B and C infections are two of the most prevalent viral diseases in the world. Existing therapies against chronic viral hepatitis are far from satisfactory due to low response rates, undesirable side effects and selection of resistant viral strains. Therefore, new therapeutic approaches are urgently needed. This review, after briefly summarising the in vitro and in vivo systems for the study of both diseases and the genetic vehicles commonly used for liver gene transfer, examines the existing status of gene therapy-based antiviral strategies that have been employed to prevent, eliminate or reduce viral infection. In particular, the authors focus on the results obtained in clinical trials and experimental clinically relevant animal models.

Development and characterisation of chitosan nanoparticles for siRNA delivery

Gene silencing mediated by double-stranded small interfering RNA (siRNA) has been widely investigated as a potential therapeutic approach for diseases with genetic defects. The use of siRNA, however, is hampered by its rapid degradation and poor cellular uptake into cells in vitro or in vivo. Therefore, we have explored chitosan as a siRNA vector due to its advantages such as low toxicity, biodegradability and biocompatibility. Chitosan nanoparticles were prepared by two methods of ionic cross-linking, simple complexation and ionic gelation using sodium tripolyphosphate (TPP). Both methods produced nanosize particles, less than 500 nm depending on type, molecular weight as well as concentration of chitosan. In the case of ionic gelation, two further factors, namely chitosan to TPP weight ratio and pH, affected the particle size. In vitro studies in two types of cells lines, CHO K1 and HEK 293, have revealed that preparation method of siRNA association to the chitosan plays an important role on the silencing effect. Chitosan-TPP nanoparticles with entrapped siRNA are shown to be better vectors as siRNA delivery vehicles compared to chitosan-siRNA complexes possibly due to their high binding capacity and loading efficiency. Therefore, chitosan-TPP nanoparticles show much potential as viable vector candidates for safer and cost-effective siRNA delivery.