Improved transfection efficiency of CS/DNA complex by co-transfected chitosanase gene

Peptide-Chitosan Engineered Scaffolds for Biomedical Applications

Peptides are signaling epitopes that control many vital biological events. Increased specificity, synthetic feasibility with concomitant lack of toxicity, and immunogenicity make this emerging class of biomolecules suitable for different applications including therapeutics, diagnostics, and biomedical engineering. Further, chitosan, a naturally occurring linear polymer composed of d-glucosamine and N-acetyl-d-glucosamine units, possesses anti-microbial, muco-adhesive, and hemostatic properties along with excellent biocompatibility. As a result, chitosan finds application in drug/gene delivery, tissue engineering, and bioimaging. Despite these applications, chitosan demonstrates limited cell adhesion and lacks biosignaling. Therefore, peptide-chitosan hybrids have emerged as a new class of biomaterial with improved biosignaling properties and cell adhesion properties. As a result, recent studies encompass increased application of peptide-chitosan hybrids as composites or conjugates in drug delivery, cell therapy, and tissue engineering and as anti-microbial material. This review discusses the recent investigations involving chitosan-peptide materials and uncovers various aspects of these interesting hybrid materials for biomedical applications.

Superior transfection efficiency of phagocytic astrocytes by large chitosan/DNA nanoparticles

PURPOSE

Mechanism study of why astrocytes isolated from experimental autoimmune encephalomyelitis (EAE)-induced B6 mice or after being exposed to inflammatory factors had the highest transfection efficiency to larger-sized, but not compacted, pspCS/pDNA particles.

METHODS

Phosphorylatable short peptide conjugated chitosan (pspCS) was compounded with plasmid DNA (pDNA) at different N:P ratios to form pspCS/pDNA particles of different size and zeta potentials. These pspCS/pDNA particles were used for the transfection of astrocytes isolated from either EAE induced or healthy B6 mice. Transfection efficiency and cell permeability of the particles were determined by the internalization of radio [H3]-labeled plasmid and the expression of a luciferase reporter gene respectively. Phagocytosis of EAE-astrocytes was determined by the internalization of FITC labeled dextran beads. By comparing the transfection efficiency of differently-sized pspCS/pDNA particles to normal and phagocytic astrocytes, with or without cytochalasin D, a phagocytosis inhibitor, in the presence, the contribution of phagocytosis to cell permeability and transfection efficiency was evaluated.

RESULTS

In vivo EAE-induction or in vitro inflammatory factors treatment transferred normal astrocytes to be phagocytic astrocytes which underwent phagocytosis, had the highest cell permeability and transfection efficiency to larger-sized pspCS/pDNA particles formed at lower N:P ratios. When phagocytosis was inhibited by cytochalasin D, both cell permeability and transfection efficiency of phagocytic astrocytes to larger were significantly decreased. Thereafter, particle size, not zeta potential, was verified as the key factor for determining whether the particles could be phagocytosed. In addition phagocytosis was successfully induced in ARPE-19 cells as well, which also improved the transfection efficiency of larger pspCS/pDNA particles.

CONCLUSION

A generally accepted concept is that the internalization of cationic polymer/pDNA particles, chitosan-DNA complex for instance, is mainly through the procedure of endocytosis of the transfected cells. More compacted particles with higher zeta potential were used to be considered had higher cell permeability and transfection efficiency. However, here we reported that phagocytosis is another important procedure for determining internalization and transfection efficiency of cationic polymer/pDNA nanoparticles, especially for advanced transfection efficiency of large pspCS/pDNA particles. Thus, for gene delivery applications, the environmental condition of the target cells should be seriously considered for selecting an appropriate gene transfer strategies.

Effects of phosphorylatable short peptide-conjugated chitosan-mediated IL-1Ra and igf-1 gene transfer on articular cartilage defects in rabbits

Previously, we reported an improvement in the transfection efficiency of the plasmid DNA-chitosan (pDNA/CS) complex by the utilization of phosphorylatable short peptide-conjugated chitosan (^pSP-CS). In this study, we investigated the effects of ^pSP-CS-mediated gene transfection of interleukin-1 receptor antagonist protein (IL-1Ra) combined with insulin-like growth factor-1 (IGF-1) in rabbit chondrocytes and in a rabbit model of cartilage defects. pBudCE4.1-IL-1Ra+igf-1, pBudCE4.1-IL-1Ra and pBudCE4.1-igf-1 were constructed and combined with ^pSP-CS to form pDNA/^pSP-CS complexes. These complexes were transfected into rabbit primary chondrocytes or injected into the joint cavity. Seven weeks after treatment, all rabbits were sacrificed and analyzed. High levels of IL-1Ra and igf-1 expression were detected both in the cell culture supernatant and in the synovial fluid. In vitro, the transgenic complexes caused significant proliferation of chondrocytes, promotion of glycosaminoglycan (GAG) and collagen II synthesis, and inhibition of chondrocyte apoptosis and nitric oxide (NO) synthesis. In vivo, the exogenous genes resulted in increased collagen II synthesis and reduced NO and GAG concentrations in the synovial fluid; histological studies revealed that pDNA/^pSP-CS treatment resulted in varying degrees of hyaline-like cartilage repair and Mankin score decrease. The co-expression of both genes produced greater effects than each single gene alone both in vitro and in vivo. The results suggest that ^pSP-CS is a good candidate for use in gene therapy for the treatment of cartilage defects and that igf-1 and IL-1Ra co-expression produces promising biologic effects on cartilage defects.

Phosphorylatable short peptide conjugated low molecular weight chitosan for efficient siRNA delivery and target gene silencing

Small interfering RNA (siRNA) has been widely investigated as a potential therapeutic approach for diseases with genetic defects. However, its application was greatly hampered by the rapid degradation and poor cellular uptake. Recently, chitosan (CS) and its derivant have been considered as a promising siRNA transporter with the advantages of low toxicity, good biodegradability and biocompatibility. Chitosan of different molecular weight (Mw) and degrees of deacetylation (DD) showed significantly varied target gene silencing efficacy, and it is still not well clarified how these characteristics influence CS mediated siRNA transfection. To compare the aspects of cell permeability and intracellular unpacking of CS/siRNA complex on the effect of CS/siRNA transfection. A radiolabeled siRNA, targeting firefly luciferase gene, was loaded by chitosan of different molecular weight (varying from 2000 to 800,000 Da) and subjected to the transfection against MDA-MB-231/Luc human breast cancer cell line which stably expressed knocked in firefly Luciferase reporter gene. Following transfection intracellular radioactivity was measured to represent cell entrance ability of the CS/siRNA, while, luciferase activity in the cell lysate was also determined to reflect target gene silencing effect. The results revealed that although low molecular weight chitosan (LMWC) condensed siRNA has the highest cell permeability of almost two folds of medium molecular weight chitosan and lipofactamine, its target gene silencing effect is really low of almost eight times less than lipofectamine. This conspicuous contradiction gave us the hypothesis that LMWC generated more condensed CS/siRNA complex to facilitate cell entrance but the tight electrostatic interaction probably limited intracellular siRNA unpacking as well and unfavorably hindered target gene silencing as the final consequence. To approve this hypothesis a phosphorylatable short peptide conjugated LMWC was adopt to promote intracellular siRNA unpacking. Which was demonstrated of perfect target gene knock down ability to the extent of being even superior to lipofactamine 2000. In a conclusion, low molecular weight chitosan has the great potential to be an ideal siRNA vehicle if the issue of siRNA unpacking could be properly resolved.

Optimize nuclear localization and intra-nucleus disassociation of the exogene for facilitating transfection efficacy of the chitosan

Previously, we had reported improving transfection efficiency of the chitosan-plasmid DNA (CS/pDNA)complex via enhancing intracellular unpacking of the exogene by the utilization of phosphorylatable short peptide conjugated chitosan (pSP-CS). In this article, we addressed a novel strategy of nucleus localization signal linked nucleic kinase substrate short peptide (NNS) modification for further optimization of the transfection efficiency. NNS, consisting of "PKKRKVREEAIKFSEEQRFRR", contained a SV40 nucleus localization signal and a potentially phosphorylatable serine residue. The short peptide could be selectively phosphorylated in the nucleus in various mammalian cells. This phosphorylatable NNS (pNNS) was conjugated to chitosan and combined with Cy3 fluorescence labeled plasmid DNA to form a pNNS-CS/pDNA complex. In vitro phosphorylation and DNA releasing assays verified that pNNS could be effectively and selectively phosphorylated by nucleic lysate, hence promoting pDNA unpacking from the complex. Thereafter, C2C12 myoblast cells were transfected. Nuclear localization of the pDNA was represented by the fluorescence in the nucleus and transfection efficiency was determined by the expression of the luciferase reporter gene, which is carried by the plasmid DNA. The results revealed that, compared with lipofactamine2000 and the previously reported pSP-CS, pNNS-CS could transport more pDNA into the nucleus and intensively augment luciferase reporter gene expression. In conclusion, nucleus localization and unpacking from the delivery vector are both critical factors in influencing exogene expression, and pNNS modification is valuable in improving transfection efficacy of the chitosan.

Isolation, characterization and heterologous expression of a novel chitosanase from Janthinobacterium sp. strain 4239

BACKGROUND

Chitosanases (EC 3.2.1.132) hydrolyze the polysaccharide chitosan, which is composed of partially acetylated beta-(1,4)-linked glucosamine residues. In nature, chitosanases are produced by a number of Gram-positive and Gram-negative bacteria, as well as by fungi, probably with the primary role of degrading chitosan from fungal and yeast cell walls for carbon metabolism. Chitosanases may also be utilized in eukaryotic cell manipulation for intracellular delivery of molecules formulated with chitosan as well as for transformation of filamentous fungi by temporal modification of the cell wall structures.However, the chitosanases used so far in transformation and transfection experiments show optimal activity at high temperature, which is incompatible with most transfection and transformation protocols. Thus, there is a need for chitosanases, which display activity at lower temperatures.

RESULTS

This paper describes the isolation of a chitosanase-producing, cold-active bacterium affiliated to the genus Janthinobacterium. The 876 bp chitosanase gene from the Janthinobacterium strain was isolated and characterized. The chitosanase was related to the Glycosyl Hydrolase family 46 chitosanases with Streptomyces chitosanase as the closest related (64% amino acid sequence identity). The chitosanase was expressed recombinantly as a periplasmic enzyme in Escherichia coli in amounts about 500 fold greater than in the native Janthinobacterium strain. Determination of temperature and pH optimum showed that the native and the recombinant chitosanase have maximal activity at pH 5-7 and at 45 degrees C, but with 30-70% of the maximum activity at 10 degrees C and 30 degrees C, respectively.

CONCLUSIONS

A novel chitosanase enzyme and its corresponding gene was isolated from Janthinobacterium and produced recombinantly in E. coli as a periplasmic enzyme. The Janthinobacterium chitosanase displayed reasonable activity at 10 degrees C to 30 degrees C, temperatures that are preferred in transfection and transformation experiments.

Balancing protection and release of DNA: tools to address a bottleneck of non-viral gene delivery

Engineering polymeric gene-delivery vectors to release an intact DNA payload at the optimal time and subcellular compartment remains a formidable challenge. An ideal vector would provide total protection of complexed DNA from degradation prior to releasing it efficiently near or within the nucleus of a target cell. While optimization of polymer properties, such as molecular weight and charge density, has proved largely inadequate in addressing this challenge, applying polymeric carriers that respond to temperature, light, pH and redox environment to trigger a switch from a tight, protective complex to a more relaxed interaction favouring release at the appropriate time and place has shown promise. Currently, a paucity of gene carriers able to satisfy the contrary requirements of adequate DNA protection and efficient release contributes to the slow progression of non-viral gene therapy towards clinical translation. This review highlights the promising carrier designs that may achieve an optimal balance of DNA protection and release. It also discusses the imaging techniques and three-dimensional in vitro models that can help study these two barriers in the non-viral gene transfer process. Ultimately, efficacious non-viral gene therapy will depend on the combination of intelligent material design, innovative imaging techniques and sophisticated in vitro model systems to facilitate the rational design of polymeric gene-delivery vectors.