N,N,N-Trimethylchitosan Chloride as a Gene Vector: Synthesis and Application

Trimethyl chitosan-cysteine-based nanoparticles as an effective delivery system for portulacerebroside A in the management of hepatocellular carcinoma cells in vitro and in vivo

Portulacerebroside A (PCA), a cerebroside compound extracted from Portulaca oleracea L., has been shown to suppress hepatocellular carcinoma (HCC) cells. This study aims to investigate the effectiveness of trimethyl chitosan-cysteine (TMC-Cys) nanocarrier in delivering PCA for HCC management and to elucidate the molecular mechanisms behind PCA's function. TMC-Cys nanocarriers notably augmented PCA's function, diminishing the proliferation, migration, and invasiveness of HCC cells in vitro, reducing hepatocellular tumorigenesis in immunocompetent mice, and impeding metastasis of xenograft tumours in nude mice. Comprehensive bioinformatics analyses, incorporating Super-PRED systems alongside pathway enrichment analysis, pinpointed toll-like receptor 4 (TLR4) and epidermal growth factor receptor (EGFR) as two promising targets of PCA, enriched in immune checkpoint pathway. PCA/nanocarrier (PCA) reduced levels of TLR4 and EGFR and their downstream proteins, including programmed cell death ligand 1, thereby increasing populations and activity of T cells co-cultured with HCC cells in vitro or in primary HCC tumours in mice. However, these effects were counteracted by additional artificial activation of TLR4 and EGFR. In conclusion, this study provides novel evidence of PCA's function in immunomodulation in addition to its direct tumour suppressive effect. TMC-Cys nanocarriers significantly enhance PCA efficacy, indicating promising application as a drug delivery system.

Type I collagen scaffold with WNT5A plasmid for in situ cartilage tissue engineering

BACKGROUND

Cartilage tissue lacks the ability to heal. Cartilage tissue engineering using cell-free scaffolds has been increasingly used in recent years.

OBJECTIVE

This study describes the use of a type I collagen scaffold combined with WNT5A plasmid to promote chondrocyte proliferation and differentiation in a rabbit osteochondral defect model.

METHODS

Type I collagen was extracted and fabricated into a collagen scaffold. To improve gene transfection efficiency, a cationic chitosan derivative N,N,N-trimethyl chitosan chloride (TMC) vector was used. A solution of TMC/WNT5A complexes was adsorbed to the collagen scaffold to prepare a WNT5A scaffold. Osteochondral defects were created in the femoral condyles of rabbits. The rabbits were divided into defect, scaffold, and scaffold with WNT5A groups. At 6 and 12 weeks after creation of the osteochondral defects, samples were collected from all groups for macroscopic observation and gene expression analysis.

RESULTS

Samples from the defect group exhibited incomplete cartilage repair, while those from the scaffold and scaffold with WNT5A groups exhibited "preliminary cartilage" covering the defect. Cartilage regeneration was superior in the scaffold with WNT5A group compared to the scaffold group. Safranin O staining revealed more proteoglycans in the scaffold and scaffold with WNT5A groups compared to the defect group. The expression levels of aggrecan, collagen type II, and SOX9 genes were significantly higher in the scaffold with WNT5A group compared to the other two groups.

CONCLUSIONS

Type I collagen scaffold showed effective adsorption and guided the three-dimensional arrangement of stem cells. WNT5A plasmid promoted cartilage repair by stimulating the expression of aggrecan, type II collagen, and SOX9 genes and proteins, as well as inhibiting cartilage hypertrophy.

Does polysaccharide quaternization improve biological activity?

The natural polysaccharides, due to their structural diversity, commonly present very distinct solubility and physical chemical properties and additionally have intrinsic biological activities that, gene-rally, reveal themselves in a light way. The chemical modification of the molecular structure can improve these parameters. In this review, original articles that approached the quaternization of polysaccharides for purposes of biological application were selected, without limitation of year of publication, in the databases Scopus, Web of Science and PubMed. The results obtained from the bibliographic survey indicate that the increase in positive charges caused by quaternization improves the interaction between modified polysaccharides and structures that have negative charges on their surface, such as the cell wall of microorganisms and some cells in the human body, such as the DNA. This greater interaction is reflected as an increase in the biological activity of all polysaccharides broached in this study. Another important data obtained was the fact that the chemical changes did not affect or irrelevantly affect the toxicity of almost all of the polysaccharides that were quaternized. Therefore, polysaccharide quaternization is a safe and effective way to obtain improvements in the biological behavior of these macromolecules.

Gene-activated dermal equivalents to accelerate healing of diabetic chronic wounds by regulating inflammation and promoting angiogenesis

Diabetic chronic wound, characterized by prolonged inflammation and impaired angiogenesis, has become one of the most serious challenges in clinic and pose a significant healthcare burden worldwide. Although a great variety of wound dressings have been developed, few of encouraged achievements were obtained so far. In this study, the gene-activated strategy was applied to enhance sustained expression of vascular endothelial growth factor (VEGF) and achieve better healing outcomes by regulating inflammation and promoting angiogenesis. The gene-activated bilayer dermal equivalents (Ga-BDEs), which has good biocompatibility, were fabricated by loading the nano-sized complexes of Lipofectamine 2000/plasmid DNA-encoding VEGF into a collagen-chitosan scaffold/silicone membrane bilayer dermal equivalent. The DNA complexes were released in a sustained manner and showed the effective transfection capacities to up-regulate the expression of VEGF in vitro. To overcome cutaneous contraction of rodents and mimic the wound healing mechanisms of the human, a reformative rat model of full-thickness diabetic chronic wound was adopted. Under the treatment of Ga-BDEs, speeding wound healing was observed, which is accompanied by the accelerated infiltration and phenotype shift of macrophages and enhanced angiogenesis in early and late healing phases, respectively. These proved that Ga-BDEs possess the functions of immunomodulation and pro-angiogenesis simultaneously. Subsequently, the better regeneration outcomes, including deposition of oriented collagen and fast reepithelialization, were achieved. All these results indicated that, being different from traditional pro-angiogenic concept, the up-regulated expression of VEGF by Ga-BDEs in a sustained manner shows versatile potentials for promoting the healing of diabetic chronic wounds.

Effect of the linear aliphatic amine functionalization on in vitro transfection efficiency of chitosan nanoparticles

The aim of this study is to prepare the long linear aliphatic amine pendant group-functionalized chitosan based nanoparticulate gene carrier system with improved properties for the efficient transfection. The amine functionalized chitosan (MChi) was synthesized by using N-(2-hydroxyethyl)ethylenediamine (HE-EDA) and characterized for the first time. The nanoparticles of MChi (nMChi) were prepared by ionic gelation method, and their particle size, polydispersity (PDI), zeta potential (mV), gene binding capacity and cytotoxicity were determined. Green Fluorescent Protein circular plasmid DNA (pEGFN1) loaded nanoparticles (gnMChi) were used in the transfection studies. The results showed that nMChi with a particle size of 102.9 nm and zeta potential of 41.9 ± 5.63 mV was non-toxic, had high transfection efficiency in Human Embryonic Kidney 293 and Primary Ovine Fibroblast cell lines and would be used as an efficient gene carrier system.

Novel application of trimethyl chitosan as an adjuvant in vaccine delivery

The application of natural carbohydrate polysaccharides for antigen delivery and its adjuvanation potential has garnered interest in the scientific community in the recent years. These biomaterials are considered favorable candidates for adjuvant development due to their desirable properties like enormous bioavailability, non-toxicity, biodegradability, stability, affordability, and immunostimulating ability. Chitosan is the one such extensively studied natural polymer which has been appreciated for its excellent applications in pharmaceuticals. Trimethyl chitosan (TMC), a derivative of chitosan, possesses these properties. In addition it has the properties of high aqueous solubility, high charge density, mucoadhesive, permeation enhancing (ability to cross tight junction), and stability over a range of ionic conditions which makes the spectrum of its applicability much broader. It has also been seen to perform analogously to alum, complete Freund’s adjuvant, incomplete Freund’s adjuvant, and cyclic guanosine monophosphate adjuvanation, which justifies its role as a potent adjuvant. Although many review articles detailing the applications of chitosan in vaccine delivery are available, a comprehensive review of the applications of TMC as an adjuvant is not available to date. This article provides a comprehensive overview of structural and chemical properties of TMC which affect its adjuvant characteristics; the efficacy of various delivery routes for TMC antigen combination; and the recent advances in the elucidation of its mechanism of action.

Functionalized Scaffold for in Situ Efficient Gene Transfection of Mesenchymal Stem Cells Spheroids toward Chondrogenesis

Multicellular mesenchymal stem cell (MSC) spheroids possess enhanced chondrogenesis ability and limited fibrosis, exhibiting advantage toward hyaline-like cartilage regeneration. However, because of the limited cell surfaces in spheroid exposed to DNA/vector, it is difficult to realize efficient gene transfection, most of which highly rely on cell-substrate interaction. Here, we report a poly(l-glutamic acid)-based porous scaffold with tunable inner surfaces that can sequentially realize cell-scaffold attachment and detachment, as well as the followed in situ spheroid formation. The attachment and detachment of cells from scaffold is achieved by the capture and release of fibronectin (Fn) via reversible imine linkage between aromatic aldehyde groups of scaffold and amino groups of Fn. Together with N, N, N-trimethyl chitosan chloride condensing plasmid DNA encoding transforming growth factor-β1 (pDNA-TGF-β1), cell attachment realizes efficient surface-mediated gene transfection. Conversion of scaffold stiffness can affect the adhesion shape of cells. Stiffer scaffold reinforces the adhesion, leading to the amplification of peripheral focal adhesions and the promotion of cell spreading, as well as the promotion of gene transfection efficiency. After cellular detachment from the scaffold via lysine treatment, the subsequent spheroid formation with extensive cell-cell interaction up-regulates the corresponding protein expression with a prolonged term. With the induction effect of the expressed TGF-β1, significantly enhanced chondrogenesis of MSCs in spheroids is achieved at 10 d in vitro. Well-regenerated cartilage at 8 weeks in vivo indicates that the present gene transfection system is a platform that can be potentially applied toward cartilage tissue engineering.

Effects of tripolyphosphate on cellular uptake and RNA interference efficiency of chitosan-based nanoparticles in Raw 264.7 macrophages

Tumor necrosis factor-α (TNF-α) is a major pro-inflammatory cytokine that is mainly secreted by macrophages during inflammation. Here, we synthesized a series of N-(2-hydroxy)propyl-3-trimethyl ammonium chitosan chlorides (HTCCs), and then used a complex coacervation technique or tripolyphosphate (TPP)-assisted ionotropic gelation strategy to complex the HTCCs with TNF-α siRNA (siTNF) to form nanoparticles (NPs). The resultant NPs had a desirable particle size (210-279nm), a slightly positive zeta potential (14-22mV), and negligible cytotoxicity against Raw 264.7 macrophages and colon-26 cells. Subsequent cellular uptake tests demonstrated that the introduction of TPP to the NPs markedly increased their cellular uptake efficiency (to nearly 100%) compared with TPP-free NPs, and yielded a correspondingly higher intracellular concentration of siRNA. Critically, in vitro gene silencing experiments revealed that all of the TPP-containing NPs showed excellent efficiency in inhibiting the mRNA expression level of TNF-α (by approximately 85-92%, which was much higher than that obtained using Oligofectamine/siTNF complexes). Collectively, these results obviously suggest that our non-toxic TPP-containing chitosan-based NPs can be exploited as efficient siTNF carriers for the treatment of inflammatory diseases.

Trigger-responsive, fast-degradable poly(β-amino ester)s for enhanced DNA unpackaging and reduced toxicity

Poly(β-amino ester)s (PBAEs) represent an important class of cationic gene delivery materials which, however, suffer from uncontrolled DNA release due in part to the slow degradation of their polyester backbone. Additionally, PBAEs with high molecular weight (MW) also show considerable toxicities. In this study, we designed and developed PBAEs with trigger-responsive domains built-in polymer backbones that can be rapidly cleaved upon external UV light triggering to promote intracellular DNA release as well as reduce material toxicity. Photo-responsive PBAEs were prepared via polyaddition of (2-nitro-1,3-phenylene)bis(methylene) diacrylate and a bifunctional amine. The nitrobenzene moiety was placed in each repeating unit of the PBAE to allow fast response to external UV irradiation, and thus the ester linkers were cleaved and the polymers were degraded within several minutes upon UV irradiation. Cationic PBAEs with high MWs were able to mediate effective intracellular gene delivery, while upon UV irradiation post-transfection, enhanced DNA unpackaging and reduced material toxicity were observed, which collectively contributed to greatly improved transfection efficiencies in various mammalian cell types tested. This strategy allows precise manipulation of material toxicity and gene release profiles of PBAEs, and thus provides an effective design approach to address critical issues in non-viral gene delivery.

Effect of N/P ratios on physicochemical stability, cellular association, and gene silencing efficiency for trimethyl chitosan/small interfering RNA complexes

N,N,N-Trimethyl chitosan (TMC) with 40% quaternization was used as a vector for small interfering RNA (siRNA) delivery. Nano-sized complexes were formed in water by mixing siRNA with TMC; the smallest particle sizes were obtained at a N/P ratio of 10. The complexes had a positive surface charge that increased with increases in the N/P ratio and leveled off at +20 mV with N/P ratios > 10. The majority of particles had a diameter <100 nm under transmission electron microscope (TEM). When the N/P ratio was >10, the binding efficiency of TMC with siRNA was >90%. In 25% fetal bovine serum, the TMC/siRNA complexes with N/P ratios of 10 and 20 were intact for 12 and 48 h, respectively. TMC/siRNA complexes with an N/P ratio > 5 efficiently entered the human embryonic kidney (HEK) 293 cells and trapped initially in the lysosomes, which could then relocate in the cytoplasm. Gene silencing, tested by using enhanced green fluorescent protein (EGFP), was reduced to ~60% by the complexes with N/P ratios of 10 and 20. Specific silencing was confirmed by dose dependency and nonsilencing effect of sequence-mismatch siRNA. No significant cytotoxicity was detected for the TMC/siRNA complexes. In this study, the influence of the N/P ratio on TMC/siRNA complexes was systematically investigated and TMC was found to be an effective vector for siRNA delivery using optimized formulations.

Nuclear location signal peptide–modified poly (ethyleneimine)/DNA complexes: An efficient gene delivery vector in vitro and in vivo

The low transfection efficiency of nonviral gene delivery systems limits their applications. In this study, we demonstrated a simple method to modify poly(ethyleneimine)/DNA complexes with a nuclear location signal peptide via bis(succinimidyl) penta(ethylene glycol) coupling. The amount of grafted nuclear location signal peptide was controlled within a range of 0–9 µg for poly(ethyleneimine)/DNA complexes containing 10 µg DNA and 100 µg poly(ethyleneimine) by adjusting the grafting agent and peptide feeds. The particle size and surface zeta-potential of the complexes were largely retained after nuclear location signal immobilization. Based on the results of the flow cytometry measurements, the nuclear location signal–modified poly(ethyleneimine)/DNA complexes were internalized into at bone marrow stem cells at a significantly faster rate and a higher amount than the unmodified complexes. In vitro transfection experiments, using plasmid DNA encoding bone morphogenetic protein 2, indicated that the nuclear location signal peptide–modified poly(ethyleneimine)/DNA complexes have significantly higher gene transfection ability toward bone marrow stem cells than unmodified complexes. The porous collagen scaffolds loaded with nuclear location signal–modified poly(ethyleneimine)/plasmid DNA encoding bone morphogenetic protein 2 complexes successfully transfected tissue cells and induced the human bone morphogenetic protein 2 expression in a rat. The modification of the poly(ethyleneimine)/DNA complexes with nuclear location signal peptide was effective in enhancing gene transfection of complexes in vitro and in vivo, thus indicating potential applications for bioactive scaffolds with enhanced tissue regeneration performance.

RNAi functionalized scaffold for scarless skin regeneration

Combination of a 3-D scaffold with the emerging RNA interference (RNAi) technique represents the latest paradigm of regenerative medicine. In our recent paper "RNAi functionalized collagen-chitosan/silicone membrane bilayer dermal equivalent for full-thickness skin regeneration with inhibited scarring" in the journal Biomaterial, we not only demonstrated a 3-D system for siRNA sustained delivery, but also presented a comprehensive in vivo study by targeting a vital problem in skin regeneration: scarring. It is expected that further development of this kind of RNAi functionalized scaffold can provide a better platform for directing cell fates by integrating the "down-regulating" biomolecular cues into the cellular microenvironment, leading to the complete functional regeneration of skin.

Fabrication of poly(lactide-co-glycolide) scaffold filled with fibrin gel, mesenchymal stem cells, and poly(ethylene oxide)-b-poly(L-lysine)/TGF-β1 plasmid DNA complexes for cartilage restoration in vivo

A poly (lactide-co-glycolide) (PLGA) scaffold filled with fibrin gel, mesenchymal stem cells (MSCs) and poly(ethylene oxide)-b-poly (L-lysine) (PEO-b-PLL)/pDNA-TGF-β1 complexes was fabricated and applied in vivo for synchronized regeneration of cartilage and subchondral bone. The PEO-b-PLL/pDNA-TGF-β1 complexes could transfect MSCs in vitro to produce TGF-β1 in situ and up regulate the expression of chondrogenesis-related genes in the construct. The expression of heterogeneous TGF-β1 in vivo declined along with the prolongation of implantation time, and lasted for 3 and 6 weeks in the mRNA and protein levels, respectively. The constructs (Experimental group) of PLGA/fibrin gel/MSCs/(PEO-b-PLL/pDNA-TGF-β1 complexes) were implanted into the osteochondral defects of rabbits to restore the functional cartilages, with gene-absent constructs as the Control. After 12 weeks, the Experimental group regenerated the neo-cartilage and subchondral bone with abundant deposition of glycosaminoglycans (GAGs) and type II collagen. The regenerated tissues had good integration with the host tissues too. By contrast, the defects were only partially repaired by the Control constructs. qRT-PCR results demonstrated that expression of the chondrogenesis-marker genes in the Experimental group was significantly higher than that of the Control group, and was very close to that of the normal cartilage tissue.

RNAi functionalized collagen-chitosan/silicone membrane bilayer dermal equivalent for full-thickness skin regeneration with inhibited scarring

Scar inhibition of dermal equivalent is one of the key issues for treatment of full thickness skin defects. To yield a bioactive RNAi functionalized matrix for skin regeneration with inhibited scarring, collagen-chitosan/silicone membrane bilayer dermal equivalent (BDE) was combined with trimetylchitosan (TMC)/siRNA complexes which could induce suppression of transforming growth factor-β1 (TGF-β1) pathway. The RNAi-BDE functioned as a reservoir for the incorporated TMC/siRNA complexes, enabling a prolonged siRNA release. The seeded fibroblasts in the RNAi-BDE showed good viability, internalized the TMC/siRNA complexes effectively and suppressed TGF-β1 expression constantly until 14 d. Application of the RNAi-BDE on the full-thickness skin defects of pig backs confirmed the in vivo inhibition of TGF-β1 expression by immunohistochemistry, real-time quantitative PCR and western blotting during 30 d post surgery. The levels of other scar-related factors such as collagen type I, collagen type III and α-smooth muscle actin (α-SMA) were also down-regulated. In combination with the ultra-thin skin graft transplantation for 73 d, the regenerated skin by RNAi-BDE had an extremely similar structure to that of the normal one. Our study reflects the latest paradigm of tissue engineering by incorporating the emerging biomolecule siRNA. The 3-D scaffolding materials for siRNA delivery may have general implications in generation of bioactive matrix as well.

Injectable nanohybrid scaffold for biopharmaceuticals delivery and soft tissue engineering

An injectable nanofibrous hydrogel scaffold integrated with growth factors (GFs) loaded polysaccharide nanoparticles was developed that specifically allows for targeted adipose-derived stem cells (ASCs) encapsulation and soft tissue engineering. The nanofibrous hydrogel was produced via biological conjugation of biotin-terminated star-shaped poly(ethylene glycol) (PEG-Biotin) and streptavidin-functionalized hyaluronic acid (HA-Streptavidin). The polysaccharide nanoparticles were noncovalently assembled via electrostatic interactions between low-molecular-weight heparin (LMWH) and N,N,N-trimethylchitosan chloride (TMC). Vascular endothelial growth factor (VEGF) was entrapped in the LMWH/TMC nanoparticles by affinity interactions with LMWH.

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.

Quaternary Salts of Chitosan: History, Antimicrobial Features, and Prospects

Recently, increasing attention has been paid to water-soluble derivatives of chitosan at its applications. The chemical characteristics and the antimicrobial properties of these salts can play significant role in pharmacological and food areas mainly as carriers for drug delivery systems and as antimicrobial packaging materials. In the current paper, a historical sequence of the main preparative methods, physical chemistry aspects, and antimicrobial activity of chitosan quaternized derivatives are presented and briefly discussed. In general, the results indicated that the quaternary derivatives had better inhibitory effects than the unmodified chitosan.

Chemo-physical and biological evaluation of poly(L-lysine)-grafted chitosan copolymers used for highly efficient gene delivery

For the success of non-viral gene delivery, it is of great importance to develop gene vectors with high efficiency but low toxicity. We demonstrate that PLL-grafted chitosan copolymers combine the advantages of PLL with its good pDNA-binding ability and of chitosan with its good biocompatibility. The chemo-physical properties of the prepared Chi-g-PLL copolymers are thoroughly characterized. The in vitro transfection study shows that the copolymers have a much higher gene transfer ability than the starting materials chitosan and PLL. A positive correlation between PLL chain lengths and transfection efficiency of the copolymers is found. Our results suggest that these novel Chi-g-PLL copolymers are good candidates for gene delivery in vivo.

The healing of full-thickness burns treated by using plasmid DNA encoding VEGF-165 activated collagen-chitosan dermal equivalents

Repair of deep burn by use of the dermal equivalent relies strongly on the angiogenesis and thereby the regeneration of dermis. To enhance the dermal regeneration, in this study plasmid DNA encoding vascular endothelial growth factor-165 (VEGF-165)/N,N,N-trimethyl chitosan chloride (TMC) complexes were loaded into a bilayer porous collagen-chitosan/silicone membrane dermal equivalents (BDEs), which were applied for treatment of full-thickness burn wounds. The DNA released from the collagen-chitosan scaffold could remain its supercoiled structure but its degree was decayed along with the prolongation of incubation time. The released DNA could transfect HEK293 cells in vitro with decayed efficiency too. Human umbilical vein endothelial cells (HUVECs) in vitro cultured in the scaffold loaded with TMC/pDNA-VEGF complexes expressed a significantly higher level of VEGF and showed higher viability than those cultured in the controls, i.e. blank scaffold, and scaffolds loaded with naked pDNA-VEGF and TMC/pDNA-eGFP, respectively. The four different BDEs were then transplanted in porcine full-thickness burn wounds. Results showed that the TMC/pDNA-VEGF group had a significantly higher number of newly-formed and mature blood vessels, and fastest regeneration of the dermis. RT-qPCR and western blotting found that the experimental group also had the highest expression of VEGF, CD31 and α-SMA in both mRNA and protein levels. Furthermore, ultra-thin skin grafting was performed on the regenerated dermis 14 days later, leading to complete repair of the burn wounds with normal histology. Moreover, the tensile strength of the repaired tissue increased along with the time prolongation of post grafting, resulting in a value of approximately 70% of the normal skin at 105 days.

Preparation and characterization of folate conjugated N-trimethyl chitosan nanoparticles as protein carrier targeting folate receptor: in vitro studies

Folate conjugated N-trimethyl chitosan (folate-TMC) was synthesized and characterized using Fourier transform infrared (FTIR) and (1)H spectroscopy. The fluorescein isothiocyanate conjugated bovine serum albumin (FITC-BSA) loaded TMC-nanoparticle (FB-TMC-NP) and FITC-BSA loaded folate-TMC-nanoparticle (FB-f-TMC-NP) were prepared by ionic cross-linking of TMC or folate-TMC with sodium alginate. Single factor analysis method was used to optimize the formulation of nanoparticles. The encapsulating efficiencies of FB-TMC-NP and FB-f-TMC-NP produced by optimal formulation were 98.3 +/- 1.9% and 98.7 +/- 2.7% (n=3), respectively. In addition, the mean diameters of FB-TMC-NP and FB-f-TMC-NP were 184.3 +/- 8.3 nm and 176.1 +/- 5.0 nm (n = 3), respectively. Transmission electron microscope (TEM) showed that the nanoparticles were of spherical shapes. The intracellular uptake of FB-f-TMC-NP by SKOV3 cells (folate receptor overexpressing cells) was 3.7-fold more than that of FB-TMC-NP and could be inhibited by the presence of 1 mM folate in the culture medium, although there was no significant difference between the intracellular uptake of FB-f-TMC-NP in A549 cells (folate receptor-deficient cells) and that of FB-TMC-NP in the same cells. In conclusion, the enhancement of cellular uptake of FB-f-TMC-NP by SKOV3 cells in a specific way was attributed to the folate receptor-mediated endocytosis. FB-TMC-NP was a promising carrier for protein.

Enhanced angiogenesis of gene-activated dermal equivalent for treatment of full thickness incisional wounds in a porcine model

Angiogenesis of dermal equivalent is one of the key issues for treatment of full thickness skin defects. To develop a gene-activated bilayer dermal equivalent (BDE), N,N,N-trimethyl chitosan chloride (TMC), a cationic gene delivery vector, was used to form complexes with the plasmid DNA encoding vascular endothelial growth factor-165 (VEGF-165), which was then incorporated into a collagen-chitosan/silicone membrane scaffold. To evaluate the angiogenesis property in vivo, full thickness skin defects were made on the back of pigs, into which the TMC/pDNA-VEGF complexes loaded BDE and other three control BDEs, i.e. the blank BDE, and the BDEs loaded with pDNA-VEGF and TMC/pDNA-eGFP complexes, respectively, were transplanted. Biopsy specimens were harvested at day 7, 10 and 14 after surgery for histology, immunohistochemistry, immunofluorescence, real-time quantitative PCR (RT-qPCR) and western blotting analyses. The results showed that the TMC/pDNA-VEGF group had the strongest VEGF expression in mRNA and protein levels, resulting in the highest densities of newly-formed and mature vessels. The ultra-thin skin graft was further transplanted onto the dermis regenerated by the TMC/pDNA-VEGF complexes loaded BDE at day 10 and well survived. At 112 days grafting, the healing skin had a similar structure and approximately 80% tensile strength of the normal skin.

In vivo restoration of full-thickness cartilage defects by poly(lactide-co-glycolide) sponges filled with fibrin gel, bone marrow mesenchymal stem cells and DNA complexes

A composite construct comprising of bone marrow mesenchymal stem cells (BMSCs), plasmid DNA encoding transforming growth factor-beta1 (pDNA-TGF-beta1), fibrin gel and poly (lactide-co-glycolide) (PLGA) sponge was designed and employed to repair articular cartilage defects. To improve the gene transfection efficiency, a cationized chitosan derivative N,N,N-trimethyl chitosan chloride (TMC) was employed as the vector. The TMC/DNA complexes had a transfection efficiency of 9% to BMSCs and showed heterogeneous TGF-beta1 expression in a 10-day culture period in vitro. In vivo culture of the composite constructs was performed by implantation into full-thickness cartilage defects of New Zealand white rabbit joints, using the constructs absence of pDNA-TGF-beta1 or BMSCs as controls. Heterogeneous expression of TGF-beta1 in vivo was detected at 4 weeks, but its level was decreased in comparison with that of 2 weeks. After implantation for 12 weeks, the cartilage defects were successfully repaired by the composite constructs of the experimental group, and the neo-cartilage integrated well with its surrounding tissue and subchondral bone. Immunohistochemical and glycosaminoglycans (GAGs) staining confirmed the similar amount and distribution of collagen type II and GAGs in the regenerated cartilage as that of hyaline cartilage. The cartilage special genes expressed in the neo-tissue were closer to those of the normal cartilage. An overall score of 2.83 was obtained according to Wakitani's standard. By contrast, only part of the defects was repaired by the pDNA-TGF-beta1 absence constructs, and no cartilage repair but fibrous tissue was found for the BMSCs absence constructs. Therefore, combination of the PLGA sponge/fibrin gel scaffold with BMSCs and gene therapy is an effective method to restore cartilage defects and may have a great potential for practical applications in the near future.

Development of pH-responsive nanocarriers using trimethylchitosans and methacrylic acid copolymer for siRNA delivery

RNA interference-based therapies are dependent on intracellular delivery of siRNA. The release of siRNA from the endosomal compartment may be a rate limiting step in the transfection process. The purpose of this study was to produce pH-responsive nanocarriers made of trimethylchitosan (TMC). To this end, pH-sensitive methacrylic acid (MAA) copolymer was added to TMC-siRNA formulations. Four different TMCs associated or not with MAA were evaluated as siRNA carriers. Nanoparticles were characterized in terms of size, surface charge, morphology and interaction with siRNA. A swelling behaviour due to a decrease in pH was observed and was found to be dependent on MAA content in the complexes. In vitro experiments aimed at evaluating how the capacity of the nanocarriers to transfect siRNA in L929 cells was affected by MAA content. Confocal microscopy experiments showed that fluorescent MAA-containing particles exhibit a different distribution pattern inside the cells comparing to their counterpart without this pH-sensitive polymer. Transfection efficiency was investigated by RhoA mRNA expression inhibition. MAA-TMC-siRNA complexes were able to transfect L929 cells with greater efficiency than corresponding TMC-siRNA complexes. This study gives an insight into the opportunity of pH-sensitive nanocarriers for siRNA delivery. Such formulations may represent an attractive strategy to improve endosomal escape of siRNA.

Trimethyl chitosan and its applications in drug delivery

Chitosan, a polymer obtained by deacetylation of chitin is widely studied for its pharmaceutical and nonpharmaceutical applications. Recommendations about uses of this polymer although could not be always realized due to limited solubility. Chitosan, for example, has been extensively evaluated for its mucoadhesive and absorption enhancement properties. The positive charge on the chitosan molecule gained by acidic environment in which it is soluble seems to be important for absorption enhancement. However chitosan is not soluble in medium except below pH 5.6. This limits its use as permeation enhancer in body compartments where pH is high. In this regard there is a need for chitosan derivatives with increased solubility, especially at neutral and basic pH values. Trimethylation of chitosan is an effort in this direction. Despite the abundance of the research related to trimethyl chitosan (TMC), the overview of the topic is not available. Hence an attempt is made in this review to cover the recent findings pertaining to synthesis, characterization and applications of TMC especially in pharmaceutical field. TMC has been synthesized by different ways and characterized by FTIR, NMR, DSC etc. This quaternized derivative of chitosan possesses a positive charge and is soluble over a wide range of pH. TMC, being a derivative of cationic polymer enriched with positive charge shows better mucoadhesive, permeation enhancement, drug delivery and DNA delivery properties. TMC can be further derivitized or grafted for modulating properties as solubility, cytotoxicity or cell recognition ability. Apart from these applications, TMC itself and its derivatives exhibit antimicrobial properties also. Quaternization of chitosan not only with methyl group but higher group as ethyl or along with spacer or quaternization of modified chitosan can be of interest too.

Biocompatibility of injectable chitosan-phospholipid implant systems

Injectable biomaterials are desirable therapeutic platforms due to minimal invasiveness and improved patient compliance, and are applicable in such areas as compound delivery and tissue engineering. The present work examined the biocompatibility of injectable blends composed of chitosan, phospholipid and lauric aldehyde (PoLi(gel)-LA) or lauric chloride (PoLi(gel)-LCl). In vitro cytotoxicity was evaluated in L929 and HeLa cell lines. Both blends resulted in acceptable biocompatibility, although greater cell viability was seen with PoLi(gel)-LA. In vivo biocompatibility was investigated in healthy CD-1 mice. Subcutaneous injection of the PoLi(gel)-LA blend caused no local or systemic toxicities over a four-week period while the PoLi(gel)-LCl caused immediate local toxicity. Mice injected intraperitoneally with PoLi(gel)-LA did not show physical or behavioural alterations, and body weight changes did not differ from control animals. Furthermore, histological examination of spleen and liver showed unaltered morphology. Interleukin-6 levels in mice injected with PoLi(gel)-LA did not differ from levels of control animals (6.91+/-3.61 pg/mL versus 6.92+/-5.02 pg/mL, respectively). Biodegradation occurred progressively, with 7.4+/-5.02% of the original injected mass remaining after four weeks. Results obtained herein establish the biocompatibility of PoLi(gel)-LA and indicate its potential for use in various localized therapeutic applications.

Chitosan N-betainates/DNA self-assembly nanoparticles for gene delivery: in vitro uptake and transfection efficiency

The aim of this work is to investigate the effect of betaine substitution degree of chitosan N-betainates (CsB) on cellular uptake, cytotoxicity and transfection efficiency of CsB/DNA complex nanoparticles (CsBNs) against COS-7 and MDA-MB-468 cells. The polymers with three substitution degrees (CsB12, CsB47 and CsB85) complexed with pDNA formed CsBN12s, CsBN47s and CsBN85s. The CsBNs showed less pH dependency with smaller particle size and higher zeta potential than that of chitosan/pDNA complex nanoparticles (CsNs) at neutral pH. CsBN85s showed stronger cellular uptake than that of CsBN47s or CsBN12s. CsBNs showed higher cytotoxicity than CsNs, and a trend increasing toxicity with substitution degree increasing. In COS-7 cells, the transfection efficiency increased with the substitution degree increasing, while the opposite result was observed in MDA-MB-468 cells. Chitosan modified with betaine could increase its ability to facilitate DNA uptake and its cytotoxicity, both of which showed the influence on transfection efficiency. It was able to increase cellular uptake and transfection efficiency of complex nanoparticles in COS-7 cells to increase betaine substitution of CsB, however, the higher sensitivity of MDA-MB-468 cells to CsBs led to decreased transfection efficiency due to the increased cytotoxicity with betaine substitution increasing. The predominant role of cellular uptake or toxicity in affecting transfection efficiency was different in two cell lines. These results provided an important guidepost for further development of chitosan derivatives/pDNA complexes as non-viral gene vectors.