The safety of chitosan as a pharmaceutical excipient

Incorporation of copper into chitosan scaffolds promotes bone regeneration in rat calvarial defects

The objective of this study was to investigate the effects of a copper loaded chitosan scaffold on bone regeneration in critical-sized calvarial defects in rats. Chitosan scaffolds and copper-chitosan scaffolds were fabricated and characterized by scanning electron microscopy (SEM). Chitosan and copper-chitosan scaffolds were implanted into 5 mm diameter critical-sized calvarial defects in Fisher 344 male rats. Empty defects (no scaffolds) were included as a control. After 4 weeks, the rats were sacrificed for microcomputed tomography (micro-CT) and histological analysis of new bone tissue development. Microscopy images revealed the uniformly porous structure of chitosan and copper-chitosan scaffolds. Significant bone regeneration was noted in the defects treated with copper-chitosan scaffolds when evaluated using micro-CT and histological analysis, when compared with other groups tested. On analysis of the micro-CT scans, an eleven-fold and a two-fold increase in the new bone volume/total volume (BV/TV) % was found in defects treated with the copper-chitosan scaffolds, when compared to empty defects and chitosan scaffolds, respectively. This study demonstrated the suitability of copper-crosslinked chitosan scaffolds for bone tissue engineering and provides the first evidence that inclusion of copper ions in scaffolds can enhance tissue regeneration.

Endotoxins affect diverse biological activity of chitosans in matters of hemocompatibility and cytocompatibility

Chitosan is used in several pharmaceutical and medical applications, owing to its good cytocompatibility and hemocompatibility. However, there are conflicting reports regarding the biological activities of chitosan with some studies reporting anti-inflammatory properties while others report pro-inflammatory properties. In this regards we analyzed the endotoxin content in five different chitosans and examined these chitosans with their different deacetylation degrees for their hemocompatibility and cytocompatibility. Therefore, we incubated primary human endothelial cells or whole blood with different chitosan concentrations and studied the protein and mRNA expression of different inflammatory markers or cytokines. Our data indicate a correlation of the endotoxin content and cytokine up-regulation in whole blood for Poly-Morpho-Nuclear (PMN)-Elastase, soluble terminal complement complex SC5b-9, complement component C5/C5a, granulocyte colony-stimulating factor, Interleukin-8 (IL), IL-10, IL-13, IL-17E, Il-32α and monocyte chemotactic protein-1. In contrast, the incubation of low endotoxin containing chitosans with primary endothelial cells resulted in increased expression of E-selectin, intercellular adhesion molecule-1, vascular cell adhesion protein-1, IL-1β, IL-6 and IL-8 in endothelial cells. We suggest that the endotoxin content in chitosan plays a major role in the biological activity of chitosan. Therefore, we strongly recommend analysis of the endotoxin concentration in chitosan, before further determining if it has pro- or anti-inflammatory properties or if it is applicable for pharmaceutical and medical fields.

Chitosan hydrogel as siRNA vector for prolonged gene silencing

Background

The periodontitis is one of the most prevalent diseases with alveolar resorption in adult people and is the main cause of the tooth loss. To investigate the possibility for protecting the loss of alveolar bone in periodontal diseases, a RNAi-based therapeutic strategy is applied for silencing RANK signaling using thermosensitive chitosan hydrogel as siRNA reservoir and vector.

Results

The thermosensitive chitosan hydrogel was formed from solution (PH = 7.2, at 4°C) at 37°C within 8 minutes. The degradation rates of hydrogel were ~50% and 5% (W remaining/W beginning) in the presence and absence of lysozyme, respectively, over a period of 20 days. The concurrent cumulative in vitro release of Cy3-labeled siRNA from the hydrogel was 50% and 17% over 14 days, with or without lysozyme digestion, respectively. High cell viability (>88%) was maintained for cells treated with hydrogel loaded with RANK specific siRNA and RANK knockdown was prolonged for up to 9 days when cells were incubated with siRNA/hydrogel complex. In vivo release of siRNA was investigated in a subcutaneous delivery setup in mice. The fluorescent signal from siRNA within hydrogel was remained for up to 14 days compared to less than one day for siRNA alone.

Conclusions

Chitosan hydrogel can potentially serve as a suitable reservoir and vector for local sustained delivery of siRNA in potential therapy.

Ultrasound treatment increases transfection efficiency of low molecular weight chitosan in fibroblasts but not in KB cells

The aim of this study was to optimize transfection efficiency (TE) of the depolymerized low molecular weight (LW) chitosan with molecular weight (Mw) at 16 kDa and 54% degree of deacetylation (DDA) on three primary cells of fibroblast (F), dental pulp (P), and periodontal ligament (PDL). The effect of low frequency ultrasound treatment on the chitosan-DNA complexes prior transfection on TE was also evaluated. This LW chitosan required high N/P ratio (>34) to bind DNA completely. An N/P ratio above 56 tended to improve TE in most primary cells nearly at the level of Lipofectamine. Ultrasonication can reduce the aggregation and sizes of the chitosan-DNA microparticles. It increased TE of F cells at an N/P ratio above 34, which was higher than Lipofectamine. However, this ultrasound treatment caused loss of TE in KB cells. MTT assay of these chitosan-DNA complexes revealed no significant cytotoxicity to both KB and F cells. This LW chitosan has potential for further development into a safer alternative to gene delivery systems in various cells of interest; however the optimal conditions have to be adjusted, depending on each cell source.

Metronidazole and Pentoxifylline films for the local treatment of chronic periodontal pockets: preparation, in vitro evaluation and clinical assessment

OBJECTIVE

Periodontitis is one of the most important chronic inflammatory dental diseases arising from the destructive actions caused by a variety of pathogenic organisms presented in the oral cavity. The aim of this study is the preparation and in vitro evaluation of films for the local treatment of periodontal pockets.

METHODS

The prepared films contained either metronidazole (Mtr), for its antimicrobial effect in periodontal diseases, using a mixture of polymers namely hydroxypropyl methyl cellulose, Carbopol 934 or locally applied Pentoxifylline (PTX), for its anti-inflammatory activity, using chitosan. All films were prepared using solvent casting technique and were evaluated for their physical characteristics, drug content uniformity, surface pH, swelling behavior, mechanical properties and in vitro release. Further characterization was done on the selected formulations using differential scanning calorimetry and scanning electron microscopy for surface structure. Clinical evaluation tests were also performed.

RESULT

Appropriate physical characteristics and mechanical properties for most formulations and their suitability for periodontal application were observed. In vitro drug release from most films showed a burst release rate for both Mtr and PTX during the first 2 h after which the release rate was markedly decreased. Clinical trials on patients revealed the advantageous use of Mtr and PTX as an adjunct treatment with traditionally used dental techniques.

CONCLUSION

The effectiveness of the co-therapy of either drug could add benefit in the eradication of chronic periodontal hazards.

Mucosal co-immunization with AIM2 enhances protective SIgA response and increases prophylactic efficacy of chitosan-DNA vaccine against coxsackievirus B3-induced myocarditis

Coxsackievirus B3 (CVB3) infection is considered as the most common cause of viral myocarditis with no available vaccine. Considering that CVB3 mainly invades through the gastrointestinal mucosa, the development of CVB3-specific mucosal vaccine, which is the most efficient way to induce mucosal immune responses, gains more and more attention. In this study, we used absent in melanoma 2 (AIM2) as a mucosal adjuvant to enhance the immunogenicity and immunoprotection of CVB3-specific chitosan-pVP1 vaccine. Mice were intranasally co-immunized with 50 μg chitosan-pAIM2 and equal amount of chitosan-pVP1 vaccine 4 times at 2 week-intervals, and then challenged with CVB3 2 weeks after the last immunization. Compared with chitosan-pVP1 vaccine immunization alone, chitosan-pAIM2 co-immunization enhanced resistance to CVB3-induced myocarditis evidenced by significantly enhanced ejection fractions from 55.40 ± 9.35 to 80.31 ± 11.35, improved myocarditis scores from 1.50 ± 0.45 to 0.30 ± 0.15, reduced viral load from 3.33 ± 0.50 to 0.50 ± 0.65, and increased survival rate from 40.0% to 75.5%. This increased immunoprotection might be attributed to the augmented level of CVB3-specific fecal SIgA with high affinity and neutralizing ability. In addition, co-immunization with chitosan-pAIM2 remarkably facilitated dendritic cells (DCs) recruitment to mesenteric lymph nodes (MLN), and promoted the expression of IgA-inducing factors (BAFF, APRIL, iNOS, RALDH1, IL-6, TGF-β), which might account for its mucosal adjuvant effect. This strategy may represent a promising prophylactic vaccine against CVB3-induced myocarditis.

In vitro analysis of nanoparticulate hydroxyapatite/chitosan composites as potential drug delivery platforms for the sustained release of antibiotics in the treatment of osteomyelitis

Nanoparticulate composites of hydroxyapatite (HAp) and chitosan were synthesized by ultrasound-assisted sequential precipitation and characterized for their microstructure at the atomic scale, surface charge, drug release properties, and combined antibacterial and osteogenic response. Crystallinity of HAp nanoparticles was reduced because of the interference of the surface layers of chitosan with the dissolution/reprecipitation-mediated recrystallization mechanism that conditions the transition from the as-precipitated amorphous calcium phosphate phase to the most thermodynamically stable one--HAp. Embedment of 5-10 nm sized, narrowly dispersed HAp nanoparticles within the polymeric matrix mitigated the burst release of the small molecule model drug, fluorescein, bound to HAp by physisorption, and promoted sustained-release kinetics throughout the 3 weeks of release time. The addition of chitosan to the particulate drug carrier formulation, however, reduced the antibacterial efficacy against S aureus. Excellent cell spreading and proliferation of osteoblastic MC3T3-E1 cells evidenced on microscopic conglomerates of HAp nanoparticles in vitro also markedly diminished on HAp/chitosan composites. Mitochondrial dehydrogenase activity exhibited normal values only for HAp/chitosan particle concentrations of up to 2 mg/cm(2) and significantly dropped, by about 50%, at higher particle concentrations (4 and 8 mg/cm(2)). The gene expression of osteocalcin, a mineralization inductor, and the transcription factor Runx2 was downregulated in cells incubated in the presence of 3 mg/cm(2) HAp/chitosan composite particles, whereas the expression of osteopontin, a potent mineralization inhibitor, was upregulated, further demonstrating the partially unfavorable osteoblastic cell response to the given particles. The peak in the expression of osteogenic markers paralleling the osteoblastic differentiation was also delayed most for the cell population incubated with HAp/chitosan particles. Overall, the positive effect of chitosan coating on the drug elution profile of HAp nanoparticles as carriers for the controlled delivery of antibiotics in the treatment of osteomyelitis was compensated for by the lower bacteriostatic efficiency and the comparatively unviable cell response to the composite material, especially at higher dosages.

Antifungal activity of oligochitosans (short chain chitosans) against some Candida species and clinical isolates of Candida albicans: molecular weight-activity relationship

A series of oligochitosans (short chain chitosans) prepared by acidic hydrolysis of chitosan and characterized by their molecular weight, polydispersity and degree of deacetylation were used to determine their anticandidal activities. This study has demonstrated that oligochitosans show a high fungistatic activity (MIC 8-512 μg/ml) against Candida species and clinical isolates of Candida albicans, which are resistant to a series of classic antibiotics. Flow cytometry analysis showed that oligochitosan possessed a high fungicidal activity as well. For the first time it was shown that even sub-MIC oligochitosan concentration suppressed the formation of C. albicans hyphal structures, cause severe cell wall alterations, and altered internal cell structure. These results indicate that oligochitosan should be considered as a possible alternative/additive to known anti-yeast agents in pharmaceutical compositions.

Chitosan: a promising safe and immune-enhancing adjuvant for intranasal vaccines

The nasal route is attractive for the delivery of vaccines in that it not only offers an easy to use, non-invasive, needle-free alternative to more conventional parenteral injection, but it also creates an opportunity to elicit both systemic and (crucially) mucosal immune responses which may increase the capability of controlling pathogens at the site of entry. Immune responses to "naked" antigens are often modest and it is widely accepted that incorporation of an adjuvant is a prerequisite for the achievement of clinically effective nasal vaccines. Many existing adjuvants are sub-optimal or unsuitable because of local toxicity or poor enhancement of immunogenicity. Chitosan, particularly chitosan salts, have now been used in several preclinical and clinical studies with good tolerability, excellent immune stimulation and positive clinical results across a number of infections. Particularly significant evidence supporting chitosan as an adjuvant for nasal vaccination comes from clinical investigations on a norovirus vaccine; this demonstrated the ability of chitosan (ChiSys®), when combined with monophosphoryl lipid, to evoke robust immunological responses and confer protective immunity following (enteral) norovirus challenge. This article summarizes the totality of the meaningful information (including key unpublished data) supporting the development of chitosan-adjuvanted vaccines.

Utilization of carboxymethyl chitosan in cosmetics

Carboxymethyl chitosan is a chitosan derivative of the most intensively investigated due to its water solubility in wider pH range compared with the parent compound, thus extended its use in various applications. In this review, different preparation conditions, which resulting in the N- and O-carboxylated chitosan, diverse degree of substitution and water solubility are recapitulated. Five important features of carboxymethyl chitosan from recent studies, which are moisture absorption-retention, anti-microbial properties, antioxidant capacities, delivery system and emulsion stabilization, have been centred and emphasized for cosmetic utilization. Additionally, cytotoxicity information has been inclusively incorporated to ensure its safety in application.

Delivery of natural polyphenols by polymeric nanoparticles improves the resistance of endothelial progenitor cells to oxidative stress

PURPOSE

Bone marrow-derived endothelial progenitor cells (EPCs) circulate into peripheral blood and significantly contribute to neo-vascularisation and re-endothelialisation as part of the process of vascular repair. Several studies have reported decreased EPC number in the presence of oxidative stress. Aim of this study was to evaluate the validity of mucoadhesive polymeric nanoparticles as a delivery system of natural products able to protect EPCs from oxidative stress.

METHODS

The total polyphenol content and antioxidant capacity of red grape seed extract (GSE) either pre-veraison (p-GSE) or ripe (r-GSE) were measured. Cell viability was evaluated by WST-1 assay. Nanoparticles were prepared by ionotropic crosslinking of two structurally different thiolated quaternary ammonium-chitosan conjugates. A hyaluronic acid solution, containing p-GSE or r-GSE, was added to a stirred solution of each of the two chitosan derivatives to obtain p- or r-GSE loaded nanoparticles (NP) of two types.

RESULTS

Both GSE types demonstrated strong antioxidant capacity. p-GSE showed a higher content in total polyphenols compared to r-GSE. NP size was in the 310-340 nm range, with 24 h stability, and nearly 100% encapsulation efficiency for both GSE types. NP were internalized by cells to an extent related directly with their surface charge intensity. GSE-NP uptake significantly improved cell viability and resistance to oxidation.

CONCLUSIONS

Nanotechnology has a great potential in nutraceutical delivery. The present results suggest that NP is a highly promising polyphenol carrier system particularly useful to protect EPCs from oxidative stress, thus improving their survival.

Chitosan-based siRNA delivery systems

Recently, chitosan has attracted significant attention in the formulation of small interfering RNA (siRNA). Because of its cationic nature, chitosan can easily complex siRNA, thus readily forming nanoparticles. Moreover, chitosan is biocompatible and biodegradable, which make it a good candidate for siRNA delivery in vivo. However, chitosan requires further development to achieve high efficiency. This review will describe the major barriers that impair the efficiency of the chitosan-based siRNA delivery systems, including the stability of the delivery system in biological fluids and endosomal escape. Several solutions to counteract these barriers have been developed and will be discussed. The parameters to consider for designing powerful delivery systems will be described, particularly the possibilities for grafting targeting ligands. Finally, optimized systems that allow in vivo therapeutic applications for both local and systemic delivery will be reviewed. This review will present recent improvements in chitosan-based siRNA delivery systems that overcome many of these system's previous pitfalls and pave the way to a new generation of siRNA delivery systems.

Rheological study of chitosan/polyol-phosphate systems: influence of the polyol part on the thermo-induced gelation mechanism

Thermo-sensitive gelling systems, like chitosan/polyol-phosphate, are candidates with a high potential for the design of biodegradable drug delivery systems, notably for in situ forming depots. They consist of stable and low viscosity aqueous solutions, liquid at room temperature, which turn into a gel state upon an increase of temperature (e.g., after subcutaneous administration). This technology enables a sustained release of potentially encapsulated active substances. Despite these thermo-gelling solutions being widely studied for the development of parenteral drug delivery systems, most commonly using β-glycerophosphate (β-GP) as gelling agent, the mechanism inducing the gelation and the role of the polyol part in this mechanism has not been clearly elucidated. To investigate the mechanism of the gelation process, comprehensive rheological studies were performed, comparing different chitosan/polyol-phosphate systems varying in the chemical structure of the polyol parts of the gelling agents. As reference, β-GP was compared to glucose-1-phosphate (G1-P) and glucose-6-phosphate (G6-P) and to a polyol-free phosphate salt, Na2HPO4, as well. Frequency sweep experiments at different temperatures or different gelling agent concentrations, temperature, and time sweep tests were performed as complementary experimental approaches. The results disclosed significant trends with widespread implications, establishing a relationship between the chemical structure of the polyol part and the macroscopic gelling behavior of the solutions, that is, transition temperature, gelation time, and gel strength. The new results presented in this study show that increasing the size of the polyol part prevents the interactions between the chitosan chains, strongly influencing the gelling process.

Blood contact properties of ascorbyl chitosan

Ascorbyl chitosan was synthesized by heating chitosan with ascorbic acid in isopropanol. The products were characterized by FTIR and C-13 NMR spectroscopies, SEM, and elemental analysis. Blood contact properties of ascorbyl chitosans were evaluated. The ascorbyl chitosans demonstrated to have increased lipid-lowering activity in comparison to chitosan alone upon contact with human blood serum in in vitro conditions. Furthermore, the total cholesterol/HDL ratio was improved towards the desirable ideal values after three hours contact with ascorbyl chitosan samples. The lipid-lowering activity increased with ascorbyl substitution. The inherent nonspecific adsorption capability of chitosan due to its chelating power with several different functional groups was exhibited by ascorbyl chitosans as well. This behavior was exemplified in a simultaneous decrease in the total iron values of the volunteers together with lower lipid levels. Furthermore, ascorbyl chitosans were observed to have less hemocompatibility but increased anticoagulant activity when compared to chitosan alone. Additional in vivo studies are necessary to support these results and to investigate further the advantages and disadvantages of these materials to prove their safety prior to clinical applications.

Chitosan nanoparticles for ocular delivery of cyclosporine A

In the present study, cyclosporine A (CsA) was successfully incorporated into cationic chitosan nanoparticles by spray-drying method aiming ocular application. Physicochemical characterisation of particles was performed in detail. Among the particles prepared using three types of chitosan with different molecular weights, particles containing chitosan with medium molecular weight was selected for in vivo studies. Selection was dependent on higher incorporation and encapsulation efficiencies of CsA and also better release characteristic in simulated tear fluid. Sheep were used in in vivo studies. Biological samples were collected at predetermined time intervals and were analysed by enzyme immune assay. CsA could be detected in both aqueous and vitreous humour samples for the duration of 72 h. In vivo release profiles indicated prolonged release of active agent from positively charged chitosan formulations. This may be attributed to enhanced residence time at the corneal and conjunctival surfaces.

Eco-friendly chitosan production by Syncephalastrum racemosum and application to the removal of acid orange 7 (AO7) from wastewaters

Due to the existence of new methodologies that have reduced the production costs of microbiological chitosan, this paper puts forward the use of agro-industrial residues in order to produce microbiological chitosan and to apply chitosan as an innovative resource for removing acid orange 7 (AO7) from wastewaters. The best culture conditions were selected by a full 2⁴ factorial design, and the removal of the dye was optimized by a 2³ central composite rotational design. The results showed that corn steep liquor (CSL) is an agro-industrial residue that can be advantageously used to produce microbiological chitosan with yields up to 7.8 g/kg of substrate. FT-IR spectra of the product showed typical peak distributions like those of standard chitosan which confirmed the extracted product was chitosan-like. The efficiency of removing low concentrations of AO7 by using microbiological chitosan in distilled water (up to 89.96%) and tap water (up to 80.60%) was significantly higher than the efficiency of the control (chitosan obtained from crustaceans), suggesting that this biopolymer is a better economic alternative for discoloring wastewater where a low concentration of the dye is considered toxic. The high percentage recovery of AO7 from the microbiological chitosan particles used favors this biopolymer as a possible bleaching agent which may be reusable.

Importance and globalization status of good manufacturing practice (GMP) requirements for pharmaceutical excipients

Pharmaceutical excipients are no longer inert materials but it is effective and able to improve the characteristics of the products' quality, stability, functionality, safety, solubility and acceptance of patients. It can interact with the active ingredients and alter the medicament characteristics. The globalization of medicines' supply enhances the importance of globalized good manufacturing practice (GMP) requirements for pharmaceutical excipients. This review was intended to assess the globalization status of good manufacturing practice (GMP) requirements for pharmaceutical excipients. The review outcomes demonstrate that there is a lack of accurately defined methods to evaluate and measure excipients' safety. Furthermore good manufacturing practice requirements for excipients are not effectively globalized.

New nerve regeneration strategy combining laminin-coated chitosan conduits and stem cell therapy

Nerve regeneration remains a difficult challenge due to the lack of safe and efficient matrix support. We designed a laminin (LN)-modified chitosan multi-walled nerve conduit combined with bone marrow stem cell (BMSC) grating to bridge a 10 mm long gap in the sciatic nerve of Sprague-Dawley rats. The repair outcome was monitored during 16 weeks after surgery. Successful grafting of LN onto the chitosan film, confirmed by immunolocalization, significantly improved cell adhesion. In vivo study showed that newly formed nerve cells covered the interior of the conduit to connect the nerve gap successfully in all groups. The rats implanted with the conduit combined with BMSCs showed the best results, in terms of nerve regrowth, muscle mass of gastrocnemius, function recovery and tract tracing. Neuroanatomical horseradish peroxidase tracer analysis of motor neurons in the lumbar spinal cord indicated that the amount and signal intensity were significantly improved. Furthermore, BMSCs suppressed neuronal cell death and promoted regeneration by suppressing the inflammatory and fibrotic response induced by chitosan after long-term implantation. In summary, this study suggests that LN-modified chitosan multi-walled nerve conduit combined with BMSCs is an efficient and safe conduit matrix for nerve regeneration.

Novel albendazole-chitosan nanoparticles for intestinal absorption enhancement and hepatic targeting improvement in rats

To improve the treatment of helminthiasis, filariasis, and colorectal cancer, albendazole-associated chitosan nanoparticles (ABZ-CS-NPs) were prepared using the emulsion crosslinking volatile technique with contained sodium tripolyphosphate as the crosslinking agent and Poloxamer 188 as the auxiliary solvent. The structural characteristics of the NPs were determined using X-ray diffraction to analyze the interaction between CS and the drug. The NPs were then evaluated in terms of their physicochemical characteristics, drug release behavior, in vivo pharmacokinetic parameters, and biodistribution in animal studies. ABZ-loaded NPs with a uniformly spherical particle sizes (157.8 ± 2.82 nm) showed efficient drug loading, encapsulated efficiency, and high physical stability. The drug release from ABZ-CS-NPs was extended over several periods. Kinetic models were then fitted to determine the release mechanisms. ABZ and its metabolite albendazole sulfoxide (ABZSX) were analyzed in rats with mebendazole as the internal standard using reversed-phase high-performance liquid chromatography. Compared with the ABZ suspension groups, the relative bioavailability values of ABZ and ABZSX were 146.05 and 222.15%, respectively. In addition, the plasma concentration versus time curve is consistent with that of the two compartment models in the plasma concentration versus time curve. The results indicate that the ABZ-loaded NPs are promising novel ABZ candidates for passive diffusion in the treatment of hydatid cysts in the liver via oral administration.

Charge affects the oral toxicity of poly(amidoamine) dendrimers

Poly(amidoamine) (PAMAM) dendrimers have been evaluated for the influence of surface functionality and size on the epithelial barrier of the gut with the goal of identifying safe carriers that can be used for oral drug delivery. Limited studies are conducted to date, however, to assess the toxicity of PAMAM dendrimers in vivo when administered by the oral route. The goal of this research was to conduct an oral acute toxicity study of PAMAM dendrimers as a function of size and charge in immune competent CD-1 mice. Maximum tolerated doses (MTD) of PAMAM dendrimers as a function of size and surface functionality were established and clinical signs of toxicity monitored. Results demonstrate that positively charged dendrimers caused more toxicity, whereas their anionic counterparts were tolerated at ten times higher doses. Severe signs of toxicity observed for large (G7) cationic amine- or hydroxyl-terminated dendrimers include hemobilia and spleenomegaly. The MTD for these dendrimers ranged from 30 mg/kg to 200 mg/kg. Anionic G6.5 or smaller molecular weight carboxyl-, amine-, or hydroxyl-terminated dendrimers (G3.5-COOH, G4-NH2, G4-OH) on the other hand were tolerated at doses of up to 500 mg/kg (300 mg/kg in some cases) with minimal or no signs of toxicity. Establishing the MTD of orally delivered PAMAM dendrimers and the influence of surface functionality and size on toxicity aids in the rational design of PAMAM-drug conjugates for oral drug delivery applications.

Injectable and biodegradable thermosensitive hydrogels loaded with PHBHHx nanoparticles for the sustained and controlled release of insulin

Biodegradable PHBHHx (poly(3-hydroxybutyrate-co-3-hydroxyhexanoate)) nanoparticles containing insulin phospholipid complex were loaded in chitosan-based thermosensitive hydrogels for long-term sustained and controlled delivery of insulin. The injectable hydrogels, prepared by adding β-glycerophosphate disodium salt (GP) solution to chitosan (CS) solution under stirring, showed a rapid solution-to-gel transition at 37 °C, a porous structure and a comparative degradation and swelling rate in vitro. In the in vitro release studies, only 19.11% of total insulin was released from the nanoparticle-loaded hydrogel (NP-CS/GP) within 31 days. However, 96.41% of total insulin was released from the free insulin-loaded hydrogel (INS-CS/GP) within 16 days. Most importantly, the hypoglycemic effect of NP-CS/GP following subcutaneous injection in diabetic rats lasted for >5 days, much longer than the effect caused by INS-CS/GP or other long-acting insulin formulations. The pharmacological availability of NP-CS/GP relative to INS-CS/GP was 379.85%, indicating that the bioavailability of insulin was significantly enhanced by NP-CS/GP gels. Therefore, biodegradable and thermosensitive NP-CS/GP gels have great potential for use in novel ultralong-acting insulin injections. In addition, the NP-loaded hydrogel system also paves the way for long-term delivery of other proteins and peptides.

Nanoparticle mediated P-glycoprotein silencing for improved drug delivery across the blood-brain barrier: a siRNA-chitosan approach

The blood-brain barrier (BBB), composed of tightly organized endothelial cells, limits the availability of drugs to therapeutic targets in the central nervous system. The barrier is maintained by membrane bound efflux pumps efficiently transporting specific xenobiotics back into the blood. The efflux pump P-glycoprotein (P-gp), expressed at high levels in brain endothelial cells, has several drug substrates. Consequently, siRNA mediated silencing of the P-gp gene is one possible strategy how to improve the delivery of drugs to the brain. Herein, we investigated the potential of siRNA-chitosan nanoparticles in silencing P-gp in a BBB model. We show that the transfection of rat brain endothelial cells mediated effective knockdown of P-gp with subsequent decrease in P-gp substrate efflux. This resulted in increased cellular delivery and efficacy of the model drug doxorubicin.

Multi-functional roles of chitosan as a potential protective agent against obesity

Chitosan, a natural polysaccharide comprising copolymers of glucosamine and N-acetylglucosamine, has been shown to have anti-obesity properties. Two experiments (Exp. 1 and Exp. 2) were performed to determine the role of chitosan on dietary intake, body weight gain, and fat deposition in a pig model, as well as identifying potential mechanisms underlying the anti-obesity effect of chitosan. In Exp. 1, the nutrient digestibility experiment, 16 pigs (n = 4/treatment) were randomly allocated to one of four dietary treatments as follows: 1) basal diet; 2) basal diet plus 300 ppm chitosan; 3) basal diet plus 600 ppm chitosan; 4) basal diet plus 1200 ppm chitosan. The main observation was that crude fat digestibility was lower in the 1200 ppm chitosan group when compared with the control group (P<0.05). In Exp. 2, a total of 80 pigs (n = 20/treatment) were offered identical dietary treatments to that offered to animals in Exp. 1. Blood samples were collected on day 0, day 35 and at the end of the experiment (day 57). Animals offered diets containing 1200 ppm chitosan had a lower daily dietary intake (P<0.001) and body weight gain (P<0.001) from day 35 to 57 when compared with all the other treatment groups. Animals offered diets containing 1200 ppm chitosan had a significantly lower final body weight (P<0.01) when compared with all the other treatment groups. The decreased dietary intake observed in the 1200 ppm chitosan group was associated with increased serum leptin concentrations (P<0.001) and a decrease in serum C-reactive protein (CRP) concentrations (P<0.05). In conclusion, the results of this study highlight novel endocrine mechanisms involving the modulation of serum leptin and CRP concentrations by which chitosan exhibits anti-obesity properties in vivo.

A study of Chitosan and c-di-GMP as mucosal adjuvants for intranasal influenza H5N1 vaccine

BACKGROUND

Highly pathogenic avian influenza A/H5N1 virus remains a potential pandemic threat, and it is essential to continue vaccine development against this subtype. A local mucosal immune response in the upper respiratory tract may stop influenza transmission. It is therefore important to develop effective intranasal pandemic influenza vaccines that induce mucosal immunity at the site of viral entry.

OBJECTIVES

We evaluated the humoral and cellular immune responses of two promising mucosal adjuvants (Chitosan and c-di-GMP) for intranasal influenza H5N1 vaccine in a murine model. Furthermore, we evaluated the concept of co-adjuvanting an experimental adjuvant (c-di-GMP) with chitosan.

METHODS

BALB/c mice were intranasally immunised with two doses of subunit NIBRG-14 (H5N1) vaccine (7·5, 1·5 or 0·3 μg haemagglutinin (HA) adjuvanted with chitosan (CSN), c-di-GMP or both adjuvants.

RESULTS

All adjuvant formulations improved the serum and local antibody responses, with the highest responses observed in the 7·5 μg HA CSN and c-di-GMP-adjuvanted groups. The c-di-GMP provided dose sparing with protective single radial haemolysis (SRH), and haemagglutination inhibition (HI) antibody responses found in the 0·3 μg HA group. CSN elicited a Th2 response, whereas c-di-GMP induced higher frequencies of virus-specific CD4+T cells producing one or more Th1 cytokines (IFN-γ+, IL-2+, TNF-α+). A combination of the two adjuvants demonstrated effectiveness at 7·5 μg HA and triggered a more balanced Th cytokine profile.

CONCLUSION

These data show that combining adjuvants can modulate the Th response and in combination with ongoing studies of adjuvanted intranasal vaccines will dictate the way forward for optimal mucosal influenza vaccines.

Green synthesis approach: extraction of chitosan from fungus mycelia

Chitosan, copolymer of glucosamine and N-acetyl glucosamine is mainly derived from chitin, which is present in cell walls of crustaceans and some other microorganisms, such as fungi. Chitosan is emerging as an important biopolymer having a broad range of applications in different fields. On a commercial scale, chitosan is mainly obtained from crustacean shells rather than from the fungal sources. The methods used for extraction of chitosan are laden with many disadvantages. Alternative options of producing chitosan from fungal biomass exist, in fact with superior physico-chemical properties. Researchers around the globe are attempting to commercialize chitosan production and extraction from fungal sources. Chitosan extracted from fungal sources has the potential to completely replace crustacean-derived chitosan. In this context, the present review discusses the potential of fungal biomass resulting from various biotechnological industries or grown on negative/low cost agricultural and industrial wastes and their by-products as an inexpensive source of chitosan. Biologically derived fungal chitosan offers promising advantages over the chitosan obtained from crustacean shells with respect to different physico-chemical attributes. The different aspects of fungal chitosan extraction methods and various parameters having an effect on the yield of chitosan are discussed in detail. This review also deals with essential attributes of chitosan for high value-added applications in different fields.

Adjuvants and inactivated polio vaccine: a systematic review

Poliomyelitis is nearing universal eradication; in 2011, there were 650 cases reported globally. When wild polio is eradicated, global oral polio vaccine (OPV) cessation followed by use of universal inactivated polio vaccine (IPV) is believed to be the safest vaccination strategy as IPV does not mutate or run the risk of vaccine derived outbreaks that OPV does. However, IPV is significantly more expensive than OPV. One strategy to make IPV more affordable is to reduce the dose by adding adjuvants, compounds that augment the immune response to the vaccine. No adjuvants are currently utilized in stand-alone IPV; however, several have been explored over the past six decades. From aluminum, used in many licensed vaccines, to newer and more experimental adjuvants such as synthetic DNA, a diverse group of compounds has been assessed with varying strengths and weaknesses. This review summarizes the studies to date evaluating the efficacy and safety of adjuvants used with IPV.

Biocompatibility of chitosan carriers with application in drug delivery

Chitosan is one of the most used polysaccharides in the design of drug delivery strategies for administration of either biomacromolecules or low molecular weight drugs. For these purposes, it is frequently used as matrix forming material in both nano and micron-sized particles. In addition to its interesting physicochemical and biopharmaceutical properties, which include high mucoadhesion and a great capacity to produce drug delivery systems, ensuring the biocompatibility of the drug delivery vehicles is a highly relevant issue. Nevertheless, this subject is not addressed as frequently as desired and even though the application of chitosan carriers has been widely explored, the demonstration of systems biocompatibility is still in its infancy. In this review, addressing the biocompatibility of chitosan carriers with application in drug delivery is discussed and the methods used in vitro and in vivo, exploring the effect of different variables, are described. We further provide a discussion on the pros and cons of used methodologies, as well as on the difficulties arising from the absence of standardization of procedures.