Chitosan as a nasal delivery system: evaluation of insulin absorption enhancement and effect on nasal membrane integrity using rat models

A novel dry powder influenza vaccine and intranasal delivery technology: induction of systemic and mucosal immune responses in rats

Intranasal (i.n.) vaccination represents an attractive non-invasive alternative to needle-based injection and provides superior protection at mucosal surfaces. However, new formulations are needed to improve efficacy and reduce the refrigerated storage and distribution requirements associated with standard liquid vaccines. Here, we describe a powder formulation of whole inactivated influenza virus and a novel i.n. delivery platform. The powder-formulated vaccine elicited a significant serum antibody response in rats that was at least as strong as that provided by the liquid vaccine administered i.n. or via intramuscular (i.m.) injection. Significant nasal IgA responses were also observed solely after i.n. delivery. This study demonstrates for the first time the generation of potent nasal mucosal and systemic immune responses using an i.n. delivered influenza vaccine powder and suggests an alternative approach to vaccination against influenza and other infectious diseases.

Low molecular weight chitosan nanoparticles as new carriers for nasal vaccine delivery in mice

High molecular weight (Mw) chitosan (CS) solutions have already been proposed as vehicles for nasal immunization. The aim of the present work was to investigate the potential utility of low Mw CS in the form of nanoparticles as new long-term nasal vaccine delivery vehicles. For this purpose, CS of low Mws (23 and 38 kDa) was obtained previously by a depolymerization process of the commercially available CS (70 kDa). Tetanus toxoid (TT), used as a model antigen, was entrapped within CS nanoparticles by an ionic cross-linking technique. TT-loaded nanoparticles were first characterized for their size, electrical charge, loading efficiency and in vitro release of antigenically active toxoid. The nanoparticles were then administered intranasally to conscious mice in order to study their feasibility as vaccine carriers. CS nanoparticles were also labeled with FITC-BSA and their interaction with the rat nasal mucosa examined by confocal laser scanning microcopy (CLSM). Irrespective of the CS Mw, the nanoparticles were in the 350 nm size range, and exhibited a positive electrical charge (+40 mV) and associated TT quite efficiently (loading efficiency: 50-60%). In vitro release studies showed an initial burst followed by an extended release of antigenically active toxoid. Following intranasal administration, TT-loaded nanoparticles elicited an increasing and long-lasting humoral immune response (IgG concentrations) as compared to the fluid vaccine. Similarly, the mucosal response (IgA levels) at 6 months post-administration of TT-loaded CS nanoparticles was significantly higher than that obtained for the fluid vaccine. The CLSM images indicated that CS nanoparticles can cross the nasal epithelia and, hence, transport the associated antigen. Interestingly, the ability of these nanoparticles to provide improved access to the associated antigen to the immune system was not significantly affected by the CS Mw. Indeed, high and long-lasting responses could be obtained using low Mw CS molecules. Furthermore, the response was not influenced by the CS dose (70-200 microg), achieving a significant response for a very low CS dose. In conclusion, nanoparticles made of low Mw CS are promising carriers for nasal vaccine delivery.

The depolymerization of chitosan: effects on physicochemical and biological properties

Chitosan has been extensively used as an absorption enhancer for macromolecules and as gene delivery vehicle. Both properties are molecular weight (MW) dependent. Here, we investigate factors affecting the oxidative depolymerization of chitosan and physicochemical properties of the resulting polymer fractions including their cytotoxicity. The molecular weight of the depolymerized chitosan was influenced by the initial concentration and the source of chitosan. At constant initial concentrations, the molecular weight decreased linearly with the chitosan/NaNO2 ratio and was a function of logarithm of the reaction time. Chitosan with larger molecular weight was more sensitive to depolymerization. No structural change was observed during the depolymerization process by infrared and proton nuclear magnetic resonance spectroscopy. In addition, thermal properties of chitosan fragments were studied by thermal gravimetric analysis and it was found that the decomposition temperature was molecular weight dependent. Furthermore, the solubility of different molecular weight chitosan was assayed as a function of pH and it increased with decreasing molecular weight. The cytotoxicity of chitosan was concentration dependent but almost molecular weight independent according to MTT assay using L929 cell line recommended by USP26. In summary, low molecular weight fractions of chitosan may potentially useful for the design of drug delivery systems due to the improved solubility properties.

Glycol chitosan improves the efficacy of intranasally administrated replication defective human adenovirus type 5 expressing glycoprotein D of bovine herpesvirus 1

The ability of two soluble formulations, namely chitosan and glycol chitosan, when used as an intranasal adjuvant, to improve the immunogenicity of an intranasal human adenovirus type 5 replication defective expressing bovine herpesvirus 1 (BoHV-1) glycoprotein D based vaccine, was investigated in cattle. Their adjuvant effects on immune response by increasing clinical and especially virological protection against an intranasal BoHV-1 challenge were then evaluated. The best virological protection was obtained in calves immunized with the vaccine vector adjuvanted with glycol chitosan which decreased the challenge BoHV-1 virus excretion titres by 0.5-1.5 log when compared to those obtained in calves immunized with the vaccine vector alone or adjuvanted with chitosan. A slight difference in clinical scores was observed in calves immunized with the adjuvanted vaccine vector compared to calves immunized with the vaccine vector alone. The obtained data suggest that the tested soluble formulation of glycol chitosan has promising potential use as an intranasal adjuvant for recombinant viral vector vaccines in cattle.

Absorption enhancers for nasal drug delivery

This paper describes the basic concepts for the transmucosal delivery of drugs, and in particular the use of the nasal route for delivery of challenging drugs such as polar low-molecular-weight drugs and peptides and proteins. Strategies for the exploitation of absorption enhancers for the improvement of nasal delivery are discussed, including consideration of mechanisms of action and the correlation between toxic effect and absorption enhancement. Selected enhancer systems, such as cyclodextrins, phospholipids, bioadhesive powder systems and chitosan, are discussed in detail. Examples of the use of these enhancers in preclinical and clinical studies are given. Methods for assessing irritancy and damage to the nasal membrane from the use of absorption enhancers are also described. Finally, the mucosal use of absorption enhancers (chitosan) for the improved nasal delivery of vaccines is reported with reference to recent phase I/II clinical studies.

Transdermal administration of bromocriptine

Bromocriptine (BRC) has been mainly used for the inhibition of lactation, treatment of menstrual disorders, Parkinson disease, breast tumours, infertility and brain tumours as a dopamine agonist in clinics. But current BRC formulations have some side effects and bioavailability problems because of hepatic first pass effect. Transdermal application could be an alternative route to overcome all these problem and penetration properties of BRC has not been studied yet. Therefore, it was aimed to investigate the effectiveness of transdermal formulation of BRC which is applicable to the skin. For this purpose, a number of BRC gel formulations (Carbopol-934 (C-934), chitosan (CH) and Gantrez-SP215 (G-SP215) were developed and the effectiveness and bioavailability of the formulations were compared in rabbits. Commercial BRC tablets (Parlodel) were also given to rabbits orally and plasma levels were compared. The effects of two different penetration enhancers, sodium taurocholate (ST) and ethoxydiglycol-Transcutol) (TR) on the BRC penetration were also investigated. The skin samples from the dorsal part of the rabbit were removed after CH gel application and investigated under electron microscope to understand the effects of the gel on the penetration and the possible penetration mechanisms through skin were also discussed. In conclusion, CH gel formulation was found to be the best formulation and comparable blood BRC concentrations were obtained when applied to the rabbit skin. Higher blood levels were obtained with the use of CH. The main penetration process was found to be through transcellular route but some other mechanisms were also found to be incorporated, after microscopic investigation. CH gel was found to be a useful carrier for BRC administration through dermal route and the penetration enhancing effect and the mechanism of CH gel were first established in this study. It was concluded that transdermal delivery of BRC may be a very promising alternative route to the oral route for the treatment.

Analysis of transient and reversible effects of poly-L-arginine on the in vivo nasal absorption of FITC-dextran in rats

We have investigated whether poly-L-arginine, with a mean molecular weights of 8.9 and 45.5 kDa (poly-L-Arg (10) and poly-L-Arg (50)), can induce transient and reversible effects involving enhancement of the nasal absorption of fluorescein isothiocyanate-labeled dextran (MW 4.4 kDa, FD-4) and determined the main pathway for the increased transport of FD-4 in rats in vivo. Pre-administration and repeated administration studies were conducted involving the selection of different time intervals between intranasal administration of poly-L-Arg and administration of FD-4, with and without poly-L-Arg, to characterize these transient and reversible effects. The degradation of poly-L-Args in a diluted nasal drip was determined from the fluorescence of degraded poly-L-Arg-fluorescamine products. In the pre-administration study, poly-L-Arg exhibited a transient effect on the increased nasal FD-4 absorption depending on its molecular weight, associated with the degradation rate of poly-L-Arg in mucus. In the repeated administration study, additional poly-L-Arg produced similarly enhanced FD-4 absorption. Confocal laser scanning microscopy showed that fluorescence of FD-4 after co-administration of poly-L-Arg (50) was confined mainly to the paracellular spaces. In conclusion, poly-L-Arg exhibited molecular weight-dependent transient and reversible effects on the enhancement of nasal FD-4 absorption paracellularly in rats in vivo. The enzymatic degradation of poly-L-Arg is one of the key determinants of the transient effect on in vivo enhanced absorption of FD-4.

Physical characterization of a chitosan-based hydrogel delivery system

Hydrogel formation from a mixture of biocompatible chitosan, beta-glycerol phosphate, and hydroxyethyl cellulose was studied. The rheological properties of the formed hydrogels were examined using a Bohlin VOR rheometer. The effect of hydrogel composition and temperature on both the gelation rate and the elastic strength of hydrogels was investigated, from which possible hydrogel formation mechanisms were inferred. The formed hydrogels as potential vehicles for delivering pilocarpine were examined. The advantages and disadvantages of chitosan/hydroxyethyl cellulose hydrogel as a delivery system are discussed.

Anticancer activity of mycobacterial DNA: effect of formulation as chitosan nanoparticles

Mycobacterium phlei (M. phlei) DNA inhibits cancer cell division but is susceptible to degradation by DNase. Chitosan forms nanoparticulate polyelectrolyte complexes with DNA, and may thus reduce nuclease degradation. We have characterized chitosan-DNA nanoparticle formation, determined DNase susceptibility, and evaluated their antiproliferative activity. Nanoparticle diameter initially decreased with increasing phosphate charge density. However nanoparticle diameter increased above 6 micromol of phosphate. Particle aggregation occurred at 16.2 micromol phosphate and was related to reduced surface charge. Incorporation of DNA within chitosan nanoparticles significantly decreased degradation by DNase. The ability of M. phlei DNA-chitosan nanoparticles to inhibit melanoma cell division was determined relative to M. phlei DNA and a cationic liposomal M. phlei DNA formulation. M. phlei DNA had antiproliferative activity (MTT reduction, IC50 = 0.9 mg/ml) without intrinsic cytotoxicity (LDH release, ED50 > 50 microg/ml). Cationic polyphosphate chitosan nanoparticles were inert (antiproliferative IC50 > 1 mg/ml, ED50 > 1 mg/ml). M. phlei DNA-chitosan nanoparticles were 20-fold more potent than M. phlei DNA. Cationic DOTAP/DOPE liposomes were cytostatic (IC50 = 49 microg/ml) and cytotoxic (ED50 = 87 microg/ml), and complexation of M. phlei DNA resulted in a significant reduction of antiproliferative activity. Chitosan nanoparticles may therefore be appropriate delivery vehicles for M. phlei DNA.

Aminated gelatin as a nasal absorption enhancer for peptide drugs: evaluation of absorption enhancing effect and nasal mucosa perturbation in rats

This study was carried out to evaluate the potential of aminated gelatin as a nasal absorption enhancer for peptide drugs. The absorption-enhancing effect was investigated in rats using insulin and fluorescein isothiocyanate-dextran with a molecular weight of 4.4 kDa (FD-4) as model drugs. The absorption of insulin was estimated by measuring the changes in plasma glucose levels following intranasal administration, and that of FD-4 was determined by measuring its plasma concentration after dosing. The hypoglycaemic effect after intranasal administration of insulin with aminated gelatin significantly increased compared with that after intranasal administration of insulin in phosphate buffered saline, indicating that aminated gelatin effectively enhanced the nasal absorption of insulin. In contrast, neither kind of native gelatin (isoelectric point = 5.0 and 9.0) showed any absorption-enhancing effect. The pH of the formulations and the concentration of aminated gelatin were found to affect the hypoglycaemic effect. In addition, aminated gelatin at a concentration of 0.2% significantly enhanced the absorption and the efflux of FD-4 through the rat nasal mucosa. The possible perturbation of aminated gelatin to nasal mucosa was evaluated by measuring the leaching of lactate dehydrogenase (LDH) using an in-situ perfusion rat model. Aminated gelatin presented a concentration-dependent (0.1-0.4%) but relatively small effect on the LDH leaching from the rat nasal epithelial membrane. These results suggest that positively charged aminated gelatin could be a new absorption enhancer for nasal delivery of peptide drugs.

Oral drug absorption enhancement by chitosan and its derivatives

Chitosan is a non-toxic, biocompatible polymer that has found a number of applications in drug delivery including that of absorption enhancer of hydrophilic macromolecular drugs. Chitosan, when protonated (pH<6.5), is able to increase the paracellular permeability of peptide drugs across mucosal epithelia. Chitosan derivatives have been evaluated to overcome chitosan's limited solubility and effectiveness as absorption enhancer at neutral pH values such as those found in the intestinal tract. Trimethyl chitosan chloride (TMC) has been synthesized at different degrees of quaternization. This quaternized polymer forms complexes with anionic macromolecules and gels or solutions with cationic or neutral compounds in aqueous environments and neutral pH values. TMC has been shown to considerably increase the permeation and/or absorption of neutral and cationic peptide analogs across intestinal epithelia. The mechanism by which TMC enhances intestinal permeability is similar to that of protonated chitosan. It reversibly interacts with components of the tight junctions, leading to widening of the paracellular routes. Mono-carboxymethylated chitosan (MCC) is a polyampholytic polymer, able to form visco-elastic gels in aqueous environments or with anionic macromolecules at neutral pH values. MCC appears to be less potent compared to the quaternized derivative. Nevertheless, MCC was found to increase the permeation and absorption of low molecular weight heparin (LMWH; an anionic polysaccharide) across intestinal epithelia. Neither chitosan derivative provokes damage of the cell membrane, and therefore they do not alter the viability of intestinal epithelial cells.

Chitosan and its derivatives as intestinal absorption enhancers

Chitosan is a non-toxic, biocompatible polymer that has found a number of applications in drug delivery including that of absorption enhancer of hydrophilic macromolecular drugs. Chitosan, when protonated (pH<6.5), is able to increase the paracellular permeability of peptide drugs across mucosal epithelia. Chitosan derivatives have been evaluated to overcome chitosan's limited solubility and effectiveness as absorption enhancer at neutral pH values such as those found in the intestinal tract. Trimethyl chitosan chloride (TMC) has been synthesized at different degrees of quaternization. This quaternized polymer forms complexes with anionic macromolecules and gels or solutions with cationic or neutral compounds in aqueous environments and neutral pH values. TMC has been shown to considerably increase the permeation of neutral and cationic peptide analogs across Caco-2 intestinal epithelia. The mechanism by which TMC is enhancing the intestinal permeability is similar to that of protonated chitosan. It reversibly interacts with components of the tight junctions, leading to widening of the paracellular routes. This chitosan derivative does not provoke damage of the cell membrane, and does not alter the viability of intestinal epithelial cells. Co-administrations of TMC with peptide drugs were found to substantially increase the bioavailability of the peptide in both rats and juvenile pigs compared with administrations without the polymer.

Effect of poly-L-arginine on the nasal absorption of FITC-dextran of different molecular weights and recombinant human granulocyte colony-stimulating factor (rhG-CSF) in rats

The effect of poly-L-arginine (poly-L-Arg) on the in vivo nasal absorption of FITC-dextrans with a mean molecular weight ranging from 4.3 to 167 kDa and recombinant human granulocyte colony-stimulating factor (rhG-CSF) in rats were studied. When FITC-dextrans were co-administered intranasally with 1.0 w/v% poly-L-Args of different molecular weight (MW, ca. 45.5 and 92 kDa, poly-L-Arg (50) and poly-L-Arg (100)), the bioavailability (F(infinity)) increased markedly compared with that after administration of FITC-dextran alone. However, the F(infinity) decreased exponentially with the increasing molecular weight of FITC-dextrans. There was no significant difference between the enhanced nasal absorption of FITC-dextrans achieved by the co-administration of poly-L-Arg (50) and poly-L-Arg (100). Moreover, the relationship between the F(infinity) and the molecular weight of FITC-dextrans indicated that the molecular weight of protein drugs, which exhibited efficient absorption with poly-L-Arg, was about 20 kDa, when the lower limit of bioavailability for developing a potent transnasal delivery system was assumed to be about 10%. Indeed, the nasal absorption of rhG-CSF, which has a molecular weight of 18.8 kDa, was also increased after co-administration of 1.0 w/v% poly-L-Arg (50) and the F(infinity) was about 11%. It seems likely that poly-L-Arg can be used to provide adequate nasal absorption of various protein drugs which have a molecular weight of about 20 kDa, thereby allowing the successful development of a variety of transnasal drug delivery systems.

In vitro gene delivery mediated by chitosan. effect of pH, serum, and molecular mass of chitosan on the transfection efficiency

Aminopolysaccharides such as chitosan and polygalactosamine (pGalN) were used to transfer luciferase plasmid into tumor cells. Chitosan largely enhanced the transfection efficiency of luciferase plasmid (pGL3), while pGalN did not at all. Transfection efficiencies of the pGL3/chitosan complexes were dependent on pH of culture medium, stoicheometry of pGL3:chitosan, serum, and molecular mass of chitosan. Transfection efficiency at pH 6.9 was higher than that at pH7.6. Optimum charge ratio of the pGL3:chitosan was 1:5. Chitosan polymer of 15 and 52 kDa largely promoted luciferase activities. Transfection efficiency mediated by chitosan of > 100 kDa was less than that by chitosan of 15 and 52 kDa. Heptamer (1.3 kDa) did not show any gene expression. Cationic liposome (lipofectin)-associated gene expression was inhibited by serum, while chitosan showed resistance to serum.

Development of novel formulations that enhance adenoviral-mediated gene expression in the lung in vitro and in vivo

Despite remarkable progress in the development of both viral and non-viral gene delivery vectors for cystic fibrosis therapy, low efficiency of gene transfer to the airway epithelium is a major obstacle to clinical application. Here we develop formulations that enhance cellular absorption of adenoviral vectors. We selected excipients from a panel of pharmaceutically acceptable com-pounds known to enhance drug absorption. Transduction efficiency of the virus in the presence of each ingredient was assessed in vitro and in vivo. Mannitol and chitosan substantially enhanced transduction efficiency in vitro and augmented expression in vivo by 4 and 8 log units, respectively. The most successful formulation (a blend of sucrose, mannitol, and Pluronic F68) transduced 100% of an A549 cell population in vitro and produced areas of intense gene expression in both large and small airways in vivo with minimal toxicity. Dose response studies also indicate that when placed in this formulation, the viral dose can be lowered by 1/2 log while maintaining superior levels of transgene expression. This formulation also enhanced the physical stability of the virus. No significant loss in titer was detected from a lyophilized formulation after storage at 25 degrees C for 30 days.

Improved nasal absorption of drugs using poly-L-arginine: effects of concentration and molecular weight of poly-L-arginine on the nasal absorption of fluorescein isothiocyanate-dextran in rats

The effects of the concentration and molecular weight of poly-L-arginine (poly-L-Arg) on the in vivo nasal absorption of fluorescein isothiocyanate-labeled dextran (MW, 4 kDa, FD-4) in rats were studied. When poly-L-Arg with a range of different molecular weights (MW, 8.9, 45.5 and 92.0 kDa) was applied intranasally at various concentrations, the bioavailability (F(0-9 h)) of FD-4 increased with the increasing concentration of poly-L-Arg. The enhanced absorption was also dependent on the molar concentration, in that the poly-L-Arg with a higher molecular weight increased F(0-9 h) at a lower molar concentration. In addition, for each applied concentration, the poly-L-Arg exhibited a molecular weight-dependence as far as the enhancement of FD-4 absorption was concerned. On the other hand, the maximum absorption rate (MAR) of FD-4, calculated by means of a deconvolution method, tended to reach a maximum plateau level at a lower applied concentration for the poly-L-Arg with the highest molecular weight, but this plateau level was almost the same for poly-L-Arg with molecular weights of 45.5 and 92.0 kDa. Moreover, the simulated absorption profiles of FD-4 indicate that the degree of enhancement (the level of MAR and the subsequent reduction in the absorption rate) was dependent on the molecular weight of poly-L-Arg, while the effect of poly-L-Arg was maintained for a longer period, depending on the applied concentration, although the MAR was relatively similar. These results indicate that the molecular weight of poly-L-Arg appears to affect both the enhancing efficiency (absorption rate) and the time-frame of this enhancing effect, whereas the concentrations of each poly-L-Arg system applied only have an effect on the time-frame. These effects may also be associated with the charge density of a poly-L-Arg molecule.

Carbohydrate biopolymers enhance antibody responses to mucosally delivered vaccine antigens

We have evaluated the ability of two carbohydrate biopolymers, chitosan and gellan, to enhance antibody responses to subunit influenza virus vaccines delivered to the respiratory tracts of mice. Groups of mice were vaccinated three times intranasally (i.n.) with 10 microg of purified influenza B/Panama virus surface antigens (PSAs), which consist of hemagglutinin (HA) and neuraminidase (NA), either alone or admixed with chitosan or gellan solutions. Separate groups were vaccinated subcutaneously (s.c.) with PSAs adsorbed to Alhydrogel or chitosan or gellan alone i.n. Serum antibody responses were determined by enzyme-linked immunosorbent assay (ELISA) for influenza virus-specific immunoglobulin G (IgG) and by HA inhibition (HAI) and NA inhibition (NAI) assays. The local respiratory immune response was measured by assaying for influenza virus-specific IgA antibody in nasal secretions and by enumerating nasal and pulmonary lymphocytes secreting IgA, IgG, and IgM anti-influenza virus-specific antibodies by enzyme-linked immunospotting (ELISPOT). When administered alone i.n., B/Panama PSA was poorly immunogenic. Parenteral immunization with B/Panama PSA with Alhydrogel elicited high titers of anti-B/Panama antibodies in serum but a very poor respiratory anti-B/Panama IgA response. In contrast, i.n. immunization with PSA plus chitosan stimulated very strong local and systemic anti-B/Panama responses. Gellan also enhanced the local and serum antibody responses to i.n. PSA but not to the same extent as chitosan. The ability of chitosan to augment the immunogenicity of influenza vaccines given i.n. was confirmed using PSA prepared from an influenza A virus (A/Texas H1N1).

Chitosans as nasal absorption enhancers of peptides: comparison between free amine chitosans and soluble salts

A total of three free amine chitosans (CS J, CS L and CS H) and two soluble chitosan salts (CS G and CS HCl) were evaluated for their efficacy and safety as nasal absorption enhancers of peptides based on in situ nasal perfusion and subacute histological evaluation in rat. At 0.5% w/v, all chitosans were effective in enhancing the nasal absorption of [D-Arg(2)]-Kyotorphin, an enzymatically stable opioid dipeptide. The enhancing effect of the free amine chitosans increased as the pH was decreased from 6.0 to 4.0 (P<0.05). However, the pH effect was not significant for the two chitosan salts (P0.05), suggesting that their adjuvant activity may be less pH-dependent than the free amine form. CS J and CS G were subsequently selected for further studies. At only 0.02% w/v, their enhancing effect was already significant and comparable to that of 5% w/v hydroxypropyl-beta-cyclodextrin (HP-beta-CD). Both chitosans at 0.1% caused minimal release of total protein and phosphorus from the rat nasal mucosa, with the values similar to that of 5% HP-beta-CD. At 0. 5% the two chitosans also stimulated smaller release of lactate dehydrogenase, an intracellular enzyme used as marker of nasal membrane damage, than 1.25% dimethyl-beta-cyclodextrin. Morphological evaluation of the rat nasal mucosa following 2-week daily administration indicated that the two chitosans (1.0%) produced only mild to moderate irritation. In conclusion, both the free amine and the acid salt forms of chitosans are effective in enhancing the nasal absorption of [D-Arg(2)]-Kyotorphin and have potential for further studies as a safe and effective nasal absorption enhancer of peptide drugs.

Effect of degree of quaternization of N-trimethyl chitosan chloride for enhanced transport of hydrophilic compounds across intestinal caco-2 cell monolayers

N-Trimethyl chitosan chloride (TMC) is a permanently quaternized chitosan derivative with improved aqueous solubility compared to native chitosan. TMC is able to open the tight junctions of intestinal epithelia at physiological pH values, where chitosan is insoluble and therefore ineffective. TMCs with degrees of substitution of 40 and 60% were synthesized according to a novel synthesis procedure and their effect on the permeability of the tight junctions of the intestinal Caco-2 monolayers was studied, measuring the transepithelial electrical resistance and the transport of a mainly paracellularly transported compound, [14C]-mannitol. Toxicity studies using nucleic stains were done to establish the transport as a cause of opening of the tight junctions and not of possible cytotoxicity. TMC60 showed higher transport enhancement ratios than TMC40 in all concentrations tested (0.05-1. 0%, w/v). Both derivatives did not affect the viability of the Caco-2 cell monolayers. These results suggest that high charge density is necessary for TMC to substantially improve the paracellular permeability of intestinal epithelia. It is expected that TMC40 and TMC60 will enhance the intestinal permeation of hydrophilic macromolecular drugs such as peptides and proteins.

Chitosan microspheres with hydrocortisone and hydrocortisone-hydroxypropyl-beta-cyclodextrin inclusion complex

In the present study, an inclusion complex composed of hydrocortisone acetate (HC) and hydroxypropyl-beta-cyclodextrin (HPbetaCD) was prepared by the spray-drying method. HC alone, HC inclusion complex or HC with HPbetaCD as a physical mixture were incorporated into chitosan microspheres by spray-drying. The inclusion complex and microspheres were characterized by X-ray powder diffractometry and differential scanning calorimetry (DSC). Microspheres were studied with respect to particle size distribution, drug content and in vitro drug release. The results indicate that the HCHPbetaCD inclusion complex is more water soluble than HC alone. The HC release rates from chitosan microspheres were influenced by the drug/polymer ratio in the manner that an increase in the release rate was observed when the drug loading was decreased. However, release data from all samples showed significant improvement of the dissolution rate for HC, with 25-40% of the drug being released in the first hour compared with about 5% for pure HC. The complexation method and microsphere preparation method (spray-drying) is simple with great potential for industrial production.

Biopharmaceutics of transmucosal peptide and protein drug administration: role of transport mechanisms with a focus on the involvement of PepT1

Non-invasive delivery of peptide and protein drugs will soon become a reality. This is due partly to a better understanding of the endogenous transport mechanisms, including paracellular transport, endocytosis, and carrier-mediated transport of mucosal routes of peptide and protein drug administration. This paper focuses on work related to the elucidation of structure-function, intracellular trafficking, and regulation of the intestinal dipeptide transporter, PepT1.

Screening of cationic compounds as an absorption enhancer for nasal drug delivery

Several cationic compounds were screened as potential nasal absorption enhancers to increase intranasal absorption of a model drug, fluorescein isothiocyanate labeled dextran (MW 4.4 kDa, FD-4), without nasal membrane damage in rats. Their effects were compared with those of classical enhancers. Various cationic compounds (poly-L-arginines with different molecular weights (MW 8.9, 45.5 and 92.0 kDa, poly-L-Arg (10), (50) and (100), respectively), L-arginine (L-Arg), L-lysine (L-Lys), and cetylpyridinium chloride (CPCL) were evaluated. Of the cationic compounds, poly-L-Arg and CPCL greatly enhanced the intranasal absorption of FD-4, as did chitosan, a cationic polysaccharide which has been reported to show a great effect on the transnasal delivery of peptide and protein drugs. The enhancing intensity by poly-L-Arg was dependent on its molecular weight. Rank order of the enhancing ratio, calculated from the AUC ratio for the enhancer treatment against the untreatment, was 0.5% poly-L-Arg (100) congruent with0.5% sodium dodecylsulfate congruent with0.5% CPCL?0.5% poly-L-Arg (50)?0.5% sodium deoxycholate congruent with0.5% sodium taurodihydrofusidate?0.5% polyoxyethylene-9-lauryl ether congruent with0.5% lysophosphatidylcholine?0.5% chitosan congruent with0.5% poly-L-Arg (10)>/=10% L-Arg congruent with10% L-Lys?0.5% sodium glycocholate congruent with0.5% sodium taurocholate congruent with0.5% EDTA. Only the poly-L-Args represented almost the same degree of hemolysis of cationic compounds compared with pH 7.0 phosphate buffered saline in the rat erythrocyte lysis experiment. The enhancing ratio by classical enhancers correlated with leaching of protein, phospholipids and LDH from isolated rabbit nasal mucosa. CPCL also fell on the regression lines between the enhancing ratio and their degree of leaching from classical enhancers. In contrast, the enhancing intensities by poly-L-Arg (10), (50) and (100) were greatly shifted from the regression line: the amount of leaching was markedly low in spite of a great enhancement of FD-4 absorption. These findings suggest that of the assessed enhancers only the poly-L-Args enhance the transnasal delivery of high molecular substances without severe damage to the nasal mucosal membrane. Poly-L-Arg is therefore a promising candidate having a good balance between enhancing activity and safety for nasal peptide and protein delivery.

Effects of N-trimethyl chitosan chloride, a novel absorption enhancer, on caco-2 intestinal epithelia and the ciliary beat frequency of chicken embryo trachea

N-trimethyl chitosan (TMC) polymers are quaternized chitosans in different degrees of trimethylation. These polymers enhance the absorption of macromolecules through mucosal epithelia by triggering the reversible opening of tight junctions and only allow for paracellular transport. To investigate the safety of these novel absorption enhancers cytotoxicity and ciliotoxicity studies have been performed. Intestinal Caco-2 cell monolayers were chosen to study possible membrane damaging effects of these polymers, using confocal laser scanning microscopy visualization of nuclear staining by a membrane impermeable fluorescent probe during transport of the paracellular marker Texas red dextran (MW 10 000). Ciliated chicken embryo trachea tissue was used to study the effect of the polymers on the ciliary beat frequency (CBF) in vitro. In both studies the TMC polymers of different degrees of substitution (20, 40 and 60%) were tested at a concentration of 1.0% (w/v). No substantial cell membrane damage could be detected on the Caco-2 cells treated with TMCs, while the effect on the CBF in vitro was found to be marginal. TMC60 and TMC40 enhance paracellular transport of Texas red dextran in Caco-2 cell monolayers, whereas TMC20 is ineffective. In conclusion, TMCs of high degrees of substitution may be effective and safe absorption enhancers for peptide and protein drug delivery.

Intranasal insulin delivery and therapy

Intranasal insulin delivery has been widely investigated as an alternative to subcutaneous injection for the treatment of diabetes. The pharmacokinetic profile of intranasal insulin is similar to that obtained by intravenous injection and, in contrast to subcutaneous insulin delivery, bears close resemblance to the 'pulsatile' pattern of endogenous insulin secretion during meal-times. The literature suggests that intranasal insulin therapy has considerable potential for controlling post-prandial hyperglycaemia in the treatment of both IDDM and NIDDM. However, effective insulin absorption via the nasal route is unlikely without employing the help of absorption enhancers or promoters which are able to modulate nasal epithelial permeability to insulin and/or prolong the residence time of the drug formulation in the nasal cavity. This article discusses the structure and function of the nasal cavity, the barriers which prevent nasal insulin absorption and through the use of absorption enhancers or promoters methods by which these barriers may be overcome.

Chitosan and depolymerized chitosan oligomers as condensing carriers for in vivo plasmid delivery

Chitosan is a polysaccharide that demonstrates much potential as a gene delivery system. The ability of a commercially available chitosan and depolymerized chitosan oligomers to condense plasmid was determined using TEM and microtitration calorimetry, while the diameter and stability of the resultant complexes were measured using laser light scattering. Selected complexes were physically stable to challenge with both serum and salt solutions. Parameters such as chitosan molecular weight, plasmid concentration and charge ratio influenced such stability. The effect of including a pH-sensitive endosomolytic peptide on the physicochemical properties of the complex was determined. The presence of a pH-sensitive endosomolytic peptide enhanced the levels of reporter gene expression in Cos-1 cells 4-fold. A selected complex containing a lytic peptide was administered in the upper small intestine and colon of rabbits, and reporter gene expression was measured in defined intestinal tissues. Reporter gene expression was enhanced in defined intestinal tissues, although levels of expression remained low. The combination of strong complex stability and low in vivo expression levels suggest that uptake and/or decomplexation, but not endosomal release, may be the critical rate-limiting steps in the uptake process.

Stimulation of mucosal and systemic antibody responses against Bordetella pertussis filamentous haemagglutinin and recombinant pertussis toxin after nasal administration with chitosan in mice

Mice were intranasally immunised with a mixture of Bordetella pertussis filamentous haemagglutinin (FHA) and recombinant pertussis toxin, PT-9K/129G (rPT) in combination with chitosan. For both antigens, this formulation induced systemic responses as measured by serum IgG and also mucosal responses as measured by secretory IgA in lung lavage and nasal washes. Immunosorbant assays were used to measure these responses. Both the systemic and mucosal responses were considerably higher than those produced when a mixture of rPT and FHA was administered nasally without chitosan. In comparison, intraperitoneally administered rPT/FHA adsorbed to Alhydrogel elicited only a systemic response, and nasal chitosan solution produced neither systemic nor mucosal response. This study clearly demonstrated that chitosan potentiated the serum and mucosal immune responses to nasally administered FHA and rPT in mice. Hence, this nasal chitosan delivery system has potential as a new non-injectable vaccine for the prophylaxis of whooping cough.

Polymeric chitosan-based vesicles for drug delivery

A simple carbohydrate polymer glycol chitosan (degree of polymerization 800 approx.) has been investigated for its ability to form polymeric vesicle drug carriers. The attachment of hydrophobic groups to glycol chitosan should yield an amphiphilic polymer capable of self-assembly into vesicles. Chitosan is used because the membrane-penetration enhancement of chitosan polymers offers the possibility of fabricating a drug delivery system suitable for the oral and intranasal administration of gut-labile molecules. Glycol chitosan modified by attachment of a strategic number of fatty acid pendant groups (11-16 mol%) assembles into unilamellar polymeric vesicles in the presence of cholesterol. These polymeric vesicles are found to be biocompatible and haemocompatible and capable of entrapping water-soluble drugs. By use of an ammonium sulphate gradient bleomycin (MW 1400), for example, can be efficiently loaded on to these polymeric vesicles to yield a bleomycin-to-polymer ratio of 0.5 units mg(-1). Previously polymers were thought to assemble into vesicles only if the polymer backbone was separated from the membrane-forming amphiphile by a hydrophilic side-arm spacer. The hydrophilic spacer was thought to be necessary to decouple the random motion of the polymer backbone from the ordered amphiphiles that make up the vesicle membrane. However, stable polymeric vesicles for use in drug delivery have been prepared from a modified carbohydrate polymer, palmitoyl glycol chitosan, without this specific architecture. These polymeric vesicles efficiently entrap water-soluble drugs.

Microparticle resins as a potential nasal drug delivery system for insulin

The application of various resins for the nasal delivery of insulin was examined in rabbits. Intranasal administration of human insulin (28 U, 1 mg) mixed with fractionated sodium polystyrene sulfonate powder (an anionic resin with a particle size of 20-45 microns) caused a rapid increase of the plasma insulin level 413.0 +/- 71.7 microU/ml (mean +/- S.D.) after 15 min, while intranasal administration of insulin alone caused little increase. The blood glucose level decreased from 118.8 +/- 18.5 mg/dl to 65.8 +/- 13.8 mg/dl at 45 min after administration. These results were superior to those obtained with the unfractionated resin. Styrene-divinylbenzene copolymer (a nonionic resin; 20-45 microns fraction) showed similar enhancement of nasal insulin absorption. In contrast, polyacrylester (a nonionic resin; 20-45 microns fraction) and cholestyramine (a cationic resin) did not promote insulin absorption. These results suggest that some resins may be useful for nasal delivery of insulin.

Nasal mucociliary clearance as a factor in nasal drug delivery

The nasal mucociliary clearance system transports the mucus layer that covers the nasal epithelium towards the nasopharynx by ciliary beating. Its function is to protect the respiratory system from damage by inhaled substances. Impairment of nasal mucociliary clearance can result in diseases of the upper airways. Therefore, it is important to study the effects of drugs and drug excipients on nasal mucociliary clearance. A large number of methods are used to assess mucociliary clearance. These methods study the effects of drug and excipients on the mucociliary system in vitro or in vivo in animals and humans. In some cases, the results of different in vitro and in vivo measurements do not correlate well. In vitro methods, especially ciliary beat frequency measurements, have been demonstrated to be valuable tools for toxicity screening. However, in vivo studies are essential to confirm the safety of nasal drug formulations. Nasal mucociliary clearance also has implications for nasal drug absorption. Drugs are cleared rapidly from the nasal cavity after intranasal administration, resulting in fast systemic drug absorption. Several approaches are discussed to increase the residence time of drug formulations in the nasal cavity, resulting in improved nasal drug absorption. However, more experimental evidence is needed to support the conclusion that this improved absorption is caused by a longer residence time of the nasal drug formulation.

Chitosan as a nasal delivery system: the effect of chitosan solutions on in vitro and in vivo mucociliary transport rates in human turbinates and volunteers

In these studies, we examined the effect on mucociliary transport rates (MTR) of various 0.25% (w/v) chitosan solutions applied to human nasal tissue both ex vivo and in vivo. In the first study a range of chitosans with different molecular weights were applied to freshly amputated human nasal turbinates, and their effect on MTR was recorded. The transient inhibitory effect on turbinate MTR that was found for most of the chitosan preparations showed a marked dependence on the volume of chitosan solution applied and the molecular weight of the chitosan tested. The higher the molecular weight of the chitosan and the more chitosan applied, the longer the original MTR was depressed. A small scale human trial, investigating the effect of chitosan glutamate, on saccharin clearance times, was also undertaken. The study showed that a once daily application of a 0.25% solution of the chitosan for 7 days had no effect on either saccharin clearance times or nasal histology as examined by light microscopy.