N-Trimethyl chitosan chloride as absorption enhancer in oral peptide drug delivery. Development and characterization of minitablet and granule formulations

Formulation strategies to improve the efficacy of intestinal permeation enhancers. Adv Drug Deliv Rev 2021;177:113925. [PMID: 34418495 DOI: 10.1016/j.addr.2021.113925]

The use of chemical permeation enhancers (PEs) is the most widely tested approach to improve oral absorption of low permeability active agents, as represented by peptides. Several hundred PEs increase intestinal permeability in preclinical bioassays, yet few have progressed to clinical testing and, of those, only incremental increases in oral bioavailability (BA) have been observed. Still, average BA values of ~1% were sufficient for two recent FDA approvals of semaglutide and octreotide oral formulations. PEs are typically screened in static in vitro and ex-vivo models where co-presentation of active agent and PE in high concentrations allows the PE to alter barrier integrity with sufficient contact time to promote flux across the intestinal epithelium. The capacity to maintain high concentrations of co-presented agents at the epithelium is not reached by standard oral dosage forms in the upper GI tract in vivo due to dilution, interference from luminal components, fast intestinal transit, and possible absorption of the PE per se. The PE-based formulations that have been assessed in clinical trials in either immediate-release or enteric-coated solid dosage forms produce low and variable oral BA due to these uncontrollable physiological factors. For PEs to appreciably increase intestinal permeability from oral dosage forms in vivo, strategies must facilitate co-presentation of PE and active agent at the epithelium for a sustained period at the required concentrations. Focusing on peptides as examples of a macromolecule class, we review physiological impediments to optimal luminal presentation, discuss the efficacy of current PE-based oral dosage forms, and suggest strategies that might be used to improve them.

Quaternary ammonium N,N,N-trimethyl chitosan derivative and povidone‑iodine complex as a potent antiseptic with enhanced wound healing property

The importance of developing more potent antimicrobials and robust infection prevention practices has been highlighted recently with the increase in reports of emerging bacterial resistance mechanisms and the development of antibiotic-resistant microbes. In this study, a quaternary ammonium chitosan derivative, N,N,N-trimethyl chitosan chloride (TMC) with inherent bactericidal property was synthesized and complexed with povidone‑iodine (PVP-I) to create a potentially more potent antiseptic solution that could also significantly enhance the wound healing process. TMC, a positively charged, water-soluble derivative of chitosan, formed stable solutions with PVP-I at 5% w/v TMC concentration (TMC5/PVP-I). TMC5/PVP-I was significantly effective against multidrug-resistant bacteria S. aureus compared with PVP-I alone. TMC/PVP-I solutions also showed fungicidal property against C. albicans, with no cytotoxic effects when tested against human fibroblast cells cultured in vitro. Wound healing assessment in vivo revealed early collagen formation and re-epithelialization for TMC5/PVP-I treated wounds in rats relative to control and PVP-I only. Formulation of TMC/PVP-I solutions presented in the study can be easily adapted in the existing production of commercial PVP-I creating a new product with more potent bactericidal and enhanced wound healing properties for optimal wound care.

Development and evaluation of a composite dosage form containing desmopressin acetate for buccal administration

Desmopressin acetate (DDAVP) is an oligopeptide indicated for the treatment of primary nocturnal enuresis, for example. The poor oral bioavailability of DDAVP accelerated a shift to alternative routes of administration like nasal and oromucosal, whereby nasal administration results in high fluctuations increasing the risk of undesirable side effects. Aim of the study was to use a new composite dosage form (solid matrix attached to a bilayer mucoadhesive film) to make DDAVP available via oromucosal route, reducing the risk of undesirable side effects through precise dosing. DDAVP was incorporated into a solid matrix in the form of a minitablet, and both direct tableting (AV > 30) and granulation followed by tableting (AV = 17.86) were compared. Minitablets with content uniformity could only be obtained by granulation and loss supplementation (AV = 11.27) with immediate drug release (>80% after 7–8 min) and rapid disintegration (<49 s). Permeation studies were performed with a clinically relevant dose (200 μg) in a time interval of up to one hour, resulting in apparent permeation coefficients of 4.90 × 10⁻⁶ cm/s (minitablet) and 2.04 × 10⁻⁶ cm/s (composite). Comparable fluctuations showed no inferiority of composite and minitablet regarding dosing accuracy. Thus, a step towards controlled and dose-accurate transmucosal delivery of systemically active DDAVP could be achieved.

Scalable Manufacturing of Enteric Encapsulation Systems for Site-Specific Oral Insulin Delivery

Oral drug delivery is a more favored mode of administration because of its ease of administration, high patient compliance, and low healthcare costs. However, no oral protein formulations are commercially available currently due to hostile gastrointestinal (GI) barriers resulting in insignificant oral bioavailability of macromolecular drugs. Herein, we used insulin as a model protein drug; insulin-loaded N-(2-hydroxy)-propyl-3-trimethylammonium chloride modified chitosan (HTCC)/sodium tripolyphosphate (TPP) nanocomplex (NC) as a nanocore was further encapsulated into enteric Eudragit L100-55 material, through a two-step flash nanocomplexation (FNC) process in a reliable and scalable manner, forming our NC-in-Eudragit composite particles (NE). Particle size and surface properties of our optimized NE were tailored to protect the loaded insulin from acidic degradation in the hostile stomach environment and to achieve intestinal site-specific drug release as well as the improvement of oral delivery efficiency of insulin. In addition, the oral administration of the optimized NE to type 1 diabetic rats could induce a very significant hypoglycemic effect with a relative oral bioavailability of 13.3%. Our results demonstrated that enteric encapsulation of nanotherapeutics using a FNC apparatus could cause drug formulations to possess better size controllability, batch-mode reproducibility, and homogeneous surface coating and then significantly enhance their oral bioavailability of insulin, indicating its great potential for clinical translation of oral protein therapeutics.

Curdlan sulfate-O-linked quaternized chitosan nanoparticles: potential adjuvants to improve the immunogenicity of exogenous antigens via intranasal vaccination

Introduction

The development of ideal vaccine adjuvants for intranasal vaccination can provide convenience for many vaccinations. As an ideal intranasal vaccine adjuvant, it should have the properties of assisting soluble antigens to pass the mucosal barrier and potentiating both systemic and mucosal immunity via nasal administration.

Methods

By using the advantages of polysaccharides, which can promote both T-helper 1 and 2 responses, curdlan sulfate (CS)–O-(2-hydroxyl)propyl-3-trimethyl ammonium chitosan chloride (O-HTCC) nanoparticles were prepared by interacting CS with O-HTCC, and the adjuvancy of the nanoparticles was investigated.

Results

The results showed that the polysaccharide-based nanoparticles induced the proliferation and activation of antigen-presenting cells. High protein-loading efficiency was obtained by testing with the model antigen ovalbumin (Ova), and the Ova adsorbed onto the cationic CS/O-HTCC complexes was taken up easily by the epithelium. To evaluate the capacity of the Ova/CS/O-HTCC nanoparticles for immune enhancement in vivo, we collected and analyzed immunocytes, serum, and mucosal lavage fluid from intranasally vaccinated mice. The results showed that Ova/CS/O-HTCC nanoparticles induced activation and maturation of antigen-presenting cells and provoked the proliferation and differentiation of lymphocytes more significantly compared to the immunization of Ova mixed with aluminum hydroxide gel. Furthermore, CS/O-HTCC evoked a significantly higher level of Ova-specific antibodies.

Conclusion

Therefore, these results suggest that CS/O-HTCC nanoparticles are ideal vaccine adjuvants for soluble antigens used in intranasal or mucosal vaccination.

How to design the surface of peptide-loaded nanoparticles for efficient oral bioavailability?

The oral administration of proteins is a current challenge to be faced in the field of therapeutics. There is currently much interest in nanocarriers since they can enhance oral bioavailability. For lack of a clear definition, the key characteristics of nanoparticles have been highlighted. Specific surface area is one of these characteristics and represents a huge source of energy that can be used to control the biological fate of the carrier. The review discusses nanocarrier stability, mucus interaction and absorption through the intestinal epithelium. The protein corona, which has raised interest over the last decade, is also discussed. The universal ideal surface is a myth and over-coated carriers are not a solution either. Besides, common excipients can be useful on several targets. The suitable design should rather take into account the composition, structure and behavior of unmodified nanomaterials.

Intestinal permeation enhancers for oral peptide delivery

Intestinal permeation enhancers (PEs) are one of the most widely tested strategies to improve oral delivery of therapeutic peptides. This article assesses the intestinal permeation enhancement action of over 250 PEs that have been tested in intestinal delivery models. In depth analysis of pre-clinical data is presented for PEs as components of proprietary delivery systems that have progressed to clinical trials. Given the importance of co-presentation of sufficiently high concentrations of PE and peptide at the small intestinal epithelium, there is an emphasis on studies where PEs have been formulated with poorly permeable molecules in solid dosage forms and lipoidal dispersions.

Proteins and peptides: The need to improve them as promising therapeutics for ulcerative colitis

The present review briefly describes the nature, type and pathogenesis of ulcerative colitis, and explores the potential use of peptides and proteins in the treatment of inflammatory bowel disease, especially ulcerative colitis. Intestinal absorption and the barrier mechanism of peptide and protein drugs are also discussed, with special emphasis on various strategies which make these drugs better therapeutics having high specificity, potency and molecular targeting ability. However, the limitation of such therapeutics are oral administration, poor pharmacokinetic profile and decreased bioavailability. The recent findings illustrated in this review will be helpful in designing the peptide/protein drugs as a promising treatment of choice for ulcerative colitis.

Preparation and in vitro evaluation of thienorphine-loaded PLGA nanoparticles

Poly (d,l-lactic-co-glycolide) nanoparticles (PLGA-NPs) have attracted considerable interest as new delivery vehicles for small molecules, with the potential to overcome issue such as poor drug solubility and cell permeability. However, their negative surface charge decreases bioavailability under oral administration. Recently, cationically modified PLGA-NPs has been introduced as novel carriers for oral delivery. In this study, our aim was to introduce and evaluate the physiochemical characteristics and bioadhesion of positively charged chitosan-coated PLGA-NPs (CS-PLGA-NPs), using thienorphine as a model drug. These results indicated that both CS-PLGA-NPs and PLGA-NPs had a narrow size distribution, averaging less than 130 nm. CS-PLGA-NPs was positively charged (+42.1 ± 0.4 mV), exhibiting the cationic nature of chitosan, whereas PLGA-NPs showed a negative surface charge (-2.01 ± 0.3 mV). CS-PLGA-NPs exhibited stronger bioadhesive potency than PLGA-NPs. Furthermore, the transport of thienorphine-CS-PLGA-NPs by Caco-2 cells was higher than thienorphine-PLGA-NPs or thienorphine solution. CS-PLGA-NPs were also found to significantly enhance cellular uptake compared with PLGA-NPs on Caco-2 cells. An evaluation of cytotoxicity showed no increase in toxicity in either kind of nanoparticles during the formulation process. The study proves that CS-PLGA-NPs can be used as a vector in oral drug delivery systems for thienorphine due to its positive surface charge and bioadhesive properties.

Nanomedicines for back of the eye drug delivery, gene delivery, and imaging

Treatment and management of diseases of the posterior segment of the eye such as diabetic retinopathy, retinoblastoma, retinitis pigmentosa, and choroidal neovascularization is a challenging task due to the anatomy and physiology of ocular barriers. For instance, traditional routes of drug delivery for therapeutic treatment are hindered by poor intraocular penetration and/or rapid ocular elimination. One possible approach to improve ocular therapy is to employ nanotechnology. Nanomedicines, products of nanotechnology, having at least one dimension in the nanoscale include nanoparticles, micelles, nanotubes, and dendrimers, with and without targeting ligands. Nanomedicines are making a significant impact in the fields of ocular drug delivery, gene delivery, and imaging, the focus of this review. Key applications of nanotechnology discussed in this review include a) bioadhesive nanomedicines; b) functionalized nanomedicines that enhance target recognition and/or cell entry; c) nanomedicines capable of controlled release of the payload; d) nanomedicines capable of enhancing gene transfection and duration of transfection; f) nanomedicines responsive to stimuli including light, heat, ultrasound, electrical signals, pH, and oxidative stress; g) diversely sized and colored nanoparticles for imaging, and h) nanowires for retinal prostheses. Additionally, nanofabricated delivery systems including implants, films, microparticles, and nanoparticles are described. Although the above nanomedicines may be administered by various routes including topical, intravitreal, intravenous, transscleral, suprachoroidal, and subretinal routes, each nanomedicine should be tailored for the disease, drug, and site of administration. In addition to the nature of materials used in nanomedicine design, depending on the site of nanomedicine administration, clearance and toxicity are expected to differ.

Ceramic nanocarriers: versatile nanosystem for protein and peptide delivery

INTRODUCTION

Proteins and peptides have been established to be the potential drug candidate for various human diseases. But, delivery of these therapeutic protein and peptides is still a challenge due to their several unfavorable properties. Nanotechnology is expanding as a promising tool for the efficient delivery of proteins and peptides. Among numerous nano-based carriers, ceramic nanoparticles have proven themselves as a unique carrier for protein and peptide delivery as they provide a more stable, bioavailable, readily manufacturable, and acceptable proteins and polypeptide formulation.

AREAS COVERED

This article provides an overview of the various aspects of ceramic nanoparticles including their classification, methods of preparation, latest advances, and applications as protein and peptide delivery carriers.

EXPERT OPINION

Ceramic nanocarriers seem to have potential for preserving structural integrity of proteins and peptides, thereby promoting a better therapeutic effect. This approach thus provides pharmaceutical scientists with a new hope for the delivery of proteins and peptides. Still, considerable study on ceramic nanocarrier is necessary with respect to pharmacokinetics, toxicology, and animal studies to confirm their efficiency as well as safety and to establish their clinical usefulness and scale-up to industrial level.

Effects of pharmaceutical processing on pepsin activity during the formulation of solid dosage forms

The main aim of this study was to investigate the effects of pharmaceutical technological methods on pepsin activity during the formulation of solid dosage forms. The circumstances of direct compression and wet granulation were modeled. During direct compression, the heat and the compression force must be taken into consideration. The effects of these parameters were investigated in three materials (pure pepsin, and 1:1 (w/w) pepsin-tartaric acid and 1:1 (w/w) pepsin-citric acid powder mixtures). It was concluded that direct compression is appropriate for the formulation of solid dosage forms containing pepsin through application without acids or with acids at low compression force. The effects of wet granulation were investigated with a factorial design for the same three materials. The factors were time, temperature and moisture content. There was no significant effect of the factors when acids were not applied. Temperature was a significant factor when acids were applied. The negative effect was significantly higher for citric acid than for tartaric acid. It was found that wet granulation can be utilized for the processing of pepsin into solid dosage forms under well-controlled circumstances. The application of citric acid is not recommended during the formulation of solid dosage forms through wet granulation. A mathematically based optimization may be necessary for preformulation studies of the preparation of dosage forms containing sensitive enzymes.

Nasal absorption and local tissue reaction of insulin nanocomplexes of trimethyl chitosan derivatives in rats

OBJECTIVES

The objective of this work was to explore the potential and safety of trimethyl chitosan (TMC) and PEGylated TMC for improved absorption of insulin after nasal administration.

METHODS

The nasal absorption of insulin nanocomplexes of TMC or PEGylated TMC was evaluated in anaesthetized rats. Concomitantly, the histopathological effects of these nanocomplexes on rat nasal mucosa were studied using a perfusion fixation technique.

KEY FINDINGS

All insulin nanocomplexes containing TMC or PEGylated TMC showed a 34-47% reduction in the blood glucose concentration, when the insulin absorption through the rat nasal mucosa was measured indirectly. In addition, the relative pharmacodynamic bioavailability (F(dyn)) of the formulations was found to be dependent upon the charge ratio of insulin and polymer, regardless of polymer structure. The F(dyn) apparently decreased with increasing charge ratio of insulin : polymer. Although acute alterations in nasal morphology by the formulations were affected by the charge ratio of insulin and polymer, the formulation of insulin/PEGylated TMC nanocomplexes was shown to be less toxic to the nasal epithelial membrane than insulin/TMC nanocomplexes.

CONCLUSIONS

PEGylated TMC nanocomplexes were a suitable absorption enhancer for nasal delivery of insulin.

Potential prospects of chitosan derivative trimethyl chitosan chloride (TMC) as a polymeric absorption enhancer: synthesis, characterization and applications

In recent years, researchers have been working extensively on various novel properties of polymers to develop increased efficiency of drug delivery and improve bioavailability of various drug molecules, especially macromolecules. Chitosan, a naturally occurring polysaccharide, because of its protonated/polymeric nature, provides effective and safe absorption of peptide and protein drugs. Its transmucosal absorption is, however, limited to acidic media because of its strong intermolecular hydrogen bonds. A new partially quaternized chitosan derivative, N-trimethyl chitosan chloride (TMC), has been synthesized with improved solubility, safety and effectiveness as an absorption enhancer at neutral pH and in aqueous environment. It enhances the absorption, especially of peptide drugs, by reversible opening of tight junctions in between epithelial cells, thereby facilitating the paracellular diffusion of peptide drugs. This derivative thus opens new perspectives as a biomaterial for various pharmaceutical applications/drug delivery systems. This review deals with the potential use of the quaternized chitosan derivative as a permeation enhancer for the mucosal delivery of macromolecular drugs along with its other biomedical applications.

Chitosan-based delivery systems for protein therapeutics and antigens

Therapeutic peptides/proteins and protein-based antigens are chemically and structurally labile compounds, which are almost exclusively administered by parenteral injections. Recently, non-invasive mucosal routes have attracted interest for administration of these biotherapeutics. Chitosan-based delivery systems enhance the absorption and/or cellular uptake of peptides/proteins across mucosal sites and have immunoadjuvant properties. Chitosan is a mucoadhesive polysaccharide capable of opening the tight junctions between epithelial cells and it has functional groups for chemical modifications, which has resulted in a large variety of chitosan derivatives with tunable properties for the aimed applications. This review provides an overview of chitosan-based polymers for preparation of both therapeutic peptides/protein and antigen formulations. The physicochemical properties of these carrier systems as well as their applications in protein and antigen delivery through parenteral and mucosal (particularly nasal and pulmonary) administrations are summarized and discussed.

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.

Peroral delivery of insulin using chitosan derivatives: A comparative study of polyelectrolyte nanocomplexes and nanoparticles

Polymeric delivery systems based on nanoparticles (NP) have emerged as a promising approach for peroral insulin delivery. Using a trimethyl chitosan (TMC) and a PEG-graft-TMC copolymer, polyelectrolyte complexes (PEC) and nanoparticles were prepared and their properties were compared. The amount of insulin was quantified by HPLC and the stability of PEC and NP upon exposure to simulated gastrointestinal (GI) fluid was monitored by dynamic laser light scattering. It was shown that polymer/insulin (+/-) charge ratio played an important role in PEC and NP formation. Stable, uniform, and spherical PEC/NP with high insulin association efficiency (AE) were formed at or close to optimized polymer/insulin (+/-) charge ratio, depending on polymer structure. All PEC were more stable in pH 6.8 simulated intestinal fluid (SIF) than NP. The PEC also appeared to play some role in protecting insulin from degradation at higher temperature and with proteolytic enzyme more efficiently than NP. On the basis of these results, polyelectrolyte complexation can be suggested as a potentially useful technique for generating insulin delivery systems for peroral administration.

Evaluation and modification of N-trimethyl chitosan chloride nanoparticles as protein carriers

N-Trimethyl chitosan chloride (TMC) nanoparticles were prepared by ionic crosslinking of TMC with tripolyphosphate (TPP). Two model proteins with different pI values, bovine serum albumin (BSA, pI=4.8) and bovine hemoglobin (BHb, pI=6.8), were used to investigate the loading and release features of the TMC nanoparticles. TMC samples with different degrees of quaternization were synthesized to evaluate its influence on the physicochemical properties and release profiles of the nanoparticles. Sodium alginate was used to modify the TMC nanoparticles to reduce burst release. The results indicated that the TMC nanoparticles had a high loading efficiency (95%) for BSA but a low one (30%) for BHb. The particle size and zeta potential were significantly affected by the BSA concentration but not by the BHb concentration. Nanoparticles of TMC with a lower degree of quaternization showed an increase in particle size, a decrease in zeta potential and a slower drug-release profile. As for the alginate-modified nanoparticles, a smaller size and lower zeta potential were observed and the burst release of BSA was reduced. These studies demonstrated that TMC nanoparticles are potential protein carriers, and that their physicochemical properties and release profile could be optimized by means of various modifications.

Synthesis of metallic nanoparticles protected with N,N,N-trimethyl chitosan chloride via a relatively weak affinity

A water-soluble cationic chitosan derivative, N,N,N-trimethyl chitosan chloride (TMC), was synthesized and used as a stabilizing reagent for the synthesis of highly stable Au, Ag and Pt nanoparticles in a single-phase of neutral aqueous solution. The morphology and stability of metallic nanoparticles were evaluated by transmission electron microscopy and UV-vis spectroscopy. The results showed that well-dispersed metallic nanoparticles have a spherical morphology with diameters of about 3 ± 0.5 nm. The prepared gold nanoparticles are stable in the aqueous solution (no significant changes in their morphology and size within 10 months) due to repulsion between the charged polymer shell coatings around the metallic nanoparticles. The relatively low affinity of TMC on gold nanoparticles was confirmed by using a ligand exchange experiment. The mechanism stabilizing the chitosan derivative and the neighbouring gold nanoparticles was identified by FTIR, (1)H NMR and (13)C NMR measurements.

Preparation and in vitro evaluation of mucoadhesive properties of alginate/chitosan microparticles containing prednisolone

This study describes the preparation of mucoadhesive alginate/chitosan microparticles containing prednisolone intended for colon-specific delivery. Two methods have been used for the preparation of the particles: the one-step method is the method in which prednisolone was dispersed within sodium alginate solution and this dispersion was then dropped in a solution containing both calcium chloride and chitosan. The two-step method consisted also of the dispersion of prednisolone in alginate solution and then dropping this dispersion into a solution containing calcium chloride, the particles were then transferred to a chitosan solution. The concentration of sodium alginate solution at 2% (w/v), various concentrations of calcium chloride solution (0.5-1.0%, w/v), chitosan solutions (0.5, 1.0 and 1.5%, w/v) and prednisolone drug load (2, 5, 10 and 15%, w/v) have been used. The results for both preparation methods show that the particle size and drug content were mainly depending on the amount of the drug concentration and not the amount of chitosan and calcium chloride. The in vitro mucoadhesive tests for particles prepared from both methods were carried out using the freshly excised gut of pigs. The particles prepared by the one-step method exhibited excellent mucoadhesive properties after 1h test. Increased chitosan concentrations from 0, 0.5, 1.0 to 1.5% (w/v) resulted in 43, 55, 82 and 88% of the particle remaining attached on the gut surface after 1 h, respectively. However, the particles prepared by the two-step method showed significant less mucoadhesion under the same experimental conditions. At chitosan concentrations of 0, 0.5, 1.0 and 1.5% (w/v) the amount of particles remaining attached to the mucosal surface of the pig gut after 1 h was 43, 3, 11 and 11%, respectively. The prednisolone release at a pH of 6.8 after 4 h was between 63 and 79% for the particles prepared by the one-step method and between 57 and 88% for the particles prepared by the two-step method with a prednisolone drug load of 5 and 10% (w/v), respectively. The results show that depending on the preparation method these chitosan coated alginate particles show different mucoadhesiveness whereas their other properties are not statistically significant different.

Rectal and vaginal administration of insulin-chitosan formulations: an experimental study in rabbits

Insulin is a polypeptide drug and it is degraded by gastrointestinal enzymes, therefore, it cannot be used via oral route readily. There are only parenteral forms available in the market. The aim of this study was to investigate the effect of rectal and vaginal administration of various insulin gel formulations on the blood glucose level as alternative routes in rabbits. Chitosan gel (CH-gel) was used as a carrier; the penetration enhancing effect of sodium taurocholate and dimethyl-beta-cyclodextrin (DM-betaCD) was also investigated. CH-gel provided longer insulin release. The maximum decreasing effect on blood glucose level was observed with insulin-CH-gel containing 5% DM-betaCD. In conclusion, our results indicate that insulin may penetrate well through the rectal and vaginal mucosae from the CH-gel. DM-betaCD was also found to be a useful agent to enhance the penetration of insulin through rectal and vaginal membranes.

Trimethylated chitosan as polymeric absorption enhancer for improved peroral delivery of peptide drugs

The absorption enhancing effects of chitosan and its derivatives have been intensively studied in recent years. It has been shown that these compounds are potent absorption enhancers. Chitosan is only soluble in acidic environments and is therefore incapable of enhancing absorption in the small intestine, the main absorption area in the gastrointestinal tract. Special emphasis has been placed on the absorption enhancing properties of N-trimethyl chitosan chloride (TMC), a partially quaternised derivative of chitosan, due to its solubility in neutral and basic environments. TMC is prepared by the reductive methylation of chitosan. The degree of quaternisation can be altered by increasing the number of reaction steps or by increasing the reaction time. Although the molecular weight of the polymer increases with addition of the methyl groups, a net decrease in the molecular weight is observed due to a decrease in the chain length of the polymer. TMC, like chitosan, possesses mucoadhesive properties. In vitro studies performed on Caco-2 cell monolayers showed a pronounced reduction in the transepithelial electrical resistance (TEER). TMC is also able to increase the permeation of hydrophilic compounds such as [14C]-mannitol and [14C] polyethylene glycol 4000 ([14C] PEG 4000, MW4000) across the cell monolayers. It was also shown that the degree of quaternisation of the polymer plays an important role on its absorption enhancing properties, especially in neutral environments where chitosan is ineffective as an absorption enhancer. The reduction in TEER is an indication of the opening of the tight junctions located between epithelial cells. Opening of the tight junctions will result in enhancement of absorption via the paracellular route. Confocal laser scanning microscopy confirmed transport of large hydrophilic compounds via the paracellular route as well as the mechanism of action of the polymer in which redistribution of the cytoskeletal F-actin is provoked, which leads to the opening of the tight junctions. Various in vivo studies in different animal models confirmed the ability of TMC to increase the absorption of the peptide drugs buserelin and octreotide after intraduodenal or -jejunal administration. However, TMC has always been administered as a solution in these studies. The impracticality of administering a solution, as well as the fact that most peptides are unstable in the presence of water, have led to the need for a solid oral dosage form with which TMC can be administered together with peptide drugs. Recent studies have focused on the development and in vivo evaluation of solid oral dosage forms.