Chitosans as absorption enhancers of poorly absorbable drugs: 3: Influence of mucus on absorption enhancement

Chitosans are potent nontoxic absorption enhancers after nasal administration but their effects on the intestinal epithelium in vivo has not been studied in detail. In this study, the effects of chitosans with varying molecular weights and degrees of acetylation on the absorption of a poorly absorbed model drug (atenolol) were studied in intestinal epithelial cell layers with or without a mucus layer and in an in situ perfusion model of rat ileum. The effects of the chitosans on epithelial morphology and release of lactate dehydrogenase (LDH) into the perfusate were investigated in the in situ model. The chitosans had pronounced effects on the permeability of mucus-free Caco-2 layers and enhanced the permeation of atenolol 10- to 15-fold, with different absorption kinetics for different chitosans, in accordance with previous results. In contrast, enhancement of atenolol absorption through rat ileum was modest. LDH release from the tissues perfused with chitosans did not increase, indicating that the chitosans were used at nontoxic concentrations. Morphological examination of the perfused ileal tissues revealed more mucus discharge from the tissues exposed to chitosans than from controls, which suggested that the discharged mucus may inhibit the binding of chitosan to the epithelial surface and hence decrease the absorption-enhancing effect. This hypothesis was supported by studies with intestinal epithelial HT29-H goblet cells covered with a mucus layer. The binding of chitosan to the epithelial cell surface and subsequent absorption-enhancing effects were significantly reduced in mucus-covered HT29-H cultures. When the mucus layer was removed prior to the addition of chitosan, the cell surface binding and absorption-enhancing effects of the chitosans were increased. We conclude that the modest absorption-enhancing effects of unformulated chitosan solutions in the perfused rat ileum are a result of the mucus barrier in this tissue. This effect may be overcome by increasing the local concentrations of both chitosan and drug, i.e,. through formulation of the chitosan into a particulate dosage form.     

Effect of Glyceryl Monocaprylate–Modified Chitosan on the Intranasal Absorption of Insulin in Rats

Nasal administration of insulin showed the attractive potential to improve the compliance of diabetic patients and alleviate mild cognitive impairment of Alzheimer's patients. However, the nasal absorption of insulin was not ideal, limiting its therapeutic effect in clinic. This study was to explore the potential of glyceryl monocaprylate–modified chitosan (CS-GMC) on the intranasal absorption of insulin via in vivo pharmacodynamic experiment in conscious rats. It was demonstrated that the absorption-enhancing effect of CS-GMC depended on the existing state of insulin in the formulation, substitution degree of GMC on chitosan and concentration of CS-GMC. Better insulin absorption was achieved when insulin existed in molecular form compared with that in polyelectrolyte complexes. CS-GMC with substitution degree 12% (CS-GMC 12%) was a preferred absorption enhancer, and its absorption enhancing effect increased linearly with the increment of its concentration in the range investigated. Compared with chitosan of the same concentration, CS-GMC12% showed remarkably enhanced and prolonged therapeutic effect up to at least 5 h under the concentration of 0.6% (w/v). CS-GMC12% showed almost no ciliotoxicity to the nasal cilia up to concentration 1.0% (w/v). In conclusion, CS-GMC was a promising absorption enhancer to improve the intranasal absorption of insulin.     

环糊精及其衍生物对磷酸川芎嗪鼻黏膜吸收的促进作用

目的研究环糊精及其衍生物对磷酸川芎嗪大鼠鼻黏膜吸收的影响。方法采用大鼠在体鼻循环法研究环糊精的浓度和种类对磷酸川芎嗪鼻黏膜吸收的促进作用,计算磷酸川芎嗪体外吸收速度常数;通过体内法研究大鼠鼻黏膜给药后药物在体内的药物动力学参数,并计算绝对生物利用度。在此基础上就在体法与体内法两种方法的相关性进行考察。结果羟丙基-β-环糊精(hy-droxypropy--βcyclodextrin,HP--βCD)可显著促进磷酸川芎嗪的鼻黏膜吸收。但在质量分数为0.5%~5.0%内,HP--βCD的吸收促进作用无显著差异(P>0.05)。和β-环糊精(-βcyclodextrin,-βCD)相比,HP--βCD的吸收促进作用显著增强。对照组、质量分数为0.5%-βCD和质量分数为0.5%HP--βCD组磷酸川芎嗪鼻黏膜吸收速度常数(ka)分别为0.158、0.163、0.233 mg.min-1,对照组与HP--βCD组有显著性差异(P<0.05),但和-βCD组无显著差异(P>0.05)。对照组与HP--βCD组的药-时曲线均符合二室模型,绝对生物利用度分别为45.7%和66.5%,两组间绝对生物利用度有显著性差异(P<0.05)。结论HP--βCD能显著提高磷酸川芎嗪大鼠鼻黏膜吸收速度和生物利用度。大鼠在体鼻循环法与体内实验结果相关性良好。     

壳聚糖及其衍生物包覆脂质体对胰岛素肠道吸收的影响

目的考察壳聚糖及其衍生物包覆脂质体对胰岛素肠道吸收的影响。方法采用逆相蒸发制备胰岛素脂质体；采用在体肠灌流法研究壳聚糖及其衍生物包覆胰岛素脂质体的肠道吸收；用酶-苯酚法测定血糖值；用放射免疫法测定血清和肠组织中胰岛素含量。结果壳聚糖(CH)、壳聚糖-EDTA轭合物(CEC)包覆胰岛素脂质体和CH-CEC双层包覆胰岛素脂质体的最佳吸收部位均集中在十二指肠，胰岛素溶液的最佳吸收部位在结肠，而未包覆胰岛素脂质体和N-三甲基壳聚糖盐酸盐(TMC)包覆胰岛素脂质体的最佳吸收部位尚不能确定。在各肠段中，以CH-CEC双层包覆胰岛素脂质体的吸收最佳。结论壳聚糖及其衍生物包覆脂质体能促进胰岛素经肠道吸收，并可提高其在肠道中的稳定性。     

Effect of Salt Forms and Molecular Weight of Chitosans on In Vitro Permeability Enhancement in Intestinal Epithelial Cells (Caco-2)

The purpose of this study was to investigate the effect of molecular weight (MW) and salt forms of chitosans (aspartate; CS A, glutamate; CS G, lactate; CS L and hydrochloride, CS HCl) on the transepithelial electrical resistance (TEER) and permeability of Caco-2 cells monolayer, using fluorescein isothiocyanate dextran 4000 (FD-4) as the model compound for paracellular tight junction transport. Chitosan salts were prepared by spray-drying method. FTIR and solid-state ¹³C NMR spectra showed the functional groups of salts in their molecular structures. Salt form, MW of chitosan, and amount of chitosan influenced the permeation-enhancing effects. These studies showed that chitosan salts appeared to increase cell permeability in a dose-dependent manner and caused relatively reversible effects only at the lower doses of 0.001–0.01% w/v. As the MW of chitosan increased from 20 to 460 kDa, the reduction in TEER significantly decreased in the following order: 20 < 45 < 200 < 460 kDa, observed in CS L and CS HCl. In CS A and CS G, the decrease in TEER was not significantly different in all MW because both chitosan salts showed rapid reduction in TEER within 20 min after the start of the experiment. Among chitosan salts, CS A was the most potent absorption enhancer in acidic (pH 6.2) environment. Cytotoxicity of chitosan salts was concentration dependent and varied slightly among the salt forms of chitosan used. CS HCl (MW 45 kDa) was the most toxic having an IC₅₀ of 0.22 ± 0.06 mg/mL. The ranking of chitosan salts cytotoxicity was CS HCl > CS L> CS G > CS A.     

Physicochemical and Immunological Characterization of N,N,N-Trimethyl Chitosan-Coated Whole Inactivated Influenza Virus Vaccine for Intranasal Administration

Purpose  The purpose of this study was the development and physicochemical and immunological characterization of intranasal (i.n.) vaccine formulations of whole inactivated influenza virus (WIV) coated with N,N,N-trimethyl chitosan (TMC). Methods  Synthesized TMCs with a degree of quarternization of 15% (TMC15) or 37% (TMC37) were tested in vitro for their ability to decrease the transepithelial resistance (TEER) of an epithelial cell monolayer. TMC15- and TMC37-coated WIV (TMC15-WIV and TMC37-WIV) were characterized by zeta potential measurements, dynamic light scattering, electron microscopy and gel permeation chromatography. Mice were vaccinated i.n. with selected vaccine formulations and immunogenicity was determined by measuring serum hemagglutination inhibition (HI) and serum IgG, IgG1 and IgG2a/c titers. Also a pulse-chase study with TMCs in solution administered i.n. 2 h prior to WIV was performed. Protective efficacy of vaccination was determined by an aerosol virus challenge. Results  TMC37 induced a reversible decrease in TEER, suggesting the opening of tight junctions, whereas TMC15 did not affect TEER. Simple mixing of (negatively charged) WIV with TMC15 or TMC37 resulted in positively charged particles with TMCs being partially bound. Intranasal immunization with TMC37-WIV or TMC15-WIV induced stronger HI, IgG, IgG1 and IgG2a/c titers than WIV alone. TMC37-WIV induced the highest immune responses. Both TMC15-WIV and TMC37-WIV provided protection against challenge, whereas WIV alone was not protective. Intranasal administration of TMC prior to WIV did not result in significant immune responses, indicating that the immunostimulatory effect of TMC is primarily based on improved i.n. delivery of WIV. Conclusions  Coating of WIV with TMC is a simple procedure to improve the delivery and immunogenicity of i.n. administered WIV and may enable effective i.n. vaccination against influenza.     

Effects of different N-trimethyl chitosans on in vitro/in vivo ofloxacin transcorneal permeation

N-trimethyl chitosan (TMC) polymers differing in quaternization degree (QD) and molecular weight (MW) were prepared from two chitosans 90% deacetylated, one of higher MW (1460 kDa) (TMCH), the other of lower MW (580 kDa) (TMCL), by one (TMCH1, QD = 4%; TMCL1, QD = 3%), two (TMCH2, QD = 35%; TMCL2, QD = 46%), or three (TMCH3, QD = 90%; TMCL3, QD = 78%) reductive methylation steps. The derivatives were tested and compared for their ability to enhance the permeability of ofloxacin across rabbit corneal epithelium, reconstituted in vitro. TMC polymers of intermediate QD (TMCH2 and TMCL2), at the concentration of 0.001% w/v, produced significant permeability enhancements, independent of polymer MW. The enhancing effect did not increase when QD was increased (TMCH3 and TMCL3), while it was not significant with low QD values (TMCH1 and TMCL1). Such an effect was specific of chitosan derivatives, because fully quaternized DEAE-dextran (MeDD) was ineffective. The transcorneal permeability-enhancing property of TMCH2 and TMCL2, and the inefficacy of MeDD were confirmed by in vivo tests on rabbit eyes. However, unlike the in vitro experiments, the in vivo ones showed a stronger effect of the TMC having higher MW. TMCH2 produced antibiotic levels in the aqueous humor higher than the MIC(90%) for the more resistant ocular pathogens. These results point to this derivative as a potential ofloxacin absorption enhancer for the topical treatment of endophthalmitis.     

Characterization of chitosan and its derivatives using asymmetrical flow field-flow-fractionation: a comparison with traditional methods

Chitosan and its derivatives are an important group of polymers used extensively in pharmaceutics. Thus, their physicochemical properties are of considerable interest and need to be characterized carefully. The most important feature to determine is their molecular weight and molecular weight distribution while the molecular weight of polymers plays an important role as pharmaceutical excipients. In this study, the feasibility of using asymmetrical flow field-flow-fractionation (AF4) connected online to a multi-angle light scattering (MALS) detector to measure the molecular weight of chitosans, trimethyl chitosans were studied and compared with the results from some traditional measurement methods. It was found that the influence of trimethyl chitosan synthesis process on the resulting molecular weight decrease depends on the initial molecular weight of chitosan. Significant molecular weight decrease was observed when chitosan molecular weight was larger than 100 kDa. In contrast, the influence was marginal when the molecular weight of chitosan was less than 50 kDa. The AF4-MALS was found to be a suitable method for the characterization of pure chitosans and trimethyl chitosans.     

Intestinal Absorption of Octreotide Using Trimethyl Chitosan Chloride: Studies in Pigs

Purpose. To investigate the enhancing effect of trimethyl chitosan chloride (TMC) on the enteral absorption of octreotide and to delineate the required doses of both TMC and peptide in vivo in juvenile pigs. Methods. Six female pigs (body weight, 25 kg) were operated to induce a stoma at the beginning of their jejunum and to insert an in-dwelling fistula for intrajejunal (IJ) administration of the formulations. A silicone cannula was inserted at the jugular vein for blood sampling. One week after surgery the pigs received IJ octreotide solution administrations with or without TMC at pH 7.4 or chitosan HCl at pH 5.5. For determining bioavailability (F) values, the pigs also received an octreotide solution intravenously (IV). Blood samples were taken from the cannulated jugular vein and subsequently analyzed by radioimmunoassay. Results. Intrajejunal administration of 10 mg octreotide without any polymer (control solution) resulted in F values of 1.7 ± 1.1% (mean ± SE). Chitosan HCl 1.5% (w/v) at pH 5.5 led to a 3-fold increase in F compared to the control (non-polymer containing) formulations. Co-administration of octreotide with 5 and 10% (w/v) TMC at pH 7.4 resulted in 7.7- and 14.5-fold increase of octreotide absorption, respectively (F of 13.9 ± 1.3% and 24.8 ± 1.8%). IJ administration of 5 mg octreotide solutions resulted in low F values of 0.5 ± 0.6%, whereas co-administration with 5% (w/v) TMC increased the intestinal octreotide bioavailability to 8.2 ± 1.5%. Conclusions. Cationic polymers of the chitosan type are able to enhance the intestinal absorption of the peptide drug octreotide in pigs. In this respect, TMC at neutral pH values of 7.4 appears to be more potent than chitosan HCl at a weak acidic pH of 5.5.     

Buccal penetration enhancement properties of N-trimethyl chitosan: Influence of quaternization degree on absorption of a high molecular weight molecule

The aim was to evaluate the influence of the degree of quaternization of N-trimethyl chitosans (TMCs) on the mucoadhesive and penetration enhancement properties towards buccal mucosa. Fluorescein isothiocyanate dextran (MW 4400 Da) (FD4) was used as model molecule. TMCs, obtained from chitosans of different MW (1460 and 580 kDa, respectively), were hydrated in distilled water and in pH 6.4 phosphate buffer (simulating the buccal fluid). The polymer solutions were subjected to mucoadhesion measurements towards bovine submaxillary mucin dispersion and porcine buccal mucosa and to FD4 permeation tests through porcine cheek epithelium. The trimethylation of chitosan allows maintenance or improvement of the mucoadhesive properties of the starting chitosans dependently on quaternization degree. In particular, the mucoadhesive properties increase on increasing degree of quaternization. The trimethylation does not produce any change in chitosan penetration enhancement properties when the medium is distilled water while if pH 6.4 buffer is used, the trimethylation produces an improvement in chitosan penetration enhancing effect. TMC derived from the lower MW chitosan and characterized by the highest degree of quaternization shows the best mucoadhesive and penetration enhancement properties and is the most promising TMC to improve the bioavailability of hydrophilic and large MW molecules (like peptides and proteins) when administered via buccal route.     

Intranasal toxicity of selected absorption enhancers

The intranasal toxicity of selected absorption enhancers (LPC, DM beta CD, N-trimethyl chitosan chloride (TMC) and chitosan hydrochloride) were determined in vivo by investigating the acute microscopic toxic potential on the morphology of rat nasal epithelium with transmission electron microscopy (TEM) and in vitro by measurement of the ciliary beat frequency (CBF), of human ciliated nasal epithelium. TEM evaluations showed that LPC (1% w/v) caused severe epithelial damage and pyknosis. No damage to the rat nasal epithelium was caused by the other absorption enhancers. CBF measurements showed that LPC resulted in total loss of ciliated cells while DM beta CD, TMC and chitosan hydrochloride did not cause any major changes in CBF.     

Chitosans for enhanced delivery of therapeutic peptides across intestinal epithelia: in vitro evaluation in Caco-2 cell monolayers

The aim of the study was to evaluate the transport enhancing effects of two chitosan salts, chitosan hydrochloride and chitosan glutamate (1.5% w/v), and the partially quaternized chitosan derivative, N-trimethyl chitosan chloride (TMC) (1.5 and 2.5% w/v), in vitro in Caco-2 cell monolayers. The transport of the peptide drugs buserelin, 9-desglycinamide, 8-arginine vasopressin (DGAVP) and insulin was followed for 4 h at pH values between 4.40 and 6.20. All the chitosans (1.5%) were able to increase the transport of the peptide drugs significantly in the following order: chitosan hydrochloride>chitosan glutamate>TMC. Due to its quaternary structure, TMC is better soluble than the chitosan salts and further increases in peptide transport were found at higher concentrations (2.5%) of this polymer. The better solubility of TMC may compensate for its lower efficacy at similar concentrations. The increases in peptide drug transport are in agreement with a lowering of the transepithelial electrical resistance (TEER) measured in the cell monolayers. No deleterious effect to the cell monolayers could be detected with the trypan blue exclusion technique. The enzyme inhibitory effect of chitosan hydrochloride (1.5%) was compared with carbomer (1.5%) [Carbopol® 934P] in transport studies with buserelin in the presence of the endoprotease, α-chymotrypsin. In the presence of α-chymotrypsin the transport of buserelin was decreased markedly (from 4.3 to 1.3% of the total dose applied) with chitosan hydrochloride (1.5%), in contrast with carbomer (1.5%) where the transport remained constant (1.4% of the total dose applied). Also the chitosan derivative TMC was not able to inhibit α-chymotrypsin. It is concluded from this study that chitosans are potent absorption enhancers, and that the charge, charge density and the structural futures of chitosan salts and N-trimethyl chitosan chloride are important factors determining their potential use as absorption enhancers for peptide drugs, but that they are unable to prevent degradation from proteolytic enzymes. Structural modification of the chitosan molecule may compensate for this shortcoming.     

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.     

TMC–MCC (N-trimethyl chitosan–mono-N-carboxymethyl chitosan) nanocomplexes for mucosal delivery of vaccines

In this study, for the first time, TMC/MCC complex nanoparticles as a delivery system and as an adjuvant were developed and evaluated to obtain systemic and mucosal immune responses against nasally administered tetanus toxoid (TT). Nanoparticles were developed by complexation between the oppositely charged chitosan derivatives, N-trimethyl chitosan (TMC, polycationic) and mono-N-carboxymethyl chitosan (MCC, polyampholytic) without using any crosslinker for mucosal vaccination. The cellular viability was found to be higher with TMC/MCC complex compared to that of MCC and TMC alone. Size, zeta potential and morphology of the nanoparticles were investigated as a function of preparation method. Nanoparticles with high loading efficacy (95%) and positively charged surface were obtained with an average particle size of 283 ± 2.5 nm. The structural integrity of the TT in the nanoparticles was confirmed by SDS–PAGE electrophoresis analysis. Cellular uptake studies indicated that FITC-BSA loaded nanoparticles were effectively taken up into the mouse Balb/c monocyte macrophages. Mice were nasally immunized with TT loaded TMC/MCC complex nanoparticles and compared to that of TMC and MCC nanoparticles. TMC/MCC complex nanoparticles were shown to induce both the mucosal and systemic immune response indicating that this newly developed system has potential for mucosal administration of vaccines.     

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.     

Intestinal absorption of octreotide: N-trimethyl chitosan chloride (TMC) ameliorates the permeability and absorption properties of the somatostatin analogue in vitro and in vivo

Octreotide acetate is a somatostatin analogue used for the control of endocrine tumors of the gastrointestinal (GI) tract and the treatment of acromegaly. The oral absorption of octreotide is limited because of the limited permeation across the intestinal epithelium. Both chitosan hydrochloride and N-trimethyl chitosan chloride (TMC), a quaternized chitosan derivative, are nonabsorbable and nontoxic polymers that have been proven to effectively increase the permeation of hydrophilic macromolecules across mucosal epithelia by opening the tight junctions. This study investigates the intestinal absorption of octreotide when it is coadministered with the polycationic absorption enhancer TMC. Caco-2 cell monolayers were used as an in vitro intestinal epithelium model, and male Wistar rats were used for in vivo studies. Octreotide with or without polymers (TMC; chitosan hydrochloride) was administered intrajejunally in rats, and serum peptide levels were measured by radioimmunoassay. All applications and administrations were performed at neutral pH values (i.e., pH = 7.4). In vitro transport studies with Caco-2 cells revealed an increased permeation of octreotide in the presence of TMC. Enhancement ratios ranged from 34 to 121 with increasing concentrations of the polymer (0.25-1.5%, w/v). In rats, 1.0% (w/v) TMC solution significantly increased the absorption of the peptide analogue, resulting in a 5-fold increase of octreotide bioavailability compared with the controls (octreotide alone). Coadministration of 1.0% (w/v) chitosan hydrochloride did not enhance octreotide bioavailability. These results in combination with the nontoxic character of TMC suggest that this polymer is a promising excipient in the development of solid dosage forms for the peroral delivery and intestinal absorption of octreotide.     

In Vivo Evaluation of Thiolated Chitosan Tablets for Oral Insulin Delivery

Chitosan–6-mercaptonicotinic acid (chitosan–6-MNA) is a thiolated chitosan with strong mucoadhesive properties and a pH-independent reactivity. This study aimed to evaluate the in vivo potential for the oral delivery of insulin. The comparison of the nonconjugated chitosan and chitosan–6-MNA was performed on several studies such as mucoadhesion, release, and in vivo studies. Thiolated chitosan formulations were both about 80-fold more mucoadhesive compared with unmodified ones. The thiolated chitosan tablets showed a sustained release for 5 h for the polymer of 20 kDa and 8 h for the polymer of 400 kDa. Human insulin was quantified in rats' plasma by means of ELISA specific for human insulin with no cross-reactivity with the endogenous insulin. In vivo results showed thiolation having a tremendous impact on the absorption of insulin. The absolute bioavailabilities were 0.73% for chitosan–6-MNA of 20 kDa and 0.62% for chitosan–6-MNA 400 kDa. The areas under the concentration–time curves (AUC) of chitosan–6-MNA formulations compared with unmodified chitosan were 4.8-fold improved for the polymer of 20 kDa and 21.02-fold improved for the polymer of 400 kDa. The improvement in the AUC with regard to the most promising aliphatic thiomer was up to 6.8-fold. Therefore, chitosan–6-MNA represents a promising excipient for the oral delivery of insulin. © 2014 Wiley Periodicals, Inc. and the American Pharmacists Association J Pharm Sci 103:3165–3170, 2014     

Efficacy and Mechanism of Action of Chitosan Nanocapsules for Oral Peptide Delivery

Purpose We have previously shown that high molecular weight (MW > 100 kDa) chitosan nanocapsules are efficient vehicles for improving the oral absorption of salmon calcitonin (sCT). In the present work, our objectives were, first, to investigate the influence of some formulation parameters on the efficacy of chitosan nanocapsules as carriers for the oral administration of sCT and, second, to elucidate the mechanism of interaction of chitosan nanocapsules with intestinal model cell lines. Methods sCT-loaded chitosan nanocapsules were prepared by the solvent displacement technique. They were characterized for their size, zeta potential, and sCT loading. The ability of chitosan nanocapsules to enhance the oral absorption of sCT was investigated in rats by monitoring the serum calcium levels. Finally, the mechanism of interaction of chitosan nanocapsules with the Caco-2 cell model or in the coculture of Caco-2 with HT29-M6 cells was investigated by confocal fluorescence microscopy. Results Chitosan nanocapsules presented a particle size in nanometer range, a positive surface charge, and an efficient encapsulation of sCT. Following oral administration to rats, all formulations of nanocapsules exhibited the ability to reduce calcemia levels; however, the intensity of the response varied depending on the formulation conditions. With regard to the mechanism of interaction of chitosan nanocapsules with cell culture, the xz images evidenced that chitosan nanocapsules interact and remain associated to the apical side of both model cell cultures. In addition, chitosan nanocapsules showed a preferable association to the mucus-secreting cells (HT29-M6). Conclusions Chitosan nanocapsules are able to enhance and prolong the intestinal absorption of sCT and this effect could be mainly ascribed to their mucoadhesive character and intimate interaction with the intestinal barrier.     

Protective immune responses to meningococcal C conjugate vaccine after intranasal immunization of mice with the LTK63 mutant plus chitosan or trimethyl chitosan chloride as novel delivery platform

Chitosan and its derivative N-trimethyl chitosan chloride (TMC), given as microparticles or powder suspensions, and the non-toxic mucosal adjuvant LTK63, were evaluated for intranasal immunization with the group C meningococcal conjugated vaccine (CRM-MenC). Mice immunized intranasally with CRM-MenC formulated with chitosan or TMC and the LTK63 mutant, showed high titers of serum and mucosal antibodies specific for the MenC polysaccharide. Neither significant differences were observed between microparticle formulations and powder suspensions nor when LTK63 was pre-associated to the delivery system or not. The bactericidal activity measured in serum of mice immunized intranasally with the conjugated vaccine formulated with the delivery systems and the LT mutant was superior to the activity in serum of mice immunized sub-cutaneously. Importantly, intranasal but not parenteral immunization, induced bactericidal antibodies at the nasal level, when formulated with both delivery system and adjuvant.     

依托泊苷壳聚糖胶束的制备及壳聚糖促进依托泊苷肠吸收作用的研究

目的 制备依托泊苷壳聚糖胶束,并研究壳聚糖对依托泊苷肠吸收的促进作用。方法 用透析法制备依托泊苷壳聚糖胶束,建立依托泊苷HPLC含量测定方法,测定了其包封率与载药量;采用大鼠在体肠循环实验,研究不同剂量壳聚糖对依托泊苷全肠段和各个肠段吸收的影响。结果 壳聚糖胶束平均粒径为139.5 nm,多分散系数为0.569;依托泊苷标准曲线为A=8 436.8C-4 963.8,r=1.000 0,日内、日间精密度符合要求;包封率为（47.3±2.84）%,载药量为（1.10±1.27）%;随着壳聚糖浓度的增加,依托泊苷在全肠段的单位面积吸收量有不同程度的增加;壳聚糖对依托泊苷的吸收促进作用存在着肠道特异性,作用大小顺序：回肠 >空肠 >十二指肠。结论 在十二指肠、空肠和回肠,壳聚糖都不同程度促进了药物的吸收,且在空肠和回肠有显著性的影响。