Chitosan microparticles for mucosal vaccination against diphtheria: oral and nasal efficacy studies in mice.

In this study, the ability of chitosan microparticles to enhance both the systemic and local immune responses against diphtheria toxoid (DT) after oral and nasal administration in mice was investigated.Firstly, DT was associated to chitosan microparticles to determine antigen loading and release. Then DT loaded chitosan microparticles, DT in phosphate buffered saline (PBS) and empty chitosan microparticles (as controls) were fed intragastrically and administered nasally to mice. Mice were also subcutaneously immunised with DT associated with alum. All mice were vaccinated in week 1 and boosted in week 3. Sera were analysed for anti-DT IgG and nasal washings and faeces for anti-DT IgA titres using an enzyme linked immunosorbent assay. Loading capacities of about 25% and loading efficacies of about 100% were obtained after loading the chitosan microparticles with DT. No DT was released at 37 degrees C in PBS. Compared to intragastrical feeding with DT in PBS, a strong enhancement of the systemic and local immune responses against DT were found in mice fed with DT loaded chitosan microparticles. In addition, a dose-dependent immune reaction was observed for mice vaccinated with different doses of DT associated to chitosan microparticles. Significant systemic humoral immune responses were also found after nasal vaccination with DT associated to chitosan microparticles.DT associated to chitosan microparticles results in protective systemic and local immune response against DT after oral vaccination, and in significant enhancement of IgG production after nasal administration. Hence, these in vivo experiments demonstrate that chitosan microparticles are very promising mucosal vaccine delivery systems.

Peroral delivery systems based on superporous hydrogel polymers: release characteristics for the peptide drugs buserelin, octreotide and insulin.

Novel peroral peptide drug delivery systems based on superporous hydrogel (SPH) and SPH composite (SPHC) have recently been developed in our laboratory. In this report the following issues were studied: release of the peptide drugs buserelin, octreotide and insulin from SPH and SPHC polymers and the developed delivery systems, stability of these peptides during the release and the integrity of insulin in the polymeric matrix of SPHC. Release studies from SPH and SPHC polymers revealed that buserelin, octreotide and insulin were released almost completely from the polymers. Peptide release rates from SPH were faster than from SPHC, due to the more porous structure of SPH polymer. All peptides studied in contact with SPHC polymer were stable under different environmental conditions (ambient temperature, 37 degrees C, light and darkness and at pH values 3.2 and 7.2). FTIR studies demonstrated that no covalent binding occurred between insulin and the polymeric SPHC matrix. Release profiles of all peptides from the developed delivery systems showed a time-controlled release profile: after a short lag time of 10-15 min, a burst release of peptides occurred during which more than 80% of peptide was released within 30-45 min. In conclusion, the present delivery systems based on SPH and SPHC show appropriate in vitro properties for application in peroral peptide drug delivery of buserelin, octreotide and insulin, and are therefore promising for further in vivo evaluation.

In vivo buccal delivery of the peptide drug buserelin with glycodeoxycholate as an absorption enhancer in pigs.

PURPOSE: To study the potential of buccal delivery of the peptide drug in pigs. METHODS: Intravenous administration and buccal delivery without and with 10 mM sodium glycodeoxycholate (GDC) as absorption enhancer were investigated as a randomised cross-over study in six pigs. The buccal delivery device consisted of an application chamber with a solution of buserelin and was attached to the buccal mucosa for 4 hours using an adhesive patch. RESULTS: Buccal administration of buserelin resulted in rapidly reached steady state plasma levels. The absolute bioavailability of the peptide after buccal delivery for 4 hours could be increased from 1.0 +/- 0.3 to 5.3 +/- 1.1% (mean +/- SD.) by co-administration of 10 mM GDC (0.45% w/v)). CONCLUSIONS: The results of this study demonstrate that buccal administration with the use of absorption enhancers is a useful approach for the delivery of peptide drugs such as buserelin.

Des-enkephalin-gamma-endorphin (DE gamma E): biotransformation in rat, dog and human plasma.

Biotransformation of [3H-Lys9] DE gamma E was investigated after in vitro incubation of the tritiated peptide with rat, dog and human plasma. In addition, its metabolite profile in blood was studied following intravenous administration to rats and dogs. Half-lives for the in vitro disappearance of DE gamma E in plasma were 13.0 +/- 0.8 min (dog), 15.7 +/- 1.2 min (rat) and 19.2 +/- 0.9 min (human), indicating very rapid degradation of the peptide by proteolytic enzymes. Biotransformation products were identified on the basis of co-chromatography on HPLC with synthetic reference peptides. The six principal fragments appeared to be beta-endorphin (beta E) sequences 7-17, 8-17, 9-17, 6-15, 7-15 and 8-15. The abundance of beta E6-15, beta E7-15 and beta E8-15 in rat and human plasma suggests preferential, subsequent carboxypeptidase and aminopeptidase mechanisms, whereas in dog plasma DE gamma E is predominantly degraded by aminopeptidase activities (major peptide metabolites: beta E7-17 and beta E8-17). In the in vivo studies with rats and dogs the same radioactive peptide fragments were detected in blood as found in the in vitro experiments with plasma. In both species their blood levels were already maximal within a minute after intravenous administration of the parent peptide, thereafter they declined rapidly. 3H-Lysine was the main radioactive metabolite in vivo, exceeding 70% of total radioactivity in rat and dog blood 10 min after 3H-DE gamma E dosing.