Abstract
Certain variations in the process parameters (emulsification time, surfactant concentration) were performed in order to prepare BSA-loaded gelatin microspheres with particle size ranging from 1 to 10 µm and high loading efficiency using a procedure originally employed by Tabata and Ikada. In vitro degradation and drug release studies in the presence of trypsin and collagenase, respectively, were performed in order to evaluate the potential of gelatin microspheres as regulated and sustained release systems for oral vaccination. Degradation data showed that the preparation procedure had provided prolonged degradation in the presence of both enzymes, suggesting complete in vivo degradation. Exponential dependence of the amount of drug released on time was evidenced. The diffusion coefficients were superior to 0.5 indicating the Case II anomalous Fickian diffusion, except for the particles smaller than 5 µm where in the presence of collagenase the transition to Super Case II transport was observed due to the higher rate of polymer degradation and BSA diffusion through the matrix. The mathematical modeling of drug release showed a biphasic release pattern in the presence of both enzymes, where the rate constants for the initial time release confirmed the influence of the particle size and/or enzymatic degradation rate on the drug release rate.
Highlights
There is a body evidence which suggests that the absorption of orally administered antigen in the intestines stimulate particular cells in the gut-associated lymphoid tissue (GALT), especially in the Peyer’s patches (PP) leading to dissemination of B and T cells to mucosal effector tissues for subsequent antigen-specific secretory IgA responses
The mathematical modeling of drug release showed a biphasic release pattern in the presence of both enzymes, where the rate constants for the initial time release confirmed the influence of the particle size and/or enzymatic degradation rate on the drug release rate
Effect of formulation and procedure parameters on microspheres size and loading efficacy The mean diameter of microspheres prepared in this study was in the range from 1.20 (+1.96) to 7.03 (+1.23) μm, which is in the frame of optimal size for uptake into GALT and systemic immunoresponsive organs
Summary
There is a body evidence which suggests that the absorption of orally administered antigen in the intestines stimulate particular cells in the gut-associated lymphoid tissue (GALT), especially in the Peyer’s patches (PP) leading to dissemination of B and T cells to mucosal effector tissues for subsequent antigen-specific secretory IgA responses. A number of potential delivery systems, including sustained-antigen releasing polymer based microparticulated carriers have been used for targeting the PP and protecting the antigen of interest from the harsh environment of the GIT [1,2]. Among the natural polymers forming the particles, gelatin is known for its excellent bio-. The treatment of gelatin by glutarldehyde (GTA) gives rise to the formation of scarcely or non-soluble products which can slow down the release of the encapsulated drug. Cross-linking is optimal at neutral pH and requires free non-protonated ε-amino groups of lysine and hydroxylysine to form imines. Additional polymerization by aldol condensation results in covalent intramolecular cross-links connecting distant gelatin molecules
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