Elaboration of alginate microspheres by emulsification-ionotropic gelation technique containing bioadhesive polymers. A morphological study of the systems.

Natural polymers have great advantages becausethey have good biocompatibility, specificdegradation and the feasibility to incorporatedrugs into their matrices. Amongst the naturalpolymers, alginate has been used by manyworkers as a matrix for the controlled release ofdrugs. It has an ability to cause abioadhesion with mucosal membranes. Drugdelivery in the oral mucosa has many advantagesfor drugs such as local anaesthetics. However,this site of the oral cavity is subjected to theinfluence of the salivation process, that canremove the remanent dosage form from theapplication site. Therefore, the addition of abioadhesive to the bead formulation could avoidthis removing effect. The most commonly used technique for carrying drugs in an alginate matrix is by extrudingdroplets of alginate drug solution or dispersioninto a calcium chloride bath. Gelation occurs byan ionic interaction between the calcium ionsand the carboxylate anion of G-G blocks ascalcium ions diffuse from the external sourceinto the droplet. An alternative to thesetechniques is the emulsification method, whichallows the encapsulation of the drug in small beads. Bead formation through emulsion techniques hasnot been adequately investigated withbioadhesive polymers. An emulsion of analginate aqueous solution in oil can be added toCaCl2 solution, and thereby leads to beadformation. However, particle size cannot beeasily controlled and the beads tend to coagulate into large masses before hardening properly. In the present study, the gelation of alginate-Chitosan (CH) and alginate-Gantrez® solution isachieved through the emulsification of thissolution with the lipophilic phase. In a first stage,a morphological study by SEM has beenrealized, in order to determine the presence orabsence of bead aggregates, and their shape and parameters.