Microspheres. Spherical microspheres, prepared by complexation between oppositely charged macromolecules such as chitosan and negatively charged molecules such as tripolyphosphate (TPP) or alginates have received a lot of attention as drug delivery vehicles for protein drug delivery purposes [49, 50]. These microspheres can protect the drugs from the hostile environment of the GI tract, improve drug absorption via the paracellular route and control the drug release at a specific site [51-53]. Xxxxxx et al. and Xxxxx et al. have applied drug containing chitosan microspheres on Caco-2 cell monolayers and showed a strong increase in the transport of buserelin, insulin and vasopressin derivative [20, 54]. A number of investigations were done by Xxx et al. and Xxxxxx et al. for controlled release drug delivery [55, 56]. They showed that variables such as drug concentration, type and concentration of chitosan, the pH of TPP solution, volume of the internal and external phases, gelation time as well as drying conditions can all determine the fate of drug release from chitosan beads. Avadi et al. have used enteric coated capsules containing Brilliant Blue chitosan beads as model hydrophilic drug for colon drug delivery [57]. The γ-scintigraphy images have demonstrated that Eudragit S coated capsules containing Brilliant Blue loaded–chitosan beads are suitable for colon drug delivery. It can be thus concluded that the non toxic chitosan microspheres and beads can increase the bioavailability of the peptide and protein drugs by protecting them from degradation, when they are able to mucoadhesively attach to a specific site on the intestinal tract and to increase drug permeation by opening the tight junctions via the paracellular pathway.
Microspheres. Microspheres are prepared by formulating leuprolide acetate into poly(lactic acid) and/or poly(lactide-co-glycolide), PLGA. PLGA microspheres are not applicable to other drugs because of low loading problems. BioSerenTach developed a new microcapsule with three-layered structure. Between surface layer and backing layer, drug is loaded. The advantage of our Three-layered long-term sustained-release microcapsules are as follows;
