Effect of Tripolyphosphate (TPP) on the Controlled Release of

ABSTRACT − Soybean phosphatidylcholine microparticles loaded with cyclosporin A (CsA) were prepared by the mod-ified emulsion solvent diffusion and ionic gelation method, in which chitosan on the surface of the microparticles was cross-linked with various concentrations of tripolyphosphate (TPP). The morphology of the particles was characterized by scan-ning electron microscopy (SEM). The change of particle size and zeta-potential by chitosan on the surface of the lipid micro-particles were systematically observed. The encapsulation efficiency and loading capacity of CsA in the particles were determined by high performance liquid chromatography (HPLC). In vitro release kinetics was studied using the dialysis method. In the results, the mean particle size and the zeta-potential of lipid microparticles increased when the attached chi-tosan was cross-linked (from 2.5 to 6.2 µm and from − 37.0 to +93.0 mV, respectively). The cyclosporin A-loaded lipid microparticles appeared discrete and spherical particles with smooth surfaces. The encapsulation efficiency of CsA was between 79 % and 90 % while the loading capacity was between 41 % and 56%. In vitro release study showed that the cross-linkage of chitosan by TPP significantly delayed the release of CsA from the particles in a concentration-dependent manner. Thus, the release of CsA from the lipid microparticles could be controlled by tripolyphosphate used as a cross-linking agent. Key words − Cyclosporin A, Chitosan, Tripolyphosphate (TPP), Microparticles, Controlled release Cyclosporin A (CsA), used as the first line therapy for the prevention of xenograft rejection following organ transplan-tation, is an extremely lipophilic cyclic peptide which is insol-uble in water. Research on CsA, thus, has been mainly focused on developing a delivery system that could enhance its sol-ubility and/or control its release profile. Liposomes, 1) micro-emulsion