Drug release characteristics from combined poly(isobutylcyanoacrylate) and cyclodextrin nanoparticles loaded with progesterone

The release characteristics of progesterone from combined nanoparticles of poly(isobutylcyanoacrylate) and hydroxypropyl-beta-cyclodextrin prepared by emulsion polymerization were determined by a "sample and separate" technique. Progesterone was molecularly dispersed in the nanoparticles. There are three distinct mechanisms that may explain the release of progesterone. First, the burst effect could be attributed to the release of progesterone loosely associated to the particles, possibly at their surface. Second, by increasing the solvent power of the dissolution medium, it was possible to demonstrate that a fraction of the progesterone was molecularly entrapped into the polymeric network constitutive of the nanoparticles. Finally, a third fraction of progesterone, which was either firmly entrapped or adsorbed on the poly(isobutylcyanoacrylate) chains, could be released only after particle hydrolysis by esterases.