THE DEVELOPMENT OF SLOW-RELEASE MOLLUSCICIDE IN A BIODEGRADABLE GELATIN MATRIX

A simple method for the preparation of slow-release compositions of ni closamide, the active molluscicidal ingredient of Bayluscide(R), has b een developed. The compositions, as monolithic discs, were prepared by insolubilizing gelatin by crosslinking treatments with 25% glutaralde hyde. Discs of six different extents of cross-linking containing 20% m olluscicide (w/w) were made. Evaluation of these compositions was carr ied out under both shea-term hydrodynamic conditions (flow-through met hod), and long-term static conditions, using dechlorinated tap water. The results proved that the release profiles, mechanical stability, an d swelling ratios of the compositions varied depending on the cross-li nking treatment periods (CTP). The release mechanism of the cross-link ed compositions was found to approach zero-order release behavior for all the compositions. The release rate constants of different formulat ions ranged from 0.09 to 1.42 mu g/cm(2) min(-1). The percent degradat ion of the crosslinked gelatin matrices was considerably affected by C TP, ranging from 5.5 to 82.0%. Bioassays were carried out using Biomph alaria alexandrina, the snail vectors of schistosomiasis. A daily 100% snail mortality prevailed for 52 and 73 days with the non-cross-linke d and cross-linked matrices (CTP = 0.25 h), respectively.