TOF-SIMS characterization and imaging of controlled-release drug delivery systems

Time-of night secondary ion mass spectrometry (TOF-SIMS) was used for the a nalysis of multilayer drug beads that serve as controlled-release drug deli very systems. TOF-SIMS analysis of a cross section of each bead system allo wed molecular chemical information to be gained from all of the layers simu ltaneously, in situ, The integrity of each of the layers was evaluated thro ugh imaging of specific ion species for the drug, excipient, and coating ma terials. The three beads in this study each showed a unique distribution of ingredients. Images of the parent molecular ion for each drug (theophyllin e, paracetamol, prednisolone) showed their distribution ranged from microme ter-sized particles in one bead cross section to almost homogeneous in anot her bead cross section. The chemical composition of each of the layers in t he beads was evaluated through mass spectrometry; the ingredients did not a lways match the manufacturer's specification. In addition, many common drug head ingredients were analyzed as pure substances, providing TOF-SIMS refe rence spectra of these materials for the first time.