use of hot‐melt extruded corn starch matrices as drug carrier systems: A thermophysical characterization

Corn starches with varying ratios of amylose to amylopectin are plasticized by hot‐melt extrusion. The nearly amorphous matrices are loaded with different model drug substances to evaluate the interaction of plasticized starch and active pharmaceutical ingredients with varying solubility. Two different thermal analytical methods are applied to provide a detailed insight into the thermal behavior of the material: Differential scanning calorimetry (DSC) and dymamic mechanical thermal analysis (DMTA). A comparison of both methods provides a more detailed understanding of the interaction of different constituents in the range of the glass transition temperature (Tg). Activation energies of Tgs can be determined by applying Arrhenius equation. Residual moistures of the unprocessed starches and the extruded products are compared using thermogravimetric analysis. Extrusion processing causes no changes of the dynamic vapor sorption behavior in the targeted storage conditions. Crystalline structure of the matrices has been studied via XRD. Recrystallization effects can be observed for high amylose corn starches, whereas for waxy corn starches no recrystallization occurs. The crystal state of the final product during API addition can be strongly linked to corresponding solubility. Drug loading with phenazone, a high soluble API, leads to the formation of a solid solution, whereas addition of the more lipophilic acetaminophen results in the formation of a solid dispersion.