Use of Mixer Torque Rheometer to Clarify the Relationship between the Kneading States of Wet Mass and the Dissolution of Final Product in High Shear Granulation.

The properties of wet mass, which indicate the progress of high shear granulation processes, usually have an effect on final product properties, such as tablet dissolution. The mixer torque rheometer (MTR) is a useful tool for quantitatively measuring the 'kneading state' of wet mass and detecting differences in granules. However, there have been no studies of the relationship between the MTR torque and the final product properties to date. In this study, we measured the MTR torque of wet granules at different kneading states, which were prepared by changing the granulation conditions. We then evaluated the relationship between the MTR torque and the dissolution rate of the final product properties. The amperage of the high shear granulator is usually monitored during granulation, but we could not detect a difference in the kneading state through the amperage. However, using MTR torque we were able to quantify the difference of the wet mass. Moreover, MTR torque showed a high correlation with dissolution, compared with the correlations with other intermediate properties, such as granules particle size and tablet hardness. These other properties are affected by following processes and are not properties that directly relate to the kneading state. Thus, MTR torque is a property of wet mass after granulation, and it can be used to directly evaluate differences of the kneading state, and as a result, dissolution. These results indicate the importance of controlling the kneading state, i.e., the progress of granulation, and the utility of MTR for detecting differences in wet mass.

Nano-scale and molecular-level understanding of wet-milled indomethacin/poloxamer 407 nanosuspension with TEM, suspended-state NMR, and Raman measurements.

We investigated the formation and stabilization mechanisms of indomethacin (IMC)/poloxamer 407 nanosuspensions. Stable nanosuspensions were prepared via 24 h wet-milling of three IMC forms (γ form, α form, and amorphous) with poloxamer 407. Cryogenic-transmission electron microscopy images of nanoparticles obtained using γ-form IMC indicated a rhombic-plate shape. In contrast, needle-like nanoparticles were observed in the nanosuspensions of α-form and amorphous IMC. Suspended-state cross polarization 13C NMR and Raman measurements directly detected the molecular states of IMC in nanosuspensions. IMC existed in its initial crystal form when γ-form and α-form IMC were used; amorphous IMC transformed into crystalline α-form IMC. Suspended-state 13C pulse saturation transfer NMR measurements revealed the molecular state of poloxamer 407 on the surface of IMC crystals. The polypropylene oxide group adsorbed to the IMC crystal surface via hydrophobic interactions, while the polyethylene oxide group on the surface was as flexible as that in polymeric micelles. The equilibrium of poloxamer 407 between micelle and nanocrystal surfaces was slower than the NMR time scale, which could stabilize the dispersion of the nanoparticles in water. The time interval evaluation during the wet-milling process revealed that α-form IMC nanocrystals could be efficiently prepared via wet-milling using amorphous IMC as the starting material.