Rotating beads method

Recently, Yoshikawa et al. [70] reported a new in vitro dissolution test, called the rotating beads method, for drugs formulated in pressure-controlled colon delivery capsules. This dissolution method was applied to acetominophen sustained-release tablets and two other drugs having low solubility in the colon, tegafur and 5-ASA. There was good correlation between the in vitro dissolution rates and the in vivo absorption rates. 

Yoshikawa, Y., Hu, Z., Kimura, G., Muranishi, M., Yoshikawa, H., and Takada, K., A dissolution test for a pressure-controlled colon delivery capsule rotating beads method, J. Pharm. 

Colon and Maloney demonstrated another packing method that also avoids pumping the slurry through the column [51]. They used centripetal force to drive beads, which have a higher density than the liquid contained in solvent slurry, through the capillary. Their packing equipment enables a rotation speed of up to 3000 rpm at which the packing time is only 5-15 min. 

Physical Methods Physical methods include mechanical disruption by milling, homogenization, or ultrasonication. Typical high-speed bead mills are composed of a grinding chamber filled with glass or steel beads which are agitated with disks or impellers mounted on a motor-driven shaft. The efficiency of cell disruption in a bead mill depends on the concentration of the cells, the amount and size of beads, and the type and rotation speed of the agitator. The optimum wet solid content for the cell suspension for a bead mill is typically somewhere between 30 percent to 60 percent by volume. The amount of beads in the chamber is 70 percent to 90 percent by... 

A variation of this method utilizes cells that are immobilized on a surface but have a freely rotating flagellum attached to an antibody-coated latex bead (40, 41). 

To estimate Lc more accurately Yamakawa and Shimada [52] computed (5 ) of polymethylene-like rotational isomeric state models with excluded volume by a Monte Carlo method. They considered that bead-bead interactions higher than ones leading to the pentane effect contribute to excluded-volume effects. They found that the simulated polymer in the unperturbed state can be modeled by a wormlike chain and that (5 )/(4 rtK) of perturbed chains begins to deviate from those of unperturbed ones at uk of 3—5. Thus, the Lc by Yamakawa and... 

---