Dissolution rate studies of cholesterol monohydrate in bile acid-lecithin solutions using the rotatingdisk method

Area of Science:

• Biophysics
• Physical Chemistry
• Gastroenterology

Background:

• Cholesterol gallstones are a common ailment, and their dissolution is crucial for non-surgical treatment.
• Understanding the kinetics of cholesterol dissolution in bile is essential for developing effective therapies.

Purpose of the Study:

• To investigate the kinetics of cholesterol gallstone dissolution in simulated bile.
• To quantify the contributions of mass transfer resistance and interfacial barriers to dissolution rates.
• To explore kinetic interpretations for slow dissolution in bile acid-lecithin solutions.

Main Methods:

• Employed a physical model approach simulating in vivo conditions.
• Utilized the rotating-disk dissolution method and Levich theory.
• Assessed diffusion-convection mass transfer and interfacial barrier effects.

Main Results:

• A significant interfacial barrier was identified for cholesterol gallstone and cholesterol monohydrate pellet dissolution in bile acid-lecithin solutions.
• Cholesterol dissolution rates were 2-20 times slower than diffusion-controlled rates, dependent on agitation.
• Dissolution rates approached theoretical diffusion-convection-controlled rates with dissolution accelerators.

Conclusions:

• The study highlights the substantial role of interfacial barriers in limiting cholesterol gallstone dissolution rates.
• Two kinetic interpretations were proposed: slow interfacial kinetics or slow cholesterol solubilization in the diffusion layer.
• An analytical mathematical solution was derived for the latter interpretation, providing a framework for further research.