Self-Assembly of Cyclodextrins and Their Complexes in Aqueous Solutions

Area of Science:

• Pharmaceutical Science
• Physical Chemistry
• Materials Science

Background:

• Cyclodextrins (CDs) are widely used pharmaceutical excipients with favorable toxicological profiles.
• CDs are utilized in early-stage drug development, including toxicology and Phase I trials.
• High concentrations of CDs can lead to spontaneous self-assembly into microparticles in aqueous solutions.

Purpose of the Study:

• To investigate the mechanisms and contributing factors behind cyclodextrin aggregate formation.
• To understand how inclusion complex formation influences CD aggregation.
• To elucidate the physiochemical properties governing CD self-assembly.

Main Methods:

• Analysis of aggregate formation in pure CD solutions and in the presence of inclusion complexes.
• Investigation of the effect of CD concentration on aggregate formation.
• Characterization of aggregate size, including subvisible and visible particles.

Main Results:

• Negligible aggregate formation occurs in pure cyclodextrin solutions.
• Aggregate formation is significantly enhanced upon inclusion complex formation.
• The extent of aggregation increases with increasing cyclodextrin concentration.
• Aggregate diameters are typically less than 300 nm, but visible aggregates can form.

Conclusions:

• Cyclodextrin aggregation is concentration-dependent and exacerbated by inclusion complex formation.
• The self-assembly behavior of CDs differs from typical amphiphiles and resembles linear oligosaccharides.
• Understanding CD aggregation is critical for preventing product rejection and ensuring reliable analytical data in pharmaceutical development.