Evaluation of solid dispersions on a molecular level by the Raman mapping technique

Area of Science:

• Pharmaceutical Sciences
• Analytical Chemistry
• Materials Science

Background:

• Troglitazone possesses two asymmetric carbons, leading to four isomers.
• Crystalline troglitazone exists as two diastereomer pairs (RR/SS and RS/SR) with distinct melting points.
• Solid dispersions are crucial for drug formulation, impacting stability and bioavailability.

Purpose of the Study:

• To evaluate the utility of Raman spectroscopy and mapping for characterizing troglitazone in solid dispersions.
• To discriminate between crystalline diastereomer pairs (RR/SS, RS/SR) and the amorphous form of troglitazone.
• To analyze the distribution of troglitazone and polyvinylpyrrolidone (PVP) within solid dispersions.

Main Methods:

• Preparation of troglitazone-polyvinylpyrrolidone (PVP) solid dispersions using a closed melting method.
• Application of Raman spectroscopy and Raman mapping techniques.
• Analysis of spectral data to identify crystalline and amorphous forms and diastereomer pairs.

Main Results:

• Raman mapping successfully identified the co-existence of crystalline and amorphous troglitazone in solid dispersions.
• The technique differentiated between the RR/SS and RS/SR crystalline diastereomer pairs.
• Distribution patterns of both troglitazone and PVP were visualized, offering insights into amorphous transformation mechanisms.

Conclusions:

• Raman spectroscopy and mapping are valuable tools for assessing solid dispersion states, including diastereomer discrimination.
• The method aids in understanding drug crystallization and amorphous transformation during solid dispersion preparation.
• This technique provides a comprehensive evaluation of drug-carrier interactions and physical states.