Triamcinolone solubilization by (2-hydroxypropyl)-β-cyclodextrin: A spectroscopic and computational approach.

Area of Science:

• Pharmaceutical Science
• Supramolecular Chemistry
• Materials Science

Background:

• Triamcinolone acetonide (TrA) is a corticosteroid with poor aqueous solubility, limiting its pharmaceutical applications.
• Cyclodextrins, such as (2-hydroxypropyl)-β-cyclodextrin (HPβCD), are widely used to improve the solubility of poorly soluble drugs.
• Understanding the molecular interactions between TrA and HPβCD is essential for optimizing drug formulation.

Purpose of the Study:

• To elucidate the molecular mechanisms underlying the solubility enhancement of triamcinolone acetonide (TrA) by (2-hydroxypropyl)-β-cyclodextrin (HPβCD).
• To characterize the drug-cyclodextrin interactions in both solution and solid states.
• To provide insights for the rational design of novel pharmaceutical formulations.

Main Methods:

• A multidisciplinary approach combining UV-Vis spectroscopy, Nuclear Magnetic Resonance (NMR) spectroscopy (including DOSY), and Raman spectroscopy.
• Determination of association constants using phase solubility diagrams and the Foster-Fyfe method.
• Computational methods and Nuclear Overhauser Effect (NOE) measurements for structural elucidation.
• Raman imaging for solid-state analysis and homogeneity assessment.

Main Results:

• Phase solubility diagrams and spectroscopic data confirmed the formation of TrA/HPβCD complexes in aqueous solution.
• NMR DOSY indicated the formation of drug/cyclodextrin aggregates, with ROE measurements providing stereochemical details of the inclusion process.
• Raman spectroscopy detected a specific interaction between the hydroxyacyl chain and HPβCD in the solid state, not observed in solution.
• Raman imaging demonstrated molecular homogeneity at a 1:7 TrA/HPβCD molar ratio, while TrA crystallization occurred at a 1:3.5 ratio.

Conclusions:

• The study successfully detailed the molecular interactions between TrA and HPβCD using a combination of spectroscopic and computational techniques.
• HPβCD effectively promotes TrA solubility through inclusion complexation in solution and molecular dispersion in the solid state.
• The findings highlight the utility of integrated spectroscopic methods for characterizing drug-cyclodextrin systems and guiding pharmaceutical formulation development.