Molecular Mobility as a Predictor of the Water Sorption by Annealed Amorphous Trehalose

• Published in: Pharmaceutical research Vol. 30; no. 3; pp. 714 - 720
• Main Authors: Bhardwaj, Sunny P., Suryanarayanan, Raj
• Format: Journal Article
• Language: English
• Published: Boston Springer US 01.03.2013; Springer; Springer Nature B.V
• Subjects: Annealing; Biochemistry; Biological and medical sciences; Biomedical and Life Sciences; Biomedical Engineering and Bioengineering; Biomedicine; Calorimetry, Differential Scanning; Crystallization; Dielectric Spectroscopy; Freeze Drying; General pharmacology; Hot Temperature; Medical Law; Medical sciences; Molecular biology; Pharmaceutical technology. Pharmaceutical industry; Pharmacology; Pharmacology. Drug treatments; Pharmacology/Toxicology; Pharmacy; Research Paper; Sorption; Thermodynamics; Trehalose - chemistry; Water; Water - chemistry; molecular mobility; trehalose; water sorption; enthalpic recovery; annealing; Annealing; Water sorption; Pharmaceutical technology; Trehalose; Molecular mobility; Predictive factor
• ISSN: 0724-8741; 1573-904X
• DOI: 10.1007/s11095-012-0910-6

ABSTRACT Purpose The work aims at investigating the correlation of water sorption potential with different measures of molecular mobility in an annealed amorphous model compound (trehalose). Methods Amorphous trehalose, prepared by freeze-drying, was annealed at 100°C (17°C < T g ) for up to 120 h. Global molecular mobility was studied using a broadband dielectric spectrometer in the frequency range of 10 6 –10 −2  Hz. Enthalpic recovery was measured by differential scanning calorimetry and water sorption profiles were obtained using an automated vapor sorption balance. Results As a function of annealing time, there was an increase, both in average α -relaxation time and enthalpic recovery and a decrease in the amount of sorbed water. A strong linear correlation was observed between the water sorption potential and the dielectric relaxation time, indicating a common underlying mechanism of the effect of annealing time on these properties. Enthalpic recovery, which is widely used as a measure of structural relaxation, did not correlate well with the extent of water sorption. Conclusions The α -relaxation time can be used as a predictor of the water sorption potential of amorphous trehalose. It will be of interest and value to develop such predictive models for other amorphous compounds of pharmaceutical interest.