title: Solid state 13C NMR investigation of impact of annealing in lyophilized glasses.
abstract: The purpose of this study was to investigate the impact of annealing on molecular mobility in lyophilized glasses, composed of a saccharide excipient and a small concentration of aspartame as a model "drug." Changes in molecular dynamics during annealing were monitored through carbon ((13)C) T(1) and T(1 rho) nuclear magnetic resonance relaxation times of the aspartame and the saccharides. Two different saccharides were studied, sucrose and trehalose. The local mobility of the aspartame guest was found to correlate closely with the overall structural relaxation monitored through calorimetric methods in the aspartame: sucrose formulation. In general terms, annealing leads to longer NMR relaxation times, indicating a slowing of the local dynamics. By contrast, annealing had only a minimal effect on the NMR relaxation times in aspartame: trehalose. Specificity of solid state NMR in detecting molecular mobility in guest and host molecules showed that sucrose provided a homogenous matrix for the guest drug as compared to the trehalose.
authors.affiliation: Department of Pharmaceutical Sciences, School of Pharmacy, University of Connecticut, U-3092, Storrs, Connecticut 06269, USA.
authors.forename: Suman A
authors.initials: SA
authors.lastname: Luthra
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Pikal
authors.forename: Marcel
authors.initials: M
authors.lastname: Utz
mesh_terms: D001218:Aspartame / Q000737:chemistry; D005612:Freeze Drying; D005898:Glass; D006358:Hot Temperature; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D014199:Trehalose / Q000737:chemistry
chemical_list: D014199:Trehalose; D001218:Aspartame