Comparison between nuclear magnetic resonance profiling and the source/sink approach for characterizing drug...

In controlled drug delivery, the drug diffusion coefficient in a given matrix is a key factor for predicting its release rate. In this work, we compare (31)P nuclear magnetic resonance (NMR) profiling for obtaining the mutual-diffusion coefficient (D(m)(gel)) of a drug in hydrogel with results obtained from conventional source/sink experiments. Despite the fact that NMR profiling is a powerful approach for measuring transport properties, it is rarely used for characterizing drug diffusion in gel matrices in pharmaceutical sciences. This work provides an illustration of the applicability of this technique and highlights its advantages for studying drug release systems. The comparison with results obtained from the source/sink experiment clearly establishes the validity of the NMR profiling approach. Alendronate was used as a model drug while curdlan, a gel-forming bacterial polysaccharide, served as a model biomaterial. The determined (D(m)(gel)) value (5.6 ± 0.3 × 10(-10) m(2)/s) agrees with the one obtained from a conventional source/sink experiment (5.4 ± 0.5 × 10(-10) m(2)/s). In addition, the alendronate self-diffusion coefficients in solution (D(s)(sln)) and in the hydrogel (D(s)(gel)) were measured on the same system using pulse-field gradient (PFG) (31)P NMR. These supplementary parameters provided a more detailed characterization of the drug transport properties in the gel matrix.