Pulsed field gradient nuclear magnetic resonance as a tool for studying drug delivery systems

Pulsed field gradient (PFG) nuclear magnetic resonance (NMR) is a versatile method for studying molecular transport and exchange in solution. Stejskal-Tanner diffusion plots can be used to distinguish between chemical species even in the absence of chemical shift or T1 resolution, provided that certain conditions are satisfied. This can be used advantageously in colloidal drug delivery systems containing two drug populations, free and bound, which often differ only by their diffusion coefficients. We discuss the conditions required for the resolution of the two pools in Stejskal-Tanner plots, as well as the effects of chemical exchange. We also present two practical examples of this analysis: surfactant micelles containing the general anesthetic propofol and lipid/water liquid crystalline mesophase vehicles (cubosomes)