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

Abstract

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 T 1 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).

Novel semisolid SNEDDS based on PEG-30-dipolyhydroxystearate: Development and characterization

“…The values 652 of the chemical shifts of HS15 micelles (Fig.7) in our study are in 653 good agreement with literature data (Momot and Kuchel, 2003). 654 All signals of the aqueous micellar dispersion (Fig.7) The PEG signal was used to evaluate the mobility of the 709 hydrophilic part of the emulsified formulations (Fig.…”

Structural characterization of functionalized gold nanoparticles for drug delivery in cancer therapy: a NMR based approach

“…The diffusion behaviour of BTZ* and BTZ** could be interpreted as a fast exchange between two sites, i.e. bound to the NPs and free or physically entrapped drug molecules 38,51 . In this case, the observed diffusion coefficients are weighted-average values between the free and bound drug species and if we consider fast exchange between these two states, the mole fractions of the free and bound drug molecules could be calculated using the following equation: D = ffreeDfree + fboundDbound where f and D denote the molecular fractions and diffusion coefficients of the free and bound drug molecule and ffree + fbound = 1.…”

“…In this context, diffusion ordered spectroscopy (DOSY) and nuclear Overhauser effect (NOE) spectroscopy, being particularly sensitive to structural and dynamical changes, have become invaluable tools for studies of the molecular transport, interactions and binding processes in complex systems. [36][37][38] Recently published results have proved the capability of NMR spectroscopy as a method for structural analysis of nano-therapeutics. 34,39,40 We have recently designed gold nanoparticles surface modified with functionalized poly(ethylene glycol) (PEGAuNPs) for targeted delivery of the highly toxic anticancer drug Bortezomib (BTZ) (Figure 2).…”

The influence of a cellular size distribution on NMR diffusion measurements

“…Furthermore magnetization decay is not accounted for. Although this is an important effect in practice, especially when the different compartments have different decay rates, this is not the main focus of the present study, but it has been considered elsewhere (Vestergaard-Poulsen et al 2004;Momot and Kuchel 2003). Hence, we will neglect longitudinal and transversal relaxation in the following.…”