HR-MAS NMR Spectroscopy: novel technologies to measure delivery performance

Abstract Understanding the transport phenomena at a molecular level is of key importance to explain and regulate macroscopic processes such as controlled-release and safe delivery of drugs. Among all the experimental techniques, nuclear magnetic resonance (NMR) spectroscopy is widely used to study structure, rotational and translational dynamics of small-drug molecules in liquid state solution. High-resolution magic angle spinning (HR-MAS) is a further recent advancement of the NMR spectroscopic technique as it provides a direct analysis of heterogeneous soft materials such as gels, polymers, and cells characterized by low molecular mobility. Indeed, HR-MAS NMR technique is based on spinning the sample at the magic angle (MAS) to reduce resonance line broadening caused by anisotropic interactions inherent to semisolid materials and enforced to small molecules encapsulated in gel systems. Thus, high-resolution (HR) signals are observed in heterogeneous semisolid materials and biological samples. Several HR approaches, in particular pulse field gradient spin echo (PGSE) experiments, are used to study the motion regime of small drugs entrapped in swollen polymers or hydrogels.