14N1H HMQC Solid-State NMR as a Powerful Tool to Study Amorphous Formulations – an Exemplary Study of Paclitaxel Loaded Polymer Micelles

We present ¹⁴N-¹H HMQC MAS NMR experiments in the solid state as a promising tool to study amorphous formulations. Poly(2-oxazoline) based polymer micelles loaded with different amounts of the cancer drug paclitaxel serve to highlight the possibilities offered by these experiments: While the very similar ¹⁵N chemical shifts hamper a solid-state NMR characterization based on this nucleus, ¹⁴N is a very versatile alternative. ¹⁴N-¹H HMQC experiments yield well-separated signals, which are spread over a large ppm range, provide information on the symmetry of the nitrogen environment and probe ¹⁴N-¹H through-space proximities.