Spatial location of indomethacin associated with unimeric amphiphilic carrier macromolecules as determined by nuclear magnetic resonance spectroscopy

Abstract

A combination of nuclear magnetic resonance (NMR) techniques including, proton NMR, relaxation analysis, two-dimensional nuclear Overhauser effect spectroscopy, and diffusion-ordered spectroscopy, has been used to demonstrate the spatial location of indomethacin within a unimolecular micelle. Understanding the location of drugs within carrier molecules using such NMR techniques can facilitate rational carrier design. In addition, this information provides insight to encapsulation efficiency of different drugs to determine the most efficient system for a particular bioactive. This study demonstrates that drugs loaded by the unimolecular amphiphile under investigation are not necessarily encapsulated but reside or localize to the periphery or interfacial region of the carrier molecule. The results have further implications as to the features of the unimolecular carrier that contribute to drug loading. In addition, evidence of drug retention associated with the unimolecular surfactant is possible in organic media, as well as in an aqueous environment. Such findings have implications for rational carrier design to correlate the carrier features to the drug of interest and indicate the strong retention capabilities of the unimolecular micelle for delivery applications. Copyright © 2016 John Wiley & Sons, Ltd.

How Does the Encapsulation of Porphyrinic Photosensitizers into Polymer Matrices Affect Their Self‐Association and Dynamic Properties?

“…The 1 H NMR transverse spin–spin relaxation times ( T 2 ) were determined for selected systems to obtain information about their segmental molecular dynamic properties. Proton relaxation time measurements are well‐established methods to study interactions or binding of small molecules with large receptor molecules . Among other factors affecting the transversal relaxation rates, molecular motions expressed as the molecular rotational correlation time ( τ C ) have a large impact on dipolar relaxation .…”

“…Proton relaxa-tion time measurements are well-established methods to study interactions or binding of small moleculesw ith large receptor molecules. [49][50][51] Amongo ther factors affecting the transversal relaxation rates, molecular motions expressed as the molecular rotational correlation time (t C )h ave al arge impact on dipolar relaxation. [50] This leads to an increase in the relaxation rates of guest molecules upon binding to al arge host with long correlation times t C .A ccordingly,t he extent of restricted mobility of the porphyrinic compounds and the strength of binding to the polymer are reflected in their T 2 relaxation times.…”