Going deep inside bioactive-loaded nanocarriers through Nuclear Magnetic Resonance (NMR) spectroscopy

Background: NMR spectroscopy is based on measuring the intensity of electromagnetic radiation, absorbed by active atomic nuclei, in the radiofrequency region. It is considered as a powerful analytical tool for examining e.g. the molecular structures of edible matrices used in the food industry. This technique attracts wide attention due to the quantitative determination of the molecular species. Principally, the applied external electromagnetic field leads to the changes in the resonance frequency of the nuclei which appears as a spectrum. The isotopic forms of H-1 and C-13 are the commonly considered nuclei in the analysis of food ingredients. Other isotopes including N-15, (17)Q, F-19 and P-31 are less frequently assessed. Scope and approach: One- and two-dimensional NMR spectroscopies along with imaging are able to deliver a large amount of information on the molecular structure, loading content, encapsulation efficiency, optimum formulations, stoichiometry, structural sensitivity in different conditions, molecular interactions and the dynamics of molecular motions, as well as release properties of ingredients involved in nanoencapsulation systems. Specific emphasis of this study has been placed on diverse applications of one and two-dimensional NMR methods in the characterization of nanoencapsulated food constituents. Key findings and conclusions: NMR spectroscopy is nondestructive, noninvasive, highly reproducible, applicable to any type of sample (solid/liquid/semi-solid) and provides a selective analysis methodology for functional groups. As a superlative technique, it can be used for characterizing sensitive nanoencapsulated bioactive agents and their corresponding carriers in different environments without a need for physical separation of ingredients and/or specific treatments.