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  • Loading‐Dependent Structura...
    Pöppler, Ann‐Christin; Lübtow, Michael M.; Schlauersbach, Jonas; Wiest, Johannes; Meinel, Lorenz; Luxenhofer, Robert

    Angewandte Chemie (International ed.), December 16, 2019, Letnik: 58, Številka: 51
    Journal Article

    Detailed insight into the internal structure of drug‐loaded polymeric micelles is scarce, but important for developing optimized delivery systems. We observed that an increase in the curcumin loading of triblock copolymers based on poly(2‐oxazolines) and poly(2‐oxazines) results in poorer dissolution properties. Using solid‐state NMR spectroscopy and complementary tools we propose a loading‐dependent structural model on the molecular level that provides an explanation for these pronounced differences. Changes in the chemical shifts and cross‐peaks in 2D NMR experiments give evidence for the involvement of the hydrophobic polymer block in the curcumin coordination at low loadings, while at higher loadings an increase in the interaction with the hydrophilic polymer blocks is observed. The involvement of the hydrophilic compartment may be critical for ultrahigh‐loaded polymer micelles and can help to rationalize specific polymer modifications to improve the performance of similar drug delivery systems. From bulk properties to a molecular level understanding: Solid‐state NMR spectroscopy complemented by X‐ray diffraction data and calculations gives insights into the loading‐dependent structure of micelles formed by amphiphilic triblock copolymers. As coordination sites in the core become saturated, stabilization of higher loadings requires coordination by the hydrophilic corona, which compromises dissolution.