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CUR Solvatochromicity submitted manuscript with SI.pdf (5.49 MB)

Ultra-High to Ultra-Low Drug Loaded Micelles: Probing Host-Guest Interactions by Fluorescence Spectroscopy

submitted on 07.06.2019, 05:58 and posted on 07.06.2019, 15:10 by Michael M Lübtow, Henning Marciniak, Alexander Schmiedel, Markus Roos, Christoph Lambert, Robert Luxenhofer
Polymer micelles are an attractive means to solubilize water insoluble compounds such as drugs. Drug loading, formulations stability and control over drug release are crucial factors for drug loaded polymer micelles. The interactions between the polymeric host and the guest molecules are considered critical to control these factors but typically barely understood. Here, we compare two isomeric polymer micelles, one of which enables ultra-high curcumin loading exceeding 50 wt.%, while the other only allows a drug loading of only 25 wt.%. In the low capacity micelles, steady-state fluorescence revealed a very unusual feature of curcumin fluorescence, a high energy emission at 510 nm. Time-resolved fluorescence upconversion showed that the fluorescence life time of the corresponding species is too short in the high-capacity micelles, preventing an observable emission in steady-state. Therefore, contrary to common perception, stronger interactions between host and guest can be detrimental to the drug loading in polymer micelles.


Deutsche Forschungsgemeinschaft

Evonik Foundation

Bavarian Ministry of Education, Culture, Research, and the Fine Arts.


Email Address of Submitting Author


University of Würzburg



ORCID For Submitting Author


Declaration of Conflict of Interest

M.M.L. and R.L are listed as inventors on a patent application pertinent to materials discussed in this contribution.

Version Notes

first manuscript version submitted for peer review