Amphiphilic poly( N-(2-hydroxypropyl)methacrylamide) copolymers ( pHPMA) bearing cholesterol side groups in phosphate buffer saline self-assemble into nanoparticles (NPs) which can be used as tumor-targeted drug carriers. It was previously shown by us that human serum albumin (HSA) interacts weakly with the NPs. However, the mechanism of this binding could not be resolved due to overlapping of signals from the complex system. Here, we use fluorescence labeling to distinguish the components and to characterize the binding: On the one hand, a fluorescent dye was attached to pHPMA, so that the diffusion behavior of the NPs could be studied in the presence of HSA using fluorescence lifetime correlation spectroscopy. On the other hand, quenching of the intrinsic fluorescence of HSA revealed the origin of the binding, which is mainly the complexation between HSA and cholesterol side groups. Furthermore, a binding constant was obtained.

Department of Pharmacy Pharmaceutical Technology and Biopharmaceutics Ludwig Maximilians Universität München Butenandtstr 5 81377 Munich Germany

Institute of Macromolecular Chemistry Czech Academy of Sciences Heyrovského nám 2 162 06 Prague 6 Czech Republic

Physik Department Physik weicher Materie Technische Universität München James Franck Str 1 85748 Garching Germany

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Molecular Mechanisms of the Interactions of N-(2-Hydroxypropyl)methacrylamide Copolymers Designed for Cancer Therapy with Blood Plasma Proteins