Influence of Hydrophobic Side-Chain Length in Amphiphilic Gradient Copoly(2-oxazoline)s on the Therapeutics Loading, Stability, Cellular Uptake and Pharmacokinetics of Nano-Formulation with Curcumin.

Due to the simple one-step preparation method and a promising application in biomedical research, amphiphilic gradient copoly(2-oxazoline)s are gaining more and more interest compared to their analogous block copolymers. In this work, the curcumin solubilization ability was tested for a series of amphiphilic gradient copoly(2-oxazoline)s with different lengths of hydrophobic side-chains, consisting of 2-ethyl-2-oxazoline as a hydrophilic monomer and 2-(4-alkyloxyphenyl)-2-oxazoline as a hydrophobic monomer. It is shown that the length of the hydrophobic side-chain in the copolymers plays a crucial role in the loading of curcumin onto the self-assembled nanoparticles. The kinetic stability of self-assembled nanoparticles studied using FRET shows a link between their integrity and cellular uptake in human glioblastoma cells. The present study demonstrates how minor changes in the molecular structure of gradient copoly(2-oxazoline)s can lead to significant differences in the loading, stability, cytotoxicity, cellular uptake, and pharmacokinetics of nano-formulations containing curcumin. The obtained results on the behavior of the complex of gradient copoly(2-oxazoline)s and curcumin may contribute to the development of effective next-generation polymeric nanostructures for biomedical applications.

Radical in the Peroxide-Produced F-Type Ferryl Form of Bovine Cytochrome c Oxidase.

The reduction of O2 in respiratory cytochrome c oxidases (CcO) is associated with the generation of the transmembrane proton gradient by two mechanisms. In one of them, the proton pumping, two different types of the ferryl intermediates of the catalytic heme a3-CuB center P and F forms, participate. Equivalent ferryl states can be also formed by the reaction of the oxidized CcO (O) with H2O2. Interestingly, in acidic solutions a single molecule of H2O2 can generate from the O an additional F-type ferryl form (F•) that should contain, in contrast to the catalytic F intermediate, a free radical at the heme a3-CuB center. In this work, the formation and the endogenous decay of both the ferryl iron of heme a3 and the radical in F• intermediate were examined by the combination of four experimental approaches, isothermal titration calorimetry, electron paramagnetic resonance, and electronic absorption spectroscopy together with the reduction of this form by the defined number of electrons. The results are consistent with the generation of radicals in F• form. However, the radical at the catalytic center is more rapidly quenched than the accompanying ferryl state of heme a3, very likely by the intrinsic oxidation of the enzyme itself.