Biocompatible polymeric micelles with polysorbate 80 for use in brain targeting.

In this paper, the synthesis and characterization of novel amphiphilic graft copolymers based on an α,ß-poly(N-2-hydroxyethyl)-D,L-aspartamide (PHEA) backbone and D,L-polylactic acid (PLA) hydrophobic side chains are reported. These copolymers were obtained starting from PHEA-ethylenediamine (PHEA-EDA), which was functionalized with polysorbate 80 (PS(80)) and/or PLA in order to obtain the PHEA-EDA-PS(80)-PLA and PHEA-EDA-PLA samples, respectively. The degrees of derivatization, DD(PS80) and DD(PLA), of PHEA-EDA-PS(80)-PLA, calculated by (1)H-NMR, resulted in being 1.2 ± 0.03 mol% and 0.54 ± 0.05 mol%, respectively, while that of PHEA-EDA-PLA was found to be 0.60 ± 0.05 mol%. Size exclusion chromatography (SEC) analysis confirmed the occurrence of derivatization, the molecular weight values being close to the theoretical ones. Polymeric micelles from PHEA-EDA-PLA and PHEA-EDA-PS(80)-PLA copolymers were obtained by using the dialysis method and were characterized in terms of mean size, zeta potential, critical aggregation concentration (CAC), and surface composition by x-ray photoelectron spectroscopy (XPS) analysis, which demonstrated the presence of PS(80) onto the PHEA-EDA-PS(80)-PLA micelle surface. In vitro experiments demonstrated that these systems had no cytotoxic effects on 16 HBE, Caco2, HuDe and K562 cell lines, and no haemolytic activity. Moreover, both PHEA-EDA-PS(80)-PLA and PHEA-EDA-PLA micelles were able to penetrate into Neuro2a cells and, in the case of PS(80) decorated micelles, to escape from phagocytosis by the J774 A1 macrophages.

Atom-specific identification of adsorbed chiral molecules by photoemission.

The study of chiral adsorbed molecules is important for an analysis of enantioselectivity in heterogeneous catalysis. Here we show that such molecules can be identified through circular dichroism in core-level photoemission arising from the chiral carbon atoms in stereoisomers of 2,3-butanediol molecules adsorbed on Si(100), using circularly polarized x rays. The asymmetry in the carbon 1s intensity excited by right and left circularly polarized light is readily observed, and changes sign with the helicity of the radiation or handedness of the enantiomers; it is absent in the achiral form of the molecule. This observation demonstrates the possibility of determining molecular chirality in the adsorbed phase.