Kontrollierbare Zeitverzögerung beim Aufplatzen von oxidationsempfindlichen, mittels PISA synthetisierten Polymersomen

Reaktive Polymersomen sind ein vielseitiges künstliches Nanotransportsystem, das eine Freisetzung als Reaktion auf einen bestimmten Stimulus ermöglichen kann. Die vorgestellten oxidationsempfindlichen Polymersomen zeigen einen zeitlich verzögerten Freisetzungsmechanismus in einer oxidativen Umgebung, der durch Anpassung der Membrandicke oder partielle Voroxidation variierbar ist. Diese polymeren Vesikel werden mittels PISA hergestellt, wodurch eine direkte, effektive In‐situ‐Einkapselung von Molekülen ermöglicht wird, wie z. B. für Farbstoffe und Enzyme gezeigt wurde. Kinetische Studien ergaben, dass ein kritischer Oxidationsgrad die Destabilisierung der Membran bewirkt, während vorab keine Freisetzung der Ladung erfolgt. Die Einkapselung von Glukoseoxidase verwandelt diese Polymersomen direkt in glukoseempfindliche Vesikel, da kleine Moleküle, wie Zucker, ihre Membran passiv durchdringen können. Dank der einfachen Herstellung bieten die Polymersomen eine vielseitige Plattform für den Einschluss und die Freisetzung von Molekülen nach einer genau einstellbaren Zeitspanne in Gegenwart spezifischer Verbindungen wie H 2 O 2 oder Glukose

ROS-Sensitive Polymer Micelles for Selective Degradation in Primary Human Monocytes from Patients with Active IBD

Inflammatory bowel disease (IBD) is characterized by increased levels of reactive oxygen species (ROS) in inflamed areas of the gastrointestinal tract and in circulating immune cells, providing novel opportunities for targeted drug delivery. In the recent experiments, oxidation-responsive polymeric nanostructures selectively degrade in the presence of H2O2. Based on these results, it is hypothesized that such degradation process can be triggered in a similar way by the incubation with stimulated monocytes isolated from patients with IBD. A first indication is given by a significant correlation between excessive ROS and degradation of micelles in monocytes isolated from healthy individuals after phorbol 12-myristate 13-acetate (PMA) stimulation. But even if the ROS-sensitive micelles are incubated with nonstimulated monocytes from patients with active IBD, a spontaneous degradation is observed in contrast to micelles incubated with monocytes from healthy donors. The findings indicate that the thioether-based micelles are indeed promising for selective drug release in the presence of activated immune cells

Poly(2-acrylamidoglycolic acid) (PAGA): Controlled Polymerization Using RAFT and Chelation of Metal Cations

Polymer–metal hybrids are interesting materials in general and serve as precursors for a wide range of possible applications. Herein, we present the controlled radical polymerization of 2-acrylamidoglycolic acid (AGA), a polyelectrolyte capable of chelating various metals, using reversible addition–fragmentation chain transfer (RAFT) polymerization. Polymerization kinetics and behavior in aqueous solution were investigated for PAGA homopolymers, and we further show that double hydrophilic poly­(N-acryloyl­morpholine)-block-PAGA (PNAM-b-PAGA) or poly­(ethylene oxide)-block-PAGA (PEO-b-PAGA) block copolymers with varying weight fractions of PAGA can be prepared. Upon addition of different metal cations, these block copolymers form wormlike and spherical hybrid assemblies in aqueous media. The aggregates react reversibly to changes in pH, and their size and shape are influenced by the PAGA/metal ratio, the overall PAGA weight fraction, the type of metal cation, and the block copolymer concentration

Predictive Strength of Photophysical Measurements for in Vitro Photobiological Activity in a Series of Ru(II) Polypyridyl Complexes Derived from π-Extended Ligands

This study investigates the correlation between photocytotoxicity and the prolonged excited-state lifetimes exhibited by certain Ru­(II) polypyridyl photosensitizers comprised of π-expansive ligands. The eight metal complexes selected for this study differ markedly in their triplet state configurations and lifetimes. Human melanoma SKMEL28 and human leukemia HL60 cells were used as in vitro models to test photocytotoxicity induced by the compounds when activated by either broadband visible or monochromatic red light. The photocytotoxicities of the metal complexes investigated varied over 2 orders of magnitude and were positively correlated with their excited-state lifetimes. The complexes with the longest excited-state lifetimes, contributed by low-lying 3IL states, were the most phototoxic toward cancer cells under all conditions