Self-assembly, drug encapsulation, and cellular uptake of block and gradient copolymers of 2-methyl-2-oxazine and 2-n-propyl/butyl-2-oxazoline

Self-assembled amphiphilic polymers have been extensively studied for various biomedical applications, as they show advantageous properties for diagnosis and therapy. In this work, we extensively compared amphiphilic copolymers of the hydrophilic monomer 2-methyl-2-oxazine (MeOzi) and the thermoresponsive or hydrophobic monomers 2-propyl-2-oxazoline (PrOx) or 2-butyl-2-oxazoline (BuOx) in both block and gradient monomer distributions. Such a head-to-head comparison between block and gradient copolymers, which has thus far been mostly missing in the available literature, should provide important insight into the differences and similarities between these two architectures. We investigated the properties of our polymers using a wide array of analytical methods, including dynamic light scattering (DLS), small-angle neutron (SANS) and X-ray scattering (SAXS), one-dimensional (1D) and two-dimensional (2D) nuclear magnetic resonance (NMR) spectroscopy, transmission electron microscopy (TEM), drug loading (DL), cellular uptake, and cytotoxicity studies. Most of the studied polymers formed self-assembled nanoparticles, but their properties varied with the monomer ratio, polymer length, and polymer architecture, and these factors could be used to fine-tune the properties of the polymer to meet the demands of the desired application. Both block and gradient copolymers showed similar critical association concentrations and DL properties for the antituberculosis drug rifampicin. Finally, we confirmed that the nanoparticles could be internalized by macrophages, which indicates great potential for the utilization of these nanoparticles in drug delivery

Fluorinated ferrocene moieties as a platform for redox-responsive polymer F-19 MRI theranostics

Fluorine-19 magnetic resonance imaging (F-19 MRI) stands out as a powerful tool for noninvasive diagnostics. In particular, polymer-based F-19 MRI tracers ofler tunable physicochemical properties, including solubility and thermoresponsive-ness, and enhanced F-19 MRI performance. However, these tracers do not detectably respond to redox changes or do so in only one redox state, thereby preventing potential applications to reactive oxygen species (ROS) bioimaging. Herein, we report the first amphiphilic redox-responsive, poly(2-oxazoline)-based polymers bearing fluorinated ferrocene moieties. Their hydrophobicity and redox responsiveness were tailored by changing the monomer ratio and substitution pattern of the fluorinated ferrocene units. Converting the diamagnetic fluorinated ferrocene moieties into paramagnetic ferrocenium markedly changed the chemical shift and relaxation times of the F-19 nuclei distinguishable by F-19 MRI. In turn, the statistical-diblock copolymers formed nanoparticles that disassemble upon oxidation, with no toxicity to cultured cells. Therefore, these polymers may be used to release lipophilic drugs in ROS-rich malignancies

Pharmacokinetics of intramuscularly administered thermoresponsive polymers

Aqueous solutions of some polymers exhibit a lower critical solution temperature (LCST); that is, they form phase-separated aggregates when heated above a threshold temperature. Such polymers found many promising (bio)medical applications, including in situ thermogelling with controlled drug release, polymer-supported radiotherapy (brachytherapy), immunotherapy, and wound dressing, among others. Yet, despite the extensive research on medicinal applications of thermoresponsive polymers, their biodistribution and fate after administration remained unknown. Thus, herein, they studied the pharmacokinetics of four different thermoresponsive polyacrylamides after intramuscular administration in mice. In vivo, these thermoresponsive polymers formed depots that subsequently dissolved with a two-phase kinetics (depot maturation, slow redissolution) with half-lives 2 weeks to 5 months, as depot vitrification prolonged their half-lives. Additionally, the decrease of T-CP of a polymer solution increased the density of the intramuscular depot. Moreover, they detected secondary polymer depots in the kidneys and liver; these secondary depots also followed two-phase kinetics (depot maturation and slow dissolution), with half-lives 8 to 38 days (kidneys) and 15 to 22 days (liver). Overall, these findings may be used to tailor the properties of thermoresponsive polymers to meet the demands of their medicinal applications. Their methods may become a benchmark for future studies of polymer biodistribution