Recent advances in drug delivery applications of aqueous two-phase systems.

Aqueous two-phase systems (ATPSs) are liquid-liquid equilibria between two aqueous phases that usually contain over 70% water content each, which results in a nontoxic organic solvent-free environment for biological compounds and biomolecules. ATPSs have attracted significant interest in applications for formulating carriers (microparticles, nanoparticles, hydrogels, and polymersomes) which can be prepared using the spontaneous phase separation of ATPSs as a driving force, and loaded with a wide range of bioactive materials, including small molecule drugs, proteins, and cells, for delivery applications. This review provides a detailed analysis of various ATPSs, including strategies employed for particle formation, polymerization of droplets in ATPSs, phase-guided block copolymer assemblies, and stimulus-responsive carriers. Processes for loading various bioactive payloads are discussed, and applications of these systems for drug delivery are summarized and discussed.

Catalyst Regeneration via Chemical Oxidation Enables Long-Term Electrochemical Carbon Dioxide Reduction.

Electrochemical CO2 reduction (ECR) with industrially relevant current densities, high product selectivity, and long-term stability has been a long-sought goal. Unfortunately, copper (Cu) catalysts for producing valuable multicarbon (C2+) products undergo structural and morphological changes under ECR conditions, especially at high current densities, resulting in a rapid decrease in product selectivity. Herein, we report a catalyst regeneration strategy, one that employs an electrolysis method comprising alternating "on" and "off" operating regimes, to increase the operating stability of a Cu catalyst. We find that it increases operating lifetime many times, maintaining ethylene selectivity ≥40% for at least 200 h of electrolysis in neutral pH media at a current density of 150 mA cm-2 using a flow cell. We also demonstrate ECR to ethylene at a current density of 1 A cm-2 with ethylene selectivity ≥40% using a three-dimensional Cu gas diffusion electrode, finding that this system under these conditions is rendered stable for greater than 36 h. This work illustrates that Cu-based catalysts, once they have entered into the state conventionally considered to possess degraded catalytic activity, may be recovered to deliver high C2+ selectivity. We present evidence that the combination of short periods of electrolysis, which minimizes the morphological changes during "on" segments, with the progressive chemical oxidation of Cu atoms on the catalyst surface during "off" segments, united with the added effects of washing the accumulated salt and decreasing the catholyte temperature prolong together the catalyst's operating lifetime.