Nonpolar solute cononsolvency in ethanol/water mixtures – Connections to solvent structure

Temperature Controlled Loading and Release of the Anti-Inflammatory Drug Cannabidiol by Smart Microgels

CBD is a promising candidate for treatment of many diseases and plays a major role in the growing trend to produce high-end drugs from natural, renewable resources. In the present work, we demonstrate a way to incorporate the anti-inflammatory drug CBD into smart microgel particles. The copolymer microgels that we chose as carrier systems exhibit a volume phase transition temperature of 39 ∘C, which is just above normal body temperature and makes them ideal candidates for hyperthermia treatment. While a simple loading route of CBD was not successful due to the enormous hydrophobicity of CBD, an alternative route was developed by immersing the microgels in ethanol. Despite the expected loss of thermoresponsive behaviour of the microgel matrix due to the solvent exchange, a temperature-dependent release of CBD was detected by the material, creating an interesting question of interactions between CBD and the microgel particles in ethanol. Furthermore, the method developed for loading of the microgel particles with CBD in ethanol was further improved by a subsequent transfer of the loaded particles into water, which proves to be an even more promising approach due to the successful temperature-dependent release of the drug above the collapse temperature of the microgels.

On-Off of Co-non-solvency for Poly(N-vinylcaprolactam) in Alcohol-Water Mixtures: A Molecular Dynamics Study

Poly(N-vinylcaprolactam) (PVCL) exhibits co-non-solvency in aqueous solutions of 2-propanol but not in methanol. What distinguishes the impact of these two cosolvents on the polymer conformational stability? We report a molecular dynamics simulation study on PVCL 50-mer and monomers dissolved in methanol-water and 2-propanol-water mixtures. We show that the alcohol-concentration dependence of the effective attraction between a pair of PVCL monomers closely resembles the conformational changes in a single PVCL 50-mer as well as the experimentally observed behavior for PVCL chains. We also found that, at the co-non-solvency maximum, the monomer-monomer attraction works over a long-range beyond the solvent-separated distance. Then, we correlate the long-range attraction to the appearance of a dense alcohol concentration accumulated between the monomers. Furthermore, we distinctly demonstrate that the co-non-solvency of PVCL monomers can be switched on/off by artificially tuning the alcohol size while keeping the energetic parameters. Thus, we conclude that the magnitude of the excluded volume effect in alcohol accompanying the gain in translational entropy of the solvent is crucial to the occurrence of PVCL polymer co-non-solvency.