遊佐 真一

To prepare amphiphilic diblock copolymers (M100Pm), a controlled radical polymerization approach was employed, incorporating hydrophilic poly(2-(methacryloyloxy)ethyl phosphorylcholine) (PMPC) with hydrophobic poly(3-methoxypropyl acrylate) (PMPA). The synthesized diblock copolymers feature a PMPC block with a degree of polymerization (DP) of 100 and a PMPA block with DP (=m) values of 171 and 552. The hydrophilic PMPC block exhibits biocompatibility, such as inhibition of platelet and protein adsorption, because of its hydrophilic pendant zwitterionic phosphorylcholine groups that have the same chemical structure as cell membrane surfaces. The PMPA block exhibits hydrophilicity because of its hydrophilic ether groups; however, it is predominantly hydrophobic. In addition, PMPA exhibits biocompatibility. Because both blocks of M100Pm are biocompatible, M100Pm has potential applications in the biomedical field as an innovative material. Because of the hydrophobicity of the PMPA blocks, which were surrounded by hydrophilic PMPC shells, M100Pm aggregated when dispersed in water. M100P171 and M100P552 formed spherical micelles and vesicles, respectively. As the DP of the PMPA block increased, the aggregate size and number also increased. Doxorubicin was successfully encapsulated within the M100Pm aggregates. Given their biocompatible properties, M100Pm aggregates have potential applications in drug delivery systems.

This study investigates the stability and application of trithiocarbonate-based chain transfer agents (CTAs) in reversible addition-fragmentation chain transfer (RAFT) radical polymerization under harsh conditions. We evaluated the stability of 4-cyano-4-(2-carboxyethylthiothioxomethylthio) pentanoic acid (Rtt-17) and 4-cyano-4-(dodecylsulfanylthiocarbonyl) sulfanylpentanoic acid (Rtt-05) at 60 °C under basic conditions using 1H NMR and UV-vis absorption spectra, showing that Rtt-05 is more stable than Rtt-17. The greater stability of Rtt-05 is attributed to the hydrophobic dodecyl group, which allows it to form micelles in water, thereby protecting the trithiocarbonate group from the surrounding aqueous phase. In contrast, hydrophilic Rtt-17, without long alkyl chains, cannot form micelles in water. Following the stability assessment, Rtt-17 and Rtt-05 were employed for RAFT polymerization of hydrophilic monomers, such as N,N-dimethylacrylamide (DMA) and 2-(methacryloyloxy)ethyl phosphorylcholine (MPC). DMA can dissolve in both water and organic solvents, and MPC can dissolve in water and polar solvents. Both CTAs successfully controlled the polymerization of DMA, producing polymers with narrow molecular weight distributions (Mw/Mn) less than 1.2. Also, Rtt-17 demonstrated effective control of MPC polymerization, yielding Mw/Mn values of around 1.2. However, during the polymerization of MPC, Rtt-05 failed to maintain control, resulting in a broad Mw/Mn (≥1.9). The inability of Rtt-05 to control MPC polymerization is due to the formation of micelles, which disrupts the interaction between the hydrophilic MPC propagating radicals and the trithiocarbonate group in the hydrophobic core of Rtt-05 micelles. The findings provide critical insights into designing CTAs for specific applications, particularly for biomedical and industrial uses of hydrophilic polymers, highlighting the potential for precise molecular weight control and tailored polymer properties.

Extracellular vesicles (EVs) have been widely recognized as a heterogeneous group of membrane-coated submicrometer particles released by different types of cells, including stem cells (SCs). Due to their ability to harbor and transfer bioactive cargo into the recipient cells, EVs have been reported as important paracrine factors involved in the regulation of a variety of biological processes. Growing data demonstrate that EVs may serve as potential next-generation cell-free therapeutic factors. However, clinical application of EVs in tissue regeneration requires the development of standardized procedures for their long-term storage, without the loss of structural integrity and biological activity. In the current study, we developed a procedure of EV cryoprotection based on coating them with ultrathin polyelectrolyte bilayer consisting of cationic poly(ethylene glycol)-block- poly(3-(methacryloylamino)propyl)trimethylammonium chloride) (PEGn-b-PMAPTACm) and anionic of poly(2-acrylamido-2-methylpropanesulfonic acid) (PAMPS). Based on the nanoparticle tracking analysis, high-resolution flow cytometry, and mass spectrometry, we studied the vesicle integrity following single- or multiple freezing-thawing cycles and long-term storage. Additionally, we evaluated the effect of cryopreservation on the EVs functional activity in vitro. Obtained data indicate that coating with polyelectrolytes improves the structural integrity of EVs and preserves their biological activity in vitro. Additionally, proteomic analysis confirmed the effect of particle stabilization, as well as an enrichment in EV proteins in samples cryopreserved in the presence of tested polymers. Taking together, our study indicates that the application of polyelectrolytes may be a novel, effective way of facilitating long-term storage of EV preparations for their further use in the biomedical applications.