Published papers

©2018, The Society of Polymer Science, Japan. Drug delivery system (DDS) is a technology that controls sustained release of medicines in the body and localized delivery to diseased tissues. Therefore, it is possible to keep the concentration of medicine at therapeutically effective concentrations for a long time and to reduce side effects. We have achieved controlled intracellular uptake, and release of medicines by nanocarriers modified with stimuli-responsive polymers based on poly(N-isopropylacrylamide), which undergoes a reversible phase transition in response to external temperature stimulation. In this article, we introduce our recent research on the design of temperature- and pH-responsive polymers, which enables selective intracellular uptake with external stimulation, and applications to DDS of an anti-tumor agent and siRNA by micelle and liposomes modified with those polymers.

© 2018 Elsevier B.V. Recently, the importance of biopharmaceuticals in medical treatments has been increasing, and effective protein purification methods are strongly required for their production. In the present study, a temperature-responsive solid-phase extraction (SPE) column was developed for the purification of proteins without affecting their bioactivity. A temperature-responsive polymer hydrogel-modified stationary phase was prepared by coating aminopropyl silica beads (average diameter, 40–64 μm) with poly(N-isopropylacrylamide) (PNIPAAm)-based thermoresponsive hydrogels. n-Butyl methacrylate and acrylic acid were copolymerized with PNIPAAm as hydrophobic and anionic monomers, respectively. Using these temperature-responsive SPE columns, targeted proteins were retained on the thermoresponsive hydrogel at 40 °C through hydrophobic and electrostatic interactions. After the temperature was reduced from 40 °C to 4 °C, the retained proteins were successfully eluted from the column. Using the temperature-responsive SPE system, lysozyme was successfully separated from ovalbumin without any loss in bioactivity (99.7 ± 0.1%). Rituximab, a monoclonal antibody, was also purified from BSA or hybridoma cell culture medium using the prepared SPE column. Denaturation of rituximab was not observed in the rituximab fraction eluted from the SPE column. These results demonstrate that temperature-responsive polymer-based SPE can be applied in biomedical purifications, while maintaining the biological activity of the proteins.