Published papers

Copyright © 2019 American Chemical Society. The cell manipulation technique using thermoresponsive polymers is currently attracting much attention for applications in the medical field. To achieve arbitrary and accurate cell control, it is necessary to intensely research fibronectin behavior. A smart surface, which has thermoresponsive wettability and which can adsorb or desorb fibronectin repeatedly without the presence of cells, was fabricated by an electrospinning method. The fabricated coating changed its structure as the temperature was changed, and this transformation could substitute for the pulling force generated by the cytoskeletal contraction of cells. Moreover, a coated quartz crystal microbalance was able to detect the fibronectin behavior as frequency shifts, which could be used in the estimation of the mass shift with the aid of suitable equations. This coating and measurement system can contribute greatly not only to the development in the medical field centered on biomaterial manipulation technologies, but also to the improvement of medical instruments.

© 2019 Elsevier B.V. There is strong demand for cell separation methods that do not decrease cell activity or modify cell surfaces. Here, new temperature-modulated cell-separation columns not requiring cell-surface premodification are described. The columns were packed with temperature-responsive cationic polymer hydrogel-modified silica beads. Poly(N-isopropylacrylamide-co-n-butyl methacrylate-co-N,N-dimethylaminopropyl acrylamide) hydrogels with various cationic moieties were attached to silica-bead surfaces by radical polymerization using N,Nʹ-methylenebisacrylamide as a crosslinking agent. The beads were packed into solid-phase extraction columns, and temperature-dependent cell elution from the columns was found using HL-60 and Jurkat cells. The retention HL-60 and Jurkat cells in columns containing cationic beads at 37 °C was 95.3% to 99.6% and 95.0% to 98.8%, respectively. By contrast, beads without cationic properties exhibited low cell retention (20.6% for HL-60 and 32.5% for Jurkat cells). The cells were mainly retained through both electrostatic and hydrophobic interactions. The retained HL-60 (4.9%) and Jurkat cells (40%) were eluted at 4 °C from the column with a low composition of cationic monomer (DMAPAAm, 1 mol% in copolymer), because the temperature-responsive hydrogels on the beads became hydrophilic, decreasing the hydrophobic interactions between the cells and the beads. A higher number of Jurkat cells than HL-60 cells were eluted because of differences in their electrostatic properties (Jurkat cells: −2.53 mV; HL-60 cells: −20.7 mV). The results indicated that cell retention by the hydrogel-coated beads packed in a solid phase extraction column could be modulated simply by changing the temperature.

© 2019 The Japanese Society for Regenerative Medicine Introduction: Stem cell therapy with mesenchymal stem cells (MSCs)has been widely used in many clinical trials, and therapy with MSC sheets shows promise for patients. However, there are few reports characterizing MSC sheets. In the present study, the properties of MSC sheets derived from bone marrow, adipose tissue, and umbilical cord were evaluated. Methods: Cell sheets were fabricated with MSCs from different tissue origins in temperature-responsive cell culture dishes with and without pre-coating of fetal bovine serum (FBS). MSC adhesion behavior in the culture dish was observed. Secretion of cytokines related to cell proliferation and immune regulation from MSC sheets was investigated by ELISA. The adhesion properties of the MSC sheets were investigated by time-lapse microscopy. Results: Different cell adhesion and proliferation rates in temperature-responsive cell culture dishes were observed among the three types of MSCs. FBS pre-coating of the dishes enhanced cell attachment and proliferation in all cell types. Harvested cell sheets showed high attachment capacity to tissue culture polystyrene dish surfaces. Conclusions: MSC sheets can be fabricated from MSCs from different tissue origins using temperature-responsive cell culture dishes. The fabricated MSC sheets could be useful in cell transplantation therapies by choosing appropriate types of MSCs that secrete therapeutic cytokines for the targeted diseases.

© 2018 Elsevier B.V. Many thermoresponsive surfaces for biomedical applications have been developed using various techniques for modifying substrates with thermoresponsive polymers. In addition, surface-initiated living radical polymerization methods such as atom-transfer radical polymerization (ATRP) and reversible addition–fragmentation chain-transfer (RAFT) polymerization have been developed as nano structure controlled surface modification methods for modifying thermoresponsive polymers to substrates. These polymerization techniques allow the accurate control of polymerization and the formation of densely packed polymer brush structures. The present review article summarizes a variety of thermoresponsive polymer brushes, mainly comprising poly(N-isopropylacrylamide) (PIPAAm), prepared by surface-initiated ATRP and RAFT polymerization. Self-oscillating polymer brushes as new nano-actuators are also discussed.

©2018, The Society of Polymer Science, Japan. Protein drugs and therapeutic cells are among promising current and future therapies for patients. The importance of these proteins and cells has increased in the clinical field, and protein and cell purification methods, without losing their potency or biological activity, are urgently needed. We prepared thermoresponsive polymer brushes as a new protein and cell separation tool because interactions between the polymer brushes and targeted proteins and cells can be modulated by changing the external solution temperature without using other agents that might contaminate these biologics or disrupt their function. Using these new thermoresponsive polymer brushes, a variety of different bio-separations have been performed by simple temperature changes in aqueous solutions. The present review describes the recent achievement in bioseparation using thermoresponsive polymer brushes.

©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.

© 2019 American Chemical Society. L-type amino acid transporter 1 (LAT1) is a transporter that is more highly expressed in cancer cells compared with normal cells. In the present study, liposomes, composed of egg phosphatidylcholine (EPC) and dioleoyl phosphatidylethanolamine, were modified with LAT1-targeting thermoresponsive polymer, l-tyrosine-conjugated poly(N-isopropylacrylamide-co-N,N-dimethylacrylamide) (P(NIPAAm-co-DMAAm)). The cellular uptake of the prepared LAT1-targeting liposomes was evaluated using HeLa cells as a cancer cell model. At temperatures above the polymer's lower critical solution temperature, uptake of the liposomes into cells was observed because the polymer at the liposome surface became hydrophobic and interacted with the cell membrane. Flow cytometry analysis suggested that l-tyrosine-P(NIPAAm-co-DMAAm)-liposomes exhibited markedly increased cellular uptake by HeLa cells compared with that of liposomes not modified with l-tyrosine. This result indicated that cellular uptake of liposomes can be enhanced by the affinity between l-tyrosine and the LAT1 of HeLa cells. The developed functional liposomes, which exhibit both thermoresponsive and LAT1-targeting properties, would be appropriate for temperature-modulated drug delivery and imaging with good targeting ability.