Crosslinked Poly(N-Isopropylacrylamide)-Based Microfibers as Cell Manipulation Materials with Prompt Cell Detachment.

Stimuli-responsive smart materials are a key to the realization of next-generation medical technologies. Among them, the temperature-responsive polymer poly(N-isopropylacrylamide) (PNIPAAm) is attracting particular attention because it is easy to use in physiological conditions. PNIPAAm-grafted surfaces can undergo temperature-modulated cell adhesion and detachment without proteolytic enzymes, and can be used as cell-separating materials through selective cell adhesion/detachment. However, cell detachment at reduced temperatures is problematic because it takes several hours. A novel thermoresponsive crosslinked microfiber system that can greatly reduce the cell detachment time is introduced in this study. The crosslinked fibers provide temperature-dependent volume change, and enable cell detachment within 10 min of reducing the temperature, which is one-sixth of the time required in previous studies. The prompt cell detachment is thought to arise from a completely new mechanism derived from fiber swelling. This system will make a significant contribution as a novel cell manipulating system for next-generation medical technology.

Temperature-modulated cell-separation column using temperature-responsive cationic copolymer hydrogel-modified silica beads.

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,N'-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.

Recent Advances in Self-Oscillating Polymer Material Systems.

In 1996, we first reported self-oscillating polymer gels exhibiting autonomous swelling-deswelling oscillations driven by the Belousov-Zhabotinsky reaction. In contrast to conventional stimuli-responsive gels, the self-oscillating gel can autonomously and periodically change its volume in a closed solution without any external stimuli. Since the first report, the novel concept of self-oscillating gels has been expanded into various polymer and gel systems. Herein, we summarize recent advances in self-oscillating polymers and gels.

Effect of reaction solvent on the preparation of thermo-responsive stationary phase through a surface initiated atom transfer radical polymerization.

Poly(N-isopropylacrylamide) (PIPAAm) brush grafted silica beads, a thermo-responsive chromatographic stationary phase, were prepared through a surface-initiated atom transfer radical polymerization (ATRP) using 2-propanol, N,N-dimethylformamide (DMF), and water as reaction solvents. The rate of grafting PIPAAm on silica bead surfaces was different and found to be dependent on the reactivity of reaction solvent. Temperature-dependent elution profiles of hydrophobic steroids from the prepared-beads-packed columns were found to be different, although the graft amounts of PIPAAm were similar on silica bead surfaces. Especially, prepared beads using 2-propanol exhibited a higher resolution than those using DMF. Calibration curves using glucose and pullulan suggested that beads prepared using DMF prohibited analytes to diffuse into the pores. On the contrary, beads prepared using 2-propanol allowed analytes to diffuse into the pores. The pore diameter of the prepared beads, measured by N(2) adsorption-desorption measurement, suggested that beads using 2-propanol has relatively larger pore diameter than those using DMF. Thus, the reaction solvent in surfaces-initiated ATRP affected the grafting configuration of PIPAAm on porous silica-bead surfaces, leading to the different separation efficiency of stationary phase for bioactive compounds.