Versatility of thermosensitive particles

Poly(N-isopropylacrylamide) (PNIPAM) particles are highly swollen below the transition temperature in water so that they become very soft and hydrophilic, but collapsed above the transition temperature to become hard and hydrophobic. Such changes bring about the discontinuous temperature dependence of adsorbability of protein, activity of immobilized enzyme, cell activating ability of the particles. The transition temperature of PNIPAM was changed by binding something to the chain end and this property was used to control the enzyme activity with temperature. Sudden change in the topology of the particle surface by quick temperature change gave excess stimulus to cells when the change was transmitted straightly to the cells.