Cell attachment/detachment behavior on poly(N-isopropylacrylamide)-based microgel films: the effect of microgel structure and swelling ratio

Microgels are cross-linked soft particles with a three-dimensional network structure that are swollen in a good solvent. Poly(N-isopropylacrylamide) (pNIPAAm)-based microgels have attracted great attentions for their temperature responsive property, particularly in recent years, pNIPAAm-based microgel films were utilized as a new kind of thermoresponsive surface to tune cell attachment/detachment behavior via temperature stimuli. However, some results are not consistent, for example, different polymerization conditions may bring out different results even for pure pNIPAAm microgel. This work aims to find out which factor plays the critical role for successful cell detachment on the pNIPAAm-based microgel films. The results unraveled that the structure and swelling ratio of the microgel rather than the film thickness plays a key role on the successful cells detachment, unlike linear pNIPAAm films in which the cells' attach/detach property is only determined by the film thickness. For poly(N-isopropylacrylamide-styrene) microgel film, NIH3T3 cells could only detach when the microgel has a uniform structure and the volume dilatation of the microgel (20/38 A degrees C) is larger than 4.