Thermoresponsive microgel films for harvesting cells and cell sheets.

This work reports the formation of thermoresponsive poly(N-isopropylacrylamide-co-styrene) (PNIPAAmSt) microgel films and their use for cell growth and detachment via temperature stimuli. Thermoresponsive surface films can be conveniently produced by spin-coating or drop-coating of PNIPAAmSt microgel dispersions onto substrates such as glass coverslips, cell culture plates, and flasks, making this technique widely accessible. The thickness, stability, and reversibility of the PNIPAAmSt films coated on silicon wafers with respect to temperature switching were examined by spectroscopic ellipsometry (SE) and atomic force microscopy (AFM). The results unraveled the direct link between thermoreversibility and changes in film thickness and surface morphology, showing reversible hydration and dehydration. Under different coating conditions, well-packed microgel monolayers could be utilized for effective cell recovery and harvesting. Furthermore, cell adhesion and detachment processes were reversible and there was no sign of loss of cell viability during repeated surface attachment, growth, and detachment, showing a mild interaction between cells and thermoresponsive surface. More importantly, there was little deterioration of the packing of the thermoresponsive films or any major loss of microgel particles during reuse, indicating their robustness. These PNIPAAmSt microgel films thus open up a convenient interfacial platform for cell and cell sheet harvesting while avoiding the damage of enzymatic cleavage.