The Fabrication Of Thermoresponsive Microgel Films For Regulating The Attachment/detachment Behaviors Of Fibroblast Cells

Poly(N-isopropylacrylamide)(PNIPAAm)is a kind of intelligent polymer material in the water or other solvent.In the past few years,many researchers were devoted to the application of cell sheet harvested from the thermoresponsive surface.It could avoid the damages coming from the traditional pancreatic enzyme digestion method of cells.In this work,we aim to harvest the nondestructive cells or cell sheets by using thermoresponsive microgel monolayer film.First,N-isopropylacrylamide(NIPAAm)-based microgels will be prepared by copolymerize with different comonomers through precipitation polymerization.Styrene(St),hydroxyl ethylmethacrylae(HEMA),allyl ammonia(AA)and acrylic acid(AC)are used as comonomers,respectively.Our purpose is to investigate the effect of different kinds of thermoresponsive film on the performance of cell adhesion and detachment behaviors.The results indicate that microgels prepared by incorporating NIPAAm with St or HEMA could regulate the attachment and detachment of cells,the ionic comonomers such as AA and AC copolymerized microgels have no difference on cell adhesion behavior,but it is difficult to make the cells detach at the same condition.When St or HEMA is used as comonomer,the microgels film can regulate the attachment and detachment of cells by temperature stimuli.Based on this study,we further investigated the regulation of poly(N-isopropylacrylamide-co-styrene)(PNIPAAmSt)microgel film on the adhvesion and detachement behaviors of cells.Thermoresponsive films can be conveniently produced by spin-coating or drop-coating of PNIPAAmSt microgel dispersion onto substrates such as glass coverslips,cell culture plates,and flasks.The thickness,stability,and reversibility of the PNIPAAmSt films 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.These PNIPAAmSt microgel films thus open up a convenient interfacial platform for cell and cell sheet harvesting.This technique has broken through the restriction of thickness of PNIPAAmSt coated,and has a good practical prospect.PNIPAAmSt with different content of styrene has a great influence on the detachment behaviors of cells.When St/NIPAAm ratios were above 40 %,the spreading cells were hardly to take off form the surface due to the reduction of thermosensitivity of thermoresponsive films.The resulting microgel dispersions were used to fabricate 2D arrays on the surface of silicon wafers/glass coverslips through dip coating.The gaps between microgel particles can be regulated by changing the withdrawing speed or the concentration of microgel dispersions.But for the 2D ordered structure,the gaps between microgel particles have no obvious effection upon the rate of cell detachment.