Temperature-Controlled Screening of Catechol Groups in Poly(N-Isopropylacrylamide-co-Dopamine Methacrylamide) for Cell Detachment

Temperature-responsive poly(N-isopropylacrylamide) (PNIPAM) polymers have been studied in many fields due to their "on-off" adjustable properties under temperature stimulation. In this work, the "on-off" mechanism for poly(N-isopropylacrylamide-co-dopamine methacrylamide) (PNIPAM-co-DMA) microgels for cell culture and nonenzymatic cell harvest was explored. Thermoresponsive surfaces were developed on silica wafers using microgels with different DMA contents using a simple spin-coating method. Experiments showed that the microgels showed an "on" state above the lower critical solution temperature (LCST), and PNIPAM-co-DMA (PND) microgels shrank to expose catechol groups for enhanced cell adhesion and proliferation. Conversely, the microgels showed an "off" state below LCST, and the hydrophobic and cell-repellent properties of DMA contributed to the rapid hydration of microgels for accelerated cell disassociation. The developed microgels presented DMA content and distribution-related cell detachment efficiency, with PND (100:0.5) and PND (100:2) showing better results. The failure of cell harvest caused by too much DMA restricted the shrinkage and swelling of microgels due to the strong hydrogen-bonding adhesion of catechol moieties for PND (100:10). Overall, the presented strategy exhibits a wide-ranging utility to construct thermoresponsive surfaces with "on-off" functionalization by introducing catechol chemical monomers.