Cell Adhesion As a Function of LCST, Comparing Pnipam to A Novel Thermoresponsive Substrate

Cell adhesion to novel materials is determined by material surface characteristics, protein adsorption, and the cellular phenotypic response, all of which are interrelated.  Thermoresponsive polymer brushes offer a unique culture system whereby cells are released by a simple temperature switch.  PNIPAM, the gold standard for thermoresponsive polymers exhibits a lower critical solution temperature (LCST) of 32°C.  At temperatures below the LCST, polymer chains are soluble and expand; above the LCST, chains are insoluble and collapse.  A novel thermoresponsive substrate prepared from random copolymers of P(MEO₂MA-co-OEGMA) (PMO)  has a distinct advantage over PNIPAM: the ability to tune the LCST to values between 26 and 90°C by varying the co-monomer ratio.  Changes in cell morphology and phenotype were assessed for both thermoresponsive systems compared to TCP and as a function of LCST.  Mouse fibroblasts were cultured on brushes for 48 hours and then harvested for gene expression analysis using real time RT-PCR.  Cell circularity and spreading were evaluated as a function of time to gain understanding of attachment efficiency. After 48 hours, cell circularity was statistically similar in all substrates and spreading was 90%+ despite significant differences at earlier time points.  Gene expression results suggest that phenotype is a function of LCST.