(437g) Cell Adhesion On Thermosensitive Bio-Inert Materials with a Tunable LCST

Smart, bioactive materials have recently emerged, capable of controlling or influencing biological processes at the molecular level.  Thermoresponsive polymer brushes, such as those composed of poly(N-isopropyl acrylamide) (PNIPAM), allow for the gentle detachment of cells from their culture surface by simply changing the temperature below the lower critical solution temperature (LCST) of the polymer in water.   At temperatures below the LCST, polymer chains are soluble and expand; above the LCST, chains are insoluble and collapse.  Thus, these polymer brushes can switch wettability, between hydrophilic and hydrophobic states, altering cell adhesion. 

In this work, we investigate changes in cellular phenotype in response to culture on thermosensitive bio-inert materials compared to tissue culture plastic (TCP).  We present an alternative to PNIPAM: thermoresponsive polymer brushes with a tunable LCST prepared from random copolymers of 2-(2-methoxyethoxy)ethyl methacrylate (MEO₂MA) and oligo(ethylene glycol) methacrylate (OEGMA).   We hypothesize that the advantage of MEO₂MA-OEGMA thermoresponsive brushes, namely the ability to modulate LCST, can be utilized to control cell adhesion.  Changes in cell morphology and phenotype will be assessed compared to TCP and as a function of LCST. 

To date, mouse fibroblasts were cultured on both thermoresponsive brushes and TCP for 48 hours and then harvested for gene expression analysis using real time RT-PCR.  Genes regulating cell adhesion (FN1, Dusp2, RhoA), inflammation (IL-6), and apoptosis (Bcl-2, trp53) were evaluated.   Cell morphology was assessed using phase contrast microscopy at 0, 6, 18, 24, 30, and 48 hours.  No obvious morphological differences were observed in cells cultured on brushes or TCP.  Gene expression analysis has revealed a small upregulation of all genes on thermobrushes relative to TCP.  Specifically, fold changes ranged between 1-1.6 for all genes; future studies must determine if this change is biologically significant.   

Thermoresponsive polymer brushes are biocompatible and non-cytotoxic.  Bioengineering applications of modulating LCST to control cell adhesion include culture under serum free conditions and growth of cellular monolayers that can be released mechanically.