Dynamics of smooth muscle cell deadhesion from thermosensitive hydroxybutyl chitosan.

Thermoresponsive polymer (TRP) enables the enzyme-free harvesting of cells through an acute increase in surface hydrophilicity of TRP across its lower critical solution temperature (LCST), rendering feasible the generation of polymer-free cell sheets for regenerative medicine applications. To date, the intricate mechanisms of cell deadhesion/detachment on TRP surface remain obscure. Elucidation of such biophysical responses would be valuable for the cell sheet technology. In this study, integrative biophysical techniques are applied to probe the thermal-induced deadhesion kinetics of smooth muscle cell (SMC) on thermoresponsive hydroxybutyl chitosan (HBC29) against different periods of pre-culture time at 37 degrees C. Atomic force microscopy demonstrates that both the surface topography and mechanical property of HBC29 film in water are acutely modulated across its LCST. Firstly, cells show negligible changes in adhesion contact area during low-temperature incubation on unmodified tissue culture polystyrene (TCPS). Secondly, the recession of adhesion contact and retraction of cell body for cells with different pre-culture times are triggered by HBC29 coating on TCPS. Interestingly, the initial rate of reduction in the normalized adhesion contact area of SMC is negatively correlated with the pre-culture time. Thirdly, the degree of cell deformation and average adhesion energy are reducing functions of time only for SMCs with the lowest pre-culture time. In contrast, adhesion energy per cell is a reducing function of time irrespective of the change of pre-culture time. Lastly, the temporal dynamics of cytoskeleton organization and beta-actin/smoothelin-B mRNA expression for SMCs is strongly dependent on the pre-culture time. Overall, this study demonstrates that the thermal-induced deadhesion of SMC on TRP is characterized by the evolution of its contractile phenotypes.