Photo-cross-linkable thermoresponsive star polymers designed for control of cell-surface interactions.

Star polymers with thermoresponsive arms, consisting of 2-(2-methoxyethoxy)ethyl methacrylate (MEO(2)MA) and oligo(ethylene glycol) methacrylate with similar to 4 ethylene oxide units (OEOMA(300), M-n = 300), were synthesized via atom transfer radical polymerization (ATRP). 25% of the arms contained benzophenone chain-end functionality at the star periphery. A mixture of linear poly(MEO(2)MA-co-OEOMA(300))-Br macroinitiators without and with benzophenone end-group macroinitiators were (MI and Bzp-MI, respectively) cross-linked with ethylene glycol dimethacrylate to form star polymers. Formation of star polymers was monitored by GPC, and the presence of benzophenone functionality in the stars as confirmed by H-1 NMR. The UV vis spectroscopy revealed that the star polymers exhibit the low critical solution temperature (LCST) at 27 degrees C, slightly lower than LCST of either MI or Bzp-MI. Commercially available tissue culture grade polystyrene surface was modified by depositing a thin film of functionalized stars and UV cross-linking (lambda = 365 nm). The star polymers covalently attached onto surfaces allowed a control of cell shrinkage and attachment in response to temperature changes.