The immobilization of poly(N-isopropylacrylamide)
(PNIPAAm) on chitosanmembranes was performed in
order to render membranes with thermo-responsive surface
properties. The aim was to create membranes suitable for cell
culture and in which confluent cell sheets can be recovered by
simply lowering the temperature. The chitosan membranes
were immersed in a solution of the monomer that was
polymerized via radical initiation. The composition of the
polymerization reaction solvent, which was a mixture of a
chitosan non-solvent (isopropanol) and a solvent (water),
provided a tight control over the chitosan membranes
swelling capability. The different swelling ratio, obtained
at different solvent composition of the reaction mixture,
drives simultaneously the monomer solubility and diffusion
into the polymeric matrix, the polymerization reaction rate,
as well as the eventual chain transfer to the side substituents
of the pyranosyl groups of chitosan. A combined analysis of
the modified membranes chemistry by proton nuclear magnetic
resonance (1H-NMR), Fourier transform spectroscopy
with attenuated total reflection (FTIR-ATR) and X-ray
photoelectron spectroscopy (XPS) showed that it was possible
to control the chitosan modification yield and depth in the
solvent composition range between 75% and 100% of isopropanol.
Plasma treatment was also applied to the original
chitosan membranes in order to improve cell adhesion and
proliferation. Chitosan membranes, which had been previously
subjected to oxygen plasma treatment, were then modified by
means of the previously describedmethodology. A human fetal
lung fibroblast cell line was cultured until confluence on the plasma-treated thermo-responsive chitosan membranes and
cell sheets were harvested lowering the temperature.Contract grant sponsor: European NoE EXPERTISSUESContract grant number: NMP3-CT-2004-500283Contract grant sponsor: European UnionContract grant number: NMP3-CT-2003-50575
