Description
The surface of solvent cast chitosan membranes was modified using a two-step procedure. Oxygen
plasma treatment was used at the first activation step followed by vinyl monomer graft
polymerization. Two monomers were used in order to compare the influence of different
functional groups on cell adhesion and proliferation; acrylic acid (AA) was used to introduce
carboxyl groups and vinyl sulfonic acid (VSA) was used as a source of sulfonic groups. The
surface chemistry/energy changes were characterized by means of X-ray photoelectron
spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR-ATR), and contact angle
measurements. Additionally, alterations in the surface morphology were investigated by scanning
electron microscopy (SEM). XPS analyses confirmed the polymer grafting on the surface; an S2s
peak appears in the VSA survey spectrum and an O–CLO peak emerges in the C1s high resolution
spectrum after AA grafting. Moreover, contact angle measurements showed an increment in the
values of the surface energy polar and Lewis base components for all treated samples, confirming
the introduction of additional polar groups by the modification processes. FTIR-ATR spectra
showed no significant difference between treated and original materials. These results confirmed
that only the very top (a few angstroms) surface layer, but not the bulk of the material, was
modified. The effect of modification on the adhesion and proliferation of osteoblast-like cells was
studied on a preliminary basis. Direct contact tests were performed using a human osteosarcoma
cell line (SaOs-2). Cell morphology (optical microscopy and SEM) and cell viability (MTS test) were
evaluated for untreated and surface modified membranes. The results revealed that both plasma
treatment, and the presence of sulfonic groups on the surface of chitosan membranes, improve
SaOs-2 adhesion and proliferation when compared to untreated or AA-grafted membranes. This
effect was strongly related to the polar and Lewis basic components of the total surface energy.
; Marques, A. P. 
