Acquisition of cell-adhesion capability of the surface of crosslinked albumin films irradiated with atmospheric-pressure plasma jets

Abstract

Crosslinked albumin films, to which L929 cells do not attach by nature, acquire the L929-cell-adhesion capability by irradiation of an atmospheric-pressure plasma jet (APPJ) of He gas. The number of attached cells was 2.6 × 104 cells/cm2 after the APPJ irradiation for 180 s, while conventional UV photolithography, which was performed in our previous work, required 2 h to obtain the same order of magnitude of the number of attached cells. The contact angle of samples decreased steeply from 105 to 38° in the first 10 s irradiation, but decreased quite gradually from 38 to 32° with increasing irradiation time from 10 to 180 s. In contrast to the nonlinear variation in the contact angles, the number of attached cells almost linearly increased from 4.5 × 103 to 2.6 × 104 cells/cm2 with increasing treatment time. X-ray photoelectron spectroscopy of the samples indicated that hydrophilic functional groups of C–C=O gradually formed with increasing APPJ irradiation time up to 180 s. These results suggest that the cell-adhesion capability of the crosslinked albumin films is not simply explained by the decrease in contact angle but also by the formation of oxidized functional groups on the surface. The effects of UV and vacuum UV light from APPJ were negligible, which indicates that the formation of oxidized functional groups on the surface is not caused by photon-assisted surface reactions but by reactions involving chemically active species supplied from APPJ.