Extracellular matrix absorption properties of negative ion-implanted polystyrene, polydimethylsiloxane and poly-lactic acid

Absorption properties of extracellular matrix (ECM) were investigated for carbon negative-ion-implanted polymers of polystyrene (PS), polydimethylsiloxane (PDMS) and poly-lactic acid (PLA) to estimate cell attachment properties of the modified surface without cell culture. Carbon negative ions were implanted to these polymers at 10 keV with a dose of 1014–1016 ions/cm2. Implanted samples were dipped in a culture medium including serum for 2 h at 37 °C. After the samples were rinsed with phosphate-buffered saline (PBS) and with pure water and then dried, nitrogen atoms absorbed on the surface were investigated by XPS. The molecular structure of many kinds of extracellular matrix proteins contains nitrogen atoms; polymers of PS, PDMS and PLA do not include nitrogen. Therefore, we can evaluate the absorption properties of ECM by the nitrogen atoms absorbed on the surface. The nitrogen content increased after ion implantation for these polymers: from 5.5 to 8% for PS; from 1 to 5% for PDMS; and from 6 to 8.3% PLA. The contact angle for C-implanted PS and PDMS decreased with increasing ion dose, and corresponded well with the absorption properties of the extracellular matrix. However, the contact angle for PLA did not significantly change after ion implantation. Thus, the absorption properties of ECM represent another measure for the estimation of cell-attachment properties.