Design of Biointerfaces for Regenerative Medicine - Polymers in Nanomedicine - page 170

because the cells were in the medium, outside of the evanescent field. When the
cells approached and landed on the surface (Fig. 1b -2), small, bright spots were
observed. The cells were round with diameters of approximately 10 m m, but the
diameter of the cell membrane visualized in the evanescent field was approximately
2 m m. These spots were difficult to detect by TIRFM with a 10

objective lens.
Once cells adhered to the SAM surface (Fig. 1b -3), bright spots were easily detected
by TIRFM. When cells spread out on the surface (Fig. 1b -4), the bright spots
observed by TIRFM became larger with time. Thus, TIRFM was a useful tool for
investigating cell adhesion. Changes observed in labeled cells could be interpreted
to infer cell behavior at the solid-liquid interface.
TIRFMwas used for time-lapse observations of initial cell adhesion to SAMs with
different surface functionalities (Fig. 2 ). After 10 min of plating a suspension of
human umbilical vein endothelial cells (HUVECs), a few bright spots were observed
on SAMs with COOH and NH 2 functionalities; this indicated cell adherence. The
number of bright spots increased and the spot areas enlarged with incubation time,
indicating that HUVECs adhered and spread well on COOH-SAM and NH 2 -SAM
surfaces. Quantitative analysis of the number of adherent cells and cell adhesion areas

Fig. 2 TIRFM images of HUVEC adhesion behavior on SAMs with four different types of
surface functional groups at the indicated times after first applying the cell suspension. Scale
bar: 200 m m[ 42 ]