Figure 4.

Comparative effect of adding features to an underlying p-doped silicon surface using individual adhesive elements to enhance HUVEC adhesion. A 5×1 µm² nanowell patterned surface of 100 nm relative well size was used to trap nanoparticles and RGD peptides, thereby creating an ensemble nanotextured surface to better enhance HUVECs adhesion. The study here was under static condition. From the very bottom, the hydrophilic p-doped silicon substratum ((+)Si) promotes more cell attachment than the PMMA surface (P). Meanwhile, when the negatively charged nanoparticles were immobilized randomly on the silicon ((−)beads on (+)Si) and PMMA surfaces ((−)beads on P), there is a slight increase in cell adhesion on (−)beads on (+)Si but not for (−)beads on P. When RGD peptides were passively added on silicon (RGD_on_(+)Si) and PMMA surfaces (RGD on P), we did not see any increase in cell adhesion. We hypothesize that the RGD peptides act as a competitive ligand for adhesion or an inhibitor to binding to RGD sequences in serum-derived matrix proteins. Next, we investigated cells on well patterns (wells), well patterns that trapped nanoparticles ((−)beads in wells), and well patterns that trapped RGD peptides (RGD in wells). After 72 hours, dissimilarities among them were not found but double in the number of cells when compared to (+)Si, (−)beads on (+)Si, and (−)beads on P. When (+)Si, P, wells, and RGD-conjugated nanoparticles were combined to make the ultimate pro-adhesive surface (RGD-(−)beads in wells), cell adhesion was synergistically enhanced by three-fold when compared to on (+)Si, (−)beads on (+)Si, and (−)beads on P at 72 hours. HUVECs/HPF is the number of HUVECs per high power field (HPF) of a 60× microscope.