than cross to the hydrophobic groups.[56] A similar study was performed by Healy's

group using human bone-derived cells (HBDC) and showed the same results.[57] Another

study by Britland et al., examined the effect of topography in combination with surface

patterning. This paper examined quite a few of the relevant topics with a few simple

experiments, although their choice of cells (BHK) does not give as much useful

information for the future. They superimposed tracks of aminosilanes orthogonal to the

ridges and grooves and showed that for shallow grooves (0.1 im to 0.5 pm), the cells

aligned almost exclusively with the chemical patterning, but as the grooves go deeper up

to 6 rm and closer together (5 .im), alignment to both the texture and the chemistry was

seen.1581 By comparing these results with the studies on topographical patterning and

chemical patterning, it is apparent that there are critical levels for each system, in which

topography and chemistry contribute differently to contact guidance.

 The use of silicones in the micropatteming of surfaces has also become quite

popular.[59-63] Essentially, textured polydimethylsiloxane (PDMS) substrates are formed

using the microfabrication techniques mentioned before. These substrates are then used

as stamps or stencils to either directly apply surface treatments such as proteins to another

substrate in an organized fashion, or to act as a mask allowing for microfluidics within

channels in the silicone to pattern the surface.[59] Many times the silicone itself is the

substrate that is used for cell studies. Whitesides' group has demonstrated that by

selectively adsorbing adhesive molecules in the form of fibronectin to the bottom of pits

or wells in the surface, and by keeping a non-adhesive protein like albumin on the surface

above the wells, endothelial cells will adhere only to the bottom of the wells where the

fibronectin is adsorbed.[64] They have also shown that through the use of microcontact