W. Richard Bowen and Nidal Hilal 4

202 7. MICRO/NANOENgINEERINg ANd AFM FOR CELLULAR SENSINg
(and silanes) have found which exhibit the lowest protein physisorption
(and hence block cell adhesion) [26–28]. These SAMs can therefore be
used to form a non-adhesive background. By the integration of specific
adhesion ligands into these patterns, defined spatial distribution of the
ligands can be formed, as shown in Figure 7.3(a). Here, a pattern of fluorescently
labelled fibronectin on a PEG-passivated surface was prepared
by photolithography. Figure 7.3(b) demonstrates that fibroblasts specifically
attach and proliferate in the adhesive islands.
Cellular interactions in vivo are largely varied. Different types of cells
are juxtaposed in the ECM and each secretes different cues at different
times. Thus, cells are exposed to temporally spatially regulated concentrations
or dynamically changing gradients of adhesive cues (e.g. due
to diffusion of soluble molecules emanating from particular cells). With
surface engineering being able to tune spatial distances and pattern sizes,
micropatterning provides a convenient way to study how cells sense
the spatial distribution of adhesive cues. A study of cells on a micropattern
of ECM ligands has discovered that the amount of integrin does not
always determine cell life or death, but instead this is often indicated by
the degree of cell spreading and its shape [29]. Surface patterning of different
ligands for two types of cells has also advanced the in vitro study
100 μm
(a)
200 μm
(b)
FIgurE 7.3 Example of surface patterning for the generation of adhesive protein patterns.
(a) Fluorescence-labelled fibronectin patterns on a glass substrate generated using
photolithography. (b) 3T3 fibroblast specifically attached and growing on the collagen patterns
but not on the PEG surface between the patterns.