Biomedical Engineering Reference
In-Depth Information
cell shape, and focal adhesion assembly. In a recent study, microcontact
printing of SAMs was used to generate arrays of circular adhesive islands
surrounded by a nonadhesive background to analyze the role of adhesive
area on adhesion strengthening [99]. The use of micropatterned surfaces
affords precise control over adhesive area, cell spreading/shape, and the pos-
ition and size of focal adhesions, allowing decoupling of cell shape/spreading
from focal adhesion formation. Cells individually adhere to the adhesive is-
lands and maintain a nearly spherical shape, while the cell-substrate adhesive
area conforms to the pattern dimensions (Fig. 7). Adhesion strength ex-
hibits hyperbolic increases with available contact area, reaching a saturation
value equivalent to the strength of unpatterned cells (Fig. 8). Moreover, inte-
grin binding and focal adhesion assembly on the engineered adhesive ligand
display nonlinear increases with available contact area, approaching saturat-
ing levels at high adhesive areas (Fig. 8). These results demonstrate precise
control over adhesive interactions in terms of molecular events (integrin
binding and focal adhesion assembly) and functional outcomes (adhesion
strength).
5
Conclusions and Future Prospects
Surface-engineering approaches focusing on controlling cell-adhesive inter-
actions represent promising strategies to engineer cell-biomaterial biomolec-
ular interactions in order to elicit specific cellular responses and enhance
the biological performance of materials in biomedical and biotechnological
applications. While considerable progress has been made in developing sur-
faces that control protein adsorption and substrates that present biomimetic
motifs, next-generation bioadhesive interfaces should consider incorporat-
ing multiple binding motifs that support binding to various integrin and
nonintegrin receptors, gradients in ligand density, nanoscale clustering,
dynamic interfacial properties, and structural as well as mechanical charac-
teristics of the ECM. For example, recent research indicates that materials
with elastic moduli comparable to native tissues and surfaces that direct
ECM deposition and assembly up-regulate cellular activities, including pro-
liferation and differentiation [100, 101]. Successful development of these
bioactive interfaces will rely heavily on the integration of advances in bio-
chemistry, cell biology, synthetic chemistry, and materials science and engin-
eering.
Acknowledgements AJG gratefully acknowledges support from the National Science Foun-
dation, National Institutes of Health, Arthritis Foundation, Whitaker Foundation, and the
Georgia Tech/Emory NSF ERC on Engineering Living Tissues.
 
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