SAMs switchable surfaces

Mrksich and coworkers [150] demonstrated even more sophisticated switchable surfaces where cells could be sequentially released and reattached. A SAM that... 

FIGURE 12.16 Schematic representation of the electrically switchable surface, (a) The surface is composed by an RGD and EG6-sulfonate mixed SAM and (b) by an RGD and EG6-ammonium mixed SAM. The two portions are able to switch from cell adhering to cell repellent in response to a potential applied. A positive potential of -E0.3 V will determine the attachment of cells in (a) while a negative potential of —0.3 V will determine the adhesion of cells in (b) [220]. 

Like a bulk responsive material, surface of a substrate can be responsive upon electrochemical, photo, temperature, pH, mechanical, or electrical stimuli (Lahann Langer, 2005). Researchers are developing different ways to make these smart surfaces such as self-assembled monolayers (SAMs), polymer brushes, or copolymer coatings. A classic example is a switchable SAM surface in responsive to electric potential, which achieve hydrophobic-hydrophilic transition on a gold substrate. The switchable surfaces provide an idea platform to smdy surface-biological system interactions (Lahann et al., 2003). Polymer brushes and copolymers are more practical avenues to be applied with long-term performance. 

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