Figure 4.

Patterning using localized SAM removal and replacement. Schematic representation of a localized SAM replacement approach using borohydride chemistry to remove regions of a preformed SAM. A) The approach involves the following: 1) HS–C₁₁EG₃OH alkanethiolate SAM; 2) apply microfluidic device; 3) flow aq. 0.5m NaBH ₄ through channels to locally remove SAM; 4) locally form a new SAM with a mixture of aqueous HS–C₁₁–EG₃–OH and HS–C₁₁–EG₆–COOH alkanethiolates to create features with varied carboxylic acid densities; 5) covalently conjugate primary amine-bearing peptide to COOH-terminated alkanethiolates. B) Using this approach, biomolecule immobilization was monitored by coupling a fluorescently tagged peptide to patterned SAM containing discrete features with varied mol% HS–C₁₁ –EG₆–COOH alkanethiolate. C) hMSC attachment and growth over 14 days was confined to RGD presenting regions (live hMSCs were stained with calcein AM, green) and D) MSCs attaching to patterned regions presenting varied percentages of RGD exhibited significant differences in cytoskeletal organization (vinculin: green, actin: red, and nuclei: blue). Adapted from ref. [36] with permission. Copyright: The American Chemical Society, 2009.