Molecular imaging of a micropatterned biological ligand on an activated polymer surface

We report here molecular characterization of a new method derived from reac tive microcontact printing microstamping on an activated polymer surface (M APS)-which enables biological ligands and proteins to be patterned on a pol ymer surface with a spatial resolution of at least 5 mu m and good reproduc ibility. MAPS is a multistep procedure: first, the surface of a polymer is modified, in one or more steps, to introduce a reactive group of interest. In a subsequent step, an elastomeric stamp, inked with a biological ligand containing a complementary terminal reactive group, is brought into contact with the activated surface of the polymer. This results in spatially resol ved transfer and coupling of the biological ligand to the reactive surface of the polymer. We used MAPS to pattern biotin on carboxylic acid derivatiz ed poly(ethylene terephthalate) (PET), and subsequently with streptavidin, mediated by the high affinity streptavidin-biotin interaction. X-ray photoe lectron spectroscopy of biotin-derivatized PET showed that approximately on e in five PET repeat units in the top 50-100 Angstrom were functionalized w ith biotin. Time-of-flight secondary ion mass spectrometry (TOF-SIMS) sugge sted an increased concentration of PET oligomers in the top 10 Angstrom due to chain scission during modification and clearly identified the derivatiz ation of PET with biotin. TOF-SIMS imaging mapped biotin and streptavidin t o the stamped regions. TOF-SIMS also imaged the spatial distribution of res idual reagents from the multistep derivatization in MAPS, such as pentafluo rophenol, Tween 20 surfactant, as well as poly(dimethylsiloxane) (PDMS), wh ich was transferred from the elastomeric PDMS stamp to the surface during M APS.