We report a procedure for surface modification based on chemical vapor deposition polymerization of
functionalized [2.2]paracyclophanes that is essentially substrate-independent. Poly(p-xylylene-2,3-dicarboxylic anhydride) and poly[p-xylylene carboxylic acid pentafluorophenolester-co-p-xylylene] are
examined as templates for cell patterning. Both reactive coatings are deposited on poly(tetrafluoroethylene),
polyethylene, silicon, gold, stainless steel, and glass and show excellent adhesion when deposited in thin
films (ca. 100 nm) under optimized polymerization conditions. X-ray photoelectron spectroscopy and grazing
angle infrared spectroscopy have been used to confirm chemical homogeneity in both cases. Reactive
coatings are subsequently patterned by microcontact printing of an amino-terminated biotin ligand and
serve as templates for layer-by-layer self-assembly. Streptavidin selectively binds to the biotin-exposing
surface regions and allows surface confinement of a biotin-tethered antibody against α5-integrin. The
specific interaction of this antibody with endothelial cells results in spatially directed deposition of
mammalian cells. Fluorescence microscopy is used to verify accurate self-assembly at each step. Although
both reactive coatings differ in how they chemically bind biomolecules, their ability to support formation
of pattern by microcontact printing is similar.
We have incorporated fluorescent quantum dots (QDs) into polystyrene microspheres using functionalized oligomeric phosphine (OP) ligands. We find that a uniform distribution of quantum dots is loaded inside each polymer bead. Some local close-packing of quantum dots in the beads is attributed to the self-polymerization of the functionalized ligands. The presence of quantum dots disturbs the nucleation and growth processes during the formation of polymer microspheres and results in a wider size distribution of the quantum dot-embedded polystyrene beads than for the control without dots. The change in quantum efficiency of the quantum dots before (approximately 20%) and after (12%) loading into the beads substantiates the protection of oligomeric phosphine ligands yet indicates that the properties of these quantum dots are still affected during processing.
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