| Abstract
| - We have prepared a chemically anchored monolayer of PEG (poly(ethylene glycol)) and phospholipidmixture (PEG/phospholipid) on a methacryloyl-terminated substrate by in situ photopolymerization. Bothmonoacryloyl phospholipid (acryloyl-PC, 1-palmitoyl-2-[12-(acryloyloxy)dodecanoyl]-sn-glycero-3-phosphocholine) and monoacryloyl PEG (acryloyl-PEG, 12-(acryloyloxy)dodecanoyl-PEG) were synthesized bymodifying phospholipid and PEG with 12-(acryloyloxy)-1-dodecanoic acid and 12-(acryloyloxy)-1-dodecanol,respectively. The surface pressure−area (Π−A) isotherm showed that acryloyl-PEG molecules were stablein the phospholipid monolayer and that they could be evenly inserted into a phospholipid monolayer atthe air/water interface. By adding 10 mol % acryloyl-PEG into phosholipid vesicles, we could produce aPEG/phosholipid monolayer on methacryloyl-terminated substrates using vesicle fusion for 3 h. Then, thispolymerizable PEG/phospholipid monolayer was in situ photopolymerized onto a methacryloyl-terminatedsubstrate with eosin Y/triethanolamine as co-initiators. Optimal vesicle fusion and irradiation conditionwere determined with respect to the vesicle fusion time and duration of irradiation. As confirmed by atomicforce microscopy and X-ray reflectivity studies, the polymerized PEG/phosholipid surface formed a PEG-covered phospholipid monolayer with thicknesses of 3 and 6 nm for the base phospholipid monolayer andthe covering PEG layer, respectively. The chemical anchoring efficiency of polymerized PEG and phospholipidmolecules, which was calculated by the relative carbon ratio of each surface before and after methanolwashing using X-ray photoelectron spectroscopy, was 98%. This polymerized PEG/phosholipid monolayershowed good stability in organic solution due to firm chemical anchoring to a solid surface.
|
