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The first use of one-dimensional magnetic resonance imaging (MRI) to provide information on concentration and molecular mobility (as revealed by the spin-spin relaxation time, T2) as a function of depth into cross-linking latex coatings during their film formation is reported. These materials are of interest because they provide hard, chemically resistant coatings and because, being waterborne, they do not release organic solvents into the atmosphere. MRI profiles, with a pixel resolution of 9 µm, are obtained at regular time intervals from a poly(vinyl acetate-co-ethylene) latex dispersion containing a difunctional cross-linker and a photoinitiator. In this complete formulation, MRI reveals that the rate of cross-linking is fastest in the middle regions of the coating. This result is explained by considering the combined effects of light scattering in the turbid latex, the inhibition of the free-radical cross-linking reaction by initial molecular oxygen, and the further ingress of oxygen from the atmosphere. A numerical model, using measured and known parameters, predicts MRI profiles that are in good qualitative agreement with those found experimentally.

Tethered bilayer lipid membranes (tBLMs) on solid supports have substantial advantages as models of artificial cell membranes for such biomedical applications as drug delivery and biosensing. Compared with untethered lipid membranes, tBLMs have more space between substrate and the bilayer and greater stability. The purpose of this work was to use these properties to fabricate and characterize a zwitterionic 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine lipid tBLM containing 2 mol% 1,2-distearoyl-sn-glycero-3-phosphoethanolamine-N-maleimide(poly(ethylene glycol))-2000 (DSPE-PEG2000-NHS) lipid tethers on a 3-aminopropyltrimethoxysilane-modified mesoporous silica substrate. A quartz crystal microbalance with dissipation monitoring was used to monitor the process of vesicle adsorption and tBLM self-assembly, and atomic force microscopy was performed to characterize the structural properties of the tBLM obtained. Whereas tether-containing lipid vesicles ruptured neither spontaneously nor as a result of osmotic shock, introduction of an amphipathic α-helical (AH) peptide induced vesicle rupture and subsequent tBLM formation. Taken together, our findings suggest that the AH peptide is an efficient means of rupturing vesicles of both simple and complex composition, and is, therefore, useful for formation of tBLMs on solid and mesoporous materials for applications in biotechnology.

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