Reduced single molecule photobleaching in fumed Langmuir-Blodgett films

An approach for reducing photobleaching of dyes doped into lipid films formed using the Langmuir-Blodgett technique is discussed. Fluorescent lipid analogs are often doped into lipid membranes to characterize microscopic domains present in the films. Dye photobleaching can limit the information from these studies which can be especially problematic for single molecule fluorescence measurements. Here we show that a protective polymer coating grown on the film using a fuming process can reduce dye photobleaching without perturbing the underlying lipid structure. Following the transfer of 1,2-dipalmitoyl-sn- glycero-3-phosphocholine monolayers to a glass substrate using the Langmuir-Blodgett technique, the films are exposed to vapors of ethyl 2-cyanoacrylate. Polymer formation produces a thin protective barrier on the lipid film that reduces photobleaching of the underlying fluorescent lipid analogs. Single molecule orientation measurements reveal that the molecular structure of the underlying monolayer is unaltered by polymer formation, suggesting that this method is a general, nonperturbative technique for the reduction of photobleaching in fluorescence studies of Langmuir-Blodgett films.