And Liposome Assembly

The layer-by-layer assembly by alternate adsorption of oppositely charged molecules was applicable for multipolar dyes with symmetric charges possessing conjugated rings and other hydrophobic fragments [48-51]. Hydrophobic fragments probably enhance dye stacking. Interestingly, the dye/polyion bilayer has the same thickness in a wide range of dye concentrations. For Congo Red/PDDA films, the bilayer thickness was 1.5 nm for dye concentrations from 0.01 up to 10 mg/mL, that is, below and above the critical micelle concentration (CMC) of the dye.

The characteristic feature of the assembly of some dye multilayers was greater than the monolayer adsorption at the dye adsorption cycle followed by a depletion of the material during the following linear polyion adsorption step. In this process, we have substantial nonspecific adsorption at the dye adsorption step, and then the removal of nonspecific bond material by complexation with an oppositely charged polyion (at the next assembly step). The graph of the film mass against the number of adsorption steps, such as a growth mode, looks like "a large step up followed by a small step down" [46, 50]. A similar growth mode was observed for protein/polyion and nanoparticle/polyion assemblies, especially with a short intermediate sample washing time [58, 77].

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