Programmability of the DNA-mediated self-assembly process: Multi-vesicle assemblies of predefined architecture.

<p>(A) Image overlays of confocal laser scanning fluorescence and differential interference contrast micrographs of merged vesicle populations (VPs). Biotinylated DNA single strands (biotin-ssDNA) that differ in sequence (α, α', β, β', γ, γ') and streptavidin populations that differ in fluorescence labeling (unlabeled (st.), Alexa Fluor® 488 labeled (st.-AF488, pseudocolored green in fluorescence micrographs), Alexa Fluor® 532 labeled (st.-AF532, pseudocolored red in fluorescence micrographs)) were incubated pairwise prior to vesicle decoration resulting in the following streptavidin/biotin-ssDNA combinations decorating the VPs: (A.1) α-st.-AF488: VP1, α'-st.:VP2; (A.2) α-st.-AF532 & β-st.-AF532: VP1, α'-st.-AF488 & γ-st.-AF488: VP2, β'-st. & γ'-st.: VP3. The receptor surface density was reduced to 0.25 mol % biotin labeled PEG phospholipids (cp. 1.0 mol % in experimental setup C). The fluorescence signal accumulates in the contact areas of adjacent and complementary vesicles forming adhesion plaques that indicate stable vesicle-vesicle linkage. (B) Schematic representation of the programmability of the DNA-mediated self-assembly process. The formation of adhesion plaques depends on the complementarity of ssDNA (cp. <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0009886#pone-0009886-g004" target="_blank">Figure 4</a>.C.1) resulting in a sequence depend accumulation of linkers in the contact areas. The depletion of linkers in between the adhesion plaques terminates the self-assembly process. In combination with the ssDNA decoration of the vesicle surface, the self-termination defines the spatial arrangement of multi-vesicle aggregates. Thus, control of the assembly process is inherent to the system resulting either in duplets (A.1) or triplets (A.2) as minimal self-containing structural units. For a discussion of factors causing the low number of such units see text. Scale bars represent 10 µm.