Lipid vesicles are commonly used as model systems for biological cell membranes but they also have engineering applications as soft, technological containers. We study the formation of superstructures of vesicles with single-stranded DNA (ssDNA) anchored to their outer monolayers. Heteroaggregation is observed between vesicles decorated with ssDNA of a given sequence and vesicles decorated with the complimentary strand. We investigate how the growth behaviour of these vesicle assemblies is affected by several variables including vesicle concentration, vesicle charge and the average number of ssDNAs per vesicle. Three regimes of aggregation behaviour are observed: no aggregation, stable cluster sizes and continuous aggregation. The growth kinetics is determined by the collision rate of the vesicles in solution and the probability that a binding event will occur during a collision. The binding of short DNA oligonucleotides is thermally reversible: repeated assembly and disassembly of the vesicle aggregates can be induced by cycling in temperature. DNA binding is observed to be thermodynamically more stable when anchored to the vesicles than in bulk solution; we propose that this is due to the enhanced local concentration of DNA and a reduction in conformational entropy due to being anchored to the membrane surface. We also demonstrate that this assembly technique is applicable to vesicles over a wide range of length-scales from vesicle populations with an average diameter of approximately 80nm to giant vesicles with diameters greater than 5µm.

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