There is provided a method of forming a multimeric complex having affinity
for a target. The method comprises: obtaining a plurality of
self-assembly molecules, said self-assembly molecules including
complementary self-assembly units such as verotoxin subunit B, each of
which is operatively connected to an interaction domain such as a single
domain antibody specific for the target; and combining said self-assembly
molecules such that at least three said self-assembly units
simultaneously bind to one another so as to permit the single domain
antibodies to bind the target.