The present invention pertains to the use of paranemic crossover motifs for RNA self-assembly, and the use of those self-assembled complexes to carry out analytical methods, and as a basis for the creation of sensors. The invention includes RNA monomeric units comprising an RNA having a binding domain that is adapted to self-assemble paranemically so as to form an RNA complex with another RNA, the binding domain of the RNA monomeric unit comprising an aptameric portion bound to a fluorophore. The invention also includes RNA complexes comprising a target RNA molecule and at least one of these monomeric units which self-assemble paranemically so as to form the RNA complex comprising an aptameric portion. The invention also includes derivatives of these complexes including aptamers, and analytical methods and devices using same.