Fig. 2
The scheme of aptamer-antibody-based sandwich-type biosensors and aptamer pair-based sandwich-type biosensors; Antibody-aptamer-based sandwich-type biosensor (a), aptamer-antibody-based sandwich-type biosensor (b), aptamer pair-based sandwich-type biosensor (c), aptamer-based sandwich-type biosensor using hands in hands nanostructure (d), FRET-based label free sandwich type biosensors (e)