Future recombinant binding tools may avoid antibodies, and use diversified libraries based on small and versatile protein scaffolds, for example the DARPins (Designed Ankyrin Repeat Proteins).  DARPins are single-chain, monodisperse, and non-immunogenic, and can be made rapidly and cheaply in bacteria in many formats.  They can also be expressed in and on cells as non-aggregating fusion proteins with tunable valencies, which opens a wide range of previously inaccessible approaches in cell biology and biochemistry.