In one embodiment, a minibody monomer that binds PSMA is provided. The minibody monomer is encoded by a nucleotide sequence comprising, from N-terminus to C-terminus, an scFv sequence that can bind PSMA, an artificial hinge sequence, and a human IgG CH3 sequence. In another embodiment, a CysDB monomer that binds PSMA is provided. The CysDB monomer may be encoded by a nucleotide sequence comprising, from N-terminus to C-terminus, an scFv sequence that can bind PSMA and a cysteine tail. In other embodiments, methods for diagnosing or treating a cancer associated with PSMA expression in a subject are provided.
