This study aimed to develop methods to perform F-18 radiolabeling with [18F]SFB of four specifically engineered novel bispecific antibody ligands, synthesized by fusion of fragments of the TfR with either full-size IgG antibodies of Aβ or tau, or with their respective single-chain variable antibody fragments (scFv of Aβ or tau) (Figure 1), to evaluate their feasibility as PET radioligands for the in vivo imaging of Aβ protofibrils and tau protein in the brains of AD mice. Here, MAPT is linked to Alzheimer disease.