Structure-relaxivity relationships of serum albumin targeted MRI probes based on a single amino acid Gd complex

The Gd(III) complex of DO3A-N-α-aminopropionate, Gd(DOTAla), was used to generate a small library of putative MRI probes targeted to human serum albumin (HSA). Ten compounds were synthesized via multistep organic synthesis, and the corresponding Gd complexes were investigated for their affinity to HSA, lipophilicity, and relaxivity in the absence and presence of HSA. Negative charge and moderate lipophilicity correlate with increased HSA affinity and relaxivity.