Labelling of a polypeptide conjugate binder for the C-reactive protein with 68Ga for PET imaging
(English)Manuscript (preprint) (Other academic)
A polypeptide conjugate that binds the C-reactive protein (CRP) with high affinity and specificity in human serum has been labelled with the short-lived radionuclide 68Ga (t1/2 = 68 min) for PET imaging. The binder molecule was formed by conjugating phosphocholine to the side chain of a lysine residue of a 42-residue designed polypeptide via an aliphatic spacer. For radiolabelling, a DOTA group was covalently attached to the polypeptide via a PEG spacer linked to the side chain of a Cys residue. The affinity of the binder for CRP is due to the interactions between CRP and the phosphocholine group as well as between CRP and the polypeptide scaffold itself. The affinity for CRP of the polypeptide conjugate was not affected by the incorporation of the DOTA and the dissociation constant was shown by fluorescence titration to be in the low nM range. Life times of polypeptide conjugates in human serum have been shown to depend on the level of incorporation of residues that are not recognized by proteases and thus to be tunable by design. The apparent half life of the polypeptide scaffold without conjugated groups was 10–20 min at 37 °C in human serum whereas the half-life of the labelled CRP binder was more than 24 h under the same conditions. The molecular versatility of peptides and peptide conjugates has therefore been shown to make them excellent carriers of multiple functions for in vivo applications, as illustrated here by the combination of molecular recognition with short-lived radioisotopes for PET imaging.
IdentifiersURN: urn:nbn:se:uu:diva-108591OAI: oai:DiVA.org:uu-108591DiVA: diva2:271583