A two-step fluorinase enzyme mediated F-18 labelling of an RGD peptide for positron emission tomography

A two-step radiolabelling protocol of a cancer relevant cRGD peptide is described where the fluorinase enzyme is used to catalyse a transhalogenation reaction to generate [F-18]-5'-fluoro-5'-deoxy-2-ethynyladenosine, [F-18]FDEA, followed by a 'click' reaction to an azide tethered cRGD peptide. This protocol offers efficient radiolabelling of a biologically relevant peptide construct in water at pH 7.8, 37 degrees C in 2 hours, which was metabolically stable in rats and retained high affinity for alpha(V)beta(3) integrin.