Synthesis and lipsome encapsulation of a novel 18F-conjugate of ω-conotoxin GVIA for the potential imaging of N-type Ca2+ channels in the brain by positron emission tomography

co-Conotoxin GVIA is a potent, irreversible antagonist of N-type voltage gated Ca2+ channels. A radiofluorinated analogue of GVIA could be useful in assessing regional synaptic density of the brain, in vivo, using positron emission tomography. N-hydroxy succinimidyl 4-[F-18]fluorobenzoate was employed to site-specifically label GVIA, preserving native binding affinity. The tracer was characterized with MALDI-TOF mass spectrometry and colorimetric protein assay. Radiochemical decay-corrected yield of the lysine-24 labeled analogue of [F-18]GVIA was 5%. Specific activity of this species was determined to be 1.2 x 10(5) Ci/mmol. Encapsulation of the tracer in sulfatide containing liposomes, a potential method for enhancing blood-brain penetrance, was accomplished with 40% efficiency. Copyright (c) 2006 John Wiley & Sons, Ltd.