Synthesis and liposome 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

ω‐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‐[18F]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 [18F]GVIA was 5%. Specific activity of this species was determined to be 1.2 × 105 Ci/mmol. Encapsulation of the tracer in sulfatide containing liposomes, a potential method for enhancing blood–brain penetrance, was accomplished with 40% efficiency. Copyright © 2006 John Wiley & Sons, Ltd.