New tagging method expands tool kit for PET radiotracers
Scientists at the U.S. Department of Energy's Brookhaven National Laboratory have devised a method for adding a radioactive tag to formaldehyde, in order to synthesize a new class of PET radiotracers to monitor the movement and interactions of a wide range of chemicals in the human body, according to research published online July 4 in Angewandte Chemie.

“PET is an extremely valuable tool for understanding human physiology,” said Brookhaven chemist and lead researcher Jacob Hooker.

“But many, if not most, molecules people are interested in studying with PET cannot be radiolabeled right now,” Hooker said. “So there is a huge need for basic science to develop new strategies for making radiotracers. Our new method…expands our tool kit of reagents and increases the number and types of compounds we can use to peer into the human body.”

The new method incorporates a radioactive form of the element carbon, such as carbon-11 into the formaldehyde molecule, according to the Upton, N.Y.-based Brookhaven scientists. Carbon-11 atoms emit positrons, which can be tracked by a PET scanner. In many carbon-11 radiotracers, the researches said that radioactive tag is attached to exterior portions of the molecule rather than the carbon chains that make up the backbone of biological molecules.

Since formaldehyde is involved in many chemical reactions that lead to the synthesis of organic, carbon-chain molecules, it has been a natural target for labeling because it can then be used to make other labeled organic compounds that can be administered to humans as radiotracers, according to the researchers.

Several groups have devised ways to label formaldehyde using other methods, but they are not routinely used, Hooker said.

“While new methods often provide proof of principles, they are often not easily adapted by others to label radiotracers, because they require special equipment and reagents not readily available to all PET chemists,” he said. “Our goal in designing a new route to carbon-11-labeled formaldehyde was to make it simple, efficient and very easy to repeat.”