A hollow fiber membrane based system for the rapid synthesis of labelled formaldehyde

An improved enzymatic method has been developed for the synthesis of labeled formaldehyde. C-11 labeled formaldehyde is a key intermediate in the synthesis of several radiopharmaceuticals e.g. 11C thymidine. The authors' approach was based on the use of enzymes attached to bioactive microporous membranes. Alcohol oxidase and catalase were covalently attached to a hollow fiber membrane (HFM) support. Alcohol oxidase catalyzes the reaction of methanol and oxygen to formaldehyde and hydrogen peroxide. Catalase breaks down hydrogen peroxide to water and oxygen thus serving as an oxygen regenerator for the system. The enzyme linked HFM was able to generate 0.5 umole of formaldehyde/min. Enzyme immobilization to a HFM obviates the need for separation of the enzyme from the reaction mixture, while the ability to supply reactants to the immobilized enzyme by convective flow of the solution into and through the microporous support membrane eliminates diffusional resistances that would otherwise slow the reaction kinetics. This system can reduce the total synthesis and purification time, an important factor considering the 20.4 min half-life of Carbon-11