DETERMINATION OF GLUTAMINE AND GLUTAMIC-ACID IN MAMMALIAN-CELL CULTURES USING TETRATHIAFULVALENE MODIFIED ENZYME ELECTRODES

Tetrathiafulvalene (TTF) mediated amperometric enzyme electrodes have been developed for the monitoring of L-glutamine and L-glutamic acid i n growing mammalian cell cultures. The detection of glutamine was acco mplished by a coupled enzyme system comprised of glutaminase plus glut amate oxidase, while the detection of glutamic acid was carried out by a single enzyme, glutamate oxidase. The appropriate enzyme(s) were im moblized on the Triton-X treated surface of tetrathiafulvalene modifie d carbon paste electrodes by adsorption, in conjunction with entrapmen t by an electrochemically deposited copolymer film of 1,3-phenylenedia mine and resorcinol. Operating conditions for the glutamine enzyme ele ctrode were optimized with respect to the amount of enzymes immoblized , pH, temperature and mobile phase flow rate for operation in a flow i njection (FIA) system. When applied to glutamine and glutamic acid mea surements in mammalian cell culture in FIA, the results obtained with enzyme electrodes were in excellent agreement with those determined by enzymatic analysis.