Liposome immunoassay using a spin label, TEMPO choline (4-[N,N-dimethyl-N-(2-hydroxyethyl)]ammonium-2,2,6,6-tetramethylpiperidine-1-oxyl): a new strategy for detecting this spin label using an ion-selective electrode in place of electron spin resonance (ESR)

Abstract

We devised a new method for detecting the spin label, TEMPO choline (4-[N,N-dimethyl-N-(2-hydroxyethyl)]ammonium-2,2,6,6-tetramethylpiperidine-1-oxyl), which is usually applied in liposome immunoassay, using a TEMPO choline-selective electrode instead of the conventional electron spin resonance (ESR) method. TEMPO choline was enclosed in the inner aqueous phase of liposomes, and the release of TEMPO choline from liposomes induced by the complement-mediated immune lysis reaction was monitored by this electrode. The potentiometric method using the TEMPO choline electrode was more effective for monitoring the immunoreaction and more economical than ESR method.

Key Words:

• Liposome immunoassay
• Ion-selective electrode
• TEMPO choline
• Potentiometry
• Electron spin resonance