Use of a quartz crystal microbalance to monitor immunoliposome--antigen interaction.

We have used quartz crystal microbalance (QCM)-based real-time biospecific interaction measurement to analyze the binding of immunoliposomes to antigen and examined the use of liposomes as signal-enhancing reagents in competitive QCM immunoassay. For the preparation of immunoliposomes, various amounts of bacterially produced lipid-tagged single-chain antibody against 2-phenyloxazolone were incorporated in phosphatidylcholine liposomes. The immunoliposomes bound specifically to immobilized hapten, and this binding was inhibited by soluble hapten in a concentration-dependent manner. In this competitive assay, antigen could be measured in the concentration range from 10(-5) to 10(-8) M.