Immunioassay systems based on immunoliposomes consisting of genetically engineered single-chain antibody

摘要

The signle-chain antibody against 2-phenyloxazonlone was modified with lipid molecules at its aminoperminus by genetic engineering.The engineered lipid-tagged antibody molecules were incorporated into liposomes consisting of phosphatidylcholine,and several kinds of immunoassay systems were ocnstructed through the use of the immunoliposomes.The first one was based on fluoroimmunoassay.A competitive fluoroimmunoassay for caproic acid conjugate of 2-phenyloxazolone as a model antigent was performed with the calboxyfluoresceine-encapsulated immunoliposomes.Antigen could be determined in the concentration range from 10~-7 to 10~-9 M.The other system was based on quartz crystal microbalance (QCM).The immunoliposomes were reacted to hapten-immobilized surface of a crystal plate with various concentration of soluble hapten molecules.The frequency change was observed by injectionof the mixture of the immunoliposomes and haptens in a concentration dependent manner.In this competitive QCM assay,antigen could be measured in the concentration reange from 10~-5 to 10~-8M.Furthermore,direct observation of the immunoliposomes on hapten-coated solid-surface by atomic force microscopy (AFM) was also performed in this study.