USE OF GENETICALLY-ENGINEERED LIPID-TAGGED ANTIBODY TO GENERATE FUNCTIONAL EUROPIUM CHELATE-LOADED LIPOSOMES - APPLICATION IN FLUOROIMMUNOASSAY

Biosynthetically lipid-tagged single-chain antibody (Laukkanen et al., Protein Eng. 6 (1993) 449; Biochemistry 33 (1994) 11664) has been use d to functionalize europium (Eu3+) chelate-loaded liposomes. The resul ting Eu immunoliposomes displayed specific hapten-binding activity and little non-specific binding in time-resolved fluoroimmunoassay (TR-FI A). No loss of entrapped marker nor of binding activity was observed a fter storage of Eu immunoliposomes for 1 month at 4 degrees C. In comp arison with Eu-labeled free single-chain antibody, Eu immunoliposomes produced a higher signal and provided increased sensitivity in a sandw ich-type immunoassay. These results demonstrate the potential of Eu im munoliposomes as signal-amplifying reagents in TR-FIA.