An ultrasensitive chemiluminescence immunosensor for PSA based on the enzyme encapsulated liposome

A highly sensitive chemiluminescence immunosensor for the detection of prostate-specific antigen (PSA) was developed based on a novel amplification procedure with the application of enzyme encapsulated liposome. Horseradish peroxidase (HRP) encapsulated and antibody-modified liposome acts as the carrier of a large number of markers and specific recognition label for the amplified detection of PSA. In the detection of PSA, the analyte was first bound to the specific capture antibody immobilized on the microwell plates, and then sandwiched by the antibody-modified liposomes encapsulating HRP. The encapsulated markers, HRP molecules were released by the lysis of the specifically bound liposomes in the microwell with Triton X-100 solution. Then, the analyte PSA could be determined via the chemiluminescence signal of HRP-catalyzed luminol/peroxide/enhancer system. The “sandwich-type” immunoassay provides the amplification route for the PSA detection in ultratrace levels. The CL emission intensity exhibits dynamic correlation to PSA concentration in the range from 0.74 pg/ml to 0.74 μg/ml with readily achievable detection limit of 0.7 pg/ml.