A Laser Magnet Immunoassay With Ultra High Sensitivity For Direct Antigen Detection

A new high sensitive diagnostic system, named "laser magnet immunoassay" (LMIA) and which uses a magnetic field and alaserbeam. has been developed[l]. In this paper, we apply the LMlA to alpha-fcroprotein (AFP), which is known as a tumor marker of hepatoma. The LMlA system shows asensitivity of 1 O-l5 g/ml of protein. Thii sensitivity value is comparable to that of radio immunoassay (RIA). The high sensitivity of our LMlA method is realized as a result of the remarkable effect of magnetic field on sample concentration and the optical interference detection.