Precolumn affinity capillary electrophoresis for the identification of clinically relevant proteins in human serum: Application to human cardiac troponin I

An approach has been developed to the on-line extraction and identification of clinical disease-state marker proteins in human serum. Fabrication of capillaries with integral packed beds for the online determination of human cardiac troponin I (cTnI), a diagnostic marker for myocardial infarction, at clinically relevant levels (2 nmol/L) in serum is demonstrated. The technique, termed precolumn affinity capillary electrophoresis (PA-CE), utilizes a short (~5 mm) packed bed of porous silica containing covalently immobilized monoclonal anti-cTnI antibodies directly integrated within a separation capillary for the selective retention of cTnI from a complex matrix. Following a rinsing step to eliminate nonspecifically bound serum proteins and other impurities from the column, desorption of the antigen into the separation region of the PA-CE capillary for subsequent measurement of femtomolar amounts of cTnI by CE is effected by the injection of an appropriate elution buffer. Advantages of this approach over previously reported affinity preconcentration techniques, related applications for PA-CE technology, and its potential for use in the development of a certified reference material for cTnI in serum are discussed.