Target antigen serum albumin

Proteins such as cytochrome c are not good target antigens for the determination of species of origin because the structures of these proteins in evolutionarily distant species are very similar. Serum albumin, on the other hand, is a rapidly changing protein (Table I) that is amenable to complete immunochemical analysis with both polyclonal and monoclonal antibodies (14-16). Albumins from thousands of pairs of vertebrate species have been compared immunochemically, and the results have been used to measure evolutionary distances (22). 

We also reported a concept for a sandwich immunoassay that is completely performed on-chip using streptavidin-coated beads as substrate [17]. The latter were electrostatically self-assembled on aminosilane micropattems at the bottom of a microfluidic channel. We used mouse IgG diluted in phosphate buffered saline (PBS) with 1% bovine serum albumin (BSA) solution as target antigen. The fluorescent sandwich immunocomplex was formed on the beads during the operation of the chip both in stop-flow and continuous flow modes. Target mouse IgG antigen could be detected down to a concentration of 15 ng/mL in stop-flow mode and 250 pg/mL in continuous flow mode, using only 1,300 nL of sample volume. 

The highly specific and sensitive recognition of antigens by antibodies can be used for imunoaffinity purification. Antibodies, trapped within a silica gel, bind a specific molecule from a mixture of compounds. Small molecules (haptens) have to be bound to a macro-molecular carrier such as bovine serum albumin (BSA) to induce an immune response and stimulate the production of antibodies. These antibodies are then able to recognize specifically the target analyte (hapten) and have been used for the detection of various chemicals such as fluorescein, dinitrophenyl (DNP), dinitrobenzene (DNB), and even TNT (Wang, 1993 Aharonson, 1994 Jordan, 1996 Bronshtein, 2000 Lan, 2000 Vazquez-Lira, 2003). 

---