Sulfonamide acridinium esters

ImmunO lSS iy. Chemiluminescence compounds (eg, acridinium esters and sulfonamides, isoluminol), luciferases (eg, firefly, marine bacterial, Benilla and Varela luciferase), photoproteins (eg, aequorin, Benilld), and components of bioluminescence reactions have been tested as replacements for radioactive labels in both competitive and sandwich-type immunoassays. Acridinium ester labels are used extensively in routine clinical immunoassay analysis designed to detect a wide range of hormones, cancer markers, specific antibodies, specific proteins, and therapeutic dmgs. An acridinium ester label produces a flash of light when it reacts with an alkaline solution of hydrogen peroxide. The detection limit for the label is 0.5 amol. 

Chemiluminescence assays are ultrasensitive (attomole to zeptomole detection limits) and have wide dynamic ranges. They are now widely used in automated immunoassay and DNA probe assay systems, (e.g., acridinium ester and acri-dinium sulfonamide labels and 1,2-dioxetane substrates for alkaline phosphatase labels and the enhanced-luminol reaction for horseradish peroxidase labels [see Chapter 9]). 

Fig. 28. Novel thiocarboxylate (a) and sulfonamide (b) acridinium esters synthesized by Kinkel et al. (KIO).

Two automated complete assay systems, utilizing acridinium esters and particle solid phases, have been recently described. A high-throughput bench-top system is able to process 180 samples per hour and the time to the first assay result is 15 min. Actual assay times are 7 min per sample (K34). The dimethyl acridinium ester label in this system has already been described (L2). The second system employs an acridinium sulfonamide (M12) and coated 4-in. polystyrene beads or latex microparticles as solid phases. Assays for P-HCG, CEA, and TSH have been reported (K5). 

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