Practical application of bioluminescence enzyme immunoassay using enhancer for firefly luciferin-luciferase bioluminescence.

Firefly luciferin-luciferase bioluminescence is known for its high quantum yield (41.0 ± 7.4%). Given this high quantum yield, application of this bioluminescence is expected to be useful in the field of clinical diagnostics. The kinetic profile of this bioluminescence exhibits an instant rise (<1 s) and a rapid decay in light emission (decreased to 42% after 5 s). In this study, we applied four enhancers including coenzyme A, inosine5'-triphosphate sodium salt, sodium tripolyphosphate and potassium pyrophosphate to prolong light emission. When these enhancers were used, luminescence was only decreased to 89, 83, 87 and 82% after 5 s, respectively. These materials modified the kinetic profile of bioluminescence so that the luminescence is more suitable for clinical application. It becomes more suitable because they enable highly sensitive integration and simplification of a device by separating luminescence measurements from dispensing of reagents. Using these enhancers, we then developed a bioluminescent enzyme immunoassay (BLEIA) for hepatitis B virus surface antigen (HBsAg) that employed firefly luciferase as a labeling enzyme. We compared the results obtained from the HBsAg BLEIA method with the conventional chemiluminescent enzyme immunoassay method, and found a satisfactory correlation r=0.984, n=118.