Dot-immunobinding assay using indirect photoacoustic measurement.

Dot-immunobinding assay of hepatitis B surface antigen (HBsAg) was performed by a conventionally dot-ELISA technique with 4-chloro-1-naphthol staining, and the quantitative results were measured by an indirect photoacoustic method. In this method, a 2-mW helium-neon laser was applied to provide the excitation beam, the blue spots on the membrane were detected in a piezoelectric transducer-based photoacoustic cell. The operational conditions of measurement were optimized. A significant difference from the negative human serum was obtained for 50 pg in HBsAg detection. The method proposed provides a sensitive quantitative technique for dot-immunobinding assay.