Ultra-sensitive immunosensor for detection of hepatitis B surface antigen using multi-functionalized gold nanoparticles

• An ultrasensitive immunosensor for monitoring hepatitis B surface antigen at detection limit of 0.36 pg mL−1 was introduced.
• We developed an improved ELISA approach by incorporating multi-functionalized gold nanoparticles as new types of labels.
• Signal amplification was obtained via streptavidin (as a label for antibody) to biotin-nanoparticle-luminol.
• Long biotin molecules on gold nanoparticles facilitated the accessibility for binding to streptavidin.

The signal amplification for analytical purposes has considerable potential in detecting trace levels of analytes for clinical, security or environmental applications. In the present report a strategy based on a sandwich type immunoassay system was designed for the detection of hepatitis B surface antigen which exploits the specific affinity interaction between streptavidin and biotin recognition systems. The method involves the specific coupling of multi-functionalized gold nanoparticles (bearing biotin and luminol molecules) to the streptavidin modified by secondary antibody. The chemiluminescent signal is produced by the gold nanoparticles in the presence of HAuCl4 as catalyst and hydrogen peroxide as oxidant. The immunosensor was able to detect hepatitis B surface antigen in the linear concentration range from 1.7 to 1920 pg mL−1 and the detection limit of 0.358 pg mL−1, at signal/noise = 3.

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