A novel method to detect circulating antigens of Schistosoma japonicum using a gold nanorod optical sensor

Diagnostic method of Schistosoma japonicum (S.japonicum) is the key of schistosomiasis prevention and control. In China, schistosomiasis reached the stage of transmission control, and almost of the epidemic areas tend to have low infection rate and intensity, but it is difficult for the existing detection methods to achieve accurate monitoring. In this study, a novel method to detect the circulating antigens of S.japonicum using gold nanorods optical sensor was developed. Gold nanorods were prepared by seed-mediated growth followed by deposition onto Indium-Tin-Oxide (ITO) glass to fabricate a solid phase biosensor. In order to assembly between the ITO glass and gold nanorod, hydroxylation and sulfhydrylation were carried out to modify the ITO glass. Surface of gold nanorods was conjugated with an SIEA26-28kDaSjscFv antibody against S.japonicum circulating antigens, and the sensor optical changed upon antigen-antibody recognition. The sensor was used to detect S.japonicum infection in rabbits by testing the serum once a week for 8 weeks. Results revealed different displacement of localized surface plasmon resonance (LSPR) of the gold nanorod optical sensor each week while the control group showed no such change in LSPR. Simultaneously, Indirect Hemagglutination Assay(IHA) and Fast Enzyme-Linked Immuno Sorbent Assay (F-ELISA) method were used to test these samples. Ten human serum samples from S.japonicum infected patients were analyzed using the gold nanorods optical sensor, which revealed that health human serum did not show any spectrum displacement. We developed a specificity gold nanorod optical sensor by combining the SIEA26-28kDaSjscFv, which was used to detect circulating antigens of S.japonicum. This method is expected to overcome the issues pertaining to the testing of circulating antigens of S.japonicum.