ABSTRACT
Objective:To improve the sensitivity and the linear range of electrochemical immunosensor to detect Schistosoma japonicum (S.japonicum) antibody.Methods:Carbon inks and silver/silver chloride inks were printed on a polyethylene terephthalate (PET) board to make a two-electrode test strip,where carbon was the working electrode and S.japonicum soluble egg antigen (SEA) was fixed at one end of working electrode by different methods; silver/silver chloride electrode was used as control.We tested the valency of the antibody by cyclic voltammetry (CV) and differential pulse voltammetry (DPV) in an electrochemistry workstation,and conducted comparison with the results of ELISA.Two new immunosensing electrodes have been developed,based on glutaraldehyde cross-linked (GA) or chitosan-glutaraldehyde cross-linked (Chit-GA) transducer fixing S.japonicum antigen.We tested the titer of the antibody by means of CV and DPV.Results:Our experimental S.japonicum antigen (50 μg/L) is the optimal test concentration for the GA sensor,and 10 μg/L for Chit-GA sensors.The immune reaction time of both electrodes is all essentially complete in 1 minute.The linear range for S.japonicura antibody in human positive serum sample detection by the glutaraldehyde cross-linked immunosensor is 1∶1000 to 1∶400,and by the chitosan-glutaraldehyde cross-linked immunosensor is 1∶1000 to 1∶500.As the concentration of dilution ratio of S.japonicum antibody in human positive serum sample increased,the test value of DPV increased proportionally.Conclusion:GA sensor and Chit-GA cross-linked S.japonicum sensors have high sensitivity and broad linear range response,and both exhibited a good linear relationship between the DPV signal and the test antibody titer.
ABSTRACT
OBJECTIVE@#To develop a rapid and simple immunoassay to detect antibodies in the sera of patients infect Schistosoma japonicum (S. japonicum).@*METHODS@#Soluble egg antigen (SEA) of S. japonicum conjugated with colloidal carbon in advance was used to react with the antibodies in the sera of patients with schistosomiasis. Then the carbon-antigen-antibody complex would be captured by SEA which had been absorbed on the nitrocellulose membrane and a gray band was shown.@*RESULTS@#A total of 137 sera samples from S. japonicum epidemic area were tested, and the consistency, sensitivity, and specificity of colloidal carbon dipstick assay were 98.54%, 98.99%, and 97.37%, respectively, compared with the IHA method. The gray scale of bands on the dipstick was curvilinear to serum titer which revealed that the assay could be used semi-quantitatively in serum analysis.@*CONCLUSION@#Colloidal carbon dipstick assay is not only rapid and simple, but also sensitive and specific for the detection of serum antibodies of schistosomiasis japonica. It will be a practical immunological assay for the diagnosis of schistosomiasis in the field testing.