RESUMO
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.
RESUMO
Objective To prepare the infected Oncomelania hupensis by artificial method for the research on the activity, vaccine, and genetic variation of Schistosoma Japonicum (S. Japonicum).Methods The mature eggs of S. Japonicum were collected by Nylon silk method and the miracidia were incubated under appropriate conditions. Negative snails were infected with miracidia in different proportion by means of individual or collective infection to seek the best method and proportion of infection between miracidia and snails. Infected snails were divided into 12 groups in total. Ⅰ-Ⅵ groups were for individual infection and Ⅶ-Ⅻ groups were for collective infection. There were 200 snails in each group. The infection ratios between snails and miracidia in Group Ⅰ-Ⅵ or screened, numbered, and reared singly. The amount of cercariae was calculated once every 10 days until the infected snails died. Then cercariae shedding quantity, infection quantity, and mortality of infected snails in every group were compared to find the best infection method and the best infection proportion between miracidia and snails. The cercariae were collected from the first generation of infected snails and were used to infect experimental animals. The mature eggs of S. Japonicum were saved from the infected experimental animals and incubated to get miracidia. The snails were artificially infected by miracidium to get the second generation of infected snails. The developmental rates of adult worms, the egg density in fecal and liver were compared between artificially and naturally infected snails. Results In individual infection GroupⅠ-Ⅵ,the average infection value of snails were 0±0,22.7±4.2,31.7±4.5,53.0±5.3,39.3±5.9,32.7±4.7,the average fatality of snails were 21.7±3.1,25.0±3.6,31.3±4.9,44.7±6.5,78.3±9.5,89.7±13.6, and the average value of cercariae shedding from infected snails were 0.0±0.0,308.0±96.6,428.1±146.2,527.0±171.1,571.4±148.9,602.9±356.3, respectively. In collective infection Group Ⅶ-Ⅻ,the average infection value of snails were 0±0,12.3±2.5,18.7±4.7,28.3±4.2,33.3±4.7,29.3±5.5,and the average fatality of snails were 22.7±3.8,23.7±4.5,28.3±5.5,47.0±9.5,75.7±8.5,86.3±12.2, and the average value of cercariae shedding from infected snails were 0±0,244.5±57.3,292.3±74.8,347.1±100.8,477.2±142.1,447.3±161.4, respectively. The second generation of artificially infected snails was obtained successfully. The average infection rate and fatality rate for the second generation of artificially infected snails were 24.65% and 24.50%, both of which were not obviously different from that of the first generation of artificially infected snails (P>0.05). In the animal experiment, the worm growth rate for the naturally infected snails, the first or second generation of artificially infected snails were 68.50%,73.50% or 71.00%. There was no obvious difference among them (P>0.05). The fecal (or liver) eggs per gram for the naturally infected snails, the first or the second generation of artificially infected snails were 1 503±269,1 683±233, or 1 541±117 (or 6 641±1 819,6 272±1 419, or 7 263±1 643). There was no significant difference among the 3 groups (P>0.05). Conclusion Infected snails can be obtained through the artificial method by using S. Japonicum miracidia to infect snails. Individual infection has the advantage over collective infection. The optimal proportion of infection between first and the second generation of artificially infected snails in the average of cercariae shedding, infection, and fatality average of snails. There was no significant difference between artificially and naturally infected snails in the developmental rate of adult worms, fecal and liver eggs per gram.