Novel printed electrode immunosensors for Schistosoma japonicum.

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. japonicum 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.

Reduction-sensitive N, N'-Bis(acryloyl) cystinamide-polymerized Nanohydrogel as a Potential Nanocarrier for Paclitaxel Delivery.

Novel monomer, N, N'-bis(acryloyl) cystinamide (NBACA), was designed and synthesized with L-cystine as row material. By using this NBACA both as the monomer and crosslinker, reduction-sensitive nanohydrogel was prepared in ethanol via distillation-precipitation polymerization. The obtained nanohydrogel can provide a relatively hydrophobic environment and hydrogen-bonding sites inside the gel; therefore, it is suitable for loading hydrophobic drug. When paclitaxel that possess poor water-solubility was used as a model drug, the nanohydrogel represented a high drug-loading capacity, and dispersed well in aqueous solutions. Furthermore, the disulfide-group-containing nanohydrogel exhibited good reduction-sensitive drug-release behavior. The nanohydrogel biodegraded rapidly in a reducing environment, and released approximately 80% of the PTX within 24 h. Cytotoxicity assays showed that the PTX-loaded nanohydrogel exhibited high cytotoxicity against MCF-7 breast cancer cells, while blank nanohydrogels displayed a negligible cytotoxicity.

Preparation and preliminary application of colloidal carbon dipstick for schistosomiasis japonica.

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.

A piezoelectric immunosensor using hybrid self-assembled monolayers for detection of Schistosoma japonicum.

BACKGROUND: The parasite Schistosoma japonicum causes schistosomiasis disease, which threatens human life and hampers economic and social development in some Asian countries. An important lesson learned from efforts to reduce the occurrence of schistosomiasis is that the diagnostic approach must be altered as further progress is made towards the control and ultimate elimination of the disease. METHODOLOGY/PRINCIPAL FINDINGS: Using mixed self-assembled monolayer membrane (mixed SAM) technology, a mixture of mercaptopropionic acid (MPA) and mercaptoethanol (ME) was self-assembled on the surface of quartz crystals by gold-sulphur-bonds. Soluble egg antigens (SEA) of S. japonicum were then cross-linked to the quartz crystal using a special coupling agent. As compared with the traditional single self-assembled monolayer immobilization method, S. japonicum antigen (SjAg) immobilization using mixed self-assembled monolayers exhibits much greater immunoreactivity. Under optimal experimental conditions, the detection range is 1:1500 to 1:60 (infected rabbit serum dilution ratios). We measured several infected rabbit serum samples with varying S. japonicum antibody (SjAb) concentrations using both immunosensor and ELISA techniques and then produced a correlation analysis. The correlation coefficients reached 0.973. CONCLUSIONS/SIGNIFICANCE: We have developed a new, simple, sensitive, and reusable piezoelectric immunosensor that directly detects SjAb in the serum. This method may represent an alternative to the current diagnostic methods for S. japonicum infection in the clinical laboratory or for analysis outside the laboratory.