Silica Sol-gel Amperometric Immunosensor for Schistosoma Japonicum Antibody Assay

Diagnosis of schistosomiasis japonica with interfacial co-assembly-based multi-channel electrochemical immunosensor arrays

Schistosomiasis control remains to be an important and challenging task in the world. However, lack of quick, simple, sensitive and specific sero-diagnostic test is still a hurdle in the control practice. The commonly employed enzyme-linked immuno-sorbent assay (ELISA) relies on the native soluble egg antigen (SEA) that is limited in supply. Here we developed an electrochemical immunosensor array (ECISA) assay with an interfacial co-assembly strategy. A recombinant Schistosoma japonicum (Sj) calcium-binding protein (SjE16) was used as a principal antigen, while the SEA as a minor, co-assembling agent, with a ratio of 8:1 (SjE16: SEA, Sj16EA), which was co-immobilized on a disposable 16-channel screen-printed carbon electrode array. A portable electrochemical detector was employed to detect antibodies in serum samples. The sensitivity of ECISA reached 100% with minimal cross-reactions. Therefore, we have demonstrated that this rapid, sensitive and specific ECISA technique has the potential to perform large-scale on-site screening of Sj infection.

Magnetic nanoparticle-based immunosensor for electrochemical detection of hepatitis B surface antigen

An electrochemical immunosensor was developed for the detection of hepatitis B surface antigen (HBsAg). The biotinylated hepatitis B surface antibody was immobilized on streptavidin magnetic nanoparticles and used for targeting the HBsAg. By the addition of horseradish peroxidase conjugated with secondary antibody (HRP-HBsAb), a sandwich-type immunoassay format was formed. Aminophenol as substrate for conjugated HRP was enzymatically changed into 3-aminophenoxazone (3-APZ). This electroactive enzymatic production (3-APZ) was transferred into an electrochemical cell and monitored by cyclic voltammetry. Under optimal conditions, the cathodic current response of 3-APZ, which was proportional to the HBsAg concentration, was measured by a glassy carbon electrode. The immunosensor response was linear toward HBsAg in the concentration range from 0.001 to 0.015 ng/ml with a detection limit of 0.9 pg/ml at a signal/noise ratio of 3.

Antibody-based sensors: principles, problems and potential for detection of pathogens and associated toxins

Antibody-based sensors permit the rapid and sensitive analysis of a range of pathogens and associated toxins. A critical assessment of the implementation of such formats is provided, with reference to their principles, problems and potential for 'on-site' analysis. Particular emphasis is placed on the detection of foodborne bacterial pathogens, such as Escherichia coli and Listeria monocytogenes, and additional examples relating to the monitoring of fungal pathogens, viruses, mycotoxins, marine toxins and parasites are also provided.

Antibody detection employing sol-gel immobilized parasites

Immunofluorescence assay (IFA) and immunoperoxidase assay (IPA) are useful diagnostic techniques for specific antibody detection for different diseases. Both involve several alternatives for immobilization of cells, such as solvent or heat fixation. Non-covalent immobilization implies rigorous storage conditions at -20 degrees C to preserve the slides, and usually numerous cells are detached during the washing steps, which can lead to inconsistencies in the results. Sol-gel chemistry is usually used for coating different materials because of the mild conditions of the polymerization reaction and the ability to introduce functional groups to a wide variety of surfaces. We have developed a novel procedure for the attachment of Trypanosoma cruzi epimastigotes and Leishmania guyanensis promastigotes to a silicon oxide polymer covered glass surface. The film was prepared using standard microscope slides with tetraethoxysilane and 3-aminopropyl triethoxysilane as polymeric precursors. When acetone was used as the major coating solvent, the IFA showed the fluorescence of the attached parasites without matrix background interference. Similar results were observed when the IPA was evaluated. The sensitivity and specificity of the sol-gel immobilized parasite slides were comparable with the heat fixation technique. The performance of the coated slides was maintained for at least 2 months at 4 degrees C storage temperature. This immobilization method does not affect the molecular epitopes of the attached cells. Thus, homogeneous, ready to use, long lasting coated slides were obtained, which are appropriate for field conditions.

Amperometric immunosensor for detecting Schistosoma mansoni antibody

An immunosensor for detecting the antibody anti-apyrase of Schistosoma mansoni based on rigid composite materials, containing graphite powder and epoxy resins, developed in this work, is described. A surface modification strategy for the use of oxidized graphite in the detection of antibody-antigen interaction was developed. This modification strategy is based on silanization of conductive composite. First, the graphite powder-epoxy resin was treated with concentrated hydrogen peroxide to improve surface hydroxyl groups and to form a hydrophilic layer. Second, 3- aminopropyltriethoxysilane was subsequently used to functionalize the treated surface to form amino groups, which were further activated with glutaraldehyde to introduce a layer of aldehyde groups. Contact angle microscopy and scanning electron microscopy were used as a qualitative analysis of the deposition of silane on the surface of the sensor. The effectiveness of the modification strategy was validated by amperometric immunoassays of S. mansoni. Amperometric signals related to concentrations of this immobilized protein were observed, and the effects of pH and incubation times were analyzed. This surface modification strategy provides a platform on which proteins can be directly immobilized for immunosensor and protein array applications.