A novel and effective natural product-based immunodetection tool for TNT-like compounds

Biotin as a structural component in the detection of small model antigens in BLA-S-ELISA

An interesting biotin-linked-antigen-Sandwich-ELISA was developed (BLA-S-ELISA), which based on the captured Trinitrophenol-Biotin (TNP-Biotin) molecule between the immobilised monovalent antibody and enzyme-conjugated streptavidin. Monoclonal anti-Trinitrotoluene single chain fragment antibody (anti-TNT-scFv) was cloned and expressed in E. coli cells, and then used as an immobilised component in an assay. Thereafter, the previously synthesised TNP-Biotin was added as antigen followed by the addition of streptavidin-horseradish peroxidase (streptavidin-HRP) conjugate which led finally to the formation of a three-component system (antibody/TNP-Biotin/streptavidin-HRP). The assay was performed with a range of different dilutions of TNP-Biotin to establish its minimal detectable concentration. The detection limit of TNP-Biotin was 4 ngmL-1 (i.e. 200 pg or 0.42 pmol antigen calculated on the basis of 50 μL sample or 8.4 nM expressed in concentration units). According to our best knowledge, this is the very first time for any model antigen to be detected with such a form of biotin-streptavidin sandwich-assay.

3.5-scFv-β-lactamase, a new protein detector of picric acid, the highly nitrated organic explosive

A new protein detector of 2,4,6-trinitrophenol (TNP, picric acid) is concisely reported herein for the first time. In brief, the gene of a specific scFv fragment, namely 3.5, was fused separately with the gene of β-lactamase and, subsequently, expressed in the periplasmic space of Escherichia coli, affording in such a way the recombinant fusion protein 3.5-scFv-β-lactamase. This bifunctional immunoreagent tool was further convincingly demonstrated for being capable to directly detect trinitrophenol-tris(hydroxymethyl)aminomethane (TNP-Tris), a less toxic TNP derivative of choice compared to TNP itself, with competitive sensitivity (50 ± 2 fmol or 175 ± 6 pg/mL).