Single-bead-based immunofluorescence assay for snake venom detection

In this communication, we reported a rapid and sensitive immunofluorescence method for the detection of snake venom by using microscale polystyrene beads as platform combined with semiconductor quantum dots (Qdots) as fluorescence label. Briefly, control rabbit IgG or capture antibody for venom was covalently immobilized onto the microspheres (surface activated with carboxyl group, dyed with different color) to form the control or capture beads. When incubated with the testing samples, the venom binds to the specific capture beads to form the complex through antibody-antigen interaction. Then, the second antibody conjugated Qdot was added, which targeted the Qdot to bind to the capture bead/antigen complex. The complex can be directly observed under a UV microscope. The system was applied to the testing of Naja kaouthia venom. Fluorescent microscopic images of QD-labeled capture beads demonstrated that QD-antibody conjugates could evenly and completely attach to the surface of capture beads, indicating that the conjugated antibody molecules remained active and were able to recognize their specific target in solution. The detection limit of this method was 5-10 ng/mL. The detection could be completed within 3 h.