A combined lab-on-a-chip approach combining immunomagnetic separation (IMS) and flow cytometry was developed for the enrichment and detection of salmonella contamination in food samples. Immunomagnetic beads were immobilized in chips consisting of long fractal meanders while contaminated samples were flowed over them. After incubation the beads can be released for detection into the flow-cytometry chip. Immunomagnetic beads were prepared by using anti-Salmonella antibodies and magnetic beads (2.8μm). Both the synthesized and commercially available anti-Salmonella beads were used to capture Salmonella from samples artificially contaminated with a concentration range of 10^2 to 10^7 mL-1 and the captured Salmonella were then detected and quantified flow cytometrically after vital staining. The results showed that on-chip IMS could effectively discriminate a bacterial contamination of 10^4/ml from control (0.22 μm sterile filtered buffer) with 65-85% recovery of magnetic beads. The parameters of the IMS and staining process (incubation time, temperature and buffering conditions) were optimized. Optimum interaction time and temperature was 20 minutes and 22°C (room temperature) respectively to obtain maximum capturing efficiency. The effects of channel volume, path length and number of bends of microfluidic chip on IMS efficiency were also determined.
Microfluidics; Immunomagnetic Separation; Lab on chip