Size Specific Immunofluorescence of Mycobacterium Tuberculosis Cells by Using a Microtip-Sensor

The size-specific capturing mechanism for Mycobacterium tuberculosis (MTB) cells is presented using a microtip-sensor. When a microtip is withdrawn from a solution drop, enriched cells by an alternating current (AC) electric field are selectively captured onto the tip due to capillary- and viscous forces. The size-specificity on the 50 μm-diameter tip is studied by using polystyrene microspheres. The size-specific capturing mechanism is applied to capture MTB cells from a sample mixture containing MTB and Drosophila S2 cells. Under the competition between capillary- and viscous forces, MTB cells are captured onto the microtip by the viscous force, while Drosophila S2 cells are removed from the tip by the capillary force. The microtip-sensor yields the detection limit of 800 cells/mL for MTB cells, which is one of the highest-sensitivity immunosensors.