Flow‐Through Microbial Capture by Antibody‐Coated Microsieves

A new flow-through method for rapid capture and detection of microorganisms is developed using optically-flat microengineered membranes. Selective and efficient capture of Salmonella is demonstrated with antibodies coated on membranes (microsieves) having a pore size much larger than the microorganism itself. The silicon-nitride membranes are first photochemically coated with 1,2-epoxy-9-decene yielding stable Si-C and N-C linkages. The resultant epoxide-terminated microsieves are subsequently biofunctionalized with anti-Salmonella antibodies. The capture efficiency of antibody-coated microsieves with different pore sizes (2.0-5.0 m) is studied with Salmonella enterica enterica serotype Typhimurium suspensions (10(7) cfu mL(-1)). The antibody-coated microsieves capture 52% (2 m microsieves), 30% (3.5 m microsieves), and 12% (5 m microsieves) of Salmonella from the suspension. The influence of flow rate (0.8-16 L min(-1) mm(-2)) on the capture efficiency of antibody-coated 3.5 m microsieves is investigated. The capture efficiency increases from approximate to 30% to approximate to 70% when the flow-rate decreases from 16 to 0.8 L min(-1) mm(-2). Antibody-coated 3.5 m microsieves can capture Salmonella rapidly and directly from fresh milk suspension (capture 35% at concentration of 80 cfu mL(-1)). The use of antibody-coated microsieves as microbial selective capture devices is thus shown to be highly promising for the direct capture of microorganisms.