title: Toward a Boron-Doped Ultrananocrystalline Diamond Electrode-Based Dielectrophoretic Preconcentrator.
abstract: This paper presents results on immunobeads-based isolation of rare bacteria and their capture at a boron-doped ultrananocrystalline diamond (BD-UNCD) electrode in a microfluidic dielectrophoretic preconcentrator. We systematically vary the bead surface chemistry and the BD-UNCD surface chemistry and apply dielectrophoresis to improve the specific and the nonspecific capture of bacteria or beads. Immunobeads were synthesized by conjugating antibodies to epoxy-/sulfate, aldehyde-/sulfate, or carboxylate-modified beads with or without poly(ethylene glycol) (PEG) coimmobilization. The carboxylate-modified beads with PEG provided the highest capture efficiency (∼65%) and selectivity (∼95%) in isolating live Escherichia coli O157:H7 from cultures containing 1000 E. coli O157:H7 colony-forming units (cfu)/mL, or ∼500 E. coli O157:H7 and ∼500 E. coli K12 cfu/mL. Higher specificity was achieved with the addition of PEG to the antibody-functionalized bead surface, highest with epoxy-/sulfate beads (85-86%), followed by carboxylate-modified beads (76-78%) and aldehyde-/sulfate beads (74-76%). The bare BD-UNCD electrodes of the preconcentrator successfully withstood 240 kV/m for 100 min that was required for the microfluidic dielectrophoresis of 1 mL of sample. As expected, the application of dielectrophoresis increased the specific and the nonspecific capture of immunobeads at the BD-UNCD electrodes; however, the capture specificity remained unaltered. The addition of PEG to the antibody-functionalized BD-UNCD surface had little effect on the specificity in immunobeads capture. These results warrant the fabrication of electrical biosensors with BD-UNCD so that dielectrophoretic preconcentration can be performed directly at the biosensing electrodes.
authors.affiliation: Institute for Micromanufacturing, Center for Biomedical Engineering and Rehabilitation Sciences, Chemical Engineering, Louisiana Tech University , Ruston, Louisiana 71272, United States.
authors.forename: Wenli
authors.initials: W
authors.lastname: Zhang
authors.affiliation: Institute for Micromanufacturing, Center for Biomedical Engineering and Rehabilitation Sciences, Chemical Engineering, Louisiana Tech University , Ruston, Louisiana 71272, United States.
authors.forename: Adarsh D
authors.initials: AD
authors.lastname: Radadia
mesh_terms: D000818:Animals; D015374:Biosensing Techniques / Q000295:instrumentation / Q000379:methods*; D001895:Boron / Q000737:chemistry*; D004566:Electrodes; D004586:Electrophoresis; D004926:Escherichia coli / Q000302:isolation & purification*; D007074:Immunoglobulin G / Q000737:chemistry; D051379:Mice; D058612:Nanodiamonds / Q000737:chemistry*; D011137:Polystyrenes / Q000737:chemistry
chemical_list: D007074:Immunoglobulin G; D058612:Nanodiamonds; D011137:Polystyrenes; D001895:Boron