Identification and quantitation of Bacillus globigii using metal enhanced electrochemical detection and capillary biosensor

Samuel K. Mwilu, Austin O. Aluoch, Seth Miller, Paula Wong, Omowunmi A. Sadik, Alim A. Fatah, Richard D. Arcilesi

Research output: Contribution to journalArticlepeer-review

28 Scopus citations


Presented herein are two detection strategies for the identification and quantification of Bacillus globigii, a spore forming nonpathogenic simulant of Bacillus anthracis. The first strategy involves a label-free, metal-enhanced electrochemical immunosensor for the quantitative detection of Bacillus globigii( atrophaeus). The immunosensor comprises of antibacillus globigii (BG) antibody selfassembled onto a gold quartz crystal electrode via cystamine bond. A solid-phase monolayer of silver underpotentially deposited onto the cystamine modified-Au-electrode surface is used as the redox probe. The monolayer was also generated by adsorbing silver nanoparticles on the gold electrode. When the antibody-modified electrode is exposed to BG spores, the antibody-antigen (Ab-Ag) complex formed insulated the electrode surface toward the silver redox probe. The variation of redox current was found to be proportional to the concentration of the BG spores between 1 x 102-3.5 x 104 spores/mL. A detection limit of 602 spores/mL was obtained, which is well-below the infectious dose of anthrax spores at 2.5 x 105 spores/mL. The second approach involves the use of ultrasensitive portable capillary biosensor (UPAC) to detect the spores. The capillary is an enclosed system that acts as the flow cell, the waveguide, and the solid support for immobilized bimolecular probes. An evanescent excitation generates a signal from an antigen-antibody- fluorophore complex, which propagates along the capillary and is guided to the detector. A limit of detection of 112 spores/mL was reported using the UPAC sensor. Both methods showed lower detection limits compared to the conventional ELISA. The effect of potential interferants tested using Bacillus pumilusconfirmed the selectivity for the analyte. This work should allow the first responders to rapidly detect and quantify Bacillus globigii spores at concentrations that are well-below the infectious dose.

Original languageEnglish (US)
Pages (from-to)7561-7570
Number of pages10
JournalAnalytical Chemistry
Issue number18
StatePublished - Sep 15 2009
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Analytical Chemistry


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