Detection of Staphylococcal enterotoxin B via biomolecular interaction analysis mass spectrometry

Abstract

Detection of Staphylococcus enterotoxin B (SEB) by biomolecular interaction analysis mass spectrometry (BIA/MS) is presented in this work. The BIA/MS experiments were based on a surface plasmon resonance (SPR) MS immunoassay that detects affinity-captured SEB both via SPR and by means of exact and direct mass measurement by matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry. Experiments were performed with standard samples and food samples to assess the BIA/MS limit of detection for SEB and to set the experimental parameters for proper quantitation. Single and double SPR referencing was performed to accurately estimate the amount of the bound toxin. Reproducible detection of 1 ng of SEB per ml, corresponding to affinity capture and MS analysis of approximately 500 amol of SEB, was readily achieved from both the standard and mushroom samples. A certain amount of SEB degradation was indicated by the signals in the mass spectra. The combination of MS with SPR-based methods of detection creates a unique approach capable of quantifying and qualitatively analyzing protein toxins from pathogenic organisms.

FIG. 1.

(a) SPR sensorgrams (baseline corrected from an anti-TTST-1-derivatized reference FC) resulting from four consecutive 100-μl injections of 10 ng of SEB per ml in HBS-EP buffer, 1 ng of SEB per ml in HBS-EP, HBS-EP buffer, and 1 ng of SEB per ml in HBS-EP. (b) Overlay view of the four binding curves. (c) SEB binding curves corrected by subtraction of the buffer injection sensorgram. (d) MALDI-TOF mass spectrum taken from the surface of FC1 following the last injection of the 1-ng/ml SEB aliquot.

FIG. 2.

(a) Overlaid SPR sensorgrams resulting from injections of 10 and 1 ng of SEB-mushroom samples per ml and a mushroom sample (SEB free) over the surface of an anti-SEB-derivatized flow cell. (b) SEB-mushroom binding curves corrected via subtraction of the mushroom sample injection sensorgram. (c) MALDI-TOF mass spectrum taken from the surface of FC1 following an injection of 1 ng of SEB-mushroom sample per ml.

FIG. 2.

(a) Overlaid SPR sensorgrams resulting from injections of 10 and 1 ng of SEB-mushroom samples per ml and a mushroom sample (SEB free) over the surface of an anti-SEB-derivatized flow cell. (b) SEB-mushroom binding curves corrected via subtraction of the mushroom sample injection sensorgram. (c) MALDI-TOF mass spectrum taken from the surface of FC1 following an injection of 1 ng of SEB-mushroom sample per ml.

FIG. 2.

(a) Overlaid SPR sensorgrams resulting from injections of 10 and 1 ng of SEB-mushroom samples per ml and a mushroom sample (SEB free) over the surface of an anti-SEB-derivatized flow cell. (b) SEB-mushroom binding curves corrected via subtraction of the mushroom sample injection sensorgram. (c) MALDI-TOF mass spectrum taken from the surface of FC1 following an injection of 1 ng of SEB-mushroom sample per ml.