Detection of staphylococcal enterotoxin A (SEA) at picogram level by a capacitive immunosensor

Abstract

This work presents the use of a flow injection capacitive immunosensor to detect staphylococcal enterotoxin A (SEA). The study was based on the direct detection of a capacitance change due to the binding between SEA and anti-SEA immobilized on a gold electrode. The optimal regeneration solution, flow rate, sample volume and buffer conditions were studied. Under the optimum conditions, this label-free biosensor provided linearity between 1 × 10(-12) g L(-1) and 1 × 10(-8) g L(-1) of SEA and the limit of detection was 1 × 10(-12) g L(-1) which was much lower than the infectious dose (0.5 × 10(-6) - 1 × 10(-6) g L(-1)). Using the regeneration solution of, 15.0 mM glycine-HCl pH 2.20, to break the binding between SEA and the immobilized anti-SEA enabled the electrode to be reused up to 39 times. This technique was applied to analyze SEA in liquid and solid food samples. Any matrix effect can be eliminated by simple dilution. SEA contamination was found in three samples, iced tea with milk (28 ± 1 ng L(-1)), orange juice (113 ± 6 ng L(-1)) and fried chicken (1.1 ± 0.2 ng g(-1)); however, the concentrations were much lower than the infectious dose. The proposed method would be useful for rapid screening of SEA in various matrices.

Monoclonal Antibody-Based Sandwich ELISA for the Detection of Staphylococcal Enterotoxin A

“…Staphylococcal enterotoxins (SEs) are single-chain proteins with molecular weights ranging from 27 to 34 kDa [3]. SEs are heat-stable, resistant to gut proteases, and active over a wide pH range [4].…”

“…A surface plasmon resonance biosensor has been reported to detect 1–40 ng/mL (ppb) SEA in raw whole eggs [6]. Jantra et al described a method for detecting SEA in various food samples based on a flow-injection capacitive immunosensor, and determined its LOD to be 1 fg/mL [3]. The immunosensor they used is highly sensitive and the matrix effects could be easily eliminated by dilution.…”

Asymmetric Mach–Zehnder Interferometer Based Biosensors for Aflatoxin M1 Detection

“…The regeneration of the antibody-functionalized surfaces can be obtained using different approaches. These are mainly based on solutions at low pH (HCl, Glycine-HCl), or at high pH (NaOH) or at high ionic strength (MgCl2) [ 18 ]. From five up to 39 regeneration cycles are reported for the whole antibody molecule [ 18 , 19 ], while for Fab′ molecules, a regeneration of four cycles has been found [ 20 ].…”

Detecting Biothreat Agents: From Current Diagnostics to Developing Sensor Technologies

“…Impedimetry has also been implemented to detect OTA in plant extracts by immobilization of anti-OTA antibody on BSA-modified gold electrodes . Some examples of capacitive sensors have been reported for the detection of SEB and SEA . In these formats, SEB is detected using HRP-labeled antibody with an LOD of 0.3 pg/mL in 10 min, whereas SEA sensing was in a label-free format with an LOD of 1 pg/mL.…”

“…1045 Some examples of capacitive sensors have been reported for the detection of SEB 1046 and SEA. 1047 In these formats, SEB is detected using HRP-labeled antibody with an LOD of 0.3 pg/mL in 10 min, whereas SEA sensing was in a label-free format with an LOD of 1 pg/mL. The latter was applied to contaminated food matrices such as tea, milk, fried chicken, and orange juice.…”