Sensitive Detection of TNT using Competition Assay on Quartz Crystal Microbalance

Abstract

Currently available TNT sensors are characterized by high sensitivity, but low specificity, which limits the detection of TNT in dirty environments. We report here a TNT sensor designed to measure the displacement of a TNT-specific antibody by quartz crystal microbalance (QCM). This sensor combines high sensitivity of detection (0.1 ng/mL) with the ability to distinguish TNT from molecules with similar chemical properties. Particularly, the reliability of this method for the detection of TNT in dirty environments was investigated by using fertilizer solution and artificial seawater. Instead of measuring actual binding of TNT, the method described is based on the displacement of an anti-TNT antibody, which allows quantifying the concentration of TNT in solution with higher sensitivity. In addition, by utilizing the rate of antibody displacement, the detection time is significantly decreased from hours, which would be necessary to measure the frequency change at equilibrium, to minutes. A Langmuir kinetic model was used to describe the molecular interactions on the surface of the sensor and to establish a standard curve to estimate on-site TNT detection. In summary, QCM detection of anti-TNT antibody displacement provides a method for rapid detection of TNT with high sensitivity and specificity.

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“…where q is the fraction of the SLBs with attached polymer and (1 À q) represents the sites available for further polymer association. Dening K A as the ratio of k A to k ÀA , the following equation describes the relationship between the polymer concentration and the surface stress change measured on the cantilever (a detailed derivation has been previously reported 53 and is shown in the ESI †):…”

“…18 This model has been previously used to describe the binding between antigenantibody systems on microcantilevers. 43,53 The association constant K A is calculated using eqn (6). Fig.…”

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