Abstract

In this study, we modified a surface plasmon resonance immunosensor chip with a polymer using surface-initiated atom transfer polymerization (SI-ATRP) for the highly sensitive detection of 2,4,6-trinitrotoluene (TNT). To immobilize a TNT analogue on the polymer, mono-2-(methacryloyloxy)ethylsuccinate (MES), which has a carboxyl group, was used in this study. However, the anti-TNT antibody may adsorb non-specifically on the polymer surface by an electrostatic interaction because MES is negatively charged. Therefore, a mixed monomer with MES and diethylaminoethylmethacrylate (DEAEM), which has a tertiary amino group and is positively charged, was prepared to obtain electroneutrality for suppressing the nonspecific adsorption. The detection of TNT was performed by inhibition assay using the polymer surface. To ensure high sensitivity to TNT, the affinity between the surface and the antibody was optimized by controlling the density of the initiator for ATRP by mixing two types of self-assembled monolayer reagents. As a result, a limit of detection of 5.7 pg/mL (ppt) for TNT was achieved using the optimized surface.

Highlights

  • There has been increasing concern about terrorist attacks using bombs

  • surface plasmon resonance (SPR) response, which is defined in resonance units (RU), increased with increasing amount of antibody bound on the surface

  • We have fabricated an SPR sensor surface modified with a polymer by surface-initiated atom transfer polymerization (SI-ATRP) for TNT

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Summary

Introduction

There has been increasing concern about terrorist attacks using bombs. Metal detectors, X-ray inspection apparatus, and sniffer dogs are mainly used to detect explosives. The detection was performed using a localized surface plasmon resonance (LSPR) sensor containing an imprinted polymer with gold nanoparticles [1] The advantage of this method is its ultrahigh sensitivity to 2,4,6-trinitrotoluene (TNT). An electrochemical method employing SiO2 nanostructures was developed to detect nitroaromatic compounds [2] This method has the advantage that the instrument used for detection is simple and suitable for constructing inexpensive and portable sensors. These brushes were used to measure a component in blood plasma without purification [11] As another application of SI-ATRP, two types of polymer chains were grown in series from a surface to realize two different characteristics by living polymerization. The second polymer with a low packing density was prepared to achieve a high protein-binding capacity [12] Another application is the amplification of SPR signals. The limit of detection (LOD) for TNT was evaluated on the SPR sensor modified with the polymer surfaces of various densities

Materials
Fabrication of Sensor Chip Surface
Instrument and Conditions for SPR
TNT Detection Using the Inhibition Assay
Control of Nonspecific Adsorption on Poly-MES-Co-Poly-DEAEM Based Surface
Highly Sensitive Detection of TNT
Conclusions
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