Elsevier

Applied Surface Science

Volume 411, 31 July 2017, Pages 205-209
Applied Surface Science

Full Length Article
A new technique to detect antibody-antigen reaction (biological interactions) on a localized surface plasmon resonance (LSPR) based nano ripple gold chip

https://doi.org/10.1016/j.apsusc.2017.03.115Get rights and content

Highlights

  • The nano ripple LSPR chip has monolayer molecule-coating sensitivity and specific selectivity.

  • Gold nano-ripple sensing chip is a low cost, and a label-free method for detecting the antibody-antigen reaction.

  • The plasmonic resonance shift depends upon the concentration of the biomolecules attached on the surface of the nano ripple pattern.

Abstract

We demonstrate that the gold nano-ripple localized surface plasmon resonance (LSPR) chip is a low cost and a label-free method for detecting the presence of an antigen. A uniform stable layer of an antibody was coated on the surface of a nano-ripple gold pattern chip followed by the addition of different concentrations of the antigen. A red shift was observed in the LSPR spectral peak caused by the change in the local refractive index in the vicinity of the nanostructure. The LSPR chip was fabricated using oblique gas cluster ion beam (GCIB) irradiation. The plasmon-resonance intensity of the scattered light was measured by a simple optical spectroscope. The gold nano ripple chip shows monolayer scale sensitivity and high selectivity. The LSPR substrate was used to detect antibody-antigen reaction of rabbit X-DENTT antibody and DENTT blocking peptide (antigen).

Introduction

The need to develop and design accurate and sensitive methods for detection of biological material is of great importance. A sensitive and quantifiable biosensing scheme is essential to detect and analyze disease-associated pathogens obtained from patients or in the environment. LSPR based sensors have the ability for a reliable and sensitive detection that can facilitate appropriate treatments. LSPR nano sensors also have the advantage of simple configuration, high selectivity, and label-free real-time monitoring capabilities [1], [2], [3]. These sensors have applications in many fields including medical diagnostics, biomedical research, food safety, and environmental science [4], [5], [6], [7].

LSPR sensing devices can identify biological phenomena with high specificity and sensitivity at the molecular scale by subsequently transducing the optical signals into quantifiable information [8]. The sensitivity of LSPR wavelength to the local environment [9] can sense the presence of biological molecules such as proteins, antibodies, and other biomolecules adsorbed to the surface of the sensor [10]. The local refractive index change leads to an LSPR spectral shift [11], [12]. Unlike ELISA (enzyme-linked immunosorbent assays) or PCR (polymerase chain reaction), LSPR does not require a labelling or amplifying process. The study of binding kinetics in real time and continuous concentration measurement of the target molecules can be achieved on the sensor [13].

The highly non-reactive nature of gold and its strong affinity to bind organic thiols makes it viable for bio-chemical applications [14]. We introduced a nano ripple gold pattern induced by gas cluster ion beam (GCIB) irradiation [15], [16], [17], [18] with the capability of identifying biomolecular interactions by monitoring LSPR wavelength shifts caused by binding and rebinding of biomolecules attached to the nano ripple gold surface. The LSPR nano ripple chip can detect biomolecules and biomolecular interactions at the mono-layer scale [19], [20]. In this work, we detected an antibody-antigen interaction using adsorbate induced LSPR-wavelength shift from the nano ripple gold surface and its dependence on the antigen concentration.

Section snippets

Materials

Dimethylsulfoxide (DMSO), dithiobissuccinimide propionate (DSP), ethanolamine hydrochloride and Protein A obtained from Sigma-Aldrich Co., USA. Rabbit X-DENTT Antibody and DENTT blocking peptide (Antigen) from Bethyl Laboratories, Inc. Acetone, ethanol and distilled water. Milli-Q water was used to prepare the PBS buffer solution.

Synthesis of gold nano-ripple substrate and SEM image

A plain 100 nm thin-gold film was subjected to collision by clusters of argon gas using a GCIB system. About 3000 atoms per cluster at the fluence of 2 × 1016 clusters/cm2

Results and discussions

In order to determine accurate and optimum LSPR spectral shift in response to a specific antibody-antigen interaction it is important to achieve a stable and uniform layer of the antibody coating on the nanostructure where the antigen binding sites are sterically accessible. Fig. 3a is a schematic diagram describing how the antibody coating was achieved on the substrate keeping antigen binding sites open. The red curve is the LSPR spectrum obtained from the antibody monolayer only. When the

Conclusion

The LSPR based nano-ripple chip fabricated by oblique gas cluster ion beam irradiation can be applied for the detection of antibody-antigen reaction. The induced local refractive index change due to the monolayer functionalization of protein A, the antibody and the antigen on the surface of the gold nano-ripple structure triggered a corresponding LSPR-resonance shift that was easily monitored by a scattering technique (spectroscope). The resonance shift depends upon the concentration of the

Acknowledgment

This work was funded by the state of Texas through the Texas Center for Superconductivity at the University of Houston.

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