Full Length ArticleA new technique to detect antibody-antigen reaction (biological interactions) on a localized surface plasmon resonance (LSPR) based nano ripple gold chip
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.
References (24)
LSPR-based nanobiosensors
Nano Today
(2009)Biosensing by optical waveguide spectroscopy based on localized surface plasmon resonance of gold nanoparticles used as a probe or as a label
J. Colloid Interface Sci.
(2009)- et al.
Localized surface plasmon resonance: nanostructures, bioassays and biosensing-a review
Anal. Chim. Acta
(2011) Localized surface plasmon resonance based optical biosensor using surface modified nanoparticle layer for label-free monitoring of antigen–antibody reaction
Sci. Technol. Adv. Mater.
(2005)Nano structure formation by gas cluster ion beam irradiations at oblique incidence
Nucl. Instrum. Methods B
(2005)Cluster ion beam assisted fabrication of metallic nanostructures for plasmonic applications
Nucl. Instrum. Methods B
(2016)- et al.
Gold nano ripple structure with potential for bio molecular sensing applications
Sens. Bio-sens. Res.
(2016) Localized surface plasmon resonance (LSPR) of polyelectrolyte-functionalized gold-nanoparticles for bio-sensing
Colloids Surf. A: Physicochem. Eng. Aspects
(2009)Oriented immobilization of biologically active proteins as a tool for revealing protein interactions and function
J. Chromatogr. B: Biomed. Sci. Appl.
(1999)A bilirubin biosensor based on multilayer network enzyme electrode
Biosens. Bioelectron.
(1995)