Abstract
This article illustrates a design and finite difference time domain (FDTD) method based on analysis of fiber optic surface plasmon resonance (SPR) biosensor for biomedical application especially for DNA-DNA hybridization. The fiber cladding at the middle portion is constructed with the proposed hybrid of gold (Au), graphene, and a sensing medium. This sensor can be recognized adsorption of DNA biomolecules onto sensing medium of PBS saline using attenuated total reflection (ATR) technique. The refractive index (RI) is varied owing to the adsorption of different concentration of biomolecules. Result states that the sensitivity with a monolayer of graphene will be improved up to 40% than bare graphene layer. Owing to increased adsorption capability of DNA molecules on graphene, sensitivity increases compared to the conventional gold thin film SPR biosensor. Numerical analysis shows that the variation of the SPR angle for mismatched DNA strands is quite negligible, whereas that for complementary DNA strands is considerable, which is essential for proper detection of DNA hybridization. Finally, the effect of Electric field distribution on inserting graphene layer is analyzed incorporating the FDTD technique by using Lumerical FDTD solution software.
Highlights
surface plasmon resonance (SPR) spectroscopy is a label-free detection method which has become an extensively applied during the last three decades and accepted bio-analytical technique for real-time detection and monitoring of biomolecular binding events [1]
As a result of the optical Kerr effect [11], notable variation occurs in the refractive index if the operating frequency is increased as the beam intensity is on the order of 1 GW/cm2.The theoretical results show that 633 nm is such a wavelength at which the overall sensitivity of the sensor is enhanced with the minimal possible Kerr effect [11]
The surface plasmon wave (SPW) propagation constant, kspw is described in Equation (2), where nAu is the refractive index (RI) of the gold and ng is the RI of the graphene [1], [9]: k SPW
Summary
SPR spectroscopy is a label-free detection method which has become an extensively applied during the last three decades and accepted bio-analytical technique for real-time detection and monitoring of biomolecular binding events [1]. As a fundamental part of fiber optic SPR biosensor, a fiber is coated with a thin metallic film (Au, Ag, or Al) to distinct the sensing medium and the dielectric [6,7,8]. Graphene embedded on gold film fiber optic sensor is proposed, where phosphate buffer saline (PBS) solution as sensing dielectric medium that is used to provide better adsorption of single strand target or probe DNA (ss-DNA) biomolecules. This sensor is allowed to recognize hybridization event in proper orientation of adenine (A), thymine (T), guanine (G) and cytosine (C) according to Fig. 1 in ref. This enhanced sensitivity is discussed in terms of electric field distribution near the graphene interface
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