A double helix-shaped optical fiber sensor for non-endoscopic diagnosis of gastrin-17

Non-endoscopic tools for the diagnostic evaluation of patients should be promoted in the field of biomedical assay and the need for highly sensitive, efficient, low-cost, and user-friendly sensors must be considered. Optical fibers are widely used in sensors because their properties meet the physical requirements for biomedical detection. The spectrum responses of the sensor create changes in refractive index, wavelength shifts, and transmission loss. This study presents a double helix DNA-shaped optical fiber sensor for biosensors. The sensing principle of the DNA-shaped sensor is based on the whispering gallery mode (WGM) formed by the interference in the fiber's bending region. The refractive index interference changes corresponding to the core and cladding layers, which create shifts in the spectrum affected by the radius of the bend. A self-assembled sensor layer formed with nanoparticles was coated onto the DNA-shaped sensor in a sandwich structure. The wavelength shifts in spectral response are traced by the concentrations of gastrin-17 at 0.1, 1, 10, and 50 μg ml^-1. The sensing layer was formed from a layer-by-layer assembly of gold nanoparticles to improve the performance of the surface plasmon resonance (SPR).