Design and fabrication of Gr/Ag-coated tilted grating sensor for ultra-sensitive detection of DNA hybridization

Abstract

A graphene sensitized biosensor based on 6° tilted fiber Bragg grating (TFBG) was proposed. The introduction of the graphene coating boosted the sensitivity and stability of the Ag/TFBG sensor, and improved the probe loading and molecular capture of the sensitized layer. A quantitative analytical model was proposed to calculate the hybridization efficiency and maximum sensor response of DNA single base mismatch. The results showed that the kinetic affinity response of the Gr/Ag/TFBG sensor was stably demonstrated with a dissociation constant (kd=9.392 ± 0.178·10−3 min−1) and the detection limit of DNA was as low as 3 pM. This indicates that the sensor has the ability to distinguish single base mutations quantitatively in real time. The surface modification, probe binding and DNA hybridization were characterized based on atomic force microscopy (AFM) and Raman detection spectrum detection system. A 3D diversity analysis model for TFBG sensors was innovatively proposed based on COMSOL. The multi-mode coupling and polarization response analysis of the inner core, the electric field distribution and polarization transmission mode of the sensitized layer, and the polarization gain brought by graphene are systematically described. Excellent bioanalytical capabilities combined with well-established analytical methods make prepared sensor promising for high-throughput screening of genetic variants and disease markers.