Fluorescent Apta-Nanobiosensors for Fast and Sensitive Detection of Digoxin in Biological Fluids Using Rgqds: Comparison of Two Approaches for Immobilization of Aptamer Publisher



Elmizadeh H¹ ; Faridbod F² ; Soleimani M¹ ; Ganjali MR^{2, 3} ; Bardajee GR⁴
Source: Sensors and Actuators# B: Chemical Published:2020

Abstract

Two approaches were utilized and compared for designing a novel ultrasensitive fluorescent apta-nanobiosensor for fast and sensitive determination of digoxin (DX) in biological fluids. The nanobiosensors were fabricated using reduced graphene quantum dots (rGQDs) as an optical probe and DX aptamer as a sensing material. In the first approach, a label-free aptamer was directly interacted with rGQDs, caused an enhancement of the fluorescence intensity of rGQDs. By addition of the target molecule (DX) and formation of the aptamer-DX complex, the fluorescence intensity was decreased. The fluorescent quenching had a linear relation with the concentration of DX with limit of detection down to 29.87 ± 1.01 × 10−12 mol L−1. In the second approach, to improve the reproducibility and sensitivity of the biosensor, a labeled aptamer with amine groups was used. Through a two-steps process, DX was detected more accurately. Fluorescence intensity of rGQDs functionalized with aptamer was first turn-off using oxidized carbon nanotubes (CNTs) through a fluorescence resonance energy transfer (FRET) mechanism. Next, by addition of the target molecule (DX), and its interaction with aptamer, inhibited the connection between CNTs and rGQDs-aptamer, hence, fluorescence of rGQDs were recovered and turn-on. The second approach provided a simple, fast, inexpensive, reproducibility and ultrasensitive methods for determination of DX with ultra-low detection limits of 7.95 ± 0.22 × 10−12 mol L−1. Both designed luminescent apta-nanobiosensors were well used for the quantification of DX in human serum and urine with satisfactory analytical results. © 2019 Elsevier B.V.