Abstract
The unique structural and electrochemical properties of graphene oxide (GO) make it an ideal material for the fabrication of biosensing devices. Therefore, in the present study, graphene oxide nanoparticles modified paper electrodes were used as a low-cost matrix for the development of an amperometric DNA sensor. The graphene oxide was synthesized using the modified hummers method and drop cast on a screen-printed paper electrode (SPPE) to enhance its electrochemical properties. Further, the GO/SPPE electrode was modified with a 5′NH2 labeled ssDNA probe specific to the htrA gene of Orientia tsutsugamushi using carbodiimide cross-linking chemistry. The synthesized GO was characterized using UV-Vis, FTIR, and XRD. The layer-by-layer modification of the paper electrode was monitored via FE-SEM, cyclic voltammetry, and electrochemical impedance spectroscopy (EIS). The sensor response after hybridization with single-stranded genomic DNA (ssGDNA) of O. tsutsugamushi was recorded using differential pulse voltammetry (DPV). Methylene blue (1 mM in PBS buffer, pH 7.2) was used as a hybridization indicator and [Fe(CN)6]−3/−4 (2.5 mM in PBS buffer, pH 7.2) as a redox probe during electrochemical measurements. The developed DNA sensor shows excellent sensitivity (1228.4 µA/cm2/ng) and LOD (20 pg/µL) for detection of O. tsutsugamushi GDNA using differential pulse voltammetry (DPV).
Highlights
Scrub typhus, one of the most neglected and re-emerging infectious diseases of the tsutsugamushi triangle, is caused by a Gram-negative bacterium known as Orientia tsutsugamushi [1,2]
These methods are sensitive and specific for the detection of antibody titer but only up to a certain detectable level. These are not able to detect the infection at early stages [1,3]. The molecular assay, such as room temperature (RT)-PCR, is sensitive and specific but shows false-negative results owing to the diversified genetic makeup of O. tsutsugamushi and lower recovery of its genomic DNA (GDNA) from the patient’s blood samples [3]
The method was based on electrochemical detection using a screen-printed paper electrode modified with graphene oxide and ssDNA probe specific to the htrA gene of O. tsutsugamushi
Summary
One of the most neglected and re-emerging infectious diseases of the tsutsugamushi triangle, is caused by a Gram-negative bacterium known as Orientia tsutsugamushi [1,2]. Low-cost disposable materials, such as paper-based electrodes, have gained considerable attention for the construction of electrochemical sensors due to their ability to work with low sample volume, low cost, and higher flexibility [5,6,7,8,9,10,11] These electrodes show excellent sensitivity, LOD, and stability in the detection of the targeted analyte using different samples [12,13,14,15,16]. The method was based on electrochemical detection using a screen-printed paper electrode modified with graphene oxide and ssDNA probe specific to the htrA gene of O. tsutsugamushi. Schematic representation of SPPE/GO/ssDNAprobe /BSA fabrication process with assay protocol for detection of O. tsutsugamushi
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