Highly Sensitive Sars-Cov-2 Detection Using Au-Functionalized Laser-Induced Graphene Sensors
Authors: Brustoloni Caroline Ji-Mei , Khamsi Pouya Soltan , Kammarchedu Vinay , Ebrahimi Aida 
Published: December 2024

Abstract

The 2019 coronavirus (COVID-19) pandemic has led to a drastic loss of human life and presented unprecedented challenges to global health, society, and the economy. Developing highly sensitive diagnostics for early detection of the infection is crucial in controlling the disease’s spread. Conventional polymerase chain reaction tests, while accurate, are relatively slow, expensive, and require trained personnel, causing strain on healthcare systems as they struggled to meet testing demands1. Electrochemical sensors offer advantages over traditional diagnostic methods including lower production cost, ease of use, real time analysis, and high sensitivity. Recently, laser-induced graphene (LIG) has gained significant attention in electrochemical sensing for its high surface area and excellent electron transfer properties. Various graphene modification methods have been used in developing electrochemical sensors, including Au-NP functionalization, choice of cross-linkers, and incubation parameters such as humidity, temperature, and duration; however, a systematic, concurrent comparison of these functionalization parameters is missing.
In this work, through a comprehensive investigation of various functionalization steps, we developed electrochemical sensors based on Au-functionalized laser induced graphene (LIG) for detection of SARS-CoV-2 with an outstanding limit of detection (LOD) of 1.2 ag/mL. To optimize the sensors, we explored the functionalization of LIG with Au-NPs via direct laser processing. The porous structure of LIG increases the surface area available for electrochemical reactions and protein immobilization, enhancing its effectiveness for sensing applications2. We showed that functionalization of the working electrode LIG with Au-NPs improves the electrochemically active surface area by ~4.5-fold compared to the geometric area. We also investigated the impact of different crosslinkers and showed that PBA/Sulfo-NHS/EDC cross-linker improves the sensitivity and LOD significantly compared to PBASE. Additionally, we studied the effect of antigen mixing, showing that sensitivity and LOD improve by more than 1.6-fold and 5.5-fold using pipette mixing compared to static mixing. The incubation condition is also optimized. Moreover, the sensors exhibit excellent selectivity against other viruses, including HCoV-229E, HCoV-OC43, HCoV-NL63, and influenza H5N1. To show the diagnostic ability for analysis of real samples, the sensor performance in spiked saliva is also demonstrated.
The insights gained from this study on graphene modification for SARS-CoV-2 detection may help optimize the fabrication of other graphene-based electrochemical sensors for detecting a variety of bioanalytes based on immobilization of biorecognition molecules.

References

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J. Lin et al., “Laser-induced porous graphene films from commercial polymers,” Nature Communications, vol. 5, no. 1, p. 5714,2014