High-Performance Graphene-Modified Sensing Chip for SARS-CoV-2 Detection

Summary

The present protocol describes the fabrication of low-cost biosensing prototypes based on useful nanosystems for accurately detecting viral proteins (at the Fg level). Such a tiny sensor platform allows for point-of-care applications that can be integrated with the Internet of Medical Things (IoMT) to meet telemedicine objectives.

Abstract

This sensing prototype model involves the development of a reusable, twofold graphene oxide (GrO)-glazed double inter-digitated capacitive (DIDC) detecting chip for detecting severe acute respiratory syndrome coronavirus 2 virus (SARS-CoV-2) specifically and rapidly. The fabricated DIDC comprises a Ti/Pt-containing glass substrate glazed with graphene oxide (GrO), which is further chemically modified with EDC-NHS to immobilize antibodies (Abs) hostile to SARS-CoV-2 based on the spike (S1) protein of the virus. The results of insightful investigations showed that GrO gave an ideal engineered surface for Ab immobilization and enhanced the capacitance to allow higher sensitivity and low sensing limits. These tunable elements helped accomplish a wide sensing range (1.0 mg/mL to 1.0 fg/mL), a minimum sensing limit of 1 fg/mL, high responsiveness and good linearity of 18.56 nF/g, and a fast reaction time of 3 s. Besides, in terms of developing financially viable point-of-care (POC) testing frameworks, the reusability of the GrO-DIDC biochip in this study is good. Significantly, the biochip is specific against blood-borne antigens and is stable for up to 10 days at 5 °C. Due to its compactness, this scaled-down biosensor has the potential for POC diagnostics of COVID-19 infection. This system can also detect other severe viral diseases, although an approval step utilizing other virus examples is under development.

Introduction

A viral pandemic caused by a new beta coronavirus¹ (i.e., 2019-nCoV), which was later named as severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)² (hereafter predominantly referred to as the virus), involving a pneumonic cluster and severe acute respiratory distress, emerged in the Wuhan city, China, at the end of 2019³. Owing to its fast worldwide human-to-human transmission, high infection rate, high mortality rate, and serious life-threatening adverse effects⁴, during the pandemic, virology research⁵ evolved quickly to identify....

Protocol

1. Cleaning of the DIDC sensing chip

1. At the beginning of the experiment, clean the DIDC chip surface²⁶ with piranha solution (H₂SO₄:H₂O₂in a 3:1 ratio), and place it on the hot plate at 80 °C for 15 min. Next, rinse the sensor surface with distilled water drop by drop using a pipette to remove the cleaning reagents completely. To ensure the complete removal of the reagent, rinse the surface with four to five drops of ethyl alcohol.
   NOTE: The DIDC chip was fabricated following a previously published report²⁶.
2. Then, dry the ....

Results

Here, a protocol is presented for sensing the S1 protein of the SARS-CoV-2 virus using a graphene oxide-glazed double inter-digitated capacitive (DIDC) sensing chip. Figure 1 shows a schematic representation (fabrication with the circuit layout) of the extremely sensitive and recyclable graphene oxide-modified double interdigitated capacitive (DIDC) sensing chip. The detailed stepwise fabrication process is shown in Figure 2. Figure 3

Discussion

For fashioning a productive DIDC chip-based biosensor, the charge distribution, conductivity, and dielectric constant of the DIDC are extremely important. Significantly, the improvements in these detection boundaries relate to the capacitive reactance of the DIDC^18,26,27. In this study, a capacitance immunosensor was fabricated that is hostile to the virus Abs and functionalized by EDC-NHS coupling on the graphene oxide-DIDC-bas.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
Amyloid β1-42 Protein	Merck (Sigma-Aldrich)	107761-42-2
anti-SARS-CoV-2 Spike (S1) monoclonal IgG antibody	SinoBiological	40150-R007
EDC [N-(3-dimethylaminopropyl)-N′-ethylcarbodiimide hydrochloride]	Thermo Fisher Scientific	A35391
Ethyl alcohol (C2H5OH)	Sigma-Aldrich
Hydrogen peroxide (H2O2)
Kapton tape			polyimide tape
NHS (NHydroxysuccinimide, 98+%; C4H5NO3)	Thermo Fisher Scientific	A39269
PBS
Prostate-specific antigen	Sigma-Aldrich	P3338-25UG
SARS-CoV-2 Spike S1-His recombinant protein	SinoBiological	40591-V08H
Single layer Graphene Oxide	Graphene Supermarket
Spin Coater	High Precision Spin Coater (Spin Coating System)		ACE-200
Sulfuric acid (H2SO4)