A capacitive laser-induced graphene based aptasensor for SARS-CoV-2 detection in human saliva

Abstract

SARS-CoV-2 virus induced CoVID-19 pandemic has accelerated the development of diagnostic tools. Devices integrated with electrochemical biosensors may be an interesting alternative to respond to the high demand for testing, particularly in contexts where access to standard detection technologies is lacking. Aptamers as recognition elements are useful due to their stability, specificity, and sensitivity to binding target molecules. We have developed a non-invasive electrochemical aptamer-based biosensor targeting SARS-CoV-2 in human saliva. The aptamer is expected to detect the Spike protein of SARS-CoV-2 wildtype and its variants. Laser-induced graphene (LIG) electrodes coated with platinum nanoparticles were biofunctionalized with a biotin-tagged aptamer. Electrochemical Impedance Spectroscopy (EIS) for BA.1 sensing was conducted in sodium chloride/sodium bicarbonate solution supplemented with pooled saliva. To estimate sensing performance, the aptasensor was tested with contrived samples of UV-attenuated virions from 10 to 10,000 copies/ml. Selectivity was assessed by exposing the aptasensor to non-targeted viruses (hCoV-OC43, Influenza A, and RSV-A). EIS data outputs were further used to select a suitable response variable and cutoff frequency. Capacitance increases in response to the gradual loading of the attenuated BA.1. The aptasensor was sensitive and specific for BA.1 at a lower viral load (10–100 copies/ml) and was capable of discriminating between negative and positive contrived samples (with strain specificity against other viruses: OC43, Influenza A, and RSV-A). The aptasensor detected SARS-CoV-2 with an estimated LOD of 1790 copies/ml in contrived samples. In human clinical samples, the aptasensor presents an accuracy of 72%, with 75% of positive percent of agreement and 67% of negative percent of agreement. Our results show that the aptasensor is a promising candidate to detect SARS-CoV-2 during early stages of infection when virion concentrations are low, which may be useful for preventing the asymptomatic spread of CoVID-19.

Role of aptamer technology in extracellular vesicle biology and therapeutic applications

“…For example, the LOD for SARS-CoV-2 detection using an electrochemical aptasensor is <1100 copies per mL, 149 while for a capacitive laser-induced graphene-based aptasensor, it stands at 1790 copies per mL. 150 These LODs translate to a detection capability that is 2 orders of magnitude beyond the acceptable diagnostic sensitivity for SARS-Cov-2 (1.0 × 10 6 genome copies per mL) according to the World Health Organization. 151 As for protein detection, an on-chip integrated graphene aptasensor achieves an LOD of 160 aM for COVID-19 neutralizing antibodies in serum, 152 which is 5 orders of magnitude lower than the minimum target concentration (30 pM) in patients.…”

Recent advances in graphene-based electroanalytical devices for healthcare applications

“… 192 Moreira et al demonstrated an aptasensor based on EIS. 193 The proposed aptasensor for the detection of SARS-CoV-2 in human saliva was fabricated using LIG. A comprehensive analysis of EIS signals identified the optimal response along with suitable cutoff frequencies.…”

A dip-and-read impedimetric electrochemical sensor for orthophosphate monitoring

“…LIG can be functionalized with the material of interest (recognition element), where changes in the electrochemical response of LIG occur due to the chemical interaction between the recognition element and target analyte in solution. In the last decade since the discovery of LIG, this material has been used for targeting a wide variety of sensors, for example: bacteria [22], viruses [23], sugars [20], and ions [24]. This material is simple to fabricate, and numerous portable devices have been developed using custom form factors that meet sampling needs.…”