Colorimetric Detection of the SARS-CoV-2 Virus (COVID-19) in Artificial Saliva Using Polydiacetylene Paper Strips

Abstract

The spread and resurgence of the SARS-CoV-2 virus (COVID-19 disease) threatens human health and social relations. Prevention of COVID-19 disease partly relies on fabricating low-cost, point-of-care (POC) sensing technology that can rapidly and selectively detect the SARS-CoV-2 virus. We report a colorimetric, paper-based polydiacetylene (PDA) biosensor, designed to detect SARS-CoV-2 spike protein in artificial saliva. Analytical characterizations of the PDA sensor using NMR and FT-IR spectroscopy showed the correct structural elucidation of PCDA-NHS conjugation. The PDA sensor platform containing the N-Hydroxysuccinimide ester of 10, 12-pentacosadiynoic acid (PCDA-NHS) was divided into three experimental PCDA-NHS concentration groups of 10%, 20%, and 30% to optimize the performance of the sensor. The optimal PCDA-NHS molar concentration was determined to be 10%. The PDA sensor works by a color change from blue to red as its colorimetric output when the immobilized antibody binds to the SARS-CoV-2 spike protein in saliva samples. Our results showed that the PDA sensing platform was able to rapidly and qualitatively detect the SARS-CoV-2 spike protein within the concentration range of 1 to 100 ng/mL after four hours of incubation. Further investigation of pH and temperature showed minimal influence on the PDA sensor for the detection of COVID-19 disease. After exposure to the SARS-CoV-2 spike protein, smartphone images of the PDA sensor were used to assess the sensor output by using the red chromatic shift (RCS) of the signal response. These results indicate the potential and practical use of this PDA sensor design for the rapid, colorimetric detection of COVID-19 disease in developing countries with limited access to medical testing.

Smartphone-based point-of-care testing of the SARS-CoV-2: A systematic review

“… The sample exposed to a mini camera able to take snapshots of the color change in real time during LAMP amplification. [45] Colorimetric Saliva Not reported SARS-CoV-2 spike protein 1 ng/mL Not reported Not reported Not reported smartphone images were used to assess the sensor output by using the red chromatic shift (RCS) of the signal response [46] Colorimetric Nasopharyngeal swab Lysis and target RNA enrichment, Orf1a gene and the N gene 5 copies per µL of the sample NR less than one hour Redmi 7 and iPhone freely available “camera color picker” smartphone apps [47] Colorimetric Blood freeze-dried and mixed for 40 min at 37°C. The magnets were used to capture the complexes catalyzed for 10 min at 37°C RNA virus 10 pg/mL 75.7% 1 hour NR telemedicine [48] Colorimetric Saliva optimized chemical treatment and heat inactivation SARS-CoV-2 nucleic acid ∼100 copies 98% <1 hour NR mobile application for detection and quantification of lateral-flow strips.…”

“…Another study by Prainito et al. utilized smartphone photos to evaluate a plasmonic biosensor's signal response following exposure to the spike protein of the SARS-CoV-2 virus [46] . Once the images captured by the smartphone camera, a smartphone app was employed to diagnose the condition by determining the level of SARS-CoV-2.…”

Photoelectrochemical biosensing platform for the SARS‐CoV‐2 spike and nucleocapsid proteins

“…Table 1 [46][47][48][49][50][51][52][53][54][55][56][57][58] shows different techniques and analytical parameters reported in the literature for the detection of SARS-CoV-2. As can be seen, the proposed immunosensors reported in this manuscript presents a sensitivity comparable to or better than the analytical sensitivity reported in some works.…”

Dual Nanofriction Force Microscopy/Fluorescence Microscopy Imaging Reveals the Enhanced Force Sensitivity of Polydiacetylene by pH and NaCl

“…Polydiacetylene (PDA) is a smart responsive material that changes its color from blue to red and emits fluorescent upon exposure to chemical , and physical stimuli . It has particularly garnered attention in sensing fields such as the detection of ions, mechanical force, , temperature, , volatile organic compounds, and biomolecules. − Its mechanochromic principle originates from the twist of the backbone that shortens the conjugation length, which is governed by a delicate balance between the headgroup–headgroup interactions, the interalkyl chain interactions, and entropy. Some of them (e.g., the hydrogen bonding in the headgroup, the van der Waals attraction forces between the alkyl chains) favor planarization, whereas others (e.g., the electrostatic repulsion in the headgroups, the entropy) encourage the deplanarization or the twist.…”