Shourya Kumar and Limei Tian, PhD

Introduction: Coronaviruses are enveloped RNA viruses in humans and animals that can cause acute and chronic diseases¹. In patients with a weak immune system or other (unknown) pre-existing conditions, an uncontrolled inflammatory response linked to a cytokine storm has been associated with severe pulmonary inflammation being the leading cause of death². In fact, studies show increased levels of cytokine storms correlate with more severe disease progression. Specifically, IL-6, IL-8, and IL-10 are shown to be predictors for quicker diagnosis of severe COVID-19 disease^3-4. Various point-of-care biosensors targeting cytokines have shown therapeutic value in determining the severity of COVID-19 disease. Methods: One biosensor utilizes an aptameric dual graphene-TWEEN 80 field effect transistor (DGTFET) to enable on-site, wireless detection of cytokines (IFN-γ, TNF-α, and IL-6) from several body fluids⁵. Another biosensor made from a cellulose-nanoparticle combination, utilizes conjugated gold nanoparticles to anti IL-6 antibodies, fixed to modified filter paper/wax paper. A subsequent 10uL sample is added to the first portion of the strip, dried with high heat (hairdryer), and then washed with a wash-buffer. The resulting colorimetric signal is then imaged with a smartphone app⁶. Another biosensor integrates machine learning with a microfluidic, nanoplasmonic digital immunoassay to profile cytokine levels of COVID-19 patients. The one-step immunoassay works by utilizing anti-cytokine capture antibody and antigen nanocubes conjugated with paired detection antibodies as signal transducers. The resulting sandwich complex is then imaged with a dark field microscope and analyzed with an on-board machine learning system⁷. Results: The biosensor developed by Hao, et al. demonstrates the capabilities of their DGTFET device in detecting cytokines IFN-γ, TNF-α, and IL-6 in biofluids including serum, saliva, urine and sweat, with respective limits of detection (LODs) of 476 × 10−15, 611 × 10−15, and 608 × 10−15 M⁵. The biosensor developed by Adrover-Jaume, et al. achieved a LOD of 17 pg mL-1 in blood⁶. Finally, the biosensor developed by Gao, et al. allows for simultaneous detection of six cytokines with LODs of LODs of 0.91 pg mL^–1 (IL-1β), 0.47 pg mL^–1 (IL-2), 0.46 pg mL^–1 (IL-6), 1.36 pg mL^–1 (IL-10), 0.71 pg mL^–1 (TNF-α), and 1.08 pg mL^–1 (IFN-γ)⁷.  Conclusions: Together, these studies demonstrate the significant advances that have made in development of biomarkers targeting cytokines, allowing for earlier detection of potentially severe COVID-19 disease progression, ultimately improving patient outcomes.

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