Electrochemical detection of ACE2 as a biomarker for diagnosis of COVID-19 and potential male infertility.

Knowing how heavily the body is burdened by SARS-CoV-2 infection is all important to avoid tragic outcomes. This demands fast and convenient assays with minimum requirement for instruments and reagents. Therefore, a short synthetic peptide is developed to perform direct serum assay, using portable hand-held potentiostat, in a reagent-less manner. The target is angiotensin converting enzyme 2 (ACE2), a protein secreted by the body into the blood to restrict viral invasion. Specifically, under electrochemical potential scanning, the peptide can covalently capture ACE2 from the serum, and then form a covalent gel-like 2D protein network with the serum proteins, in an ACE2-specific fashion. This formation of a covalent biosensing complex enables sensitive detection in serum samples of SARS-CoV-2 infected patients. The detected serum level of ACE2 can not only serve as an index of viral load, but may also hint at the associated risk of potential male infertility. These results may point to field application of this simple design in the clinical practice in treating COVID-19 in the near future.

Minimalist Design for a Hand-Held SARS-Cov-2 Sensor: Peptide-Induced Covalent Assembly of Hydrogel Enabling Facile Fiber-Optic Detection of a Virus Marker Protein.

The rampaging COVID-19 needs bioassaying methods of low cost and high robustness for those living in the poorly developed regions. Here, we propose such a method that does not need expensive and complicated equipment. Only a set of hand-held small devices is sufficient. A section along an optic fiber cable is stripped, so that laser light travelling through it will leak outside, while biosensing process taken place on this stripped section can form a new cladding layer of hydrogel, restoring the laser output of the fiber. A short peptide probe immobilized on the stripped section of the fiber can covalently capture a biomarker protein of SARS-Cov-2 from the serum sample. Through the cross-linking of the target protein with the interfering proteins in the serum sample, a hydrogel is covalently immobilized around the stripped section, highly resistant to detergent rinsing that is indispensable for removing nonspecific interference from the clinical sample. Using this "covalent biosensing" strategy, only one peptide probe is sufficient to simultaneously achieve ultrahigh affinity toward the biomarker protein of SARS-Cov-2 and effective signal amplification.

Electrochemical Resonance of Molecular Motion Enabling Label-, Antibody-, and Enzyme-Free Detection of SARS-CoV-2.

In this work, we developed a method to detect two viral marker proteins, the main protease and the spike protein (S protein), of SARS-CoV-2, as well as a host marker, chemokine receptor 5 (CCR5), which is associated with the risk of developing the severe acute respiratory syndrome. This assay can be completed in two steps in a label-free fashion, yielding a "signal-on" signal readout, which usually cannot be attained by electrochemical label-free detection using no labels or markers to tag the target protein. The proposed assay also utilizes no antibodies or enzyme-based reagents. The method achieves this performance by moderating the frequency of electrochemical potential scanning such that the scanning rate keeps pace with, or "resonances" with, the molecular motion of the probe molecule. This method has been successfully applied to detect the three target proteins in serum samples collected from patients infected with SARS-CoV-2, and the results indicate a strong correlation with the risk of deteriorating into severe acute conditions after virus infection. Soon, the clinical application of this method may provide a low-cost but effective method for virus surveillance in the general public.