A fully integrated wearable impedance cytometer with an online smartphone readout has been demonstrated a little while back26. Recently, a handheld portable platform using disposable nanopore strips has also been presented for the detection of HIV antibody levels in saliva27. In another paper28, the authors presented a dielectrophoretic-impedance based method for the detection and analysis of proteins, specifically Bovine Serum Albumin (BSA). Authors in another article29 showcase an electrochemical impedance-based sensor employing graphene-carbon nanotubes composite deposited on a glassy carbon electrode to detect the protein antigen. A universal antibody-modified nanocrystalline boron-doped diamond biosensor for direct detection of protein and viral particles at very low concentrations was discussed30. Researchers described a new paper based electrochemical impedance biosensor for label-free detection and quantification of human interferon-gamma (IFN-γ), a biomarker which plays an important role in tuberculosis susceptibility31. Another microfluidic device, utilizing bead-based capture chamber technology, for the quantification of IL-6 in human serum samples for sepsis stratification was presented32. Furthermore, in other studies33,34, researchers present electrochemical biosensors for the detection of IgG anti-Trypanosoma cruzi antibodies and IgG antibodies to Helicobacter pylori in human serum samples respectively. Table 1 presents a comparison of systems that detect proteins electrically. Although significant leaps in the prototyping and development of microfluidic electrochemical biosensors have been made in the laboratory and academic environment within the last decade, the translation of most of these devices to a Point-of-Care setting has been limited by practical constraints and challenges such as portability, cost, integration, and regulatory affairs35. Additionally, the use of electrochemical biosensors for complex physiological samples such as blood, serum, and saliva is challenging since high salt concentrations in these samples reduce the double layer thickness and result in charge screening. Therefore, an electrical system needs to be highly sensitive, portable, and must have the ability to work with biological specimens with high salt concentrations for potential use in a POC setting.
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