ABSTRACT
Diabetes is a chronic disease, which is the seventh leading cause of death worldwide. The increased risk to the health of diabetic patients, with comorbidities in harsh situations like COVID-19 pandemics, necessitates real-time monitoring of blood glucose. Monitoring of blood glucose is invasive, hence, sweat glucose monitoring can be an alternative approach to address the invasive issue in blood glucose monitoring. This work reports a facile, low-cost, high-performance nonenzymatic copper (Cu) native oxide (CuNOx)-based electrochemical sensor for sweat glucose sensing. We utilized a very thin Cu native oxide of ~10 nm on Cu thin film for the sensing because of the excellent catalytic oxidation behavior of cuprous oxide (Cu2O) to glucose. The anodic sweep of cyclic voltammetry of glucose showed that the hydroxyl ions from sodium hydroxide convert the electrode surface into different oxides [Cu(I), Cu(II) Cu(III)], which electro-oxidize glucose to gluconolactone, then eventually to gluconic acid resulting in oxidation current. The CuNOx sensors exhibited a sensitivity of 603.42 μA mM−1 cm−2, a linear range beyond the desired limit of 7.00 mM with excellent linearity, and a low limit of detection of 94.21 μM. Excellent repeatability and stability (stable >1 year) with relative standard deviation (RSD) of 2.67%, and 2.70%, respectively were achieved for 1 mM glucose. The selectivity with common interferants of glucose in human sweat and blood showed an RSD of 3.56%. We believe the electrocatalytic efficacy of the CuNOx sensors for glucose sensing can open a new prospect in the fabrication of wearable sweat glucose sensors.
ABSTRACT
The COVID-19 pandemic has devastated the world, despite all efforts in infection control and treatment/vaccine development. Hospitals are currently overcrowded, with health statuses of patients often being hard to gauge. Therefore, methods for determining infection severity need to be developed so that high-risk patients can be prioritized, resources can be efficiently distributed, and fatalities can be prevented. Electrochemical prognostic biosensing of various biomarkers may hold promise in solving these problems as they are low-cost and provide timely results. Therefore, we have reviewed the literature and extracted the most promising biomarkers along with their most favourable electrochemical sensors. The biomarkers discussed in this paper are C-reactive protein (CRP), interleukins (ILs), tumour necrosis factor alpha (TNFα), interferons (IFNs), glutamate, breath pH, lymphocytes, platelets, neutrophils and D-dimer. Metabolic syndrome is also discussed as comorbidity for COVID-19 patients, as it increases infection severity and raises chances of becoming infected. Cannabinoids, especially cannabidiol (CBD), are discussed as a potential adjunct therapy for COVID-19 as their medicinal properties may be desirable in minimizing the neurodegenerative or severe inflammatory damage caused by severe COVID-19 infection. Currently, hospitals are struggling to provide adequate care; thus, point-of-care electrochemical sensor development needs to be prioritized to provide an approximate prognosis for hospital patients. During and following the immediate aftermath of the pandemic, electrochemical sensors can also be integrated into wearable and portable devices to help patients monitor recovery while returning to their daily lives. Beyond the COVID-19 pandemic, these sensors will also prove useful for monitoring inflammation-based diseases such as cancer and cardiovascular disease.